Mick,
thats what has me stuck . As to how and where to use temp and pressure I have no clue ?
I've never done a NG site so this is all French to me.
I keep being told that a flow computer is only way to do this, but the old system that was in place only had DP, temp, psi, and plate size. So it can be done.
It definitely *can* be done, but you are going to need more than just dp, temp, psi, and plate size. You said earlier that a bristol babcock flow computer was being used, so I dont understand why you are saying it was being done with only those 4 parameters.
Either way here is a aga3 calc that someone built for contrologix. If you have logix5000 perhaps you can take a look at this and it will point you in the right direction on what you need to do.
http://forums.mrplc.com/index.php?showtopic=20910
I still stand by my comment that a flow computer is the right tool for this job.