Analyzing the need for machine safeguarding

Analyzing the need for machine safeguarding

Assessing the degree of risk associated with a machine is a necessary first step in eliminating hazards or providing appropriate safeguards.

Assessing the degree of risk associated with a machine is a necessary first step in eliminating hazards or providing appropriate safeguards.

Typical Risk Assessment/Risk Reduction process.


Machine safeguards are designed to protect a company's most valuable asset — its employees. Using the right safeguard to reduce the risk associated with a machine hazard not only reduces both the direct and indirect costs of an accident, but also provides an opportunity to save bottom-line operating costs.

Choosing the best machine safeguard requires performing a Risk Assess-ment/Risk Reduction analysis. This helps a company determine the total cost associated with an accident and the financial and operational benefits resulting from the use of various machine safeguards. Such an analysis focuses a shop's attention on solving each machine-hazard problem.

The real cost of an accident
Typically, cost analysis of an accident is limited to total, out-of-pocket expenses associated with each specific incident, usually what an insurance company reports. Work-related accident costs go beyond hospital and medical bills and can cascade throughout a company.

Additional costs accrue not only from the loss of a worker's time because of an accident or injury, but also the time lost due to other workers involved in helping the injured person. Incidental expenses can include first-aid equipment and supplies and the cost of transporting the injured worker to a doctor's office or hospital.

Costs also include loss of production from the machine involved in the accident. And if it remains idle, production is lost on other machines that further down the line. The cost of lost production time can even extend to over-time necessary to resume production and get the plant back on schedule. In addition, it may be necessary to train a new or transferred worker to perform the work of the injured operator during his or her absence.

An accident involving improper use can, in some cases, also result in damage to the machine, meaning repair costs and additional down-time. It may also be necessary to cover the cost of a damaged workpiece, which may be considerable.

Subsequent costs
Costs resulting from an accident also include the cost of investigating the accident and complying with statutory requirements such as filling out forms for OSHA (Occupational Health and Safety Act) or preparing a state's notice of injury. In any case, a company will have to work with insurance and worker's compensation claims.

An accident can influence costs even outside the company. It could raise insurance rates and result in fines from OSHA and state regulatory agencies. Penalties from OSHA can range from nothing to as much as $70,000 per machine, if a willful violation occurs.

It is not uncommon for an analysis of all costs associated with an accident, considering its total financial impact, to reveal that the actual total cost of an accident can range from four to ten times the visible, direct cost stated by an insurance company.

The cost of an accident goes beyond strictly financial considerations. When employees are not able to work, they lose the feeling that they are an integral part of the company's success.

Analyzing machine hazards
There are two approaches to the analysis of machine safeguarding. One, referred to as the "Domino Theory," is based on the H. W. Heinrich Law which examines the relationship between unsafe acts and practices and how accidents occur.

The second approach, called the "Dupont Accident Theory," is based on the premise that all accidents are preventable through the assignment of responsibility and a measure of accountability. Both operate on the belief that the cost and losses due to accidents can be reduced to zero.

These methods are incorporated in many safety requirements aimed at reducing machine hazards, including those of OSHA, the American National Standards Institute (ANSI), and the European Machinery Directive. The development of machine safety requirements is due in part to the rise of automated machinery and the expansion of business to global markets.

A basic premise of all these safety documents is that machinery hazards be completely eliminated from the employee work zone during the machine design stage. If this is not possible, machinery safeguards must be used to provide a safe working environment.

A machine installation can include many hazard sources, including electrical, audio, ergonomic, carcinogenic, thermal, and chemical. While many types of hazards must be considered, this analysis will be limited to mechanical hazards associated with machine operation. Safeguards that prevent any part of a worker's body from entering the hazard or that point of operation can be categorized into four groups: barrier guards, devices (presence sensing or safety inter-locks), safety controls, and enclosures. Each has advantages and operating limitations.

Assessing risk
The process of developing a safety device to reduce or eliminate a hazard involves analyzing each element of machine operation. Hazards are a safety concern in areas where operators, maintenance personnel, or others must stand or pass by a machine. A machine may have one or more hazard points or areas of hazard. These include pinch points, web or roll nips, punches, shears, hot surfaces, blades, flammable vapors, and protrusions. Each hazard should be reviewed based on the function of the personnel approaching or using the machine at each location.

Generally, a risk hazard analysis starts with a list that matches each hazard to the task performed at a location. It is possible to have multiple hazards for each task and location, so a risk assessment for each hazard/location pair must be performed.

The first step in a risk analysis is to assign a risk value to each paired hazard/location as a function of three considerations: severity of a potential injury, frequency of exposure, and the probability of an accident. Each consideration is then categorized according to severity of a resulting injury, frequency of exposure, and probability of occurrence. A numerical value is then assigned to each of these categories. The following example describes the risk-analysis process.

The degree or severity of an injury can be described as minor, serious, major, and fatal. A minor injury would be a bruise, cut, or abrasion. A serious injury would result in the loss of consciousness. Major injuries are typically considered irreversible and permanent and include burns, broken bones, loss of sight or a limb, or some other permanent bodily damage. A fatal injury is the most serious situation.

A numerical value is assigned to each category: 1 for a minor injury, 3 for a serious injury, 6 for a major injury, and 10 for a fatality.

Frequency of exposure to a hazard can be described as frequent (several times a day or more), occasional (daily), and seldom (once a week or less), with assigned values of 4, 2, and 1, respectively.

Probability of occurrence of an accident can be described as unlikely, possible, probable, and certain with respective values assigned of 1, 2, 4 and 6.

In this example, the maximum total risk for all three categories is 20 and corresponds to the most serious condition. If a risk was estimated to have a cumulative total of 13, it might be considered a medium risk.

Additional tasks associated with a particular hazard are similarly analyzed and assigned total-risk numbers. The total-risk summation of all tasks considered for this particular hazard is used as an initial-risk value in an iterative risk-reduction process, which is then run for each remaining category. This lets users develop a structure to identify hazards with relative weighting and experiment with various remedies and machine guarding equipment.

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