8
SYSTEM PERFORMANCE
Rev C
Pressure Drop Through Obstructions
Every obstruction or fitting in the line will cause a small amount of
pressure drop. We recommend keeping connections or obstructions in the
permeate line to a minimum. These include items such as tees, valves,
step-down adapters, elbows, compression fittings, etc.
We recommend subtracting 1/2 psi (0.034 bar) of pressure drop per fitting
used.
Figure 5
NOTE:
Do not use 1/4-inch OD tubing anwhere in the installation,
including runs to ice makers. Larger tubing diameters produce less
pressure drop and increase system performance.
EXAMPLE:
Q:
A Merlin will be installed with inlet conditions that will produce 0.5
gpm, based on Table 1. The installation requires 20 ft of permeate
tubing. Find the tubing pressure drop.
A:
Tubing pressure drop for this installation will be 0.11 psi/ft of
3/8-inch tubing or 0.02 psi/ft of 1/2-inch tubing according to
Figure 4. Because 20 ft of tubing will be used, the total tubing
pressure drop is:
For 3/8-inch tubing: 0.11 psi/ft X 20 ft = 2.2 psi tubing pressure
drop
For 1/2-inch tubing: 0.02 psi/10 ft X 20 ft = 0.4 psi tubing
pressure drop
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Tee
Elbow
Stepdown
Fitting
Compression
Fitting
Valve