Change-out of HP cold recycle valve

[Onnie]

Hoi ,

Recently we changed out on a two stage compressor the HP cold recycle valve.The new one is faster. They also increased the CV of the valve from Cv 80 to 114. The valve has a double function.: control and anti-surge. We programmed the new curve in our automation system, but tuning is still a problem. Is the choice of a Cv charactiristic for a compressor. Operation envelope enzz.

Thank O.

 

[dcasto]

A faster valve? Do you mean you went from a linear to a quick open trim?

What do you mean, two functions? If your set point is away from the surge line, why would you need anti-surge.

Cv doesn't make any difference. If your process needs a Cv = 50, then a maximum of 80 or 110 doesn't matter unless you have a upset or startup case that requires 90, then the 80 won't work.

You said you put the curve in the atosystem, you mean the Cv vs the % travel? So EE may explian that one, but I don't see why it has anything to do with the control tuning.

Overall, you have a faster opening valve at the low end where one would expect to be for a antisurge. this means the loop must be slowed down because a small valve movement will make a huge change in flow when the valve first opens.

Rethink you needs and maybe you need a linear travel with a faster loop?

 

[PWRPLNT75]

Maybe try A linear travel?