Designing and operating safe chemical reaction processes HSG143

More documents

Recommendations

Info

Health and SafetyExecutiveThe Personal Protective Equipment at Work Regulations 199213 These Regulations 54 aim to ensure the free provision of personal protectiveequipment (PPE) where the risk has not been controlled by other means, andits safe use. They include general duties covering the selection of suitable PPE,maintenance, information, instructions and training. Guidance 55 on the Regulationsis available.The Pressure Systems Safety Regulations 199914 These Regulations 5 set down a range of duties on users of installed pressuresystems and owners of mobile systems. They include duties not to operate thesystem or allow its operation unless the safe operating limits of the pressuresystems are known. The systems must have a suitable written scheme ofexamination.15 A written scheme of examination is a planned scheme for periodic examinationof those parts of a pressure system in which a defect may give rise to danger.16 A pressure system includes any vessel and/or pipeline, with its associatedpipework (including valves and pumps, etc) that contains a relevant fluid. The term‘relevant fluid’ is defined in the Regulations and covers compressed or liquefiedgases above 0.5 bar gauge pressure, pressurised hot water above 110 o C andsteam at any pressure.17 An Approved Code of Practice 56 accompany the Regulations.The Pressure Equipment Regulations 199918 These Regulations 6 apply to the design, manufacture and conformityassessment of pressure equipment and assemblies. They apply when themaximum allowable pressure is greater than 0.5 bar above atmospheric pressure.19 If Schedule 1 (of PER) excludes a particular item of pressure equipment fromPER, then the PSSR 5 may apply to the initial supply of the equipment.20 Whichever set of Regulations cover the initial supply of the equipment, thePSSR cover the equipment while in-service.Provision and Use of Work Equipment Regulations 199821 These Regulations 4 aim to ensure the provision of safe work equipment and itssafe use. They include general duties covering the selection of suitable equipment,maintenance, information, instructions and training. They also address the need forequipment to be able to control selected hazards. Guidance is available. 57Designing and operating safe chemical reaction processes Page 42 of 64
Health and SafetyExecutiveAppendix two:Inherently safer chemicalreaction processes1 The four strategies for the design of inherently safer processes and plants are:(a) substitute;(b) minimise;(c) moderate; and(d) simplify.Some examples of inherently safer chemical synthesis routes have been given inparagraph 66 of the main text.2 Inherently safer design represents a fundamentally different approach tochemical process safety. 15,16 Rather than accepting the hazards in a process, andthen adding on safety systems and layers of protection to control those hazards,the challenge to the process designer is to reconsider the process and eliminatethe hazards. If the designer cannot eliminate the hazards the challenge becomesto minimise or reduce them as much as possible by modifying the process, ratherthan by adding external layers of protection.3 In considering inherently safer design alternatives, it is essential to rememberthat there are often, perhaps always, conflicting benefits and deficienciesassociated with the different options. Chemical processes usually have manypotential hazards, and a change that reduces one hazard may create a new one orincrease the magnitude of a different existing hazard. For example:(a) Chlorocarbon refrigerants are inherently safer with respect to fire, explosion andacute toxic hazards when compared to alternative refrigerants such asammonia, propane and sulphur dioxide. However, they have been shown tocause long term environmental damage because of stratospheric ozonedepletion.(b) Supercritical processing may use relatively non-hazardous materials such aswater or carbon dioxide as reaction and extraction solvents, but supercriticalprocessing may require high temperatures and pressures.(c) A solvent used in an exothermic reaction is non-volatile, and moderately toxic.An alternative solvent is less toxic, but also has a much lower boiling point.There is a trade-off between toxic hazards, the ability of the lower boiling pointsolvent to temper the exotherm at a lower temperature, and the possibility thatthe mixture may evaporate more rapidly.(d) A wide variety of applications including chlorination, ethoxylation,hydrogenation, and polymerisation reactions use continuous processes in loopreactors. However, facilities may be needed to deal with off-specificationmaterial produced during start-up or process malfunction.Designing and operating safe chemical reaction processes Page 43 of 64
Page 1: Health and SafetyExecutiveDesigning
Page 6 and 7: Health and SafetyExecutivethe Unite
Page 8 and 9: Health and SafetyExecutive22 This p
Page 10 and 11: Health and SafetyExecutive34 Increa
Page 12 and 13: Health and SafetyExecutiveCauses of
Page 14 and 15: Health and SafetyExecutive52 To add
Page 16 and 17: Health and SafetyExecutiveInitial a
Page 18 and 19: Health and SafetyExecutive75 More c
Page 20 and 21: Health and SafetyExecutive89 It is
Page 22 and 23: Health and SafetyExecutive100 The r
Page 24 and 25: Health and SafetyExecutive112 For t
Page 26 and 27: Health and SafetyExecutiveSelecting
Page 28 and 29: Health and SafetyExecutiveA serious
Page 30 and 31: Health and SafetyExecutiveProtectiv
Page 32 and 33: Health and SafetyExecutivea relief
Page 34 and 35: Health and SafetyExecutive176 The t
Page 36 and 37: Health and SafetyExecutive188 Writt
Page 38 and 39: Health and SafetyExecutive(f) the t
Page 40 and 41: Health and SafetyExecutiveAppendix
Page 46: Health and SafetyExecutiveNitroglyc
Page 49 and 50: Health and SafetyExecutiveV Ventila
Page 51 and 52: Health and SafetyExecutiveAppendix
Page 53 and 54: Health and SafetyExecutive15 Having
Page 55 and 56: Health and SafetyExecutive15 Bollin
Page 57 and 58: Health and SafetyExecutive50 Prepar
Page 59 and 60: Health and SafetyExecutiveFurther i
Page 61 and 62: Health and SafetyExecutiveDecomposi
Page 63 and 64: Health and SafetyExecutiveRate of r

Designing and operating safe chemical reaction processes HSG143

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?