Piping_Materials_Elbows and Bends_Reducers_PE & ROTO Lined Carbon Steel Piping

Piping Elbows and Bends are very important pipe fitting which are used very frequently for changing direction in
piping system. Piping Elbow and Piping bend are not the same, even though sometimes these two terms are
interchangeably used. A BEND is simply a generic term in piping for an “offset” – a change in direction of the
piping. It signifies that there is a “bend” i.e., a change in direction of the piping (usually for some specific reason) –
but it lacks specific, engineering definition as to direction and degree. Bends are usually made by using a bending
machine (hot bending and cold bending) on site and suited for a specific need. Uses of bends are economic as it
reduces number of expensive fittings.
An ELBOW, on the other hand, is a specific, standard, engineered bend pre-fabricated as a spool piece (based on
ASME B 16.9) and designed to be screwed, flanged, or welded to the piping it is associated with. An elbow can be
45 degree or 90 degree. There can also be custom-designed elbows, although most are categorized as either “short
radius” or long radius”.
In short “All bends are elbows but all elbows are not bends”
Whenever the term elbow is used, it must also carry the qualifiers of type (45 or 90 degree) and radius (short or
long) – besides the nominal size.
Elbows can change direction to any angle as per requirement. An elbow angle can be defined as the angle by which
the flow direction deviates from its original flowing direction (See Fig.1 below). Even though an elbow angle can be
anything greater than 0 but less or equal to 90° but still a change in direction greater than 90° at a single point is not
desirable. Normally, a 45° and a 90° elbow combinedly used while making piping layouts for such situations.

Fig.1 A typical elbow with elbow angle (phi)
Elbow angle can be easily calculated using simple geometrical technique of mathematics.
Refer to Fig.2. Pipe direction is changing at point A with the help of an elbow and again the direction is changing at
the point G using another elbow.

Fig.2 Example figure for elbow angle calculation
In order to find out the elbow angle at A, it is necessary to consider a plane which contains the arms of the elbow. If
there had been no change in direction at point A, the pipe would have moved along line AD but pipe is moving along
line AG. Plane AFGD contains lines AD and AG and elbow angle (phi) is marked which denotes the angle by which
the flow is deviating from its original direction.
Considering right angle triangle AGD, tan (phi) = √(x2 + z2)/y
Similarly elbow angle at G is given by: tan (phi1) =√ (y2 +z2)/x

Page 1 of 52

Elbow Radius:
Elbows or bends are available in various radii for a smooth change in direction which are expressed in terms of pipe
nominal size expressed in inches. Elbows or bends are available in three radii,
a. Long radius elbows (Radius = 1.5D): used most frequently where there is a need to keep the frictional fluid
pressure loss down to a minimum, there is ample space and volume to allow for a wider turn and generate less
pressure drop.
b. Long radius elbows (Radius > 1.5D): Used sometimes for specific applications for transporting high viscous
fluids likes slurry, low polymer etc. For radius more than 1.5D pipe bends are usually used and these can be made to
any radius. However, 3D & 5D pipe bends are most commonly used
b. Short radius elbows (Radius = 1.0D): to be used only in locations where space does not permit use of long radii
elbow and there is a need to reduce the cost of elbows. In jacketed piping the short radius elbow is used for the core
pipe.
Here D is nominal pipe size in inches.
Elbow Radius:
For a smooth change in direction, elbows or bends are available in various radii. These radii are expressed in terms
of pipe nominal size expressed in inches. Elbows are available in two radii,
a. Long radius elbows (Radius = 1.5D)
b. Short radius elbows (Radius = 1.0D)
where D is nominal pipe size in inches.
For radius more than 1.5D, pipe bends are used and these can be made to any radius.
However, 3D & 5D pipe bends are most commonly used. Usually in chemical, petrochemical
& refinery plants, long radius elbows are widely used. Pipe bends are preferred where pressure drop is of a major
consideration. Use of short radius elbows should be avoided as far as possible due to abrupt change in direction
causing high pressure drop.

Elbow Radius
4.0 End Connections:

Page 2 of 52

The following types of end connections are available for connecting elbow/bend to pipe.
• Socket welded
• Butt welded
• Screwed
• Flanged
A. Socketed Welded Elbows:
• Pipe is connected to socket welded elbow as shown in Fig. – 5, by having a fillet weld.

Socketed Welded Elbows
• Socket welded elbows are available up to 2” nominal size. However, in UIL, our practice is to use these elbows up
to 11/2” size only.
• Dimensions of socket welded elbows are as per ASME B16.11
• Since there is possibility of fluid getting entrapped between pipe O.D and socket I.D., this may cause corrosion
called crevice corrosion. Thus use of socket welded fittings should be avoided for services where corrosion/erosion
is of great concern.
• Fillet welds are examined by using liquid dye penetrant or Magnetic particle inspection method. No radiography is
possible for checking soundness of these welds.
• Since socket welded joints cannot be radiographed, these fittings are not recommended for critical services
handling hazardous or highly inflammable fluids. For such services butt welded fittings are preferred.
• Socket welded fittings are forged and applicable material standards are as follows:

Page 3 of 52

ASTM A105 (Forged Carbon Steel)
These fittings are suitable for welding to all carbon steel pipes.
ASTM A182 (Forged Alloy Steel and Stainless Steel Fittings)
Under ASTM A182 several grades are available depending upon chemical composition.
Selection would depend upon pipe material connected to these fittings. Fitting material should have same chemical
composition as that of pipe.
Some of the grades available under ASTM A182 and corresponding connected pipe material specification are listed
below:
GRADE

PIPE MATERIAL SPEC

F11

:

ASTM A335 P11

F22

:

ASTM A335 P22

F304

:

ASTM A312 Gr.TP 304

F304L

:

ASTM A312 TP 304L

F316

:

ASTM A312 TP 316

F321

:

ASTM A316 TP321

ASTM A350 (Forged carbon and low alloy steel fittings for low temperature services)
Under ASTM A350, several grades are available depending upon chemical composition & tensile properties.
• Fittings conforming to ASME B16.11 are designated as Pressure class 2000, 3000 and 6000 fittings for threaded
and Pressure class 3000, 6000 and 9000 for socket welded ends.
This designation identified the fittings with their ratings as shown below:
(Refer Table 2, ASME B 16.11)

Pressure
Class

Type

Pipe used for Rating Basis
Schedule No./Wall
designation

2000

Threaded

80 / (XS)

3000

Threaded

160 /–

Page 4 of 52

6000

Threaded

– / XXS

3000

Socket-Welding

80 / (XS)

6000

Socket-Welding

160 /–

9000

Socket-Welding

– / XXS

The above does not restrict the use of pipe of thinner or thicker wall with fittings. However, when thinner pipe is
used, its strength may govern and when thicker pipe is used, the strength of the fitting governs the rating.
B. Butt Welded Elbows:
• Pipe is connected to butt welded elbow as shown in Fig. 6 by having a butt-welding joint.

Butt Welded Elbows
• Butt welded fittings are supplied with bevel ends suitable for welding to pipe. It is important to indicate connected
pipe thickness schedule while ordering. All edge preparations for butt welding to conform to ASME B16.25.
• Dimensions of butt welded elbows are as per ASME B16.9. This standard is applicable for carbon steel & alloy
steel butt weld fittings of NPS 1/2” through 48”
• Dimensions of stainless steel butt welded fittings are as per MSS-SP-43. Physical dimensions for fittings are
identical under ASME B16.9 and MSS-SP-43. It is implied that the scope of ASME B16.9 deals primarily with the
wall thicknesses which are common to carbon and low alloy steel piping, whereas MSS-SP-43 deals specifically
with schedule 5S & 10S in stainless steel piping.

Page 5 of 52

• Dimensions for short radius elbows are as per ASME B16.28 in case of carbon steel & low alloy steel and MSSSP-59 for stainless steel.
• Butt welded fittings are usually used for sizes 2” & above. However, for smaller sizes up to
11/2” on critical lines where use of socket welded joints is prohibited, pipe bends are used.
These bends are usually of 5D radius and made at site by cold bending of pipe.
Alternatively, butt welded elbows can be used in lieu of pipe bends but usually smaller dia lines are field routed and
it is not possible to have the requirement known at initial stage of the project for procurement purpose. So pipe
bends are preferred. However, pipe bends do occupy more space and particularly in pharmaceutical plants where
major portion of piping is of small dia. and layout is congested, butt welded elbows are preferred.
• Butt welded joints can be radiographed and hence preferred for all critical services.
• Material standards as applicable to butt welded fittings are as follows:
ASTM A234:
This specification covers wrought carbon steel and alloy steel fittings of seamless and welded construction. Unless
seamless or welded construction is specified in order, either may be furnished at the option of the supplier. All
welded construction fittings as per this standard are supplied with 100% radiography. Under ASTM A234, several
grades are available depending upon chemical composition. Selection would depend upon pipe material connected
to these fittings.
Some of the grades available under this specification and corresponding connected pipe material specification are
listed below:
GRADE
WPB

:

WPC
WP11
WP22

:
:
:

PIPE MATERIAL SPEC
ASTM A53 Gr A/B, A106 Gr A/B
IS 1239, IS 1978, IS 3589
ASTM A106 Gr.C
ASTM A335 P11
ASTM A335 P22

ASTM A403:
This specification covers two general classes, WP & CR, of wrought austenitic stainless steel fittings of seamless
and welded construction.
Class WP fittings are manufactured to the requirements of ASME B16.9 & ASME B16.28 and are subdivided into
three subclasses as follows:
WP – S Manufactured from seamless product by a seamless method of manufacture.
WP – W These fittings contain welds and all welds made by the fitting manufacturer including starting pipe weld if
the pipe was welded with the addition of filler material are radiographed. However no radiography is done for the
starting pipe weld if the pipe was welded without the addition of filler material.
WP-WX These fittings contain welds and all welds whether made by the fitting manufacturer or by the starting
material manufacturer are radiographed.

