Microhidráulica Industrial

# Two Restrictors

The chart on the adjacent page solves for the absolute pressure between two orifices as a percentage of the supply pressure. To solve a problem, simply follow the graph line corresponding to the Lohm ratio, L1/L2 , until it crosses the overall pressure ratio, P1/P3. Then read horizontally across to the left hand scale to obtain the value of P2 as a percentage of the upstream absolute pressure, P1.

EXAMPLE: Find the intermediate pressure between two restrictors with an upstream pressure 72 psia, exhausting to atmosphere at 14.7 psia.

 L1 = 2000 Lo. L2 = 500 Lo.

Calculate the Lohm ratio: L1/L2 = 2000/500 = 4.0

Calculate the overall pressure ratio: P1/P3 = 72.0/14.7 = 4.9

Read 28% from left hand scale of graph.

The upstream pressure is known, thus:

 P2 = 0.28 x 72.0 = 20 psia  The chart on the adjacent page solves for the absolute pressure between two orifices as a percentage of the supply pressure. To solve a problem, simply follow the graph line corresponding to the Lohm ratio, L1/L2 , until it crosses the overall pressure ratio, P1/P3. Then read horizontally across to the left hand scale to obtain the value of P2 as a percentage of the upstream absolute pressure, P1.

EXAMPLE: Find the intermediate pressure between two restrictors with an upstream pressure 72 psia, exhausting to atmosphere at 14.7 psia.

 L1 = 2000 Lo. L2 = 500 Lo.

Calculate the Lohm ratio: L1/L2 = 2000/500 = 4.0

Calculate the overall pressure ratio: P1/P3 = 72.0/14.7 = 4.9

Read 28% from left hand scale of graph.

The upstream pressure is known, thus:

 P2 = 0.28 x 72.0 = 20 psia  