Machinery Safety 101

Conveyor System Safety

This entry is part 1 of 1 in the series Con­vey­or systems
  • Con­vey­or Sys­tem Safety

Con­vey­or sys­tems are every­where, from the bag­gage hand­ling sys­tems in air­ports to people movers in air­ports and malls, to pack­age hand­ling, min­ing, and gen­er­al indus­tri­al applications. 

Con­vey­ors range from very small dual-belt con­vey­ors used to move prin­ted cir­cuit boards in and out of board-stuff­ing machines to pneu­mat­ic con­vey­ors mov­ing pel­let­ized plastic from stor­age silos to injec­tion mould­ing machines, to massive troughed-belt min­ing con­vey­ors mov­ing hun­dreds of tons of ore a minute. 

In this art­icle, I’m going to cov­er the basic require­ments for some of the com­mon types of con­vey­ors, and I’ll be ref­er­en­cing the most com­mon con­vey­or stand­ards and reg­u­la­tions in use today. I will be exclud­ing all applic­a­tions that involve mov­ing people as I want to focus on the spe­cif­ics of mater­i­al hand­ling con­vey­ors. I’m also going to stay away from spe­cif­ics related to under­ground min­ing con­vey­ors because these have spe­cif­ic safety require­ments related to the mater­i­als and envir­on­ment in which they operate.

Primary Sources

The primary stand­ards sources related to con­vey­ors and used in this art­icle include:

[1] Safety Stand­ard for Con­vey­ors and Related Equip­ment. ASME B20.1. 2018. 

[2] Con­tinu­ous hand­ling equip­ment and sys­tems — Safety and EMC require­ments for mech­an­ic­al hand­ling of bulk mater­i­als except fixed belt con­vey­ors. EN 618. 2002+A1:2010.

[3] Con­tinu­ous hand­ling equip­ment and sys­tems – Safety and EMC require­ments for equip­ment for mech­an­ic­al hand­ling of unit loads. EN 619. 2002 + A1:2010.

[4] Con­tinu­ous mater­i­al hand­ling equip­ment and sys­tems — Safety and EMC require­ments for fixed belt con­vey­ors for bulk mater­i­als. EN 620. 2002 + A1:2010

I’ve included a much more com­pre­hens­ive bib­li­o­graphy at the end of this art­icle if you want to dig deeper.

Defining a Conveyor System

At their most basic, a con­vey­or sys­tem con­sists of a con­tinu­ous mov­ing sur­face that is used to move mater­i­al from one loc­a­tion to anoth­er. Con­vey­ors can be broken down into two basic types, bulk mater­i­al, and pack­age or unit-hand­ling. Bulk mater­i­als range from powders through crushed ores and oth­er types of sim­il­ar mater­i­als. Unit hand­ling con­vey­ors are used to move mater­i­al that is con­tained bags, boxes, pal­lets, or sim­il­ar meth­ods used to con­tain or group oth­er mater­i­al into lar­ger units for handling.

With­in the two basic types of con­vey­ors there are many sub-types, including:

  • Belt
  • Trough
  • Walled
  • Belt Feed­er
  • Buck­et
  • Chain
  • En Masse
  • Flighted
  • Hori­zont­al reciprocating
  • Ver­tic­al reciprocating
  • Pneu­mat­ic (these have some spe­cial requirements)
  • and many more.
conveyor, Conveyor System Safety, Machinery Safety 101
Con­vey­or Com­pon­ents [5]

The dia­gram above comes from A User’s Guide to Con­vey­or Belt Safety pub­lished by the CSST (now called the CNESST) and the IRRST in Mon­tréal, Québec, Canada. This excel­lent guide was avail­able for free down­load in Eng­lish from Ontari­o’s Work­place Safety & Pre­ven­tion Ser­vices (WSPS), how­ever, it was removed from their web­site in Janu­ary 2021. The guide is avail­able as a down­load here. It is still avail­able in French from IRRST. The guide was also adop­ted by Work­Safe Alberta.

Definitions

Let’s get star­ted by com­par­ing the defin­i­tions of con­veys used in the EU versus those used in the USA. I’ll start with the EN 620 [4] definition.

