ISA TR84.00.03

Testing considerations of SIF should be included in most of theSafety Lifecycle steps described in ANSI/ISA-84.01-1996. Testingfrequency is a part of the determination of Safety Integrity Level(SIL) for the SIF. Provision for conducting tests must be includedin the selection of equipment and design of the SIF and thePre-Startup Acceptance Test (PSAT) is an integral part of ensuringthe SIF will provide the risk reduction necessary. Whenmodifications are made to SIF, testing can validate thatappropriate SIF action will still take place.

This technical report is an informative document providingguidance on performing testing of SIF components and systems thatwill help achieve full safety benefits of the SIF in the mostcost-effective way. Both manual and automated techniques arepresented for off-line and on-line testing of SIF and the benefitsof each technique described. Existing techniques and proposed newtechniques will be described. Utilizing the techniques described inconjunction with an overall safety management program will allowusers to meet the testing requirements of ANSI/ISA-84.01-1996 anddIEC 61511. Techniques are described for testing all elements ofthe SIF including field sensors, final control elements, logicsolvers (signal conversion modules included), Human MachineInterface (HMI), communication links with other systems, userapplication software, and other required auxiliaries such as power.Suggested inspection techniques for regular observation ofequipment and components to detect potential problems are alsopresented.

The techniques described can also be used for testing burnermanagement systems in conjunction with the NFPA 85 code.

These techniques are illustrated by the examples given inAnnexes A-MM. Each Annex is an example of how one companymight apply a given technique, and is not intended to represent aconsensus solution within the process industry.

Purpose

Systematic testing of each Safety Instrumented Function (SIF) isrequired to ensure that dangerous unrevealed failures have notoccurred that could render the SIF unable to perform the functionfor which it was provided. This testing ensures that alloperational functions of the SIF are evaluated on a periodicschedule in accordance with the safety integrity requirement of theSIF. Many processes have operating cycles that are longer than theperiod between testing required achieving the safety integrity.Thus performing the required off-line testing necessitates shuttingdown the process. This is costly and puts unnecessary strain onequipment and necessitates going through shutdown and startup(which are usually the most dangerous periods of a processlifecycle) again. Therefore, the ability to perform testing whilethe process remains in operation is desirable.

There are also different ideas on what constitutes an acceptabletest for various components of SIF. Whether the test is performedoff-line, with the process down, or on-line with the process inoperation, there are methods for performing the testing that ensurea high degree of detection of failures that might have occurred.Guidance is needed in the selection of these testing methods forboth off-line and on-line situations.

There is also benefit in performing inspection activities on SISequipment during normal operation of the process to detect anypotential problem creating situations that might be developing.Guidance in what to look for, how often to inspect, and what to dowhen a condition is observed that could lead to a failure willenhance the safety integrity of the SIF.

Edition:

02

Published:

06/17/2002

Number of Pages:

222

File Size:

1 file , 960 KB