Operator error is usually only a “symptom” of the cause of crane accidents
Mobile cranes are potentially dangerous and in most cases harbor higher accident potential than any other equipment in construction and industry.
“There is still no other piece of equipment that has the potential of causing so much damage or harming so many people as does a crane in an accident,” Donald Dickie, internationally known crane expert, said. For example:
• Cranes are involved in more serious accidents than other construction equipment. • Crane accidents cost most in insurance claims. • More construction fatalities result from cranes and hoisting equipment than any other cause.
Force Dangers
To comprehend this better, it is important to understand why such potential danger exists. Mobile cranes are capable of producing tremendous amounts of force. This force is created by crane functions such as hoisting, booming and swinging. The velocity at which these functions occur determines the amount of force exerted.
The important thing to remember, however, is that force has virtually the same effect on a crane and its components as does load weight. For example, if a load were lifted or swung fast enough, the force created from these movements could be enough to exceed the crane’s ratings and result in a turnover or structural damage.
The problem does not occur from moving loads—that is the purpose of the crane—but instead when the force from these movements exceeds the crane’s capacity.
It is essential, therefore, that force be kept within manufacturer’s parameters and guidelines.
How is this done? Normally it is left up to the operator’s perception and judgment. This is one of the many reasons why he plays such an important role in crane safety.
Change Factors
Because mobile cranes are so versatile and mobile, they are constantly in the process of change. Amplified by the many configurations that mobile cranes can undergo, this produces a multitude of variables necessary to ensure safe operation. When these variables combine with human factors, predicting accidents is difficult.
To illustrate this, consider a hydraulic crane prepared to lift a 10,000-pound load with 60 feet of boom at a 30-foot radius. According to the manufacturer’s load chart, this lift is possible since the load to be lifted is within the crane’s maximum rated capacity of 11,600 pounds.
But there are many other things that must be taken into consideration. For example, there is the lattice extension and jib attached to the main boom, the headache ball, the load block and rigging—all of which when combined add several thousand pounds to actual load weight and must be considered before the lift is attempted.
A failure to do so would result in an overload condition and possibly an accident.
Other questions also must be asked: Are there adequate parts of line? Does the list require that outriggers be fully extended? Which capacity chart is to be used? When placing the load will the radius be reduced and how much? In which “quadrant” is the load to be lifted? When the load is swung will it be to an area of less capacity?
Sound Evaluation
In addition, there are other factors that come into play, such as wind, terrain and crane set-up on different surfaces. These are only a few of the many variables that can be created through the configuration and operation of mobile cranes—each one of which often required precise calculations and sound judgment.
Mobile cranes today differ somewhat from the past. Industry demands and increased technology have resulted in crane manufacturers building sophisticated “state-of-the-art” machines specifically designed to maximize capability.
Pound-for-pound, mobile cranes have more capacity. In the past, for a mobile crane to life 100 tons, its actual weight would have to exceed this capability. It is possible today, however, to purchase cranes having twice the capacity for their total weight. For the consumer, this translates into the crane being smaller, lighter and more manueverable and cost-effective.
Stability Problems
However, these changes have resulted in the crane’s capacities being based more on structural competence rather than stability. The crane could break before it tips—so the raising of outriggers should never be relied upon to indicate an overload. Even though this has never been advised as an alternative to precise load chart interpretations, older cranes do have a tendency to be more forgiving since their capacities are derived more from tipping weight.
This can be illustrated by a conversation I had recently with a plant manager interested in acquiring some training. During our conversation he said his company owned an older lattice-boom crane, but last year had purchased a rough-terrain, hydraulic crane. Even though they had experienced several minor accidents with the older crane, it was not until they acquired the hydraulic crane that the more serious accidents began. In fact, during the course of a year they had buckled two booms resulting in $60,000 damage and turned the crane over twice. Why did this happen? Primarily because those involved with the crane failed to perform the necessary pre-lift calculations and comply with the manufacturer’s instructions and warnings.
Misperceptions
For the benefit of the safety professional, our failure to understand why mobile cranes are so potentially dangerous has not been the only oversight, but rather has led to a more serious problem: the way the crane is viewed.
This inaccurate perception has been perpetuated by the emergence of hydraulic cranes and the erroneous idea that their operation requires little skill.
Instead of viewing the crane as a complicated and sophisticated machine, it has been viewed as a “tool” to be operated by virtually anyone. Because of this, industry is continuing to pay a tremendous price in terms of accidents.
This information does provide a clue as to why most crane accidents occur and where prevention should begin. Mobile cranes do inherently entail a high degree of danger, but this danger does not exist within the crane itself, as some have mistakenly thought. The problem begins when the crane is put into operation.
