Pressure hazard controls

Vapor Pressure The pressure exerted by a vapor above its own liquid. The higher the vapor pressure, the easier it is for a liquid to evaporate and fill the work area with vapors which can cause health or fire hazards. Venting Emergency flow of vessel contents out of a vessel. The pressure is controlled or reduced by venting, thus avoiding a failure of the vessel by overpressurization. The emergency flow can be one-phase or multi-phase, each of which results in different flow characteristics. 

Containment eliminates most opportunities for exposure and is the preferred method of control in chemical manufacturing. Actually, containment in many chemical plants is dictated by pressure, temperature, fire, or product-loss requirements and is really not a health-hazard control option. However, it must be recognized that containment is never perfect, releases and exposure opportunities will still occur, and additional control will probably be required. 

Fauske, H.K., 1987. Pressure relief and venting some practical considerations related to hazard control. Hazards from Pressure. Symposium Series No. 102. 133-142 (IChemE. Rugby. UK). 

Portions of the HCF structure, along with the steel confinement boxes (SCBs), gloveboxes, fume hoods, and the ventilation systems perform confinement functions. These confinement systems provide defense in depth by ensuring that hazardous materials are retained in specific designated areas within the HCF. They accomplish this function by maintaining an air pressure differential hierarchy from regions of greater contamination to those of lesser contamination within the facility. These differentials are described later in this section. This pressure differential controls the movement of contamination by diffusion and by adverse airflows. The Identified contamination zones in the HCF are as follows ... 

There are many kinds of system failures that can create emergencies. For example, intermption of operations may create hazardous conditions. Boiler overheating can cause dangerous conditions requiring quick action. Failure of temperarnre limit controls can lead to runaway processes. Failure of pressure limit controls can lead to rupmre of pipes, gaskets, vessels, and other equipment. Sudden releases of steam, gas, fuel, or hazardous chemicals can create dangers... 

Yin, YP. 2003. Seepage pressure effect on landslide stability at the Three Gorges Reservoir area. The Chinese J. of Geological Hazard Control, 14(3) l-8. (in Chinese)... 

Once, working on a two-phase flow systan, we needed to make sure that it was two-fault tolerant to an accident—in other words, after two failures, the system was still safe. We put in two relief valves to handle overpressure. The problem was they both had to operate in tandem to handle the flow and pressure profiles. That was an important example of validating that the hazard control is adequate. Obviously, the two relief valves weren t independent in their operations and therefore didn t independently control the hazard. Luckily, we validated our control was NOT adequate during testing and resized the relief valves. 

Provision and Use of Work Equipment Regulations 1998 and ACoP L22 The Pressure Systems Safety Regulations 2000 HSE Approved Code of Practice COP37 — Safety of pressure systems Control of Substances Hazardous to Health Regulations 2002... 

Hazard control personnel must ensure assessment of all work areas to identify unsafe electrical hazards. The pressure of current traveling through electrical conductors is known as volts. Resistance relates to the measured flow of electricity. We describe the measurement using the term ohms. Some materials such as metal offer little resistance and become conductors very easily. Other substances. 

Dow Fire and Explosion Index. The Dow Eire and Explosion Index (3) is a procedure usehil for determining the relative degree of hazard related to flammable and explosive materials. This Index form works essentially the same way as an income tax form. Penalties are provided for inventory, extended temperatures and pressures, reactivity, etc, and credits are appHed for fire protection systems, process control (qv), and material isolation. The complete procedure is capable of estimating a doUar amount for the maximum probable property damage and the business intermptionloss based on an empirical correlation provided with the Index. 

Explosibility and Fire Control. As in the case of many other reactive chemicals, the fire and explosion hazards of ethylene oxide are system-dependent. Each system should be evaluated for its particular hazards including start-up, shut-down, and failure modes. Storage of more than a threshold quantity of 5000 lb (- 2300 kg) of the material makes ethylene oxide subject to the provisions of OSHA 29 CER 1910 for "Highly Hazardous Chemicals." Table 15 summarizes relevant fire and explosion data for ethylene oxide, which are at standard temperature and pressure (STP) conditions except where otherwise noted. 

Pneumatic Controllers The pneumatic controller is an automatic controller that uses pneumatic pressure as a power source and generates a single pneumatic output pressure. The pneumatic controller is used in single-loop control applications and is often installed on the control valve or on an adjacent pipestand or wall in close proximity to the control valve and/or measurement transmitter. Pneumatic controllers are used in areas where it would be hazardous to use electronic equipment, in locations without power, in situations where maintenance personnel are more familiar with pneumatic controllers, or in applications where replacement with modern electronic controls has not been justified. 

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