PAGE 1 OF 6 General: Pressure Testing Shop Built Tanks Pressure testing tanks with either positive pressure or vacuum can be a very dangerous exercise. It is important to understand the equipment involved in pressure testing, and to observe the proper safety precautions and operating procedures in order to prevent injuries and equipment damage. Some general safety precautions include: 1. It is critical that a tank never be left unattended while an airline is connected. If the pressure relief valve failed the tank could be over pressured and explode. 2. Do not stand in front of tank heads or fittings while the tank is being pressurized, if a failure occurred fittings or pieces of the tank could be shot out by the pressure. 3. Be aware of any bulging or deformation of the tank during testing. If deformation or bulging is observed release pressure immediately. (note that some deformation is normal, particularly in rectangular tanks, but when in doubt: release the pressure) 4. Do not begin pressure testing a tank until all welding is complete and all welds have been visually inspected and repaired. 5. Do not apply vacuum to a single wall tank or to the inner (primary) tank of a double wall tank. 6. Never allow the pressure difference between the inner and outer tank of a double wall tank to be more than three and one-half (3.5) PSI. 7. Never exceed the maximum pressure for a tank as defined on the print. 8. Check the print before testing. Be aware: Is it a single wall or double wall Which fittings go to the Primary and which go to the Secondary Check to see if it is single compartment or multi-compartment How much pressure (PSI) for Primary and Secondary Is everything that the print calls for on the tank 9. Never test a tank unless you have checked the print to verify its test pressure. Equipment: Use supplied test fitting kit from test fitting area. Test fitting kits will be composed of: Pressure Gauge Pressure Relief Valve Regulator Check all components to see if operational. If any of the components of the test kit appear to be broken replace them before beginning testing. Verify the date of the last calibration; do not use any components that have current calibration certification. Warning: NEVER ALTER TEST EQUIPMENT
PAGE 2 OF 6 Pressure Gauge- shows what pressure exists in the system Check Pressure Gauge to make sure that none of its components are bent or pinched, that the needle moves freely and that everything appears to be in good working order. If the gauge appears to be broken or its calibration is expired replace it before beginning testing. Pressure Relief Valve- rapidly releases pressure when it passes the valve s set limit Check the pressure relief valve to be sure that all the parts move freely, that there is no dirt or foreign matter blocking the valve and that the calibration date has not expired. Regulator- limits the pressure of incoming air to control how fast pressure builds in the tank Check Regulator for any signs of obvious damage: cracks, torn or weeping seals, broken or missing parts. Be sure to check that the regulator is designed to operate at the proper pressure, that it has been set properly for the job and that its calibration date is not expired.
PAGE 3 OF 6 The regulator is installed upstream of the pressure relief valve, and both the relief valve and regulator are upstream of the gauge. The proper configuration is shown in the photo below. Install test fittings in proper locations with pipe sealant and tighten with a wrench. Notice that the Pressure Gauge (located all the way to the left) is downstream of the Pressure Relief Valve and the Regulator (located to the right of the gauge in this photo). This arrangement is critical to the safe function of the pressure testing setup, and must be followed at all times when pressure testing shop built tanks. Procedure: Before beginning the test verify that the test fittings are all correctly installed, that the tank pressure is listed on the print and that there are no other employees working on the tank who could be injured in the event of a pressure release. Single Wall Tanks Connect test fittings to the tank; be sure that the pressure relief valve and gauge are downstream of the air supply as shown in the diagram and photo below. Pressurize the tank. Watch the gauge to make sure the needle is moving freely. Once you reach the proper pressure shut off the air at the tank and the hose. Remove the hose from
PAGE 4 OF 6 the test valve. Do not leave the inlet hose connected to the tank when you are performing testing. When the tank is pressurized properly, run a soapy water mixture over all welds in an upward motion, marking all leaks, or areas that might be leaks, as they are identified by bubbling. Let the air out of the tank using the valve on the test fitting. Do not loosen any plugs, caps or manhole covers to let air out. When the tank is under pressure there is enough force on the fittings to turn them into dangerous projectiles if they are unscrewed. Repair all previously identified leaks and suspicious areas. Pressurize the tank again and use a soapy water mixture to check for leaks. If leaks are found again inform a senior employee that you are having problems. If all leaks are fixed have a senior employee verify the test results before you break down the testing kit. Release the pressure from the tank, and after testing is complete return the test kit to designated lead man. Double Wall Tanks Connect test fittings to both the inlet for the primary tank and the inlet for the secondary tank. Be sure that both tanks have a pressure release valve and a properly installed pressure gauge. Pressurize the Primary tank first. Watch the gauge to make sure the needle is moving freely. Once you reach the proper pressure shut off the air at the tank and the hose. Remove the hose from the test valve. Check the Primary to make sure it is holding air. If not, double check that the fittings are all properly installed and tightened. Pressurize the primary again and verify that it holds air. Disconnect from the test fitting to the Primary and connect the air hose to the test fitting for the Secondary, or switch the supply valve to the Secondary tank position (depending upon your line configuration). Pressurize the Secondary. The pressure difference between Primary and Secondary may never be more than 3-1/2 P.S.I. Putting too much pressure in the secondary tank could cause it to explode, or could cause the primary to implode. When the tank is pressurized properly, run a soapy water mixture over all welds in an upward motion, marking all leaks, or areas that might be leaks, as they are identified by bubbling. Let the air out of the Secondary using the valve on the test fitting. Do not loosen any plugs, caps or manhole covers to let air out. When the tank is under pressure there is enough force on the fittings to turn them into dangerous projectiles if they are unscrewed.
PAGE 5 OF 6 Repair all previously identified leaks and suspicious areas. Pressurize the Secondary again and use a soapy water mixture to check for leaks. If leaks are found again inform a senior employee that you are having problems. If all leaks are fixed have a senior employee verify the test results before you break down the testing kit. Release the pressure from both the Primary and Secondary tanks at the same time. After testing is complete return the test kit to designated lead man. Repads (Doublers) Make sure the tell-tale hole is taped properly before installing the repad, since it will not be possible to tap it after installation. Install the repad. After all required welding is complete inspect the welds inside and out to make sure they are proper and ready for testing. Put pipe sealant on test valve and screw it into tell-tale hole. Tighten the valve properly. Connect a hand pump to valve and pressurize the assembly to the value specified by the print. Run soapy water over all welds in an upward motion, checking for bubbles generated by air leaks. Mark any areas that require repair. Let the air out of the assembly and patch the marked suspicious spots and leaks. Re-test. If all leaks are fixed have a senior employee verify the test results before you break down the testing kit. After testing is complete return the test kit to designated lead man. Training: No employee may pressure test any tank until they have completed the Company s pressure testing training program. A qualified person with sufficient experience and technical understanding of pressure testing to instruct others in the process shall complete the training. Training shall include: A classroom session that covers the setup, operation, inspection, maintenance, breakdown and storage of the equipment used for testing tanks. A practical training session during which the employee s performance is evaluated to assure that they understand how to safely perform pressure testing. Retraining is to be conducted: Every two years When any accident or near miss occurs If a deficiency in the employees understanding of the process is observed
PAGE 6 OF 6 When new processes or materials are introduced which might change the requirements of the process Certification of training shall be maintained at the Company s administrative office.