back pressure regulator 3

[RNvd]

Hi guys,
Can some one expand on how to evaluate back pressure regulator set pressure and capacity requirement in a hot oil system which typically include a heater, expansion tank, system piping and all heat users or loops.

 

[sshep]

Is this back pressure regulator on the pad gas vent in the expansion tank?

 

[StoneCold]

The back pressure regulator I assume is at the end of the supply line. It needs to be sized so that if you have no users the back pressure regulator will be large enough to handle the flow. You might be better off with two in parallel at different set pressures. Both reguators only opening when you have no users.

 

[sshep]

If this backpressure regulator is supposed to act as a minimum flow for the pump and/or the fired heater, then consider a flow controller instead (will wind closed when not needed). This seems more common in my experience than a back pressure controller.

Using only the minimum hot oil flow through a hot oil system is an often unrecognized way to improve the efficiency at the heater by as much as a few %. While the heat demand at the process is the same, a fired heater will use less fuel to heat a smaller hot oil flow through a large delta-T than it will when a lot of high temperature hot oil is mixed with the cold stuff returning from the process (large flow through a small delta-T).

Just a thought. -sshep

 

[tkdhwjd]

I belive the system is a closed oil loop.
Hence the backpressure regulator is more like a flow controller, in this case. I would size it based on the two criteria:
1) Maximum design flowrate - CV must be large enough to manage this
2) Minimum design flowrate - Don't want to oversize the valve.

Depending upon how wide the gap is between these two design limits, you may have to use multiple valves or bypasses, etc.

Cheers