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Part

AGENDA OF THE CEMA ENGINEERING CONFERENCE BULK HANDLING SAFETY COMMITTEE MEETING

Monday, June 26, 2017 – 1:40 PM

1. Call To Order

2. Get member to take minutes

3. Roll Call and Introductions

4. Approval of Minutes from Safety Committee Meeting – June 20, 2016. (Attached)

5. Old Items

a. Review the document (Bucket Elevator Book, Best Practices in Design, 1st ed., Chapter 11-

Safety) regarding the inspection, servicing, and maintenance of backstops as done in the

Bucket Elevator handbook. A subcommittee needs to be formed to develop a Best Practice

Document from attendees of the Bulk Handling Safety Committee at 2016 Engineering

Committee. Follow-up with current committee, as no activity has taken place. (Attached)

b. Review The E-Stop Application Guide for Bulk Handling Belt Conveyors as discussed with unit

handling group as it has been moved to the Conveyor Controls Committee for (completion)

combined review for final approval. The controls group have developed a document that would

follow the Risk Assessment format. The base document would be for all conveyors with

separate appendices for unit conveyors and bulk conveyors. Update Available. (Attached)

c. Review updated additions from ASME B20 1.1, 5.16 on risk assessment and Best practices

for guarding on Bucket Elevators. (Attached)

6. New Items for Discussion

a. Set up subcommittee to develop Best Practice Document for inspection, servicing, and

maintenance of backstops.

b. Trip/safety hazards in regards to self-unloading portable rail car systems (Attached)

c. Fire / Explosion preventive measures (Attached)

d. ANSI/ISO vs. CEMA Safety Labels Discussion (Attached)

THE VOICE OF THE NORTH AMERICAN CONVEYOR INDUSTRY

Conveyor Equipment Manufacturers Association


7. New Business8. Next Meeting - June 25, 2018 - LaPlaya Hotel, Naples, FL9. Adjourn


MINUTES OF THE CEMA ENGINEERING CONFERENCE

BULK HANDLING SAFETY COMMITTEE MEETING

Monday, June 20, 2016 – 1:40 PM

Meeting was conducted during the 2016 Engineering Conference at the LaPlaya Hotel on

Monday June 20, 2016

• Meeting was called to Order by Rick Tschantz of Imperial Technologies, Inc. at 1:40 PM

• Roll Call and Introductions were conducted where 46 associates attended the Bulk Handling Safety

meeting- see attached attendee list

• 2016 Proposed agenda was reviewed and approved without additions

• 2015 Minutes from Safety Committee Meeting – June 22, 2015 was reviewed and approved without

additions.

• Old Items

a. Todd Swinderman of RToddS Engineering, LLC presented and discussed the newly adopted

CEMA Technical Report 2015-01 Recommended CEMA Risk Assessment Process. This

document is referenced in the 2015 edition of the ASME B20.1, 5.16.

b. Manufacturers of Bulk Handling equipment were encouraged to review the technical report

and share with associates and clients while putting costs realized due to accidents and what

savings can be realized by proper engineering and implementation of the risk assessment

programs to develop a Safe, Reliable, Productive, and Profitable operating system.

c. Raul Morales submitted stand-alone document regarding the inspection, servicing, and

maintenance of backstops. This was work shared from the work being done for the Bucket

Elevator handbook and will be continued by setting up a subcommittee that will develop Best

Practice Document from return emails of each of the associates in attendance at this

meeting in lieu of attendance sheet signage.

d. The E-Stop Application Guide for Bulk Handling Belt Conveyors was discussed briefly. It was

agreed to not have a separate document from the unit handling group as it was agreed to

Conveyor Equipment Manufacturers Association


move this committee work to the Conveyor Controls Committee during the next afternoon

meeting session for combined review for final approval. The controls group would develop a

document that would follow the Risk Assessment format. The base document would be for

all conveyors with separate appendices for unit conveyors and bulk conveyors.

• New Items

a. A Subcommittee will be developed to review and make recommendations for backstop

safety for next year’s review. Those in attendance at the Bulk safety meeting are asked by

return email to be included on the committee for further action.

b. Review updated additions from ASME B20 1.1, 5.16 on risk assessment and Best practices

for guarding on Bucket Elevators.

• Next Meeting – June 26, 2017 – La Playa Hotel, Naples, FL

• Adjourned at 3:10.

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CEMA Bucket Elevator Book - Best Practices in Design - 1st Edition Chapter 11 - Safety

Chapter 11

SAFETY

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BUCKET ELEVATOR SAFETY

Elevator moving parts operate unguarded by necessity of function, i.e. belts, chain, pulleys, rollers, buckets, pans, etc., create hazards to be avoided. We strongly recom-mend that equipment erectors, operators and maintenance personnel use a LOCK-OUT/TAGOUT safety procedure whenever installing or servicing equipment, and that all affected personnel receive training in safety practices, including awareness of haz-ard areas to be avoided. In addition, the use of proper tools and methods can prevent accidents that can result in severe injury to all affected personnel.

Since individual bucket elevator designs vary by manufacturer, it is critical to follow the manufacturer’s owner’s manual applicable to the specific elevator being erected or serviced. A number of safety instructions are listed throughout owner’s manual. They shall be designated by a black triangle around a white exclamation point and the word WARNING in bold letters.

Reference http://www.cemanet.org/safety-label-placement-guidelines/; Bucket Elevators SC-4.

These instructions alert affected personnel of hazard areas or unsafe procedures. Study them carefully and follow them, insist that those working with you do the same, since accidents are often caused by carelessness or negligence. These safety instructions are not all-inclusive as each application and operating environment is different. The elevator must be operated in accordance with all installation and safety instructions in this manual.

General Safety PrecautionsTaking into consideration all of the physical aspects of the installation, any or all of the following safeguards are required to protect the operators or those working in the immediate area of the elevator.

