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Topic Title: Implementation of SIL a trip functions.
Topic Summary: How should SIL 'a' classified trip functions be implemented?
Created On: 23 March 2010 11:41 AM
Status: Read Only
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 23 March 2010 11:41 AM
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Posts: 1
Joined: 19 June 2003

Dear All,

In normal refinery, chemical process applications, how should trip functions classified as SIL 'a' or 'not rated' be implemented?

1. Can the trip function be 'deleted' and considered to be 'not required' whilst retaining the DCS control loop?

2. Should it be retained as an 'independent trip function' and implemented within the DCS?

Appreciate some advice please.
 14 April 2010 07:38 PM
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Posts: 90
Joined: 26 February 2002

On an ALARP basis you should not delete, but do not need to jump through SIL hoops in terms of substantiation of design/installation etc.; simply maintain on 'good practice' basis.

HTDearden CEng
Consulting Engineer

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