CHEMICAL CLEANING OF CARBON STEEL PIPING SYSTEMS

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Specification No 1652109-8.0

Info No 300969

POWER PLANT SPECIFICATION SUBJECT: CHEMICAL CLEANING OF CARBON STEEL PIPING SYSTEMS Author : TMO

Date: 950710

Approved: TKS

Page:

1/8

General This specification deals with the chemical cleaning of the carbon steel piping systems. The piping systems mentioned in this specification are indicated in the Line List, referring to this specification. Prior to the chemical cleaning of the piping systems, pressure testing and mechanical cleaning has to be executed. The piping systems have to be completely cleaned from grease and oil. When cleaning the piping systems chemically, the pipe section is exposed to an acid solution. During the reaction between the acid and the surface of the pipe material, the surface is cleaned from all remnants of rolling skin, oxidations etc. left over from the mechanical cleaning. This treatment is also known as pickling. After the pickling the pipe section is treated with a phosphate solution which provides the pipes with a phosphate layer giving a short time protection against oxidation. When the chemical cleaning is executed, the internal of the pipe section is completely cleaned, and only the metallic surface of the base material must be visible. The purpose of chemical cleaning is to protect the delicate components of the GenSet from particles, which may cause damage or reduce the time of operation of the components and the GenSet. The chemical cleaning of the piping systems is normally used when the demand for cleanliness is higher that it is possible to obtain by mechanical cleaning. Normally, the chemical cleaning is followed by a flushing of the piping systems. (Flushing specifications are not described in this specification). The chemical cleaning of the piping systems has to be carried out in accordance with the guidelines of the MBD-H supervisor. The chemical cleaning will not be accepted without an approval from the MBD-H supervisor.

Specification No 1652109-8.0

Info No 300969

POWER PLANT SPECIFICATION SUBJECT: CHEMICAL CLEANING OF CARBON STEEL PIPING SYSTEMS Author : TMO

Date: 950710

Approved: TKS

Page:

2/8

Methods of Chemical Cleaning The chemical cleaning of the piping systems can be executed according to: A.

a conventional treatment sequence of acid bath - water bath - lye bath. Short description: Conventional and aggressive, but "easy to get" chemicals are used. The execution of the treatment requires open baths for the chemical solutions and heating-up facilities for the phosphate solution. Further, the method requires a great deal of manual work, and therefore, there must be paid great attention to the safety precautions.

B.

an alternative treatment with simultaneously pickling and phosphatizing. Short description: Sophisticated, but non-aggressive and non-polluting chemicals are used. The execution of the treatment requires a vessel and a pump. No heating-up facilities are necessary. Compared to method A the need for manual workforce and safety precautions is very reduced.

With respect to the quality of the chemical cleaning, there should be no difference whether method A or method B is executed.

Specification No 1652109-8.0

Info No 300969

POWER PLANT SPECIFICATION SUBJECT: CHEMICAL CLEANING OF CARBON STEEL PIPING SYSTEMS Author : TMO

Date: 950710

Approved: TKS

Page:

3/8

Execution of Work Method A - Conventional Treatment Preparation of the Piping System The piping system in question has to be dismantled in each flange connection. All components, valves, filters, pumps etc. are not to be included in this cleaning operation, but have to be checked, and if necessary, carefully cleaned. All components are to be sealed and preserved. Preparation of the Hydrochloric Acid Bath The hydrochloric acid (HCL) is commercially available with a concentration of 3133% and an arsenic content of less than 1%. The solution is prepared by mixing the hydrochloride acid with clean potable water. Mixing ration of the hydrochloric bath HCL : H2O = 3 : 2 (parts by weight). CAUTION: Pour the acid into the water and never vice versa! The temperature of the bath must not be below 20°C. Preparation of the Water Bath A bath with clean potable water must be prepared. Preparation of the Lye Baths The lye solution is prepared by mixing trisodium phosphate (Na3PO4) with clean potable water. Mixing ration of the lye bath Na3PO4 : H2O = 1 : 8 (parts by weight) The treatment temperature must be 80°C. A heating-up device must be installed in the lye bath.