1. HOPPER GRATINGS — Open hoppers should be provided with protective grating to prevent contact with moving bucket line by personnel. Material in feed hopper must not be poked or pushed with any item.2. GUARDS — For protection of operator and other persons in working area, all bucket elevators shall be equipped with guards for all exposed equipment such as drives, gears, shafts, couplings, etc. These guards must comply with all applicable national, state (or province) and local safety regulations. (Reference OSHA1910.219F )3. ELECTRICAL EQUIPMENT — Electrical equipment conforming to the National Electrical Code or the National Electrical Safety Code, including requirements for the environment, should be considered for the following func-tions:

a. Overflow Devices: Electrical interlocks to warn personnel and shut off power whenever dischargeof elevator is interrupted.b. Overload Protection: To shut off power whenever operation of elevator is stopped as a result ofexcessive material, foreign objects, excessively large lumps, etc.c. Zero Speed Protection: Devices such as zero speed switches to shut off power in the event of anyincident which might cause elevator to cease operating.d. Safety Shutoff Switch: With power lock-out provision at elevator drive.e. Emergency Stop Switches: Readily accessible wherever required and known to proper personnel.

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f. Electrical Interlocking: To shut down feeding conveyor whenever a receiving elevator stops.g. Signal Devices: To warn personnel of imminent start up to elevator, especially if started from aremote location.

4. CAUTION PLATES — Caution plates shall be positioned on the elevator at all inspection doors, cleanoutdoors, and access doors. Do not remove or obscure these plates. When painting the equipment, do not paintdirectly over the plates. Reference caution labels at the end of this chapter.

Dust Hazard Explosion Risk

When elevating materials that may pose a dust explosion risk, such as corn, flour, sugar, plastics, wood, coal and certain metals, additional safety equipment should be considered and may be mandated in certain applications. Some of the additional safety equipment that should be considered includes:

Explosion Vents -By installing appropriate explosion vent panels at the elevator head, boot and at intervals along the casing, the pressure generated from a deflagration may be vented and help prevent catastrophic destruction of the elevator. Excessive pressure is relieved through the vents which are engineered specifically for the application. To minimize personnel exposure, vents should start 8 ft to 12 ft above grade and deflector plates should be used at the head to deflect the explosion upward. All explosion vents should vent to the outside.

Figure 11.01 - Explosion Vent

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Explosion Panels and Dust Collection(Reference NFPA 61: Standard for the Prevention of Fires and Dust Explosions in Agricultural)

• All bucket elevator legs 7.4.1, A7.4.1.2-A 7.4.10• Bulk Handling 7.4.2, A7.4.2.1, A7.4.2.2• Dust Control 10.3.1.2, 10.3.2, A10.3.2• Materials other than grain 7.4.3, A 7.4.3.2, A 7.4.3.3• Motors and Drives 7.4.1.4,A 7.4.1.4

Explosion Suppression Systems -By installing appropriate explosion suppression systems at the elevator head, boot and at intervals along the casing, the explosion can be chemically suppressed before there is damage to the elevator. The system is designed to detect the pressure build up during the early stages of the deflagration and inject a chemical suppressant to extinguish the flame before there is an explosion. These systems are engineered specifically for the application and take into consideration the elevator design and the type of hazardous dust within the process.

Figure 11.02a - Typical Elevator Explosion Venting for a Single Casing Leg

Figure 11.02b - Typical Elevator Explosion Venting for a Double Casing Leg

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Explosion Isolation Devices -By installing appropriate explosion isolation devices on the elevator discharge or intake, explosion propagation to other parts of the plant may be prevented. A valve closes upon receiving a signal from an explosion vent panel sensor, pressure sensor or optical device to prevent the passage of flames, glowing embers, or pressure continuing on to other areas of the plant.

Figure 11.04 - Typical Explosion Isolation Devices

Figure 11.03 - Typical Explosion Suppression Devices

Typical Explosion Suppression Devices Installed at Elevator Boot

Typical Explosion Suppression Devices Installed at Elevator Head

Typical Explosion Suppression Devices Installed at Elevator

Casing

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SENSORS AND CONTROLS FOR PREDICTIVE/PREVENTIVE MAINTENANCE

A. BELT BUCKET ELEVATORS

1. BELT SLIPA bucket elevator belt can slip on the head pulley due to:

• Inadequate belt tension between head and boot pulleys• Belt wear and stretch• Worn head pulley lagging• Moisture between the belt and head pulley• Material plug conditions• Changing operating temperatures

This can lead to:• Reduced belt life• Dropped belts• Fires• Explosions (when elevating certain dusty materials such

as corn, sugar, coal, plastics, wood, certain metals)

As such, the belt speed must be monitored on every belt bucket elevator.

When using a constant speed drive, belt slip at the head pulley can be monitored using a single sensor installed at the boot. If the belt slips at the head, the speed of the boot pulley and shaft will reduce proportionally. The sensor at the boot will detect this as a reduction in speed from normal and can provide warning and shutdown signals. When using a variable speed drive, two sensors are required. One sensor is installed on the head shaft, and one sensor installed on the boot shaft. The signals from these sensors are used to determine belt slip from

Figure 11.05 - Typical Sensor Locations

Figure 11.06 - Fire at Elevator Head

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the proportional speed. Additionally, belt slip/under-speed information can be a valuable tool for predictive or preventative maintenance.

Typical belt slip (under-speed) sensor mounted on the boot shaft of a bucket elevator:

2. BEARING TEMPERATURE

Shaft bearings can fail due to:• End of service life• Incorrect or inadequate bearing lubrication• Contamination from material dust

This can lead to:• Catastrophic elevator failure• Fires• Explosions (when elevating

certain dusty materials such as corn, sugar, coal, plastics, wood, certain metals)

As such, all pulley shaft bearing temperatures (head, boot, knee/bend) must be monitored on every belt bucket elevator.

Typical Belt Slip Sensor Belt Slip Sensor-Installed on Elevator Boot Shaft

Figure 11.07 - Belt Slip Sensor

Figure 11.08 -Typical Bearing Temperature

Sensor

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Typical bearing temperature sensors are adjustable in depth. Positively mounted grease through, continuous temperature sensors incorporating NTC Thermistors or RTD’s. When the bearing temperature exceeds a pre-set value, warning and shutdown signals are provided. Additionally, bearing temperature information can be a valuable tool for predictive and/or preventative maintenance.

