Wafer or Lug?
Wafer or Lug?
(OP)
Howdy,
I am new at picking valves. I don't know if I have enough information to pick the right one. I was asked to find quotes for an 8" butterfly valve, sour-trimmed, air actuated to be used in an abrasive service application. As I started researching them I have discovered some two types of bodies, the wafer and the lug. Does anyone have any recomendations?
Thanks,
Foxtrap
I am new at picking valves. I don't know if I have enough information to pick the right one. I was asked to find quotes for an 8" butterfly valve, sour-trimmed, air actuated to be used in an abrasive service application. As I started researching them I have discovered some two types of bodies, the wafer and the lug. Does anyone have any recomendations?
Thanks,
Foxtrap





RE: Wafer or Lug?
With respect to your application, the wafer valve is typically used between two raise flaced flanges and then all-thread is used to "sandwich" the butterfly valve between the flanges. The pressure of the nuts on the backside of the flange squeeze the gaskets into the face of the body and hold it in place. This is a common installation. The lugged version has drilled and tapped, or threaded ports that would match the bolt circle of the mating flange, thus allowing the use of a bolt to hold the valve in place. This is typically used in whats called an end of line servive, where you might want to isolate a pump or piece of equipment. This configuration allows you to remove the downstream flange and leave the upstream flange attached to the butterfly valve and isolating the pressure in the line.
Bottom line, if you want to be able to remove one of the flanges and retain pressure upstream, you need a lugged version.
Sour trim and abrasive service, need special attention (NACE) and hard facing on disc edge and seating. In some cases, you may need hardened body and sealed bearings to keep contaminants out of the bearings.
Hope this helps.
Bob
RE: Wafer or Lug?
RE: Wafer or Lug?
RE: Wafer or Lug?
RE: Wafer or Lug?
Geosmith: Why is a triple offset valve bad for abrasize and sour service?
Is there any more things I should be taking into account?
Thanks for your help to far?
RE: Wafer or Lug?
if You use tripple-offset metal-seated design (there are many discussions about that within this site, such as thread408-135872, thread408-126483 and others...), in addition to the sealed bearings and the horyzontal installation already mentioned, I'd suggest to make sure - if possible - that the valve is installed with the "flat face" of the conical seat below and the "inclined face" above (so that the possible solid particles accumulation may be removed more easily by the opening and closing movements of the valve disc itself...).
A solid seal ring (if the sealing element is on the disc) in a properly hardened or coated material may also be useful.
Hope this helps, 'NGL
RE: Wafer or Lug?
Butterfly valves in abrasive slurries can be great or they can be a disaster. The original rubber-lined butterfly valves were developed for cement dust. A cast-iron vane and a rubber liner lasts pretty well in that application. There are also rubber-encapsulated vanes to protect against abrasion. They make tires out of rubber...abrasion resistance is one of the primary reasons. Automotive brakes are made of cast iron for the same reason. The best trick for ruber-lined valve in abrasives is to undercut the vane: i.e. to reduce slightly the diameter of the vane, so that the vane does not grind grit against the seat with ans much force as a standard-fit valve would.
What is the temperature of your application?
What is the flowrate in your application/line-size/velocity?
High-performance (double-offset) valves are not as successful in abrasive services as symmetrical butterflies. The seating surface on an HP valve is narrow and must be polished. Turning the vane with the finely-polished edge facing directly into the abrasive flow results in the finely-polished surface not being there for you when you need the valve to shut off. The seats are usually convoluted to be process-energized. Packing the convolutions with abrasive fines does not contribute to their successful functioning.
Triple-offset valves seat without wiping action, so they tend to trap chunks between teh vane and seating surface. There is an active sealing member in most TO valves (One MFR calls it a lamellar ring) , and the crevice between the active sealing member and its holder can pack with fines. Again, if this gets chewed up in the open position, the valve will leak when you try to close it.
If your slurry temperature is compatible with elastomers, use a rubber-lined valve.
Try to keep the velocity between the values where the particles drop out, and an upper limit of around 12 FPS.
Earlier advice about having the stem horizontal is valid. ALSO put the actuator on the left side (looking downstream). Actuators customarily open CCW, so this installation will push back/dislodge/flush the settled layer of sludge at the bottom of the line as the valve opens.
One other trick is to put a 1" thick steel plate in the pipe upstream of the valve, in the same plane as the open vane. This will work like an inertial cleaner, deflecting the larger chunks and allowing the open vane to stay in its protective "wake". This will protect the LE of the vane and help extend the life of the valve. It needs to be as close as possible to the valve, but make sure you can get the vane completely open.
If the service is too hot for elastomers, think about a ceramic ball valve instead.
RE: Wafer or Lug?
I unfortuately I wasn't made familar with the application except a few details, the ones forementioned and that it is Ø8" and should have class 150 flanges (or BC).
Thanks for install advice. I probably would have missed the horizontal installation.
RE: Wafer or Lug?
RE: Wafer or Lug?
I don't understand the last trick that you mentioned? How to put the 1" thick plate in front of the valve. What is the meaning of vane? Why it can extend the life of the valve? Thanks in advance.
RE: Wafer or Lug?
Interesting idea.
rmw
RE: Wafer or Lug?
Thanks for clarifying what I had said, rmw.
Still Foxtrap could be a LOT more explicit about his application. Process ladings, chunk size, pressures, temperatures, flowrates. Whether he needs on-off or modulating control. The biggest difference between whether he needs a $400 rubber seated butterfly valve or a $10000 ceramic ball valve is about 150 degrees in his process conditions.
Pinch valves can be useful for chunky slurries, knife-gate valves can be great for stringy slurries, but where one works the other would likely be awful.
RE: Wafer or Lug?
I do apologize for being quite vague in my application description but that is mostly due to the fact I was unequipped to ask the questions I needed to know from the client before finding a valve to recommend.
I was looking for help in the recommendation but also an idea of what are the factors involved specifying a valve. What is a pinch valve?
Foxtrap
PS: "Her" application...
RE: Wafer or Lug?
John
RE: Wafer or Lug?