Emerson Exchange 365

I am using DVC6200 positioners with low bleed relays in control service. The positioners are mounted on fairly large double acting piston actuators (flowserve size 100 actuators) where fast stroking speeds (1" per sec) have been specified. As such, booster relays have been installed to achieve the stroke rate.

The standard tune set has delivered very poor results for valve dynamic movement, so manual tuning is in progress. By screwing in the booster gain screws to about 1/4 open, and increasing gain to 12, some improvement is made, but unless the boosters fire, valve response to control changes of less than 4% is still very poor. 

I will be reducing booster gain screws more (1/8 turn) to try to get the boosters to fire on smaller control changes, but suspect that I will still be stuck with very poor dynamics when the valve is modulating.  Should I be replacing the log gain relays in the DVCs with standard relays, and if so, can I expect much improvement.

in that the stroke speed requirment is more than necessary for many of the valves, I am considering removing the boosters and living with slower response, but hopefully better modulating performance.

I cant find the maximum air output from the low bleed relay to understand how much less air it is likely to move than the standard relay when in modulating service.

This is quite an urgent query, so any response would be greatly received.

JR