Technical Article Emergency Stop Switches A Technical .

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Technical ArticleEmergency Stop SwitchesA Technical Guide for Proper SelectionEmergency stop switches, generallyreferred to as E-Stops, ensure the safetyof persons and machinery and providea consistent, predictable, failsafe control response. A wide range of electricalmachinery must have these specialisedswitch controls for emergency shutdownto meet workplace safety and establishedinternational and U.S. regulatory requirements. E-Stops – critical human machineinterface (HMI) devices – differ from simplestop switches (that merely turn equipmentoff) in that they offer “foolproof” equipment shutdown. This is accomplishedthrough advanced switch design thatrequires a twist, pull, or key to releaseelectrical contacts to allow machineryrestart.www.eao.comE-Stops are generally designed for failsafeoperation so the stop command has priority over the sustaining function. This hasled to innovative switch designs thatprevent “blocking” (wanton or accidentalobstruction of the actuator with foreignobjects) and “teasing” (which could resultin premature or unreliable action). Switchcompanies also are developing newsolutions to problems that arise whencontact block and actuator are improperlyinstalled or separated because of vibrationor other malfunction.creating additional hazards. Resetting theelectrical system can only be done by firstreleasing the E-Stop that was originallyactivated. If E-Stops were activated atmultiple locations, all must be releasedbefore machinerySafe emergency stoppingErgonomic, electrical, mechanical, andcolour requirements for E-Stops are quitespecific. The E-Stop control, commonly adistinctive pushbutton switch or “mushroom type” pushbutton (although wires,ropes, bars, handles, or foot pedals aresometimes employed), must use directAccording to international standards, theemergency stop function must be initiatedby a single human action using a manuallyactuated control device. The E-Stopfunction must be operational at all timesand designed to stop the machine withoutE-Stops are critical to the human machineinterface (HMI). restart. It should be notedthat resetting E-Stops does not in itselfrestart the machinery; it only permitsrestarting through normal proceduresappropriate for the machinery involved.

Not all stop E-Stops are made the same. Designers need to have a thorough knowledge ofE-Stop fundamentals, E-Stop switch characteristics and capabilities, and the internationaland U.S. standards and compliance requireEmergency Stop Switchesments.J. Torzillo, L. ScottFigure 1 – Parts of an E-Stop“Actuators can be “teaseproof,” twist-to-release, andfoolproof in design.”Figure 1 – Parts of an E-Stop“E-Stops typically offer a range1of contact options includinggold over silver or silver overpalladium, and silver-platedscrew terminals with availablequick-connect terminals.”2EMERGENCY-STOPPUSHBUTTON ACTUATORActuators should be precision molded fromhigh quality polymeric materials to assure amechanical life in excess of 6,050 operationsas required by industry standards, includingEN IEC 60947 5-5, paragraph 7.3.3. Inreal life, E-Stops generally exceed 250,000operations. Actuators can be “teaseproof,” twist-to-release, and foolproof indesign. Actuators can also be pushbutton,mushroom, or key release.SEALINGMany E-Stops are sealed to IP 65 oil andwatertight standards.3FRONT PLATEFront plates can be designed to conformto color and legend standards.4FIXING NUTE-Stops have a variety of mountingoptions, for use in 22.5 mm or 16 mmpanel openings.5SWITCHING ELEMENTE-Stops typically offer a range of contactoptions including gold over silver or silverover palladium, and silver-plated screwterminals with available quick-connectterminals.www.eao.com.23/8

