SAFETY in OVERPRESSURE RELIEVING SYSTEMS - KLM ...

KLM TechnologyGroupPractical Engineering Guidelinesfor Processing Plant SolutionsSAFETY in OVERPRESSURERELIEVING SYSTEMSENGINEERING DESIGN GUIDELINESPage 16 of 64Rev: 01October 20114. Output signal processing, interfacing and power5. Actuators and valve(s) or switching devices to provide the final control elementfunction.Input InterfacesCommunicationsOutput InterfacesInputsensorsInputinterfacesE/E/PE DeviceOutputinterfacesOutputsignalsOutputactuators/ finalcontrolelementsPower SuppliesValveFigure 7: Basic SIS layoutSafety Instrumented System (SIS) is an alternative for conventional relief device toeliminate the source of overpressure, thereby making relief capacity unnecessary. Theyare typically used where the provision of relief capacity is inappropriate. This is typically(but not always) due to one of the following factors:1. The fluid which would be discharged via a relieving device is toxic or extremelyhazardous2. Realistic evaluation of the overpressure scenario and quantification of the reliefload is difficult or impossible (e.g. explosive reaction)3. The cost of providing the necessary capacity in the disposal system or the reliefvalves is prohibitive.4. The vessel is not exclusively in air, water, or steam service.5. The user must ensure the MAWP of the vessel is higher than the highestpressure that can reasonably be achieved by the system.These design guideline are believed to be as accurate as possible, but are very general and not for specific design cases.They were designed for engineers to do preliminary designs and process specification sheets. The final design mustalways be guaranteed for the service selected by the manufacturing vendor, but these guidelines will greatly reduce theamount of up front engineering hours that are required to develop the final design. The guidelines are a training tool foryoung engineers or a resource for engineers with experience.This document is entrusted to the recipient personally, but the copyright remains with us. It must not be copied,reproduced or in any way communicated or made accessible to third parties without our written consent.