CLASS DH - PNEUMATIC TESTING - GREATER THAN 1 BAR (15 PSIG)

Transcription

1 Page 1 of 10 CLASS DH - PNEUMATIC TESTING - GREATER THAN 1 BAR (15 PSIG) 1. SCOPE 1.1 To provide definitive requirements for HIGH PRESSURE PNEUMATIC testing of piping systems according to ASME B31.3. This test method shall not be applied to non-metallic piping materials. 1.2 The piping system as used herein is intended to include the pipe, valves and fittings. Vessels, process equipment, instruments, and relief devices are not included. 1.3 The acceptance of piping systems under this specification is for pressure tightness only. 2. CLASS DH--PNEUMATIC GREATER THAN 1 BAR (15 PSIG) 2.1 This test is performed by pressurizing the system with a gas, to a specified Test Pressure, but not less than 0.3 Bar (5 Psig) The Owner shall verify if site safety practices and/or local authorities impose additional requirements or restrictions The Owner is responsible to assure that all conditions and safety concerns identified in G4D are addressed Interim testing may use a sonic leak detector to listen for leaks. Refer to G4S and G8S for procedures The final test is when the system can sustain a specified pressure for a minimum period of 30 minutes plus the time to do the examination, without evidence of leaks. 2.2 A complete line or section of line containing several valves and branches shall be tested at one time Exemptions to 2.2 can include valves that are pre-cleaned for a specific service, lined, or specialty valves that do not meet the required line test pressure If the valves cannot be tested with a system test, the contractor shall ensure the valves are tested prior to installation per ASME B31.3. Contractor shall confirm allowable test pressure of valves prior to performing work.

2 Page 2 of A set of marked-up or highlighted drawings may be used. The purpose is to identify the boundaries of separate piping systems to be tested, the locations of isolation blanks, valve positions, double block and bleed valve arrangements, location of pressure injection or connection points, location of pressure gauge(s), recorders for pressure, temperature, and other instrumentation used to validate the test. 2.3 CAUTION: PNEUMATIC TESTING should be used only as a last alternative when hydrostatic testing is not practical or could damage the system. Pneumatic Testing involves the hazard of potential release of the energy stored as a compressed gas. Carefully planned and supervised procedures shall be followed. Persons responsible for the testing are to be informed of the procedures to be followed. In cold weather, care must be taken to minimize the chance of brittle fracture during the test Carbon Steel Pipe The metal temperature of carbon steel piping subjected to a pneumatic test shall not be colder than 15.5C (60F). Situations where the temperature could be colder than 15.5C (60F) may be acceptable, but must be analyzed by Owner prior to testing Non-Ferrous and Stainless Steel Pipe or Tubing (Including that with Carbon Steel Lap-Joint Flanges) The metal temperature of non-ferrous and stainless steel piping subjected to a pneumatic test shall not be colder than the minimum Design Temperature given in the pressure-temperature ratings of the governing CPPS Specification plus 16.7C (30F) A materials engineer shall conduct a review of installed equipment to ensure that the ductile to brittle transition temperatures of the materials are below the test temperature. 2.4 A Safe Work Procedure shall be written, and approved prior to beginning of a CLASS DH PNEUMATIC test. The procedure shall cover the following items as minimum requirements: a. Pretest visual inspection. The system to be tested shall be reviewed to ensure that the complete system can be depressurized at completion of the test. b. Areas to be roped off and minimum distances to be maintained, according to local site standards, government regulations, or Table 1 in EMETL G4D (as approved by Owner). c. Time schedule. d. Indoctrination of personnel on hazards involved.

3 Page 3 of 10 e. Form G4Q , Pneumatic Testing Safe Work Procedure Checklist, to be completed and signed. 3. TEST MEDIUM AND EQUIPMENT Pneumatic tests shall be made with air, nitrogen, or other nonflammable, nontoxic gases where applicable. 3.1 Nitrogen is the preferred fluid for pneumatic testing at a gage Pressure above 6.9 Bar (100 Psig). 3.2 Air shall not be used to test new piping at gage pressures above 20 Bar (300 Psig). 3.3 Air shall not be used to test unclean or used piping at any pressure, unless the piping has been cleaned, purged with inert gas, tested and sampled to verify that a combustible gas mixture is not present Air compressors shall be equipped with discharge filters for removal of water, oil, and foreign matter. Maximum discharge temperature of lubricated air compressors shall be 150C (300F) The sonic testing equipment shall be capable of detecting frequencies between 30KHz and 50KHz, and used in accordance with the manufacturer s recommendations. 4. PREPARATION FOR TEST 4.1 The line schedule issued should give the Common Product Piping Specification for each line and may include material, size, insulation, etc., and the required Test Pressure, Test Class (Method) and other requirements of the pipe specifications. 4.2 In the absence of a line schedule, the Test Pressure and Test Class (Method) required may be covered in the job project piping specification, contract technical job instructions, construction order, or for maintenance jobs, by Work Order. If not specified, refer to the appropriate Common Product Pipe Specifications. 4.3 Prior to testing, a thorough visual inspection shall be made for defects such as improper materials, poor gasket installation and loose joints. All bolts shall be made up tight in the system to be tested. Unless noted otherwise, gaskets per pipe specifications shall be used. All other mechanical joints shall also be examined.

