Download EN 50191 Workstation Seminar

Setting up a Safe
Product Safety Workstation.
Electrical Safety
Seminars
Dwayne Davis - Associated Research Inc.
1
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Seminar Outline
Setting up a Safe Product Safety
Workstation.
I.
II.
III.
IV.
V.
VI.
VII.
VIII.
IX.
X.
XI.
XII.
XIII.
How is your product safety testing workstation set-up?
Considerations for a product safety testing workstation.
EN 50191, erection and operation of electrical test equipment.
Protection against electrical shock.
General requirements.
Test stations with automatic protection against direct contact.
Test stations without automatic protection against direct contact.
Test laboratories and experimental stations.
Temporary test stations.
Test stations without test personnel in permanent attendance.
Operation of test installations.
Personnel.
Article reprints.
Associated Research, Inc. ©2002
How is your Product Safety
Testing Workstation Set-up?
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Is my product safety testing workstation set up
for maximum productivity or safety?
Are assembly operations performed at the same
workstation to balance the production line?
Can assemblers not involved with the electrical
aspects of manufacturing the product
inadvertently be exposed to electrical safety
hazards?
Are my operators aware of the potential hazards
involved in performing the product safety test?
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Considerations for a Production
Safety Test Workstation.
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Where do you find guidelines for setting up the
workstation?
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In the US; OSHA 29 CFR part 1910 subpart S,
Electrical Safety Related Work Practices.
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NFPA 70E, Safety Requirements for Employee
Workplaces.
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In Europe EN 50191, Erection and Operation of
Electrical Test Equipment.
Associated Research, Inc. ©2002
EN 50191:2001
Erection and Operation of
Electrical Test Equipment.
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How to set up and operate a safe electrical test
workstation.
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Implemented in Europe March 1, 2001.
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Any other national standards in Europe that
contradict this standard have to be withdrawn by
October 1, 2002.
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The standard does not just cover testing equipment,
but the whole electrical test installation, including
the size of the test areas, use of protective barriers,
indicator lights and signs.
Associated Research, Inc. ©2002
Human Body Resistance.
The human body on an average has about 1000 to 1500 ohms resistance
to the flow of electrical current. The outer layer of the skin provides the
largest percentage of the body’s electrical resistance. The amount of
resistance the skin provides varies widely. Dry thick skin provides a much
higher resistance than moist soft skin or skin which may have a cut or an
abrasion. The parts of the body which conduct the electricity the best are
the blood vessels and nerves. Therefore when a person receives a severe
electrical shock many times internal injuries may result. The skin, like any
insulator has a breakdown voltage at which it ceases to act like a resistor
and is simply “punctured” leaving only the lower resistance body tissue to
impede the flow of current in the body. This voltage will vary with the
individual, but is normally in the area of 600 volts.
500
• Hand to hand 1000
• 120 volt
• Formula I = E/R
• 120/1000 = 0.120 amps or 120 mA
500
100
500
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500
Protection Against
Electric Shock.
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The severity of shock received by a person who contacts
an electrical circuit is affected by three primary factors:
1. The amount of current flowing through the
body.
2. The path of the electrical current through the
body.
3. The duration or length of time the person is
exposed.

Burns are the most common form of shock related
injury. Any person who is exposed to voltages in excess
of 50 volts is at risk of being injured from an electrical
shock.

Currents as low as 50 ma can cause an irregular heart
beat which is known as fibrillation, which can cause the
heart to stop the pumping action.
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Startle Reaction.
UL and ANSI conducted experiments in the 1960’s to determine how
the human body responded to different current levels. Tests were
run using a 120 volt 60 Hz source. They determined that on an
average 0.5 ma of current is the perception level that can produce a
startle reaction, higher levels of current in the range of 5 to 10 ma
start to produce an inability to let go, the electrical current causes a
paralysis where you cannot release a hand grip on the circuit.
Currents in the range of 20 to 40 ma between the extremities makes
the muscles contract painfully, making breathing difficult leading to
asphyxiation. Current levels in the 40 to 70 ma range lasting for 1
second or longer causes ventricular fibrillation which is frequently
fatal. Further increasing the currents greater than 70 ma causes
electrical burns and cardiac arrest.
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General Requirements.
Protection Against Electrical Shock.
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Test assemblies arranged and designed that the protection
against direct contact is secured by insulation of live parts,
covers, enclosures, obstacles, or safe distances.
