by Mark Webster MSME, PE
Beginning with the 2015 edition of the AMSE B20.1 ASME Safety Standards for Conveyors and Related Equipment, a paragraph has been added addressing the need for a formal risk assessment for conveyors and conveyor systems. This article explains the need for risk assessment for conveyors, what the standard recommends, references to available documentation of risk the assessment processes, and some examples of product liability/injury cases involving conveyors where risk assessment was a factor.
The use of conveyors has greatly reduced the number of accidents that occur due to manual handling of materials. However, conveyors can present hazards to personnel working in the vicinity that must be addressed during design, installation, use, and maintenance. Part of the process engineers use when designing any machine is performing an evaluation of the design to identify potential hazards to personnel in the vicinity, such as operators, maintenance personnel, or just passersby. This is one reason B20.1 recommends that the design and installation of conveyors and conveyor systems be supervised by qualified engineers.1
During the design process, engineers identify potential hazards and try to either design out the hazard or otherwise protect personnel from contact with the hazard through the use of guards or other measures. A widely accepted system for identifying, mitigating, and documenting this evaluation process is the Risk Assessment Process. This is a formalized process that documents the hazards that were identified and what provisions were made to mitigate the risk to an acceptable level. Risk assessments have fairly recently gained popularity in mainstream industry in the U.S., in part due to the increasing popularity of performance based standards and from an increased focus on safety. It is now quite common for the subject of risk assessment to come up during litigation concerning injuries sustained through contact with a conveyor.
This article does not delve into the details of how to perform a risk assessment. Instead the reader is directed to use any of the many available risk assessment standards including those referenced in ASME B20.1 and in the endnotes of this article.2
Safety standards come in two types: prescriptive and performance based. Prescriptive standards describe specifically how requirements are to be met. For instance, let's consider the fictitious prescriptive requirement for guarding an in-running nip point hazard on a conveyor indicating "an individual physical guard shall be installed at all nip points." The advantage of this prescriptive requirement is that everyone knows what the requirement is and it can be easily be verified; there must be a guard in place on every nip point on the conveyor. The risk assessment has essentially already been completed by the standard writer. With a prescriptive standard, the engineer simply follows the instructions, like a recipe, when designing.
However, prescriptive standards tend to impede product improvement since they do not leave the engineer any leeway for alternate designs that may be just as good or better. For instance, in the nip point example above, what if a fence is provided around the entire conveyor preventing access by personnel? Or how about if the nip point is guarded by location (out of reach)? Or what about providing a system of sensors that detect personnel in the vicinity and shut down the conveyor? If these methods of protection are not specifically allowed in the prescriptive standard they cannot be used.
Performance based standards, on the other hand, describe what end result should be achieved, but not specifically how to achieve it. For the above example, a performance based standard might read "Nip points shall be guarded." Big difference. Based on the definition of "guarded" in the B20.1 standard, for instance, any method of protection that results in personnel not being exposed to the nip hazard is acceptable, not just a physical guard.
This is what makes performance based standards valuable — they allow engineers to improve designs and utilize newly developed technology and still meet the performance requirements of the standard. This is also why performance based standards and risk assessments go hand in hand. To use a new design or new technology, a risk assessment is required to ensure that the final design meets the performance requirements of the standard. OSHA favors performance based standards and has requested that standard development organizations such as ASME use them when possible.
The ASME/ANSI B20.1 Safety Standard for Conveyors and Related Equipment, first issued in 1947, was developed to provide guidelines for the design, construction, installation, operation, and maintenance of conveyors and related equipment. In 1973 OSHA indicated an interest in B20.1, and the standard underwent a change in format to a performance standard, which is preferred by OSHA. B20.1 is the definitive safety standard for conveyors in the United States and is incorporated by reference into OSHA CFR 1910 and CFR 1926. Over the years engineers have relied on the B20.1 standard to guide them in the process of designing conveyors and conveyor systems. Since B20.1 is a performance based standard, a necessary part of the design process is performing a risk assessment, although the standard contained no direct reference to risk assessment until the 2015 edition.
The B20.1 standard has two major sections. Section 5 contains general guidelines for all conveyors and Section 6 contains guidelines for specific types of conveyors. However, there are hundreds of different variations of conveyors, and new designs continue to be developed. The B20.1 standard does not attempt to cover every possible variation of conveyor and the unique hazards they may present. Again, since it is written as a performance standard, it can be applied to any new design or new technology as long as a risk assessment is performed to ensure that the performance requirements of the standard have been met. This is important for products such as conveyors that are constantly being upgraded with new technology, customized to meet an end user's specific needs, and with new types of conveyors popping up often.