3. BELT MISALIGNMENT

A bucket elevator belt can misalign near the head or boot due to:• Inadequate belt tension between head and boot pulleys• Worn head pulley lagging• Moisture between the belt and head pulley• Material plug conditions• Head and or boot pulley alignment issues• Out of plumb shaft• Poorly spliced belt• Uneven loading of buckets• Pulleys walking on shafts• Worn our inadequate pulley crown• Material build up on pulley surface

This can lead to:

• Reduced belt life• Damage to elevator casing• Damage to belt edge• Dropped belts• Damage to elevator buckets• Fires• Explosions (when elevating certain dusty materials

such as corn, sugar, coal, plastics, wood, and certain metals)

As such, belt misalignment must be monitored on every belt bucket elevator.

Belt misalignment can be monitored by installing contact style sensors on each side of the head and boot pulleys, in line with the belt.

Typical sensors are force activated, temperature activated or high powered inductive. When the edge of the belt contacts the sensor, warning and shutdown signals are provided. Additionally, belt misalignment information can be a valuable tool for predictive and/or preventative maintenance.

Figure 11.09 - Typical Belt Misalignment Sensor

Figure 11.10 - Belt Misalignment Sensor

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4. PLUG CONDITION

Plug conditions can occur due to:• Inadequate discharge chute size• Buckets thrown into and blocking the discharge• Tramp material blocking the discharge• Excessive feed rate at the inlet• Build-up of sticky material in discharge chute

This can lead to:• Catastrophic elevator failure• Belt slip• Belt misalignment• Broken buckets• Fires• Explosions (when elevating certain dusty materials such as corn, sugar, coal, plastics, wood and certain

metals)

As such, sensors to detect plug conditions should be installed in the area near the head discharge and/or in the area just above the inlet at the boot.

Typical sensors include flush probe or diaphragm style which detect material pushing against the sensor under a plug condition, and providing a signal to shut down the elevator.

Figure 11.11 - Typical Plug Switches

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B. CHAIN BUCKET ELEVATORS

Similar sensors to those used on belt bucket elevators are used to monitor chain bucket elevators. Shaft Speed sensors monitor for a stop condition. This is sometimes via a boot or head shaft mounted speed sensor or via a high powered inductive sensor detecting the chain or bucket movement. The zero speed indicator probes sense the ferrous metal in buckets, and are used to confirm chain movement throughout the system.

Bearing sensors monitor bearing temperature, and plug chute sensors monitor for blocked discharge conditions. Belt Misalignment sensors are not applicable.

WARNING -Whenever using any type of bucket elevator to move materials that could create an explosive dust hazard con-dition, the sensors MUST be approved for the hazardous area where they are to be installed. Class II Division 1, Groups E, F, G.

Additional considerations and precautions should be taken if the area in or around the bucket elevator is a gas hazard area.

Installation should be in accordance with the National Electrical Code for hazardous area locations.

BACKSTOPSA critical component for the safe operation of a bucket elevator is a functional backstop device – also called a holdback -- built into the drive assembly or mounted directly on the head shaft.

When a well designed, built and maintained bucket elevator is unloaded (all buckets empty) it is considered a balanced system, thus its components will not cause rotation of the head and tail shafts in either forward or re-verse direction. As soon as the buckets start filling with material the system becomes unbalanced as the weight of the material will accumulate energy in the arrangement because the loaded buckets on the in-feed side will weigh more than the empty buckets on the discharge side. This is the same condition that applies to inclined con-veyors, which require an anti-runback device to prevent reverse movement of the belts or chains. Such a device is referred to as a backstop, or holdback. Without a backstop, a reversing bucket elevator can rapidly accelerate to a runaway condition, which can kill or injure personnel, damage or destroy drive train components, tear or rip expensive belting, damage chains and buckets, or cause considerable other damage such as casing bending or rupturing. A backstop is in essence a safety device which acts to prevent reverse rotation of the head shaft, in this manner protecting against any of the potential consequences described above from occurring, as well as avoiding the substantial clean-up of material that will accumulate in the boot and lower casings.

Figure 11.12 - Typical Chain Bucket Elevator Sensor

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Backstops can be selected for either low-speed or high-speed use. High speed backstops are typically an integral component of the speed reducer (gearbox) in the drive assembly while low speed shafts are mounted directly on the elevator head shaft, typically on the side opposite the drive. Both backstop styles are designed to be highly reliable when properly selected, used and maintained as recommended by the manufacturer.

High speed backstops should not be used when the drive is not directly coupled to the head shaft, for instance when using a chain drive for the final reduction stage between the gearbox and elevator head shaft, because the chain drive could fail or need maintenance under a loaded condition. Low speed backstops are the preferred arrangement for this drive configuration.

Figure 11.13 - Low Speed Backstop

Figure 11.14 - High Speed Backstop

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Head Assembly with External Backstop – Chain Driven from Reducer to Head Shaft

1. External backstop2. Backstop torque arm3. Torque arm support bracket or stirrup4. Torque arm support

*Guards removed to show coupling arrangement

Figure 11.15 - Head Assembly with External Backstop*

Figure 11.16 - Head Section showing Low Speed Backstop - Chain Drive is on Opposite Side

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A backstop is required in all bucket elevators to ensure safe operation of the system. Additionally, the backstop can be an important aid to avoid runaway conditions during bucket replacement, as the side with more buckets will produce greater gravitational pull than the one with fewer buckets. It is important to note that a proper sequence of bucket installation is required for the backstop to perform its protective function during the procedure, as the discharge side should always have fewer buckets than the inlet side or the chain or belt will rotate in forward direction.

Considerations on backstops:

• A backstop (holdback) IS a mechanical device designed to allow free rotation of a shaft in onlyone direction.

