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Using E-​​Stops in Lockout Procedures

2010 November 29
This entry is part 5 of 10 in the series Emergency Stop

Disconnect Switch with Lock and TagControl of haz­ardous energy is one of the key ways that main­te­nance and ser­vice work­ers are pro­tected while main­tain­ing indus­trial equip­ment. Not so long ago we only thought about ‘Lockout’ or ‘Lockout/​Tagout’ pro­ce­dures, but there is much more to pro­tect­ing these work­ers than ‘just’ lock­ing out energy sources. Inevitably con­di­tions come up where safe­guards may need to be removed or tem­porar­ily bypassed in order to diag­nose prob­lems or to make crit­i­cal but infre­quent adjust­ments to the equip­ment, and this is where Hazardous Energy Control Procedures, or HECP, come in.

One of the ques­tions I often get when help­ing clients with devel­op­ing HECPs for their equip­ment is, “Can we use the emer­gency stop cir­cuit for lock­out?”. As usual, there is a short answer and a long answer to that sim­ple question!

The Short Answer

The short answer to this ques­tion is NO. Lockout requires that sources of haz­ardous energy be phys­i­cally iso­lated or blocked. Control sys­tems may be able to meet parts, but not all of this require­ment. Read on if you’d like to know why.

The Long Answer

Lockout

Lockout pro­ce­dures are now grouped with other adjust­ment, diag­nos­tic and test pro­ce­dures into what are called Hazardous Energy Control Procedures or HECP. In the USA, OSHA pub­lishes a lock­out stan­dard in 29 CFR 1910.147, and ANSI pub­lishes ANSI Z244.1.

Download ANSI standards

In Canada we didn’t have a stan­dard for HECP until 2005 when CSA Z460 was pub­lished, although all the Provinces and Territories have some lan­guage in their leg­is­la­tion that at least alludes to the need for con­trol of haz­ardous energy. In the Province of Ontario where I live, this require­ment shows up in Ontario Regulation 851, Sections 42, 75 and 76.

In the EU, con­trol of haz­ardous energy is dealt with in ISO 14118:2000, Safety of machin­ery — Prevention of unex­pected start-​​up.

Download ISO Standards

If you have a look at the sec­tions from the Ontario reg­u­la­tions, they don’t tell you how to per­form lock­out, and they make lit­tle men­tion of what to do with live work for trou­bleshoot­ing pur­poses. The US OSHA reg­u­la­tions read more like a stan­dard, but because they are in leg­is­la­tion they are pre­scrip­tive. You MUST meet this min­i­mum require­ment, and you may exceed it.

Let’s look at how lock­out is defined in the standards.

Canada (Ontario) USA (OSHA) European Union

Lockout — place­ment of a lock or tag on an energy-​​isolating device in accor­dance with an estab­lished pro­ce­dure, thereby indi­cat­ing that the energy-​​isolating device is not to be oper­ated until removal of the lock or tag in accor­dance with an estab­lished procedure.

CSA Z460, 2005

Lockout. The place­ment of a lock­out device on an energy iso­lat­ing device, in accor­dance with an estab­lished pro­ce­dure, ensur­ing that the energy iso­lat­ing device and the equip­ment being con­trolled can­not be oper­ated until the lock­out device is removed.

Tagout. The place­ment of a tagout device on an energy iso­lat­ing device, in accor­dance with an estab­lished pro­ce­dure, to indi­cate that the energy iso­lat­ing device and the equip­ment being con­trolled may not be oper­ated until the tagout device is removed.

29 CFR 1910.147

2.14 lockout/​tagout: The place­ment of a lock/​tag on the energy iso­lat­ing device in accor­dance with an estab­lished pro­ce­dure, indi­cat­ing that the energy iso­lat­ing device shall not be oper­ated until removal of the lock/​tag in accor­dance with an estab­lished pro­ce­dure. (The term “lockout/​tagout” allows the use of a lock­out device, a tagout device, or a com­bi­na­tion of both.)

