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  • 1. Module J-6- Testing and Purging Objectives of Unit1. State when the three main tests required for newly installed gas piping shall be conducted2. State the testing pressure and the duration of the test for gas piping systems before appliances are connected where the working pressure is less than 1/2 P.S.I.G. and the piping is less than 100 feet3. State the testing pressure and the duration of the test for gas piping systems before appliances are connected where the working pressure is 1/2 to 33 P.S.I.G.4. Name two substances that should not be used to pressure test gas piping systems5. Name two inert gases commonly used to pressure test gas piping systems6. State the testing pressure and the duration of the test for gas piping systems after appliances are connected7. Explain the final testing procedure before the gas system becomes operational8. State two methods of purging a gas piping system to the outdoors9. Explain the procedure to be followed when gas piping of 4 inch N.P.S or larger has been pressure tested with air10. State the safety precautions that must be taken when purging gas piping11. State the maximum increments used in calibrating pressure testing devices when used on gas piping before appliances are connected Module J6 - Testing and Purging 1
  • 2. 12. State the maximum increment used in calibrating pressure testing devices when used on gas piping after appliances are connected.IntroductionAll gas piping systems must be tested before being put into operation thereasons-are obvious in that leaking natural gas could cause a dangerouscondition in an enclosed space or building.The Canadian Gas Association Installation Code 8-149-1 stipulates certaintesting procedures and conditions for testing natural gas systems. Thesetesting procedures and conditions are discussed in his learning package.Frequent reference should be made to the CGA Code and to the CGA GasAppliance Installation Manual, which are periodically revised to keep up-to-date with changes in the gas industry.After the gas system has been tested with air, or an inert gas, the naturalgas system must be purged before being put into operation.The various procedures and regulations pertaining to purging are alsopresented in this package.TestingAll newly installed natural gas piping installations should be tested beforebeing put into service. Tree main tests that should be performed in order tocomply with gas code regulations: a) testing of the piping system before appliances are connected; b) testing of the piping system after appliances are connected. c) testing of .the piping system after the gas has been turned onTesting before appliances are installed involves the pressurization ofthe gas piping system using air or an inert gas such as carbon dioxide ornitrogen. The person conducting the testing must ensure that all openingsare capped or plugged off and the system completely isolated before the airor inert gas is forced into the piping system.The test pressure table for pressurization with air or inert gas is given inTable 1 on the next page. Module J6 - Testing and Purging 2
  • 3. Table 1Working Diameter Length Test TestPressure of pipe of pipe or Pressure(PSIG) Duration(PSIG) or tubing tubing(ft) (Hrs) (inches)Less than ½ Less than ½ 100 or less 25 ½Less than ½ All sizes More than 25 1½½ to 33 All sizes 100 50 24Over 33 All sizes All lengths 1 ½ times the 24 All lengths max. Operating pressureAll piping in The greater 24false of 50 psig orceilings and 1 ½ times theconcealed max. Operatingspaces pressureFor tests of 1/2 and 1 1/2 hours, a mercury manometer or slope gauge orany device calibrated in increments not exceeding 1/4 pound must be used.Tests conducted over a 24-hour period require a pressure recording device.Note: After bringing the system up to the test pressure, the source ofsupply should be isolated before any pressure readings are recorded.The high pressure tests must be conducted before the appliances areconnected, to prevent damage to shut-off valves or other manifold valves orcomponents, which could cause a hazardous condition at a later date.The testing of natural gas systems after appliances have been connectedis accompIished by first ensuring that aII appliances have been shut off.Natural gas is then allowed to flow into the system until the test dial on themeter remains steady or untiI it can be ascertained that there is no gas flowthrough the regulator. The valve at the inlet to the system is then closedand the gas piping in the system isolated. The piping should then be at thenormal working pressure at which the system wiII operate. Module J6 - Testing and Purging 3
