Failure of Valves 1

[jignesh1210us]

I have installed SS 316 Ball Valve at the entry of Filter Press & at the end of recirculation line. The pipeline is having pressure of about 4 Kg/cm2. It is used for Cu Slurry solution with density of 1.5. After Valve there is a bend to redirect the solution of recirculation line in the Vessel / reactor. The difficulty is that the frequency of Valve failure and that bend is too much in recirculation line. Can any one suggest ? Is there any problem with the layout ? All MOC of pipeline are SS 316, Sch#40 and Pump is Warman Slurry pump 4/3 CCAH.

 

[BigInch]

You forgot to post the layout diagram.

**********************
"The problem isn't working out the equation,
its finding the answer to the real question." BigInch

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[jignesh1210us]

Dear Sir,
Pls find herewith attached file of layout for your reference.

 

[rneill]

In what way is the valve failing ?

 

[jignesh1210us]

Valves are failing due to slurry velocity, erosions of the slurry. May be due to pressure. Present pressure is 4 Kg/cm2 which I think normal for warman pumps.

 

[jignesh1210us]

Due to Erosions , Velocity of slurry

 

[rneill]

I guess what I was getting as was more along the lines of ...

Are you seeing valve stems breaking, valves seat materials eroding away but the balls themselves are okay, or are you seeing erosion on the ball material itself, etc.

What is the physical problem or symptom that you experience that tells you the valve has failed. Have you taken any of the valves out and examined the internals to see exactly what is going on ?

 

[jignesh1210us]

Dear Sir,
We have inspected valves also. It is observed that 3" SS valve,which got damaged within two days after fixing in the recirculation line of Warman pump. The same kind of damage observed in PP valves also earlier. The teflon ring is the same as in SS & PP valves which once damaged, erodes the SS part very fast with the velocity of the slurry. We have checked the pressure is around 4 kgs/cm2 in the discharge line of the pump.
WE also have installed Pinch Valve but it's Sleeve is rupturing even in fully closed condition.

 

[rneill]

Flow disruptions in close proximity to the valve (e.g., the bend) could be creating turbulence which is contributing to erosion of valve components. Providing some straight pipe upstream and downstream of the valve may help minimize turbulence related erosion. I might try 5 diameters upstream and 3 to 5 diameters downstream.

SS material is also quite soft (as is teflon) and you might want to try and harden the valves against erosion.

SEATS: If you are having trouble with the teflon, can you find harder more resistant elastomers (perhaps PEEK) or could you consider a metal seated ball valve.

BALL: If you are currently using just bare SS, you could consider providing a hard wear resistant coating on the valve. Consult the manufacturers but options might include nitriding or electroless nickel coating. A heat treated low phosphorous electroless nickel coating would provide good wear resistance.

 

[micalbrch]

Do you use the valve at the entry of the filter press to control something (throttling)?. I can understand if you use it as a shut-off valve which is either completely closed or completely open. But to control the slurry flow into the filter press is a little bit strange for me to understand. But I'm not sure about the sketch you sent neither.

 

[jignesh1210us]

rneill : Sir, I think I will try to give some straight length in upstream and downstream of pipe. This looks like certainly beneficial. Thank you very much for your opinion.
micalbrch : Sir, this is on-off application. For Throttling the flow we are using CS Diapharm valve rubber coated which works satisfactorily. Thanks for your reply

 

[micalbrch]

jignesh: Feel free to ignore my question as it is not content of your initial request. But why do you throttle the flow of a centrifugal pump into a filter press? You do it with a diaphragm valve. I understand a filter press as a devive which consists of mutltiple chambers. The pressure increases due to the solids which remain in the filter elements. And with increasing pressure the flow must be reduced. At low pressure (4 kg/cm²) a perfect application for a Warman centrifugal - but without valve.

 

[jignesh1210us]

micalbrch
Dear Sir,
I think we have never thought regarding pumping into filter press without valve. But the obstruction is we have comman pump for two filter presses. One running and other standby.
please suggest.
Idea seems to be good but cant able to found suitable layout

 

[micalbrch]

jignesh: That's o.k. and common practice to have two filter presses which are fed by one pump as long as the pump does not feed both presses at the same time. So, there is no mistake in your operation. But still I do not think that you must throttle the flow. The pump will reduce its flow automatically when the presure increases. Try it without throttling the flow. The worst which can happen is that you have one batch of cake which is not perfectly dewatered.