Estop

Message: 3
   Date: Tue, 27 May 2003 22:49:17 -0500
   From: "Dan-Att" <dsymonds@xxxxxxx
Subject: RE: Re:disable input and emergency stops

Gentlemen:

FYI

In response to the discussion last night about ESTOP, I retrieved my copy of
the NFPA 79 Electrical Standard For Industrial Machinery and in section 7-5
under the heading of "Stop Circuits" it reads as follows:

(a) Stop functions shall be initiated through deenergization rather than
energization of control devices.

(b) Stop functions shall override there related start functions

(c) Each machine shall incorporate at least one emergency stop device which,
when activated, shall deenergize all electrical power circuits which provide
electrical enegry to sustain machine motion without creating other hazards.
The functioning of any breaking system fitted to the machine to stop it more
rapidly shall not be prevented by activating the emergency stop.

Exception: Where an emergency stop device would exactly duplicate the
function of the stop device(s), a separate emergency stop device shall not
be required.

(d) All machine motions stopped by emergency stop function or other stop
function shall be restarted only by deliberate operator action.  The
resetting of the emergency stop function or stop function shall not restart
any part of the machine.

Cheers
Dan Symonds




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