What is a gas cylinder manifold? Components, cylinder count and safe operation

A single 45kg cylinder is enough for a small eatery, but large restaurant kitchens, canteens and production workshops usually need several cylinders running at the same time. In that case, the cylinders are connected into a gas cylinder manifold to supply gas continuously at a sufficient flow rate. Below are its components, how to work out the number of cylinders and how to operate it safely.

What is a gas cylinder manifold?

It is an assembly of several LPG cylinders, usually 45kg cylinders, connected to a common header and then through a regulator into the pipework leading to the burners. A manifold is usually split into two groups: an in-use group and a standby group. The articles installing gas cylinders in restaurants and gas for industrial kitchens only touched on this option.

Common components

• Gas cylinders: 45kg cylinders with the same type of valve, standing upright, held by a rack or chain.
• Cylinder valves of the right type that seal properly, for example the LPG cylinder handwheel valve.
• Flexible connecting hoses: connect each cylinder valve to the header; depending on the system, non-return valves allow a cylinder to be removed without gas escaping from the header.
• A metal header that collects gas from the cylinders, together with branch isolation valves and a main valve to isolate each group or shut off the whole system.
• Regulator, single- or two-stage, reducing the pressure to a level that suits the burners.
• Pressure gauges to monitor the gas supply.
• Automatic changeover device (depending on the system): switches automatically to the standby group when the pressure in the in-use group drops.

Why use a cylinder manifold?

Gas in the cylinder is liquid and must vaporise before it can be supplied to the stove; this process draws heat from the cylinder shell and its surroundings. Each cylinder can only deliver a limited amount of vapour; draw more than that and the pressure drops, the flame weakens, the cylinder gets cold and may frost over. Connecting several cylinders shares the load, providing enough vapour for peak hours. A manifold also allows a group of empty cylinders to be changed without turning off the stoves.

How to work out the number of cylinders

The exact figure is calculated by the designer; the general method is as follows:

1. List the burners, such as restaurant wok burners, and the gas consumption shown on the label of each appliance.
2. Determine the maximum flow rate when several appliances run at the same time during peak hours.
3. Estimate the vaporisation capacity of each cylinder under actual conditions, which depends on the ambient temperature, the amount of gas left and the duration of continuous draw.
4. Calculate the number of cylinders for the in-use group, adding a safety margin; the standby group is usually the same size.
5. Compare daily consumption with the gas delivery schedule to work out the number of reserve cylinders.

Siting, design and installation

The manifold is placed in a separate, well-ventilated area, away from the cooking area. LPG is heavier than air, so the cylinder area must be ventilated at floor level and must not be in a basement or a low-lying spot — a difference from natural gas, see LPG vs LNG: how do they differ. Safety distances, the amount of gas stored and fire protection equipment follow current regulations.

A cylinder manifold must be designed, installed, leak tested and commissioned by a qualified installer. VietnhatGas supplies 45kg cylinders and cylinder valves to distributing dealers and does not install systems.

Operation and periodic checks

• Changing cylinders: close the branch valve and the valves of the empty cylinders, remove them, check the seals, fit full cylinders, open the valves slowly and test for leaks with soapy water, never with a flame.
• Only accept cylinders within their inspection date, with the cylinder and valve intact — see periodic inspection.
• Check hoses, valves and joints regularly; carry out maintenance according to the installer’s schedule.
• If you smell gas: close the main valve, do not switch electrical equipment on or off, ventilate the area, leave and call the fire service on 114 from a safe place.

Frequently asked questions

Written by the VietnhatGas technical and sales team — a batch manufacturer of LPG cylinders. This content is for reference; regulations and standards may change, so please check the current texts.