Medium Pressure Gas Service (MP)
Service pressure is based on the pressure that the local distribution network operates at and is usually: Medium Pressure: (>75mbar<=2bar). Other pressure tiers are: Low Pressure: (0<=75mbar), Intermediate Pressure: (>2bar<=7bar) and High Pressure: (>7bar).
Medium Pressure Gas Meters
MP meters are effectively the same meters that are installed for low pressure and are based on their capacity, measured in Standard cubic meters per hour (SCMH). A U6 meter delivers 6 m³/hr, a U25 delivers 25 m³/hr, and so on.
The difference is MP meters need to be adapted in order to manage the increased pressure from the main. This includes a regulator, the means by which pressure in the downstream system is controlled. An MP regulator works with Maximum Operating Pressure (MOP) upstream exceeding 75 mbar but not exceeding 2 bar whilst maintaining a controlled outlet pressure within pre-determined limits of accuracy under flow conditions and ensures that the downstream pressure is kept within acceptable limits under no-flow conditions. This may include integral safety devices, for example slam-shut valves (when it is defined as a Pressure Regulating Installation (PRI).
Gas Service Pipes
Gas services are small diameter pipes, usually up to 63mm (2.48inches) diameter which are connected to low, medium or intermediate pressure mains and take gas into homes. commercial or industrial buildings. A gas service regulator is connected to the end of the service pipe before the gas meter to reduce the gas pressure to supply gas appliances installed in the premises. In the case of Medium Pressure, a bespoke solution is required to match the desired pressure and the situation on site.
Medium Pressure Gas Meter Installation
For Medium Pressure (MP) installations you will need to indicate the required meter pressure you require.
A medium pressure gas supply requires a Senior Meter Technician (SMT) engineer who has been through specific training. Medium pressure supplies are rare which is why not all engineers are trained in them. Different pressure control arrangements and additional competences are required for medium pressure work under the Nationally Accredited Certification Scheme (ACS) for low and medium pressure metering work.
Note: Recently there has been an increase in the use of medium pressure gas supplies to domestic premises.
HAZARDS with Medium Pressure Meter Installations
Meter Housings: Meters supplied from a medium pressure service must be housed externally to the building in a surface mounted meter box; or purpose-built compartment. Meters shall not be located within the premises or recessed meter boxes. The proposed location for the meter and regulator installation and the design of any purpose-built compartment must be agreed with the Gas Transporter Company (GTC) at the initial design stage.
Proximity to buildings – must be considered
Medium Pressure installations have hazard zones associated with them. All electrical equipment and building openings must be outside the hazard zone.
For domestic installations the hazard zone is small. A distance of 1m from electrical equipment and building openings should be maintained.
For Commercial medium-pressure installations, the meter must be sited at least 3 metres from the nearest property or ignition source. There must also be constant access for future maintenance or any potential emergency works including a dedicated parking space allocated for a maintenance vehicle.
Medium Pressure Gas Connection Costs
Connection costs for all pressures are dependent upon the length of the service, the load requirements (Peak Flow Rate) whether the connection is to a Low Pressure, Medium Pressure or Intermediate Pressure pipeline and the road classification. In calculating the charge, the length of the service will be based on the distance from the nearest suitable Distribution Pipeline to the meter position.
Note*
Risk Assessment – Medium Pressure (‘MP’) fed gas service – If the property is supplied via an ‘MP’ service and it is discovered that it has been ‘built over’ i.e. the meter and regulator are located within the building, the installation should be classified as ‘At Risk’ (‘AR’) in accordance with the procedure detailed in the current GIUSP (TB 001(1)). This is because of the increased risks associated with elevated gas pressures