Pressure Test Procedures
Pressure testing is one of several ways of evaluating the structural integrity of vessels, conduits, mechanical equipment such as pumps and valves, and process equipment such as heat exchangers and distillation towers designed to contain, convey, or process liquids and gases. There are several different safety objectives in pressure testing. The first is that the device won't explode or burst under pressure. The second is that the device won't stop functioning under pressure. The third is that leakage won't allow dangerous substances to escape from the device, threatening life, limb, or property.
Hydrostatic Pressure Testing
Most apparata designed to contain very high pressures are hydrostatically tested, meaning that they are filled and pressurized with liquid water or oil, as opposed to with air, because of their incompressibility. This means that if a pressure tank filled with water under high pressure failed and a seam opened, the tank wouldn't explode because the liquid's specific volume wouldn't suddenly expand under ambient conditions. The specific volume of a gas always increases rapidly, even explosively, with a sudden decrease in pressure. Other tests use water or oil containing radioactive or fluorescent dyes which are easily sensed with instrumentation.
Gas Pressure Testing
At lower pressures, the item can be filled with pressurized gas and leak tested with soap bubbles. This is how an auto mechanic usually locates a leak in a tire. This same method is used by plumbers to spot leaks in domestic natural gas lines. The soap lowers the surface tension of the water, precipitating the prolific formation of tiny bubbles or foam around a small leak.
Sniffers
Automotive air conditioning can be analyzed for leaks by use of a sniffer, which is a refrigerant-sensitive hand-held device with a long flexible tubular wand which quickly detects the presence and source of even a small amount of refrigerant molecules in ducting and plenums. Industrial sniffer systems sometimes use pressurized helium because of the ease of helium's extremely small molecules in finding voids in seals, potting and welding joints.
Bursting and Leaking
Much pressure testing is safety-related, focused on determining maximum normal operating pressures, bursting pressures, and leakage pressures of devices such as gas and air storage tanks, propane tanks, and fuel tanks on space vehicles where the scale of consequences of the vessel bursting are obvious. With a propane vessel, both bursting and/or leaking can be immediately life-threatening.
Functionality
Tires fail to function as intended either in the event of a blowout or a leak. Here the pressure testing consists of measuring pressure with a tire pressure gauge periodically and under approximately the same conditions each time, like making sure that the test is always done at the same time of day.
Dangerous Leaks
Leaking chlorine tanks will require the mandatory evacuation of entire communities and towns under some conditions. Such substances as chlorine, pesticides, poisons, and other lethal chemicals require stringent and regular pressure testing of all components according to well validated and sanctioned testing procedures.
Tags: pressure testing, designed contain, equipment such, filled with, Pressure Test, Pressure Test Procedures