3.2

belt con­vey­or

con­vey­or includ­ing its struc­tur­al com­pon­ents, using a mov­ing belt with a con­tinu­ous rub­ber or poly­mer­ic sur­face for the con­vey­ing medi­um. The belt is usu­ally driv­en by a pul­ley at one end, passing over a free-run­ning pul­ley at the oth­er end. The upper por­tion of the belt may be sup­por­ted by free-run­ning idlers or suit­able flat sur­faces. The con­vey­or may be arranged for hori­zont­al or inclined travel, the angle of slope depend­ing on the char­ac­ter of the goods con­veyed and the type of belt.

EN 620:2010 [2]
Black and white illustration of a flat-belt conveyor
Typ­ic­al flat-belt con­vey­or [6, Fig. 27]

Here’s the US definition:

con­vey­or: a hori­zont­al, inclined, or ver­tic­al device for mov­ing or trans­port­ing bulk mater­i­al, pack­ages, or objects in a path pre­de­ter­mined by the design of the device and hav­ing points of load­ing and dis­charge, fixed or select­ive. Included are skip hoists and ver­tic­al recip­roc­at­ing and inclined recip­roc­at­ing con­vey­ors. Typ­ic­al excep­tions are those devices known as indus­tri­al trucks, tract­ors, trail­ers, tier­ing machines (except pal­let load tier­ers), cranes, hoists, power shovels, power scoops, buck­et drag lines, trench­ers, plat­form elev­at­ors designed to carry pas­sen­gers or an oper­at­or, man­lifts, mov­ing walks, mov­ing stair­ways (escal­at­ors), high­way or rail­way vehicles, cable­ways, tram­ways, dumb­waiters, pneu­mat­ic con­vey­ors, robots, or integ­ral machine trans­fer devices.

ASME B20.1, 2012 [3]

The US stand­ard has taken pains to include spe­cif­ic types of machines that share char­ac­ter­ist­ics with con­vey­ors and may be con­fused with them, while the EU stand­ard has a more straight-for­ward defin­i­tion. The core of the two defin­i­tions are essen­tially the same, a mov­ing sur­face used to move mater­i­als from here to there.

Hazards

There area few com­mon haz­ards present on every con­vey­or system:

  • Entan­gle­ment (in-run­ning nip between the belt and all pul­leys and rollers, wire stitches at the belt join, and the con­veyed mater­i­al, etc.)
  • Entan­gle­ment in the drive system
  • Abra­sion from the mov­ing belt
  • Crush­ing in belt-ten­sion­ing devices and oth­er parts of the mechanism
  • Sever­ing in screw conveyors

There are many oth­er haz­ards need to be con­sidered, but let’s look at these first.

Entanglement

Con­vey­or-related injur­ies typ­ic­ally involve a work­er­’s hands or fin­gers becom­ing caught in nip points or shear points on con­vey­ors and may occur in these situations:

  • Clean­ing and main­tain­ing a con­vey­or, espe­cially when it is still operating.
  • Reach­ing into an in-going nip point to remove debris or to free jammed material.
  • Allow­ing a clean­ing cloth or an employ­ee’s cloth­ing to get caught in the con­vey­or and pull the work­er­’s fin­gers or hands into the conveyor.
  • Cloth­ing or oth­er objects like ID badge lan­yards can be snagged by dam­aged steel wire stitch­ing attach­ing the belt mater­i­al’s ends.

Oth­er con­vey­or-related haz­ards include improp­erly guarded sprock­et and chain drives. Over­head con­vey­ors war­rant spe­cial atten­tion because most of the con­vey­or’s drive train is exposed. Mater­i­als car­ried by over­head con­vey­ors, and broken con­vey­or com­pon­ents can fall from the con­vey­or sys­tem. Employ­ees have also been injured while step­ping or walk­ing on or near con­vey­ors. [6]

Entan­gle­ment injur­ies fre­quently occur when con­vey­ors are manu­ally cleaned. Work­ers using flat blades or oth­er tools to scrape mater­i­al from belts on the return side are often drawn into in-run­ning nip points when the tools they are using, their cloth­ing or hands become entangled in the mov­ing parts of the conveyor.

