4.2.22 student book © 2004 propane education & research councilpage 1 4.2.22 performing gas...

4.2.22 Student Book © 2004 Propane Education & Research Council

4.2.22

Performing Gas Distribution System Leak

Checks Requirements for vapor distribution system leak checks are found in Chapter 7 of NFPA 54, National Fuel Gas Code, 2002 edition. Suggested methods for conducting leak checks are found in Annex D to the code.

In this module you will learn to identify:

(1) NFPA 54 regulations & guidelines for gas distribution system leak checks

(2) Procedures for testing for leakage using a manometer

(3) Procedures for testing for leakage using pressure or block gauges

(4) Procedures for testing for leakage using the gas meter

(5) Other considerations regarding leakage in a gas distribution system

4.2.22 Student Book © 2004 Propane Education & Research Council Page 1

NFPA 54 Requirements & Guidelines for Leak Checks

NFPA 54

2002

7.2.1 Test Gases. Leak checks using fuel gas shall be permitted in piping systems that have been pressure tested in accordance with Section 7.1.

7.2.2 Before Turning Gas On. Before gas is introduced into a system of new gas piping, the entire system shall be inspected to determine that there are no open fittings or ends and that all valves at unused outlets are closed and plugged or capped.

7.2.3 Test for Leakage. Immediately after the gas is turned on into a new system or into a system that has been initially restored after an interruption of service, the piping system shall be tested for leakage. Where leakage is indicated, the gas supply shall be shut off until the necessary repairs have been made.

7.2.4 Placing Equipment in Operation. Gas utilization equipment shall not be placed in operation until after the piping system has been tested in accordance with 7.2.3 and purged in accordance with 7.3.2.

A leak check performed on an LP-Gas system should include all regulators, including appliance regulators, and 100% pilot safety control valves in the system.


Procedures for Testing for Leakage Using a Manometer

1. Piping systems serving appliances which receive gas at pressures of ½ psig or less may be leak checked by inserting a water manometer or equivalent device downstream of the final system regulator.

2. This leakage check is performed with propane vapor at 9 inches water column + or - ½ inch for a period of 3 minutes.

Te st p o in t# 1 (Te st Ta p o n O utle t Sid e o f Re g ula to r)

Te st p o in t# 2Te st p o in t# 2Te st p o in t# 2

Te st p o in t# 3

Se rvic e Va lve &1 st Sta g eRe g u la to r

2nd sta g eRe g ula to r

7

6

5

4

3

2

1

0

12

3

4

5

6

7

Connect Manometer to any Test point.

Figure 1. Leak Checking Using a Manometer

4.2.22 Student Book © 2004 Propane Education & Research Council Pages 2 & 3


Step 1: Close the service valve at the propane storage container.

Step 2: After verifying there are no uncapped lines, connect a manometer or equivalent device at a convenient location—

(1) at the outlet test tap of the second-stage or integral 2-stage regulator or

(2) downstream at an appliance shutoff valve or other test tap located before an appliance control.

Step 3: Pilots not incorporating a 100 percent pilot shutoff valve and all manual gas valves not incorporating safety shutoff systems are to be placed in the “off” position prior to leak checking.



Step 4: Except for appliances not incorporating a 100 percent pilot shutoff valve, each individual equipment shutoff valve should be supplying pressure to its appliance for the leak check. This check will prove the integrity of the 100 percent pilot shutoff of each gas valve so equipped, so the manual gas cock of each gas valve incorporating a 100 percent pilot shutoff should be in the “on” position.

Step 5: SLOWLY open the service valve at the propane storage container. Leave it open for two or three seconds; then close it.

Step 6: Release enough gas from the piping system through a range burner valve or other suitable means to drop the system pressure to 9" ± ½" water column.



Step 7: Allow the piping system to remain pressurized for 3 minutes without showing an increase or decrease in the reading on the gauge. If the pressure increases, propane may be leaking into the system from a container service valve. Check to ensure all service valves are fully closed and restart the leak check. If another pressure increase is observed, the container service valve must be repaired or replaced to complete a valid leak check.

Figure 2. U-Tube ManometerMounded on Water HeaterLeak Check Pressure Reading is

8.8 inches w.c.

If the pressure decreases, one or more leaks exist in the system. The source(s) of leakage must be located using a combustible gas indicator, suitable leak detection solution, isolated testing and inspection of piping segments, or a combination of these methods. After the source(s) of leakage are located and repaired, the leak check must be restarted and continued until no change in pressure is observed.



