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Flange gasket effecting compressed air flow

Flange gasket effecting compressed air flow

Flange gasket effecting compressed air flow

(OP)
A 1.5" pipe has compressed air flowing through by a 100hp compressor rated at 4cfm/hp.  A 1/16" gasket is protruding into the bore 1/8", so the diameter at that point is 1.25".  I am trying to determine the loss of $ annually for this protrusion of the gasket, assuming the compressor runs 8760 hours/year.  Also assume pressure before the flange at 100psi.  I believe this $ amount to be fairly negligible, but am unsure to solve this.  Thanks in advance.

RE: Flange gasket effecting compressed air flow

You should be able to model the gasket protrusion as a thin-plate orifice to find the pressure-drop across it.  Once you know the pressure drop you can calculate the pumping power lost using equations similar to below.

hp = 144*N*P*V*n/(33,000*(n-1))*((P2/P)^((n-1)/(N*n))-1) where:
N = # of compressor stages,
P = atmospheric pressure (psi),
P2 = absolute final pressure (psi),
V = volumetric flowrate (scfm),
n = exponent of compression curve (1.41 for adiabatic)


This is from Machinery's Handbook, 27th Ed.

If you calculate hp using P2 as pressure before the obstruction, then again with P2 as pressure after the obstruction, then subtract the values to find the power difference.

Then divide by your efficiency (.8-.9 for electric drive) to find total power consumption.  Multiply by $ per power unit to find cost.

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