Specification No 1652109-8.0

Info No 300969

POWER PLANT SPECIFICATION SUBJECT: CHEMICAL CLEANING OF CARBON STEEL PIPING SYSTEMS Author : TMO

Date: 950710

Approved: TKS

Page:

4/8

Method A - Conventional Treatment........(continued) Safety Precautions At hydrochloric acid baths and the lye baths, the fumes must be exhausted by ventilators and led out into the open. Attention has to be paid to the local safety and precaution regulations. In compliance with the safety and precaution regulations on handling acids and lyes, every person carrying out acid and lye treatment has to wear acid-resistant clothing, rubber boots, rubber gloves and goggles. A connected water hose always has to be kept ready for flushing and neutralizing in case of accidents. Treatment of the Pipes The dismantled pipe sections are put into the hydrochloric acid bath for the pickling treatment. Attention has to be paid that no pockets of air inside the pipe section are present. The duration of the treatment has to be determined by visual appraisal. If any threads already have been made in the pipes, it is necessary to ensure that the tip of the threads does not sustain damage. The duration of the treatment has to be reduced accordingly. After completion of the pickling process, the acid solution still adhering to the pipes must be washed of in the water bath. The pipes are then put into the lye bath. Any further remnants of the acid solution still left in the scores and pores of the superficial structure will be neutralized in the lye bath. In the lye bath the pipes are provided with a phosphate layer, giving a short time protection against oxidation. As for the acid bath there must be no pockets of air inside the pipe section during this operation. The duration of the lye bath treatment is approximately 2 minutes. After the lye bath treatment the pipe section are flushed with clean potable water to remove any remnants of the lye. Hereafter, the pipe sections have to be dried, if possible, by letting clean compressed air through the pipe section. The chemical solutions can be used for several treatments of pipe sections. When the solutions start to “run down”, the duration of the treatments has to be increased accordingly.

Specification No 1652109-8.0

Info No 300969

POWER PLANT SPECIFICATION SUBJECT: CHEMICAL CLEANING OF CARBON STEEL PIPING SYSTEMS Author : TMO

Date: 950710

Approved: TKS

Page:

5/8

Method A - Conventional Treatment........(continued) Sealing and Protection of Cleaned Pipe Sections If quite some time elapses between the chemical cleaning and the mounting of the piping system, the pipe section must be preserved, and the ends must be closed. For this purpose plugs or caps in vivid colors are the most suitable as they will not be overlooked, when mounting. Disposal of Chemicals Prior to disposal of the hydrochloride acid bath, the solution has to be neutralized. For this purpose sodium hydroxide (NaOH) is suitable. By mixing the two chemicals in the right quantities, the solution turns into salt water. HCl + NaOH = NaCl + H2O The solution is neutralized when the pH value is 7, or when the litmus paper does not change color when dipped in the solution. When neutralized, the solution can be led to the normal sewerage. ATTENTION: Disposal of chemicals must be according to the local or national safety and pre- caution regulations. The trisodium phosphate solution is to be neutralized with liberally amounts of water. At normal conditions the solution then can be led to the sewerage. ATTENTION: Disposal of chemicals must be according to the local or national safety and pre-caution regulations.

Specification No 1652109-8.0

Info No 300969

POWER PLANT SPECIFICATION SUBJECT: CHEMICAL CLEANING OF CARBON STEEL PIPING SYSTEMS Author : TMO

Date: 950710

Approved: TKS

Page:

