THROAT AREA FLOW IN GLOBE VALVE 3

[skengg]

HELLO,
can anybody tell me what is the min. flow area require at throat section of globe valve body. like, if nomianal size of valve represent 100% area then how much minimum. area we can attain at throat section 60%,70% or 80% while keep flow abruption minimum.

 

[gerhardl]

Flow situation after a reduction, or before, inside the valve, is determined by actual flow, pressure, temperature and medium and the valve geometry, plus geometry after the valve. Flow turbulence/loss might be calculated approximaty based on earlier data from experience. Measuring and observing with the actual flow condition is the only sure way.

Other ways: 1. See what competitors have done. 2. Wich constructions are 'best selling' on the market. 3. Test with an actual valve with different adapted reductions mounted. 4. Better yet: Cut off valve ends and mount together with different end-redution pieces.

There is no general rule for a reduction size, but common practises for some different 'typical' applications. If you want to avoid too turbulent situations and cavitation (in or just after the valve) you must be conservative.

You might get some suggetions if you publish more details!

But way bother with large reductions? It will of course inflence and lower the production cost under some conditions, and more if number of valves is large.

PS. Reduction to 80% will in most (not all!)common cases be OK, lower has to be calculated/tested.

 

[skengg]

Thanx for advise, actually we are revising steel globe valve 8 inch cl-150 globe valve product to make cost effective.i am trying to reduce chest dia. for reduction in weight. by reducing chest dia. throat cross section section area also reduce. so i am trying to find any general information regarding throat area reduction.

 

[Nick_Gray_88]

Assuming this is a standard isolation valve?
The flow area wants to never drop below the pipeline area for the valve, except across the seat diameter which code rules allow down to 90%.
This way you ensure any fluid phenomena in the valve is across a replaceable component.

Chasing cost for the sake of chasing cost has lead the industry to the state it’s in now. Valves are safety critical, their function should be the #1 priority, then there are better ways to address cost after that

 

[LittleInch]

Its a globe valve he's talking about..

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Nick_Gray_88]

I got that bit…
But globe control, choke (globe pattern), isolation globe, SDNR pattern globe, they come in so many variations

 

[skengg]

i am talking about z flow pattern globe valve in which we have throat section area as min. flow area.

 

[bcd]

You can refer to API-602, which has tables of minimum flow area for standard and full port globe valves based on valve size and pressure class.

 

[Nick_Gray_88]

That’s true, but the location of where you put the smallest flow area in the valve will have a massive affect on the performance and service life of the installed valve.

If it is at the seat and you design the valve properly and select the right materials the valve could work for 30+ years, if you put it in the body it could last for a few months.

Personally I’ve seen examples where people have tried to pull size and weight out of the valve and as a consequence forgot the effects of the fluid going through the valve and has resulted in the body having holes in it…

 

[skengg]

yea i understand what you are saying.
our material specifications are as per standard. basically at chest throat section i try to reduce chest dia to make it cost effective. suppose you have cross sectional area at certain section of body is 60% of nominal dia. area and it gradually increase to 100%. do you think it can cause major issue in valve point of view. i know reducing area causes large pressure drop.