Page 6 of 52

Class CR fittings are manufactured to the requirements of MSS-SP-43 and do not require non-destructive
examination.
Under ASTM A403 several grades are available depending upon chemical composition.
Selection would depend upon pipe material connected to these fittings. Some of the grades
listed below:
GRADE
WP
304

CR
WP

CR

304
304L

PIPE MATERIAL SPEC
WP 304S :
WP304W :
WP304WX :

ASTM A312 TP304

WP304LS :
WP304LW :
WP304LWS :

ASTM A312 TP304L

304L

ASTM A420:
• This specification covers wrought carbon steel and alloy steel fittings of seamless & welded construction intended
for use at low temperatures. It covers four grades WPL6, WPL9, WPL3 & WPL8 depending upon chemical
composition. Fittings WPL6 are impact tested at temp – 50° C, WPL9 at -75° C, WPL3 at -100° C and WPL8 at
-195° C temperature.
• The allowable pressure ratings for fittings may be calculated as for straight seamless pipe in accordance with the
rules established in the applicable section of ASME B31.3.
• The pipe wall thickness and material type shall be that with which the fittings have been ordered to be used, their
identity on the fittings is in lieu of pressure rating markings.
C. Screwed Elbows:
• These are usually used for Galvanised piping where all joints are screwed type. Fittings used are also galvanized
on such lines.
• Following standards are usually adopted for galvanized screwed fittings.
IS 1239 Part II
ASTM A105 or ASTM A181 Class 60 forged & galvanized and dimensions conforming to ASME B16.11.
• Usually we do not use fittings conforming to IS 1239 part II because the same are not forged and get cracked while
tightening. Forged fittings having dimensional standard conforming to ASME B16.11 are preferred. For pressure
rating of these fittings, refer Paragraph on pressure ratings of socket welded fittings.
• Screwed joints are made by using teflon tape for sealing.
• There is always a possibility of leakage through screwed joints. These type of joints are not recommended for
hazardous fluids.

Page 7 of 52

• Sometimes, seal welding is done for screwed joints in order to avoid leakage. However screwed connection at
instruments shall not be seal welded.
• Pipe threads are usually as per IS554 taper.
D. Flanged Elbows:
• Usually flanged elbows are used on cast-iron piping. Cast steel flanged elbows with liner are used to some extent
for lined piping such as carbon steel-PTFE lined (Refer chapter on lined-piping)
• Following standards are usually adopted for flanged elbows & other fittings:
ASME B16.1 (Cast Iron Pipe Flanges and Flanged Fittings; Classes 25,125 and 250)
ASME B16.5 (Pipe Flanges and Flanged Fittings).
• As per ASME B16.1, cast iron fittings are available in classes 25, 125, 250. Based on pressure-temperature
conditions, proper rating can be selected as per table 2 ASME B16.1. All ratings are dependent on the contained
fluid and are the maximum non shock pressures at the tabulated temperature.
• All class 25 & 125 flanged fittings are furnished with flat face. All class 250 flanged fittings are furnished with
0,06 inch high raised face and finished in accordance with MSS-SP-6.
• The minimum material requirements for flanged cast iron fittings shall be as follows:

Rating

Size

Class of Iron

25

All

ASTM A126 Class A

125

1″ – 12″

ASTM A126 Class A or B

125

14″ & above

ASTM A126 Class B

250

1″ – 12″

ASTM A126 Class A or B

250

14″ & above

ASTM A126 Class B

The equivalent IS material usually used is IS 210 Gr. 220.
E. Mitre Elbows:
• These are usually used for low pressure, low temperature non critical services having 14” inches and above. They
are economical as compared to elbows in higher sizes and hence preferred.

Page 8 of 52

• Mitre bends are usually fabricated at site out of pipe by cutting and re-welding spools as shown in Fig. 7. The
Figure is for 5 piece 4 weld mitres. The change in direction at every weld is 22 1/2 °. We may also have 4-piece 3weld mitre where change in direction at every weld would be 30°. Usually 5 piece 4 weld mitres are preferred in
order to have smooth flow.

• Usually effective radius of mitre-bend, defined as the shortest distance from the pipe centre line to the intersection
of the planes of adjacent mitre joints is 1.5D where D is the nominal pipe size in inches. However, one can select
any other radius if called for.
• It is recommended to fabricate mitre bends after knowing length of Arm-1 & Arm-2 up to next weld (Refer Fig. 7).
So as to avoid two additional welds.
• Because of high stress intensification factor they are not recommended on high temperature lines.
• Pressure-temperature rating for mitre bend is not the same as for pipe and in order to withstand same pressuretemperature conditions as applicable to pipe, a higher thickness is required for mitre bend.
As per ASME B31.3 (Cl. 304.2.3), the maximum allowable internal pressure shall be the lesser value calculated
from equation given below :
These equations are not applicable when θ exceeds 22.5°

Page 9 of 52

Where
Pm = Maximum allowable internal pressure for mitre bend.
T = Minimum Miter Pipe wall thickness.
C = Sum of mechanical & corrosion allowances.
R1 = Effective radius of mitre bend.
r2 = Mean radius of pipe using nominal wall thickness.
S = Allowable stress of material at the given temperature.
E = Quality factor as applicable to pipe used for mitre bend.
θ = Angle of mitre cut or 1/2 the angle of change in direction at mitre joint.
Thickness ‘T’ used in above equations shall extend a distance not less than ‘M’ from the inside crotch of the end
mitre welds where,
M

=

larger of 2.5 (r2 × T) 0.5 or tan θ (R1 – r2).

Usually extra thickness is available in pipe used for low pressure services and it is possible to use the same pipe for
making mitre bends. However a check is always required.
• An angular offset of 3° or less does not require design consideration as a mitre bend.

Page 10 of 52

There are three major parameters which dictate the radius selection for elbow. Space availability, cost and pressure
drop.
Pipe bends are preferred where pressure drop is of a major consideration.
Use of short radius elbows should be avoided as far as possible due to abrupt change in direction causing high
pressure drop.
Minimum thickness requirement:
Whether an elbow or bend is used the minimum thickness requirement from code must be met. Code ASME B 31.3
provides equation for calculating minimum thickness required (t) in finished form for a given internal design
pressure (P) as shown below:

Fig.3: Code equation for minimum thickness requirement calculation
Here,
R1 = bend radius of welding elbow or pipe bend
D = outside diameter of pipe
W = weld joint strength reduction factor
Y = coefficient from Code Table 304.1.1
S = stress value for material from Table A-1 at maximum temperature
E = quality factor from Table A-1A or A-1B

Page 11 of 52

Add any corrosion, erosion, mechanical allowances with this calculated value to get the thickness required.
End Connections:
For connecting elbow/bend to pipe the following type of end connections are available

Butt welded: Used along with large bore (>=2 inch) piping


Socket welded: Used along with pipe size



Screwed:



Flanged:
Butt welded Elbows:

Pipe is connected to butt welded elbow as shown in Fig. 4 by having a butt-welding joint.




Butt welded fittings are supplied with bevel ends suitable for welding to pipe. It is important to indicate the
connected pipe thickness /schedule while ordering. All edge preparations for butt welding should conform to
ASME B16.25.
Dimensions of butt welded elbows are as per ASME B16.9. This standard is applicable for carbon steel &
alloy steel butt weld fittings of NPS 1/2” through 48”.

Fig.4: A typical Butt-Welded Elbow
Dimensions of stainless steel butt welded fittings are as per MSS-SP-43. Physical dimensions for fittings
are identical under ASME B16.9 and MSS-SP-43. It is implied that the scope of ASME B16.9 deals primarily
with the wall thicknesses which are common to carbon and low alloy steel piping, whereas MSS-SP-43 deals
specifically with schedule 5S & 10S in stainless steel piping.

Dimensions for short radius elbows are as per ASME B16.28 in case of carbon steel & low alloy steel and
MSS-SP-59 for stainless steel.

Butt welded fittings are usually used for sizes 2” & above. However, for smaller sizes up to 1-1/2” on
critical lines where use of socket welded joints is prohibited, pipe bends are normally used. These bends are
usually of 5D radius and made at site by cold bending of pipe. Alternatively, butt welded elbows can be used in
lieu of pipe bends but usually smaller dia lines are field routed and it is not possible to have the requirement
known at initial stage of the project for procurement purpose. So pipe bends are preferred. However, pipe bends
do occupy more space and particularly in pharmaceutical plants where major portion of piping is of small dia. and
layout is congested, butt welded elbows are preferred.

Butt welded joints can be radiographed and hence preferred for all critical services.




Material standards as applicable to butt welded fittings are as follows:
ASTM A234:
This specification covers wrought carbon steel & alloy steel fittings of seamless and welded construction. Unless
seamless or welded construction is specified in order, either may be furnished at the option of the supplier. All
welded construction fittings as per this standard are supplied with 100% radiography. Under ASTM A234, several
grades are available depending upon chemical composition. Selection would depend upon pipe material connected
to these fittings.