It is also interesting to note that statistics place the most blame for accidents on human error with the operator being responsible for the largest percentage. Operator error is not the real cause at all, but only a “symptom” of the cause. The underlying cause of most crane accidents is our failure to determine and maintain an operator’s qualifications.
Preventing Accidents
The most important step in preventing accidents then, is to allow cranes to be operated only by trained and qualified personnel. Even though these requirements are published in Occupational Safety and Health Administration standards, the process by which operatory competency and qualifications are determined needs clarification.
In the American National Standards Institute B30.5 (1982), a widely referenced National Consensus Standard on Mobile and Locomotive Cranes is the heading “Qualifications For Operators.” It says that “Operators shall be required by the employer to pass a written or oral examination and a practical operating examination unless able to furnish satisfactory evidence of qualifications and experience. Qualifications shall be limited to the specific type of equipment for which examined. Operators and operator trainees shall meet the following physical qualifications.”
In this portion of the standard, an operator’s qualifications is a process involving three areas. If failure to demonstrate competency in any one area is discovered, the operator must be considered unqualified to operate the crane.
Physical Traits
The operator must meet the following physical qualifications:
Vision of at least 20/30 Snellen in one eye and 20/50 in the other, with or without corrective lenses.
Ability to distinguish colors, regardless of position, if color differentiation is required for operation.
Adequate hearing, with or without hearing aid, for the specific operation.
Sufficient strength, endurance, agility, coordination, and speed of reaction to meet the demands of equipment operation.
In addition, evidence of physical defects or emotional instability that could “render a hazard to the operator or others, or which in the opinion of the examiner could interfere with the operator’s performance, may be sufficient cause for disqualification. In such cases, specialized clinical or medical judgments and tests may be required.”
Evidence that an operator is “subject to seizures or loss of physical control shall be sufficient reason for disqualification. Specialized medical tests may be required to determine these conditions.
“Operators and operator trainees should have normal depth perception, field of vision, reaction time, manual dexterity, coordination, and no tendencies to dizziness or similar undesirable characteristiscs.”
The operator also is required to pass a written examination for mental competence to be assured. Even though an oral examination and evidence of qualifications and experience are allowed by ANSI as proof of qualifications, a more verifiable means is the use of written tests.
If these exams are designed properly, they are normally far more objective. Oral examinations tend to be subjective: an accurate determination of the operator’s mental abilities depends solely on the personal judgment of the examiner.
Written examinations not only will reveal whether operators possess the required knowledge, but they also will reveal if an operator is illiterate.
In fact, according to Jonathan Kogel, author of Illiterate America, there are 60 million illiterate adults in America. Of these 60 million, 46 million adults are considered functionally illiterate—where they function at a fifth grade level in basic skills. This level is definitely not high enough to comprehend and assimilate the technical information found in operator’s manuals and load charts, especially for the mobile hydraulic cranes built today.
Hard to Measure
The final area ANSI identifies for examination is the operator’s practical competence. This area, compared with the physical and mental, is perhaps the most difficult to determine. Maintaining objectivity is far more difficult.
The person conducting the practical tests must be qualified (with a solid background in use and operation of mobile cranes) to accurately determine proper operating speeds, movement, techniques and procedures.
Furthermore, an obstacle course should be designed to cover any and all responsibilities and experiences the operator is expected to perform.
When the outcome of these examinations are evaluated, they will reveal any deficiencies the operator may have.
Training
It is important when developing an in-house program or acquiring the services of an outside company to remember to develop the program to meet specific needs and applications.
For operators this would include both classroom and hands-on training. The classroom instruction should include theory of operation, technical data, applicable standards, manufacturers’ information and rigging—all with an emphasis on safety.
Equal time should be devoted to hands-on or practical instruction. This is where the operator is actually taught how to inspect, set up and operate the crane in a lift situation. It is here that the operator can see the relevance of what was taught in the classroom, thus meeting the objective of safe crane operation.
A Good Teacher
Selecting the appropriate instructor also is crucial. Not only should this person possess the technical knowledge associated with your particular equipment, but he should have a thorough understanding of applicable government and industry standards and how they relate to the operator and his job.
Don’t select someone who has acquired his knowledge only through books. This will only result in the training program being “bookish” thus lacking the required depth and practical application.
Finally, look for an instructor who has the ability to communicate. He does not have to be an orator, but he should be able to make the material relevant and help the operator understand the importance of his training.
References
- Dickie, D.E. “Mobile Crane Accidents,” Construction Safety Association of Ontario, revised September 1986, p. 2.
- Headley, James. “In Defense of the Operator.” Cranes Today, December/January 1988, p. 45.
- Headley, James. “The Employer’s Duty.” Cranes Today, February 1988, p. 39.
- IBID p. 39.
By James Headley, BS, Director; Crane Institute of America, Altamonte Springs, Fla.