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Posts Tagged ‘Riyaz Ali’

Approaches to Partial Stroke Testing Safety Valves

Posted in Final Control Element, Safety on Wednesday, October 23rd, 2019. No comments yet
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The safety valve within a safety instrumented function (SIF) must be tested regularly to help assure proper operation in the event of a safety demand. Operators usually perform an offline full stroke test during a scheduled shutdown because of the impact of this test on the process. But when a SIF (a.k.a. safety loop) requires […]

Simplifying Safety Valve Proof Testing

Posted in Safety on Wednesday, December 19th, 2018. No comments yet
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A safety instrumented function (SIF) within a safety instrumented system (SIS) consists of a sensor, logic solver, and final element. As part of the IEC 61511 global safety standard, these elements within the SIF must be tested during the operational phase of the safety lifecycle. Of the 3 elements, the final control element, typically a […]

Partial Stroke Test for Final Elements—Diagnostic Coverage Factors

Posted in Final Control Element, Safety on Thursday, December 13th, 2018. No comments yet
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Author: Riyaz Ali Partial stroke test is one of the viable means to check mechanical integrity of Final Element of Safety Instrumented Function (SIF) loop. Generally, end users struggle on question of credit of PST for improvement in SIL (Safety Integrity Level). IEC 61508 and IEC 61511 define diagnostic coverage factors (DCF), but do not […]

Low-Bleed or Standard Relays for Control Valves?

Posted in Controllers & Positioners, Final Control Element on Tuesday, January 2nd, 2018. No comments yet
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Happy New Year everyone! I hope your holidays helped to recharge your batteries and get you off to a great start for 2018. I saw this exchange in my email over the holidays about the effects of using low-bleed relays with Fisher DVC6200 digital valve controllers for control applications as compared to standard relays. This […]

Selection Criteria in Compressor Anti-Surge Valves

Posted in Final Control Element on Friday, August 18th, 2017. No comments yet
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Some of the most consistently popular posts here on the blog involve compressor anti-surge control. It’s a condition in centrifugal and axial compressors where a flow reversal condition can occur. Wikipedia defines centrifugal compressor surge as: …the point at which the compressor cannot add enough energy to overcome the system resistance or backpressure.[26] This causes […]