Belt-drives and chain-drives used to power the head pul­ley are com­mon main­ten­ance loc­a­tions that also involve sig­ni­fic­ant risks of entanglement.

Abrasion

Mov­ing flat belts will cause abra­sion injur­ies to work­ers whose hands, arms, or oth­er body parts come into pro­longed con­tact with the belt. Some of the haz­ard comes from the sur­face fin­ish of the belt itself, as well as the char­ac­ter­ist­ics of the belt mater­i­al itself. Addi­tion­ally, small particles of the mater­i­al car­ried by the belt, includ­ing dirt and grit that may be car­ried onto belts used for unit loads such as card­board boxes can increase the abras­ive­ness of the belt.

There are abra­sion haz­ards cre­ated by the mov­ing sur­faces of the head and tail pul­leys and the idler rollers along the length of the con­vey­or. Dam­age that occurs to the sur­face of the pul­leys can increase the abras­ive­ness of these sur­faces, while some con­vey­or sys­tems use knurled sur­faces to increase fric­tion between the head pul­ley and the belt.

Crushing

Belt ten­sion­ing devices, par­tic­u­larly by coun­ter­weights used to main­tain belt ten­sion auto­mat­ic­ally cre­ate crush­ing haz­ards under the coun­ter­weight, and in oth­er types of ten­sion­ing mech­an­isms. Pneu­mat­ic cyl­in­ders and mech­an­ic­al springs can cre­ate crush­ing haz­ards in the mech­an­isms, and add trapped energy haz­ards that can cause cata­stroph­ic injur­ies if the belt should break dur­ing maintenance.

Oth­er types of con­vey­ors, like buck­et con­vey­ors for example, bring their own types of crush­ing hazards.

Severing

Screw con­vey­ors com­monly used for mov­ing swarf away from the work­ing areas on CNC lathes and used to move all kinds of par­tic­u­late mater­i­als have inher­ent shear points in the areas where the screw passes fixed parts of the con­vey­or tube. These shear points cre­ate sever­ing haz­ards, as well as sig­ni­fic­ant entan­gle­ment and draw­ing-in haz­ards. Screw con­vey­ors can eas­ily shear parts of tools and oth­er objects that may be put into the con­vey­or feed openings.

Controls

Guard­ing con­vey­or sys­tems effect­ively can be a chal­lenge since access to some of the mov­ing parts of the con­vey­or is required for nor­mal use, how­ever, head and tail pul­leys, drive and ten­sion­ing sys­tems can be effect­ively guarded with some thought and plan­ning. Some gen­er­al con­trols you might use include the fol­low­ing [6]:

  • Install guards for all sprock­ets, chains, rollers, belts, and oth­er mov­ing parts. Guard­ing by loc­a­tion – loc­at­ing mov­ing parts away from employ­ees to pre­vent acci­dent­al con­tact with the haz­ard point – is one option for guard­ing con­vey­ors. It is par­tic­u­larly dif­fi­cult, how­ever, to use this meth­od when guard­ing the in-going nip points on cer­tain con­vey­ors such as roller con­vey­ors because the exposed rollers are cru­cial to the func­tion of the conveyor.
  • Use prom­in­ent warn­ing signs or lights to alert work­ers to the con­vey­or oper­a­tion when it is not feas­ible to install guard­ing devices because they inter­fere with the con­vey­or’s operation.
  • Ensure that all con­vey­or open­ings such as wall and floor open­ings, and chutes and hop­pers, have guards when the con­vey­or is not in use.
  • Ensure that start but­tons have guards to pre­vent acci­dent­al operation.
  • Ensure that con­vey­or con­trols or power sources can accept a lockout/tagout device to allow safe main­ten­ance prac­tices. For cros­sov­ers, aisles, pas­sage­ways, you need to do the following:
  • Ensure that all accesses and aisles that cross over or under or are adja­cent to the con­vey­or have adequate clear­ance and hand­rails or oth­er guards.
  • Place cros­sov­ers in areas where employ­ees are most likely to use them.
  • Ensure that all under­passes have pro­tec­ted ceilings.
  • Post appro­pri­ate haz­ard warn­ing signs at all cros­sov­ers, aisles, and passageways.
  • Con­sid­er­ing emer­gency egress when determ­in­ing the place­ment of cros­sov­ers, aisles, and pas­sage­ways. For emer­gency stops or shut-offs, you will need these engin­eer­ing controls:
  • Equip con­vey­ors with inter­lock­ing devices that shut them down dur­ing an elec­tric­al or mech­an­ic­al over­load such as product jams or oth­er stop­pages. When con­vey­ors are arranged in a series, all should auto­mat­ic­ally stop whenev­er one stops.
  • Equip con­vey­ors with emer­gency stop con­trols that require manu­al reset­ting before resum­ing con­vey­or operation.
  • Install clearly marked, unob­struc­ted emer­gency stop but­tons or pull cords with­in easy reach of workers.
  • Provide con­tinu­ously access­ible con­vey­or belts with emer­gency stop cables that extend the entire length of the con­vey­or belt to allow access to the cable from any point along the belt.

