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normal flow rate versus maximum flow rate in pipeline

normal flow rate versus maximum flow rate in pipeline

(OP)
Hi everyone;
we are going to transfer chemical from storage tank trough pump and pipe line to another plant.maximum flowrate is dictated by downstream plant and it is clear. i need to define normal flowrate because i need it for calculation and also to put it in equipment and instrumentation datasheet.i am wondering if anybody could give me an advice to define normal flowrate.
best regards

RE: normal flow rate versus maximum flow rate in pipeline

You seem to be confusing boundary conditions with physical limitations. If the maximum flow rate is based on the downstream plant, it has very little to do with your piping and pumps--e.g., you might have operational reasons to design the pipe big enough for many times the maximum delivery flow rate due to friction considerations or pipe availability.

"Normal flow rate" dhas everything to do with your piping and pumps. You need to determine the nominal flow based on plant input and the capacity of the processing equipment and then design your take-away pipe to accommodate that flow rate without approaching erosional velocity in the pipe, running away from your suction head on the pump, and being in an economical region of the pump curve. You need to do this while being able to accommodate changing needs of the downstream plant and changing plant inflow.

What I'm trying to say is that you need to define "normal" based on the realities of the upstream flows and processes. You also need to define a "maximum" based on physical limitations of the selected equipment that should be greater than the "maximum" defined by the boundary conditions.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

RE: normal flow rate versus maximum flow rate in pipeline

I would tend to think that there must be external factors that define the "normal" flow rate in the same way as the "maximum" flow rate has been determined (i.e. the downstream plant demand). In case this is something really unique and there is no "normal" flow case for the downstream facility, then it is purely up to the designer to specify this value - given that the same system must be able to meet the maximum flow conditions, as well as to be able to manage the existing/available storage constraints, product batching schedule, etc. Like David says, this has everything to do with your piping and pumps (I would add storage tanks and pumping schedules, if any) - both scenarios need to be fully workable and economical, while meeting the the given constraints and requirements.

Dejan IVANOVIC
Process Engineer, MSChE

RE: normal flow rate versus maximum flow rate in pipeline

Normal means what the system does "normally", say more than 80-90% of the time.

The normal flowrate is a balance between how much you need to transfer in a certain time period.

If you need a lot in one go ( say 1 hour) then it is quite big, but if you can spread that out "normally" over say 8 hours it is much smaller.

SO if your maximum is say 100m3/hr, your "normal" could be anywhere from 1 to 99 m3/hr.

Each system is different - there is no magic rule.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: normal flow rate versus maximum flow rate in pipeline

Normal flowrate might also be defined as the flowrate needed to fill the tank(s) within the average alloted time to do so.

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