A multiple header for interconnection of gas sources with distribution points.
Individual cylinders cannot supply high rates of gas flow, particularly for continuous operation over long periods of time. Manifolding of cylinders is one answer to this problem. A reasonably large volume of gas is provided by this means, and it can be discharged at a moderately rapid rate. Manifolds are available as portable or stationary units.
Portable. Portable manifolds are useful where moderate volumes of gas are required for jobs of a nonrepetitive nature, either in the shop or in the field. Two portable systems are commonly used. Both permit the manifolded cylinders to be located near the point of use. In one type of portable manifold, Ts are connected to the individual cylinder valves, and leads (pigtails) successively join the Ts together. The gas from each cylinder passes through the T, into the main gas stream, and finally, to a regulator that serves the entire group of cylinders.
In the second type of portable manifold, the cylinders are connected by individual cylinder leads (pigtails) to a common coupler block that is connected to a pressure reducing regulator.
Stationary. Stationary manifolds, Figure C- 12, are installed in shops or plants where larger volumes of gas are required. This type of manifold feeds a pipe- line system distributing the gas to various stations throughout the plant. This arrangement allows many operators to work from a common pipeline system without interruption. Alternatively, it may supply large automatic torch brazing or oxygen cutting operations.
This type of manifold consists of an adequately supported high-pressure header to which a number of cylinders are connected by means of pigtails. One or more permanently mounted regulators reduce the pressure and regulate the flow of gas from the manifold into the plant piping system.
An important protective device for the fuel gas pipeline system is the hydraulic seal, or hydraulic flashback arrester, which keeps flashback originating at a station from passing further into the system. It consists of a small pressure vessel partly filled with water through which the gas supply flows. The gas continues through the space above the water level and through the vessel head to the station regulator. A flashback of high pressure backup will set off the relief valve to the vessel head, which will vent the pressure to the outside atmosphere. A check valve prevents the water from backing up into the line.
Regulations and Safe Practices for Manifolds and Pipelines.
The rules and regulations set forth in the current issue of NFP A51, Standard for the Installation and Operation of Oxyfiel Gas Systems for Welding and Cutting, as recommended by the National Fire Protection Association, govern the installation of oxygen and acetylene manifolds and pipelines. In all cases, manifolds should be obtained from reliable suppliers and
installed by personnel familiar with proper construction and installation of manifolds and pipelines.