PBSI Group - Weir Electrical

Buchholz Relays

P&B Weir Electrical has been a leading manufacturer of Transformer protection relays of the Buchholz principle for 70 years.

The Weir Electrical Company was established in 1937 to manufacture electrical instruments.

In the mid 1940's the company identified a requirement for gas and oil operated (Buchholz) relays to protect oil filled transformers and the first productions units were installed at that time. A continual development programme, in conjunction with the Central Electricity Generating Board, led to the production of the Mk10 Buchholz Relay.

Most faults in an oil filled Transformer are accompanied by the generation of gas. By using a suitable relay the formation of this gas can be used as a warning of a developing fault. 

Products have been designed, tested and manufactured to meet the detailed requirements of British Standard BEBS T2, Eskom and DIN specifications. P&B Weir Electrical were also privileged to be represented on the technical committee responsible for preparation of the harmonised European specification EN 50 216, which relays also comply to.

A vast range of standard product is available, we are also happy to provide units to your specific requirements e.g. with fixings, flanges, conduit entry, calibration, finishes etc.

P&B Weir Electrical maintains a quality assurance system, certified in accordance with           ISO 9001:2008.

Click on the product for the Buchholz Relay leaflet

Dry Air Pump (For testing of Buchholz Relays)


The Dry Air Pump provides a portable solution for on-site testing of Gas and Oil operated Buchholz Relays.

A charge of air is created in the polycarbonate cylinder by means of a foot-operated pump. The cylinder contains an indicating silica gel, which absorbs the moisture present in the air.

The pressure of the air-charge is monitored on the built-in pressure gauge. When a suitable pressure has been attained, the air charge is then quickly passed to the Buchholz via a flexible tube, by opening the ballvalve fitted to the cylinder. To prevent backpressure forcing oil back down the flexible pipe, a non-return valve is incorporated in the unit.

The indicating silica gel is a crystalline material, which absorbs moisture readily. The properties of the crystals can easily be regenerated by heating/drying. The crystals are impregnated with Iron compounds, which give them an orange colour. Upon absorption of moisture these crystals change from their orange colour to a pale yellow and then become colourless.

When the crystals change to pale yellow they should be regenerated.

This gel is not classified as dangerous.



Click on product to view Dry Air Pump leaflet

Remote Gas Vessel RGV


The P&B Weir RGV consists of an oil and gas-proof aluminium vessel with two inspection ports fitted with glass windows,one gratuated.The gases accumulated in the Buchholz relay can be transferred to the RGV for easier measurement on the grauated scale and evaluated by drawing these off at ground level.

The Remote Gas Vessel is mounted at the bottom of the transformer and connected trough the piping to the ballvalves of the Buchholz relay. The RGV is mounted vertically using two M!) tapped holes at the rear or the unit. The pipework should be configured,copper tube 6mm(1/4") o/d should be used to connect between the Buccholz and the RGV using the fittings kit(available Separately: RAG-04928).

Click on product to view Remote Gas Vessel leaflet

If you require specific information on any of our products, please do not hesitate to e-mail us at  weir@pbsigroup.com and we will get back to you!