Pump Automatic Recirculation Valve

[Scotsinst]

Yarway (Tyco) and others make an automatic recirculation valve (ARC) for automatic pump spillback when the flow falls to the pump minimum required spillback rate.
I am reluctant to specify this type of spillback because I have had no experience with it. Some of our systems require long term controlled spillback, so on-off control is not acceptable.
Is there anyone in who can share good or bad experience with this equipment?
Anyone using an ARC on a high head pump(>2000 psig discharge pressure (140 kg/cm2(g))?

 

[hacksaw]

They (ARV) work just as claimed and hard to beat.

HP flow restrictors (older method) also work if you can afford the wasted energy. You pump manufacturer generally can advise you. There are some cases where a permanent recycle is not desireable.

 

[TD2K]

We had them on our BFW pumps though we were running much lower discharge pressures than you were, 700 psig or so.

They were trouble free. One think I would want to look into is how they handle cavitation. I would think for BFW being let down from 2000 psig, cavitation within the valve is going to be a real problem. I would get some references from them for similar applications and talk to the users to satisfy myself the valves have worked well. Make sure that you are comparing apples and apples, similar valve trim materials, similar water temperatures, outlet pressures, dPs, etc.

 

[Scotsinst]

Thanks for the feedback. I know of problems (15 years ago) with Yarway Turbo-cascade multi-step valves in high-pressure BFW spillback service. They only lasted a year or two and we replaced them all with Masoneilan Lincoln Logs (78200) with good results.
I am therefore not really keen to experiment with a multi-step ARC made by Yarway. Since, in the product bulletin they include a "backpressure" regulator in the spillback line it seems to indicate that the multi-step trim in the ARC cannot eliminate cavitation. Our current design uses Masoneilan Lincoln Log or Fisher valve with DST trim for high pressure pump spillback, with no backpressure regulator of course.
As far as the comment about it not being desirable to operate on constant spillback. The pump has a minimum spillback flowrate which may be 30% of rated flow but also a minimum continuous flowrate where there is no pump damage. On high-head multi-stage pumps the minimum continuous spillback flowrate may be 90% of rated. For long-term turndown feed rates a continuous spillback is therefore required.

 

[TerryOsser]

Try

http://www.blackhall.co.uk/ARV.htm

Its a better product.

 

[TD2K]

We had Lincoln log recycle valves on booster and main injection water pumps on a facility up on the North Slope of Alaska. They recycled water from essentially 3000 psig back to essentially atmospheric, water temperature was about 140F to 160F I believe.

There were a lot of problems with the valves wearing out, parts were expensive and were long lead items. We tried out a new valve just before I left and it apparently worked well (well, after we put in the right trim. There were LOTS of discussions whether to try it and finally, the field people ordered it when I was gone. The valve body was 6" so we needed a 6" trim right? Talk about oversized). The valve wasn't anything fancy, just a multi orifice type trim (the plug exposed more orifices as needed) and lots and lots of metal in that puppy. But, the users we talked to were real happy with its service. Now, if I can remember who made that sucker?

 

[saxon]

Scotinst, There are three methods employed to maintain minimum pump flow.

1. sized orifice providing continous min. flow.
2. on/off valve controlled by inst. signal utilizing either flow or pressure.
3. use of an ARC valve.

Method one is the cheapest solution initially, but when you figure the cost wasted energy over the loong term it becomes the most expensive. Method two is the most expensive initially and must be constantly calibrated and maintained. Method three, has a high initial cost, but overall this cost drops over time because no energy is wasted and calibraton and maintanence is not required.

We use these types of valves extensively in services with widely varying flow rates that at times may drop below the pumps required minimum flow. I know of cases where this type of valve was installed twenty years ago and are still operational today. I can't say the same about the pump seals, but that's another issue.

Hope this helps.
saxon

 

[davefitz]

for long term operation in a bypass mode, one may consider a variable speed drive or variable speed hydraulic coupling on the pump with recirc ontrol valve , instead of constant speed with ARC , depending on the system's flow vs required pressure characteristic. On-off or 2 speed pumps can also be justified in some applications.

If operating cost is of no concern, the ARC is the most reliable.

 

[snarayan]

I may be very late to comment but still I would recommend anyone to approach CCI valve (Control Components Inc. California Tel : 01-949-858-1877) for a guaranteed trouble free operation. visit : ccivalve.com

 

[pablo02]

I worked at a plant that utilized 2 Fisher valves (BFP about 2300 psig) in parallel -- they were setup to operate also in parallel (controls) [DCS tech was a great programmer but not too familiar with operating conditions] -- they complained bitterly about the plug, seat and trim wearing out frequently and it was expensive to replace... I finally convinced them their problem was in their control method and not the valves themselves -- at low loads and start-ups when the boiler make-up was reduced and both valves were in service, the plugs would only open a few thousands of an inch - the water was literally cutting the metal under these conditions: I got them to bias one valve out of service (until the unit was at about 30% load) so that the valve in service would open further and reduce the velocity of the water flowing through the valve...

we also found out that our chemical injections (I think it was the oxygen scavenger, it's been awhile) also attacked the carrier metal for stellite -- carbon steel would outlast the stellite trim on these valves...

my thoughts are that there are other conditions that may create problems that should be considered before condemning the valves...