Electrical Workbench Grounding Straps

STORY BY EMC(SW) MICHAEL LAVERGNE, NAVAL SAFETY CENTER, AFLOAT SAFETY PROGRAMS DIRECTORATE

How many times have you been in an electrical/electronic shop and noticed that there were single, green wires with something attached (that looked like an alligator clip) coming from the work bench?

It isn’t just an ordinary wire. It is a lifesaving device known as a “grounding strap,” and it connects that piece of equipment to the hull. Electric current likes to flow in the path of least resistance. When there’s a problem, the current will flow to ship’s hull instead of shocking (or killing) the worker.

Grounding straps are covered by PMS MIP series 6652/006(or L06) A-1+ and NSTM 300. You must have one grounding strap for every four feet of work bench. Grounding leads and grounding straps must have green insulation or be marked with green-colored tape or green-colored adhesive labels. Grounding straps must be at least 40 inches long and able to reach every part of the work bench.

A 50-amp, blunt-nose, battery-type clip and insulating sleeve must be installed at the free end. The Servit post must be sealed with two coats of varnish (A-A-1800) or other suitable preservation to protect from moisture or corrosion. The ground stud should be welded to the hull (if feasible) or to a main member on the bulk head. The grounding stud should be connected to ground using three nuts or a collar stud with two hex nuts.

A ground bus serving a row of workbenches must be continuous (unsliced) cable no longer than 50 inches.

Resistance from the ground (battery type) clip to a point beside the deck grounding stud must be less than or equal to 0.1 ohm. If greater than 0.1 ohms resistance, tag out the disconnect switch and test panel, notify work center supervisor, repair or replace as necessary, remove safety tags and return equipment to readiness condition.

NSTM 300, Electric Plant-General, states ships shall have a minimum of one electrical workbench maintained all times.

More information on standardizing electrical workbenches/requirements can be found in:

  • Naval Ship’s Technical Manual (NSTM 300 Appendix H)
  • PMS MIP 6652/006(or L06) A-1+

This article was originally printed in Sea Compass Vol. 5, No. 1 with a content error. We would like to apologize to our readers for the inaccuracy and have reprinted this article with the corrected information.

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