Parallel Flow Paths; Series Flow Paths - Emerson Daniel 700 Series Technical Manual

Technical Guide
DAN-LIQ-TG-44-rev0813
November 2013

Parallel Flow Paths

An inherent characteristic of liquids is that they will always take the path of least resistance. Thus, when two parallel flow paths
offer different resistances, the pressure will increase only to the amount required to take the easier path.
In Figure 1-5 the oil has three possible flow paths. Since valve A opens at 10 psi, the oil will go that way and pressure will build
up to only 10 psi. Should flow be blocked beyond A, pressure would build up to 20 psi, then oil would flow through B. There
would be no flow through C unless the path through valve B should also become blocked.

Series Flow Paths

When resistances to flow are connected in a series, the pressures add up. Figure 1-6 shows the same valves as Figure 1-5,
but connected in a series. Pressure gauges placed in the lines indicate the pressure normally required to open each valve
plus back pressure from the valves down-stream. The pressure at the pump is the sum of the pressures required to open the
individual valves.
The oil can choose 3 paths.
It first chooses path "A" because
only 10 psi is required . A pressure
gauge at the pump will read 10 psi.
PARALLEL FLOW PATHS
PUMP
A
10 psi opens valve A
B
20 psi opens valve B
C
30 psi opens valve C
Figure 1-5
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