Hazardous operating plant

On any hazardous operating plant, any change of circumstances must be assessed carefully, including careful risk assessment, before action is taken. Staff must be clear about the limits of their decision-making responsibilities. Operations management needs to keep acutely aware of the overall plant situation ( situational awareness , as discussed elsewhere) while also remaining sufficiently detached that they can make calm decisions about the best way forward when circumstances change. This is a difficult balance to achieve in practice - it requires hands-on detachment , i.e., full awareness with critical faculties intact. 

HAZOP (Knowlton, 1989 Lees, 1980 CPQRA, 1989, pp. 419-422). HAZOP stands for hazard and operability studies. This is a set of formal hazard identification and elimination procedures designed to identify hazards to people, process plants, and the environment. The techniques aim to stimulate in a systematic way the imagination of designers and people who operate plants or eqmpment so they can identify potenti hazards. In effect, HAZOP studies make the assumption that a hazard or operating problem can arise when there is a deviation from the design or operating intention. Corrective actions can then be made before a real accident occurs. 

Minimize inventory to the extent feasible. Expected benefits from minimum inventory may be offset by hazards resulting from more frequent and smaller shipments. The relative hazards should be reviewed (Englund, Design and Operate Plants for Inherent Safety—Part 1, Chem. Eng. Prog., vol. 87, no. 2, March 1991, pp. 85-91). 

E. N. Helmets and L. C. Schaller, Calculated Process Risks and Hazards Management, Plant/Operations Progress, 14, No. 4 (October), 229-31, 1995. 

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. 

A hazard and operability study is a procedure for the systematic, critical, examination of the operability of a process. When applied to a process design or an operating plant, it indicates potential hazards that may arise from deviations from the intended design conditions. 

Britton, L. G., Using material data in static hazard assessment Plant/Operations Prog. (AIChE), 11 56-70(1992). 

Full Scale Production—Reevaluation of chemical reaction hazards Newly revealed reactivity hazards from plant operations Management of changes Update of safety procedures as required Ongoing interaction of process safety with engineering, production, economic, andcommercial aspects of the process... 

Additional hazards in plant operations include specific gas and dust explosions, but such considerations are outside the scope of this book. Reference can be made to another CCPS Guidelines book [159] for issues relative to certain explosions. 

General Safety Precautions. The preparation and handling of the items covered by this specification, and the subassemblies thereof, involve hazardous operations and therefore require explosives safety precautions. Use of this specification will not be construed as to relieve the contractor or manufacturer of responsibility for the safety of his operations. Listed below are certain minimum provisions which a contractor or manufacturer (who prepares the item covered) should observe in order to fulfill his responsibility for safety. At Bureau of Naval Weapons, Navy Department, and other government plants, these provisions are mandatory. Such other warnings and precautions, pertinent to the operational effectiveness or safety during preparation of the specified items, are included in detailed technical requirements of the specification... 

R L Rogers, "The Advantages and Limitations of Dewar Calorimetry in Chemical Hazard Testing", Plant/Operations Progress, 8, 109-112, 1989... 

Examples of common safe practices are pressure relief valves, vent systems, flare stacks, snuffing steam and fire water, escape hatches in explosive areas, dikes around tanks storing hazardous materials, turbine drives as spares for electrical motors in case of power failure, and others. Safety considerations are paramount in the layout of the plant, particularly isolation of especially hazardous operations and accessibility for corrective action when necessary. 

Advance planning for the possibility of an accident will greatly minimize the consequences. A common hazard is found when a bench scale operation is scaled up when this scale-up occurs in an overutilized laboratory area. Solvents in small and large quantities may be found in the immediate vicinity and batches of oxidizers, expls and similar hazardous ingredients may be present where they may be exposed to ignition by one or more mechanisms. Often other personnel are present within the structure not knowing of the potentially hazardous operations which are conducted in their immediate vicinity. Exits and walk-ways may be blocked by materia-als, equipment or personnel in transit. While there is no safe expl, proplnt or pyrot material, familiarity does breed complacency. We are reminded of a recent expl of a BlkPdr replica plant (Ref 80) which resulted in the loss of life and the destruction of the plant. Nevertheless,... 

Buffer zones separating relatively hazardous operations from neighboring residential, commercial, or industrial properties also are important. The human toll in the Bhopal disaster was magnified by the fact that a town had been allowed to grow up at the plant s boundary. 

Rogers, R.L. (1989) The advantages and limitations of adiabatic dewar calorimetry in chemical hazards testing. Plant Operation Progress, 8 (2), 109-12. 

Once a complete flowsheet has been developed, the operability and control of the process can be considered. Moreover, the economic incentive for modifying the flowsheet to improve the control can be considered. Then a (hierarchical) procedure for the synthesis of a control system for the complete plant can be used as an additional tool for screening the process alternatives, and a preliminary hazardous operations study can be initiated. The results of this conceptual design study then provides an estimate of the economic incentive for initiating a more rigorous design study. 

Design Process design checks Unit processes Unit operations Plant equipments Pressure systems Instrument systems Hazard and operability studies (fine scale) Failure modes and effects analysis Fault trees and event trees Hazard analysis Reliability assessments... 

High-level waste reprocessing is the most hazardous operation in the nuclear industry. It is there that the largest quantities of fissionable and radioactive nuclides are handled in aqueous solution. These large-scale operations require both remote control and remote maintenance of the plant to protect the workers from radiation. In addition, the air and water effluents along with the solid refuse must be closely monitored to assure that the public is protected. Finally, the fissionable material requires strict accountability to ensure that it is not diverted to unauthorized uses. 

It becomes clear that the chances a single fire or explosion will spread to adjoining units can be reduced by careful plant layout and judicious choice of construction materials. Hazardous operations should be isolated by location in separate buildings or by the use of brick fire walls. Brick or reinforced concrete walls can serve to limit the effects of an explosion, particularly if the roof is designed to lift easily under an explosive force. 

Protective equipment must be used for protection from toxic gases and vapors and are required for normal hazardous operations such as working in a spray-painting plant, production and use of toxic chemicals, and fumigant use. Safe respiratory protective equipment is required for all these activities. 

In an operational plant there is a need to mark the container containing chemicals with proper labeling. These chemicals and hazards have been categorized into different classes. Different colors were assigned depending on their physical or chemical hazards as shown in Table 2.1. 

The most common use of personal protective equipment is for the protection of head, eyes, ears, torso, hands, and feet. This equipment helps to protect a person from damage normally encountered in an industrial plant, a construction site, or land renovation project. PPE includes devices and clothing designed to be worn or used for the protection or safety of an individual in potentially hazardous areas or performing potentially hazardous operations. 

Since clinical trials and toxicology studies require increasing amounts of product, an intermediate scale-up is often necessary. Scale-up may be performed in a pilot plant or in intermediate-sized laboratory equipment on-site or at a contract facility. As the scale increases, evaluation of the hazardousness of the operation sequence becomes necessary. Hazardous operation analysis may be done during this intermediate scale-up or during the detailed design. It is useful to take the results of the gap analysis and collect the appropriate data during intermediate scale-up. 

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