Page 12 of 52

Some of the grades available under this specification and corresponding connected pipe material specification are
listed below:

ASTM A403:
This specification covers two general classes, WP & CR, of wrought austenitic stainless steel fittings of seamless
and welded construction.
Class WP fittings are manufactured to the requirements of ASME B16.9 & ASME B16.28 and are subdivided into
three subclasses as follows:
WP – S Manufactured from seamless product by a seamless method of manufacture.
WP – W These fittings contain welds and all welds made by the fitting manufacturer including starting pipe weld if
the pipe was welded with the addition of filler material are radiographed. However no radiography is done for the
starting pipe weld if the pipe was welded without the addition of filler material.
WP-WX These fittings contain welds and all welds whether made by the fitting manufacturer or by the starting
material manufacturer are radiographed.
Class CR fittings are manufactured to the requirements of MSS-SP-43 and do not require non-destructive
examination.
Under ASTM A403 several grades are available depending upon chemical composition. Selection would depend
upon pipe material connected to these fittings. Some of the grades available under this specification and
corresponding connected pipe material specification are listed below:

ASTM A420:
This specification covers wrought carbon steel and alloy steel fittings of seamless & welded construction
intended for use at low temperatures. It covers four grades WPL6, WPL9, WPL3 & WPL8 depending upon
chemical composition. Fittings WPL6 are impact tested at temp – 50° C, WPL9 at -75° C, WPL3 at -100° C and
WPL8 at -195° C temperature.

The allowable pressure ratings for fittings may be calculated as for straight seamless pipe in accordance
with the rules established in the applicable section of ASME B31.3.

The pipe wall thickness and material type shall be that with which the fittings have been ordered to be used,
their identity on the fittings is in lieu of pressure rating markings.


The term SIF indicates a multiplier of Bending and Torsional stresses. This Intensifier acts local to a piping
Component (tees, elbows, bends, Olets, etc.) and value depends on component geometry. The minimum value

Page 13 of 52

of SIF is 1.0. It is widely used by piping stress engineers in places where the actual stress calculation is quite
difficult due to its difficult geometry (Varying thickness, cross section, curvature etc.) as unlike straight Pipes
the simple Beam theory is not applicable. So in this situation it is required to assume additional stresses by
suitably incorporating a SIF.
Stress Intensification Factor for a Piping Bend/Elbow:
In layman’s language the SIF of a bend or elbow can be defined as the ratio of bending stress of an elbow to that
of straight pipe of same diameter and thickness when subjected to same bending moment. Whenever the same
bending moment is applied to a bend because of ovalization the bending stress of the elbow will be much higher
than that of straight pipe. That is why the SIF value will always be greater than or equal to 1.0 (for straight
pipe).
The process piping code ASME B 31.3 provides a simple formula to calculate the SIF of a bend or elbow. As
per that code
SIF in-plane = 0.9 / h^(2/3)
SIF out-plane = 0.75 / h^(2/3)
Here h=T R1 / r2^2
h =Flexibility characteristics, dimensionless
T =Nominal wall thickness of bend, in
R1 =Bend radius, in
r2 =Mean radius of matching pipe, in
The in plane and out plane concept for a bend can be obtained from the attached figure from code or in
layman’s language the same can be explained as follows:
The in-plane bending moment is the bending moment which causes elbow to close or open in the plane formed
by two limbs of elbow.
In a similar way the out plane bending moment can be defined as the bending moment which causes one limb of
elbow to move out of the plane keeping other limb steady.
From the above mentioned equations the following can be interpreted:
For the same pipe size and same pipe thickness
1. A short radius elbow is having more SIF as compared to a long radius elbow.
2. With increase in bend radius the SIF decreases and finally reaches to 1.0 for straight pipe.
3. The SIF for a 45 degree elbow and a 90 degree elbow is same as bend radius is same.
4. With increase in nominal pipe thickness or schedule the SIF of a bend (90 degree) keeps on decreasing till its
value is equal to 1.0.

Page 14 of 52

Carbon steel:
ASTM A53- welded and seamless pipe, black and galvanised.
ASTM A106- Seamless cs pipe for high temperature services.
ASTM A672- Electric fusion welded steel pipe for high pressure service at moderate temperature services.

Stainless steel:
ASTM A312- Seamless and welded steel pipe for low temperature services.
A409-welded large diameter austenitic steel pipe for corrosive and high temperature services.
ASTM A358- Electric fusion welded austenitic chrome -nickel steel pipe for high temperature services.

Low alloy steel:
ASTM A335- Seamless ferritic alloy steel pipe for high temperature services.
ASTM A691- Carbon and alloy steel pipe, electric fusion welded for high pressure service at high temperature.

Low temperature carbon steel:
ASTM A333- Seamless and welded steel pipe for low temperature services.
ASTM A671- Electric fusion welded steel pipe for atmpospheric and low temperature services(sizes >=16in NB)
Pipe
Based on Manufacturing Process Pipes can be classified as below
1.

Seamless Pipe

2.

Welded Pipe

a. EFW-Electric Fusion Welded
1.

i.

2.

ii.

Longitudinal SAW Pipe
Spiral SAW Pipe

b. ERW – Electrical Resistance welded Pipe

Page 15 of 52

1.

Seamless Pipe

ž Mandrel Mill
->This process is used to make smaller sizes of seamless pipe, typically 1 to 6 inches (25 to 150 mm) diameter.
-> The ingot of steel is heated to 2,370 °F (1,300 °C) and pierced.

Page 16 of 52

-> A mandrel is inserted into the tube and the assembly is passed through a rolling (mandrel) mill.
->Unlike the plug mill, the mandrel mill reduces wall thickness continuously with a series of pairs of curved rollers
set at 90° angles to each other.
->After reheating, the pipe is passed through a multi -stand stretch-reducing mill to reduce the diameter to the
finished diameter.
->The pipe is then cut to length before heat treatment, final straightening, inspection, and hydrostatic testing.
Plug Mill
->This process is used to make larger sizes of seamless pipe, typically 6 to 16 inches (150 to 400 mm) diameter.
->An ingot of steel weighing up to two tons is heated to 2,370 °F (1,300 °C) and pierced.
->The hole in the hollow shell is enlarged on a rotary elongator, resulting in a short thick-walled tube known as a
bloom.
->An internal plug approximately the same diameter as the finished diameter of the pipe is then forced through the
bloom.
->The bloom containing the plug is then passed between the rolls of the plug mill.
->Rotation of the rolls reduces the wall thickness
->The tube is rotated through 90° for each pass through the plug mill to ensure roundness.
->The tube is then passed through a reeling mill and reducing mill to even out the wall thickness and produce the
finished dimensions.
-> The tube is then cut to length before heat treatment, final straightening, inspection, and hydrostatic testing.

Page 17 of 52

2.
Welded Pipes
a.

EFW Pipe
1.

i.

Longitudinally Welded Pipe

->Welded pipe (pipe manufactured with a weld) is a tubular product made out of flat plates, known as skelp, that are
formed, bent and prepared for welding. The most popular process for large diameter pipe uses a longitudinal seam
weld. The welds are made by heating with an electric arc between the bare metal electrodes.
->Pressure is not used. Filler metal for the welds is obtained from the electrodes.
->For diameters above 36 inches, double seam welded pipe is specified as an alternative in API 5L. This has two
longitudinal seams.

Page 18 of 52

Longitudinally Welded Pipe

EFW Pipe Manufacturing Process
2.

Spiral welded pipe

->As an alternative process, spiral weld construction allows large diameter pipe to be produced from narrower plates
or skelp.
->The defects that occur in spiral welded pipe are mainly those associated with the SAW weld,

Page 19 of 52

->An additional problem with early spiral welded pipe was poor dimensional accuracy, particularly out of roundness
at the pipe ends. This led to problems of poor fit-up during field girth welding. Spiral line pipe gained a poor
reputation in some companies as a result of these early experiences.
->Considered suitable only for low pressure applications such as water pipe.
b. Electric Resistance Welded (ERW)
->Solid phase butt weld, was produced using resistance heating & high pressure to make the longitudinal weld
(ERW),
->Nowadays Most pipe mills now use high frequency induction heating (HFI) for better control and consistency.
However, the product is still often referred to as ERW pipe, even though the weld may have been produced by the
HFI process.
->The defects that can occur in ERW/HFI pipe are those associated with strip production, such as laminations and
defects at the narrow weld line.
->Lack of fusion due to insufficient heat and pressure is the principal defect, although hook cracks can also form due
to realignment of non metallic inclusions at the weld interface. Because the weld line is not visible after trimming,
and the nature of the solid phase welding process, considerable lengths of weld with poor fusion can be produced if
the welding parameters fall outside the set limits.
->In addition, early ERW pipe was subject to pressure reversals, a problem that results in failure in service at a lower
stress than that seen in the pre-service pressure test. This problem is caused by crack growth during the pressure test
hold period, which in the case of early ERW pipe was due to a combination of low weld line toughness and lack of
fusion defects.

Technical requirements for Pipes & Fittings
for preparation of Purchase Requisition




18th February 2015
want2learn
Detail Design




0 Comments
20
0
0

While preparing the purchase requisition/inquiry of any piping component there are various
points which need to be checked and confirmed with the vendor. The responsible requisition
engineer should include all the technical points & clauses applicable to the piping
components in the requisition/inquiry & subsequent technical queries (TQ).
The requisition engineer should refer all the project specific standards and specifications
along with the applicable international codes and standards while preparing the inquiry
requisition of the piping components. In this article few general technical requirements for
pipes & fittings are listed for information. Note that these requirements may vary depending
upon the project requirements.

Page 20 of 52

General requirements:


Pipe and Fitting Material supplied must be strictly in accordance with the latest codes
and standards, mentioned in the Material Requisition (MR or PR: Purchase Requisition)
Scope of supply. This specification for pipes and fittings as detailed in subsequent points
shall supplement the codes and other project specifications.



