Safeguards, Safeguarding, including physical guards, light curtains,
dual operating buttons, safety instrumentation, etc.
● other names for safeguards include machine guards, guards, etc.
Safeguarding and Safeguards in design are based on the knowledge from Human Factors and are an integral part of Safety Design. There is a long history of use of safeguards, and many safeguards that are routinely used have a proven effective history in use in various particular circumstances. Safeguards are enshrined in many generally accepted Codes, Standards and Recommended Practices.
- physical guards or barrier guards which literally prevent access to the hazard, at least during operations, often accompanied by safety instrumentation to sense the unauthorized disabling of the guard, and to stop or alter the operation to prevent access to the hazard, usually disruptively to the operation
- physical guards coupled with safety instrumentation for operations whose physical guards are intended to be circumvented at will, but preferably infrequently, during operation to alter or stop the equipment operation to eliminate the hazard when the physical guard is circumvented, such as a door to the hazard that can be opened at will while the equipment is operating - such an arrangement is often at least somewhat disruptive to operations when the safety instrumentation alters or stops the operation of the equipment, so its use is usually discouraged
- safety instrumentation which prevents access to the hazard when it is a hazard
- safeguarding devices that allow access to the normally hazardous area, and simultaneously prevent the hazard from being effective as a hazard to the operator and others with access at that time - such devices are usually closely integrated into the equipment operation and are not disruptive, or minimally disruptive, to the planned operations. although they may have a major impact on productions rates
Physical guards, barrier guards, are often effectively fencing or grating. They are commonly used to prevent access to hazards which require no access for operation of the equipment. They are often accompanied by safety instrumentation that will stop operations if the barrier guard is removed or altered enough to expose the hazard. This alteration or removal is not intended to be a part of normal operations, even occasionally.
- in running nip points associated with such items as meshing gears, belts and chains on sprockets
- rotating components such as flywheels, gears and shafts
- pinch points between moving and stationary components of machinery
Some Safeguarding Devices are very effective for the special problem of the point-of-operation. The point-of-operation is the location where items are being processed and worked. These safeguarding devices may allow access to a normally hazardous area, only when the area is not hazardous, or may prevent the hazard from being effective as a hazard to the operator and others when access is allowed, or may allow an operator to get close to a hazardous area without contacting the hazardous area, without using a barrier guard.
● Safeguards can be considered to consist of the following types:
Safety instrumentation which prevents access to the hazard when it is a hazard is most often used in conjunction with equipment that has varying times during its use when it would be hazardous to a user, and other times when its use would not be hazardous to a user. An example of that would be the doors to an elevator shaft. When the elevator occupant cage is properly located at the floor, opening the door and stepping through the doorway into the elevator shaft is safe. When the elevator occupant cage is located at a considerable distance from the floor, opening and stepping through the door would be very hazardous. When the elevator occupant cage is located several inches above or below the floor, opening and stepping through the door could lead to a serious fall. Such instrumentation to be true safety instrumentation must be fail-safe, which means that if there is a failure in the instrumentation, the equipment will be rendered safe, even at the cost of being non-operational, if that is the safe condition. In the case of the example elevator, the doors would not automatically open for users until the failure in the safety instrumentation was repaired.
● Safeguards can be considered to cover at least the following issues:
- the point-of-operation for industrial equipment, commercial equipment and consumer products, such as the point of operation between the dies in a stamping press, where the metal part is stamped into a shape, under conditions where the metal part must be inserted in between the dies repetitively by an operator during the operation
- non-point-of-operation hazards for industrial equipment, commercial equipment and consumer products such as moving chains on sprockets (an example of an in-running nip point)
- intermittent hazards to users particularly for equipment passively used by the public, such as the doors on an elevator, where the location of the passenger cage (the elevator) determines whether it is safe for the doors to the elevator shaft to open
Safeguards and Safeguarding, characterized by issues
Physical Guards, Barrier Guards
Physical Guards, Barrier Guards,
coupled with safety instrumentation for operations
Physical guards coupled with safety instrumentation for operations whose physical guards are intended to be circumvented at will, but preferably infrequently, can be used where operating problems may require that the operation be altered to resolve the operating problem, and part of that alteration involves accessing equipment locations which are hazardous in normal operation.