4 Page 4 of Joints shall NOT be insulated or covered in any manner, for this test. 4.5 Piping systems connected to equipment shall be isolated from the equipment by means of a line blind, prior to cleaning and testing. If a valve is connected to the equipment, the blind shall be between the valve and the equipment, with the valve in the open position Where piping can not be isolated from equipment for testing, or it is desirable to include equipment in leak testing, the equipment may be included in the test provided: The piping system Test Pressure does not exceed either manufacturer s test pressure or a pressure limit imposed by the position and condition of the equipment The equipment does not contain any internals or materials that may be damaged by testing No rotating equipment may be included in any piping system leak test. 4.6 Valves shall be left open during the testing. If a valve is located at the end of a line, a blind flange or plug shall be installed. Where a valve can not be tested in the open position, do one of the following: Blank the upstream side of the valve Remove the valve and install a blind flange Remove the valve and install a flanged test spool where continuity of the line is required for purpose of the test. 4.7 Test blinds shall be installed between existing piping and new piping to prevent introducing cleaning and testing medium into existing lines, or pressurizing the existing system When isolation and blanking is required for the purpose of leak testing, it shall be made using the blind flanges according to the CPPS for the pipe line, or using test blinds as described by Engineering Specification G4G or G4G Test blinds shall be capable of withstanding the test pressure Contractor fabricated appliances used for leak testing of pipe lines such as test stands, test blinds, blind flanges, etc. - shall be designed and fabricated in accordance with governing Codes and Standards, such as ASME B31.3, ASME B16.5, ASME B16.47,

5 Page 5 of 10 ASME B16.48, etc. This includes use of proper materials, as well as assembly, welding, post treatment, and inspection requirements. 4.8 Leak tests shall include as much instrument process piping and tubing as possible. Where an instrument process line contains more than one block valve, all valves shall be open except the one nearest the instrument. 4.9 If cleaning has a negative effect on control valves, pressure reducing valves, level controllers, level switches, orifice plates, turbine meters, massflow meters, vortex meters and other instruments or fittings, then remove these items only if designated by the Owner. These items shall be removed from the lines before cleaning and reinstalled before testing. All such items shall be cleaned separately after removal Where control valves are closed, the line shall not be tested until the valves have been opened by the Owner. The line bore orifice spacers and gaskets or spare rings furnished with meter runs shall be installed prior to cleaning and remain in place until after testing. If any instruments and similar special equipment cannot withstand the required test pressure, they shall be removed only if designated by the Owner. Direct operated or self-contained regulators and float actuated devices shall be removed, or blocked and vented Safety valves and rupture discs installed for fit-up shall be removed during the test and reinstalled only after successfully completing the test. Some inline equipment and valves, such as transflow or three-way valves, may not be able to be tested. The line shall then be tested with temporary spool in place Check available drawings for any specific installation or operating instruction pertaining to expansion joints. Test Pressure shall not exceed the maximum allowable specified test pressure of the expansion joint Expansion joints having tie-rods shall be tested as part of the piping system unless otherwise specified. The tie-rod nuts must be hand tight, with no slack under the outside nuts.

6 Page 6 of Expansion joints not having tie-rods shall be removed or isolated from the test Insulation will not be allowed on systems under test except on those parts which have had a documented certified shop or mill test Spring support travel stops shall not be removed until all testing has been completed Prior to administration of the test visually observe the piping system to assure it is properly prepared Care should be exercised to check and confirm that there are no sections of the piping system where gas can be trapped downstream of check valves, or sections isolated by other valves, such that the piping cannot be safely vented after testing. 5. ADMINISTRATION OF TEST 5.1 All tests shall be witnessed and accepted by the Owner or Owner designee The presence of the Owner or Owner designee is not necessary while initial checking of lines for leaks is in progress. 5.2 A Pressure Relief Device shall be provided, having a set pressure not higher than the test pressure plus the lesser of 3.4 BAR (50 psig) or 10% of the test pressure. 5.3 Special precautions shall be taken if testing is to be performed in the open air, with regard to weather such as wind, or background noise, or other influences which may affect the accuracy of the test results. 5.4 Pressure gauges shall be of a suitable scale capacity for the test pressure, having a dial at least 115 mm (4-1/2 ) in diameter. The test pressure should be approximately 60% of full scale. The maximum pressure capacity shall not exceed three times the particular test pressure. Gauges will have established traceable identities and shall be accurate to within 1% of full scale. There shall be a minimum of two pressure gauges for each test Pressure gages used for testing shall be calibrated at least every six months. Calibration shall be traceable to individual gages for verification. Records of calibration shall be made available upon request Prior to the Pneumatic Test, a pre-test shall be conducted

