1.4.4 Poly-Steel Chain (PC)
Transmission, conveyance: Lube-free type. Food or medicine production
Poly-Steel (PC) Chains are lube-free chains used in food or medicine production. PC Chains can be used in power-transmission applications, and, with the addition of attachments on the outer plates, as conveyors. (See Figure 1.14.)
Figure 1.14 Poly-Steel Chain
Construction and Features
The chains are a construction of outer links (outer plates and pins) made of SS304, and inner links made of engineered plastic. There are no rollers. Features are shown below.
- Inner links are made of a self-lubricating material; therefore, the chains do not require lubrication. The wear resistance of these chains is higher than that of Stainless Steel Roller Chains without lubrication (Figure 1.15).
- Because the inner link is made of plastic, the noise caused by engagement with the sprocket is lower (about 5 dB lower than Standard Roller Chain).
- PC Chain is very light; about half that of Standard Roller Chains.
- There are five sizes for this series: Numbers 25, 35, 40, 50, and 60. The maximum allowable tension varies from 0.08 to 0.88 kN.
Standard sprockets are used. The three major sizes have the same dimensions as ANSI Roller Chain; Numbers 25 and 35 are slightly wider. In corrosive conditions, carbon steel sprockets may corrode and contaminate the application. Use stainless steel or, at slow speeds (less than 70 m/min.), use engineered plastic sprockets.
Figure 1.15 Stainless Steel Chain Versus Poly-Steel Chain
Selection and Handling
- One of the advantages of Stainless Steel Drive Chain is its high ratio between tensile strength and maximum allowable tension. Even if tension is high at the moment of starting, it will not break if the start-up is infrequent. The ratio between tensile strength and maximum allowable tension for Poly-Steel Chain, however, is low. There is a huge difference in the Young's ratio between steel and plastic. Almost all of the shock load is absorbed by the engineered plastic inner link. This means you need to take care when selecting Poly-Steel Chain. If Poly-Steel Chain is selected the same way as standard chain, breakage may occur. When selecting Poly-Steel Chain, the maximum tension—including inertia shock—must be considered to get satisfactory results.
- These chains are suitable for splash applications, but they should not be submerged in water or other liquids. The ideal environment is indoors where rusting must be avoided.
- The allowable tension of this series is almost the same as Stainless Steel Roller Chains (SS series.)
- An offset link is not available for Poly-Steel Chain. An even number of links must be used.
Application Series: PC-SY
Because of the titanium outer links and special engineered plastic inner links, SY series chains do not corrode in most chemicals, including hydrochloric and sulfuric acid. The allowable tension is about half that of Poly-Steel Chains. This is a nonmagnetic type of chain.
Manufacturers are working to increase both the tensile strength and the maximum allowable tension.