Teknic EF-785, Installation Manual

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you need to do to provide the required level of protection. Typical safety
control systems for level 2, 3 or 4 are constructed using safety control
“relays”
5
, positively-driven E-Stop switches, interlock switches, guard-
lock switches
6
, and contactors with positively-driven feedback contacts,
all wired together by the machine builder to interrupt power to the
mechanical hazards. (The requirements for all of these devices are each
called out by various other EN standards.) There is then a procedure
described in ISO 13849-2 which details how to do an FMEA (Failure
Mode Effects Analysis) to prove that your system is fault tolerant. Then
the system must be tested to make sure that the monitoring of the safety
system will report errors when they occur to fully meet the requirements.
The requirements become more difficult and expensive to comply with if
you want to allow for a controlled stop before removing hazardous power
and/or if you want to construct a two area (Main + Load/Unload)
machine.
All of the above sounds like a lot of work, hassle and expense- and it
is . To make things even more frustrating, meeting these important
requirements rarely, if ever makes your machine more attractive to your
customers at the time of sale. It slows time-to-market and increases
development cost without providing any
differentiating market value.
Basically, all machinery vendors are forced to mark their machines as
compliant, so customers don’t perceive any difference.
Sometimes engineers take shortcuts when designing their safety
control system by not reading, or partially ignoring, any or all of the EN
standards referenced by the CE Machinery Directive, hoping that the test
lab does not catch any errors or omissions. Unfortunately, this can often
result in significant rework and delay of product launch when the test lab
discovers insufficient compliance. If you’re “lucky” enough to pass a
machinery safety compliance inspection despite having errors and/or
omissions then, of course, there is a real liability issue. Clearly, taking
“shortcuts” is not advisable.
Light at the end of a short tunnel…
Fortunately, the eF-785 is pre-engineered to remove nearly all of this
work from your project plan. All you have to do is to assess whether you
need a level 2 or 3 safety control system based upon your risk
assessment. If you need a level 3 system, install the eF-785 with guard-
locks on any movable guards (i.e. protective doors or covers). If you
require a level 2 system, install the eF-785 with interlock switches on any
Main area moveable guards, and guard locking switches on any moveable
guards in the Load area. That’s it.
The safety review and certification of the eF-785 to EN 954-1 explicitly
included an FMEA of a safety control system constructed as detailed in
this manual to make sure the installation instructions, when followed,
would result in a safety control system compliant with the standards. So,
if you install the eF-785 according to these instructions, using the
recommended 3
rd
party components, your machine will be compliant.
5 Safety control “relays” are control circuits constructed of multiple relays with special
positively guided contacts, electrically cross-coupled and packaged together to perform
fail-safe control and monitoring functions. These “relays” typically cost $200-
$1,000USD depending on the safety level required and the required complexity of the
control system (systems that allow time for a controlled stop and/or control multiple
areas cost increasingly more).
6 Guard-lock switches are interlock switches that also have a fail safe solenoid latch to
lock the guard (door) they are monitoring in a closed position.
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