For most all your forest product applications, welded steel chains are your best chain choice. There is no other class of chain that offers a package of high strength, flexibility, ruggedness, precision, and durability equal to what is offered in welded steel chains. Along with a lower cost, welded steel chains are ideal for most conveyor applications with long or short runs, poor conditions, medium or high speeds and heavy loading. Adding some low cost features will pay high dividends in your operation, by giving you even better service and more value.
Reducing fatigue requires proper selection of steels as a means to improve fatigue life. We know that fatigue is probably the leading cause of steel failure. Simply stated, if we can improve resistance to failure, we can improve the life of the chain.
Unfortunately, when you look at a piece of steel, you can’t tell what grade of steel it is, or whether or not it was heat treated. Unless you have some metallurgical background, you really don’t know whether one steel is more fatigue resistance than another. You have to have a lot of faith and trust in the company you deal with to insure you are getting a fair deal.
This chain is normally used in the food processing industry, where conventional lubricated chains are restricted. It is generally found in viscerating tables or conveyors used in meat processing plants. Delrin or Acetal Bushed chain is ideal because it is self lubricating which is required in this environment.
The units are usually slat conveyors, with stainless steel slats bolted to the chain. The product never touches the chain. Instead, the product rides on the moving slat conveyor while the various disassembly operations are performed. The operating environment is usually in a cold and wet atmosphere.
Webster Delrin or Acetal Bushed Roller chain for conveyers is available in 4.040” pitch (S1113D) and 6.000” pitch (S1670D) and comes with K22 attachments every 2nd link. S1113D is widely used in pork processing while S1670D is used in beef processing. Refer to Webster Master Catalog #300 for detailed engineering information. This chain is excellent for use in wet, corrosive environments such as meat packing or food processing.
If I gave you a piece of wire and asked you to break it, you would probably move it back and forth rapidly between your fingers. You would feel it getting hot, and soon the wire would break. You have just experienced a fatigue failure. Fatigue is probably the most common cause of failure of any steel product, whether chain or any other mechanism that uses steel.
Individually all parts of a chain are important, but none as important as the chain pin. This is the heart and soul of chain, and will in most cases determine the life of the chain. Engineers like to say the pin “articulates around a sprocket,” which in my language means, the pin moves back and forth between two rigid parts – something like the wire held rigidly in your fingers. That creates a condition of fatigue that can lead to failure, or breakage.
So then, our problem is to find a way to reduce or minimize the possibility of a fatigue failure. Fatigue occurs by slow growth of a crack which usually begins at a weak point on the surface, or at a point where the loads are higher than elsewhere. (Engineers call this a “stress concentration” – they like to confuse us with big words.)
Welded steel chains usually have the designation, “WR” or “WH” preceding the chain size. The “WR” designation means the pins only are heat-treated. The “WH” designation means all the parts, sidebars, bushing and pins are heat-treated.