Pressure Vessel is briefly is a storage device, which could store fluids above 15PSI.
These are generally designed based on ASME codes, if vessel does not have heating mechanism(unlike boilers), it can be designed by ASME Section VIII.
For PVs with pressure 15PSI to 3000PSI, division 1 is used, for pressures between 3000PSI to 10000PSI, division 2 and division 3 for above 10000PSI
Below is the pressure vessel size and selection formula
PUMP DUTY SELECTED = 2.99 M3/HR @ 48 MTR
Pressure Vessel Volume V can be calculated from the following formula
V= Q.1000. (1+Cut-in) + Dp. 1
4 nmax.Dp k
Where
V = Tank Volume (Litres)
Q = Flow (m3/hr) = 2.99 m3/hr
Dp = Difference between cut-in & cut-out = 3.2 bar
nmax = max. Number of starts per hour = 15
k = Constant for tank pre-charge pressure = 0.9
maximum cut-in = 2.3 bar
maximum cut-out = 5.5 bar
Therefore V = 2.99 x 1000 x (1+2.3) + 3.2 . 1
4 x 15 x 3.2 0.9
= 101.2 LTR
Therefore Pressure vessel selected is 130 L capacity.