Adjustable Pressure Relief Valves: Tips and Recommendations for Choosing the Best Option
When installing an adjustable pressure relief valve, the safety of the infrastructure and people is at stake. There are many models available in the market, but we must pay special attention to ensure that our investment meets our needs. Additionally, taking care of the location where it will be installed is also an important detail to consider.
Pressure relief valves protect vessels, piping systems, and equipment from overpressure, which, if left uncontrolled, can not only damage a system but also cause an explosion. Because these valves play such a crucial role, it is absolutely essential to choose the best option to achieve optimal performance of the installation.
6 Factors to Consider When Choosing an Adjustable Pressure Relief Valve
There are six key elements to consider when selecting a valve that best suits the desired outcomes.
The set pressure is the pressure at which a safety or relief valve opens. The set pressure of the valve should not exceed the maximum allowable working pressure (MAWP) of the boiler or other pressure vessel.
This means the valve should open at zero pressure below the equipment’s MAWP. In turn, the equipment’s MAWP should be at least 10% higher than the highest expected operating pressure under normal circumstances.
Temperature affects the volume and viscosity of the gas or liquid flowing through the system. This factor also helps determine the ideal valve construction material. For example, steel valves can withstand higher operating temperatures than valves made of bronze or iron. Both operating temperature and relief temperature should be taken into account.
La presión en el lado de salida de la válvula de alivio se conoce como contrapresión, y es el resultado de la presión en el equipo de descarga, que puede ser constante o variable. Esta situación puede afectar al ajuste de la presión de la válvula aguas arriba y, por lo tanto, provocar que se abra de manera repentina dañando la válvula.
Para instalaciones con contrapresión variable, las válvulas deben seleccionarse de modo que la contrapresión no exceda el 10% de la presión de ajuste de la válvula. En las instalaciones con unos niveles de contrapresión que se mantienen constantes puede ser necesaria una válvula operada por piloto o una válvula sellada con fuelle.
The pressure on the outlet side of the relief valve is known as backpressure, and it is the result of the pressure in the discharge equipment, which can be constant or variable. This situation can affect the upstream pressure setting of the valve and may cause it to open suddenly, damaging the valve.
For installations with variable backpressure, valves should be selected so that the backpressure does not exceed 10% of the valve’s set pressure. In installations with constant backpressure levels, a pilot-operated valve or a bellows-sealed valve may be necessary.
Different types of valves are required for different service types: steam, air, gas, etc. Similarly, the material used to construct the valve will need to be adapted. For example, stainless steel valves are preferred for corrosive media.
Both relief valves and safety valves must be able to relieve pressure with a certain capacity, which is determined based on factors such as the valve’s geometry, discharge area, or medium temperature.
The required capacity is established by the applicable code. It is usually expressed in: LBS/HR – pounds per hour (steam flow); SCFM – standard cubic feet per minute (air or gas flow); GPM – gallons per minute (liquid flow). When selecting and sizing safety or relief valves, it is necessary to consider these basic factors. You should also consider the physical dimensions of the equipment and the plant, as well as other factors related to the operating environment of the valve.
The adjustable pressure relief valve should be installed in a vertical position and as close as possible to the protected equipment or piping. If not installed close enough, the total pressure drop between the piping and the inlet of the safety valve should not exceed 3% of the valve’s constant pressure value or 1/3 of the maximum allowable open/closed pressure difference (whichever is smaller).
In practice, it is possible to reduce the total pressure drop in the piping by expanding the valve’s inlet diameter and reducing the number of elbows, adopting a long-radius elbow.
Contact Valfonta and receive the personalized advice you need
At Valfonta, we have over 50 years of experience in the design and manufacturing of valves for all types of fluid systems. We have extensive expertise that we provide to our clients, offering advice regarding the most suitable products for each case.
If you want to contact our sales team, we invite you to write to us at our email firstname.lastname@example.org or through the form on our website. Alternatively, you can also call us at our phone number (+34) 93 3720888. We look forward to hearing from you!
Valfonta has been a beneficiary of the European Regional Development Fund, whose objective is to improve the use and quality of information and communication technologies and access to them. Thanks to this, they have been able to implement a production and plant control system (MES system). This action took place during 2022. For this purpose, they have received the support of the Industry 4.0 program of the Barcelona Chamber of Commerce.
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