# Air pressure vessel safety valve size

• guideonl
In summary, the conversation discusses determining the size of a safety valve for an air pressure vessel and the procedure for calculating it. It also raises the question of the relationship between the discharge capacity of the safety valve and the flow capacity of a compression unit. The conversation concludes with a statement about the importance of considering mass flow and volume flow in determining the size of the valve.
guideonl
Hi everyone,

I have to determine the size of safety valve for an air pressure vessel. I found in ASME and BS 5500 a procedure to calculate the size of safety valve, which relates the mass flow capacity to the: pressure, temprature, discharge area, s.v coefficient, and air parameters. This can be helpfull if the flow capacity is known, so you can get the discharge area (valve size). But if the flow capacity is unknown (such in case manufacturing perss. vessels without compression units).
The next question is there any relation between the discharge capacity of the s.v to the compression unit flow capacity? I suppose yes, but is it equal/higher? how much?

Thank you,
Guideon

If it is all air, no liquid, then mass flow out = mass flow in. If there is zero mass flow in, then even a small valve is able to make the pressure start reducing immediately.

If temperature in the tank is increasing then use volume flow out = volume flow in.

## 1. What is an air pressure vessel safety valve and why is it important?

An air pressure vessel safety valve is a device used to release excess pressure from a closed system, such as a container or tank, in order to prevent it from exploding or causing damage. It is important because it helps maintain the integrity and safety of the vessel by regulating the pressure inside.

## 2. How do I determine the correct size for a safety valve for my specific air pressure vessel?

The size of a safety valve is determined by the maximum pressure and capacity of the vessel it is being used for. It is important to consult with a professional engineer or refer to the manufacturer's guidelines to ensure the correct size is chosen.

## 3. Can a safety valve be adjusted or modified to fit a larger or smaller vessel?

No, safety valves should not be adjusted or modified in any way. They are designed and manufactured for specific pressure and capacity requirements and altering them can compromise their effectiveness and safety.

## 4. How often should safety valves be inspected and replaced?

Safety valves should be inspected regularly, at least once a year, to ensure they are functioning properly and within the required pressure range. If any signs of damage or wear are present, the valve should be replaced immediately to maintain safety and prevent potential accidents.

## 5. Are there any regulations or standards for air pressure vessel safety valves?

Yes, there are various national and international standards that regulate the design, installation, and use of safety valves for air pressure vessels. These standards include ASME, API, ISO, and others, and it is important to comply with these regulations to ensure the safety and effectiveness of the valve.

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