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Anonymous Poster #1

Shear Pin Relay

04/20/2017 3:18 AM

Hi All,

As a university student, we are required to undergo industrial training which i am currently undergoing at a Pumping station.

I came across the term "immediate/shear pin relay" on a soft starter.

Can anyone explain its meaning and functioning.

Thanks

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#1

Re: Shear Pin Relay

04/20/2017 3:23 AM

Yes, indeed.

  1. The individual(s) who carried out the design can explain the term. The description will be in a document named "Control Description", "Functional description", or "Process description", or similar. The name(s) will be on the document.
  2. The individual(s) who carried out the commissioning of the equipment can also explain the term. Their testing records will be in the commissioning documentation for the equipment. The name(s) will be on the document.
  3. Operatives at the pumping station or driving it remotely can also explain the term, because these individuals need to know what to do when the equipment operates. So ask them. It will also be written-up in the operating manuals for the equipment.

Alas, none of those documents can be seen from here. However, the documents are a good thing, because it means that, even in the absence of the individual(s) who wrote and use(s) them, the fresh eye on them can soon come up to speed on the contents and the meaning. Especially someone of the presumed intelligence of an Engineering undergraduate.

Good luck

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Anonymous Poster #1
#2
In reply to #1

Re: Shear Pin Relay

04/20/2017 3:33 AM

Hi,

Thank you for your response.

The station was designed around 20 years back. Such documents are currently not available.

Just for information- The soft starter make is solcon and type RVS DN. I tried to look in the manual of the soft starter but i cannot understand what the term shear pin refer to.

Thanks

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#9
In reply to #2

Re: Shear Pin Relay

04/20/2017 10:58 PM

I, too, knew what shear pins (mechanical) are, but the addition of the term "relay" was a stumper. Wonderful knowledge, this. Thanks to all, again.

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#3

Re: Shear Pin Relay

04/20/2017 3:58 AM

http://slideplayer.com/slide/6293149/

"70 Main Parameters O/C – SHEAR PIN - Operational when RVS-DN is energized and has three trip functions: At all time - If I > 850% of FLC it trips the RVS-DN within 1 cycle (overrides the value of the O/C – SHEAR PIN setting). At starting process - If I > 850% of FLA it trips the RVS-DN after O/C DELAY (see here after) At run time - If I > O/C – SHEAR PIN setting of FLA it trips the RVS-DN after O/C DELAY Note: The O/C SHEAR PIN is not intended to replace the fast acting fuses, required to protect the thyristors. Adjustments: –Trip Current: 100-850% of FLA –Trip Delay 0-5 sec. O/C SHEAR PIN 850% OF FLA O/C DELAY 0.5 SEC. Trip 850% I FLA "

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Anonymous Poster #1
#4
In reply to #3

Re: Shear Pin Relay

04/20/2017 4:51 AM

Thank you sir.

Your reply has been of great help for me.

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#5

Re: Shear Pin Relay

04/20/2017 8:34 AM

The concept is an electronic representation of an old mechanical device used to prevent major damage to critical machinery. The engineer would design in a component somewhere along the mechanical drive train that was purposely made weaker than all the others, but also very easy to access and replace. This component would often take the form of a "pin" in a gear or belt sheave that would break or "shear" under extreme torque. So if something in the machine jammed, this sacrificial device would break first, protecting the rest of the machine from damage. The machine still stopped, but the damaged part was easy to replace and get back the machine back into production.

It's now possible to replicate this function electronically by monitoring current, because in a motor, current and torque follow each other directly. So if a machine jams, the motor current jumps quickly and the "shear pin" function disables current flow to the stator before anything breaks.

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#7
In reply to #5

Re: Shear Pin Relay

04/20/2017 3:33 PM

Learned something new today. Thanks! I'd never come across that term before.

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#11
In reply to #5

Re: Shear Pin Relay

04/21/2017 1:06 AM

EXCELLENT ANSWER! Thanks! I've known of mechanical shear pins most of my life, but I had not heard the term used in an electrical context.

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#12
In reply to #5

Re: Shear Pin Relay

04/21/2017 2:18 PM

Ditto what half of CR4 has said about your post.

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#6

Re: Shear Pin Relay

04/20/2017 11:35 AM

Interesting topic. I learned something new (or got reminded). That is not my normal job function, but if someone mentions it during an explanation, I will immediately understand now.

Thank you Anonymous student.

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#8

Re: Shear Pin Relay

04/20/2017 10:57 PM

I came to this discussion to read and learn because it seemed like an interesting question. I leave educated, enlightened, and, once again, delighted with the folks with whom I get to hang out on CR4. Thank you, Anonymous 1. Might you be willing to hang around, get an ID by which we can know you in future, and share the future with us? Most Anons seem to be more interested in scamming, flaming, or asking for help with home work. You, sir, or ma'am, have educated more than one today.

Hats off to you!

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#10

Re: Shear Pin Relay

04/20/2017 11:23 PM

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#13

Re: Shear Pin Relay

04/21/2017 4:23 PM

Jraef et al thanx. Very clear and concise.

It is sad that documentation can't be available (lost or misfiled) only 20 years after install.

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