Use of two hand control devices.
Prohibition zone.
Barriers to separate the test area from work areas and
passageways.
Use of indicator lights and signs.
Emergency cut off switches.
Unauthorized and unintentional switching.
Prevent automatic energizing.
Protection against residual voltages.
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Test Stations with Automatic
Protection Against Direct Contact.
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Insulation of live parts using covers or enclosures to protect
against direct contact with the test object.
Use of fail safe interlocks to prevent application of test
voltages, opening cover or enclosure must disconnect the test
voltage automatically and residual voltages must be reduced
to non-hazardous level before the DUT can be touched.
Single fault conditions shall not prevent the test voltages from
being turned off, and the occurrence of a fault shall ensure
that it is impossible to switch voltages on again.
Mechanical construction must be adequately strong.
Test stations with automatic protection against direct contact
may omit barriers and emergency switching- off devices.
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Test Stations Without Automatic
Positive Protection Against Direct
Contact.
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Test stations without positive protection against direct
contact shall only be installed if the erection of test stations
with automatic protection against direct contact is not
practicable,
-due to frequently changing test duties.
-In case of varying types of test objects.
-In case of serious difficulties in performing the
work.
-When test duties occur only occasionally.
Barriers must be used to separate the test area, they may
take form of walls, grids, ropes, chains or bars subject to
national regulations. They shall be designed that visual
contact with the operator can be maintained at all times.
At least one emergency switching device shall be installed
outside the test area.
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Test Stations Without Automatic
Positive Protection Against Direct
Contact.
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An adequate number of red signal lights,
indicating operational status shall be installed.
If test circuits are electrically connected to the
general power supply system, additional
protection shall be provided by means of an
residual current device (RCD) with a rated
difference current < 30ma.
Test workbench tops shall be made of insulating
materials.
The working area of test stations shall be such
that movement of test personnel is not impeded.
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Test Laboratories and
Experimental Stations.
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The barriers shall be solid walls or grids at least 70 inches
(1,800 mm) high. Entrances shall be provided with warning
signs “no unauthorized persons beyond this point”
- in cases of voltages up to 1,000V, the barriers
may also be ropes, chains, or bars. Solid walls or
grids must be at least 39 inches (1,000 mm) high.
A sufficient number of red and green signal lights shall be
installed to indicate the operational status.
- Green signal lights are not required for voltages
up to 1KV.
When there are separate test areas within the test
laboratory the operational status of each of the test areas
shall be indicated by means of signal lights.
Emergency escape doors, gates shall be able to be opened
from the inside of the test area.
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Test Laboratories and
Experimental Stations.
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In test laboratories measures are required to
prevent unauthorized entry and shall not hinder
persons from leaving.
In test laboratories with voltages exceeding 1 KV
devices or provisions for grounding (earthing)
shall be available.
Where test voltages exceed 1KV, all areas
including those outside the test area where
capacitive charging is likely to take place shall be
separated by additional barriers for the duration
of the testing.
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Temporary Test Stations.
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Unauthorized persons shall be prevented from access to
temporary test areas by means of walls, grids, ropes, chains,
bars or similar barriers. Entrances shall be provided with
warning signs “no unauthorized persons beyond this point”.
Escape facilities shall be provided.
Voltages exceeding 1KV, devices or provisions for grounding
(earthing) shall be available.
Voltages exceeding 1KV, in which capacitive charging is
likely to occur even outside the test area shall be separated by
additional barriers for the duration of the test.
When safety probes are used with voltages exceeding 1KV
the high side of the test apparatus shall be electrically isolated
from the supply and insulated from earth, the same applies to
test probes and their leads. The test object shall also be
isolated from earth where practicable.
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Test Stations Without Test
Personnel in Permanent
Attendance.
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Shall be erected in compliance with automatic
protection against direct contact or set up with the
requirements as specified for a test laboratory.
Emergency stop equipment in accordance with the
requirements of EN 418 Safety of Machinery with
an adequate number of manual controls shall be
provided.
Prevention of automatic energizing may be
omitted, provided that this will not cause any
hazard.
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Operation of Test Installations.
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Test stations other than those which have automatic
protection against direct contact may only be operated under
the control and supervision of a skilled person.
Test installations shall be provided with operating
instructions and shall contain the information required for
safe operation.
