3 replies to this topic

[jamy86]

For checking flare header adequacy after proposed modifications in electrical supply distribution in a refinery, what philosophy is generally considered?

 

For example:

If suppose power to a unit is going via a substation (SS), and if this SS trips/ fails, then flare load equivalent to power failure case of that unit will go to flare header.

 

Multiple SS failure will occur if the power supply to this fails and then multiple units will be affected, and all respective flare loads will go to the flare.

 

My question is if we are providing multiple power input sources to substations, can multiple SS failure be considered as a case for flare header adequacy checking. Should total refinery blackout (main power source failure) be considered as a case even after multiple power sources (refinery internal power generation and external power supply) are provided to SS's.

 

 

Are there any standards for this?

[Bobby Strain]

In my experience, refineries generally have solenoid devices to trip the source of potential flare loads on power failure. Even so, the flare must have sufficient capacity to handle the two (or more) greatest relief flows. So, the answer to your question cannot be offered with any reliability.

 

Bobby

[fallah]

 

My question is if we are providing multiple power input sources to substations, can multiple SS failure be considered as a case for flare header adequacy checking. Should total refinery blackout (main power source failure) be considered as a case even after multiple power sources (refinery internal power generation and external power supply) are provided to SS's.

 

 

Are there any standards for this?

 

Jamy,

 

Individual SS power failure as local power failures and also simultaneous power failures among them should be evaluated as credible scenarios of power failures for checking of flare capacity adequacy.

 

And yes, total refinery blackout; if it's credible; should be considered as a case for checking flare capacity adequacy.

 

The main point is having adequate flare capacity for highest relief load among all above credible cases relevant to power failure cases.

[gegio1960]

jamy,

everything is managed thru probabilities of failure.

the basic concept is:

- in order to obtain a certain load release, a series of events shall happen (tree of failure)

- each event is associated with its own probability of failure

- the combination of the single probabilities will produce a probability for the load release scenario

- if the combined probability is below a certain treshold (eg 1 probability in 1 million years) the scenario is not credible

- the addition of other independent power sources will decrease the probability of some failures.

in parallel, dynamic simulation studies can be made to better identify, and possibly reduce, the peak load rate of the controlling scenarios

good luck!