6/8

Method B - Alternative Treatment Preparation of the Piping System The chemicals used for the alternative treatment are only aggressive to oxidations. On normal conditions there is therefore no risk of corrosion or pitting of the painting, rubber, packings, valve sealings etc. during the treatment. The piping system in question is to be dismantled in each flange connection. All components, valves, filters, pumps etc. are, if possible, not to be included in this cleaning operation, but are to be checked, and if necessary, carefully cleaned. All components are to be sealed and preserved. The chemicals have to be circulated through the pipe sections by a pumping unit. A suitable amount of pipe sections has to be assembled to form one single pipeline. As absolutely no pockets of air are allowed during the treatment, it is of great importance that the single pipeline is assembled in a way that ensures the escape of the air from the inside of the piping. The best way to let the air escape, is to arrange the single pipeline with continuously slope. The pumping unit is consisting of an open vessel, with a volume capacity of approximately 2 times the volume of the single pipeline. The vessel is connected to a centrifugal pump. From here, the pump is connected to the lowest end of the single pipeline. The other end of the single pipeline is connected to the top of the vessel. The chemical is pumped from the vessel via the pump and through the single pipeline. Hoses of plastic or similar are suitable for the connections between the pumping unit and the single pipeline. A filter has to be installed between the vessel and the pump. In front of the pump a non-return valve has to be installed. The vessel has to be equipped with a drain and shut of valves at all connections. Treatment of the Pipes, Degreasing Prior to the pickling treatment, the piping system has to be completely cleaned from oil and grease. For that purpose the chemical WS50 is used. The chemical WS50 is poured into the open vessel and mixed with clean potable water. All the shutoff valves on the vessel have to be closed. The WS50 chemical is mixed with water to a 0.5% solution. The temperature of the solution should not be below 10°C.

Specification No 1652109-8.0

Info No 300969

POWER PLANT SPECIFICATION SUBJECT: CHEMICAL CLEANING OF CARBON STEEL PIPING SYSTEMS Author : TMO

Date: 950710

Approved: TKS

Page:

7/8

Method B - Alternative Treatment........(continued) The chemical solution is mixed in the vessel, the shutoff valves are opened, and the pump is turned on. The solution is now circulated until the single pipeline is completely filled and there are absolutely no air pockets in the system. Duration: Approximately ½ hour. The WS50 solution is drained from the piping system and the vessel. The system has to be filled with clean potable water and flushed for about 10 minutes. When the water flushing is executed, the water is drained from the system. Treatment of the Pipes, Pickling After the degreasing the pickling can begin. The chemical VH Deruster is poured into the open vessel and mixed with clean potable water. All the shutoff valves on the vessel have to be closed. The VH Deruster chemical is mixed with water to a 5% solution. The temperature of the solution should not be below 10oC. When the chemical solution is mixed in the vessel, the shutoff valves are opened, and the pump is turned on. The solution is now circulated until the single pipeline is completely filled, and there are absolutely no air pockets in the system. Duration: Approximately ½ hour. The pump is turned off, and the shutoff valves on the vessel are closed. The chemical solution has to rest in the piping for 5-6 hours. Then the shutoff valves are opened, and the pump is turned on. The solution has to be circulated again for ½ hour. The pump is turned off, and the shutoff valves closed. Again, the chemical solution has to rest inside the piping for about 5-6 hours. After the resting period the piping is inspected. If further treatment is necessary, the above described procedure is repeated. If not, the chemical solution is drained from the vessel and the single pipeline. The solution cannot be reused. The vessel is filled with clean potable water, and the single pipeline is flushed by using the pump. If necessary, the water flushing is repeated until all the chemical remnants have been removed. After completion of the treatment the single pipeline has to be dismantled and dried by letting clean compressed air, or if possible, nitrogen through the pipe section.

Specification No 1652109-8.0

Info No 300969

POWER PLANT SPECIFICATION SUBJECT: CHEMICAL CLEANING OF CARBON STEEL PIPING SYSTEMS Author : TMO

Date: 950710

Approved: TKS

Page:

8/8

Method B - Alternative Treatment........(continued) Sealing and Protection of Cleaned Pipe Sections If quite some time elapses between the chemical cleaning and the mounting of the piping system, the pipe section must be preserved and the ends must be closed. For this purpose plugs or caps in vivid colors are the most suitable as they will not be overlooked, when mounting. Disposal of Chemicals Both the chemical solutions of the WS50 and the VH Deruster pH neutral are nonpoisonous. The solutions can be led into the normal sewerage. ATTENTION: Disposal of chemicals must be according to the local or national safety and precaution regulations.

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