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## How do you calculate Cv for steam valves?

The volume flow rate for liquids can be calculated by multiplying the fluid velocity times the flow area. Thus, Cv is numerically equal to the number of U.S. gallons of water at 60°F that will flow through the valve in one minute when the pressure differential across the valve is one pound per square inch.

## How do you size a safety relief valve?

Here are six factors that must be considered when selecting and sizing safety or pressure relief valves.

1. Connection size and type. The valve size must correspond to the size of the inlet and discharge piping.
2. Set pressure (PSIG)
3. Temperature.
4. Back pressure.
5. Service.
6. Required capacity.

Is higher Cv more flow?

The valve flow coefficient (Cv) is a number which represents a valve’s ability to pass flow. The bigger the Cv, the more flow a valve can pass with a given pressure drop.

How do I calculate what I need for a Cv?

The equation for calculating the valve flow coefficient is Cv = Q √ (SQ/P).

### How do I choose a steam control valve?

Sizing a control valve for a steam heat exchanger is a compromise between:

1. A smaller pressure drop that will minimise the size (and perhaps the cost) of the heat exchanger.
2. A larger pressure drop that allows the valve to apply effective and accurate control over the pressure and flowrate for most of its travel.

How do you choose a valve class?

Choose the right valve type. Every valve needs to perform one or more basic functions: Shut off flow. Divert flow….Starting with basic valve requirements will simplify and speed up valve selection:

1. Valve size and type.
2. Materials of construction.
3. Performance requirements.
4. Check valve specific requirements.
5. Maintenance planning.

How do I convert my Cv to GPM?

Multiply the square root of the pressure differential by the valve coefficient to calculate the flow in gallons per minute.

## Why is fire overpressure 21% for relief valve sizing?

But 10% or 21% itself is the optimum value more than MAWP (might be a little bit more or less) prevents the pressure relieving devices to be larger than normal size also allows the maximum operating pressure of the pressure vessel to be close enough to its design pressure.

How do you select valves?

1. Choose a valve type depending on your application.
2. Consider your fluid type (liquid or gas) and its characteristics to determine compatible valve materials.
3. Determine the temperature, pressure, and flow rate under which your valve will be operating.

What factors affect the size of a steam valve?

The design thickness and body jointing methods also have an effect. For example, an SG iron valve could have a PN16 rating and may also be Appendix 1 Saturated steam valve sizing chart

### Which type of steam valve is suitable for superheated steam?

The DN32 bodied valve will be suitable because the outlet velocity is less than 0.5 Mach allowed for superheated steam. The same procedure can be used to determine the conditions of the downstream steam for other upstream conditions.

### How does steam flow through a control valve?

Steam is supplied at a specific pressure to the upstream side of the control valve through which it passes to a heat exchanger, also operating at a specific pressure. Steam passes through the control valve and into the steam space of the equipment where it comes into contact with the heat transfer surfaces.

How do you reduce the velocity of steam in a steam valve?

It is good practice to keep the downstream steam velocity in the valve body typically below 150 m/s for saturated steam and 250 m/s for superheated steam. This can be achieved by increasing the valve body size, which will also reduce the velocity in the valve outlet and the likelihood of excess noise.