ANSI Z244.1–2003


3.3 iso­la­tion and energy dissipation

pro­ce­dure which con­sists of all of the four fol­low­ing actions:

a) iso­lat­ing (dis­con­nect­ing, sep­a­rat­ing) the machine (or defined parts of the machine) from all power supplies;

b) lock­ing (or oth­er­wise secur­ing), if nec­es­sary (for instance in large machines or in instal­la­tions), all the iso­lat­ing units in the “iso­lated” position;

c) dis­si­pat­ing or restrain­ing [con­tain­ing] any stored energy which may give rise to a haz­ard.

NOTE Energy con­sid­ered in c) above may be stored in e.g.:

  • mechan­i­cal parts con­tin­u­ing to move through inertia;
  • mechan­i­cal parts liable to move by gravity;
  • capac­i­tors, accumulators;
  • pres­sur­ized fluids;
  • springs.

d) ver­i­fy­ing by using a safe work­ing pro­ce­dure that the actions taken accord­ing to a), b) and c) above have pro­duced the desired effect.

ISO 14118–2000

As you can see, the def­i­n­i­tions are fairly sim­i­lar, although slightly dif­fer­ent terms may be used. The ISO stan­dard actu­ally pro­vides the best guid­ance over­all in my opin­ion. Note that these excerpts are all taken from the def­i­n­i­tions sec­tions of the rel­e­vant documents.

One of the big dif­fer­ences between the US and Canada is the idea of ‘tagout’ (pro­nounced TAG-​​out for those not famil­iar with the term). Tagout is iden­ti­cal to lock­out with the excep­tion of the device that is attached to the energy iso­lat­ing device. Under cer­tain cir­cum­stances the US per­mits the use of a tag with­out a lock to secure the energy iso­la­tion device. This is not per­mit­ted in Canada under any cir­cum­stance, and the term ‘tagout’ is not offi­cially rec­og­nized. In Canada the term is often taken to mean the addi­tion of a tag to the lock­ing device,  a manda­tory part of the procedure.

Use of Controls for Energy Isolation

This is where the ‘rub­ber meets the road’ — how is the source of haz­ardous energy iso­lated effec­tively? To under­stand the require­ments, let’s look at the def­i­n­i­tion for an Energy Isolating Device.

Canada USA EU

Energy-​​isolating device — a mechan­i­cal device that phys­i­cally pre­vents the trans­mis­sion or release of energy, includ­ing but not lim­ited to the fol­low­ing: a man­u­ally oper­ated elec­tri­cal cir­cuit breaker; a dis­con­nect switch; a man­u­ally oper­ated switch by which the con­duc­tors of a cir­cuit can be dis­con­nected from all ungrounded sup­ply con­duc­tors; a line valve; a block; and other devices used to block or iso­late energy (push-​​button selec­tor switches and other control-​​type devices are not energy-​​isolating devices).

CSA Z460, 2005

Note — Bold added for empha­sis — DN

Energy iso­lat­ing device. A mechan­i­cal device that phys­i­cally pre­vents the trans­mis­sion or release of energy, includ­ing but not lim­ited to the fol­low­ing: A man­u­ally oper­ated elec­tri­cal cir­cuit breaker; a dis­con­nect switch; a man­u­ally oper­ated switch by which the con­duc­tors of a cir­cuit can be dis­con­nected from all ungrounded sup­ply con­duc­tors, and, in addi­tion, no pole can be oper­ated inde­pen­dently; a line valve; a block; and any sim­i­lar device used to block or iso­late energy. Push but­tons, selec­tor switches and other con­trol cir­cuit type devices are not energy iso­lat­ing devices.

Note — Bold added for empha­sis — DN

Tagout device. A promi­nent warn­ing device, such as a tag and a means of attach­ment, which can be securely fas­tened to an energy iso­lat­ing device in accor­dance with an estab­lished pro­ce­dure, to indi­cate that the energy iso­lat­ing device and the equip­ment being con­trolled may not be oper­ated until the tagout device is removed.