E-Stops are required on all machinery independent of the type of energy used to controlthe function, except for machines in which anE-Stop function would not lessen the risk.Equipment designers must also consider a rangeof other safety functions.“One of the first steps isdetermining where the E-Stopfits within your machine controlsystem.”vehicles may differ significantlyfrom those used on processmachinery or medical equipment and will be governed bydifferent regulatory bodiesspecific to those segments.Regulatory bodies may alsospecify size, colour, legend,contact terminals, etc.“Check what international andU.S. standards, performanceratings, and codes apply foryour application.”E-Stops may require shorter behind-panel depth.mechanical action with mechanical latching. When the E-Stop isactivated (pushed), it permanently opens the electrical contactsthrough a latching mechanism. To close the electrical contactsand allow machinery restart, the E-Stop actuator must bemanually unlatched with a twist or a key release. Some E-Stopactuators can simply be pulled to close the electrical contacts.This approach may be less desirable from a safety standpointthan a twist or key release, which requires a more deliberateaction by an operator.Selecting the right E-Stop for your applicationBecause of the confusing array of E-Stops available, it is important to understand the design basics that contribute to high-quality, ergonomic switch design. EAO is a leader in HMI Componentsand Systems, including innovative, rugged, reliable, and affordable E-Stops that meet or exceed international and U.S. standards.One of the first steps is determining where the E-Stop fits withinyour machine control system and whether your particular application requires Category 0 or Category 1 type emergency shutdown. The intended application often determines the placement,size, electrical specifications, mechanical characteristics,ergonomics, colour/legends, and number of E-Stops required. Soa thorough understanding of the machinery and associatedcontrol systems is key to making the right E-Stop choice.It is then useful to construct orconsult an existing E-Stopseries selector chart (oftensupplied by vendors). Forexample, EAO provides a chartthat allows easy comparison ofkey design factors (see Figure2). You can select panelopening size, type of actuator,type and number of contactblocks, connectors, colours,and maximum electrical ratingto come up with one or moreappropriate models.Like many vendors, EAOprovides special enclosures,switch guards, palm guards,custom labelling, and otheraccessories to completevirtually any E-Stop application. Some accessories may bespecified by industry standards, such as the SEMIstandards for semiconductorfabrication equipment thatmandate the use of palmguards. EAO and othervendors also offer services toassist customers in the design,engineering, and production ofHMI Systems, integratingE-Stops.Designed for rough dutyA second, and equally important step, is determining whatinternational and U.S. standards, performance ratings, and codesapply for your application. Requirements vary by industrysegment, so standards for E-Stops used on transportationwww.eao.com.3Robust, heavy-duty construction is the hallmark of theoriginal 22.5 mm switches.Many, like the EAO Series 04

E-Stops are covered by standards and regulations of the FDA Department of Health andHuman Services. The key document is CFR Title 21, Part 1020 – Performance Standards forIonizing Radiation Emitting Products, S. 40.“Virtually all industry segments– from machinery, instrumentation, medical treatment anddiagnostic, lifting/ moving, andtransportation – mandateE-Stops for safe operation.”switch characteristics andcapabilities, and the international and U.S. standards andcompliance requirements thatapply to their applicationareas.“Modern applications oftendemand a slimmed downE-Stop with 16mm mounting.”E-Stops are required on allmachinery independent of thetype of energy used to controlthe function, except formachines in which an E-Stopfunction would not lessen therisk. An E-Stop switch isintended to be one part of acomprehensive safety system,so the equipment designermust also consider safetyIlluminated E-Stop used in medical diagnostic treatment.E-Stops, have stackable contact blocks, optional key releaseactuators, and mounting options for 22.5 mm panel openings.This EAO series is rated at up to 10 A, 600 VAC, has silvercontacts with available gold over silver or silver over palladiumcontacts, and silver-plated screw terminals with availablequick-connect terminals.Smaller mounting footprintModern applications often demand a slimmed down E-Stop with16mm mounting. Innovative products, like the EAO Series 61, arenow available with an actuator shape that prevents blockage fromforeign objects, a black indicator ring visible from long distances,and available key release actuators. This EAO series is rated at 5A, 250 VAC, and has a choice of silver or gold contacts, screw orsolder quick-connect terminals.Short behind-panel depthNewer electronic applications are requiring E-Stops with shorterbehind-panel depth. EAO’s Series 84 E-Stop, for example,features a very short behind-panel depth (18 mm maximum),single “mono-block” construction, 22.5 mm mounting, andavailable LED illumination that is visible from the side as well asfront of the actuator. This series is rated at 3A, 120VAC and 1.5A,240VAC, has gold contacts, quick-connect/solder printed circuitboard terminals, and ribbon cable terminals.ApplicationsVirtually all industry segments – from machinery, instrumentation,medical treatment and diagnostic, lifting/ moving, and transportation – mandate E-Stops for safe operation. Designers need tohave a thorough knowledge of E-Stop fundamentals, E-Stopwww.eao.com.4Figure 2 - Key Design Factors22.5 mm panel opening16 mm panel openingISO 13850 (formerly EN418)“Tease-Proof” actuatorStackable contact blocks/elementsShort “behind-panel” depth(18 mm max)IlluminationCap colour other than redScrew terminals Quick-connect/solder terminalsRibbon cable terminalsSealed to IP 65 oil and watertightstandardsTwist-to-release actuatorKey-release actuatorEnclosureLegend platesProtective shroudMax rating: 10 A/600 VACMax rating: 10 A/660 VACMax rating: 5 A/250 VACMax rating: 3 A/250 VAC

