High quality control relays for critical application 1

[SA07]

Hi
For a particular application we have the following relays. We will replace them with new ones. Can you please suggest some make/reference of higher quality relay for a critical application? Thanks.

 

[itsmoked]

What causes you to seek "higher quality"?

What are these relays doing?

What voltage are they switching?

How often do they operate?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[che12345]

Dear Mr. SA07 (Electrical)(OP)22 Feb 22 11:48
"... For a particular application we have the following relays. We will replace them with new ones. Can you please suggest some make/reference of higher quality relay for a critical application?..."
1. What is the problem that you are facing, e.g. contact over-heating/melted, coil over-heating, coil open circuit, required higher IEC IP rating ... etc?
2. This relay is rated for Resistive load 6A at 250V AC, 6A at 28VDC.
3. Attention: if the load is inductive e.g. IEC AC3 or 4 etc., the current rating is lowered.
Che Kuan Yau (Singapore)

 

[SA07]

Actual relays are used to stop boiler feeders. We have got several boiler trips due to this circuit during disturbance of utility network. The relays are in service for about 15 years. We intend to replace them as preventive maintenance.

Some contacts are used for signaling to PLC. Some are used to close gate valves.
They switch 24 Vdc.

They operate about 10 times per year.

 

[IRstuff]

Sounds like you need a UPS, not new relays

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[RRaghunath]

The relays operate on 24V DC and I suppose your 24V DC system is backed up by storage battery. If yes, how can disturbance in utility network affect your DC system voltage. If it is happening, it means your battery needs to be replaced (your 24V DC system is depending solely on the Float charger).

 

[itsmoked]

Besides the excellent advice already given it doesn't sound like you need "better relays" but relays that have a lower hold-in voltage. You should look up the specs of the relay you have with regards to hold-in voltage and after seeing what it is find a similar-plug-in replacement with a lower hold-in voltage.

Just checked your relay.
Never mind. It's as low as they get. 1/10th the pull-in voltage.

A UPS that works is the order of the day.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[SA07]

We already have industrialised type UPS supplying the whole of the plant. We replace the batteries every 2 years.
We have several boiler trips in the past due to this circuit. This part is causing the first trip of the boiler.

 

[3DDave]

What disturbed the utility network and what was the effect of the disturbance on the UPS that allowed the 24V supply to drop so far that the relay tripped?

 

[SA07]

e.g. Earth fault on the utility network

 

[IRstuff]

So, how is this a problem with the relays? Sounds like a solution looking for a problem. It would seem to me that the appropriate approach would be to further insulation your system from the utility; a relay can only work if it's properly powered, PERIOD.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

https://www.youtube.com/watch?v=BKorP55Aqvg

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[3DDave]

what was the effect of the disturbance on the UPS that allowed the 24V supply to drop so far that the relay tripped?

 

[davidbeach]

I'll add my voice as well. There is no way that an AC utility system fault, of any sort, can impact a properly designed and installed battery based DC system. Find the flaw in the DC system before looking for a different relay.

One possible DC design flaw that I don't recall seeing mentioned is that the DC is also being used to trip breakers that clear the AC system fault and that there's isn't sufficient DC capacity to do that without adverse impact to other portions of the DC system. If that's the case, it's a design flaw that won't be overcome with different control relays.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[SA07]

I agree with you.
We have noticed that for about 50 relays on site only 1 the led on is working.

2 relays on the MFT (Master fuel trip) circuit the mechanical indicator orange is in off position although the relay is energized.

 

[RedSnake]

Changing the relays that are not fully functioning should be step 1.

You mentioned that some are used to close gate valves and that they switch 24 Vdc.
But what is the power consumption of this valvs?
It looks like the tung 11-12-14 is a bit burnt on the picture, this doesn't mean that it isn't working but if there is arcing due to spikes from the valve coils there needs to be surge arresters on the valve coils.
This can make the relay not tripping when you tell it to.

That the orange indicator don't seem to work on two of the relays are not good they are mechanically attached to the tungs.

Best Regards A

“Logic will get you from A to Z; imagination will get you everywhere.“
Albert Einstein