• Record Type: Interpretation
• Standard Number: 1910.147
  
• Subject: Machine guarding.
• Information Date:1996

May 28, 1996

Mr. Michael D. Zoll, CSP
Manager of Safety
P.O. Box 6977
Cleveland, OH 44101-1977

Dear Mr. Zoll:

This is in response to your letter of February 3, 1995, in regard to machine guarding. We apologize for the delay in our response.

As a general rule, no violation exists if no employee is exposed, or is likely to be exposed to a hazard (the hazards are not accessible under any normal circumstances). Standards requiring barrier guards are intended to prevent employees who work in hazardous locations from hazards such as those you described in your letter. It may be possible for an employer to address moving parts hazards by limiting employee access to the area in which such hazards are present.

Keeping in mind the general rule, please find in the following, the questions that you listed (scenarios described) and our evaluation with respect to each scenario.

Question 1. We have a large aluminum hot rolling mill. Several areas behind the mill contain multiple large diameter drive shafts and couplings, as well as other complex hazardous moving parts. The individual shafts, couplings, and moving parts are not individually guarded. However, awareness barriers are provided in the form of a chain across the entry point with a DANGER sign instructing employees to not enter this area while the machine is running. The chain is not electrically interlocked to the mill, nor is any other form of machine guarding provided. Is this acceptable protection for these areas?

Question 2. The same type of equipment as mentioned in situation 1 exist, but the awareness barrier is in the form of standard railings with a self closing swing gate. The gate is not electrically interlocked to the mill. A similar DANGER sign is in place. No additional guarding is provided to the equipment inside the railing. Is this an acceptable method to control the mechanical power transmission hazard?

Response 1 and 2. Barrier guards are acceptable, so long as they are designed and constructed to prevent the operator or any other person from having any part of his body in contact with the moving parts of the machine. The machine guarding standard contemplates a physical means of preventing employee contact with the moving parts of machines. An awareness barrier such as a chain depends largely on human behavior, and so would not provide the necessary protection. Although awareness barriers would generally not meet the intent of the standard, one exception would be where there is no reasonably foreseeable reason why an employee would enter an area such as you describe. In evaluating the situation, however, an employer must be careful to consider every possible reason why an employee might enter the area. This could include reasons associated with the machinery, such as oiling and cleaning, and foreseeable employee misconduct, such as "sneaking a smoke."

Question 3. The same type of equipment as mentioned in situation 2 exist, but the access gates are padlocked closed. An employee must obtain a key from the team leader. Is this an acceptable method to guard the mechanical power transmission equipment and other hazards in this area?

Response 3. A locked access gate that prevents entry into the zone of danger created by moving machine parts would negate the need for additional guarding. However, your question presupposes that an authorized employee could gain entry into the restricted area by obtaining the key from a team leader. The machine guarding standards generally do not create a category of "authorized" employees who may be exposed to hazards of moving parts. The proposed method will satisfy the standard if employees can obtain the key to unlock the gate and enter the area only when moving parts hazards are not present.

Please also note that if the purpose of having access to the equipment is to perform servicing and maintenance on the machine, then the requirements of 1910.147, "The Control of Hazardous Energy (Lockout/Tagout)" may apply.

Question 4. The same type of equipment as mentioned in situation 2 exist, but the access gates are electrically interlocked. The interlock will send a signal to shut the equipment off, but due to the inertia in the equipment, the equipment will not stop immediately. The signal will prevent the equipment from continuing normal operation. The operator will have to evaluate the opened gate and reset the equipment before resuming operation. Is this an acceptable method to control the hazards?

Response 4. Based on the information that you have provided, an electrically interlocked gate would not be acceptable if there is enough time for an employee to come into the zone of danger before the machine stops and the hazard is removed. An interlock system should be provided with a time-delay device to coincide with the movement under the effect of inertia, so that the gate would not open until the moving parts of the machine come to a full stop.

Question 5. The hot rolling mill as described above has multiple stands. The gap between stands is approximately 3-5 feet. Employees are permitted to stand outside the mill and observe the sheet as it passes from one stand to the other. The aluminum sheet is traveling in excess of 1,000 feet per minute. The sheet enters the next stand of the mill and an in-running nip point exists. Due to the large size of the rolls and the complexity of the machine, the point of operation protection for this hazard is provided in the form of an awareness barrier. A self closing swinging gate is installed to prevent access to the gap between the stands. Is this an acceptable method of guarding?

Response 5. It is not entirely clear to us from your description where the stands, the gaps between stands, and the nip points are relative to each other. The answers we have given to your previous questions, however, should enable you to evaluate this situation.

Thank you for your inquiry. If you need further assistance, please contact Alcmene Haloftis of my staff at 202-219-8031.

Sincerely,



John B. Miles, Director
Directorate of Compliance Programs




February 3, 1995

Mr. John Miles, Directorate of
Compliance Programs
Occupational Safety and
Health Administration
Department of Labor
200 Constitution Ave. N.W.
Washington, DC 20210

Re: Machine Guarding

Dear Mr. Miles:

I have been asked to evaluate machine guarding around several types of equipment in our various plants. Specifically I am trying to determine if these situations comply with OSHA standards. I am also trying to explore our options to upgrade the protection as needed to bring these conditions into full compliance where needed. Please evaluate the conditions described and answer the specific questions listed with each scenario. I need to prepare a report to the plants involved by February 10, 1995 and would appreciate a quick response to these questions.

1. We have a large aluminum hot rolling mill. Several areas behind the mill contain multiple large diameter drive shafts and couplings, as well as other complex hazardous moving parts. The individual shafts, couplings, and moving parts are not individually guarded. However, awareness barriers are provided in the form of a chain across the entry point with a DANGER sign instructing employees to not enter this area while the machine is running. The chain is not electrically interlocked to the mill, nor is any other form of machine guarding provided. Is this acceptable protection for these areas.

2. The same type of equipment as mentioned in situation 1 exist, but the awareness barrier is in the form of standard railings with a self closing swing gate. The gate is not electrically interlocked to the mill. A similar DANGER sign is in place. No additional guarding is provided to the equipment inside the railing. Is this an acceptable method to control the mechanical power transmission hazard?

3. The same type of equipment as mentioned in situation 2 exist, but the access gates are padlocked closed. An employees must obtain a key from their team leader. Is this an acceptable method to guard the mechanical power transmission equipment and other hazards in this area?

4. The same type of equipment as mentioned in situation 2 exist, but the access gates are electrically interlocked. The interlock will send a signal to shut the equipment off, but due to the inertia in the equipment, the equipment will not stop immediately. The signal will prevent the equipment from continuing normal operation. The operator will have to evaluate the opened gate and reset the equipment before resuming operation. Is this an acceptable method to control the hazards?

5. The hot rolling mill as described above has multiple stands. The gap between stands is approximately 3-5 feet. Employees are permitted to stand outside the mill and observe the sheet as it passes from one stand to the other. The aluminum sheet is traveling in excess of 1,000 feet per minute. The sheet enters the next stand of the mill and an in-running nip point exist. Due to the large size of the rolls and the complexity of the machine, the point of operation protection for this hazard is provided in the form of an awareness barrier. A self closing swinging gate is installed to prevent access to the gap between the stands. Is this an acceptable method of guarding.

Please call me at (216)523-6990 if you need additional information to evaluate these questions or if you will be unable to respond before February 10, 1995.

Sincerely yours,



Michael D. Zoll, CSP
Manager of Safety