• A backstop IS NOT a brake.• A backstop IS NOT an indexing device.• A backstop IS NOT a jogging device.

Figure 11.17 - Drive with Integral High Speed Backstop at First Intermediate Shaft

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WARNING: Lock out power source and remove all external loads from gear drive system and from backstop before servicing drive or accessories. Locking out the power source and removing the load will reduce the pos-sibility of an unexpected motion or reaction in the system.

Safety considerations required when working on a jammed elevator caused by boot flooding:

If a bucket elevator stops due to a flooded boot condition that overloads the drive, causing it to stall or impeding it from starting, it is critical to clear the accumulated material from the boot section manually through the clea-nout doors before attempting to restart the drive. The motor should be able to resume operating under normal condition for it to empty the loaded buckets. The drive must not be “jogged” to attempt releasing the jam since each jog will increase the energy stored in the system if the drive moves and the buckets do not release from the flooded boot section whilst the backstop is now holding increased system tension. This could lead to potential equipment damage, injuries or death if the belt, chain, backstop or drive fail due to overloading. The condition is especially critical with fabric belting because of its elasticity, in which each partial head shaft rotation will store more energy in the belt.

Figure 11.18 - Flooded elevator boot section must be cleared before attempting to restart.

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Use of Holding Brakes in Lieu of Backstops

Although a fail-safe brake can provide the same capability to impede reverse rotation as a backstop its use is not a preferred selection for design of an elevator. This is because for the brake to have the ability to provide instantaneous engagement in the case of a loss of power or emergency stop, it must be of the spring engaged, electromechanically or electro-hydraulically released type. These brakes will activate almost immediately, so if there is still inertia in the system (in the normal direction of elevator operation) when the brake abruptly stops the inertia could cause damage to components and spillage of material into the elevator boot.

When the drive system is equipped with a fluid coupling or a V-belt drive between motor and reducer a brake should never be installed on the motor shaft. Fluid couplings are not a direct mechanical connection and will allow the gearbox shaft to spin. V-belt drives can slip or fail and are a maintenance item that could cause a hazardous condition if removed while the elevator is loaded. In both of these cases the brake should always be installed directly on the gearbox shaft.

Figure 11.19 - Low Speed Backstop Testing Machine. Due to criticality of safe operation premium manufacturers’ backstops are

fully load tested at factory.

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Figure 11.20 - CEMA Bucket Elevator Safety Poster, Available under the Safety Label in-formation downloaded free at: wwww.cemanet.org

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Figure 11.21 - CEMA Safety Label Placement Guidelines, Available under the Safety Label in-formation downloaded free at: www.cemanet.org

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Conveyor Equipment Manufacturers Association (CEMA)

Safety Best Practices Recommendation CEMA SBP-002 (2016)

E-Stop Application GuideFor Unit and Bulk Material Handling

Conveyor Systems

Provided as a service to the Conveying Industry By The CEMA Engineering Conference

Conveyor Safety Committee

Original Publication Date: 2008 Revision Date: September 12, 2016

1

DISCLAIMER

The information provided in this document is advisory only.

These recommendations are provided by CEMA are general in nature and are not intended as a substitute for professional advice. Users should seek the advice, supervision and/or consultation of qualified engineers, safety consultants, and other qualified professionals.

Any use of this publication, or any information contained herein, or any other CEMA publication is made with agreement and understanding that the user and the user’s company assume full responsibility for the designs, safety, specifications, suitability and adequacy of any conveyor system, system component, mechanical or electrical device designed or manufactured using this information.

The user and the user’s company understand and agree that CEMA, its member companies, its officers, agents and employees are not and shall not be liable in any manner under any theory of liability to anyone for reliance on or use of these recommendations. The users and the user’s company agree to release, hold harmless and indemnify and defend CEMA, its member companies, successors, assigns, officers, agents and employees from any and all claims of liability, costs, fees (including attorney’s fees), or damages arising in any way out of the use of this information.

CEMA and its member companies, successors, assigns, officers, agents and employees make no representations or warranties whatsoever, either express or implied, about the information contained herein, including, but not limited to, representations or warranties that the information and recommendations contained herein conform to any federal, state or local laws, regulations, guidelines or ordinances.

CONVEYOR EQUIPMENT MANUFACTURERS ASSOCIATION 5672 Strand Ct, Suite 2 Naples, Florida 34110

Web Site: http://www.cemanet.org Copyright © 2016

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TABLE OF CONTENTS

1. Definitions

2. Objectives

3. Guidelines Common to All Conveyors

3.1 Application Rules for E-Stop Hardware/Devices

3.2 Placement Rules for E-Stops Affecting All Accessible Powered Equipment

3.3 E-Stop Interlocking

3.4 Inspection and Testing

4. Guidelines Specific to Unit Handling Conveyors


4.2 Primary Placement Rules for E-Stops


4.4 Typical Areas for E-Stop Application

5. Guidelines Specific to Bulk Handling Conveyors


5.2 Placement Rules for E-Stops



6. Special Applications Areas

7. References

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FOREWORD

This document shall be used in conjunction with the applicable current standard of ASME B20.1 “Safety Standard for Conveyor and Related Equipment.”

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1. DefinitionsThe following definitions are both specific to this document and generic to the material handling industry where such definitions can be found.

Accessible, Readily (as applied to E-Stop actuators): The rapid visual contact and recognition of an Emergency Stop (E-Stop) actuator that is capable of being reached quickly for operation without a need to climb over or remove obstacles.

E-Stop Purpose: To disable or stop any motion hazardous to personnel, equipment or product asquickly as is safe and practical without creating additional hazards.

E-Stop Actuator: The mechanism which the operator interfaces with and, in turn, causes the E-Stop device to register an emergency stop state.

E-Stop Application Criteria: Required on equipment on which there is a reasonable potential forinjury to personnel, moving components or conveyables. The potential for injury from fallingconveyables must also be considered.

E-Stop Device: A push-button switch, cable-operated switch, active electronic sensing or othercomponent that is manufactured with the specific intent to be used as an input, logic or outputdevice as part of the E-Stop function.

