Process plant building safety

CCPS G-26. Guidelines for Evaluation Process Plant Buildings for External Explosions and Eires. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. 

For accidents affecting process plant buildings, the potential for serious or fatal injury to building occupants is the foremost concern. Additionally, in cases where buildings house critical controls or equipment, proper design and siting may also help reduce indirect safety impacts (e.g., due to loss of process control), as well as business interruption costs and property loss from such events. 

King, L. J.(compiler) Safety Analysis for the Transuranium Processing Plant, Building 7920, ORNL-3954 (April 1968). 

A pressure relief system is normally required on all bioreactors and pressurised tanks as a safety feature to comply with pressure vessel design regulations. In a few cases, some companies appear to have overcome the need to use a pressure relief system on the vessel either by ensuring pressure relief is provided on relevant pipework to the vessel and/or ensuring there are no pumps transferring material which could lead to a build up of pressure if the outlet pipework were closed. The absence of pressure relief on the vessels can considerably simplify the process plant. The safety and regulatory requirements, as well as insurance inspection requirements, for pressure relief is currently a confused area. 

Center for Chemical Process Safety (CCPS). Guidelines for evaluating process plant buildings for external explosions, fires and toxic releases. 2nd ed. New York, NY Wiley-AIChE 2012. 

CIA 1990. A Approach to the Categorization of Process Plant Hazard and Control Building Design. Prepared by Working Group 3 of the Major Hazards Steering Group. Issued by the Safety Committee of the Chemical Industry Safety and Health Council of the Chemical Industries Association, Eondon. 

These process safety management systems help ensure that facilities are designed, constructed, operated, and maintained with appropriate controls in place to prevent serious accidents. However, despite these precautions, buildings close to hazardous process plants have presented serious risks to the people who work in them. This observation is prompted by the fact that some buildings, because of their design and construction, have collapsed when subjected to comparatively moderate accidental explosions, with serious injury or fatality to the occupants. Conversely, experience indicates that personnel located outdoors and away from such buildings, if subjected to the same blast, may have a lower likelihood of serious injury or fatality. 

Safe unit placement enhances the overall safety of a pilot plant. A containment cell or a separate building is not, however, a guarantee of safety. Other measures include Increased process monitoring of safety specific variables, limiting inventories of hazardous feedstocks and products, detailed hazard analysis and risk assessments, and good design practices. One essential element is to ensure that the pilot plant has adequate space to support its operation. This requires a careful evaluation of the required space before the unit is constructed. While a detailed layout and a careful... 

For example, a construction crew may be erecting a new administration building at a process plant site. The contract workers who pour the concrete and erect the steel work will not have any contact with the people who work on the processes, nor will they be directed by the site supervisors. Therefore, they are true contract workers. At the other extreme is a maintenance worker who has worked on the facility for many years and who reports directly to the facility s supervision. Even though this worker may be on contract in an administrative sense, regulatory agencies such as Occupational Safety and Health Administration (OSHA) would regard him or her as being equivalent to a full-time employee. 

Criticality. The process plant is designed on the principle of safe geometry under all conditions (e.g., the use of HARP tanks). Continuous monitoring is provided by an approved criticality detection and alarm system. Where additional operational control is required to maintain safe conditions, this is specified in the appropriate nuclear safety assessments and Criticality Clearance Certificate. The latter specifies limits and conditions that need to be complied with during operations for example, in respect of limited tap density, moisture content, isotopic inventory and mass. It identifies any systems or instrumentation that demonstrate that compliance is maintained during operation. In addition key points of the plant are monitored by neutron monitors to give early warning of the unanticipated build-up of solid plutonium which could lead to the development of unsafe conditions. 

Check lists serve to draw one s attention to safety relevant issues. They reflect to a large extent the experiences with the design, building and operation of plants and the corresponding safety analyses. Apart from the normal operation the lists should cover start-up and shut-down as well as other possible plant states. In what follows a checklist for process plants is presented. Further information can be found in the relevant literature, for example also in [9]. 

There are many hundreds of important safety valves installed in a nuclear plant. Although they are components common to all process plants, the peculiar needs concerning perfect leak proofing, big sizes, quickness of action and high reliability demanded by nuclear plants make this component a particularly difficult one to build and maintain in compliance with regulations. As an example, the leak-proof specifications of some valves for nuclear plants were considered by many manufacturers, at the start of this industry, beyond the possibility of human technology . Obviously, system provisions do exist which may alleviate the task of the valves, such as redundancy and diversity incorporated in the design, however, even if these are considered, a valve remains one of the most critical components in a plant. 

If ambient conditions normally exceed about 50% RH for extended periods (more than about 8 h), provisions should be made to dehumidify the process plant and bulk storage buildings. Cooling and proper ventilation may also be necessary for worker comfort and safety. Adequate ventilation is especially important because all buildings should be tightly constructed and closed to maintain a dry inside environment (RH of 40%-50%). 

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