Step 8: Record the test pressure and time for each leak check run. Once the piping system is proven to be leak free, if leaks were repaired, also record the nature and location of repaired leaks.

Step 9: After a successful leak check is performed and recorded, the system may be purged of air and, if appropriate, appliances placed into service following manufacturer instructions.


Procedures for Testing for Leakage Using a Pressure Gauge Block

Figure 3. Leak Checking Using Pressure or Block Gauges



Step 1: Close the service valve at the propane storage container.

Step 2: Install a test block gauge apparatus between the container valve and the first stage regulator.

Step 3: Do a walk through inspection of the vapor distribution system to confirm there are no open pipe terminations not connected to shutoffs and gas appliances that are not capped, or plugged.

Figure 4. Zero to 300 Psig Block Gauge



Pilots not incorporating a 100 percent pilot shutoff valve and all manual gas valves not incorporating safety shutoff systems are to be placed in the “off” position prior to leak checking. Except for appliances not incorporating a 100 percent pilot shutoff valve, each individual equipment shutoff valve should be supplying pressure to its appliance for the leak check.

Step 4: Pressurize the distribution line by opening the service valve on the tank.

Step 5: Read the tank pressure on the block gauge 0-300#.

Step 6: Close the service valve on the tank.

Step 7: Reduce the pressure reading on the pressure test gauge by approximately 10 psig.



Step 8: Observe the 0-300# pressure gauge for either a rise in pressure or a drop in pressure. If there is a rise, the service valve is leaking through. If there is a drop, there is a leak in the system.

Step 9: Allow the piping system to remain pressurized for 3 minutes without showing an increase or decrease in the reading on the gauge.

Step 10: Record the start and end time of the test pressure and leak check once the piping system is proven to be leak free.

If the pressure increases, propane may be leaking into the system from a container service valve. If the pressure decreases, one or more leaks exist in the system. The source(s) of leakage must be located using a combustible gas indicator, suitable leak detection solution, isolated testing and inspection of piping segments, or a combination of these methods. After the source(s) of leakage are located and repaired, the leak check must be restarted and continued until no change in pressure is observed.


Procedures for Testing for Leakage Using the Gas Meter

Annex D to NFPA 54 outlines the following suggested method of testing for leakage using the gas meter (when present in the distribution system).

NFPA 54

2002

• Immediately prior to the test, determine if the meter is in good operating condition and has not been bypassed. Inspect the vapor distribution system and ensure valves and appliance controls are set as described in the procedures for leak checks using a manometer or gauge test block.

• Check for leakage by carefully watching the test dial on the meter to determine whether gas is passing through the meter.

• To assist in observing any movement of the test hand, wet a small piece of paper and paste its edge directly over the centerline of the hand as soon as the gas is turned on. This observation should be made with the test hand on the upstroke.



Figure 5. Test Observation Times for Various Meter Dials

Dial Styles (ft3) Test Time (min)

¼ 5

½ 5

1 7

2 10

5 20

10 30For SI units, 1 ft3 = 0.028 m3

• The following table (Figure 1) can be used for determining the length of observation time.

• If there has been no movement of the test hand for the required length of time, it is assumed that no leakage is present. Record the starting and ending time of the leak check, and the meter register reading on appropriate company forms.



Figure 6. Observing and Recording Meter Reading& Leak Check Start and Ending Times


Other Considerations Regarding Leakage in a Gas Distribution System

• Once a leak in a propane distribution system is known, the leak may be located by using an approved gas detector, a non-corrosive leak detection fluid, or other approved detection method.

• Matches, candles, open flames, or other methods that provide a source of ignition shall not be used.

• Artificial illumination used in connection with a search for gas leakage should be restricted to battery-operated flashlights (preferably of the safety type) or approved safety lamps.

• When searching for leaks, electric switches should not be operated. If electric lights are already turned on, they should not be turned off.

4.2.22 Student Book © 2004 Propane Education & Research Council Pages 9 - 12

Time to See If You Got the Key Points of This Module…

• Complete the Review on pages 9 & 10.

• See if you are ready for the Certification Exam by checking off the performance criteria on pages 11 & 12.

4.2.22 student book © 2004 propane education & research councilpage 1 4.2.22 performing gas...

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