E-Stop Interlocking: Where an E-Stop associated with one control cabinet will be required toinitiate an E-Stop condition in another control cabinet/E-Stop zone, such as when two independentcontrol areas have transportation conveyors running adjacent to each other en-route to a mergingoperation.

E-Stop Panel: This is an independently powered relay cabinet that will not shut down if one ormore of the interlocked control cabinets are shut down.

E-Stop Zone: The physical area in which all conveyor equipment is stopped when an E-Stopdevice is actuated.

Functional Safety: The part of the overall safety of a system or piece of equipment that depends on the system or equipment operating correctly in response to its inputs, including the safe management of likely operator errors, hardware failures and environmental changes.

General Access Area: Designated passageways/walkways where trained operators will travel between work stations and other areas such as break rooms, offices, restrooms, supply rooms, or other areas employees are required to travel in the course of their normal duties. During the course of travel these operators may utilize stairs, ladders, crossovers, gates, etc. in order to access work stations and may pass under, over or adjacent to operating conveyor equipment.

Guarded by Location Area: Describes areas where moving parts are so protected by their remoteness from the floor, platform, walkway, or other working level or by their location with reference to frame, foundation, or structure as to reduce risk of accidental contact by persons or objects. Remoteness from regular or frequent presence of public or employed personnel may, in reasonable circumstances, constitute guarding by location. Unprotected danger points and areas that are inaccessible to the operating personnel in the normal performance of their duties shall be considered guarded by location.

Lock-Out Device: Any approved device that can be used to lock out or isolate any or all potential energy sources, such as electrical, air, or kinetic, that might cause unexpected movement of machine components. See current edition of ANSI Z244.1 "American National Safety Standards for Lock-out Tag-out of Energy Sources.

Minor Servicing: Activities, which take place during normal production operations and which are routine, repetitive, and integral to the use of machine/equipment for production. Based on the

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NOTE

results of a risk assessment, minor servicing tasks may be determined to be at an acceptable risk level and do not require the use of a lock-out device to isolate power during the task. See OSHA 29 CFR 1910.147 (a)(2)(ii) and ASME B20.1-2015 (5.4).

Observable: Point from which an operator has an unobstructed view and can make a reasonably sound evaluation on the state/condition of a situation (maximum distance of 100 ft)1.

Restricted Access Area: Areas of the material handling system that do not meet the above two defined areas (General Access and Guarded by Location) and do not have a normal presence of trained operators or allow operators to enter this area in the performance of their normal duties.

Work Station: A physical location where a person is normally positioned, which is located by design and supported with facilities necessary for a person to perform prescribed work duties. This position would not apply to maintenance location.

For the purpose of this document, the term “conveyor” applies to all powered material handling equipment that transports a product.

1 Distance based on several studies on effectiveness of eyewitnesses’ ability to recognize fine and gross details at various distances.

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2. ObjectivesThe following objectives form the basis toward which we must strive in E-Stop application. Occasionally, these objectives must be tempered with the realities of practical application such as equipment density, equipment interfaces, and customer operational preferences, which can be evaluated using established risk assessment methods.

● Stop the conveyor motion when a hazardous situation is observed in order to prevent orminimize accidents that may result in injury to personnel, damage to equipment or damageto conveyables.

● Stop the hazardous motion as quickly as possible, without generation of other hazards, inthe event that an accident has occurred.

Do not apply E-Stop equipment in a manner that might entice, encourage or otherwise facilitate unsafe practices.

Do not deviate from the established guidelines or standards without evaluating the safety of those changes in the specific situations using an established risk assessment method.

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3. Guidelines Common to All ConveyorsThe following section contains guidelines which apply generally to all conveyor types.


● Only E-Stop devices that are designed and manufactured with the intent to functionfor that purpose shall be used.

● The use of an E-Stop, to prevent unintentional motion while clearing jams and otherminor servicing, is permitted under the OSHA minor servicing exception, as long asthe person servicing the equipment is in control of the E-Stop.

● E-Stop circuits must be analyzed and designed according to consensus standardsNFPA 79, ISO 13849, or IEC 62061.

● E-Stop circuits, when activated and the stop cycle completes, shall ensure that notorque-generating energy can continue to act upon a motor and also preventunintentional initiation of hazardous motion.

● E-Stop stopping cycle behavior is defined by NFPA 79. For most conveyors, aCategory 0 Emergency Stop will immediately remove power to the conveyoractuators resulting in an uncontrolled stop. When an uncontrolled stop is morehazardous than a controlled stop, the E-Stop shall trigger a Category 1 EmergencyStop. This cycle is a controlled stop where power is not removed until the stop iscomplete.

● The suspension of a safety function must be replaced by another safety functionwith the equivalent performance level.

● E-Stop circuits shall stop air or hydraulic powered devices by interrupting the powersource in such a manner that hazardous motion due to kinetic energy or othermeans does not occur.

● E-Stop electrical devices and systems must be designed such that they requiremanual reset at the point of electrical actuation before a restart sequence can begin.

● Resetting the activated E-Stop device must not automatically restart the equipment.Equipment restart must be initiated by start controls of the associated equipmentonly after the activated E-Stop device has been manually reset, and begin only afterthe normal startup sequence including delays and warnings has occurred.Equipment interlocked with the associated cabinet will also restart (or not) per thesequence of operation. No equipment will restart without appropriate warning anddelay.

● Apply only those E-Stop devices and systems that meet accepted company,industry, engineering, and government standards for performance, appearance, andelectrical design.

● E-Stop switches and actuators must be recognizable and distinct from any othercontrols:

■ The actuator of a pushbutton-operated device shall be of the palm ormushroom head type.

■ E-Stop pushbutton actuators shall be colored red. The backgroundimmediately around an E-Stop pushbutton shall be colored yellow.

■ Pull cords for pull cord switches should be provided in a high visibilitycolor which allows rapid identification.

■ Other E-Stop switches and actuators should be clearly labeled or be ahigh visibility color.

