Hi Folks
The concept of hipotting equipment in the field after repairs may
theoretically be a good one - but is fraught with both practical and safety
problems.
For example:
a) Some equipment needs special hipot equipment or equipment settings, e.g.
if it has large filter capacitors on the AC/DC input. However, most
servicemen will have - at most - a physically small portable appliance
tester ("PAT") with very limited test voltage and current capabilities.
These will often show a test failure (due to the current drawn by the
filters tripping the fault indication circuit)when no actual fault exists.
b) To give the serviceman a tester capable of performing the tests per the
factory hipot means that he probably has a large, heavy machine (which he
won't want to carry around) that has a potentially lethal output which
should only be used in controlled factory conditions.
c) It could be dangerous to hipot an equipment in-situ - both to the
serviceman and to any other equipment that is attached, and to any people
who are touching associated equipment.
d) If incorrectly used, both the equipment under test and associated
equipment could be damaged - which will be expensive and timeconsuming to
fix.
e) The serviceman will need special training, and what happens if he passes
the equipment to someone who has not had the full training?
f) How do you guarrantee that a serviceman will take the proper care of the
tester, and what happens if someone else starts "playing around with it" for
"fun"?
-- and so on.
I think a far better approach would be:
i) Design the equipment so that it is easy to repair, with all safety
critical ( or "-related" - see earlier discussions!) components being easy
to replace, or built into service-replaceable modules. Avoid complicated
wiring layouts which could be damaged, or incorrectly refitted during
service. Fit appropriate warning and caution labels both inside and outside
the equipment.
ii) Ensure the service instructions give clear indication of how to
fault-find the equipment, exactly how to repair it, and with exactly which
components or modules.
iii) Ensure the service instructions give an appropriate set of visual
and/or simple DMM checks for the physical and electrical safety of the
equipment before and after completing the service work and refitting the
covers
In other words: "KISS".
John Allen
Thales Defence
Bracknell UK.
-----Original Message-----
From: Anderson Cheng (TPE) [mailto:anderson_ch...@htc.com.tw]
Sent: 06 February 2002 02:59
To: 'marti...@appliedbiosystems.com'; emc-p...@majordomo.ieee.org
Subject: RE: Compliance After Repairs in the Field
If products required to have 100% production-line tests (such as Hi-pot and
Ground Continuity tests), then I required that tests should be made in the
field after repairs. I think it at least benefits checking out the minimum
safety constructions are still functioning well.
Regards,
Anderson Cheng
High Tech Computer Corp.
-----Original Message-----
From: marti...@appliedbiosystems.com [mailto:marti...@appliedbiosystems.com]
Sent: Wednesday, February 06, 2002 7:50 AM
To: emc-p...@majordomo.ieee.org
Subject: Compliance After Repairs in the Field
Greetings,
We are a manufacturer of Laboratory Equipment. We evaluate our products to
UL 3101-1, CSA 1010.0 and EN 61010. When we repair a product in the field,
which may include replacing power supplies, line filters, etc., what
obligations do we have to verify continuing compliance with the safety
specifications we originally evaluated our products against? Do we need to
perform applicable safety testing following these repairs?
Traditionally, NRTL's are not concerned with the product once it leaves the
factory. They do not require follow-up testing to be performed after
repairs are made in the field. Since we self-certify to the LVD, should we
take a different approach to repairs in the field compared to the approach
NRTL's take?
Does your company have a specific process that is followed when repairs are
made in the field to verify continuing compliance? If so, what is that
process?
All responses are appreciated.
Regards
Joe Martin
EMC/Product Safety Engineer
Applied Biosystems
marti...@appliedbiosystems.com
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