All items must be supplied in accordance with proper wall thickness/ schedule as
stated in the Purchase Requisition (PR). Wall thickness thinner or heavier than specified
tolerance shall not be accepted.



Vendor must specify the material type and grade together with NPS and schedule /
wall thickness / class within the Material requisition – Scope of Supply for all piping
components.



Butt weld end preparation for pipes, fittings and flanges shall be as per ASME B16.25.



100% radiography has to be performed for all welded items to give a joint factor of
1.0. If not specified, Pipes and fitting shall be supplied seamless. Seamless is an
acceptable alternative for welded pipe and fittings but vice-versa is not acceptable.



The chemical analysis of Carbon Steel (CS) & Low Temperature Carbon Steel (LTCS)
pipes and fittings, forgings, plates shall be in accordance with the applicable product
standard with the following limitations:

Carbon 0.23 Maximum wt% (pipes)
Carbon 0.23 Maximum wt% (forgings)
Carbon Equivalent (CE) shall not exceed 0.43%
Where CE = C + Mn/6 + (Cr+Mo+V)/5 + (Cu+Ni)/15
The above formula for CE is applicable when the carbon content is greater than 0.12%


CS & LTCS materials shall be fully killed and fine grained and shall be produced by a
low sulphur and low phosphorous refining process. The components must be supplied in
normalized or normalized and tempered condition.



All Austenitic stainless steel, duplex stainless steel items must be supplied in solution
annealed and quenched condition as per corresponding ASTM standard.



Repair welding for parent plate / weld end flange is not accepted.



The carbon content of SS 316 must be limited to 0.03%. All SS Materials specified as
F 316 / WP 316/ Type 316 may be dual certified for both SS 316 & 316L, if specifically
mentioned in the project specification.



Austenitic stainless steel has to be capable of passing an inter-granular corrosion test
in accordance with ASTM A262, Practice E.



All duplex stainless steel shall have ferrite content between 35% – 65% (volume
fraction) on base metal and on heat affected zone to 35% – 70 % as per ASTM E562 four
point count method.

Requirements for Pipes:

Page 21 of 52



Dimensions of CS / SS and Alloy steel (AS) pipe shall comply with ASME B36.10M or
ASME B36.19M as applicable.



CS pipes shall be supplied in double random lengths (11 to 13m) for pipe sizes 2” to
36”, and in single random lengths (5 to 7m) for pipe sizes 1.5” and smaller.



SS, Duplex Stainless Steel (DSS) and Carbon Steel galvanized pipes shall be supplied
in single random lengths (5 to 7m) for all pipe sizes.



It is not permitted to join lengths of pipe by circumferential welds to make single or
double random lengths.



Plain end pipes must have square ends cut with burrs removed.



All stainless steel pipes shall be supplied in solution annealed condition.



All threaded & coupled pipes shall be supplied with ends threaded in accordance with
ASME B1.20.1 (NPT).



Each length of the threaded pipe shall be supplied with full coupling screwed hand
tight at one end.



Galvanizing of pipes shall be in accordance with ASTM A153. Threaded portion of
pipes shall be free of galvanizing.



Pipes shall be heat treated in accordance with product specification requirements
after completion of all forming and welding operations.



Carbon Steel & Low Temperature Carbon Steel (LTCS) Pipes shall be fully killed fine
grained and shall be supplied in normalized or normalized and tempered condition.



Welded pipe shall be supplied with single straight seam for sizes up to 36” and
double straight seam for sizes greater than 36” subjected to approval from the
contractor.




Spiral seam welds are not acceptable.
All DSS welded pipes with a wall thickness greater than 30 mm must be 100%
ultrasonically examined.

Requirements for Fittings:


Dimensions of butt welded fittings must be in accordance with ASME B16.9.



Forged, threaded and socket welded fittings shall be in accordance with ASME
B16.11.



Other fittings dimensions shall comply with MSS SP-75, MSS SP-95, MSS SP-97 or BS
3799 as applicable.



Vendor shall provide calculations as per ASME B31.3 for the fittings not covered
under the above mentioned standards.



Union dimensions shall be in accordance with BS 3799.



All screwed fittings shall be threaded NPT in accordance with ASME B1.20.1.



Branch reinforcing fittings (i.e. Elbowlets, Sockolets, weldolets, etc.) shall be designed
in accordance with the requirements of ASME B31.3. The vendor shall submit drawings
during bid stage and calculations for review and approval after award of contract.



Butt weld elbows shall be long radius type (radius =1.5 nominal pipe size). Short
radius elbows are not permitted.

Page 22 of 52



For reducing fittings specified with two schedules in the Inquiry / Purchase
description, the first schedule refers to the larger end or run pipe, the second schedule
refers to the smaller end or branch pipe.



Fittings shall be forged to the final shape and size. Fittings shall not be machined
from bar stock or solid forged billets without specific approval.



Galvanizing of fittings shall be in accordance with ASTM A153. Threaded portion of
fittings shall be supplied with threads free of galvanizing.



Swage nipple shall be pipe swaged by forging only. Machining of bar stock, forgings
or heavy wall pipe not permitted. Dimensions shall be in accordance with MSS-SP-95.



All reduction sizes for tees and reducers to be in accordance with ASME B16.9.



CS & LTCS fittings shall be fully killed and fine grained and shall be supplied in
normalized or normalized and tempered condition.



100% of CS & LTCS welded fittings, with wall thickness greater than Sch 80 shall be
examined by Magnetic Particle Examination for weld bevel ends. Acceptance standards
shall be in accordance with ASME VIII Division 1, Appendix 6. This shall be done after final
heat treatment.



100% of SS & DSS wrought fittings having wall thickness more than 20mm shall have
the bevel and weld end over a width of 25mm, examined by Dye penetrant Method.
Acceptance standards shall be in accordance with ASME VIII Division 1, Appendix 8.



100% of DSS welded fittings with a wall thickness greater than 30mm shall be 100%
ultrasonically examined in accordance with ASME VIII Division 1.



100% of DSS forged fittings weld bevels shall be examined by Dye Penetrant
inspection.



100% of CS, LTCS & SS forged fittings, with wall thickness greater than Sch 80 shall
be examined by Magnetic Particle / Dye penetrant examination. Acceptance standards
shall be in accordance with ASME VIII Division 1, Appendix 6 / 8. This shall be done after
final heat treatment.

Positive material identification:


Positive Material Identification (PMI) shall be conducted for all SS / CRA alloy piping
items as per the project specification included in the Inquiry / Purchase requisition.

Special Requirements:
Sour service requirements:


All materials specified for sour service shall, as a minimum, meet the requirements of
NACE MR0175 / ISO 15156 – latest edition.



All welded pipes / fittings in sour service shall be HIC tested, if required by the project
specification. It shall be conducted for one pipe / fitting per heat in accordance with NACE
TM-0284 Solution – A with acceptance criteria as specified in NACE MR-0175.

Impact test requirements:


All CS, LTCS, welded austenitic and duplex stainless steel piping components shall be
impact tested (for using in low temperature services) in accordance with ASME B31.3.

Page 23 of 52



For carbon steel pipes and fittings, the impact test temperature shall be the
‘minimum metal temperature’ as defined in the project. The impact test requirement and
acceptance criteria shall be as per Cl. 323.2.2 and Cl. 323.3.5 of ASME B31.3 respectively.



For welded SS and DSS items, the impact test temperature shall be the ‘minimum
metal temperature’ as defined in the project but not more than (-101 Deg. C) and (-50
Deg. C) respectively. For SS items, the acceptance criteria shall be as per Cl. 323.3.5 of
ASME B 31.3. For DSS items, test results shall be at least 40 joules in transverse direction
(for standard specimen 10 x 10 mm) as an average of three tests, one result may be
lower but not less than 30 joules.



For LTCS items, the impact test temperature shall be (-46 Deg. C). Test results shall
be at least 27 joules as an average of three tests (for standard specimen 10 x 10 mm),
one result may be lower, but not lower than 21 joules.

Plastic Piping System: A Tool Against Chemical Corrosion – Part 1
1. Introduction to Plastic Piping System:
Because corrosion is a problem in operating and maintaining any Chemical Process Plant, one would prefer avoiding
steel completely as a piping material but since its not feasible because of the usefulness of steel in sustaining the
Pressure and Temperature conditions normally foreseen in any Process Plant. That brings the concept of composite
piping constructed from the highly Chemical Resistant Polymer Compounds as base material, reinforced with
suitable fibrous materials such as Glass which provides it the requisite strength.
2. PLASTIC MATERIALS:
Basically 3 types of Synthetic Polymer Components have found acceptance in industrial use.

Page 24 of 52



Thermoplasts



Thermosets



Composite Plastics

2.1 Thermoplasts:
The Thermoplastics are Polymer Compounds, which are normally available in crystal form.
On application of heat and pressure these crystals attain the requisite level of flowability to be able to attain the
desired shape by molding process. On re-heating the plastic material can once again undergo the transformation
from solid to a flowable state which allows their reprocessing into the desired shape.
Some of the commonly used Thermoplasts are as follows


Polyethylene



Polypropylene



Polystyrene



Polyvinyl Chloride



Fluor-Plastics

By and large the thermoplastics are structurally weak materials and have limited temperature endurance.