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● E-Stop devices and systems, regardless of type, will effectively stop all hazardousmotion in the controlled E-Stop zone.

● Pull cords shall be tested, at actuation points, to ensure the manufacturer’srecommended performance is within the limits for the maximum deflection and pullforce. An anti-friction device may be used to reduce pull force to extend thedistance when changing direction.

3.2 Placement Rules for E-Stops Affecting All Accessible Powered Equipment

● Apply an approved E-Stop device mounted to or available nearby to all controlcabinets on which there are external controls that stop, start or monitor conveyoroperation.

● Apply E-Stops so that they control all conveyors observable from where that E-Stopcan be actuated, where practical.

● E-Stop devices are not required to be readily accessible to personnel for conveyorsthat are guarded by location, provided such or additional guarding can reasonablyprevent contact with the conveyor and injury to personnel from falling conveyables.

● An E-Stop must be provided at reasonable intervals consistent with equipment typeand density, expected operational parameters, reasonable foreseeable misuse andtraining levels of personnel expected to be in the area.

● Apply an E-Stop at hazards that cannot otherwise be protected in a practicalmanner and are accessible by personnel.

● Extend E-Stop cords to accessible areas where practical, unless additionalelectrical devices would be needed.

● Maintain consistency when determining the functions, locations, arrangements,labeling, and appearance of emergency stop system cords and switches within thesame installation wherever possible.

● For unit handling conveyor E-Stop placement rules refer to section 4.2.● For bulk handling conveyor E-Stop placement rules refer to section 5.2.


E-Stop interlocking applies to situations where an E-Stop device associated with onecontrol cabinet will be required to initiate an E-Stop condition in another control cabinet/E-Stop zone. For example, this occurs when two independent control areas have conveyorslocated adjacent to each and are observable.

● Provide interlocks between independent control sections in an effort to maintaincompliance with the criteria specified in first two bullet points of section 2.

● Provide E-Stop interlock capability for third party equipment expected to be in thearea.

● Interlocks should be provided between independent OEM equipment controls asspecified in section 2, first two bullet points.

E-Stop electrical/electronic interlocking is typically accomplished via one of the methods listedbelow:

● One or more E-Stop relays in each cabinet with contacts wired to other cabinets forinterlocking on a zone-to-zone basis.

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● Single E-Stop device: A single E-Stop device being interlocked to another area canbe equipped with multiple isolated contacts: one set for each control cabinet/E-Stopzone.

● Dedicated E-Stop panel: An E-Stop panel is an independently powered relaycabinet that will not shut down if one or the other interlocked control cabinets isshut down. The E-Stop devices are connected to the E-Stop panel which is theninterlocked to the appropriate control cabinets on a zone-by-zone basis.

● Multiple E-Stop devices: When one or more independently powered E-Stop devicesmust be interlocked to one or more additional cabinets, an E-Stop panel may beemployed to avoid an unnecessary shutdown of interlocked cabinets.

● Safety-rated communication between safety controllers.

Operation of interlocked E-Stop zones is as follows:

● The cabinet associated with the actuated E-Stop device will comply with all rulesspecified in section 3.1.

● The interlocked cabinet E-Stopped zone works as follows:■ When the remote E-Stop device is actuated, the interlocked cabinet/E-

Stop zone immediately goes into an E-Stop shutdown cycle.■ Recommend that the E-Stop indicator on the interlocked control cabinet

will uniquely signal to user (light or sound), indicating that the E-Stopcondition is remote from that controlled area.

■ When the E-Stop device is reset and the associated control cabinet isrestarted, the interlocked cabinet/E-Stop zone may restart after aminimum of a five - second audible alarm. No physical reset in theinterlocked cabinet is required.

3.4 Inspection and Testing

● E-Stops must be validated after installation and before delivery to the end user.The validation process must be documented and performed by qualifiedpersonnel.

● E-Stops must be inspected and tested at a frequency that complements thehazard being guarded. This frequency should be documented as a time period orsystem output in the documentation given to the customer.

● Testing shall be done with the conveyor operating. The safety system responseand feedback must be verified to be consistent with the intended design.

● E-Stop switches and actuators should be clearly labeled or be a high visibilitycolor.

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4. Guidelines Specific to Unit Handling ConveyorsThe following section contains guidelines which apply to unit handling conveyors.


● An E-Stop must be provided at reasonable intervals consistent with equipmenttype and density, expected operational parameters, reasonable foreseeablemisuse and training levels of personnel expected to be in the area.

● When E-Stops are configured to function as lockout devices, the performancemust meet or exceed the performance of a dedicated supply disconnect means.

● Pull cord E-Stop switch systems shall be slack detection type to operate andactivate an emergency stop condition should a cord break or come loose.

● An E-Stop must stop all hazardous motion that is observable from the point ofactuation.

4.2 Primary Placement Rules for E-Stops

● Apply an E-Stop actuator within reach (maximum of 1.5m (5’-0”)) of anydesignated “Work Station” that directly interfaces with powered conveyors. (Seesection 1 for definition of “Work Station”).

● Apply an E-Stop actuator such that “E-Stop access” is provided within 7.5m (25’-0”) for any point along a conveyor in a “general access area”. (See section 1 fordefinitions of “E-Stop access” and “general access area”).

● Apply an E-Stop actuator such that “E-Stop access” is provided within anunobstructed travel distance of 30m (100’-0”) of any point along a conveyor in a“restricted access area”. (See section 1 for definitions of “E-Stop Access” and“Restricted Access Area”).

● The placement rules, listed in the Common Guidelines section 3.2, aresupplementary to the primary.


There are no unique interlocking requirements. Refer to section 3.3 for more information.


The following are examples of typical areas and types of equipment where E-Stops would or could be applied on unit handling conveyors. This section is not intended to be a complete listing of where E-Stops are to be applied, nor does it mandate that E-Stops be applied in all the situations listed.