Safety instrumentation which prevents access to the hazard
Safeguarding Devices, especially for use at and near the point-of-operation
- presence sensing devices, such as light curtains associated with such equipment as automated presses, and presses operated by the operator with a foot pedal, a single hand button, or any other device that leaves his hand or hands free to go into the point-of-operation when they could be injured - these devices stop movement or take whatever action is necessary to protect from the hazard when they are interrupted by a body part
- dual operating buttons, such as dual palm buttons, useful wherever the operator alternates between accessing the point-of-operation, such as inserting a part between dies, and then must operate the next cycle of the equipment, usually creating a hazard to the operators hand(s) or other body parts during this cycle - the location of the dual operating buttons must be such that these body parts cannot be contacted by the hazard while the dual operating buttons are being actuated
- pullbacks which literally will pull an operators hands and/or arms from the area of danger at the time that the hazard exists - these devices must be put on by the operator and properly adjusted to be effective
- restraints which prevents a body part of the operator from entering the hazardous area, useful when the operator must get close to the point-of-operation during the operation, but does not have to get into the hazardous area of the point of operation, but cannot be isolated from the point of operation by a barrier guard - these devices must be put on by the operator and properly adjusted to be effective
- an automatically controlled moving barrier(s) which can be used when certain physical areas are hazardous at certain times, and not at other times. and which allows access to the normally hazardous area only when it is not hazardous to the operator
Safeguarding and Safeguards are based on knowledge from Human Factors and are a
Safeguards and Safeguarding, characterized by types
The choice of safeguards as the design solution to safety hazards is based on the principles of the Safety Design and particularly the Safety Design Hierarchy, which is the accepted system for design of safe equipment, systems, products and facilities. The Safety Design Hierarchy requires that safety hazards be designed out of the equipment, products and facilities wherever and whenever possible. Only if the hazards cannot be designed out, are safeguards used to protect against the hazards. The Safety Design Hierarchy also requires that Warnings not be used in place of Safeguards if Safeguards will protect against the hazard. If Safeguards will protect against the hazards, Warnings are used to complement safeguards when this adds to the safety of the installation where safeguards are being used to protect from hazards. Safeguards and Warnings are not interchangeable.
The information that follows is not intended to be exhaustive, Safeguarding is a large issue with many publications covering various aspects of the subject. The coverage below is intended to introduce the subject. The organization of the materials below is one way to look at the subject. The choice to use Safeguards, and the specifics of any particular Safeguard requires engineering analysis of many factors in the areas of Engineering Design, Human Factors and Safety Design.
For more information see >>
as a forensic engineer for over 30 years, routinely analyze Safeguards (physical guards, light curtains, dual operating buttons, safety instrumentation, etc.) and Warnings, and the requirements for Safeguards and Warnings, often analyzing to determine whether there is a need for Safeguards and/or Warnings, and to determine whether Safeguards and/or Warnings which are present met the needs for safety, and are the correct choice for safety.
Relationship of Safeguards and Safeguarding
to Human Factors, Safety Design, Warnings, and Codes and Standards
as part of the Bachelors and Masters degrees in Engineering, he took extensive coursework in Engineering
he minored in Normal Psychology as part of the Bachelors degree work
Combined, Engineering and Normal Psychology are the scientific bases of Human Factors and the related studies of the human-machine interface, human-facility interface, and responses to hazards, which comprise a significant part of the foundation for Safety Design and Safety Design Analysis. Human Factors and Safety Design are the bases for the requirements for Safeguards as well as Warnings. James D. Madden, P.E. has specific education in Engineering and Normal Psychology, as follows:
during 17 years in industrial operations and engineering design specified Safeguards and Warnings as part of the engineering design of equipment, systems and facilities, with analysis of Safeguards and Warnings as part of safety assurance
during 17 years working in industrial operations and design engineering, made extensive use of Human Factors and Safety Design, the bases for Safeguards and Safeguarding, as an integral part of engineering design, including acquiring personal knowledge of the human-machine and human-facility interfaces while working in industrial operations
as a forensic engineer for over 30 years, routinely use Human Factors and Safety Design principles, the bases for Safeguards, in engineering analysis of accidents, and equipment and facilities involved in accidents
during 17 years as a design engineer and for over 30 years in forensic engineering, have made extensive use of Codes and Standards and Recommended Practices, including interpretation, inclusive of requirements for Safeguards and Warnings
requirement in Safety Design. Safeguards are included in many generally accepted Codes, Standards and Recommended Practices. Warnings and Safeguards are used in prescribed manners related to the safety of the use of one or the other in particular circumstances. These subject areas are all closely related.
