Pressure vessels are storage tanks or vessels that have been designed to operate at pressures greater than normal (generally above 15 p.s.i.g). Common materials held and maintained by pressure vessels include air, water, nitrogen, refrigerants (like Freon), ammonia, propane, and reactor fuels. Due to their pressurizing capabilities, they are often used to store chemicals and elements that can change states (notably gases that have been liquidized). In most cases, the walls of pressure vessels are thicker than normal tanks providing greater protection when in use with hazardous or explosive chemicals.
Pressure vessels are used in a variety of industries including chemical, cosmetics, food and beverage, oil/ fuel, paper and pulp, pharmaceutical and plastic processing, and power generation.
Most pressure vessels have built-in temperature control characteristics (heating only, cooling only or both heating and cooling) in addition to pressurizing capabilities. This can help to keep volatile chemicals in relatively inert states, or when necessary, change the state of the material to prepare it for transportation or use in a connected system.
Pressure vessels with temperature controls have gauges to allow for reading of internal pressures and temperatures. These gauges are available with a variety of end connections, levels of accuracy, materials of construction, and pressure ranges.
Pressure sources for pressure vessels are limited to the maximum allowable working pressure of the lowest rated system component. When sources cannot be limited, the use of pressure-relief devices is required. Common relief devices include a spring-loaded relief valves and rupture disc assemblies. Additional connections, such as audible alarms and computer regulation are often necessary in systems where pressure relief is necessary, especially if the chemical being contained is hazardous in nature.