Pressure-relief systems

Once the process route has been chosen, it may be possible to synthesize flowsheets that do not require large inventories of materials in the process. The design of the reaction and separation system is particularly important in this respect, but heat transfer, storage, and pressure relief systems are also important. 

Designers of emergency pressure relief systems should be famihar with the fohowing hst of regulations, codes of practice, and industiy standards and guidehnes. 

FIG. 26 13 Typical pressure relief system configurations (a) rupture disk system (h) pressure relief valve system. 

Since discharges of vapors from highly hazardous toxic materials cannot simply be released to the atmosphere, the use of a weak seam roof is not normally acceptable. It is best that tanks be designed and stamped for 15 psig to provide maximum safety, and pressure relief systems must be provided to vent to equipment that can collect, contain, and treat the effluent. 

Vent Sizing Package (VSP) The VSP is an extension of ARC technology. The VSP is a bench-scale apparatus for characterizing runaway chemical reactions. It makes possible the sizing of pressure relief systems with less engineering expertise than is required with the ARC or other methods. 

Wilday, A.J. 1991. The Safe Design of Chemical Plants with No Need for Pressure Relief Systems. Elazards IX—New Directions in Process Safety. IChemE Symposium Series. No. 124, pp. 243-253. Institute of Chemical Engineers, IChemE, Rugby, U.K. 

Rearick, How to Design Pressure Relief Systems, Parts I and II, Hydrocarbon Processing, August/ September 1969. 

Isaacs, Marx, Pressure Relief Systems, Chemical Engineering, February 22, 1971. 

Large-scale storage containers are usually of metal and equipped with pressure-relief systems. 

In applying this rule, the capacity of the pressure relief system must also be sized to handle the quantity of fluid released at this pressure (together with other expected loads during this contingency), so that the built-up back pressure will not result in exceeding 1.5 times the design pressure. This additional load need not, however, be considered in calculations of flare and PR valve radiant heat levels. 

Isolation Valves for Pressure Relief Systems - Block valves for maintenance isolation purposes are permissible in pressure relieving systems, provided that they are car sealed open and comply with the requirements of CSO valves. The particular locations where such CSO valves are p>ermitted are ... 

Huff, J. F., 1985, Multiphase Flashing Flow in Pressure Relief Systems, Plant Operations, 4, 191-199. 

The common theme of many of these items is that blowdown lines and flare and vent stacks should be kept simple because they are part of the pressure relief system. Avoid flame arrestors, molecular seals, water seals, and U-bends. Avoid steam, which brings with it laist and scale and may freeze. 

M. Kneale, The Safe Disposal of Relief Discharges, Selection Use of Pressure Relief Systems for Process Plants, Institution of Chemical Engineers North Western Branch, Manchester. UK, 1989, Paper 7. 

Compliance. Compare achievement in specific PSM elements against previous audit findings for the site. This helps indicate the effectiveness of the management system. For example, if previous audits found that preventive maintenance was not kept up to date on pressure relief systems, has the system weakness (or absence) that allowed this to occur been corrected ... 

First K. E. and J. E. Huff, Design Chaits for Two-Phase Flashing Flow in Emergency Pressure Relief Systems, Plant Operations Progress, Vol. 8, No. 1, 1989, p. 40. 

Huff, J. E., Frontiers in Pressure Relief System Design, Ibid., p. 44. 

Shaw, D. A., S,VFIRE Program for Design of Emergency Pressure Relief Systems, CEP, 14—17, July 1990. 

Vents from pressure-relief systems and governor vents ... 

Parkinson, J. S. (1979) Inst. Chem. Eng. Sym. Design 79, Kl. Assessment of plant pressure relief systems. PARRY, C. F. (1992) Relief Systems Handbook (Institution of Chemical Engineers, London). 

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