Help with 20 HP motor starter in NEMA4 Enclosure

[milmat1]

I need to quote a NEMA 4 enclosure, Motor Controls for a 20HP conveyor feeder.

My problem is this needs a safety cable switch as well. So what am I going to have to do here?
The safety cable switch a Bulkpro SS-2 safety rated pull switch. Can I use that alone to open the control voltage for the starter? Or must it go through a sfety relay?

 

[milmat1]

It is outside as well, So anyone know of a NEMA 4 Enclosure that would have disconnect handle

 

[Fitz]

I need to quote a NEMA 4 enclosure, Motor Controls for a 20HP conveyor feeder.

My problem is this needs a safety cable switch as well. So what am I going to have to do here?
The safety cable switch a Bulkpro SS-2 safety rated pull switch. Can I use that alone to open the control voltage for the starter? Or must it go through a safety relay?

Disclaimer: I don't claim to be up on the latest safety standards, but I believe the proper way is to use a safety monitoring relay that your cable switch would be an input to, and the safety relay's output would be an interlock for the motor starter coil circuit. Look at something like an Allen-Bradley bulletin 440R for an example.

Hoffman and most other enclosure manufacturers offer NEMA 4 enclosures with flanged disconnect mount.

This link should help. http://www.hoffmanonline.com/produc...&cat_2=2296&SelectCatID=2296&CatID=2296#B2297

 

[milmat1]

Disclaimer: I don't claim to be up on the latest safety standards, but I believe the proper way is to use a safety monitoring relay that your cable switch would be an input to, and the safety relay's output would be an interlock for the motor starter coil circuit. Look at something like an Allen-Bradley bulletin 440R for an example.

Hoffman and most other enclosure manufacturers offer NEMA 4 enclosures with flanged disconnect mount.

This link should help. http://www.hoffmanonline.com/produc...&cat_2=2296&SelectCatID=2296&CatID=2296#B2297

I think that will work best, Plus I could add an ESTOP mushroom head to the relay channels as well...

I found a Hoffman NEMA4 Disconnect box that I like. Now if I can ever figure out the breaker/handle/actuator setup I might be in good shape....I am so out of my normal element here that I do struggle at times.

Thanks !

 

[Fitz]

I think that will work best, Plus I could add an ESTOP mushroom head to the relay channels as well...

I found a Hoffman NEMA4 Disconnect box that I like. Now if I can ever figure out the breaker/handle/actuator setup I might be in good shape....I am so out of my normal element here that I do struggle at times.

Thanks !

No problem. Adding the E-Stop to the circuit is a good idea.

Let me know specifics of what you need for the disconnect. I'll help you pick something if you'd like.

 

[Bit_Bucket_07]

You don't need a safety relay. The "SS-2" portion of the part number probably indicates that this conveyor safety switch features two independent switches. The typical installation uses one of these switches for breaking PLC output power, while the other switch is used as an input to the PLC so as to provide for alarms and interlocks within the software. If you add an E-Stop pushbutton, then you should provide two contacts for it as well and wire it in the same manner. One contact kills control power, while the second contact provides a PLC input.

 

[TConnolly]

You don't need a safety relay.

Be careful giving advice like that where you don't know the final application of the starter. There is no such thing as overkill when it comes to safety. I can't in good conscience recommend a lower safety level without knowing anything about what is being controlled or the potential risks or what local regulations the AHJ might want him to follow. You might be correct, he might not need a safety relay, but we can't declare that to be the case based on the information we have at this point in the thread.

 

[milmat1]

You don't need a safety relay. The "SS-2" portion of the part number probably indicates that this conveyor safety switch features two independent switches. The typical installation uses one of these switches for breaking PLC output power, while the other switch is used as an input to the PLC so as to provide for alarms and interlocks within the software. If you add an E-Stop pushbutton, then you should provide two contacts for it as well and wire it in the same manner. One contact kills control power, while the second contact provides a PLC input.

Be careful giving advice like that where you don't know the final application of the starter. There is no such thing as overkill when it comes to safety. I can't in good conscience recommend a lower safety level without knowing anything about what is being controlled or the potential risks or what local regulations the AHJ might want him to follow. You might be correct, he might not need a safety relay, but we can't declare that to be the case based on the information we have at this point in the thread.

The box will contain only a starter/OL for ACL motor starting. Start/Stop pushbuttons..
The cable switch is safety rated, but they want an estop button. correct me if I'm wrong here: Once we install an estop button it needs dual contacts to a safe relay channel.
As I understand it simply breaking the control voltage with a ESTOP button would not be allowed is that wrong ?

 

[milmat1]

By the way this is a conveyor for some type of mining operation...

 

[Bit_Bucket_07]

By the way this is a conveyor for some type of mining operation...

I'm quite confident that you will exceed any and all MSHA specifications if you wire your motor starter in the manner that I suggested in my previous post.

If the operator cannot see the entire conveyor from the point at which he initiates start-up, then you'll need to sound a warning horn prior to starting the conveyor.

 

[Fitz]

The proper equipment and methods depends on the applicable codes and standards that apply at the point of use, and the OP will have to determine that. There is no "one size fits all answer", which is why I inserted my disclaimer.

Regardless, I would still say use a safety relay, and use the cable switch for pilot duty only.

 

[Bit_Bucket_07]

Guess he needs to use a "one size fits all" safety relay -- just to be safe?

 

[dmargineau]

The box will contain only a starter/OL for ACL motor starting. Start/Stop pushbuttons..
The cable switch is safety rated, but they want an estop button. correct me if I'm wrong here: Once we install an estop button it needs dual contacts to a safe relay channel.
As I understand it simply breaking the control voltage with a ESTOP button would not be allowed is that wrong ?

The E-Stop PB will need two sets of contacts, both wired up to two Safety Channels of a Safety Relay; the system's control voltage will be series fed through two Safety Rated Control Relays which's coils will be controlled by the previously mentioned Safety Relay via auxiliary contacts.
The opening of one (or both) of the E-Stop PB monitored contacts will cause the Safety Relay to drop which will consequently open the two Safety Rated Relays providing control power to the system.

 

[Geospark]

Matt,

I don't know if you have read my last post in your recent thread about safety design for your SEW drives project?

http://www.plctalk.net/qanda/showthread.php?t=79059&page=2

It all boils down to the Risk Assessment.

There is no point in you or others trying to design a safety system without knowing the hazards you are safe guarding against.

As TConnolly said, there is not enough information here yet for anyone to decide what is or is not needed.

Having said that, the fact that someone has selected a safety rope switch and emergency stop for this conveyor would suggest there are certain hazards involved. Both of these are emergency stop protection measures. You do not wire these up any old way. In most cases a dual channel safety relay would be used here, but perhaps single channel would do? leaving a second contact free for a PLC or whatever.
What needs to be driven to a safe, or dead stop when an emergency stop is activated? Just the conveyor? Maybe pneumatics or hydraulics as well?
What controls need to be isolated, if any?
You don't just do it as good practice, it has to be required to prevent known hazards. Maybe doing so might create another hazard?

But yet again we are working without a Risk Assessment, so we cannot make these decisions for you.

There most certainly is no "one size fits all" with safety. Every situation is unique and must be assessed individually.

Proceed with caution Matt.

G.

 

[jstolaruk]

No risk assessment available? (spot on Geospark!) Then I always default to at least SIL category 3, usually SIL category 4, devices & strategy and that means dual channel contacts with a safety relay, monitored reset (so forth & so on).