in. w.c. (2.2 kPag ± 0.1 kPag), and observing the device for a pressure change. If fuel gas is used as a pressure source, it is necessary to pressurize the system to full operating pressure, close the container service valve, and then release enough gas from the system through a range burner valve or other suitable means to drop the system pressure to 9 in. w.c. ± 1.2 in. w.c. (2.2 kPag ± 0.1 kPag). This ensures that all regulators in the system upstream of the test point are unlocked and that a leak anywhere in the system is communicated to the gauging device. The system should be allowed to stand for three minutes without showing an increase or a decrease in the pressure. 3The third method is performed by inserting a 30psig (207 kPag) pressure gauge on the downstream side of the first stage regulator, admitting normal operating pressure to the system and then closing the container valve. Enough pressure should be released from the system to lower the pressure gauge reading by 5psig (34.5 kPag). The system should be allowed to stand for three minutes without showing an increase or a decrease in the pressure. Pressure Test per NFPA 54 In accordance with NFPA 54 National Fuel Gas Code, a pressure test checks for leaks in the interior lines of a vapor distribution system. This covers the lines downstream of the outlet of an integral two-stage regulator, second stage regulator or meter. This location in the piping system is called “Point of Delivery.” This test applies pressure of not less than 1½ times the proposed maximum working pressure of the interior piping, but not less than 3psig. The test medium shall be air, nitrogen, carbon dioxide or an inert gas. It is performed only on newly-installed interior piping systems or on systems repaired or modified as specified by NFPA 54. Disconnecting and isolating each appliance is important because many appliance gas controls are not designed to handle the amount of pressure that will be applied during this pressure test (gas valve can only withstand ½ lb of pressure (14" water column W.C.). The minimum test duration for most residential and small commercial systems is ten minutes. NFPA 58 also requires a Leak Check/Pressure Test on the entire vapor distribution system; however, propane may be used for this test. A Leak Check identifies leaks by applying pressure to the entire vapor system up to the outlets of the equipment. The test is usually conducted using propane and a pressure gauge or water manometer to monitor a pressure change which would indicate a leak. A leak check is performed when a new or modified gas piping system is placed into service, or when there has been an interruption to service, such as a gas outage, gas leak, or regulator replacement. An NFPA leak check test is required for propane leaks by applying pressure to the system downstream from the point of delivery. It basically checks up to the outlet of the equipment or appliance shut-off valves. However, it is recommended here to check the entire vapor distribution system, including the appliance connectors and the appliance gas controls. This test is usually conducted using fuel gas instead of air. Individual company policy will dictate how this test should be conducted. The test can be done either with the 300 lb gauge following the procedure outlined earlier as the pressure test with a couple of modifications. The test is performed by installing a T-block and a 300lb pressure gauge between the container service valve and the first stage regulator. (see Figure 1) Do a walk-through inspection (turn off all valves except for 100% safety pilot controls—they should be in the “ON” position with the pilot burner not lit.) This will test to insure that the pilot safeties drop out when the pilot gas is no longer supplied to the pilot to hold open the safety. Then slowly open the service valve allowing vapor pressure to fill the line. Once that is complete, close the service valve and reduce the pressure reading on the block gauge by 10psig lower than the container pressure, using the connector installed between the service valve and the first stage regulator. Keep in mind this is a release of some gas, so make sure it is safe to do so (no sources of ignition). What you are watching for is either an increase in pressure (a leaking service valve) or a drop in pressure indicating a leak. This test must be conducted for three minutes. If a leak is indicated, it must be repaired. On short runs of piping, a leak detection solution may be used to find the leak. Upon completion, re-light all equipment and test with a soap solution all fitting, etc. that were disturbed. As stated in item three previously, the third method is performed by inserting a 30psig (207 kPag) pressure gauge on the downstream side of the first-stage regulator (see Figure 2, pg.8), admitting normal operating pressure to the system and then closing the container valve. Enough pressure should be released from the system to lower the pressure gauge reading by 5psig (34.5 kPag). The system should be allowed to stand for three minutes without showing an increase or a decrease in the pressure. Figure 1. Leak check using 300 lb gauge 6 ICM/March/April 2016
ICM March-April 2016
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