A door to such a hazardous location is an example of this type of safeguard. This door could be for access by a hand, such as on some lathes, or a whole person, such as with some plastics processing equipment. Safety instrumentation associated with physical guards coupled with safety instrumentation for operations is designed to be the least disruptive to the operations as is feasible, while still safe, as opposed to safety instrumentation associated with physical guards to prevent persons disabling the guards and continuing operation with the hazard exposed. Such instrumentation to prevent disabling the guards can be very disruptive to operations.
Often the operator or others must access the point-of-operation during operations. In some operations the operator may be required to access the point-of-operation repetitively many times an hour, perhaps every few seconds, even placing his hand repetitively between dies in a stamping press, for example. These safeguarding devices are intended to eliminate the hazard passively when the operator enters the point of operation (for example, with his hand), or to prevent the operator from accessing the point of operation when it is a hazard, without using a barrier guard.
Examples of safeguarding devices that allow access to a normally hazardous area only when it is not in a hazardous condition, or create the non-hazardous condition during access, which are especially useful at the point-of-operation, include:
Examples of hazards that may be effectively protected against by physical guards, barrier guards, usually without operational effects, include:
Experience and Qualifications of James D. Madden, P.E.
in regard to Safeguards and Guards, and application of Safeguarding
earned the Professional Engineers license (P.E.) by taking the National Council of Engineering Examiners' examination in Fundamentals of Engineering and the Mechanical Engineering and Chemical Engineering sections of the National Council of Engineering Examiners' (NCEE) examination in Principles and Practices of Engineering
earned 2 Engineering degrees, Bachelor of Science and Master of Engineering, and took additional credit coursework post-degree, taking coursework in physics, chemistry, mathematics, engineering mechanics, mechanical engineering, chemical engineering and normal psychology
at the start of forensic work, completed refresher and additional post-degree college credit coursework and continuing education coursework in mechanical engineering, metallurgy and materials
designated a Diplomate Forensic Engineer by the National Academy of Forensic Engineers in accordance with the standards of the Council of Engineering and Scientific Specialty Boards (CESB)
● attended engineering seminars presented by the National Academy of Forensic Engineers
regularly attend additional technical courses and seminars each year to meet the requirements for continuing engineering education for the Professional Engineer's license
● over 40 years of engineering experience, with:
● 17 years experience in industrial operations, engineering design and construction assistance
● 30 years experience in forensic engineering, including:
● working on over 1000 cases
● issuing over 600 reports and over 60 affidavits
● testifying in over 90 depositions and over 75 trials
Our Work with Safeguarding in Our Forensic Engineering Work
In our Forensic Engineering work, Safeguards, including physical guards, mechanical interlocks, light curtains, dual operating buttons, instrumentation, etc., are routinely analyzed, particularly relative to Warnings, whether present or not. Safeguards and Warnings are closely related, but generally used for different conditions. The safety requirements for Safeguards and/or Warnings are used to determine whether there is a need for Safeguards and/or Warnings, and to determine whether Safeguards and/or Warnings, if present, meet the needs for safety. If a requirement for Safeguarding or Warnings is determined to exist, the analysis includes determining whether either Safeguards or Warnings are the correct choice for safety, or if both should be provided.
Our work with Safeguarding includes engineering analysis to determine the adequacy of the Safeguarding used in industrial and commercial operations and construction activities, and the adequacy of Safeguards used as components of industrial and commercial equipment and consumer products. The purpose of this work is to determine whether these Safeguards were installed and used in a manner that would assure the safety of these activities and items. The purpose of this work is also to determine whether the Safeguards were chosen as required by the Safety Design Hierarchy, and whether the Safeguards, and their use, met the requirements of Codes, Standards and Recommended Practices.
Safeguards include physical guards (barriers of various types), light curtains, dual operating buttons, interlocks and safety instrumentation, restraints, and similar items and devices. Safeguards are provided specifically to prevent persons from encountering a hazard.
