How many cycles.

I am using a 1734-OW2/c relay output card. I was wondering how many cycles can the relay reliably deliver without failure.

If it switches more current than it was designed for, zero.
The question can't be answered without knowing the load. Spec sheet ratings are generally given for purely resistive loads. Inductive loads will reduce the life. Suppression will mitigate the impact of inductive loads.
If you are switching an output so frequently that relay life becomes a concern, you're probably better off with a solid-state output device. If, for whatever reason you really need the contact output, consider a solid state output driving an interposing relay so that when the relay fails it is easy to replace.
If you need one more output and all you have available is a contact output, you can still add an interposing relay. That will give you a relatively small load on the PLC output and the interposing relay will be the more likely point of failure.

No it has worked for at least 5 years and the relay switches 70 times a minute 24/7. I suspect that I am getting some chattering in the contacts that could be causing my issue.

LOL... if my math is right thats 183,960,000 cycles

Its past do and should be changed out, do they offer a transistor (solid state) one? if yes it would be better that the mechanical relay

Do you have an unused output on the card?

I would reprogram the output to another one. At least that would eliminate the relay if the problem continues.

Thank you for the Answer Steve. I will have to do some more research on the load.

70 times a minute 24/7

Click to expand...

70 cycles x 60 minutes/hr x 24 hr/day x 365 days/year x 5 years = about 184 million cycles.

The relays used in POINT I/O modules are generally rated to mechanically run about 20 million cycles. At full load, the contacts in those relays are expected to serve for only about 100,000 cycles.

A module that's served for that long at that rate should be considered for replacement.

Certainly if you consider "chatter" a possible reason for a malfunction you may wish to investigate a solid-state interface both for performance and longevity.

At almost 185 million cycles, the relay mechanism could be wearing out even if the contact itself is still clean. Aabeck's suggestion is a good way to test whether the problem is in the relay itself.

Minimum 100,000 operations @ rated load.

Probably not more than 20,000,000.

Publication 1734-IN055I-EN Page 23

Let me see now . . .
5 years times 365 day/yr X 24 hr/day X 60 min/Hr X 70 cycles/min = (roughly) 184 Million cycles . . .

I do hope you have a spare one on hand?
Poet.

Are you sure it's 70 cycles per minute and not 70 cycles per hour? Or has the application changed since the original installation? At the risk of insulting the OP, it's hard to imagine a competent designer intentionally using a relay contact output for that application.

At 185 million...I am pretty you have exceeded MTBF of relay components.
MTBF is "Mean Time Between Failure". Most components have this rating.