CHAPTER 24 Safe Work Practices and Permit-to-Work System 24.1 INTRODUCTION OSHA s Process Safety Management (PSM) Standard (OSHA, 1992) requires employers to develop and implement safe work practices (SWPs) to control hazards during operations such as lockout/tagout, confined space entry, opening process equipment or piping, and entrance into a facility by maintenance, contractor, laboratory, or other support personnel. SWPs often apply to hazardous work (HSE, 2002). For example, a permit is required for hot work by the PSM standard. The use of permits is governed by a set of procedures, called a permit-to-work (PTW) system. OSHA regulations exist for other types of hazardous work such as confined space entry (OSHA, 1998) and lockout/tagout (OSHA, 1996). Many accidents have occurred during the performance of hazardous work (Kletz, 1988). Worker fatalities and injuries have occurred when confined spaces containing unsafe atmospheres were entered, piping containing hazardous chemicals was opened, and work was performed on equipment while still energized. Such accidents can often be attributed to human factors issues. A survey by the UK Health and Safety Executive found that the largest single cause of maintenance-related accidents was the lack of or deficiency in PTW systems (HSE, 2002). A company considered hot work to be staightforward and maintained a supply of pre-signed permits for use by anyone conducting hot work. An untrained contractor used one of the permits to cut open a line containing flammable material causing a fire. 24.2 ISSUES The following human factors issues should be addressed in designing, implementing and operating safe work practices and PTW systems. Human Factors Methods for Improving Performance in the Process Industries 159 2007 American Institute of Chemical Engineers
160 SAFE WORK PRACTICES AND PERMIT-TO-WORK SYSTEM People Only authorized and qualified personnel should perform hazardous work. See Chapter 29 on Competence Management for more information. Hazardous work, by its nature, may be more stressful than normal work. Consequently, human factors such as stress, fatigue and shiftwork are particularly important. See Chapter 17 on Shiftwork Issues for more information. Other individuals involved in hot work such as the permit issuer, fire watch, and rescue personnel should also be qualified. Training and Briefing Involved personnel should be appropriately trained and briefed before they perform work. The training should be relevant to the actual work and circumstances under which it will be performed. Persons performing hot work should be briefed on the work to be performed at the job site so that the equipment and hazards involved and the precautions required can be pointed out. Personnel performing hazardous work often use specialized equipment such as hoists and other lifting equipment; personal protective equipment (PPE) such as supplied-air systems; and safety equipment such as rescue lines. Training should include the use of such equipment. Personnel should also be trained in the recognition of when SWPs and a permit are needed. If hazardous work is performed infrequently, the need for refresher training is particularly important. The nature of the work to be performed can vary from job to job so that specific briefings may be needed. Affected personnel in operations, maintenance, safety, and others such as contractors and temporary employees, should be included, as appropriate. See Chapter 12 on Training for more information. Communications PTW systems are in large part communications systems for facility personnel. Personnel performing hazardous work need to communicate with each other, standby personnel, operating personnel, and supervisors. Communications may be in written form such as procedures, permits, labels, and signs; it may be verbal such as spoken instructions; or it may be nonverbal such as hand signals in the field. In some situations two forms of communication should be used such as both verbal and written instructions. The means of communicating critical information should be specified. Hazardous work should be properly described for workers by responsible personnel. Figures and drawings may be useful to assist in describing the work, its location and limitations. Those who perform hazardous work should be given the opportunity to discuss the work with those authorizing it. It is poor practice to leave a permit on a desk to be picked up because it discourages communication. Permits should be suitably displayed, e.g. in the permit coordination room, main control room, local control rooms, and at the work site. Entries in permits should be legible and permits should be able to withstand the environments in which they will be displayed, such as at the work site.
24.2 ISSUES 161 Permits should be cross-referenced where there is interaction between jobs, including isolations if they are common to more than one job. Particular attention should be paid to the hand back from personnel performing hazardous work to those responsible for its operation. See Chapter 13 on Communications for more information. Procedures Hazardous work should be performed according to established safe work practices. The procedures should fully document how the SWPs and PTW system works, the circumstances under which it should be used, and the responsibilities of those involved. See Chapter 22 on Procedures for more information. Precautions Personnel carrying out hazardous work and process operators must be aware of, understand, and carry out those actions needed to ensure the work is performed safely and does not adversely impact people or the process. Permit issuers should be sufficiently knowledgeable and able to determine the hazards involved and the precautions needed for hazardous work. Permits should designate individuals for special roles such as fire watch and rescue. Isolation requirements should be specified. Precautions must be specified, communicated, and understood. PTW systems should verify that these requirements have been met. Identification Significant potential exists in hazardous work for the wrong piece of equipment or the wrong location to be selected. Correct and clear identification of equipment and locations is critical. This should be covered in writing in the permit and reinforced verbally, ideally in the field. Chapter 11 on Labeling provides more information relating to identification. Checks Critical actions in performing hazardous work, such as confirming isolations are in place, should be checked independently by someone other than the individual performing the action. Confirmation should usually be documented by signature. Environmental Factors Hazardous work is often conducted in adverse working environments. Access and working space may be restricted. Physical movement of workers may be impeded by the need to wear PPE. Environments may be hot, humid, cold, noisy, and so on. The potential impact of these factors on hazardous work should be addressed. See Chapter 15 on Environmental Factors for more information.
