1. Module J-6- Testing and Purging
Objectives of Unit
1. State when the three main tests required for newly installed gas
piping shall be conducted
2. 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 feet
3. 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 systems
5. Name two inert gases commonly used to pressure test gas piping
systems
6. State the testing pressure and the duration of the test for gas piping
systems after appliances are connected
7. Explain the final testing procedure before the gas system becomes
operational
8. State two methods of purging a gas piping system to the outdoors
9. Explain the procedure to be followed when gas piping of 4 inch N.P.S
or larger has been pressure tested with air
10. State the safety precautions that must be taken when purging gas
piping
11. State the maximum increments used in calibrating pressure testing
devices when used on gas piping before appliances are connected
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2. 12. State the maximum increment used in calibrating pressure testing
devices when used on gas piping after appliances are connected.
Introduction
All gas piping systems must be tested before being put into operation the
reasons-are obvious in that leaking natural gas could cause a dangerous
condition in an enclosed space or building.
The Canadian Gas Association Installation Code 8-149-1 stipulates certain
testing procedures and conditions for testing natural gas systems. These
testing procedures and conditions are discussed in his learning package.
Frequent reference should be made to the CGA Code and to the CGA Gas
Appliance 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 natural
gas system must be purged before being put into operation.
The various procedures and regulations pertaining to purging are also
presented in this package.
Testing
All newly installed natural gas piping installations should be tested before
being put into service. Tree main tests that should be performed in order to
comply 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 on
Testing before appliances are installed involves the pressurization of
the gas piping system using air or an inert gas such as carbon dioxide or
nitrogen. The person conducting the testing must ensure that all openings
are capped or plugged off and the system completely isolated before the air
or inert gas is forced into the piping system.
The test pressure table for pressurization with air or inert gas is given in
Table 1 on the next page.
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3. Table 1
Working Diameter Length Test Test
Pressure 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 ½
Less than ½ All sizes More than 25 1½
½ to 33 All sizes 100 50 24
Over 33 All sizes All lengths 1 ½ times the 24
All lengths max. Operating
pressure
All piping in The greater 24
false of 50 psig or
ceilings and 1 ½ times the
concealed max. Operating
spaces pressure
For tests of 1/2 and 1 1/2 hours, a mercury manometer or slope gauge or
any 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 of
supply should be isolated before any pressure readings are recorded.
The high pressure tests must be conducted before the appliances are
connected, to prevent damage to shut-off valves or other manifold valves or
components, which could cause a hazardous condition at a later date.
The testing of natural gas systems after appliances have been connected
is 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 the
meter remains steady or untiI it can be ascertained that there is no gas flow
through the regulator. The valve at the inlet to the system is then closed
and the gas piping in the system isolated. The piping should then be at the
normal working pressure at which the system wiII operate.
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4. The pressure gauge or manometer should be calibrated to read in
increments of not greater than 1 inch water column, and the normal working
pressure 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 be
located by using an approved type of liquid leak detector solution on all
joints 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 be
made of the test dial on the gas meter for a period of 10 minutes. Any
movement 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 are
oxygen and liquids
Purging
After gas piping has been pressure tested using air or an inert gas, the
piping system must be fully purged by forcing the air or inert gas from the
pipelines by natural gas pressure. Gas piping should be purged using the
appliance farthest from the meter, to ensure that the supply line is fully
purged.
Piping or tubing supplying an appliance with an input of under 400,000
B.T.U./hr. may be purged at the open top 'burner by a Iighted taper or
similar means of ignition. The purging shall continue untiI a stable flame is
established.
A system may also be purged outdoors by either monitoring the discharge
outlet with a gas detector or by burning through an approved type of purge
burner. A purge burner should never be used indoors. When purging
outdoors, the temporary pipe or tube should terminate no closer than 10
feet from any buiIding or air intake. The person purging must constantly
supervise and control the purge by a quarter-turn valve (handle attached)
located within 5 feet of the purge point. Smoking or any other uncontrolled
means of ignition shall not be permitted within the area while purging is in
progress.
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5. Any piping system of 4 inch N.P.S. or larger must be purged outdoors, and
if air has been used in the pressure testing process, the system must first
be purged with carbon dioxide or nitrogen before being purged with natural
gas.
Piping used for purging shall be reduced to 1/2 inch N.P.S. at the outdoor
purging point. Figure 1 illustrates a typical purge burner assembly.
Figure 1
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6. Self Test
1. 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.
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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.
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8. Answers to Self Test
1. 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 liquids
5. Carbon dioxide and nitrogen
6. 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
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