29 CFR 1910.147

2.8 energy iso­lat­ing device: A mechan­i­cal device that phys­i­cally pre­vents the trans­mis­sion or release of energy, includ­ing but not lim­ited to the fol­low­ing: a man­u­ally oper­ated elec­tri­cal cir­cuit breaker, a dis­con­nect switch, a man­u­ally oper­ated switch by which the con­duc­tors of a cir­cuit can be dis­con­nected from all ungrounded sup­ply con­duc­tors and, in addi­tion, no pole can be oper­ated inde­pen­dently; a line valve; a block; and any sim­i­lar device used to block or iso­late energy.

2.20.1 tagout device: A promi­nent warn­ing means such as a tag and a means of attach­ment, which can be securely fas­tened to an energy iso­lat­ing device to indi­cate that the energy iso­lat­ing device and the equip­ment being con­trolled may not be oper­ated until the tagout device is removed.

ANSI Z244.1–2003

4.1 Isolation and energy dissipation

Machines shall be pro­vided with means intended for iso­la­tion and energy dis­si­pa­tion (see clause 5), espe­cially with a view to major main­te­nance, work on power cir­cuits and decom­mis­sion­ing in accor­dance with the essen­tial safety require­ment expressed in ISO/​TR 12100–2:1992, annex A, 1.6.3.

Note — ISO/​TR 12100–2 was with­drawn in Oct-​​10 and replaced by ISO 12100–2010. — DN Read more on this.

5.1 Devices for iso­la­tion from power sup­plies
5.1.1
Isolation devices shall:

  • ensure a reli­able iso­la­tion (dis­con­nec­tion, separation);
  • have a reli­able mechan­i­cal link between the man­ual con­trol and the iso­lat­ing element(s);
  • be equipped with clear and unam­bigu­ous iden­ti­fi­ca­tion of the state of the iso­la­tion device which cor­re­sponds to each posi­tion of its man­ual con­trol (actuator).

NOTE 1 For elec­tri­cal equip­ment, a sup­ply dis­con­nect­ing device com­ply­ing with IEC 60204–1:1997, 5.3 “Supply dis­con­nect­ing (iso­lat­ing) device” meets this requirement.

NOTE 2 Plug and socket sys­tems (for elec­tri­cal sup­plies), or their pneu­matic, hydraulic or mechan­i­cal equiv­a­lents, are exam­ples of iso­lat­ing devices with which it is pos­si­ble to achieve a vis­i­ble and reli­able dis­con­ti­nu­ity in the power sup­ply circuits.

For elec­tri­cal plug/​socket com­bi­na­tions, see IEC 60204–1:1997, 5.3.2 d).

NOTE 3 For hydraulic and pneu­matic equip­ment, see also EN 982:1996, 5.1.6 and EN 983:1996, 5.1.6.

ISO 14118–2000


Brady 65675 Large Plug Lockout Device

BRADY Small Plug Lockout Device

As you can see from the above def­i­n­i­tions, all the juris­dic­tions require that devices used for energy iso­la­tion are reli­able, man­u­ally oper­a­ble, mechan­i­cal devices. While elec­tri­cal con­trol sys­tems that meet high lev­els of design reli­a­bil­ity may meet the reli­a­bil­ity require­ments, they do not meet the require­ments for phys­i­cal, mechan­i­cal dis­con­nec­tion of the source of haz­ardous energy. Operator devices are specif­i­cally excluded from this use in Canada and the USA. Note that plug and socket com­bi­na­tions are per­mit­ted in all juris­dic­tions. Lockout devices such as Brady 65675 Large Plug Lockout Device like the Brady Small Plug Lockout Device shown here and sim­i­lar devices can be used for this pur­pose. With some plugs it is pos­si­ble to put a small lock through a hole in one of the con­tacts. In some juris­dic­tions, even the sim­ple act of putting the plug in your back pocket while con­duct­ing the work is sufficient.

