M.H.Hawash, Process Engineer
Engineering for Petroleum and Process Industries (ENNPI), Egypt.
W.M.Shehata, F.K.Gad, Faculty of Petroleum and Mining Engineering
Department of Refining and Petrochemical Engineering, Suez University, Egypt.
Development of Process Safety System by Using LOPA with Applying Conditional Modifiers.
Authors
Abstract
This paper presents systematic approach of reducing the total Safety Integrity Level “SIL”
rating for the Safety Instrument System “SIS” of Vacuum Distillate Unit “VDU”. The method
is applying the applicable conditional modifiers such as Ignition Probability and occupancy
factor during developing Layer of Protection Analysis Method “LOPA”. The results of this
approach that the SIL rating of VDU feed Node is reduced from SIL 3 to SIL 2 by using the
applicable condition modifiers. Such Reduction in SIL rating without reducing the required
safety measures has a great impact for the total cost reduction of the unit and reduce design and
installation, operation and maintenance complexity and cost.