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[invssse]

Dear Experts,

 

In API 521 SIXTH EDITION (JANUARY 2014)  4.4.15.1 (PP.58) there is a statement for Utility Failure.

 

"An evaluation of the effect of overpressure that is attributable to the loss of a particular utility service should include the chain of developments that can occur and the reaction time involved. In situations in which the equipment fails but operates in parallel with equipment that has a different energy source, operating credit may be taken for the unaffected and functioning equipment to the extent that service is maintained."

 

It's easy to say electric power and steam are different energy sources to drive a pump. but are they different energy sources at the following circumstances?

 

1.  Can the power circuits from two different substations be taken as two different energy sources?

2.  Can credit be taken for dual electrical power supply? That is, when one of the electrical circuit fails,  the other circuit will switch to supply power through an instrument or device.  

 

Thanks.

[Bobby Strain]

1. No

2. No