Guides

Learn more from these guides. You can down­load the ori­gin­al guides below.

683 down­loads 1.0 Doug Nix 2019-05-01 9:26

References

The con­vey­or stand­ards lis­ted below are invalu­able ref­er­ences when safe­guard­ing conveyors.

[1] Safety Stand­ard for Con­vey­ors and Related Equip­ment. ASME B20.1. 2018.

[2] Con­tinu­ous hand­ling equip­ment and sys­tems — Safety and EMC require­ments for mech­an­ic­al hand­ling of bulk mater­i­als except fixed belt con­vey­ors. EN 618. 2002+A1:2010.

[3] Con­tinu­ous hand­ling equip­ment and sys­tems – Safety and EMC require­ments for equip­ment for mech­an­ic­al hand­ling of unit loads. EN 619. 2002 + A1:2010.

[4] Con­tinu­ous mater­i­al hand­ling equip­ment and sys­tems — Safety and EMC require­ments for fixed belt con­vey­ors for bulk mater­i­als. EN 620. 2002 + A1:2010.

[4] Advanced Design of Recyc­ling Machines, Con­vey­or belt mov­ing WEEE for sort­ing. 2019.

[5] L. Giraud, S. Massé, J. Dubé, L. Schreiber, A. Turcot, A User’s Guide to Con­vey­or Belt Safety, 2nd ed. Mon­tréal: CSST – Com­mis­sion de la santé et de la sécur­ité du trav­ail du Québec, 2003.

[6] Occu­pa­tion­al Safety and Health Admin­is­tra­tion. “Safe­guard­ing Equip­ment and Pro­tect­ing Work­ers from Ampu­ta­tions Small Busi­ness Safety and Health Man­age­ment Series”, Osha.gov, 2001. [Online]. Avail­able: https://www.osha.gov/Publications/OSHA3170/osha3170.html. [Accessed: 2021-04-16].

[7] R. Swin­der­man, A. Mar­ti and D. Mar­shall, Found­a­tions for Con­vey­or Safety, 1st ed. Stevens Point, WI: Mar­tin Engin­eer­ing Com­pany, 2016. [Avail­able: https://www.martin-eng.com/content/product_subcategory/667/conveyor-belt-safety] Accessed: 2019-05-01.

Bibliography

AMERICAN SOCIETY OF MECHANICAL ENGINEERS. Safety stand­ard for con­vey­ors and related equip­ment : an Amer­ic­an nation­al stand­ard, New York, ASME, 2009, viii, 14, 2 p. (ASME B20.1 – 2009). 

ASSOCIATION FRANÇAISE DE NORMALISATION. Engins de manuten­tion con­tin­ue : trans­por­teurs à courroies : exemple de pro­tec­tion des points de coince­ment sur les roul­eaux, Par­is, AFNOR, 1985, 11 p. (AFNOR H 95 – 106 1985). 

«Con­voyeurs», dans QUÉBEC. Règle­ment sur la santé et la sécur­ité du trav­ail, c. S‑2.1, r. 13, à jour au 6 mars 2012, Québec, Éditeur offi­ciel du Québec, 2012, sec­tion XXIII, art. 265 – 271. 

CONVEYOR EQUIPMENT MANUFACTURERS ASSOCIATION, et AMERICAN NATIONAL STANDARDS INSTITUTE. Belt con­vey­ors : unit hand­ling con­vey­ors, Naples, Flor., CEMA, 2002, ii, 24 p. (ANSI/CEMA 402‑2003).