Page 25 of 52

Fig 1.Thermoplast Piping Components
2.2 Thermosets:
The Thermosetting Plastics are Polymer Compound (resins), which are normally available in liquid form at ambient
temperature. On addition of Catalyst and Accelerator these Resins undergo a chemical transformation into a rigid
product that sets into the required shape by curing process.
Some of the commonly used Thermosetting Plastics are as follows.


Epoxies



Furans



Phenolics



Polyesters – Bisphenol, Isophthalic, Halogenated



Polyurethane



Vinyl esters

Even though the Thermosetting Plastics are relatively superior to Thermoplastics in terms of structural strength and
temperature endurance, still in its virgin form they find limited use in Industrial applications.

Page 26 of 52

Fig 2.Thermoset Piping Components
2.3 Composite Plastics:
As it is evident from the foregoing discussion that both Thermoplastics and Thermosetting Plastics in their virgin
form lack ability to sustain the level of mechanical loading normally encountered in the Industrial applications. An
attempt to strike an appropriate balance between the two desired properties of the material (i.e. Mechanical Strength
and Corrosion Resistance) therefore has always remained a desirable objective. This brought forward the concept of
Composite Plastics where in a reasonable degree of mechanical strength is imparted to the base Polymer which in
itself is adequately resistant to the Chemical Corrosion, by way of reinforcing it with a suitable reinforcing material.
Most of the commercially available composite materials in the Reinforced Plastic category use
a combination of Thermosetting Plastic Resins (e.g. Polyester, Epoxy, Vinyl Ester etc.) and Fiberglass or Synthetic
Fibers as reinforcing material. In order to provide an ultra superior chemical resistance, it is also possible to
manufacture a composite material using Thermoplastic Material (e.g. PVC, PVDF, PP etc) as a base liner over which
the layers of Thermosetting Resins and Fiberglass are applied to attain the required mechanical strength.
Manufacturing Process:
The composite plastics pipes are commonly produced by 1 of the following methods


Custom Contact Molding:

It is a manual/ semi automated process in which the composite sections are manufactured by application of various
layers of resin and Glass Fibers (in various forms such as surface mat, roving mat, chop-strand mat etc.) either by
Hand Lay-up or by Spray Lay-up method.


Filament Winding:

It is a fully automatic process in which an automatic control over winding angle (0 to 90 degree) and winding
pressure can be exercised to obtain the varying degree of Hoop – Axial ratio and Glass – Resin percentage
composition. Normally a winding angle of 54 3/ 4 Degree provides a 2:1 Hoop – Axial ratio which is condition of
optimum internal pressure requirement. By increasing the winding pressure the Glass – Resin proportion could be
varied from 80 % – 20 % to 60% – 40 %. A composite section of high Glass content will result into high strength
and low chemical resistance and visa versa.

Page 27 of 52



Pultrusion:

As the name implies this is a sort of extrusion process by pulling the filaments through a resin bath tub and
subsequently passing it through an extruding die and then through a an atmosphere of controlled elevated
temperature. The above process is commonly used for manufacturing rolled sections such as Angles, Channels, I
Beams etc.


Resin Transfer Molding:

The above process is used for specialized applications for manufacture of sandwich structures with certain core
material.

Fig 3.Composite Piping Components
3. TYPICAL MECHANICAL PROPERTIES OF THERMOSETTING PLASTIC:
The Reinforced Thermosetting Plastic Material typically represents a mechanically weak structure with high
coefficient of thermal expansion, low thermal conductivity and high strength – weight ratio. The approximate values
of various mechanical properties of the Reinforced Plastic are in the following range.
Density 0.055 – 0.065 Lbs / inch3
Coefficient of 9 – 13 in/ in O F x 10-6
Thermal Expansion

Page 28 of 52

Modulus of Elasticity 1.0 – 3.0 PSI * 106
Ultimate Tensile Strength 12 – 100 PSI * 103
Yield Strength 12 – 100 PSI * 103
Thermal Conductivity 1.5 – 2 BTU/ Hr. Ft OF
1.0 PLASTIC PIPING SYSTEM:
The Plastic Piping System consists of Piping Profile fabricated from plain end pipe, plain and flanged end Fittings
(i.e. Elbows and Reducers) and stub-in branch connections. The Flanged Joints are Stub Ends with loose Backing
Flanges. In case of Flanged Tapping Long Stub Flanges are recommended to be used in place of pipe stub-in and
Short Stub Flanges.
The pipe to pipe and pipe to fittings joints are laminated joints. Accessories to Piping System include Soft Rubber/
CAF Gaskets and Full Threaded Fasteners with Washers.
1.1 Design Considerations for Plastic Piping:


Owing to weak mechanical properties a minimum of NS 2” line size is recommended for Plastic Piping.
However tapping of small size (i.e. smaller than NS 2”) are permitted for drain/ vent etc. provided the
branch connection is adequately supported.



Since the piping joints employed as per most Standard are laminated joints (Refer DIN 16966 Part 8 for
details) requiring a large overlap length, care shall be taken to ensure adequate spacing between the joints
to avoid the overlapping of the laminate structure.



Owing to its large Co-efficient of Thermal Expansion the Plastic Pipelines exhibit a high tendency to grow
under moderate temperatures. This may result into sizable deflection of the branches and the corners of the
Piping Profile. It shall therefore be ensured that the branch connections are not over stressed, either by
providing adequate flexibility on the branch piping or by fixing the branch points by external means to
disallow its deflection.

If free movement of the corners of the piping profile can be allowed (i.e. e.g. not being hindered by any other
external item) then it is preferable to leave the profile to grow freely.
However if the growth of the profile has any adverse effect on the system stability (i.e. e.g. supports falling off from
the external structure) it may be appropriate to restrict the growth of the sides of the profile by providing fixed
supports at various locations as per Plastic Piping Support recommendations.


Unlike Steel, bellows are not used on Plastic Piping. The thermal stress behavior is addressed either by
providing in-built flexibility in the system or by arresting the axial growth of the pipe runs within the pipe
length itself. In case the later method is employed, the pipe may have to be guided at close intervals to
avoid failure due to buckling.



Owing to its weak nature, the plastic piping shall not be supported by a line contact between the pipe
surface and the external structure taking the load. Hence as a general rule Clamp and Shoe type supports
shall be employed on Plastic Piping System

Page 29 of 52



All concentrated loads (e.g. On-line Valves, Instruments etc) shall be directly supported to ensure that the
load is transferred to the grade/ external structure without stressing the piping.



All the valves employed on Plastic Piping shall be provided a Fixed Type Support to ensure that the Piping
is not over stressed in case of jamming of the Valve hand wheel while operating.



Due to excess thickness of Plastic Pipe (as compared to Steel) it is likely to obstruct the opening of the flap
of Sandwich type Butterfly/ Wafer Check Valve into the pipe. In order to address the above issue the Spacer
Rings (made of same or equivalent material as pipe) will be employed across the valve. The above Spacer
Ring is procured as a Special Part.

1.2 Bill of Material Considerations for Plastic Piping:
The Bill of Material for Plastic Piping is worked out similar to the steel piping with the following exceptions.


Since most Standard requires the Flanged (one end or both end flanged) Fittings i.e. Elbows and Reducers
to be shop fabricated it requires a careful consideration to assess the precise requirement of the Flanged
Fitting of each type and differentiate the same from the plain end fittings.



Since all Branch connections are stub-in type the material required for fabricating branch connections shall
be accounted for, while computing the pipe quantities.



In case of Flanged Tapping the branch connection is made by employing Long Stubs Flange instead of pipe
stub-in with a Short Stub Flange. Care shall therefore be exercised to differentiate the above Flanges
Tapping from the rest of branches to be able to estimate the requirement of Long and Short Stub Flanges
accurately.



Spacers shall be accounted for (as Special Parts) across all Sandwich Type Butterfly Valves and Wafer
Check Valves.

1.3 Technical Specification Considerations for Plastic Piping:


The Vendors scope includes supply, fabrication, erection, supporting and testing of Plastic Piping as per the
Enquiry Document.



Items such as Gaskets, Fasteners, On-line Valves, Instruments, Special Parts are excluded from the
Vendor’s scope.



All Piping items in Vendors scope shall be fabricated by Hand Lay-up method to ensure superior Chemical
Resistance properties.



The whole Laminate Structure shall be UV absorbent.



The Piping items shall be fabricated and supplied as per the UN 3030 –16 (Part-1) and all other relevant
DIN Standards referenced there in.



The Stub Ends for Flanges shall be fabricated as monolithic structure



The Flanged Elbows shall be in accordance with DIN 16966 Part-2 without the straight portion.

Page 30 of 52



The Piping Material shall comply with the General Quality and Testing Requirements as per DIN 16966
Part 1



The Inspection and Testing Shall include, but not limited to, the following test

Short Term Hydro test
Laminate Structure and Glass Content
Adhesive Shear Strength
Hardness Test (Styrene Content)
Surface Finish and Dimensional Check


FRP Piping with Thermoplastic (e.g. PVC, PP etc) liner shall be subject to additional leak test using air at
0.5 Bar-g (max) prior to lamination of liner weld seams.



It is recommended to follow the Laminate Structure of the FRP Piping as per most Technical Specification.
The Vendor shall confirm the same for the specified wall thickness indicated in the Enquiry Document.
Alternatively the Vendor can propose its own Laminate Structure for company’s review and approval.

1.4 Installation Consideration for Plastic Piping:


The Plastic Piping System shall be installed with permanent supports in place. Erection of Plastic Piping
with temporary supports is not acceptable.



The pipes shall not be stretched in order to match the terminal ends



The Flange Joints shall be tightened to the specified Torque Value only by employing Torque Wrench.



