Butterfly Valve Leaking 1

[zrasmusuperfan]

Hello, I am a recent grad and have been tasked with my first real application. I am working at a plant that uses river water for cooling, the problem is the water that is taken from the river is full of sand and debris. There are multiple butterfly valves that are 60" in diameter. The total throughput is around 250,000 gpm from 6 valves. The issue comes through lack of maintenance of the valves and sand working its way on the seal and damaging the bushing, causing the leak. It is a significant leak on each valve. I am a chemical engineer, meaning I understand butterfly valves, but I am not familiar with the intimate details. Is there a product out there that is injectable that could form the seal that is worn out? Is this something I should contact the valve manufacturer about, would that even be helpful? Other than routine maintenance is there anything that could be done to mitigate the problem. This has apparently been an issue for several years. If there are no practical solutions to the valve is it practical to install some type of drain valve in the system, so that in the event of the water being turned off, the sand from the water doesn't settle and get all over the floor and piping system? Perhaps there are even valves that are designed to handle such flows with minimal leaking. If I am being unclear, I apologize, and sorry for my ignorance, I am learning. I appreciate any input or guidance. Thanks have a nice day.

 

[ARHeit]

I've only been in the industry a couple years myself, but I would look up slurry valves and resilient seated butterfly valves. One of the grey beards on here will probably have better advice, but that's where I might start. But also if plant maintenance doesn't care to maintain them, things will just continue to break, so keep it cheap so replacement parts aren't a financial burden.

"Whether you think you can or think you can't - you're right." - Henry Ford

http://www.eng-tips.com/faqs.cfm?fid=376

 

[Compositepro]

Abandon the butterfly valves and permanently install inflating pipe plugs instead.

http://www.petersenproducts.com/129-0_pipe_plug.aspx

 

[ash9144]

I have seen butterflies work reasonably well in slurry service with glass reinforced ptfe seats. Regular ptfe seats would fail in short time in the application.

Of course there are valves which would prove more reliable in that service such as ball valves (which at 60" diam would be high dollar) or gate valves (which your operators would hate you for for years to come).

 

[DRWeig]

Similar to Compositepro's suggestion, I prefer pinch valves when marine life enters the picture.

http://www.flowrox.com/Products/3_1_pinch_valves

http://www.redvalve.com/rv/index.php/content/view/30/67/

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[Danlap]

Some additional info is still required to assess your problem.
Is the valve located below the sea (river) level and under the ground? And whether there are any some sort of strainer / sand trap before the valve? What is the seat material?

Your questions:
Is there a product out there that is injectable that could form the seal that is worn out? For 60" size, assuming it is always in process (wet), and operated in frequent basis. Then the answer is NO
Why -->
a. You don't have control where the sealant would end up stick onto, and it may stick on the parts that even not leaking.
b. giving that uncertainty, you cannot measure the sealant quantity (volume) required for this,
b. I never see 60" PTFE Lining, especially for River water. I presume the seat material is either NBR or EPDM (General name: RUBBER). Rubber could only be patched (economically) by means of heat with other rubber.
If it always in process (wet), you could not do such patching.

Is this something I should contact the valve manufacturer about, would that even be helpful?
On 99 percent cases NO. Manufacturer would have interest to repair the valve if you sent the valve to their workshop. If it is a new valve, then your warranty would be void, since no human being have control over whats passing through the valves. See disclaimer of the warranty carefully.

Other than routine maintenance is there anything that could be done to mitigate the problem?
--> Modify the line, ensure that minimum debris would pass the valve. By adding some strainer probably
--> Change your Plant's maintenance mindset:
[ul]
[li]A 30 percent open position butterfly valve, have almost the same flow with fully open butterfly valve[/li]
[li]Let say the valve is new, define the fully close position. During operation do not over torque (spanner with extension) the valve. It only pushing the sticked debris against the seat.[/li]
[li]Assuming that your system is atmospheric, there's a good chance that the seat is not broken. However debris tracing stick to seat. If this happen (indicated by valve cannot reach fully close), one of your bravest maintenance guy to go inside and see (clean) the surface before it got worse (hardened)[/li]
[li]There are 6 valves. If possible "kill" one every once a year for routine maintenance. Build your own statistical approach (Mean time between failure)[/li]
[/ul]


By far, big size non critical valve (for cooling water, etc.), Plant would prefer Butterfly valve. It is Ok, as long as they understand the risk (it is rubber - will deform by times, and will leak after several period).

Regards,
MR

Greenfield and Brownfield have one thing in common; Valve(s) is deemed to "run to fail" earlier shall compared to other equipments

 

[zrasmusuperfan]

Thank you all very much for the replies. I will be looking into the different types of valves to determine if it would be economical to change out the valve. I should have specified, these valves supply water that is being used for cooling.
As for Muktiadi's questions, the valves are located ~50 feet from the river, placed vertically near level to the intake, maybe 5-10 feet higher at a maximum. There are several screens to block the large debris, but the smallest screen size is 1/4" x 1/4". I'm not sure of the exact type of rubber the seat is made of, but that is something else I will look into. Talking to an operator, it appears the leak occurs at the shaft of the valve and not the seat. I think the issue is more that the sand gets beyond the packing material of the valve and leaks from near the stem and not the seat. But like I said earlier, I have seen butterfly valves and understand them, but I haven't actually seen the inside of this particular valve except on a drawing, and may very well be incorrect. This has all been really helpful.

 

[gerhardl]

In my opinion butterfly valves could, will and have been used for this application, but they would have to be in a suitable construction with references for such applications. The issue here seems to be the stem sealing material and construction. Constructional details and materials will and can differ vastly from supplier to supplier. (If the valve specification only say 'water' , chemically clean,free of particles, water will be assumed.)

Ask for valves suitable for river water with silt and sand. Also look for what valve suppliers for hydroelectric (river) plants can offer. I might suggest double eccentric BFL valves, of course as normally mounted with horizontal spindle, and/or completly rubber coated disc.

Another tip is to see if there is some simple way to modify the intake to give some of the more coarse grit and silt an opportunity to settle.

Any valve for this application will have a lifetime, even quench valves, which anyway will be costly and require large pipeline modifications. The existing plant has clarily not planned for maintenance. Check available valve-types and make a cost/lifetime analysis, including maintenance and downtime cost.

 

[LittleInch]

You need to try and find a sectional drawing of the particular valve to see what types of shaft seal you have. There is no real alternative once the shaft starts leaking to replacement of the shaft seal and possibly re-building the stem itself if this has become worn or scored.

Stem seals vary wildly from simple bushes chevron seals and o rings to packing and other means, which allow some sort of adjustment or modification. You need to see your particular ones to see where the problem might lie.

The orientation may also not be a preferable or acceptable for that particular valve unless specified. If it is in a vertical pipe but designed for horizontal there will be a lot of forces on the shaft not allowed for.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way