162 SAFE WORK PRACTICES AND PERMIT-TO-WORK SYSTEM Equipment and Process Design The usability of tools and equipment employed in performing hazardous work and the way in which personnel interact with the process while carrying out work affect the likelihood of human failures. Such failures are particularly significant since they occur during the performance of inherently hazardous activities and may have significant impacts on the workers involved. Specialized tools and equipment are often used in hazardous work, for example, welding equipment, breathing equipment, and lifting equipment, and workers may be less familiar with them and less skilled in their use. Necessary tools, equipment, parts, supplies and materials should be specified and their availability ensured. See Chapter 8 on Facilities and Workstation Design and Chapter 4 on Process Equipment Design for more information. Unauthorized Changes Deviations from SWPs, changes in materials, tools, or equipment, and so on should not be permitted without a suitable review. A separate permit should be issued if it is determined that other work is needed during the performance of permitted work. See Chapter 25 on Management of Change for more information. Time Constraints and Pressures In some circumstances there may be time pressures on performing hazardous work that may result in cutting corners and short cuts. For example, excessive workloads may occur during turnarounds, revamps, etc. and PTW systems can be overloaded. PTW systems should be designed to accommodate such situations, for example, by ensuring a sufficient number of trained contractor personnel will be available and that the PTW system does not include non-critical activities. See Chapter 16 on Workload for more information. Issuing permits with a duration longer than the job is reasonably expected to take should be avoided. Generally, multiple-day permits should not be issued since conditions can change from day to day, even with unknowns such as the weather. A renewed permit should be issued each day. Hazardous work should be properly described and authorized by a responsible person. Responsibilities for hazardous work, including safety precautions, should be defined and assigned. Personnel responsible for overall control of the work and its execution should be specified. Needed resources should be available. Appropriate supervision of personnel using the PTW system should be provided and SWPs and the PTW system should be properly managed, inspected and reviewed. Culture Some personnel may resist the use of SWPs and PTW systems. They may not be familiar with how these systems work or believe they are not needed. Other personnel
24.3 TOOLS 163 may embrace them as a significant contribution to safety. See Chapter 19 on Safety Culture for more information. Permit Design Permits should be tailored to the type of hazardous work so that emphasis is given to the particular hazards present and the precautions required, i.e. separate permits should be used for different types of work. Standard formats should be used to facilitate training and reduce the chance of failures. Permits should be readily identifiable, clearly laid out, legible and readily usable under the circumstances in which they may be employed. They should contain document control information including a revision number and issue date. Statements or questions that could be ambiguous or misleading should be avoided. See Chapter 14 on Documentation Design and Use for more information. PTW System Design The PTW system should match the organization s structure and procedures. PTW systems should not be used unless they are really needed since overuse will diminish their value. An explosion in the gas compression module of the Piper Alpha oil production platform in the North Sea resulted in 167 fatalities. A key contributing cause of the accident was the lack of an effective PTW system. This resulted in condensate being admitted to a pump from which the pressure safety valve had been removed. An atmospheric release occurred followed by an explosion and fire. 24.3 TOOLS The human factors issues described above can be used as design criteria for SWPs and PTW systems. Guidance on the design and use of SWPs and PTW systems is available in the literature (HSE, 1997; HSE, 2002; Lees, 1996; CCPS, 1995). Hazard analysis and risk assessment methods can be used to identify human failures and human factors issues for hazardous work. The analyses identify possible errors and the factors that influence their likelihood. See Chapter 26 on Qualitative Hazard Analysis, and Chapter 27 on Quantitative Risk Analysis for more information. Regular monitoring is needed to ensure correct implementation and use of SWPs and PTW systems. Spot checks on permits should be performed and comparisons made of permits with the work being performed. Deviations should result in immediate corrective action. Audits against best-practices using checklists should be conducted at defined intervals (CCPS, 1993). Reviews of the system effectiveness
164 SAFE WORK PRACTICES AND PERMIT-TO-WORK SYSTEM should be made at longer intervals with input sought from involved workers and supervisors. 24.4 REFERENCES CCPS (1993), Guidelines for Auditing Process Safety Management Systems (NY: AICHE Center for Chemical Process Safety). CCPS (1995), Guidelines for Safe Process Operations and Maintenance (NY: AICHE Center for Chemical Process Safety). HSE (1997), Guidance on Permit-to-Work Systems in the Petroleum Industry (Sudbury, UK: HSE Books). HSE (2002), Permit-to-work systems (Sudbury, UK: HSE Books). Kletz, T. A. (1988), What Went Wrong? Case Histories of Process Plant Disasters, 2nd ed. (Houston, TX: Gulf, Houston, TX). Lees, F. P. (1996), Loss Prevention in the Process Industries. Hazard Identification, Assessment and Control, 2nd ed. (Oxford, UK: Butterworth-Heinemann). OSHA (1992), Process Safety Management of Highly Hazardous Chemicals; Explosives and Blasting Agents, 29 CFR 1910.119 (Washington, DC: Occupational Safety and Health Administration), published 2/24/1992 and effective 5/26/92. OSHA (1996), The Control of Hazardous Energy (Lockout/Tagout), 20 CFR 1910.147 (Washington, DC: Occupational Safety and Health Administration). OSHA (1998), Permit Required Confined Spaces, 20 CFR 1910.146 (Washington, DC: Occupational Safety and Health Administration). 24.5 ADDITIONAL REFERENCE HSE (1997), The Safe Isolation of Plant and Equipment (Sudbury, UK: HSE Books).