Orifice v Reduced Pipe ID to control flow rate
Orifice v Reduced Pipe ID to control flow rate
(OP)
Looking for a bit of advice, and confirmation that I am on the right path.
I need to take a feed off oil system running at 10 bar, which will pass oil through a couple of devices before being returned to the sump above the oil line. Flow in the branch line to be between 2 and 4 l/min.
I started off looking at an orifice using:-
Q=C*A*sqrt(2*(P1-P2)/p)
Where C = Orifice flow coefficient (used 0.7 as a value), A = cross sectional area of the orifice, P1 = upstream pressure, P2 = downstream pressure, and p = density
ref: Wikipedia www.en.wikipedia.org/wiki/Orifice_plate
This gives me an orifice diameter of 1.6mm for a 3.84 l/min flow rate. The orifice is a bit on the small side and may become blocked, if a make the orifice for example 3mm diameter then the flow rate becomes too big.
Pressure after the orifice will be atmospheric pressure (P1 - P2 = 9 bar) if orifice is at the end of the branch, the oil is returned above the oil line, and the gearbox is vented?
If I increased the ID to 3mm but increased the length to give me the 9 bar pressure drop, would I get the flow I'm looking for?
I need to take a feed off oil system running at 10 bar, which will pass oil through a couple of devices before being returned to the sump above the oil line. Flow in the branch line to be between 2 and 4 l/min.
I started off looking at an orifice using:-
Q=C*A*sqrt(2*(P1-P2)/p)
Where C = Orifice flow coefficient (used 0.7 as a value), A = cross sectional area of the orifice, P1 = upstream pressure, P2 = downstream pressure, and p = density
ref: Wikipedia www.en.wikipedia.org/wiki/Orifice_plate
This gives me an orifice diameter of 1.6mm for a 3.84 l/min flow rate. The orifice is a bit on the small side and may become blocked, if a make the orifice for example 3mm diameter then the flow rate becomes too big.
Pressure after the orifice will be atmospheric pressure (P1 - P2 = 9 bar) if orifice is at the end of the branch, the oil is returned above the oil line, and the gearbox is vented?
If I increased the ID to 3mm but increased the length to give me the 9 bar pressure drop, would I get the flow I'm looking for?





RE: Orifice v Reduced Pipe ID to control flow rate
Yes, you could use a larger capillary to get the same pressure drop and flow rate, but as you increase the diameter, the capillary gets longer pretty fast.
Mike Halloran
Pembroke Pines, FL, USA
RE: Orifice v Reduced Pipe ID to control flow rate
So I see, just done some calcs for 3mm and 2mm tube at different oil viscosities.
Any thoughts on multiple orifices in sequence?
I did calculations using the equation in my first post where the downstream pressure of orifice 1 is the upstream pressure of orifice 2 etc. Three orifices at 2mm diameter would get me from 10 bar down to 1, with a flow rate of 3.47 l/min.
Am I missing something?
Matt
RE: Orifice v Reduced Pipe ID to control flow rate
RE: Orifice v Reduced Pipe ID to control flow rate
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I've attempted to produce, in a former life, a similar product to their viscojet...we came close, and spent quite a bit of money and time to get there. I don't much care for their service nor price when volumes are <10,000 units, but they do produce good parts.
RE: Orifice v Reduced Pipe ID to control flow rate
I'll have a look at the Lee company literature.
RE: Orifice v Reduced Pipe ID to control flow rate