The pace of change in E-Stop technology issteady, not revolutionary. Established standards, function, and familiarity dictate a certainbeneficial inertia in new E-Stop developments.Emergency Stop SwitchesJ. Torzillo, L. ScottFigure 3 – International standards that apply to Emergency Stops vs. Stop Switches“E-Stops are required on allmachinery independent of thetype of energy used to controlthe function, except formachines in which an E-Stopfunction would not lessen therisk.”“Designers need to have athorough knowledge of E-Stopfundamentals.”Emergency StopStop SwitchGeneralColor of actuatorActuators of emergency switching off devices shall be colored RED. EN IEC 60947-5-5 § 4.2.1 EN 60204-1 § 10.8.3 DIN EN ISO 13850 § 4.4.5Not definedActuator/BackgroundWhen a background exists behind the actuator, and as far as it is practicable,it shall be colored yellow. EN IEC 60947-5-5, 4.2.1 EN 60204-1, 10.8.3 DIN EN ISO 13850 § 4.4.5Not definedInscription of actuatorThe direction of unlatching shall be clearly identified when resettingis achieved by rotation of the button. EN IEC 60947-5-5 § 4.2.1Not definedElectrical requirementsUtilization categoriesThe utilization categories shall be AC-15 and/or DC-13 and/or DC-14 in accordancewith EN 60947-5-1. EN IEC 60947-5-5 § 5.1Not definedDirect opening actionAll normally closed contact elements of an emergency stop device shall havea direct opening action (positive opening action). EN IEC 60947-5-5 § 5.2Not necessaryLatchingIt shall not be possible for the emergency stop device to latch-in withoutgenerating the emergency stop signal. EN IEC 60947-5-5 § 6.2.1Not definedResettingResetting of the emergency stop shall only be possible as the result of a manualaction at the location where the emergency stop was initiated. EN ISO 13850, 4.4.4Not definedResettingThe resetting of the latching means shall be by turning a key, by rotation of thebutton in the designated direction, or by a pulling motion. EN IEC 60947-5-5 § 6.3.1Not defined, but usually realized by turninga key, by rotation of the button in thedesignated direction, or by a pulling motion.Robustness ofa button activatorA button actuator shall withstand a torque as specified below, in both directions of latchedactuator and unlatched positions, where the resetting action requires rotation of the push-button. EN IEC 60947-5-5 § 7.3.2ØForceTorque16 mm80 N1.6 Nm22 mm110 N2.2 Nm30 mm150 N3.0 NmNot definedDurability testThe test shall consist of 6,050 cycles in which latching and resetting of the actuator occursduring each cycle.The movement and actuating forces shall be consistent throughout thetest. Monitoring of these parameters shall be carried out to ensure consistency. EN IEC 60947-5-5 § 7.3.3Not defined EN IEC60947-5-5 (International Standard) EN ISO 13850 (Safety of Machinery) EN 60204-1 (Safety of Machinery)Not definedTestingNormsMandatory standardsfunctions such as reversal or limitation ofmotion, deflection, shielding, braking, ordisconnecting, that are not specifically addressed in this paper.Primary application areas where electricalmachinery is safeguarded with E-Stop technology include: Metalworking Wood productionwww.eao.com.5 Textile production Food processing Printing Medical laser & x-ray equipment Packaging equipment Semi-fab equipment Pumping Lifting/moving equipment Plastics & rubber processing Materials handling6/8

E-Stops will continue to evolve to meet newstandards and new applications. For designers,the most important considerations in makingthe right design decisions are a thorough understanding of E-Stop functions, and a groundingin the standards, codes, and compliances.“SEMI S2-93 makes a cleardistinction between emergencyoff (EMO) switches andE-Stops.”“Depending on design andapplication requirements,many E-Stops are listed as ULcategory NISD emergency stopdevices.” Electronic production equipment Paper & cardboard

EN IEC 60947 5-5, paragraph 7.3.3. In real life, E-Stops generally exceed 250,000 operations. Actuators can be “tease-proof,” twist-to-release, and foolproof in design. Actuators can also be pushbutton, mushroom, or key release. SEALING Many E-Stops are sealed to IP 65 oil and watertight standards. FRONT PLATE Front plates can be designed to conform to color and legend standards. FIXING .