Timmie McElwain Gas/Propane Basics... President, Gas Appliance Service Riverside, RI gastc@cox.net Propane System Tests Part 2 by way of a piping system. The regulators in the piping system ensure the proper delivery of pressure to the appliances and that it is not too high or too low. When all of the appliances are shut off, including any pilot lights, pressure will continue to build in the gas lines unless the regulator stops the flow of gas. Flow and Lock-up tests are typically performed on the vapor distribution systems during start-up to determine if the piping system and regulators are sized correctly for the estimated load. These tests should also be performed to determine whether the inlet pressure to an appliance is sufficient and to verify that a regulator will stop gas flow when there is no demand for gas by the appliance. Flow Test A flow test measures the pressure downstream of the firststage and final-stage regulators when the appliances are operating. It determines if the regulators are supplying the amount of gas the system requires. This test is conducted by temporarily installing a water manometer (see Figure 3) or pressure gauge (See Figure 2) in the outlet pressure tap of the firststage regulator and in the distribution line close to the appliance that is furthest away from the final-stage regulator. The manometer or pressure gauge is used to monitor the delivery pressure at the test location when all appliances are turned on. Refer to your company policy for specific procedures. Lock-up Test Lock-up is the amount of pressure necessary to completely stop the flow of vapor through the first-stage and final-stage regulator inlet orifices, when there is no gas demand. A lock-up test measures the pressure in the lines downstream of the final-stage regulator to ensure that the regulator will shut off the flow of propane when the appliances are not calling for gas. The lock-up test is conducted by opening the container service valve and closing all appliance shut-off valves or gas controls. Then the manometer, or pressure gauge, is monitored for any increase in pressure. This continues until the pressure stops rising at or below an acceptable limit. As a Propane professional, one of the most important things you do is ensure customer safety. One of the ways this can be done is to make sure the customer’s vapor distribution system is leak-free and operating effectively. In order to accomplish this, there is a series of five tests that have to be performed: • Pressure Test • Leak Check • Leak Test • Flow Test • Lock-up test You may have heard of these tests or at least a couple of them. The terms are often misused. There are many reasons for this, from code changes that changed the meaning to terms used in different parts of the country. We want to align with federal codes and regulations in this discussion. Be aware that codes in your area may require different test pressures and different times for tests. Check with your local Authority Having Jurisdiction. In Part One we covered Pressure Test per NFPA 58 and NFPA 54. We also covered how to do a Leak Check. In Part Two, we will cover Leak Test, Flow Test, Lock Up Test and testing using a gas meter. In the previous discussion, we determined that a Leak Check identifies leaks by applying pressure to the entire vapor distribution system up to the outlets of the equipment shut-off valves. This test is usually conducted using propane and a pressure gauge or water manometer (“U” Gauge) to monitor pressure change, which would indicate a leak. A leak check is typically performed when a new system, or one that was modified, is placed into operation. It would also be used when there has been an interruption to service, such as an out-of-gas call, gas leak or if a regulator is replaced. Leak Test is carried out after the pressure test and leak check. A leak test uses a liquid leak detector solution (hopefully non-corrosive) or a Combustible Gas Detector (see Figure 1) that is set to detect propane to isolate the exact location of a leak. Once the leak is located it must then be repaired; once the repairs are complete the system must be rechecked to determine it is leak-free. Flow and Lock-up Tests When the appliances are operating, gas is supplied to them Figure 2. Two Examples of Digital Manometers Wohler DM 2000 Testo 506 Figure 1. Combustible Gas Detector 20 ICM/May/June 2016
ICM May-June 2016
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