National standards and persons in the gas suppression industry use many words followed by "pressure", Storage pressure, Downstream pressure, Working pressure, Discharge pressure and the least understood Developed pressure.
Working Pressure
Working pressure is the pressure in the pipe work and is the same as downstream pressure in a lot of cases. This is an estimated pressure for inert agents as it varies over time and distance.
Downstream Pressure
Downstream pressure is accepted to be the pressure of the gas in the distribution pipe (after the pressure reducer, if fitted).
Discharge Pressure
Discharge pressure is the pressure as it leaves the cylinder. In many cases this the same as the storage pressure but in several newer systems pressure reduction is done in the valve so now discharge pressure will be much lower than the storage pressure.
Storage Pressure
Storage pressure is the pressure of the gas in the cylinder at room temperature (20 - 21 oC).
Developed Pressure
Developed pressure is the pressure of the gas at maximum working temperature, assumed to be 50 oC. The pressure of all gases increases as temperature increases. As an example 200 Bar Inergen at 20 oC becomes 235 Bar at 50 oC.
This is important in Africa as atmospheric temperatures can reach high levels, therefore pipe and fittings must be able to withstand the additional pressures brought about by high temperatures.
Pipe and fitting pressure ratings are therefore calculated at developed pressure.