Outlet pressure at PSV

[yldrmkara]

Hi Everyone,

Firsly i am sorry for my english but i try to explain what i say.

PSV s normal Sprig Loeaded and convectional
1 1/2" 1500# to 2" 300#
PSV Set Pressure 180 Bar
Operatioan Pressure 145 Bar
PSV On the Pump
Pump is the Positive Deplacment Pump ( Piston Type )
PSV Outlet connection to the Pump Inlet.

The Question is below

when the PSV opens fully, what is the pressure that occurs at the time of exit ( End point of the outlet ? Does this pressure affect the Pump inlet pressure? and how can we calculate it or standars are saying some think about that ?

2. Question:

This system has a lat of vibration, how is the affact vibration and any standart definition of vibration range ?

3. Question

Generally, PSV Disc and Nozzle surface are rubbing each other and also when the PSV open that time some of dirt element mayme effect schratches on the surface and theese surface are damaged ? Am i right ?

Thans a lot

 

[Latexman]

1. The pressure at one point is equal. So, where the end point of outlet connects to the inlet, they are at the same pressure. The pressure at the PSV outlet flange is the backpressure of the flow in the outlet line plus/minus any hydrostatic pressure due to elevation.
2. Excessive vibration is not good. Fatigue failure may occur after some time.
3. Depending on the hardness of the dirt compared to the metal surfaces, it may scratch.

Good Luck,
Latexman
Pats' Pub's Proprietor

 

[georgeverghese]

There was a thumb rule some one posted on E-tips a few weeks ago, and it apparently is from some Russian standard: "In pulsating pd pump applications, PSV set pressure should be at least 40% higher than max normal operating pressure". All things considered, would tend to accept this margin as being ideal as it minimises dependence on unreliable pulsation dampeners and other attenuating effects process and mechanical engineers are eager to take credit for in an attempt to reduce CAPEX. This thumb rule is clearly breached in your configuration and would be viewed as being operationally troublesome (only 25% margin).

 

[The Obturator]

Regarding the seating. Dependant on the actual vibrations, fluid/particles/dirt etc., it has often been recommended to use soft seats.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

 

[yldrmkara]

Thanks all for reply.

Actually i cant find anythink for outlet pressure of the PSV but i see one think. i want to explain below

PSV 1 1/2" inlet Flange 1500# to outlet 3" 300# , that time i can easly say max allowable pressure at the end point of outlet flange is look around 50 bar.

And when the PSV open, The incoming pressurized liquid hits many points inside the disc surface and exits by losing its pressure. Because of that many manufacturer give outlet flange pound less than inlet flange pound.

But how is the calculate that, how they know outlet line become 3" 300# or have any standart ?

 

[The Obturator]

The PRV manufacturers are offering you 300# rated outlet because they are following API-526. ie., for a 1500' inlet the outlet is always 300# (smaller sizes).

You state that the outlet sees 50 bar, in which case a 300# outlet is necessary.

What you need to understand that there is a very large pressure drop from the set pressure at inlet to the outlet. In particular, the orifice area where the set pressure is the expands into the large volume of the body bowl. The pressure drop can be up to 90% of the set pressure.

Do you have variable back pressure? I note youhave stated you have a conventional spring loaded PRV.

Per ISO-4126, only the term Safety Valve is used regardless of application or design.

 

[yldrmkara]

Hi Sir ,

What you need to understand that there is a very large pressure drop from the set pressure at inlet to the outlet. In particular, the orifice area where the set pressure is the expands into the large volume of the body bowl. The pressure drop can be up to 90% of the set pressure.

Actually i absolutley agree with you, i said before PSV outlet line connection Pump inlet Line and pump is pd. Pump operation pressure 147 bar. At this point when the psv leakage , that leakage liquid going to the pump inlet and possitive effect to suction bar. how much the effect ? its around 10 bar or 5 bar its not important because 147 bar + 10 bar = 157 bar and this pressure can not open the PSV, but if effect bar is 50 bar that time our psv will open and the system into the cirle.

Yes ;
bulit-up back pressure 6,1 bar.
Superimpossed back pressure 0,7 bar
Conventional Spring Loaded Relief Valve