BB 25 (type 22) Buchholz relay for rolling stock traction transformers
The Buchholz Relay BB 25 (type 22) is a double-float gas relay for rail rolling stock, primarily for the traction transformers of electric locomotives and multiple units. The relay has a G 1½″ threaded connection on DN 25, a mass of 4.2 kg and is rated for transformers up to 5000 kVA.
- Type
- 22 (BB 25 / DG 25)
- Connection
- G 1½″ thread, DN 25
- Transformer rating
- ≤ 5000 kVA
- Mass
- 4.2 kg
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
A stationary transformer stands still, while on a locomotive the relay works all the time at a changing tilt angle, during acceleration and braking, and under heavy vibration. The BB 25 design is adapted to exactly these conditions. The relay is insensitive to shocks, so it gives no false operations. It is installed in the pipe between the traction transformer tank and the conservator. In normal operation the housing is completely filled with insulating liquid and both floats are at the top.
Free gas lowers the upper float, and the relay gives an alarm signal. If there is a lot of gas, it passes on into the conservator without touching the lower float. In an oil leak the upper float operates first, then the lower one, and the transformer is tripped. Sudden damage creates a pressure wave that deflects the flow flap of the lower system, and the transformer is tripped in this case too. After the wave has passed, the system returns to its initial position. The flap is set to 0.65, 1.00 or 1.50 m/s with a tolerance of ±15 %. Function is checked with the button on the cover or with a test pump.
The electrical connection is made through a cable gland or a pre-assembled Harting connector, which simplifies relay replacement in the depot. By order code, the entries available are M25x1.5, M20x1.5 with a Harting connector, or 1/2″ NPT, with IP 66 enclosure and housing colour RAL 7033. For example, one can order one normally closed contact in the upper system and two normally closed in the lower, a flap set to 1.00 m/s and a pre-assembled Harting connector. Besides type 22, the relay types 04 (BG 25), 21 (BG 25 S), 06 (BF 25/10) and 08 (BF 50/10) are suitable for rolling stock.
The general data of these relays are as follows. Contacts AC/DC 5–250 V, 0.01–6 A, switching capacity 1500 VA/1250 W, ambient temperature −40…+55 °C, oil temperature −40…+115 °C, basic enclosure rating IP56. The relays are supplied with a test report covering dielectric strength, leak tightness, function and flow checks. Technical documentation is in English, German, Polish and Chinese. The relay is taken by manufacturers of traction transformers and rolling stock, and is also installed during repair and modernisation of locomotive fleets.
Technical specifications
| Type | 22 (BB 25 / DG 25) |
|---|---|
| Connection | G 1½″ thread, DN 25 |
| Transformer rating | ≤ 5000 kVA |
| Mass | 4.2 kg |
| Feature | stable operation at a changing tilt angle, high vibration resistance |
| Wiring | cable gland or pre-assembled Harting connector |
| Other types for railways | 04 (BG 25), 21 (BG 25 S), 06 (BF 25/10), 08 (BF 50/10) |
| Contacts | AC/DC 5–250 V, 0.01–6 A |
Request a price and lead time
BB 25 (type 22) Buchholz relay for rolling stock traction transformers. We reply within one business day.
Or email sales@usk.ua or call 044 339-50-20.
Customs codes
| UKTZED (Ukraine) | 8536 49 00 00 |
|---|---|
| HS, 6 digits | 8536 49 |
| CN (EU) | 8536 49 00 |
| HTSUS (USA) | 8536 49 00 85 |
| China customs tariff | 8536 49 00 00 |
Codes are for reference: the final code is determined at declaration for the specific model.
Questions and answers
What traction transformer rating is the BB 25 suitable for?
Type 22 is rated for transformers up to 5000 kVA. The connection is a G 1½″ thread on DN 25, mass 4.2 kg.
What other relays are used on rolling stock?
Types 04 (BG 25), 21 (BG 25 S), 06 (BF 25/10) and 08 (BF 50/10) are also suitable for rail transport.
How is the relay connected to the control circuits?
Through a cable gland or a pre-assembled Harting connector. The contacts are rated for AC/DC 5–250 V and 0.01–6 A.
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