As far as possible the Piping profile shall be prefabricated in the Vendors shop at site, leaving only a few
field joints for final fit-up.



In case of FRP Piping with Thermoplastic Liner, the Field Weld will always be located at the convenient
height/ location to allow down hand welding/ jointing.

Page 31 of 52

Fig 1.Composite Piping System

Introduction to Rubber Lined Piping:
Corrosion is a menace in operating and maintaining a Chemical Process Plant. Hence given a choice one would be
tempted to dispense away with Steel all together as a material of construction for piping used in a Chemical Plant.
Unfortunately it is not practical to undermine the usefulness of Steel in sustaining the Pressure and Temperature
conditions normally foreseen in any Process Plant. That brings the concept of composite piping wherein an attempt
is made to make use of the mechanical strength of Steel, at the same time to impart a high degree of corrosion
resistance to the wetted surface of the component made of Steel.
Carbon Steel Piping internally lined with Rubber is a classic example of such composite piping. Due to the intimate
bonding between Rubber and Steel during vulcanizing process, it provides one of the most practical solutions in
dealing with chemically corrosive fluids within the limitations posed by the endurance of Rubber for the operating
temperatures.
LINING MATERIAL:
Following are the commonly used Rubber varieties in the Chemical Plant in general

Page 32 of 52



Natural Rubber



Butyl Rubber



Nitrile Rubber



EPDM

LINING PROCESS:
The Rubber Lining is a process of application of liner material (normally in the form of rubber sheets or extruded
tubes) over the internal surface of the steel piping followed by vulcanizing at the required temperature to attain the
desired degree of hardness.
The Lining Process generally consists of following steps


Inspection of Piping Items for verifying its fitness for the purpose. The aspects which need to be considered
with respect to above, are the accessibility of the internal surface for application of lining and suitability of
the internal contours for achieving a defect free lining.

Note: In order to provide reasonable access to the internal surface of the Piping for application of liner, necessitates
that Piping profile is broken down into flanged spools/ fittings of predetermined dimensions.


Surface preparation in terms of removal of scale/ rust either by wire brushing or sand/ shot blasting.



Application of Rubber Solution/ lining material



Curing of Liner material (i.e. vulcanizing) at the required temperature either by employing hot water or
steam. The vulcanizing of Rubber could also be done at ambient temperature by adding certain accelerators
along with the filler materials used in the Rubber Stock.



Inspection of the lined surface for possible defects such as pin holes/ blisters etc.



Hydro testing of the lined components

Page 33 of 52

Fig 1 Rubber Lined Piping

Fig 2: Rubber Lined Fittings

Page 34 of 52

RUBBER LINED PIPING SYSTEM:
The limited temperature endurance of the Rubber Lining Material prohibits any welding on steel subsequent to
lining. That means that the Rubber Lined Piping System needs to be necessarily prefabricated. At the same time the
total profile is also required to be broken down into flanged spools of such configuration that the internal surface
requiring lining is accessible from at least one of the open ends for application of lining. It is from the above concern
that the line size of Rubber Lined Piping is recommended to be 2” NPS and above.
A Rubber lined Piping System therefore is an assembly of various flanged Spools/ Fittings prefabricated to a
predetermined dimensions. The supporting system employed for Rubber Lined Piping is normally a clamp and shoe
arrangement. Welding of any support component to steel surface of the lined piping is completely prohibited. The
accessories to Rubber lined Piping include soft Rubber gasket and full threaded Fasteners.
1. DESIGN CONSIDERATIONS:


A minimum of 2” NPS line size is recommended for Rubber Lined Piping



The maximum length of straight Flanged Spools shall be as per Fig 3-A. These dimensions are decided to
allow a reasonable accessibility for lining application and to avoid any pipe to pipe welding joint within the
spool length based on Single Random Length of Steel pipe. It is logical to use straight Pipe Spools of
Standard Dimensions (i.e. the maximum recommended spool length as per Fig 3-A Standard) as far as
possible, to minimize the number of flange joints and at the same time to facilitate interchangeability of the
spools. However the last spools at the corners or branch locations of the profile (or at any location specific
situation) shall be adjusted to suit the dimension of the profile.

The straight Flanged Spools employ fixed flange at 1 end and loose flange (i.e. lap flange with stub end) at the other
end to accommodate the bolt hole rotational mismatch of the flanged fittings bolted to the straight spools.


In order to facilitate interchangeability, all flanged fittings (including Tee) shall be of a Standard Dimension
as per Fig 3. Use of flanged fittings of non-standard dimensions is however permitted (under exceptional
situations) provided they are procured as non-standard Special Parts.



For tapping of small size (i.e. Instrument / Drain-Vent Connections etc) a sandwich type Carrier Flange
with nozzle of the required size will be employed and procured as a standard Special Part.



It is likely that due to erection deviations, the prefabricated/lined chain of flanged spools may either leave
some gap or may have excess length while connecting the end terminals at site. A design solution (i.e. by
employing spacers) for such deviations is impractical and hence the spools requiring adjustment as per site
condition shall be fabricated as per actual site condition and sent for lining on a rush basis. During order
finalization a commitment on crash delivery of such spools (including material supply) will be obtained
from the Vendor. The complete activity shall be coordinated from site in consultation with Project Group.



As a contingency measure some Solid Spacers (made of Hard Rubber/ Ebonite) of predetermined
dimension are procured as standard Special Parts. These spacers can be cut into small rings at site to suit
the Gap (encountered during assembly of Rubber Lined Piping) and sandwiched between the flange joint to
fill the gap. It may however be noted that the above solid spacer can be used to fill small gaps (of the order
of 25 mm) only due to the limited strength of the Rubber. Any gap in excess of 25 mm shall be handled as
described in the earlier paragraphs.



During the design stage it may be necessary to incorporate some spacers to bridge the corner to corner
dimensions of the profile. Lined Spacers fabricated from Carbon Steel and subsequently Rubber lined are

Page 35 of 52

employed for the above purpose. As far as possible the Lined Spacer of discrete thickness of 50mm, 75mm
and 100 mm shall be used.


The Rubber Lining may obstruct the opening of flap of Sandwich type Butterfly/ Wafer Check Valve into
the pipe. In order to address the above issue the Lined Spacer (Type-1) shall be used across the Valve. The
thickness of the above spacer shall be decided as per the requirement of the valve under question.



All the straight flanged spools (including non-standard special parts) shall be assigned part no., in the
Isometric Drawings.



The supporting of Rubber Lined lines is done similar to Carbon Steel Piping with the following exceptions.

1. The lines are recommended to be supported, by employing Shoe and Clamp type supports.
2. No welding (e.g. Dummy/ Trunnion) is permitted on the Rubber Lined Piping components subsequent to lining.
2. BILL OF MATERIAL CONSIDERATIONS:
Enquiry Bill of Material:


The Enquiry BOM shall be prepared on completion of about 90% of the Isometrics for Rubber Lined
Piping.



The Pipe quantity shall be indicated in terms of the total requirement for each size based on the Isometrics



The quantity of Flanged Fittings shall be counted from the Isometrics and indicated in numbers.



The Flange quantity shall represent the requirement of Flanges on straight Pipe Spools.

The quantity of each of fixed and loose type Flanges of a particular size will be equal to the number of straight
spools of that size.


The quantity of Solid Spacers of each size is estimated based on the following equation

Q = (30 * No of Lines per size) / 500 (rounded to next number)
The above equation is based on an estimated requirement of 1 spacer (25 mm long) per line per size.


The total quantity Q of Lined Spacers for each size is estimated to be equal to the number of lines in that
size. The above total quantity is split into 3 parts as below

Spacer of 50 mm width 50% of Q
Spacers of 75mm width 25% of Q
Spacers of 100mm width 25% of Q


The requirement of non-standard Special Parts will be picked up from the Isometrics.

Page 36 of 52



Unlike other Piping Systems, no spares are included in the Bill of Material of Rubber Lined Piping unless
required as per the Contract Agreement.

Order Bill of Material:


At the ordering stage an updated Bill of Material is issued along with the Construction Isometrics for
execution purpose.



The above Bill of Material will account for only as much material as required for the Isometrics being
released for fabrication



It is expected that nearly 80% of the Isometrics would be included in the above lot.

Final Bill of Material:
The Final Bill of Material will account for the remaining 15% (i.e. 100% requirement of the Project) of the
Isometrics which will be issued along with the above BOM.
3. TECHNICAL SPECIFICATION CONSIDERATIONS:


The Vendors scope includes supply, fabrication, rubber lining, testing and delivery of rubber lined flanged
spools (including non standard special parts) as per Isometrics.



Items such as Gaskets, Fasteners, On-line Valves, Instruments, Special Parts (with the exception of nonstandard Special Parts) are excluded from the Vendor’s scope.



The Rubber Lining shall be carried out as per BS 6374.



Prior to Rubber-Lining the internal surface to be lined shall be appropriately prepared by way of grinding
excess weld deposits/sharp corners. Besides the surface shall be made free of rust/ scale by sand blasting.



The Vendor shall confirm the suitability of Rubber Material against the Fluids indicated in the Enquiry
document



In absence of specific requirement Natural Rubber shall be used



The Finished lining shall have 80 Shore D Hardness and shall be suitable for the temperature range of 45
°C to 95 °C.



A minimum of 3 mm Thick Rubber Lining shall be achieved on all surfaces.



The Rubber Lining shall be done by Vulcanizing Process under controlled temperature.



The Rubber Lined Piping items shall be tested in Accordance with BS 6374 and shall include, but not
limited to, following tests.

