Intermittent Factors For Industrial Applications 1

[ThePunisher]

I commonly observe that in most oil and gas projects, their associated design load calculations are tabulated in kW, kVArs in such a manner that all continuous, intermittent and standby loads are summed up separately and then applied with 1.00, 0.30, 0.10 diversity factors for continuous, intermittent and standby respectively. Then,

maximum running load = continuous loads*(1.0) + intermittent loads*(0.30)

Peak Load = continuous load*(1.0) + intermittent loads*(0.30) + standby loads*(0.10)

My questions:

1. Are the diversity factors: 0.30(for intermittent), 0.10 (for standby) an industry practice?

2. Is there an industry standard that specifies diversity factors for intermittent and standby loads?

 

[rcw retired EE]

Interesting concept. One I had not seen before (that I remember). We apply a demand factor to each load based on our knowledge of how it will be used: 100% or 80% for continuous loads, factors of 10% to 80% for intermittant and 0%-20% for standby. Then we add a safety factor or growth margin to the total. Dual pumps are either listed as one at 100% and one at 0% or both at 50%-75% depending on the pump curve.

I am not aware of any standard. Lots of discussion on this site before. Conclusion was to make sure your calculation basis is reasonable and that you could defend it if challenged.

 

[davidbeach]

Keeping in mind that "could defend it if challenged" could be after you've been sworn in as a witness in a court case.

 

[waross]

I would be more comfortable doing an assessment of the loads first. The loads could then be assigned a factor of 1, 0.3 or 0.1 depending on the nature of the loads.
Loads in the 0.3 group may then be arbitrarily called intermittent and loads in the 0.1 group may be arbitrarily called standby.
The second step is to take a step back and look at the big picture. If process requirements require several motors in the "standby" group to operate simultaneously, then this must be factored in in some way. Consider ten motors running 10% of the time at random times versus ten motor running 10% of the time, but all at the same time.



Bill
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"Why not the best?"
Jimmy Carter