Gas Suppression Systems - Manifold Pressures

The following are extracts from SANS 306:4 and SANS 14520:1

SANS 306:4 19.1

Valves and manifolds for high pressure systems shall be hydraulically tested to a minimum working pressure of 190 bar.

CO₂ systems storage pressure at 20 °C is 57 bar but the manifold has to be pressure tested to 190 bar to cater for developed pressure.

SANS 14520:1 6.3.1.6

The manifolds to the container and valve assembly shall be hydraulically tested by the manufacturer to a minimum pressure of 1,5 times maximum working pressure (see 3.17), or as required by the appropriate national standards.

The word “shall” referenced above means it is a compulsory requirement to test manifolds due to the dangers they present. It is the duty of the supplier, the installer, the consultant and the inspector to ensure this takes place.

A further problem faces the industry with constant flow valves being introduced by gas system manufacturers. It is claimed that the valve, although controlling 300 bar pressure, only releases the gas at 42 bar therefore the pressure exerted on the manifold will be around 60-70 bar (at 50 °C) but the SANS and ISO standard rate the manifold by the pressure in the container.

Furthermore

3.17 maximum working pressure is the equilibrium pressure within a container at the maximum working temperature.

What is overlooked here is the word “maximum”. This is referencing “the equilibrium pressure within a container at the maximum working temperature”. This temperature being 50 °C .

With extra temperature comes extra pressure. This has to be catered for in the design of the manifold because in Africa we can be subject to these temperatures and this provides the safety factor we should all use.

Here are the developed pressures for the common gasses in South Africa and the pressure that manifolds should be tested to.

By utilising a lower rated manifold for these systems is fine until something goes wrong. What if the valve fails and exerts the full 300 bar onto a manifold designed to withhold 60 bar? This is a question posed to the ISO committee for attention.

Who will take the punch if this happens, the local supplier who manufactures the manifold or the original supplier?

Come guys we all owe it to the industry. Do the right thing!!