In addi­tion, the energy iso­la­tion device is required to be able to be locked in the off, iso­lated, or blocked posi­tion. There are emer­gency stop but­ton oper­a­tors that can be pur­chased with an inte­grated lock cylin­der, and there are some con­trol oper­a­tor acces­sories avail­able that will allow con­trol push but­tons and selec­tor switches to be locked in one posi­tion or another, but these do not meet the require­ments of the above stan­dards. They can be used in addi­tion to an energy iso­la­tion device as part of the pro­ce­dure, but not on their own as the sole means of pre­vent­ing unex­pected start-​​up.

BRADY Button Locking Device

BRADY Button Locking Device

Conclusions

Each machine or piece of equip­ment is required to have an HECP that is spe­cific to that piece of equip­ment. ‘Global’ HECP’s are sel­dom use­ful except as a tem­plate doc­u­ment. Development of HECPs takes some care­ful thought and a thor­ough under­stand­ing of the kinds of work that will need to be done to main­tain and ser­vice the machin­ery. Individual juris­dic­tions have some dif­fer­ences in the details of their reg­u­la­tions, but ulti­mately the require­ments come down to the same thing: Protecting workers.

Control sys­tem devices such as stop but­tons and emer­gency stop devices are not accepted as energy iso­lat­ing devices and can­not be used for this pur­pose, although they may be used as part of the HECP shut­down pro­ce­dure lead­ing up to the phys­i­cal iso­la­tion of the haz­ardous energy sources.

Excellent stan­dards exist that cover devel­op­ment of these pro­ce­dures and should be ref­er­enced as spe­cific HECP are developed.

5% Discount on All Standards with code: CC2011

104602 — BRADY Button Locking Device

BRADY Button Locking Device

References

Canada

Ontario Regulation 851, Sections 42, 75 and 76.

CSA Z460-​​05 (R2010) — Control of haz­ardous energy — Lockout and other methods

USA

29 CFR 1910.147The con­trol of haz­ardous energy (lockout/​tagout).

ANSI Z244.1 — 2003 (R2008) — Control of Hazardous Energy – Lockout/​Tagout and Alternative Methods

Download stan­dards

Allen-Bradley 8579

Allen-​​Bradley 8579

International

ISO 14118 2000, Safety of machin­ery — Prevention of unex­pected start-​​up

Download ISO Standards

Post By Doug Nix (95 Posts)

+DougNix is Managing Director and Principal Consultant at Compliance InSight Consulting, Inc. (http://​www​.com​pli​an​cein​sight​.ca) in Kitchener, Ontario, and is Lead Author and Managing Editor of the Machinery Safety 101 blog.

Doug’s work includes teach­ing machin­ery risk assess­ment tech­niques pri­vately and through Conestoga College Institute of Technology and Advanced Learning in Kitchener, Ontario, as well as pro­vid­ing tech­ni­cal ser­vices and train­ing pro­grams to clients related to risk assess­ment, indus­trial machin­ery safety, safety-​​related con­trol sys­tem inte­gra­tion and reli­a­bil­ity, laser safety and reg­u­la­tory conformity.

Website: → Compliance inSight Consulting Inc.

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  • Roberta Nelson Shea

    Great com­par­i­son and expla­na­tion! You are quite right that pad­lock­ing the estop is NOT a means of energy iso­la­tion. Instead lock­ing the estop is sim­ply a means of ensur­ing that the estop is not reset, and if all is work­ing as it should and elec­tric­ity is the ONLY source of energy, it means that a reset and re-​​initiation of oper­a­tion would not hap­pen. However there is still elec­tri­cal energy avail­able, since the lock is not an iso­la­tion device.

    In addi­tion, every­one needs to remem­ber that energy iso­la­tion (and lock-​​out) is NOT just about elec­tri­cal energy. Usually there are mul­ti­ple sources of energy.

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