Hoist Runway Mainline Disconnect

[WoodyPE]

ref: OSHA Reg 1910.179 Section G5-iii

We need to install some runway disconnect switches and the regulation doesn't read very clearly.

What is/are the purpose(s) of a "runway mainline disconnect switch"?

Apparantly, it is not a lock-out tag-out feature for maintenance because we have that capability at the circuit breaker.

Also we have emergency stop buttons on the pendants.

Help would be appreciated. Thanks much.

 

[safetydan]

From OSHA CFR:

1910.179(g)(5)(iii)

On floor-operated cranes, a switch or circuit breaker of the enclosed type, with provision for locking in the open position, shall be provided in the leads from the runway conductors. This disconnect shall be mounted on the bridge or footwalk near the runway collectors. One of the following types of floor-operated disconnects shall be provided:

1910.179(g)(5)(iii)(a)

Nonconductive rope attached to the main disconnect switch.

1910.179(g)(5)(iii)(b)

An undervoltage trip for the main circuit breaker operated by an emergency stop button in the pendant pushbutton in the pendant pushbutton station.

1910.179(g)(5)(iii)(c)

A main line contactor operated by a switch or pushbutton in the pendant pushbutton station.

1910.179(g)(5)(iv)

The hoisting motion of all electric traveling cranes shall be provided with an overtravel limit switch in the hoisting direction.

1910.179(g)(5)(v)

All cranes using a lifting magnet shall have a magnet circuit switch of the enclosed type with provision for locking in the open position. Means for discharging the inductive load of the magnet shall be provided.

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My question to you is what does the manufacturer tell you?

The way the regulations read, it is so someone can disconnect the power to the crane from a location on the ground.

 

[WoodyPE]

I have the regulation, but the purpose of the runway main line disconnect switch is not clear. The hoist manufacturers do not take responsibility for this part of the code. According to them, this is a plant requirement, not a product requirement.

I read section iiib to mean the emergency stop button on the pendant meets the requirement. Why would anyone spend money on the other types of switches if the pendant e-stop is good enough, and it is required anyway by the code?

This part of the code does not make rational sense to me, and seems to be a redundant waste of money.

 

[safetydan]

Welcome to OSHA.

 

[kenvlach]

Operators sometimes lose hold of pendant controls when maneuvering around large equipment and tanks of hot liquids. Helps to have liquid-tight pendants.

 

[Simmers]

Consult NEC Section 610.31 thru 610.33: It's very clear there and is recognized by OSHA.

The runway disconnect must be readily accessible from the floor, capable of being locked open (all ungrounded conductors) and placed within the view of the runway conductors (AND LABELED PROPERLY)

Disconnects for individual cranes and hoists/monmorails are also discussed in detail.

 

[standg]

You cannot consider your e-stop button as being efficient enough. According to OSHA, e-stops are not to be used as means of isolating energy.

 

[ssn596]

As a working electrician and also as one with 20 years in safety.

An E stop generally will turn off all control power to a machine. In the case of a crane this would be to the bridge, trolley and hoist motors. In some cases an E stop can also disconnect main power either by a relay or a shunt trip on the breaker.

Because the E stop is GENERALLY only in the control circuit AND using control power only (in old days pushing in stop button) is EXTREMELY unsafe because oldest electrician trick is to use screw driver to push in the relay and energize the motor and you end up ground up This has happened more times than you can shake a stick at you MUST have a disconnect that kills all power (required by OSHA and NEC)

OK so for cranes the disconnect must be on the floor in the area the crane serves (it is also a real good idea to have one on the bridge DOUBLY so in the case of floor operated cranes. I would think the circuit breaker in the panel could suffice for the floor disconnect IF nearby AND clearly marked AND legible from the ladder leading to the crane way.

Food for thought
what are your priorities
keeping your employees safe
or
merely complying with OSHA??

Dan Bentler

 

[cranergy]

In the long run, being extra cautious with this type of equipment is always recommended and saves costs associated with damage and injury. More safety measures are explained in this article: crane safety.
Periodic inspections are also part of OSHA regulations and are sometimes part of insurance requirements.