Loop Test Procedure
Content
5.1.1 1.
Loop Test Procedure
Common Procedure Before the loop test or sequence test is conducted, all instruments related shall be calibrated, this can be seen from the instrument label. The final loop test shall be performed to ensure that the installed instrumentations are functionally correct. Each transmitter and switch should not be recalibrated during the loop test, since all transmitter and switches are installed after finished the workshop calibration. 2. When performing tests, two groups will be required, one in the field and other in the control room. The contractor is required to provide proper communication for all involved in test verification, i.e. field radios or walkie talkies approved by appropriate Indonesian radio frequency Government agency. 3. Adequate skilled manpower and technically/ organizationally skilled supervision is required to provide proper test and meet the time schedule of the job. In most instances COMPANY and/or CONTRACTOR representative will witness the entire test and countersign the test report. Should any of the tests not be witnessed, CONTRACTOR can proceed the test by him selves under the confirmation of COMPANY’s acceptance. 4. Associated alarms and trip actions of DCS/PLC and/or board-mounted instruments shall be checked during the loop test. When particular loop ties into DCS/PLC system, a technician may be required in the rack room for troubleshooting. 5. Where interlock inputs have already been proven during loop tests, these inputs may be by passed. One of the inputs to a given interlock will be tested to prove entire loop. All other inputs shall be proven at the sequence test. 6. Where interlock inputs and/or outputs are associated with electrical equipment such as motors for pumps, compressors and valves, the sequence test shall be carried out in conjunction with the mechanical and electrical discipline to insure protection to equipment. 7. Tests are essentially functional and if an inoperative or badly calibrated or otherwise unsatisfactory test result is encountered, all results for that loop should be considered null and void. The relevant earlier tests shall be repeated, as necessary, after rework, replacement or repair. The test shall then be completely repeated for that particular loop. Loop Test Procedure
1.
Prior to performing loop verification, check the entire loop to ensure all wires and tubing are connected. Check for proper voltages and set instrument air pressure to the recommended manufacturer’s requirements.
2.
For testing the loop, set air and/or electrical supplies where appropriate. IN particular, the air supply pressure for control valves and the other pneumatic actuators to be checked that they are set correctly in accordance with the specifications.
3.
For electronic loops, check polarities and measure loop impedance in advance, where necessary. Prior to conducting the loop test, DCS shall be de-energized and confirm that all field cables are properly connected. Then DCS shall be energized again.
4.
The final loop test shall be performed to ensure that the installed instrumentation are functionally correct. Each transmitter and switch should not be recalibrated during the loop test, since all transmitter and switches are installed after finished the work shop calibration.
5.
If a transmitter exist in a loop, the output signals equivalent to 0%, 50% and 100% of the instrument range shall be generated manual (dummy signals) to check the function of the loop, such the way the varying zero adjustment of electronic transmitters or connecting DC standard current generator or holding nozzle and flapper on pilot of pneumatic transmitters.
6.
Connect a precision known source to the primary field transmitter. A simulation of the measured variable is applied to the transmitter for zero, mid scale and full scale reading, according to the manufacturer’s recommended instructions. Observe on the PLC system’s, that the indication shows as being simulated. Also observe on the MMI (Man Machine Interface) screens on the PC. It must indicate proper actions on Display and Alarm Screens
7.
If a local mounted controller exist in a loop, the signal for checking the valve operation to be generated manually using the manual operation device on the controller prior to the automatic operation check. Automatic operation check to be conducted by changing the controller's set point.
8.
Control Loop: Place the controller in the manual mode and simulate a process variable signal from 0%, 25%, 50%, 75% and 100% of scale and observe on the monitor that the process variable indication shows as simulated signals. Return process variable to 0%, put the controller in the automatic mode, place P.B. at 100%, reset time and derivative to
minimum setting with set point at 50% and ensure that controller is in direct action. Simulate process variable signal 0%, 25%, 50%, 75% and 100%, observe and record all findings 9. For pressure switch and level switch loops, their contact to be manually make and/or break for ensuring the corresponding instrument's responses. 10. For thermocouple loops, check the burn-out features by disconnecting wires, and confirm that the polarity of thermocouple extension wires is maintained when re-connected. For assisting the identification of thermocouple extension wires, the following guide is given. (1) Negative extension wires is always colored as red as per ANSI C96.1.
(2)
For type K thermocouple (Chromel / alumel), the negative wire is slightly magnetic. It has a lower resistance in ohms/foot for the same size wire.
