‘Physical protection is part of LOPA. Various layers of protection are added to a process. The protection layers may include: inherently safer concepts; the basic process control system; safety instrumented functions; passive devices, such as dikes or blast walls, active devices, such as pressure relief valves; and human intervention.’
Reference: Adapted from Chemical Process Safety – Fundamentals with Applications, 2nd Ed.
‘Physical protection consists of a variety of measures to protect facilities, material, and personnel against undesirable consequences such as fire, explosion, gas release, sabotage, theft, and malicious outcomes or acts.’
Reference: incorporated from http://www.nrc.gov/security/domestic/phys-protect.html
Physical Protection (Relief Valves, Rupture Discs, etc.)
‘These devices, when appropriately sized, designed and maintained, are IPLs which can provide a high degree of protection against overpressure in ‘clean’ services. However, their effectiveness can be impaired in fouling or corrosive services, if block valves are installed upsteam of the relief valves, or if the inspection and maintenance regime is of poor quality. If the flow from the relief valves is discharged to the atmosphere, additional consequences may occur which will require examination. This could involve the examination of the effectiveness of downstream flares, quench tanks, scrubbers, etc.’
Reference: Adapted from Center for Chemical Process Safety (CCPS), “Layer of protection analysis: simplified process risk assessment.” American Institute of Chemical Engineers, 2001, xviii