Liquids and other media flowing through valves during critical operating conditions can be affected by a number of hazards, including cavitation or flashing. The symptoms of valves that may be failing include an increase in noise emission, valve and pipe component erosion, or mechanical vibration in the valves and the connected pipelines. Under many critical applications, neglecting these signs can result in negative outcomes on plant performance, the costs of ownership, fugitive emissions, and even serious safety hazards. This why many safety valves are required to be made to ASME, ANSI, and/or API standards.
Unfortunately, it is a far too common practice for operators to select valves in a quick manner and think mostly of cost of the pipe, installation, and performance – rather than precluding them all for safety. This is often due to the pressure to maximize funds and allocate time during the phases of planning, bidding, and ordering components. Below we will share a few safety valves that should be considered and used in critical applications.
Safety valves were first put in use approximately 100 years ago on steam boilers during the industrial era. They were created with the sole purpose of keeping heating and other related pieces of equipment from exploding. Today, the sole purpose of these valves is to safeguard an operation from a number of hazards by opening or closing during certain conditions.
One such example is a pressure relief valve. They are designed to open when a certain pressure level is reached in order to release the pressure and prevent any damage to the system or surrounding area. They are commonly used in boilers, pressure vessels, and other related systems.
Valves in Gas/Vapor
Safety valves used in gas or vapor operations are often tailored to whichever chemical they are used with from ammonia to butane to natural gas and many others. A safety relief valve has to be capable of relieving the capacity of the connected compressor or compressors at operating pressure. The relief pressure may not be set higher than the maximum working pressure of any piece of equipment in the entire system. If the operating pressure is set below the valve’s relief pressure, it may start leaking and create a hazard. The Engineering Toolbox has a great formula for calculating the minimum discharge relief area of safety valves used in gas and vapor systems
Vacuum safety valves are used to prevent tank collapse when it is being emptied, in addition to clean in place or sterilization in place procedures. They are also installed on top of storage tanks to control fugitive emission losses that can result from handling flammable and hazardous petroleum products that produce vapor.
There are also vacuum valves known as breather valves, conservation vents, and safety vents that are specifically designed to protect process systems, tanks, and equipment from excessive pressure and vacuum forces.
Vacuum pressure safety valves, or VPSVs, are automatic valves that relieve the static pressure on a gas. The valves are used when the difference between the ambient pressure and the vessel pressure is low, negative, and close to atmospheric pressure.
For more on safety valves, check out these related articles.