Visual Inspection
Peal Test

Page 37 of 52

Spark Test
Hardness Test
Flatness Test of Lined Sealing Surfaces


Outside surface of all Rubber Lined items shall be painted with 2 coats of Primer (e.g. Epoxy/ Zinc
Phosphate)



The straight Flanged Spools (including non-standard Special Parts) shall be suitably marked (Whether
Proof Marking on the Body and Punching on the Flange rim) the Part Number and the Isometric Number.



Since the Vendor is required to Quote on a Lump Sum basis it may be pertinent to get the units rates at the
time of enquiry to process the order amendment at a later date based on the final status of engineering.
Normally unit rates of following items shall be obtained for each size

Lined Pipe without Flanges
Lined Loose Flange including welding
Lined Fixed Flange including welding
Lined Branch Connection including welding
Only Lining
4. INSTALLATION CONSIDERATIONS:


The Final Grouting of the Equipment connected with Rubber Lined Piping is done only after the erection of
the connected Rubber-lined Piping.



The Rubber Lined Pieces are handled carefully to avoid damage to the lined surface.



The Flange Joints shall be tightened to the specified Torque Value by employing Torque

Wrench.


The Solid Rubber Spacer (for site adjustment) shall be machine cut as per the required thickness (a
maximum of 25mm gap). The above Solid Spacers shall not be provided near the equipment connection.



In case the gap is more than 25 mm the corrective action shall be taken by re-fabricating the pipe spool as
per the required dimension and sending it for lining.

Page 38 of 52

Fig 3: Dimensions for Lined Piping
Rubber linings are mainly used for protection against corrosion and/or erosion damage.
A wide range of rubbers and elastomers are available for lining vessels, tanks and piping.
Rubbers can also be made with anti-static properties to give a low surface electrical resistance.
Hard rubbers, i.e. hardness greater than Shore D 60, can only be applied by autoclave vulcanization, and therefore
hard rubber lining is restricted to small equipment or components. Only soft rubbers can be applied on site.
Hard rubber linings can only be applied to rigid structures and they are also sensitive to large temperature
fluctuations. Soft rubber linings remain elastic over a large temperature range, and consequently they can
accommodate major deformation, vibrations and significant temperature changes.
With respect to safety aspects, pressure rating, etc. the regulations which apply to piping, equipment and structures
are also valid for rubber-lined systems.

Page 39 of 52

Material Selection
Material selection is determined by:
- service conditions (pressure, temperature, medium, etc.)
- design
- manufacturing method
The following rubber types are used for lining purposes (classification according to ASTM D 1418):
- Isoprene or natural rubber (NR)
- Synthetic isoprene rubber (IR)
- Styrene-butadiene rubber (SBR)
- Chloroprene rubber (CR)
- Butyl rubber (IIR)
- Broom-butyl rubber (BIIR)
- Chloro-butyl rubber (CIIR)
- Nitrile-butadiene rubber (NBR)
- Ethylene propylene rubber (EP, EPDM)
- Urethane rubber (UR)
- Chlorosulphonated polyethylene (CSM)**
- Fluoro elastomer (FKM)*
* Commercially available under trade name “Viton” (DuPont product)
** Commercially available under trade name “Hypalon” (DuPont product)
Depending on the degree of vulcanization, rubbers can be classified as ‘soft’ rubber or as ‘hard’ rubber. The hardness
of soft rubbers is expressed in Shore A, and the hardness of hard rubbers is expressed in Shore D (ASTM D 2240).
Hard rubbers (or Ebonites), i.e. with a hardness higher than Shore D 60, can be produced from NR or blends, e.g.
NR/IR, NR/SBR and NR/IR/SBR.
Properties of Rubber

Page 40 of 52

Each rubber material has a specific limit in terms of allowable service temperature and chemical resistance. The
chemical resistance and temperature limits for continuous service of several rubber types are given below.
1. Natural rubber (NR)
Soft and hard natural rubber linings are suitable for handling most inorganic chemicals, with the exception of strong
oxidising agents such as chromic and nitric acids. Natural rubber linings are also suitable for handling hydrochloric
acid. Natural rubber is also resistant to most organic fluids, including alcohols and most esters. They should not be
used in the presence of aliphatic or aromatic hydrocarbons, halogenated hydrocarbons, mineral oils and certain
vegetable oils. The allowable service temperature range is -40 °C to +80 °C.
The bond strength of NR linings on steel is excellent. The hardness is typically Shore A 55 for soft rubber and Shore
D 75 for hard natural rubber.
2. Synthetic isoprene rubber (IR)
Isoprene rubber is a synthetic alternative form of NR, and has similar properties.
3. Styrene-butadiene rubber (SBR)
Styrene-butadiene rubber can be used for the containment of automotive brake fluids, alcohols and mixtures of
alcohol and water. The allowable service temperature range is -30 °C to +80 °C. The hardness is in the same range
as that of soft natural rubber (NR).
4. Chloroprene rubber (CR)
Chloroprene rubber is resistant to ozone and sunlight, and reasonably resistant to oils and chlorine. Special
compounds are suitable for use with refrigerants (e.g. Freon 12 and 22).
The allowable service temperature range is -30 °C to +105 °C. Hardness is approximately Shore A 60.
5. Butyl rubbers (IIR, BIIR, CIIR)
Butyl rubbers have excellent tolerance to hydrochloric acid. Butyl rubber is resistant to ozone and sunlight, nonflammable hydraulic fluids, animal and vegetable oils, water, alcohols, ketones and acids. Butyl rubber should not
be used in the presence of free halogens, petroleum oils or halogenated or aromatic hydrocarbons. The allowable
service temperature range is -30 °C to +110 °C. Hardness is in the range of Shore A 55 to A 60.
6. Nitrile butadiene rubber (NBR)
Nitrile butadiene rubber (also known as BuNa-N) is a copolymer of butadiene and acrylonitrile. The acrylonitrile
content must be at least 35% by mole to obtain good chemical resistance. Nitrile rubbers are resistant to petroleumbased hydraulic and lubricating oils, animal and vegetable oils, acetylene, alcohols, water, alkalis and fuel oils.
Nitrile rubber should not be used for phenols, ketones, acetic acids, most aromatic hydrocarbons and nitrogen
derivatives. The allowable service temperature is -35 °C to +80 °C. Hardness is approximately Shore A 60.
7. Ethylene propylene rubbers (EPDM / EPM)
Ethylene propylene rubbers are resistant to ozone and sunlight, oxidizing chemicals, non-flammable hydraulic
fluids, pure aniline, fire extinguisher liquids, acids, hot water and steam. However, these rubbers are not resistant to
mineral oils, petrol solvents and aromatic hydrocarbons. The allowable service temperature range is -40 °C to +150
°C. Hardness is typically in the range Shore A 40 to A 80.

Page 41 of 52

8. Urethane rubber (UR)
Urethane rubber has excellent wear/erosion resistance and is chemically resistant to mineral oils, fuels and ozone.
Urethane rubber should not be used for concentrated acids, ketones or chlorinated hydrocarbons, and shall not be
used for water above 50 °C.
Otherwise, the allowable service temperature range is -40 °C to +70 °C. Hardness is typically in the range Shore A
50 to A 80.
9. Chlorosulphonated polyethylene (CSM)
Chlorosulphonated polyethylene is a highly wear-resistant synthetic rubber with excellent resistance to heat, ozone
sunlight, oxidising media, sodium hypochlorite and sulphuric acid.
CSM rubber has also good resistance to most oils, lubricants and aliphatic hydrocarbons, but is unsuitable for use
with esters and ketones. The allowable service temperature range is -35 °C to +80 °C. Hardness is approximately
Shore A 60.
10. Fluoro-elastomers (FKM)
Fluoro-elastomers are copolymers of hexa-fluoro-propylene and vinyldiene fluoride. They are suitable for both hightemperature and vacuum applications. These materials have excellent resistance to oils, fuels, lubricants, carbon
tetrachloride, most concentrated acids and many aliphatic and aromatic hydrocarbons such as toluenes, benzene and
xylene.
They should not, however, be used with low molecular weight esters and ethers, ketones, certain amines and hot
anhydrous hydrofluoric or chlorosulphonic acids. These materials are also resistant to ozone and sunlight and can be
used in contact with many corrosive gases, e.g. bromine and chlorine. However, they are not resistant to ammonia or
highpressure steam. The allowable service temperature range is -20 °C to +230 °C. Hardness is typically in the range
Shore A 60 to A 90.
Reducers used in Piping Industry: A short literature
Pipelines are not of uniform size and there is requirement of reducing or expanding the lines depending on process
requirement or availability of material. Here comes the importance of a special pipe fitting called Reducers.
Reducers are most extensively used in piping industry to reduce or expand the straight part of run pipe. Basically,
reducers are available in two styles:


Concentric reducers and



Eccentric reducers.

Concentric Reducers:
As shown in Fig. 1. In this type of reducers area reduction is concentric and center line of the pipe on bigger end and
smaller end remains same. These styles are normally used for vertical lines.

Page 42 of 52

Fig.1: Concentric Reducers
Eccentric Reducers:
As shown in Fig. 2 , in this style of reducer there is an offset in between the center lines of bigger end and center line
of smaller end. This offset or eccentricity will maintain a flat side either on top or on bottom side.

Fig.2: Eccentric Reducer
This offset or eccentricity can easily be found out by the following equation:
Eccentricity=(Bigger end ID-Smaller end ID)/2
While using this type of reducer the user has the option of orienting the flat side. Usually for horizontal lines,
eccentric reducers are oriented with either the flat side up or down and the same with deviation is mentioned in
isometric.
Normally eccentric reducers with flat side down are preferred for following cases on horizontal lines:
• On Sleepers and Piperacks
• On lines requiring gravity flow
• On pump suction line which handle slurry.

