In a wide variety of applications gases from cylinders or insulated liquid tanks are piped, via static systems, to the point(s) of use. From a safety perspective this can eliminate cylinders in a populated workspace, avoid the requirement for difficult cylinder handling operations (e.g. up and down stairs) and generally reduce the number of cylinder handling movements, along with the number of persons involved in those movements.
Practically, such piped systems dramatically reduce the inconvenience of running out of gas mid-way though a task. However, in order to achieve these benefits safely it is essential that the system(s) should be correctly designed, installed and maintained inline with relevant legislation. It is also essential that the operators of the system(s) are correctly trained.
The Two Parts of a Piped System
For convenience, a piped system may be divided into two main parts, the supply system and the distribution system.
The Supply System
The ‘supply’ side is that part of the installation from the cylinder(s) to the main pressure regulator. This must be gas compatible and capable of withstanding cylinder fill-pressures. The supply may be from a single cylinder that is attached to the piped system via a flexible hose or ‘pigtail’ or from a ‘bank’ of two cylinders that feed gas into a changeover panel.
The changeover system may either be a manually operated system or an auto changeover system. Ideally, this part of the system should either be sited outdoors or in a bespoke, well-ventilated manifold room and the cylinders in the manifold area (cage or housing) should be kept in accordance with the relevant industry Codes of Practice.
Each pigtail should be fitted with a non-return or isolating valve. From the pigtail(s) the header is fed, which may incorporate purge points, isolation valves, bursting discs, heaters and vaporisers etc.
The Distribution System
On a single cylinder system the pressure in the distribution system is controlled by a main regulator (typically two-stage unless the cylinder supply is low pressure from a liquefied gas supply e.g. propane). The main regulator is carried on a mounting block and should be positioned in such a way that the HP (high pressure) and LP (low pressure) gauges are visible to the operator.
The part of the system after the main regulator is referred to as the distribution system. The specific components for this are determined by the service gas. Certain components are, however, essential. For example, the distribution system must be protected against over-pressurisation resulting from a regulator malfunction or other abnormal circumstance.
Changeover systems will have two ‘banks’ of cylinders connected to the supply system; one ‘in use’ and the other ‘on reserve’. Changeover between these can be achieved by a variety of means depending upon the design. For example, if the regulators on each bank are preset to slightly different outlet pressures; as one side (bank) empties the other will automatically take over. Alternatively, this can also be achieved by having a manually or automatically operated changeover valve. Such equipment may be linked to a remote alarm, highlighting to the operator that a changeover has occurred and the ‘empty’ cylinder(s) need to be replaced and removed.
Piped System Installation and Operation
It is essential that piped systems are installed by competent installers (refer to the BCGA website for guidance) in accordance with BCGA Codes of Practice and UK legislation.
The installer should commission the system and provide handover documentation that includes operating procedures for the system.
System Operators
It is imperative that operators are trained in the safe operation of their particular piped system and are aware of the consequences of not following approved standard operating procedures.
They need to undertake a weekly inspection of their system (in-line with Code of Practice 4 issued by the British Compressed Gases Association) and recognise the need to report any faults immediately to their supervisor.
Piped System Regulation
Fixed piped systems usually fall under the scope of The Pressure Systems Safety Regulations 2000 and operators must not use a piped system until a Written Scheme of Examination (WSE) has been drawn up by a Competent Person.
The system’s WSE will also detail how often – and how – the fixed gas system must be formally inspected by a Competent Person. It you use piped systems please check that you have a the correct WSE’s in place as well as standard operating procedures. Ensure that all operators have been correctly trained.
Piped System Operator Training
Our range of compressed gas training courses includes options containing information of fixed gas supply systems / manifolds. If you require assistance, please contact us.
