Valve for high pressure , high viscosity, highly abrasive enviroment 4

[washl]

Looking for suggests for an application i am working on. Our process involves using a high viscosity, highly abrasive material in which we control the flow using a pneumatic actuated metal seated ball valve. Initially we had issues with the valves failing to open (prior to switching to the metal seated valve). We operate at a pressure around 1500 psi and the valve cycles about once per minute. The issue that we are having now are leaks occuring at the stem. This occurs over a short period < 2mos. Are there any suggests on what i can try, valves, different packing, etc.?

 

[JimCasey]

Metal-seated ball valves such as VTI or Mogas are frequently used successfully in applications such as this. Ceramic valves >EXIST< for abrasive services.

You didn't say how hot the application is. If it's not too hot, and o-ring-sealed bushing below the packing helps to keep the grit out of the packing.

Thw pneumatic actuator is good because it probably does not put a side-load on the valve stem. Rack and pinion wont side-load the stem, nor will a scotch yoke. Make sure your mounting bracket and coupling are concentric anyway.

Live-loaded packing will help since it has a spring to keep compression on the packing as it wears. THe packing stackup should have a junk ring as the first element next to the process:usually this is a braided ring that can absorb grit instead of trying to seal around it.

 

[washl]

Thanks for the help. the temperature is ambient, and not a issue. This has a live loaded stem (Manufacturer is Sharpe Valve) but i will check on the o-ring sealed bushing and the junk ring. I haven't found a ceramic valve that will handle the pressures but will look at VTI and Mogas.

 

[FACS]

We used to use "Burkert" valves for abrasive diamond slurries.

The material does not come in contact with moving parts, and therefore does not foul up the components. The design uses a diaphram, made of polymer, that covers the orifice. The only contacting part is the diaphram on the orifice opening.

As you can imagine, diamond slurry is abrasive; we never had one clog or leak.

Charlie

http://www.facsco.com

 

[washl]

One other thing to note, we use 2" valves.

 

[FACS]

Have you looked a pneumatic pinch valves?

Basically a large rubber tube inside a housing. When air is applied between the tubing and the housing, it compresses the rubber tube and stops the flow.

I used them for waste drains for the abrasive slurries. They are found in the agriculture industry

Charlie

http://www.facsco.com

 

[JimCasey]

Charlie: A 1500 psi pinch valve?????

 

[bcd]

You specifically mention stem seal leaks as the problem. Many times, it's not the media or wear that causes the packing to repeatedly leak, but a lack of proper alignment between the valve and actuator. Check how the actuator is connected to the valve to see if there is any side loading. Do you have a slide-on type coupling or does it clamp on.

The symptom that indicates side loaiding is that you tighten the packing until it seals, then, a shorwhile later, the packing leaks again. Tighten the packing until is stops and roughly the same period, it leaks again. On and on it goes until there is no adjustment left. Also, look at the type of packing used. For high cycle ambient temperature, would recommend filled PTFE v-ring (chevron) type. It is common for small ball valves to simply use plastic washers, which are OK for occasional manual operation, but won't last as long when automated with side loading.

bcd

 

[ballvalveguy]

You might want to look at Argus or Gosco Valves. They both have stem guides to prevent side load on the packing. If you're cycling once a minute 24/7, that's approximately 500,000 times a year so it's very high cycle. Also, make sure that the valve and actuator are properly aligned as BCD says. In addition, Chesterton makes a packing set that is guaranteed for 1,000,000 cycles, so you may want to contact them too.

 

[Ashereng]

Have you considered a slab (or through conduit) gate valve?

The "seats" of a slab gate is perpendicular to the direction of flow, so it doesn't take as much abuse as the gate slide at 90 degress to flow when moving. Also, with a slab gate, there is no tradition gate valve's "seat" in which stuff can accumulate, allowing you to close the valve multiple cycles.

Also, what is "high viscosity"? And, what is "highly abraisive"? That may also help others give you a better suggestion.

"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?

 

[JLSeagull]

Consider hard surface materials to reduce the abrasion. Examples such as Deloro Stellite or other cobalt alloys may be helpful.

 

[ballvalveguy]

There are also diffusion processes (boriding)

http://www.bodycote.com

that will reduce the coefficient of friction and create a very hard surface (RC 97 if the Rockwell scale went that high). Arcuate cuts in the ball also reduces velocities when you first open the valve. You might also want to open the valve very quickly to reduce the amount of time the abrasive fluids are directed at the ball seat.

 

[caihui]

I agree with Ashereng to use through conduit is a good idea. Of course the metal seated ball valve is good way, and I don't think the packing leakage is not your choice wrong, I think it the valve have some problem. And the main problem is the stem not in the same axle of ball and below trunnion.

 

[washl]

All, Just catching up on the threads thanks for the help. Just a quick update on status.

We're still in the process of trying different packing to address the leakage of stems. Currently looking at UHMWPE material.

I've looked at other valve types but havent found a slab gate valve for the high pressures and room to fit in our application. I don't have the exact measurement for viscosity but it has the consistancy of a thick cement paste and is ceramic based.

The valve body is coated with Armaloy and the ball is stellite

 

[277Peter]

Dear Washl

The Serck Audco super H pressure balanced plug valve is worth considering for your abrasive service HP application the body internals can be hard faced for extra errosion protection.

follow the link below

http://www.flowserve.com/eim/v/inde...005e191eacRCRD&vgnextfmt=default&locale=en_US

 

[ballvalveguy]

Dear Washl,

UHMWPE can be used as a packing material, however, it is very limited on temperature. I would not recommend it if you see temperatures above 175F. My feeling is that you are more likely to be side loading the packing with misalignment of the valve and actuator, than having inferior packing materials. (look at BCD's comments) However, if you still feel that it is the packing, Chesterton offers a guarantee on their packing for 1,000,000 cycles. You can reach them at (800) 263-9140. They will tell you that it is extremely important not to overtighten the packing. For packing to work, you need to have a bit of movement or it won't seal properly.

Also take a look at

http://www.mclassvalves.com.

Gosco manufactures a valve that will work in this application.

 

[stanier]

I have successfully used Valve Technologies metal seated ball valves on 75% solids fly ash at 15000kPa.

Geoffrey D Stone FIMechE C.Eng;FIEAust CP Eng

http://www.waterhammer.bigblog.com.au

 

[washl]

The temp is less than 175F. From the Gosco website, the M-class looks promising. It seems to be a bit more robust than what i am currently using. My guess that comes at a significant cost. How does it handle high viscosity material (>250,000Cp)?

 

[ballvalveguy]

I'm not sure how Gosco would work on high viscocity material, but these high end companies (VTI, Mogas, Argus etc) should be able to solve your problem. You're right about the price though. Depending on what valve manufacturer you're using right now, you could be 3-4 times the price. You tend to get what you pay for, but on difficult applications like this, you need to look at cost of ownership. If you're replacing valves every 2 months, how much does that cost you in labour, lost production, safety?