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WORKED EXAMPLES FOR LIQUIDS

Given a liquid relief valve of d_o = 10mm at a set pressure p_t = 8 bar gauge.
Question:

What will be its discharge of water sg = 1 in kg/hr at an accumulation of 10% with a discharge coefficient of c_f10 = 0.45?
What will be its flow in litres/min.?

from (2a)

w_f=40\cdot 100\cdot 0.45\cdot \sqrt{1.1\cdot 8}

=5339.7\;\;\;\;\;\;\;\;\;\;(kg/hr)

and

v_f=\frac{2}{3\cdot 40}\cdot 5339.7

=89\;\;\;\;\;\;\;\;\;\;(litres/min)

Given a mineral oil of specific gravity sg = 0.89, and it is desired to relieve 35 litres/min at a flowing pressure of 30 lb/in².
Question:

What is the minimum size of safety valve seat assuming the valve can work at 25% set pressure accumulation, and has a coefficient of discharge of 0.6?

A flowing pressure of 30 lb/in² corresponds to;

=\frac{30}{14.5}=2.069\;\;\;\;\;\;\;\;\;\;(bar gauge)

Hence, set pressure p_t

=\frac{2.069}{1.25}=1.665\;\;\;\;\;\;\;\;\;\;(bar gauge)

From (5)

=d_o\geq \sqrt{\frac{1.3416\cdot 35\cdot \sqrt{0.89}}{0.6\cdot\sqrt{1.665}}}\;\;\;\;\;\;\;\;\;\;(mm)

\geq 7.56\;\;\;\;\;\;\;\;\;\;(mm)