(3) For type R thermocouple (Copper/copper-Nickel Alloy), the negative wires softer than the positive wire. 11. For resistance temperature detector (RTD) loops, check the function of all instrument and control valve(s) in the loop by connecting the resistance approximately 120 ohm at the terminal heads, and visually check the correct connections when close the terminal heads. 12. Analytical and Special Installations shall be checked according to manufacturer's instruction and/or by agreement with owner's and/or Contractor's engineer.
13. During
loop testing, the following items shall generally be confirmed or
checked : (1) In control room or at the local panel : Indication and output signal level on the Indication of trend recorders associated Function of flow counters Function of annunciators Action of controllers of DCS or DCS console or board mounted instruments with DCS (2) In the Field :
conventional type instruments
-
Action
of
control
valves
including
associated accessories, such as solenoid valves, limit switches, etc.
gauges
Range of transmitter Indication of remote mounted output
14. The test report form is shown in Table 1 (sheet). Sequence Test Procedure
1.
Prior to sequence test, CONTRACTOR will request COMPANY to
approve sequence and timing flow diagram provided by CONTRACTOR. This approval is to ensure that there will be no change in sequence test during commissioning. CONTRACTOR shall supply approved cause and effect 2. diagrams including the sequence and timing diagrams to COMPANY. Complete interlock system shall be checked for correct sequence of operation and all interlock systems shall be checked for “fail safe” operation. 3. 4. Start-up bypass and maintenance override switches shall generally Where interlock inputs and/or outputs are associated with electrical be "OFF" prior to sequence. equipment, such as motors for pump, compressors and, valves, the sequence test shall be carried out in conjunction with the related section engineer 5. For initiators, manual output signals will be required to generate in lieu of transmitter signals or contacts will be required to make and/or break manually to check the annunciators. Function check will not be necessary, since it should be finished during loop test. 6. For inputs devices, signal generator output will be required to provide analog signal or pulse in lieu of transmitters signals. Contact activation will be required to make and/or break manually to provide digital signal. Function check will not be necessary, since it should be finished during loop test. 7. For output devices, pushing manual trip buttons or making emergency conditions will be required as same manner as checking the initiators correctly. At the same time, answer back shall be checked, where necessary.
8.
For remote pneumatic or motor operated valves, manual switches
or DCS operation key board switches shall be on and/or of to check the valve shall be switched to remote position prior to test.
Loop Test Procedure
Common Procedure Before the loop test or sequence test is conducted, all instruments related shall be calibrated, this can be seen from the instrument label. The final loop test shall be performed to ensure that the installed instrumentations are functionally correct. Each transmitter and switch should not be recalibrated during the loop test, since all transmitter and switches are installed after finished the workshop calibration. 2. When performing tests, two groups will be required, one in the field and other in the control room. The contractor is required to provide proper communication for all involved in test verification, i.e. field radios or walkie talkies approved by appropriate Indonesian radio frequency Government agency. 3. Adequate skilled manpower and technically/ organizationally skilled supervision is required to provide proper test and meet the time schedule of the job. In most instances COMPANY and/or CONTRACTOR representative will witness the entire test and countersign the test report. Should any of the tests not be witnessed, CONTRACTOR can proceed the test by him selves under the confirmation of COMPANY’s acceptance. 4. Associated alarms and trip actions of DCS/PLC and/or board-mounted instruments shall be checked during the loop test. When particular loop ties into DCS/PLC system, a technician may be required in the rack room for troubleshooting. 5. Where interlock inputs have already been proven during loop tests, these inputs may be by passed. One of the inputs to a given interlock will be tested to prove entire loop. All other inputs shall be proven at the sequence test. 6. Where interlock inputs and/or outputs are associated with electrical equipment such as motors for pumps, compressors and valves, the sequence test shall be carried out in conjunction with the mechanical and electrical discipline to insure protection to equipment. 7. Tests are essentially functional and if an inoperative or badly calibrated or otherwise unsatisfactory test result is encountered, all results for that loop should be considered null and void. The relevant earlier tests shall be repeated, as necessary, after rework, replacement or repair. The test shall then be completely repeated for that particular loop. Loop Test Procedure
1.
Prior to performing loop verification, check the entire loop to ensure all wires and tubing are connected. Check for proper voltages and set instrument air pressure to the recommended manufacturer’s requirements.
2.
For testing the loop, set air and/or electrical supplies where appropriate. IN particular, the air supply pressure for control valves and the other pneumatic actuators to be checked that they are set correctly in accordance with the specifications.
3.
