Manifolds
are required to fill cylinders with gases or liquids after they are
processed and produced in gas plants. Usually made of metal, a manifold
comprises a metal line of pipes through which numerous gas cylinders can be
connected and filled with gas simultaneously. An essential equipment,
manifolds are widely used in gas plants. They help in connecting several
cylinders to a common gas supply line and thereby providing a larger
continuous supply of gas. For filling high pressure oxygen or any other gas
to cylinders, high pressure filling manifold is required. Manifolds usually
comprise a high pressure isolation valve with pigtail connection with
individual valve. Safety relief valves and pressure gauge With the growing
demand for safety and performance for instrumentation systems in gas, oil,
chemical and other process plants, lots of high-integrity designs of
manifolds are available.
Manifold configurations
To make the user use most of the allotted space for the system, two basic
configurations are available-single row and double row.
- Single row configuration: Here all the connections to the manifold of
cylinder is done in a continuous straight line.
- Double row configuration: Here the connections to the manifold occur
on either side of the common line. It has two equal rows of cylinders
with a common pipe running between the two rows. It requires support
from either the ground up or suspended from above.
Components of Filling Manifolds
For filling high-pressure oxygen gas to cylinders, manifolds are required.
Manifolds consist of:
- High Pressure Isolation Valve
- Pigtail connection with individual Valve
- Pressure Gauge
- Safety Relief Valve
- Station valves
- Check valves
Station valves are required to isolate individual cylinders on a
manifold from service. They are mostly recommended for most laboratory
applications. They are always useful in the event of a leaking pigtail or a
defective check valve. It is very essential that station valves used in high
purity gas service maintain gas purity. There are two types of
pigtails-rigid pigtail and flexible pigtail-used to connect cylinders to the
manifold header.
It is to be noted that either rigid pigtails or flexible pigtails are
recommended for helium and hydrogen because these gases have the property of
diffusing. Check valves on the cylinder end of each pigtail should always be
fixed on filling manifolds used for flammable, toxic, or corrosive gases. In
some cases purge assemblies are installed. Many applications require that
gas always be supplied to the process. The flow can not be shut down to
replace empty cylinders. In such a case a changeover manifold is the
solution. For optimizing the performance of manifolds, never mix gases on a
manifold. The same manifold should be connected to only one type of gas.
Advantages of Gas Manifold
- Manifolds simplify piping.
- They improve appearance.
- They reduce space requirements.
- They can be configured with any desired combination of inlets,
outlets, or flow circuitry.
- Manifolds connect two or more cylinders of gas together.
- They increase the supply volume of gas available to provide a
continuous flow when one cylinder is not sufficient and other bulk
supply is not practical.
- Manifolds are also used when a single cylinder of gas is not capable
of supplying the required flow rate required by a process.
Gas Manifold
