Oil flow relay (indicator) for transformer forced-circulation cooling systems
The oil flow indicator is a protective relay that monitors circulation lubrication and circulating oil cooling of machine installations and transformers. If a pump stops, or a pipeline clogs or breaks, the indicator gives a signal or trips the installation before it is damaged.
- Types
- 11 (SF 25), 14 (SF 25/10) flanged; 13 (SG 25) threaded
- Nominal bore
- DN 25
- Pick-up setting
- 0.35 m/s ±15 %
- Drop-out setting
- 0.17 m/s ±15 %
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
On transformers with forced oil circulation (OF/OD cooling) the relay confirms that oil is really flowing through the coolers. The indicator is built into the pipework of the circulation system. The free length of pipe between it and the nearest fixing point must not exceed 0.5 m, and bends are made with an inner radius of more than 50 mm. The indicator belongs to the same family of relays as the Buchholz relay and the OLTC monitoring relay, and shares technical data with them.
The oil flow moves the flow flap to its working position. When the velocity falls below the setting, the flap returns to its initial position and gives a fault signal. The pick-up setting is 0.35 m/s and the drop-out setting 0.17 m/s, both with a tolerance of ±15 %, operating time less than 0.1 s. The relay works at a very low operating pressure, so it can be installed even in a drain line, where the flow is created only by the slope of the pipe.
The range includes flanged types 11 (SF 25) and 14 (SF 25/10) and threaded type 13 (SG 25), all with nominal bore DN 25 and a mass of 3.1–4.0 kg. The housing and cover are cast from a coated aluminium alloy. Inspection windows with hinged covers show the flap position, and the cover carries a test and reset button. The terminal box holds reed contacts, and the cable enters through M20/M25, 1/2″ NPT or a Harting connector. The nameplate shows the type, code, serial number, contact kind (normally open, normally closed, changeover) and enclosure rating. A typical order looks like this: type 11 with one normally open contact, an M20x1.5 entry, IP 66 and housing colour RAL 7033.
Every unit undergoes dielectric strength and leak tightness tests, a functional test and a flow check. The contacts switch AC/DC 5–250 V at 0.01–6 A, switching capacity 1500 VA/1250 W, dielectric strength 2500 V. Ambient temperature −40…+55 °C, oil −40…+115 °C, up to +135 °C in version 21, viscosity 1–1100 mm²/s. Vibration resistance 2–200 Hz/2 g, shock 25 g (class 4M6), enclosure rating IP56. The indicators are used on power transformers at power plants and substations and in the oil systems of industrial equipment.
Technical specifications
| Types | 11 (SF 25), 14 (SF 25/10) flanged; 13 (SG 25) threaded |
|---|---|
| Nominal bore | DN 25 |
| Pick-up setting | 0.35 m/s ±15 % |
| Drop-out setting | 0.17 m/s ±15 % |
| Operating time | < 0.1 s |
| Contacts | AC/DC 5–250 V, 0.01–6 A |
| Liquid temperature | −40…+115 °C |
| Enclosure rating | IP56 |
| Mass | 3.1–4.0 kg |
Request a price and lead time
Oil flow relay (indicator) for transformer forced-circulation cooling systems. 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 settings does the flow indicator have?
The flap moves to its working position at 0.35 m/s and returns at 0.17 m/s, with a tolerance of ±15 % on both settings. Operating time is less than 0.1 s.
Can the indicator be installed in a drain line?
Yes, the relay works at a very low operating pressure. It is installed even where the flow is created only by the slope of the pipe.
What connection versions are available?
Flanged types 11 (SF 25) and 14 (SF 25/10) and threaded type 13 (SG 25), all on DN 25. Mass 3.1–4.0 kg.
Similar equipment from other manufacturers
