Valves protection systems

The Guidelines for Process Equipment Reliability Data with Data Tables covers a variety of components used in the chemical process industry, including electrical equipment, analyzers, instrumentation and controls, detectors, heat exchangers, piping systems, rotating equipment (pump, compressor, and fan), valves, and fire protection systems. 

In the cathodic protection of storage tanks, potentials should be measured in at least three places, i.e., at each end and at the top of the cover [16]. Widely different polarized areas arise due to the small distance which is normally the case between the impressed current anodes and the tank. Since such tanks are often buried under asphalt, it is recommended that permanent reference electrodes or fixed measuring points (plastic tubes under valve boxes) be installed. These should be located in areas not easily accessible to the cathodic protection current, for example between two tanks or between the tank wall and foundations. Since storage tanks usually have several anodes located near the tank, equalizing currents can flow between the differently loaded anodes on switching off the protection system and thus falsify the potential measurement. In such cases the anodes should be separated. 

All respiratory protective systems should be stored in clean, dry conditions but be readily accessible. They should be inspected and cleaned regularly, with particular attention to facepiece seals, nonreturn valves, harnesses etc. Issue on a personal basis is essential for regular use otherwise the equipment should be returned to a central position. Records are required of location, date of issue, estimated duration of use of canisters etc. 

The entire contents of the protected system are lost when the disc ruptures. This necessitates a shutdown of the operation for replacement of the disc, unless a block valve is installed upstream. 

Secondary containment systems are best described as passive protective systems. They do not eliminate or prevent a spill or leak, but they can significantly moderate the impact without the need for any active device. Also, containment systems can be defeated by manual or active design features. For example, a dike may have a drain valve to remove rain water, and the valve could be left open. A door in a containment building could be left open. 

Integral safety relief valve works to protect system against excessive pressure. 

A type of valve located in the steam line and elsewhere that automatically cuts the boiler in and out, thus providing for online and offline operation. This valve protects the steam system in the event of a loss of pressure from a boiler, caused perhaps by a large steam leak. 

Whatever method is used, there should be a clear design philosophy for the basic process control system (BPCS) employed at a facility that is consistent throughout each process and throughout the facility. Consistency in application will avoid human factor errors by operators. The philosophy should cover measurements, displays, alarms, control loops, protective systems, interlocks, special valves (e.g., PSV,... 

An active fire protection system requires some action to occur before it functions per its design intent. This action may be taken by either a person or control system. Examples of active fire protection systems are monitors, water spray systems, foam systems, emergency isolation valves, and ESD systems. 

Other supervisory signals may come from fire protection system components such as supervised control valves, system air and supervisory air pressure transmitters, water tank level and temperature transmitters, valve house and fire water pump building temperature transmitters, and fire water pumps. 

The project plan should encompass all aspects of a fire protection system, such as the underground fire water distribution system, fire pumps, aboveground water header, valving and standpipes, structural support, and detection and alarm systems. All work on the fire protection system must be coordinated with other work activities at the site or in the operating unit. The recommended installation practices for the different types of fire protection systems are covered in consensus standards, such as NFPA. The installation process is illustrated in Figure 9-1. 

Inspections consist of a visual check of the fire protection systems by qualified personnel to ensure the system is available for immediate use. Visual checks should be made using a checklist. The inspection should verify that the fixed and portable equipment is ready to be operated. The associated devices, fittings, piping, and valving are inspected to ensure they have not been tampered with and that there is no obvious deterioration, physical damage, or condition to prevent operation. Documentation of the visual inspections may vary from... 

Fire Protection System System Design System Pressure System Control Valve Locations ... 

Protective system—Systems such as pressure relief valves that function to prevent or mitigate the occurrence of an incident. 

Errors that resulted in the component being unavailable when needed—For example, equipment not restored to full operability following maintenance, testing, or inspection. Valves left closed, actuation or protective systems not reconnected, slip-blinds left in the line, or failing to return pump selector switches to the standby auto-start position are common examples. 

Post Indicator Valve (PIV) A post-type valve diat provides a visual means of indicating "open" or "shut" position. It is found on the supply main of installed tire protection systems. Potentiation The effect of a chemical which does not itself have an adverse effect but which enhances the toxicity of another chemical. 

Leung, J.C. (1996) Easily size relief devices and piping for two-phase flow. Chemical Engineering Progress, 12, 28-50. Schmidt, J. and Giesbrecht, H. (2001) Evaluation of uncertainties for safety valve vent system compared to a model-based on-line vessel protection in a (certified) process controller, in ECCE-3, Nuremberg Germany. 

The primary purpose of a safety relief valve (SRV) is the last protection of life, environment and property in this process industry by safely venting process fluid from an overpressurized vessel. It is not the purpose of a safety valve to control or regulate the pressure in the vessel or system that the valve protects, and it does not take the place of a control or regulating valve... 

The main issue here as regards to SRVs is the Guidelines on the Application of Directive 94/9/EC of 23 March 1994 on the approximation of the laws of the Member States concerning equipment and protective systems intended for use in potentially Explosive Atmospheres Second edition - July 2005. The paragraph affecting SRVs is the section on what is called simple products (including simple valves), which remains in the guidelines and reads as follows ... 

The fire protection system consists not only of a deluge system activated by the ultraviolet sensors, but also of fusible link type fire systems. The deluge system has a trip mechanism from mercury checks activated by heat-activated-devices, a manual release on the deluge valve, a pneumatic remote trip station, and an electrical push button along with the electrical trip mechanism from the U/V detectors. The remote trip stations are located by escape routes so it is possible for the operator to trip the systems as he exits the building without exposing himself to further danger. 

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