For electronic loops, check polarities and measure loop impedance in advance, where necessary. Prior to conducting the loop test, DCS shall be de-energized and confirm that all field cables are properly connected. Then DCS shall be energized again.
4.
The final loop test shall be performed to ensure that the installed instrumentation are functionally correct. Each transmitter and switch should not be recalibrated during the loop test, since all transmitter and switches are installed after finished the work shop calibration.
5.
If a transmitter exist in a loop, the output signals equivalent to 0%, 50% and 100% of the instrument range shall be generated manual (dummy signals) to check the function of the loop, such the way the varying zero adjustment of electronic transmitters or connecting DC standard current generator or holding nozzle and flapper on pilot of pneumatic transmitters.
6.
Connect a precision known source to the primary field transmitter. A simulation of the measured variable is applied to the transmitter for zero, mid scale and full scale reading, according to the manufacturer’s recommended instructions. Observe on the PLC system’s, that the indication shows as being simulated. Also observe on the MMI (Man Machine Interface) screens on the PC. It must indicate proper actions on Display and Alarm Screens
7.
If a local mounted controller exist in a loop, the signal for checking the valve operation to be generated manually using the manual operation device on the controller prior to the automatic operation check. Automatic operation check to be conducted by changing the controller's set point.
8.
Control Loop: Place the controller in the manual mode and simulate a process variable signal from 0%, 25%, 50%, 75% and 100% of scale and observe on the monitor that the process variable indication shows as simulated signals. Return process variable to 0%, put the controller in the automatic mode, place P.B. at 100%, reset time and derivative to
minimum setting with set point at 50% and ensure that controller is in direct action. Simulate process variable signal 0%, 25%, 50%, 75% and 100%, observe and record all findings 9. For pressure switch and level switch loops, their contact to be manually make and/or break for ensuring the corresponding instrument's responses. 10. For thermocouple loops, check the burn-out features by disconnecting wires, and confirm that the polarity of thermocouple extension wires is maintained when re-connected. For assisting the identification of thermocouple extension wires, the following guide is given. (1) Negative extension wires is always colored as red as per ANSI C96.1.
(2)
For type K thermocouple (Chromel / alumel), the negative wire is slightly magnetic. It has a lower resistance in ohms/foot for the same size wire.
(3) For type R thermocouple (Copper/copper-Nickel Alloy), the negative wires softer than the positive wire. 11. For resistance temperature detector (RTD) loops, check the function of all instrument and control valve(s) in the loop by connecting the resistance approximately 120 ohm at the terminal heads, and visually check the correct connections when close the terminal heads. 12. Analytical and Special Installations shall be checked according to manufacturer's instruction and/or by agreement with owner's and/or Contractor's engineer.
13. During
loop testing, the following items shall generally be confirmed or
checked : (1) In control room or at the local panel : Indication and output signal level on the Indication of trend recorders associated Function of flow counters Function of annunciators Action of controllers of DCS or DCS console or board mounted instruments with DCS (2) In the Field :
conventional type instruments
-
Action
of
control
valves
including
associated accessories, such as solenoid valves, limit switches, etc.
gauges
Range of transmitter Indication of remote mounted output
14. The test report form is shown in Table 1 (sheet). Sequence Test Procedure
1.
Prior to sequence test, CONTRACTOR will request COMPANY to
approve sequence and timing flow diagram provided by CONTRACTOR. This approval is to ensure that there will be no change in sequence test during commissioning. CONTRACTOR shall supply approved cause and effect 2. diagrams including the sequence and timing diagrams to COMPANY. Complete interlock system shall be checked for correct sequence of operation and all interlock systems shall be checked for “fail safe” operation. 3. 4. Start-up bypass and maintenance override switches shall generally Where interlock inputs and/or outputs are associated with electrical be "OFF" prior to sequence. equipment, such as motors for pump, compressors and, valves, the sequence test shall be carried out in conjunction with the related section engineer 5. For initiators, manual output signals will be required to generate in lieu of transmitter signals or contacts will be required to make and/or break manually to check the annunciators. Function check will not be necessary, since it should be finished during loop test. 6. For inputs devices, signal generator output will be required to provide analog signal or pulse in lieu of transmitters signals. Contact activation will be required to make and/or break manually to provide digital signal. Function check will not be necessary, since it should be finished during loop test. 7. For output devices, pushing manual trip buttons or making emergency conditions will be required as same manner as checking the initiators correctly. At the same time, answer back shall be checked, where necessary.
8.
For remote pneumatic or motor operated valves, manual switches
or DCS operation key board switches shall be on and/or of to check the valve shall be switched to remote position prior to test.