Test installations shall be inspected for visible damage or
defects before use and shall not be operated if there are signs
of damage or defects liable to cause danger.
Only skilled persons shall be employed to maintain the test
station.
The proper condition and efficiency of the safety devices shall
be checked by skilled persons at suitable intervals of time.
The results are to be recorded.
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Personnel.
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Only skilled or instructed persons may work with test
installations based upon the complexity of the work involved.
Training records shall be kept.
Personnel using safety probes must receive additional training
regarding special risk involved.
Personnel working in test laboratories, experimental and
temporary test stations may work only under the overall
supervision of a nominated person in control of the work.
Test areas may be entered by personnel who have received
adequate instructions regarding the hazards or accompanied
by a skilled person.
Any persons working in test laboratories, experimental stations
or in areas with temporary test stations shall be fully aware of
the existing hazards and has the duty to take safety precautions
to protect all personnel against the hazards.
Associated Research, Inc. ©2002
Resource Links
American National Standards Institute
11 West 42nd Street, 13th Floor
New York, New York 10036
USA
http://www.ansi.org
U.S. source for IEC standards and other
domestic and international standards.
Canadian Standards Association
178 Rexdale Boulevard
Rexdale, Ontario
M9W 1R3
CANADA
http://www.csa-international.org
Comité Européen de Normalisation Electrotechnique
Rue de Stassart, 35, B-1050
Brussels
M9W 1R3
Belgium
http://www.cenelec.be
ASTM
100 Barr Harbor Drive
West Conshohocken, PA 19428-2959
USA
Phone: 610-832-9585
Fax: 610-832-9555
E-mail: [email protected]
http://www.astm.org
IEC Central Office
3, rue de Verenbe,
P.O. Box 131,
1211 Geneva 20
SWITZERLAND
http://www.iec.ch/home-e.htm
BEAB
1 Station View
Guildford, Surrey, GU1 4JY
UNITED KINGDOM
http://www.beab.co.uk
British Approvals Board for Telecommunications
Claremont House
34 Molesey Road
Hersham, Walton-on-Thames, Surrey KT12
4RQ
UNITED KINGDOM
http://www.babt.co.uk
British Standards Institution
389 Chiswick High Road
London W4 4AL
UNITED KINGDOM
http://www.bsi.org.uk
The Institute of Electrical and Electronic Engineers, Inc.
345 East 47th Street
New York, New York 10017
USA
Phone: 800-678-IEEE (Customer Service)
E-mail: [email protected]
http://www.ieee.org
International Product Safety News
E-mail: [email protected]
http://www.safetylink.com
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Resource Links (cont.)
Japanese Standards Association
1-24, Akasaka 4, Minato-ku
Tokyo 107
JAPAN
Publisher of English translations
of Japanese Industrial Standards.
National Institute of Standards and Technology
Gaithersburg, MD 20899-0001
USA
http://www.nist.gov
National Electric Manufacturers Association
Standards Publication Office
2101 L. Street, N.W., Suite 300
Washington, D.C. 20037
USA
Phone: 202-457-8400
Fax: 202-457-8473
http://www.nema.org
Issues standards for electrical products.
A free catalog is published annually.
OSHA Region V Office
230 South Dearborn Street
Room 3244
Chicago, IL 60604
USA
Phone: 312-353-2220
http://www.osha.gov
TÜV Rheinland of North America, Inc.
12 Commerce Road
Newton, CT 06470
USA
Phone: 203-426-0888
http://www.us.tuv.com
The Standards Council of Canada
Suite 1200
45 O'Conner Street
Ottawa, K1P 6N7
CANADA
Phone: 613-238-3222 or 1-800-267-8220 (Sales Only)
Fax: 613-995-4564
E-mail: [email protected]
http://www.scc.ca
Underwriters Laboratories, Inc.
Publications Stock
333 Pfingsten Road
Northbrook, Illinois 60062
USA
http://www.ul.com
A free catalog of Standards for Safety
is published twice a year.
U.S. Consumer Product Safety Commission
Washington, D.C. 20207
USA
Phone: 800-638-2772
Phone: (Hearing/Speech Impaired) 800-638-8270
E-mail: [email protected]
http://www.cpsc.gov
VDE-Verband Deutscher Elektrotechniker
Merlinstrasse 28
D-63069 Offenbach
FEDERAL REPUBLIC OF GERMANY
http://www.vde.de
Publisher of VDE standards and English translations.
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