Replacement of Nitrogen Pressure Vessel Seals

A group of employees are assigned to replace the head seals on twelve large nitrogen pressure vessels (accumulator bottles) at a manufacturing facility. Each pressure vessel has an operating pressure of about 5,000 psig. Replacement of the seals on each vessel requires that its head be opened, releasing any vessel contents to the atmosphere. The vessels lack individual gauges to indicate internal pressure levels.

Question 1

Yes: Correct.

The pressurized nitrogen would be considered an energy source. A vessel pressure of 5,000 psig clearly represents a hazardous level of energy. Therefore, the energy source must be bled off, and the vessel secured at atmospheric pressure, before the seals can be replaced.
No: Incorrect. Actually, the answer here is yes.

The pressurized nitrogen would be considered an energy source. A vessel pressure of 5,000 psig clearly represents a hazardous level of energy. Therefore, the energy source must be bled off, and the vessel secured at atmospheric pressure, before the seals can be replaced.

Question 2

Were the employees performing a servicing and/or maintenance operation that was subject to unexpected energization, start up, or release of hazardous energy?

Yes: Correct.

An unexpected release of high pressure during a seal-replacement operation could have potentially fatal consequences.
No: Incorrect. Actually, the employees' work was subject to unexpected energization, start up, or release of hazardous energy.

An unexpected release of high pressure during a seal-replacement operation could have potentially fatal consequences.

Question 3

Does the Lockout/Tagout standard apply to this particular servicing and/or maintenance operation?

Yes: Correct. The Lockout/Tagout standard would apply here.

The potential for unexpected release of hazardous energy from the nitrogen pressure vessel existed during this operation and posed the risk of injury to the employees.

The employer should develop and implement an energy control procedure meeting the requirements of 1910.147(c)(4). This would ensure that all hazardous energy is identified and secured at the energy isolation points, that internal pressure is safely relieved from the nitrogen pressure vessels, and that there is no potential for energy reaccumulation during the maintenance operation.
No: Incorrect. In this case, the Lockout/Tagout standard would apply.

The potential for unexpected release of hazardous energy from the nitrogen pressure vessel existed during this operation and posed the risk of injury to the employees.

The employer should develop and implement an energy control procedure meeting the requirements of 1910.147(c)(4). This would ensure that all hazardous energy is identified and secured at the energy isolation points, that internal pressure is safely relieved from the nitrogen pressure vessels, and that there is no potential for energy reaccumulation during the maintenance operation.

Question 4

Yes: Correct.

The employer is required to implement a procedure which affords each person working on this pressure vessel a level of protection equivalent to that provided by the implementation of a personnel lockout or tagout device. Under these circumstances, each employee must affix a personal lock or tag either on each energy isolation device or on the group lockout device, group lockbox, or comparable mechanism, and each employee must be permitted to verify that all energy sources are effectively isolated.

For more information: Refer to the Lockout/Tagout standard part 1910.147(f)(3), STD 1-7.3, paragraph H.8 (a through h) (Note: You must scroll to paragraph H.8.), and the detailed discussion and acceptable examples in Appendix C, paragraph B (Note: You must scroll to paragraph Appendix C, paragraph B.).
No: Incorrect. The group lockout or tagout provisions would apply here.

The employer is required to implement a procedure which affords each person working on this pressure vessel a level of protection equivalent to that provided by the implementation of a personnel lockout or tagout device. Under these circumstances, each employee must be permitted to verify that all energy sources are isolated and to affix a personal lock or tag either on each energy isolation device or on the group lockout device, group lockbox, or comparable mechanism.

For more information: Refer to the Lockout/Tagout standard part 1910.147(f)(3), STD 1-7.3, paragraph H.8 (a through h) (Note: You must scroll to paragraph H.8.), and the detailed discussion and acceptable examples in Appendix C, paragraph B (Note: You must scroll to paragraph Appendix C, paragraph B.).

Question 5

Yes: Incorrect. Not in this case.

The Lockout/Tagout standard does not specifically require the use of a work authorization permit. An employer may choose to use a generic energy control procedure and a work authorization permit to meet the requirements of 1910.147(c)(4). If the employer uses this method, the work authorization permit must identify the equipment to be serviced or maintained, the types and unique energy characteristics to be encountered, methods for safe work, and the process or procedures to be used to safely accomplish the task. The company procedure must specify that the employees are required to perform their work in accordance with the terms and limitations of the work permit.

For more information: Refer to the April 10, 1991, letter of interpretation to Mr. Duane Barns, Dow Chemical U.S.A., for further details.
No: Correct.

The Lockout/Tagout standard does not specifically require the use of a work authorization permit. An employer may choose to use a generic energy control procedure and a work authorization permit to meet the requirements of 1910.147(c)(4). If the employer uses this method, the work authorization permit must identify the equipment to be serviced or maintained, the types and unique energy characteristics to be encountered, methods for safe work, and the process or procedures to be used to safely accomplish the task. The company procedure must specify that the employees are required to perform their work in accordance with the terms and limitations of the work permit.

For more information: Refer to the April 10, 1991, letter of interpretation to Mr. Duane Barns, Dow Chemical U.S.A., for further details.