Control Valve Location 1

[CurlyJoe]

We’re laying out a glycol system with a pumped loop around an exchanger where fresh glycol will come into the pump suction side of the loop. (See attached diagram) Due to physical-layout constraints, we put the valve in Location C, but will it work there? My concern is air leaking up past the control valve and draining that line.

There’s plenty of space to put the valve at Location B, but the valve may not work there for the same reasons I’m concerned about Location C.

Location A would require some piping rework, but if that’s our best chance of controlling the temperature in this loop, then that’s what we’ll have to do.

 

[pennpiper]

First of all there is a big difference between what is shown on a P&ID and where you place the valve in the real physical world. Those positions (A, B & C) are all schematic and mean almost nothing relative to up or down.

The Control Valve is either a LCV (Level) or it is a FCV (Flow) or a PCV (Pressure) or TCV (Temperature)Control Valve. You did not say which,but it can be located in the "A" position for all cases and the high point "Seal Leg" will still work.

If I (we) had more information we might be able to determine whether you even need the "Seal Leg" at all. Why is it there?

 

[CurlyJoe]

Thanks much for the sanity check on Location A.

To answer your question, we're controlling temperature in the loop (by controlling flow out of it). The header feeding the loop will force cold glycol in as the TCV opens to bleed off the excess.

About the seal leg: We inherited this piping layout and the best we can gather, the seal leg was unintentional. Methinks the designer took the pipe up to the rack and down through the chase for giggles. I'd not have had call to post the question if not for the "seal leg."

At this point, I just want to locate the TCV to give this thing a shot at working.

 

[StoneCold]

Curly Joe
I assume that you have a check valve where you are returning to the suction of the pump, also you might need to have a restriction between the point where you dump out of the loop and the return to pump suction so that you have enough pressure to force liquid out of the loop. Just an added thought that is not on your sketch.

Regards
StoneCold

 

[CurlyJoe]

Yes, there is a check valve in the loop on the suction side of the pump.

Thanks for the orifice suggestion. I'm to get a globe valve in that line to keep the pump from running all the way out, but an orifice may be a better solution.