CONVEYOR EQUIPMENT MANUFACTURERS ASSOCIATION, et AMERICAN NATIONAL STANDARDS INSTITUTE. Belt driv­en live roller con­vey­ors : unit hand­ling con­vey­ors, Naples, Flor., CEMA, 1997, ii, 16 p. (ANSI/CEMA 403‑2003).

CONVEYOR EQUIPMENT MANUFACTURERS ASSOCIATION. Bulk mater­i­al belt con­vey­or trough­ing and return idlers : selec­tion and dimen­sions, Naples, Flor., CEMA, 2001, 40 p. (CEMA 502‑2001).

CONVEYOR EQUIPMENT MANUFACTURERS ASSOCIATION, et AMERICAN NATIONAL STANDARDS INSTITUTE. Chain driv­en live roller con­vey­ors : unit hand­ling con­vey­ors, Naples, Flor., CEMA, 2000, ii, 12 p. (ANSI/CEMA 404‑2003).

CONVEYOR EQUIPMENT MANUFACTURERS ASSOCIATION, et AMERICAN NATIONAL STANDARDS INSTITUTE. Lineshaft driv­en live roller con­vey­ors : unit hand­ling con­vey­ors, Naples, Flor., CEMA, 1996, ii, 33 p. (ANSI/CEMA 406‑2003).

CONVEYOR EQUIPMENT MANUFACTURERS ASSOCIATION, et AMERICAN NATIONAL STANDARDS INSTITUTE. Roller con­vey­ors : non powered : unit hand­ling con­vey­ors, Naples, Flor., CEMA, 2002, 17 p. (ANSI/CEMA 401‑2003).

Mater­i­al Hand­ling Industry, Con­vey­or and Sort­a­tion Sys­tems Com­mit­tee. “Applic­a­tion Guidelines for Ver­tic­al Recip­roc­at­ing Con­vey­ors.” Avail­able: https://www.pflow.com/wp-content/uploads/2016/10/vrc-application-guidelines.pdf. Accessed: 2019-04-27.

United States of Amer­ica. DEPARTMENT OF LABOR. MINE SAFETY AND HEALTH ADMINISTRATION. MSHA’s guide to equip­ment guard­ing, rev. 2004, Arling­ton, Vir­gin­ia., MSHA, 2004, 33 p. (Oth­er train­ing mater­i­al; 3), http://www.msha.gov/s&hinfo/equipguarding2004.pdf.

HEALTH AND SAFETY EXECUTIVE. Con­vey­or belt work­sta­tion design, Sud­bury, Suf­folk, G.-B., HSE, 2012, 14 p., http://www.hse.gov.uk/pubns/geis4.pdf.

«Mesur­es ergo­nomiques par­ticulières», dans QUÉBEC. Règle­ment sur la santé et la sécur­ité du trav­ail, c. S‑2.1, r. 13, à jour au 6 mars 2012, Québec, Éditeur offi­ciel du Québec, 2012, sec­tion XX, art. 166. 

STANDARDS AUSTRALIA INTERNATIONAL. Aus­trali­an stand­ard : con­vey­ors : safety require­ments, 3rd ed., Sydney, Aus­tralia, Stand­ards Aus­tralia Inter­na­tion­al, 2000, 86 p. (AS 1755 2000). 

SUVA. Liste de con­trôle : trans­por­teurs à bande pour marchand­ises en vrac, Lausanne, Suva, 2004, 4 p. 

«Tech­niques de manuten­tion», dans QUÉBEC. Règle­ment sur la santé et la sécur­ité du trav­ail, c. S‑2.1, r. 13, à jour au 6 mars 2012, Québec, Éditeur offi­ciel du Québec, 2012, sec­tion XXIII, art. 243 – 244. 

VIA PRÉVENTION. “Prin­cipes de base pour la manuten­tion,” [Mon­tréal], Via Préven­tion, [2012], 2 p. (Procé­dure sécuritaire de trav­ail), http://www.viaprevention.com/upload/viaprevention/publications/2012731143829 – 2.pdf .

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