Process equipment mechanical hazards

As the flowsheet becomes more firmly defined, the detailed process and mechanical design of the equipment can progress. The control scheme must be added and detailed hazard and operability studies carried out. All this is beyond the scope of the present text. However, all these considerations might require the flowsheet to be readdressed if problems are uncovered. 

This safety audit is used for identifying inputs and material flows, processes and intermediates, and final products - but with special attention paid to human-material/process/equipment interactions that could result in (a) sudden and accidental releases/spills, (b) mechanical failure-based injuries, and (c) physical injuries - cuts, abrasions, and so on, as well as ergonomic hazards. Additional sources of adverse effects/safety problem areas are records/ knowledge of in-plant accidents/near misses, equipment failures, customer complaints, inadequate secondary prevention/safety procedures and equipment (including components that can be rendered non-operable upon unanticipated events), and inadequacies in suppliers of material and equipment or maintenance services. 

The process material or equipment hazards, such as toxicity, fl anmability, electrical, and mechanical hazards ... 

Engineers select and evaluate process equipment. The selected equipment must be technically sound, rehable, safe and easy to operate, serviceable, economically attractive and environmentally sound, e.g. minimal noise pollution and no mechanical and fire hazards. For example, all pneumatic valves, except for the modulating valves, are air-to-open/ spring-to-close valve type for safe shutdown unless the valve is a divert drain valve as... 

A system, e.g., detection and isolation valves, to provide a positive mechanical barrier and block potential flame paths in process piping or ductwork that lead to other process equipment or operator occupied areas. Used where there is the potential for flame and pressure to travel to other areas resulting in additional fire or explosion hazards. An isolation valve system utilizes detection and control functions that initiate valve closure within milliseconds and operates at the earliest possible moment of a deflagration. 

The first step in the process is risk identification, which is accomplished by review of the proposal/study by suitably experienced experts using well-considered checklists. These must embrace all facets which may affect the project outcome, such as plant feedstock quality, process reliability, mechanical reliability, potential foundation problems, operational hazards, environmental impact, equipment costs, construction costing and labour, statutory requirements, contractual and legal problems peculiar to the country of construction, eventual decommissioning costs, and so on. Risks due to operational hazard are generally treated separately from commercial risk, and will be discussed in Chapter 12, but they are obviously an essential part of the overall process. 

Suggested control and instrumentation systems for the management of process equipment and components are described and outlined in API RP 14C, which is still relatively the arrangement utilized in the process industries. All process control systems are usually reviewed by a Process Hazard Analysis, which will deem if the provided mechanisms are adequate to prevent an incident from developing. 

Focus on certain factors at the time of audit, such as safe behavior, physical hazards, and personal protective equipment. Other concerns are work processes, body mechanics, unsafe acts or procedures, equipment use, and the pace of work. 

Engineering controls design the environment, the process, equipment, and/or materials to directly eliminate or control the hazard(s).The hazard may be completely removed or if it stiU exists, mechanisms are in place to contain it. This level attempts to remove latent human error potential from the process as well as control the scope and nature of hazards and associated risks (Prevention through Design, 2012). 

Equipment used to process, store, or handle highly hazardous chemicals must be designed constructed, installed and maintained to minimize the risk of release. A systematic, scheduled, test and maintenance program is preferred over "breakdown" maintenance " that could compromise safety. Elements of a mechanical integrity program include 1) identification and categorization of equipment and instrumentation, 2) documentation of manufacturer data on mean time to failure, 3 ) test and inspection frequencies, 4) maintenance procedures, 5) training of maintenance personnel, 6) test criteria, and 7) documentation of test and inspection results. 

Originally, equipment was made largely from wood or gun-metal and often rubber lined. These materials give the lowest hazards from friction with explosives. Nowadays, improved standards of engineering and of design have made it possible to employ stainless steel and plastics in the construction of explosive machinery with considerable increase in mechanical efficiency. In this way not only can processes be carried out more rapidly, but the quantity of explosive present at any time is reduced, with consequent increase in overall safety. 

---