Page 43 of 52

Eccentric reducers with flat side up are used for all pump suction lines (excluding pumps handling slurry) on
horizontal lines. This way one can avoid air getting trapped inside the pipeline during initial venting through pump
casing and will help in avoiding Cavitation.
Depending on end connections of this fitting with straight pipe, reducers are grouped as follows:
Butt Welding reducers: The applicable pressure rating, dimensional and material standards for butt welding
reducers are same as those applicable to butt welding elbows.
Socket welding reducers: As shown in Fig.3. such reducers are available in concentric type only & in the form of a
coupling with one end socket to fit larger diameter pipe and other end socket to fit smaller diameter pipe. Standards
are same as those applicable to socket welding elbows.

Fig.3: Socket Welded Reducers
Screwed reducers: Available only in concentric type and are in the form of coupling having one end to fit bigger
pipe and other end to fit smaller pipe. ASME B16.11 is applicable dimensional standard. Material standards
including pressure ratings are same as of screwed elbows.
Flanged reducers: Their pressure rating, use, material and dimensional standards are same as those applicable
to flanged elbows. Regardless of reduction their face to face dimensions are governed by the larger pipe size.

Page 44 of 52

Design Guidelines for PE & ROTO Lined
Carbon Steel Piping
Carbon steel piping with internal PE / ROTO lining is used for liquid service with high chloride
as well as higher oxygen content. The maximum operating temperature of the PE & ROTO
lined piping is 60 °C. Also, these types of coatings are suitable for gas-liquid ratio values
upto 300.
A PE liner consists of a number of Polyethylene pipe lengths, which are fused together and
inserted into sections of carbon steel pipelines and flowlines. The Carbon Steel pipe provides
the pressure containment; while the PE liner provides corrosion protection. At the ends of the
sections, the liners are terminated by PE stub ends. Connections between PE lined carbon
steel pipes shall be flanged.
The PE & ROTO lining is carried out only after the pipe spools are fabricated & hydrotested.
No welding is allowed on the pipe spool once the PE or ROTO lining is done. The pipe
trunnion member & line stop members, if applicable, shall be welded prior to the lining.
Hydrotesting of the spool or pipelines is done before the lining & after the lining also.
Therefore, gaskets are required to be considered for each flanged joint for hydrotest
purpose.
The requirements to be considered while designing of PE lined piping are mentioned below:
PE/ROTO lining dimensional limitations:
The longest continuous length of liner, which can be installed in straight pipe, depends on
diameter and wall thickness, but is generally reduced in practice by local curvature of the
line.
For off plot piping scope the PE lining can be done for a pipe spool of upto 250m length. For
shop lined piping the maximum length of PE lined pipe spool is kept as 18m because of the
transportation limitations. Minimum pipe spool length requirement is 5m (can be as less as
2m if agreed with PE lining vendor). PE lining can be done only for straight pipe spools. It can
not be done for pipe spools with reducers or branches. In such cases (for pipe spools with
reducers or branches) rotolining is carried out .
Bends for PE lining shall not be less than 20D radius (recommended radius is 40D wherever
possible). PE or ROTO lining cannot be carried out for pipe spools with orifice flanges
because of the small size orifice flange tapings. In this case, one option is to use a suitable
material for the upstream & downstream pipe spools & the orifice flanges. And the other
option is to use carrier rings with orifice tapings & orifice plate of the suitable material which
will get sandwiched between two PE lined flanges which avoids the use of expensive
material for the upstream & downstream pipe spools.
Annulus Vents:

Page 45 of 52

Every PE lined pipe spool shall have vent points. The minimum number of vent points shall
be one on each flanged end of a section of lined pipe. The vent points to be provided with
valves for oil & gas application & without valves for water service application. The valves
shall be opened only for venting purpose. Continuous venting is not permitted. The purpose
of venting is as follows.


To vent the (ambient) gas from the pipe/annulus during installation.



To vent the permeated fluids accumulated in the annulus to prevent collapse.



To allow monitoring of the integrity of the PE liner during the service life.

Vent holes shall be designed such that no extrusion of the PE liner will occur. For larger
diameter lines, vent discs with multiple holes or wire screens may be used. Vent holes shall
not be larger than 3 mm in diameter. All vents shall be valved (except for water service
where vents can be plugged) and shall have a “snorkel” to prevent ingress of dirt, moisture
and/or air.
The design of the vent point assembly shall be agreed with the Company.
Design Guidelines for ROTO Lined Piping:
Rotolining is a method of lining the inside of pipes or other parts with a seamless, one piece
inner layer of plastic. In this lining technique the lined spool is produced by heating and
rotating a carbon steel spool with a polymer, which is in a granular form, placed inside the
pipe spool. The polymer melts and forms a liner on the internal surface of the carbon steel
pipe. Also, the polymer forms a bond with the metal.
The choice of which polymer to use is based on the chemical resistance properties that are
required of the final part. Polyethylene, Polypropylene, PVDF or number of other polymers is
used for rotolining
application. The lining thickness varies from 2 mm to 8 mm. The heavy lining thickness
allows post machining of critical surfaces that would not be possible with a thinner lining
applied by other methods. Virtually any type of metal weldment or casting can be rotolined.
Typical items that can be rotolined are tanks, carbon steel pipes, fittings, and complex
welded structures.
Rotolining Procedure:


The rotolining process comprises placing a polymer having an average particle size of
70-1000 μm containing a melt processible fluoropolymer, in a cylindrical article to be
lined (the powder being present in sufficient amount to make a lining at least 500 μm
thick).



The cylindrical article is rotated to bring the radial acceleration at the substrate
surface to be coated to 100 m/sec2 or greater, pressing the powder against the article to
be lined by means of the centrifugal force generated by that rotation, at the same time
heating the melt processible fluoropolymer to a temperature equal to or higher than the
melting point of the melt processible fluoropolymer, but not higher than 400° C., thereby
adhering the melt processible fluoropolymer to the surface of the article to be lined.

Page 46 of 52



During the heating cycle, the polymer particles begin to stick to the hot metal
substrate. A skin is formed. This skin gradually forms a homogenous layer of uniform
thickness. Ultimate wall thickness is determined by the amount of material that is initially
placed into the cavity.



Adding a small amount of a heat stabilizer such as PPS (polyphenylene sulphide) to
prevent the decomposition of the fluoropolymer on heating can give an excellent coating
with minimal bubble formation.



After a predetermined time at a specific temperature, the entire polymer is
distributed over the surface of the spool. The spool is then cooled by a combination of
forced air and water mist.



The part is then removed from the machine and surfaces such as flange face and “O”
ring sealing areas are machined into the plastic. Linings are spark and ultrasonically
tested to insure liner integrity.



The process itself introduces no force or shear to the material. The result is a
relatively stress free lining. Rotolined parts are completely seamless and weld free.

Advantages of ROTOLINING:


Seamless construction with a very smooth interior surface.



Polymer rotolining have an excellent chemical resistant, relatively high temperature
performance and an excellent metal to plastic bond.



Thicker lining & uniform wall thickness can be achieved than electrostatic or spray
coating.



Drastically reduces permeation through the coating and possible corrosion of the
metal substrate.



Thicker coating can be repaired by welding if mechanically damaged. Thin coatings
must be stripped and recoated, if repairs are not possible.

ROTO lining dimensional limitations:
Guidelines for ROTO lining dimensional limitations are as per below table:

Page 47 of 52

Rotolining Limitations

Rotolining Dimensional table

All dimensional given in above table shall be considered as diagonal lengths. The above
dimensions shall be verified with the ROTO lining contractor prior to issuing the isometrics
for fabrication.

Page 48 of 52

For ROTO lining minimum branch-off size shall be 1” NB.
The thickness of PE & ROTO lining on the flange raised face (collar thickness) is as per below
Table:

Flange Collar thickness

The above thicknesses shall be verified with the PE & ROTO lining contractors prior to
issuing piping isometric drawings for construction.
Flange joint details for PE / ROTO lining piping:
Typical PE / ROTO lined flange joint detail is as follows:

Page 49 of 52

Typical Flanged joint

The 1/2” NB annulus vents shown in the above sketch are for PE lined pipe spool only.
Galvanised carbon steel retainer rings are used between PE / ROTO lined flange joints to
hold the stub ends in place (to avoid the plastic material from deformation). The width of
retainer ring is calculated as follows:
A = (2 x B + 2 x T) – 3mm
Where,
A – Width of retainer ring
B – Thickness of flange raised face
T – Collar thickness
Retainer rings are generally provided by PE lining vendor, still it has to be confirmed with the
vendor at the start of the project.
Following sketches provides the information regarding the use of retainer ring & insulating
gasket for PE & ROTO lining flange joints.

Page 50 of 52

Flanged joints

The use of insulating gasket for PE & ROTO lining piping is restricted for the insulating spools
only wherever shown in PEFS. For flange joint between PE / ROTO lined CS piping & SS or
DSS mating flange insulating gasket is not required to be provided.
For insulating joint insulating gasket, extra long sleeves, washers & extra long bolts are
required. The spectacle blind, spade & spacers shall be considered of suitable material for PE
& ROTO lined piping and the blind flange shall be epoxy coated or ROTO lined. This shall be
finalized with the client & construction contractor prior to start of a project.
A typical isometric of PE/Rotolined pipe is shown below:

Page 51 of 52

Typical isometric drawing

Page 52 of 52