Relay problem - corrossion? sticky?

Hi,

I'm trying to get some ideas as to why some of our relays are not working properly.

The socket is 700-HN222 from Allen Bradley and the relay is 700-HK (24VDC) series also Allen Bradley.

We sell our cabinet to a manufacturer of machines and their maintenance personell is telling me that the "relay don't work".

They have to take the relay out and put it back in again, and then it will work again.

From what they tell me it seems like it is one of the two poles that doesn't switch when getting power to the relay. Atleast in that case

The relay itself have no signs of corrossion on the pins.

The relay are located in Egypt in "unpowered" machines. They just power them up for tests and on a quite regular basis they have to take the relays out and put it back in again.

I was thinking that the cabinets was getting wet inside because of the temperature diffrence between night and day but they say that all the papers inside the cabinet is fine. If it would be water inside the cabinet the papers would be somewhat damaged.

So I'm down to that I wan't to have a socket that I can open and se if there is any problem. But since there is no sign of corrosion on the relay I don't think this is the problem. But then again it's unlikely that the one pole would "stick" since they just pull it out and back in again.

As I understand gold plated contacts is better for corrosion? But will the pins also be gold plated? IF the problem is in the socket connection then it would be no good. Also, there are 1700pcs at site so want to avoid changing them.

We have never had this problem but once, that also in Kuwait with a cabinet with no power to it. When they powered it up they had to pull all relays and put them in again.

Thankfull for any ideas

Think you need to post a snippet of wiring so we can see how you have implemented this relay.

The relay base looks very very much like one made by Finder:
https://uk.rs-online.com/web/p/relay-sockets/5348868
I have used a lot, and not wishing to tempt fate, I haven't had any issues. They have a nice clip that keeps the relay in place.

I don't use that make of relay, but instead one that used to be Releco, but which now seems to be part of Finder:
https://uk.rs-online.com/web/p/non-latching-relays/5345336
I choose that one because it has mechanical and LED indication when powered, plus a lever on the top so that it can be manually operated. Again, fate please forgive me, no issues.

Which way are you mounting the relays?

I just measured the thickness of the relay connectors, they are almost exactly 0.5mm thick, how about on the relays you use?

Attached is wiring. It's 24VDC voltage with no load to talk about.

That relay and socket looks exactly the same as the Allen Bradley I use. Must be labeled relays, also 0,5mm thick.
They are mounted on DIN rail on the "correct" way.

Loaded down 24VDC can cause similar issues. Take a small external power supply and run individual relays.....have you checked for 24VDC with your meter?

dcam said:

Loaded down 24VDC can cause similar issues. Take a small external power supply and run individual relays.....have you checked for 24VDC with your meter?

Click to expand...

The 24VDC power supply isn't much loaded at all, and the control input the relay contacts is wired to doesn't draw much.
I can't meassure at site since it's in Egypt and the maintenance personel is back home.

Relays need a minimum switching load to keep the contacts from developing a film. Specs for this relay show 50 - 500 mw for minimum load, depending on contact alloy. Kind of rare, but I have had problems with too small of a load.

jaden said:

Relays need a minimum switching load to keep the contacts from developing a film. Specs for this relay show 50 - 500 mw for minimum load, depending on contact alloy. Kind of rare, but I have had problems with too small of a load.

Click to expand...

In the early 90s at a rubber plant, we saw this with relays supplying digital inputs to some servo amps and had to spec a relay with gold contacts to solve it, and then train our purchasing agents and maintenance techs that we really needed those $25 relays to avoid costing hundreds of dollars in down time and lost production. I am not sure if it was the low current inputs on the servos or the sulfur in the atmosphere that would cause the normal silver plated contacts to fail, but the gold plated contacts never did. IIRC, they only had a 1A contact rating so the floor techs would assume that 10A is better if there was some problem that appeared related to those relays and plug in the cheap ones only to create more issues.

jaden said:

Relays need a minimum switching load to keep the contacts from developing a film. Specs for this relay show 50 - 500 mw for minimum load, depending on contact alloy. Kind of rare, but I have had problems with too small of a load.

Click to expand...

Thanks I'll look into that!

For switching low loads [microAmps] use a relay with bifurcated contacts. OMRON, IDEC and others offer this feature.

Hi rQx, it seems a bit unclear what you are saying when you say the relays aren't switching. Are the relays turning on and they don't get a voltage thru the contacts, or are the relays not turning on, they remove the relay from the base, reinstall relay and then they turn on and voltage is travelling thru the contacts. If the first scenario, that is why you buy gold flecked contacts relays, if the load is only for PLC type indication, there isn't enough load across the contacts to keep them clean and they get a film on them that, although the relay has turned on AND the contacts have closed, you don't get a circuit thru the contacts.

I have experienced when there is high humidity and salt content in the air, i.e. close to the ocean in the middle east, that you get all kind of weird corrosion problems.
Is the Egypt site close to the ocean ? Maybe the same as in Kuwait ?
If that is the explanation then I dont have an easy solution

In my case it was Alexandria, Egypt.

If you have 1700pcs at the site then get the manufacturer involved especially if they are all exhibiting this problem. Also, I would foresee a field service trip if 1700 relays were playing up.