Residential, commercial, industrial, manufacturing and construction equipment, and components associated with this equipment, and associated facilities, are analyzed for the need and correct application of Safeguards. This analysis includes consideration of the role that Warnings might also serve for the installations analyzed.
Consumer products and residential, commercial and industrial facilities, considered separately from equipment, are also analyzed for the need and correct application of Safeguards. This analysis includes consideration of the role that Warnings might also serve for the installations analyzed.
click for discussion of many of the considerations for the engineering analysis of Safeguards and for their need and use with equipment, products and facilities
<< click for a description of the typical activities and work performed
■ including ● mechanical interlocks ● physical guards, such as barriers and various types of restraints ● electronic safeguards, such as light curtains, control interlocks, double actuation buttons and fail-safe instrumentation ■ safeguards for use on or with ● consumer products
● equipment ● machinery ● roadways ● buildings ● structures ● etc.
Madden Accident Analysis & Forensic Engineering, through its Senior Forensic Engineer, James D. Madden, P.E., a licensed professional engineer, has performed Accident Investigations, Engineering Analyses and Accident Reconstructions for accidents, incidents and cases in the metropolitan areas of Cleveland, Akron, Canton, Toledo, Warren, Youngstown, Mansfield, Columbus, Dayton, Cincinnati, Lima, Findlay, Marietta and Steubenville, as well elsewhere throughout Ohio, and the metropolitan areas of Pittsburgh and Erie, as well as elsewhere throughout western and central Pennsylvania, and the metropolitan areas of Detroit, Ann Arbor, Lansing, Flint and Port Huron, as well as elsewhere in southern Michigan, and the metropolitan areas of Buffalo and Syracuse, as well as elsewhere in western and central New York state. In many of these areas James D. Madden, P.E. has provided expert reports and testified in the capacity of an Expert Witness in court proceedings, including depositions, arbitrations and/or trials.
Madden Accident Analysis & Forensic Engineering, through its Senior Forensic Engineer James D. Madden, P.E., is available for Accident Investigations, Engineering Analyses, Accident Reconstructions, and testimony in deposition, arbitration and trial, for cases located throughout North America.
Consultation is available before starting a case. We invite you to
consult with us. There is no charge for an initial phone consultation.
Call us, or if you prefer we can schedule the consultation in advance.
Consultation with James D. Madden, PE, a Professional Engineer, and Forensic
Engineering Consulting and Testifying Expert Witness, is available to the client at all
times during the work - before, during, and after the investigation,
engineering analysis, reconstruction, report, and any other work on the case.
Download a Summary or Detailed Curriculum Vitae (CV) / Resume' for James D. Madden, P.E.,
email us, and bookmark this website.
Qualifications of James D. Madden, P.E., Senior Forensic Engineer
Downloads and Links - Curriculum Vitae, Email and Bookmark
For mailing address, phone, fax and email address click a button below the Fee Schedule section.
Contact us by phone, fax, mail or email for a copy of the Fee Schedule for charges for engineering
and consulting services and testimony. Click a button below for contact information.
Over the last 30 years we have regularly worked on accidents which occurred in Ohio, Pennsylvania, Michigan, New York and nearby, including inspections of accident sites, equipment, and facilities, with reports and testimony. During these 30 years we have also worked on accidents which occurred in other states, and equipment and facilities located in other states, with inspections of accident sites, equipment, and facilities, from Utah and Kansas to Vermont and North Carolina, with reports and testimony for these accidents, when applicable.
Geographic Area of Practice - North America
Contact us to discuss your case by phone at NO CHARGE.
This consultation can be scheduled in advance to meet your schedule.
● verbal reports, by telephone or in face-to-face conferences
We present the results of our investigations, engineering analyses and reconstructions in
the client's choice of any, or all, of the following:
Presentation of results of our work
Our work investigating, analyzing and reconstructing accidents, and presenting the results, may include any
or all of the following, depending on the needs of the case:
Our Typical Work Activities and Products, when warranted by the case
● written reports and affidavits
● deposition testimony, including video deposition
● trial testimony and arbitration testimony
James D. Madden, P.E., while performing Forensic Engineering work full-time for over
the last 30 years, for both plaintiff and defendant, has to date:
Forensic Engineering Work by Senior Forensic Engineer James D. Madden, P.E.