● Pick modules, picking conveyors■ Conveyor: Cords along the entire accessible length.■ Gates: None if non-powered or often fall under the low hazard exception

determined by established risk assessment methods.■ Accessible feed and take away conveyors unless they are within 7.5m

(25’-0”) of an E-Stop actuating device.● General duty conveyors with operator access: Follow distance requirements in

section 4.2 for the following:■ Belt conveyor

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■ Live roller conveyor (including lineshaft driven and accumulationconveyors)

■ Transfers■ Transportation corridors

● Merges:■ Central (large): Pull cord protection where generally accessible■ Remote (mini): Mushroom switch or pull cord within 7.5m (25 ‘-0”)■ Alligators (pivot belts): Mushroom switch or pull cord where readily

accessible● Induction: Cord along accessible length● Sorters:

■ Slat: Cord along accessible length■ Tube: Cord along accessible length■ Pop-up wheel or roller: Cord along accessible length■ Isolated diverters: Require individual evaluation based on access

● Trailer loaders and unloaders:■ Control station mushroom switch at the end of a decline or incline■ Interlock loader/unloader to feed/takeaway conveyor and other visible

conveyors● Pallet Conveyor:

■ Roller transport or accumulation conveyors. Cord protection or within7.5m (25’-0”) if generally accessible

■ Chain: Cord protection on all generally accessible areas● Transfers: Cord protected if generally accessible; button or cord protection within

sight if not accessible● Scale conveyor● Miscellaneous equipment utilizing conveyor, “Third-party”, such as those

components listed below, the denser coverage of: manufacturer’srecommendations or per these specifications if the supplier integrates theequipment. Individual installations are to be evaluated for additional needs.

● Stretch wrappers● Depalletizers● Palletizers● Strappers/tapers● Those conveyors where moving surfaces and general arrangements qualify under

the low energy exception need not be provided with access to E-Stop devices aslong as all residual hazards are assessed to be at an acceptable risk level.

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5. Guidelines Specific to Bulk Handling ConveyorsThe following section contains guidelines which apply to bulk handling conveyors.


● E-Stop circuits, when activated, shall stop the conveyor as fast as possible withoutdamaging the equipment or creating new hazards. However, uncontrolled stopscan create additional hazards on some conveyors, such as downhill regenerativeconveyors.

● An E-Stop must stop all hazardous motion of associated equipment that isobservable from the point of actuation. This includes all conveyors feeding theconveyor on which the actuator is located on.

5.2 Placement Rules for E-Stops

● Refer to the placement rules, listed in the Common Guidelines section 3.2.● Apply pull cord E-Stops such that “E-Stop access” is provided along the full length

of belt feeders and belt conveyors normally accessible from walkways, floors, orplatforms.

● Apply an E-Stop actuator such that “E-Stop access” is provided within anunobstructed travel distance of 15m (50’-0”) of any point along a conveyor in a“general access area” where pull cord E-Stops cannot be practically applied.


There are no unique interlocking requirements. Refer to section 3.3 for more information.


The following are examples of typical areas and types of equipment where E-Stops would or could be applied. This section is not intended to be a complete listing of where E-Stops are to be applied, nor does it mandate that E-Stops be applied in all the situations listed.

● Bulk Conveyors: Along the carrying run of the conveyor terminating at the headand tail ends of the conveyor.

● Those conveyors where moving surfaces and general arrangements qualify underthe low energy exception need not be provided with access to E-Stop devices aslong as all residual hazards are assessed to be at an acceptable risk level.

● Bulk components and accessories such as sampling devices, magnetic separators,crushers, screens, de-lumpers and any similar equipment that is electricallycontrolled.

● Along the length of travel for tripper or stacking conveyors.● Along the accessible side(s) of shuttle conveyors.● Shall be provided at points where personnel could come in contact with cables,

chains, belts, and runways of exposed bucket conveyors.● Shall be provided on material encapsulating conveyors, unless guarded by location

or position, at unguarded nip points.● Accessible carry and return idlers at convex and horizontal curves.● As determined by risk assessment.

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6. Special Applications or AreasIn areas and applications where the preceding rules do not appear to apply, such as the following, the situation should be analyzed and qualified using established risk assessment methods:

● Hazardous special equipment● Unusual controls configurations● Special operational factors● Sub-standard training levels of personnel with access to the area● Restricted Access Facility

7. ReferencesThe following is an abbreviated list of related references, technical reports, and national and international standards. Referenced documents are for the current versions at the time of publishing this guide

● ASME B20.1 Safety Standard for Conveyors and Related Equipment● ASME B30.13 Storage/Retrieval (SR) Machines and Associated Equipment● CEMA – Technical Report 2015-01 Recommended CEMA Risk Assessment Process● ISO 13849 – Safety of machinery - Safety-related parts of control systems● ISO 12100 – General principles for design — Risk assessment and risk reduction● IEC 62061 - Safety of machinery - Functional safety of safety-related electrical, electronic

and programmable electronic control systems● NFPA 79 - Electrical Standard for Industrial Machinery● RIA R15.06 Industrial Robots and Robot Systems● OSHA CPL 02-00-147 The Control of Hazardous Energy – Enforcement Policy and

Inspection Procedures■ Minor servicing exception -- §1910.147(a) (2) (ii)

● OSHA 29CFR 1910.147 Lock-out/Tag-out● CEMA Belt Conveyors for Bulk Materials, 7th ed., 2014● CEMA Application Guide for Unit Handling Conveyors, 2nd ed., 2016

Risk Assessment for Conveyors

Conveyors and conveying systems are known to have various danger points associated with the conveying of bulk and unit loads. Conveyors have known nip and pinch points that can cause serious injury or death and these risks must be reduced to an acceptable level.

Using the risk reduction methods suggested by the B20.1 standard is a good starting point as it recognizes the CEMA Risk Assessment Program. Conveyors are often used with other conveyors and / or processing machines. They are mostly unattended, remotely located, do not perform work on the product and the loading and unloading is by other equipment.