  • 4. The pressure gauge or manometer should be calibrated to read inincrements of not greater than 1 inch water column, and the normal workingpressure should be maintained for a minimum time period of 10 minutes.If a drop in pressure is noticed, the source of the leak, or leaks, shall belocated by using an approved type of liquid leak detector solution on alljoints and fittings in the piping system.The final test is performed when the gas system is to be put into operation.While ensuring that all appliances are shut off, a careful check should bemade of the test dial on the gas meter for a period of 10 minutes. Anymovement of the hand on the test dial indicates the presence of a leak.Two substances that should not be used to pressure test gas piping areoxygen and liquidsPurgingAfter gas piping has been pressure tested using air or an inert gas, thepiping system must be fully purged by forcing the air or inert gas from thepipelines by natural gas pressure. Gas piping should be purged using theappliance farthest from the meter, to ensure that the supply line is fullypurged.Piping or tubing supplying an appliance with an input of under 400,000B.T.U./hr. may be purged at the open top burner by a Iighted taper orsimilar means of ignition. The purging shall continue untiI a stable flame isestablished.A system may also be purged outdoors by either monitoring the dischargeoutlet with a gas detector or by burning through an approved type of purgeburner. A purge burner should never be used indoors. When purgingoutdoors, the temporary pipe or tube should terminate no closer than 10feet from any buiIding or air intake. The person purging must constantlysupervise and control the purge by a quarter-turn valve (handle attached)located within 5 feet of the purge point. Smoking or any other uncontrolledmeans of ignition shall not be permitted within the area while purging is inprogress. Module J6 - Testing and Purging 4
  • 5. Any piping system of 4 inch N.P.S. or larger must be purged outdoors, andif air has been used in the pressure testing process, the system must firstbe purged with carbon dioxide or nitrogen before being purged with naturalgas.Piping used for purging shall be reduced to 1/2 inch N.P.S. at the outdoorpurging point. Figure 1 illustrates a typical purge burner assembly.Figure 1 Module J6 - Testing and Purging 5
  • 6. Self Test1. List when the three main tests required for newly installed gas piping shall be conducted. a) b) c)2. State the testing pressure and the duration of the test for gas piping systems before appliances are connected where the working.3. pressure is less than 1/2 P.S.I .G. and the piping is less than 100 feet.4. State the testing pressure and the duration of the test for gas piping systems before appliances are connected where the working pressure is 1/2 to 33 P.S.I.G.5. Name two substances that should not be used to pressure test gas piping systems.6. Name two inert gases commonly used to pressure test gas piping systems.7. State the testing pressure and the duration of the test for gas piping systems after appliances are connected.8. Explain the final testing procedure before the gas system becomes operational.9. State two methods of purging a gas piping system to the outdoors. a) b)10. Explain the procedure to be followed when gas piping of 4 inch N.P.S. or larger has been pressure tested with air.11. State the safety precautions that must be taken when purging gas piping. Module J6 - Testing and Purging 6
  • 7. 12. State the maximum increments used in calibrating pressure testing devices when used on gas piping before appliances are connected.13. State the maximum increment used in calibrating pressure testing devices when used on gas piping after appliances are connected. Module J6 - Testing and Purging 7
  • 8. Answers to Self Test1. a) Before appliances are connected. b) After appliances are connected. c) After the gas has been turned on.2. Testing pressure 25 P.S.I.G. for 1/2 hour.3. Testing pressure 50 P.S.I.G. for 24 hours.4. Oxygen and liquids5. Carbon dioxide and nitrogen6. The normal working pressure of the system for 10 minutes.7. With all appliances turned off, a careful check should be made of the test dial on the meter for a period of 10 minutes.8. a) Monitoring the discharge outlet with a gas detector. b) Burning through an approved type of purge burner.9. The piping should first be purged with carbon dioxide and/or nitrogen and then purged with natural gas.10. Smoking is not permitted and maximum precautions must be taken to ensure the elimination of all potential sources of ignition.11. 1/4 P.S.I.12. inch water column Module J6 - Testing and Purging 8