● completed over 1000 cases
● written and issued over 600 reports
● testified in over 90 depositions
● written and issued over 60 affidavits
● testified in over 75 trials
See details of the forensic work throughout this website, and a summary on the Employment Page.
The qualifications of James D. Madden, P.E., Senior Forensic Engineer, Consulting and Testifying
Use the Search Box at the left to search the whole website.
Use Control F, 'Ctrl' + 'F', to locate specific words on this page.
Bookmark this site by typing Control D ('Ctr' + 'D').
Safeguarding, Machine Guards - Table of Contents - links to content on this page
■ Our Work with Safeguarding, and its involvement in Our Forensic Engineering Work ■ Our Forensic Engineering Work - number of ● Cases ● Reports ● Affidavits ● Testimonies ■ Safeguarding characterized by Issues ■ Safeguarding characterized by Type ■ Experience & Qualifications ■ Our Typical Work Activities & Products ■ Presentation of Results of Work ■ Geographic Area available for Work
click on the underlined squares to link to the subjects
■ Relationship of Safeguarding with Human Factors, Safety Design, Warnings and Codes & Standards ■ Barrier Guards with Instrumentation ■ Safeguarding and Instrumentation ■ Safeguarding and Point of Operation ■ Contact Us by Phone, Mail or Email ■ Consult, before and after assignment ■ Fee Schedule availability ■ Curriculum Vitae and additional Qualifications ■ Links to Other Pages (left sidebars)
● inspection of the accident site, such as a roadway, outdoor facilities, building or industrial facilities
inspection of the involved equipment, in current condition, including in damaged condition (such as crashed vehicles); and when available for operation, during operation (such as industrial equipment)
● interviewing witnesses (often during the inspection of the accident site, product and/or equipment)
coordinating or interfacing with others while they are preparing specialized exhibits such as video animations and videos of demonstrations
review and study of case documents, evidence and applicable codes, standards, regulations and recommended practices
● written reports and affidavits, and exhibits
drawings, calculations, graphical analyses, computer analyses, etc. as required to analyze and reconstruct the accident, and to present the engineering analysis and reconstruction
● testing accident items and exemplar items (such as consumer products)
● photography and/or video of the accident site and involved equipment
● testimony in deposition, trial and arbitration
for more information,
click on subject listings below
Related Basic Specialties
These Specialties are in a website which will open in a separate tab to the right of the current tab. This website in the current tab and the new website will be available side by side.
If lines of text overlap in this website check the browser zoom setting - reducing the zoom should prevent overlap of lines of text.
If parts of the website are missing or distorted, such as a section of the Left Navigation Bar, or a button, try rebooting the page in the browser, one or more times - click on the circle arrow at the left of the website name [URL].
brown buttons below open pdfs in separate tabs for downloading
Madden Accident Analysis & Forensic Engineering
over 30 Years Investigating, Analyzing, Reconstructing & Testifying about Accidents
Forensic Engineering & Scientific Accident Reconstruction
Copyright 2011, 2012, 2015, 2016, 2018, 2019 by Madden Accident Analysis & Forensic Engineering and James D. Madden, P.E., aka James Madden and Jim Madden.
All rights reserved. This website contains photographs which are licensed with restrictions that prohibit downloading, reproduction, re-publication or re-transmission.
Madden Accident Analysis & Forensic Engineering, through its Senior Forensic Engineer, James D. Madden, P.E., a licensed professional engineer, has performed Accident Investigations, Engineering Analyses and Accident Reconstructions routinely for accidents, incidents and cases located in Ohio, Pennsylvania, Michigan, and New York, in the technical areas which are noted in this website, as well as providing expert reports and testifying in court proceedings in these states in the capacity of an Expert Witness, including depositions, arbitrations and/or trials, with Forensic Engineering work also performed in, and/or for cases in, Illinois, Maryland, North Carolina, Vermont, Kansas and Utah, with testimony in court in Kansas.
Madden Accident Analysis & Forensic Engineering
1700 West Market Street, Suite 318, Akron, Ohio 44313, or
8803 Brecksville Road, Suite 7-216, Cleveland, Ohio 44141
phone: 440-838-1191 or 440-832-9540, fax: 440-838-1192