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In a typical propane refrigeration loop (e.g. in photo), there is always an accumulator or surge vessel. There is no level control on this vessel...so how does the level in the vessel get maintained. The expansion valve usually a level control valve maintains level in chiller. Does that valve...

In a typical fractionation column with a total condenser, does the liquid going to the reflux drum remain fully in the saturated liquid phase? Is any vapor formed in the reflux drum? Is the reflux drum usually just an accumulator or does it also act as a separator? If the reflux drum has a boot...

I am trying to understand if I can send a hydrocarbon product to an API 650 tank which has max internal design of 2.5 psig. Product is from Inlet Separator at 50 psig. Now when I model it I see that the vapor pressure of liquid from Separator is 50 psig. When I take it across LCV to the tank...

@little inch - thanks, however, I am still a bit confused over selecting a high selector From your earlier comment "But if you really want to do that then take both position signals and stick them into a high selector block and the valve will open more based on either lower flow than your set...

Thanks little inch. What you said makes sense. I guess my only concern is that since we have a fail open and air to close valve, should we actually have a low selector instead of high selector? Since in case of blocked flow for e.g, downstream of pump, the head/pressure increases and flow...

@LittleInch - yes both PC and FC are for min flow protection. In case of low flow and high prssure..the control valve should open. Valve is fail open and air to close. So when flow decrease, controller should send low signal to valve maybe ..to cause it to open? ..for pressure increase the valve...

Hi, I am trying to understand use of high and low selector in process control For e.g. in the attach photo, can we use high selector for pressure and flow controller to control min. flow recycle control valve? Should we use high or low selector? Should PC and FC be direct acting or reverse...

How does VFD speed control actually work in Reciprocating/Positive Displacement Compressor? In case of reciprocating compressor, how does capacity control work with speed control. Since we don’t really measure capacity / flow, is the speed control done based on pressure? For example lets...

Thank you for your answers @little inch @snickster

Snickster - yes this pressure vessel is to remove any entrained oil. level control in this vessel is just to maintain an interface b/w oil and water. This pressure vessel will be full of liquid. Noted on ur point to design this vessel for the max op pressure of the upstream separator. But I am...

thanks snickster, but incase i put a level control on water pressure vessel with continuous flow coming in and going out...will that help keep pressure at 15 psig...in this case there will be constant flow into and out of vessel. the water pressure vessel will be fully filled with level control...

@little inch - thanks very much for your response. much appreciated.

@little inch - thanks for your answer

thanks, horacio. Since the fluid is essentially water, what will be there in vapor space in this case? Would the pressure ever rise to 15 psig, even if a pressure control valve is there on the venting line??

Thanks 1503-44, In case, The LCV is sized for Pinlet = 50 psig and Poutlet = 15 psig. The pressure vessel for water does not have any blanketing or pressure control. Now in real world case, what will happen…will the pressure vessel pressure increase and rise to 15 psig…when it rises to 15 psig...

I have a pump that is pumping stable product to a tank. There is no blanketing on the tank and it is not vented to the atmosphere. What will be the pressure in the tank? Will it be due to vapor pressure of the liquid. Since vapor pressure is below atmospheric..will there be vapor in the tank at...

I have a oil water separator operating at 50 psig with a level control for interface. Water flows out of the level control valve to a pressure vessel. The level control valve is sized for p inlet = 50 psig and p outlet = 15 psig. The water pressure vessel has no blanketing or any positive...

How flow change with pressure drop? If P1 at the inlet of pipe=50 psig &P2 at end of pipe is based on pr. drop and flow is x for e.g. Now if i put orifice in pipe due to more delta P should flow increase to > x since flow is proportional to delta P? Why by putting orifice then flow decrease???

In a low pr. flare system can a the flare ko operating pr. be kept at atmospheric? Since pr. at flare tip is atmospheric then how flare ko can be atmospheric? would it not be always higher than atmospheric due to backpressure? attachd...

Out of the tower is about 1680 barrel pressure of reservoir is 2000 psig pressure downstream of choke is about 1000 psig GOR is measured by flashing bottomhole sample to standard conditions (60 F 0 psig) it is a proper composition