The pressure equivalent to the force (in Newtons) per unit of surface area (m2).
In the case of tubing, this is an important figure as it will determined the mechanical forces which the tubing installation is subjected to.
In the international system, the pressure unit id the Pascal, however this unit is very small, and so other units are often used, such as bars or the millimetres of a water column.
1 atm = 1 bar = 10,000 mm H2O = 750 mm Hg = 100,000 Pa
It must be remembered that in normal conditions, working pressure is equivalent to 1 atmosphere (owing to the layer of air which forms the Earth’s atmosphere), which means that it will always be necessary to determine as to whether the pressure values are relative or absolute. One also has to take into account that work may be undertaken in a depression – with suction - i.e. applying less air pressure, which leads to pressure values below those of atmospheric values.