One caveat with performance based standards is the very same characteristic that makes them advantageous: flexibility. The flexibility of the performance based requirements can make it difficult to determine if the requirements have been met. In the above example, how do you know if the safety features provided meet the performance requirement of the standard? This is where the risk assessment comes into play.
In the case of a performance standard, it is the responsibility of the engineer to use his experience and expertise to determine how to best meet the performance requirements of the standard. This is best accomplished by using a formal risk assessment process to systematically evaluate the conveyor or other machine to identify hazards and the risk associated with them, and to document what was done to mitigate the risk to an acceptable level.
The ASME B20.1-2015 standard recognizes this need by including section 5.16, which recommends the use of a formal risk assessment process for all conveyors. B20.1 does not specify a particular risk assessment procedure to follow, and the specific standard used is not important. The standard does however offer some examples of documented risk assessment processes. In particular, it is suggested that the reader refer to the CEMA Technical Report 2015-01 "Recommended CEMA Risk Assessment Process." This relatively new risk assessment process is the only one in existence that I am aware of that is tailored specifically to the conveyor industry, and includes lists of common hazards and hazardous situations typically found on conveyors.
The B20.1 standard should be referenced during the risk assessment of new conveyors and conveyor systems. Paragraph 5.16 states "This standard should be used in the risk assessment process and has evolved from assessment of the hazards and risks associated with conveyors. This Standard also identifies appropriate safeguards to reduce the danger to an acceptable level."3 In other words, the standard supplies the performance requirements, and the risk assessment process is used to evaluate various methods of accomplishing the required performance.
The standard also recognizes the burden that the risk assessment process could place on some manufacturers of standard lines of conveyors, who may ship hundreds of individual conveyors in a matter of days, and indicates that "Companies that produce standard products/equipment may conduct a risk assessment analysis for a product group in lieu of each individual standard product shipped out of that product group."4 If, however, the conveyors designs are modified in a way or are a component of a larger overall system, a new risk assessment should be performed to determine if any new hazards may have been created.
Summarizing the risk assessment recommendations in ASME B20.1:
As far as OSHA is concerned, the responsibility to provide a safe workplace is that of the employer. In general OSHA requires that a Job Hazard Analysis be completed to evaluate the processes that employees follow, and to provide safeguards to protect them from these hazards. Employers utilizing conveyors or conveyor systems in their operations must be aware of the hazards posed to employees and protect them, and in many cases it is very helpful to get assistance from manufacturers or other conveyor experts. In addition B20.1 requires that only trained personnel are allowed to operate conveyors, and maintenance must be performed by qualified and trained personnel.
In general, risk assessment is a shared responsibility between the various parties involved. Typically this includes the manufacturer, installer, end user or owner, and often the system integrator that designed the overall conveyor system.
In the case where sections of "standard" conveyor are being used in some sort of process, the manufacturer is often only responsible to provide a conveyor that meets the guarding and warning requirements of B20.1 for that specific type of conveyor, preferably by performing a standard risk assessment for the particular line of conveyor. The manufacturer may not know the exact end use of the conveyor or be involved in the design of the overall conveyor system, and would not be able to perform a risk assessment for the entire system on their own.
The manufacturer is responsible for performing a risk assessment of the individual conveyor sections. If any modifications are made to the standard design for a particular application, the manufacturer should review the standard risk assessment and revise it to include any new hazards that may have been created as a result of the changes. If an installer, owner, or any other entity modifies the conveyor after it is shipped from the manufacturer, they may take over the responsibility. ANSI+B11+TR3-20005 states that "When the user designs, constructs, modifies or reconstructs the machine, the user is considered to be the supplier."
The system integrator is generally responsible for performing a risk assessment of the entire conveyor system. This could be the conveyor manufacturer, a third party company, or the end user themselves. Sometimes this responsibility is divided between two or more separate entities that may be performing a part of the integration. For instance, the integration may be divided between mechanical and electrical integration.
A maintenance worker at a recycling facility sustained severe injuries to his hand when it was pulled into a chain drive on a conveyor. The worker was applying oil to the chain, and had not locked out the controls. Another worker started the conveyor, unaware that the other worker was oiling the chain, pulling the worker's hand into the chain drive.