7 Page 7 of 10 according to Test Class D, G4S , at a pressure not to exceed 1 Bar (15 Psig). (Exceptions to G4S ) 1)Para 4.3 priming and/or Painting shall be permitted prior to the pre-test, as long as the pre-test is not considered a "Sensitive Leak Test" in accordance with ASME B31.3 para as part of the "Alternative Leak Test" ASME B31.3 para or requirements of Category M testing ASME B31.3 para. M345. 2)Para 2.1 is not mandatory to apply bubble forming solution to all joints, for this pre-test. 5.6 The pressure shall be raised slowly in stepwise fashion as described in the following table.

8 Page 8 of 10 TABLE 1. PNEUMATIC TEST PROCEDURE Preliminary Test Step 1 Primary Test Step 2 Primary Test Step 3 Primary Test Step 4 (Final) Raise pressure to 25 psig (172 kpag) or to 25% of primary test pressure, whichever is lower. Disconnect supply. Hold pressure for 10 minutes. Gradually increase the pressure to 50% of the primary test pressure. Do this in steps of approx. 20% of the primary test pressure,, holding at each step for 2 to 3 minutes for piping to equalize strains. Increase pressure in increments of 10% of the primary test pressure until primary test pressure is reached. At each increment, close test gas inlet valve at test manifold and observe test gage for 5 minutes. Maintain primary test pressure for 30 minutes. Hold for 10 minutes at 50% of the primary test pressure mark. Observe gage for loss of pressure (visual) inspection of the system is not required. If pressure loss is noted, release pressure and do necessary repair. Repeat preliminary test. Blowdown system to 80% of primary test pressure for final leak testing. Check for leaks. If pressure loss exceeds 10%, blowdown to preliminary test pressure and check for leaks. Proceed to next increment if pressure loss is not detected. See acceptance standard, Paragraph If leaks are found, release pressure and do necessary repair. Repeat preliminary test. If no leaks are found, proceed with primary test. Step 2. If no appreciable loss of pressure is detected (in the judgment of the inspector) after 10 minutes, proceed with Step 3. Proceed with Step 4. End

9 Page 9 of All personnel shall be kept clear of the immediate area while the test pressure is being raised. See EMETL G4D for the Safe Distance Table requirements Acceptance A commercially available bubble forming solution (not soap and water) such as SNOOP or SHERLOCK shall be applied to all joints under examination including valve stem and packing glands Flanges joints (except at wafer valves and similar items) may be taped with duct or masking tape and punched with a small hole so leakage can be observed at the hole After holding the piping system at the Test Pressure for the specified time, all joints not previously tested shall be examined for leaks with the piping system under not less than 80% of the specified Test Pressure. When no indication of leakage of the test fluid is observed, the piping system is acceptable. 5.7 Interim testing for leaks may be done using a sonic leak detector The testing shall continue in increments until the final test pressure is reached and held for 30 minutes minimum without evidence of any leakage. 5.8 Variations of pressure and volume due to temperature changes will be taken into account in determining whether pressure during test is satisfactory. All attempts shall be made to stabilize the temperature of the test, prior to starting the test. 6. RETESTS 6.1 In the event that a piping system or any part fails to pass the test prescribed, a new test shall be applied after repairs and corrections have been made. This retest shall include all parts of a connected system which may have passed a test previously, but have been affected by the corrections made or by a delay attending to the corrections. 7. POST TEST 7.1 At the completion of the test, all blinds, plugs and caps used to isolate equipment, vessels and instruments shall be removed, flange faces and threads inspected for damage, and piping reconnected. Special care is required when reconnecting these

10 points to avoid leaks. Page 10 of New gaskets shall be used when reinstalling flanged items or reconnecting to flanged equipment. Gaskets removed after tests shall not be reused. 7.3 Vents and drains shall be capped, plugged or blanked after completion of test according to pipe specifications or job instructions. 7.4 All valves shall be placed in the open or closed position as determined by the Owner. i i 10/24/2012, MOC2012_12142, By: Dan Devine, Supersedes Issue Date: 29-AUG- 2006, Fully reviewed and revisions made