(303) 758-2728

Home > Problems Solved > Urethane O-ring Drive Belt

The Case of the Dying Drive Belts
Solved with a Urethane O-ring Belt

Like everyone, we get requests for quotes over the internet. It's not what we do as a general rule. We are more interesting in solving sealing problems than offering the lowest price, but we will quote if it appears that the customer needs more than just a price. A few years ago a company asked us to quote on four sizes of Viton® o-rings and mentioned in the inquiry that they were using a nitrile o-ring as a drive belt and it was failing on a weekly basis. Someone had recommended Viton® as a possible solution to the o-ring belt problem.

We sent the quote but also mentioned that we didn't really think Viton® was the best approach. Viton's® claim to fame is excellent temperature and fluid resistance and that probably was not what was causing the o-ring belt failure. When many synthetic rubbers stretch they age and crack much more rapidly. We knew that another o-ring, such as a urethane o-ring, had properties that might solve the problem.

The company responded that our price was not the lowest, but that we were the only company which had questioned using Viton®. They wanted to talk further. So we asked about the application.

They made a small office type machine which they leased out. The lease on the machine included maintenance. There were hundred of machines in operation throughout their country. The cost of the o-ring belt, no matter what material, was a small fraction of what the failures were costing them. Once we had determined that there was no actual temperature problem involved, we recommended a urethane o-ring. Urethane is a plastic, not an elastomer, and doesn't have the same stretch/aging problem. We expected the urethane to last much longer under the conditions the o-ring belt was subjected to.

Our progress in getting the urethane o-ring belt to work was not smooth. Initially we sent them an urethane o-ring that was the same size as the nitrile o-ring they were using. We forgot that nitrile has a lot more stretch than urethane and so they were using a smaller diameter o-ring to compensate. Sorry about that. The company then shipped us a machine so we could figure out the right size. It took some trial and error, but we did.

An urethane o-ring has a service life in excess of one year, but the company replaces them annually just to be safe. This means that they now use one urethane o-ring where they used to use fifty-two. And oddly enough that is the smallest part of the savings. They still send maintenance people out but at much longer intervals so labor costs have dropped a lot. For what it's worth, a urethane o-ring (metric cross section and non-standard ID) costs more than the Viton® o-ring we quoted but the price of the o-ring is no longer an important consideration.

Conclusion: The cost to use a product is often much more than the cost to buy it.

Note: [Some characteristics of an urethane o-ring: The temperature range of an urethane o-ring is -40 C to +105 C. Urethane is an excellent elastomer with high abrasion resistance characteristics and high tensile strength. Urethane o-rings are often used in high pressure hydraulic systems where highly stressed parts are subject to wear.]

Next Topic: The Case of the Mixed Up Millimeters

PSP Inc. at www.pspglobal.com
© 1997-2009, Problem Solving Products, Inc.
Submit Your Industrial Website
Site Map 1 | Site Map 2 | Site Map 3
Privacy Statement | Terms of Use