The conveyor was a component in a shredding system, which also included the shredding machine and electrical controls. Material exiting from the shredder in one room was deposited on an inclined steel belt conveyor. The material was conveyed from the shredding room upward at an angle to an adjacent room through a hole near the top of the wall separating the two rooms, where it was deposited into a cart for transporting to the next stage in the process.
There was an issue with improper lock out/tag out. The plaintiff also argued that the manufacturer of the conveyor had failed to provide proper controls including an audible warning prior to the conveyor starting as well as e-stop devices.
The conveyor manufacturer had supplied this conveyor as an individual component to be used in the overall system, and had no involvement in the design of the control system or the overall system layout. The layout of the system was a joint effort between the end user and the system integrator that they hired to install all of the various components and configure the controls to provide the desired operation. The manufacturer of the conveyor was not consulted during this process. As such, the risk assessment responsibility of the manufacturer was for the most part limited to ensuring the conveyor met the applicable requirements of the B20.1 standard for this particular type of conveyor, and assisting with the risk assessment of the overall system if so requested by the end user.
My opinion was that the conveyor as supplied by the manufacturer met all applicable requirements of B20.1, and the responsibility for performing a risk assessment on the overall system was shared between the system integrator and the end user. This would include identifying any safety features that needed to be added in addition to what the conveyor manufacturer supplied on the standard belt conveyor. It is the end user's responsibility to work with the system integrator to develop safe processes for operators and maintenance personnel. It is the system integrator's responsibility to ensure that the overall system design meets the B20.1 and any other applicable standards, in light of these processes.
This case settled without going to trial.
An employee of the Street Department was helping load road salt into a storage building, utilizing a stacker conveyor, when the hood on his sweatshirt was snagged by an exposed rotating shaft. The worker was spun around and eventually thrown to the ground, sustaining severe injuries.
A stacker conveyor is a portable or movable inclined belt conveyor, generally used for creating piles of bulk material. In this case it was used in the summer or fall months to stockpile salt for use on icy roads during the upcoming winter. Stacker conveyors can be powered in various ways, including from a tractor power takeoff (PTO) shaft, as it was in this case. Salt flowed from a dump truck into a hopper at the lower end of the conveyor, and was conveyed upward at an angle and discharged to make a pile. Some salt tends to spill out onto the ground at the infeed hopper end and occasionally needs to be manually shoveled back into the conveyor infeed hopper. This is what the worker was doing when the hood of his sweatshirt was snagged by the exposed rotating shaft. During discovery it was found that this shaft was supplied by the conveyor manufacturer and was not guarded.
The B20.1 standard states that "Where necessary for the protection of personnel from hazards, all exposed moving machinery parts that present a hazard to personnel at workstations or operators' stations shall be mechanically or electrically guarded or guarded by location or position." The B20.1 also encourages the reader to use the ANSI B15.1-2000 (R2008) Safety Standard for Mechanical Power Transmission Apparatus, which includes guarding of rotating drive components.
Rotating shafts present a serious safety hazard and must be guarded. In this case, the conveyor was not modified by the end user, and was being used as intended by the manufacturer. Although the employer has the ultimate responsibility for providing a safe workplace, they also expect that a standard product has been designed to meet the applicable safety standards.
One of my opinions in this case was that since there was no system integrator, and the conveyor manufacturer supplied a standalone conveyor of a standard design, and the conveyor was not modified by the end user, they had the sole responsibility to perform a risk assessment of the design. Such a risk assessment should have identified the safety hazard presented by the exposed rotating shaft and prompted action such as fitting a guard over the shaft or removing the extended shaft, which served no purpose.
This case settled without going to trial.
Mark R. Webster is a mechanical engineer who specializes in conveyors and is an experienced expert witness. He is a licensed Professional Engineer with 35 years of experience with conveyors, and a wide range of industrial machinery and control systems, conveyor systems, material handling systems, elevators, material lifts, vertical conveyors, and custom engineered machinery and systems. Mr. Webster is a Board Certified Forensic Engineer, Vice Chair of ASME B20.1 Safety Standards for Conveyors and Related Equipment, Chair of ASME Board on Safety Codes and Standards, and a member of the National Academy of Forensic Engineers. Mr. Webster can be reached at 262-707-2159 or by email at:
1 See ASME B20.1-2015 Introduction
2 Risk assessment examples are listed in ASME B20.1-2015, paragraph 5.16
3 ASME B20.1-2015, paragraph 5.16(b)
4 ASME B20.1-2015, paragraph 5.16(c)
5 American National Standards Institute, ANSI+B11+TR3-2000, Safety Standards for Mechanical Power Transmission Apparatus