The risk assessment process determines a level of risk where risk is a combination of probably of occurrence and the severity of that harm. Risk reduction is the application of one or more protective measures. The nip points inherent on conveyors and there drive trains is well documented in the ANSI / ASME Standards B20.1 and B15.1 respectively. These nip points generally fall into the category of harm as Catastrophic or Serious and the probability of harm is very likely or likely meaning they have a high level of risk associated with them. See table 1, copied from ANSI B11-TR#-2000 below.

Probability of Occurrence of Harm

Severity of Harm Catastrophic Serious Moderate Minor

Very Likely High High High Medium Likely High High Medium Low

Unlikely Medium Medium Low Negligible Remote Low Low Negligible Negligible

Table 1: Risk Estimation Matrix

Since the severity of the Harm cannot be eliminated by design the probability of occurrence must be reduced. In the conveyor industry, this is accomplished by guarding. Locations and types of physical guards are covered in OSHA, MSHA, B20.1, B15.1, ISO 5045. Use of these guards will result in a probability of occurrence from inadvertent contact with a pinch or nip point to remote. This results in a Low Risk design. This risk can be further reduced by applying color warnings to guards and moving machine parts or by the use of warning labels such as those recommended by CEMA. A still further risk reduction is applied by the end user or employer. This consists of proper training in LOTO (Lock Out – Tag Out) covered by OSHA 1910.147 and developing safe maintenance procedures for routine preventative maintenance in a JSA (Job Safety Analysis).

One of the difficulties in the conveyor industry is determining who is responsible to carry out a risk assessment. Is it the manufacturer, system integrator, engineer of record or the plant owner/employer. The ultimate responsibility lies with the employer who is obligated by law to provide a safe work place for their employees. The following risk reduction breakdown will outline what risk reduction must be applied at the various segments of a project.

Manufacturer: The manufacturer of a conveyor is responsible to provide all guarding attached to and associated with the known hazards of the conveyor as described in ASME B20. These guards should comply with OSHA/MSHA standards as applicable. The manufacturer should also provide all warning labels and instructions that include warnings on LOTO, not riding on conveyor, and requiring proper training for operators and maintenance personnel. The manufacturer may or may not provide electrical safety and control devices and may or may not provide the power transmission for the conveyor. If these devices are included they become the responsibility of the manufacturer to properly apply these devices.

System Integrator / engineer: The responsibilities of the system integrator and / or engineer depends on the scope of service performed by each entity. They are generally responsible for the system layout, equipment selection and system control. The risk reduction at this phase includes: making sure the manufacturers equipment complies with the specified codes; address all hazards associated with conveyor transfers such as nip points and material spillage; address dusting problems that could lead to dust explosions; provide all barrier guards associated with equipment location; all spillage guarding for material or conveyor components falling from the conveyor; area safety signs and posters and electrical controls. These control relate to the safe operation of the conveyor system. Areas that need to be addressed include: location and type of pull cords and E-Stops, local disconnects at the motor when remote from the mcc, time delays and warning horns/lights when the service area is out of sight from the starting controls. The electrical control system must meet the requirements of the NEC code for design and installation. The system integrator must also provide guards from moving machinery such as trippers and shuttle conveyors. The system integrator is also responsible for conveyor cross under and overs, proper walkways and handrails, system egress and openings in floors and walls. Warning signs that conveyors are remote controlled.

Fire protection and dust explosion protection must be incorporated where large amounts of combustible materials are present such as coal or grain dust. Fires and explosions can be caused by frozen bearings, misaligned belts, frozen rollers, drive pulley slippage, electrical failures, static electricity, tramp iron in the conveyed material, chute plugging or welding to name some of the common causes.

End User / Employer: The employer is responsible to provide the employees a safe place to work. This includes making sure that all the equipment is code complicate and was overseen by a competent engineer, system integrator or manufacturer. The employer must furnish any additional items that are required by were not provided in previous project phases. The employer is responsible to make sure that a comprehensive LOTO program is developed and enforced. The employer is responsible to make sure his employees have the necessary PPE for the work being done. This includes hard hats, gloves, eye protection, safety harnesses, ear protection and respirators. The employer must also identify all hazardous materials in the work place.

The employer must make sure that all employees are properly trained in their job function. They must be trained in LOTO if they are going to work on conveyors. They must also be trained not to ride on moving belts. They must be trained in how to clean under and around conveyors including the cleaning of pulleys. They must be trained to block gravity loads such as conveyor counterweight take-ups. The employer must also establish safe isle ways that are guarded against product or conveyor machinery falling from the conveyors.

Fire Prevention

NFTA References 3.3.15 Dust Explosion Hazard. A dust deflagration hazard in an enclosure that is capable of bursting or rupturing the enclosure due to the development of internal pressure from the deflagration. 3.3.16* Dust Hazards Analysis (DHA). A systematic review to identify and evaluate the potential fire, flash fire, or explosion hazards associated with the presence of one or more combustible particulate solids in a process or facility. 4.2.1.1* The facility, processes, and equipment shall be designed, constructed, equipped, and maintained and management systems shall be implemented to reasonably protect occupants not in the immediate proximity of the ignition from the effects of fire for the time needed to evacuate, relocate, or take refuge. 4.2.1.2 The facility, processes, and equipment shall be designed, constructed, equipped, and maintained and management systems shall be implemented to reasonably prevent serious injury from flash fires.

Trip/Safety Hazards

From Frank Loeffler, Loeffler Engineering Group

I have become aware of at least 5 fatal accidents on rail car unloading conveyors as shown in the Figure 1. I also know of one fatality in the type of conveyor shown in the Figure 2.

What they have in common on a floor level horizontal section followed by an inclined section that uses hold down wheels to make the turn. I would like to suggest a DANGER warning label for use on this type of conveyor.

Figure 1

Figure 2

CEMA Bulk/Unit Safety Committee ANSI/ISO Pictograms

June 26, 2017

CEMA Bulk/Unit Safety Committee CEMA Safety Labels

June 26, 2017

conveyor equipment manufacturers association document is for reiew onl for the safety committee-may...

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