METHODS TO DIMINISH CONTROL VALVE CAVITATION :

Updated: May 23

Welcome to my new article, here in this article I will discuss methods to prevent or to diminish control valve cavitation.


Cavitation can cause a lot of damage to the valve body, thus increasing downtime and cost too. To reduce cavitation is a must.


In my other article, I have discussed problem occur in the control valve. Click on a link to know more about it.


Basically in this article, you will gain knowledge on how to reduce cavitation in the control valve, anti-cavitation valve, choked flow in the control valve, how to sustain cavitation in the control valve, how to curb control valve cavitation.


There are some methods by using them we can reduce cavitation.


1. By preventing Flashing

2. By sustaining the Flashing

3. Cushion with gas.

4. By reducing velocity


Let discuss each one by one,


1. By preventing Flashing


- We know that flashing can occur when pressure falls below vapor pressure and can never recover again.


- If we somehow manage not to fall vanacontracta pressure below vapor pressure for the liquid, which will prevent flashing and cavitation will never occur. so what to do?


- Use cavitation control valve trim.


- Select a valve type we have very low-pressure recovery rate.


- Decrease the liquid pressure which will help to reduce the vapor pressure


- Use anti-cavitation trim. so, it will provide multistage pressure drop as the fluid passes through the trim. Due to the use of multistage cavitation trim graph looks as shown in the below figure.


- One more way to reduce cavitation is to use cage- guided valve trim which contains multiple small holes which helps to reduce cavitation.


2. By sustaining the Flashing.


- Now, to sustain flashing means we have to use such a control valve with less pressure recovery rate due to that when control valve experience flashing pressure will never recover.

It will remain in flashing state.


- This option is not that good as flashing is also not good for control valve but it is better than cavitation.


- In the process, if we don't have many options we can go with this.


3. Caution with gas.


- In some process, non-reacting gas is injected into the liquid stream to provide cushioning within the cavitation region.


- The presence of a non-condensible gas bubble in the liquid system disturbs the microjet pathways, helping to dissipate energy before striking on the walls.


4. By reducing velocity


- One more way to reduce cavitation is to reduce velocity of flowing fluid. by reducing velocity pressure drop will reduce thus pressure will not drop below vapor pressure.

CALIBRATION

CONTROL VALVE

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