Flow control valve is mechanically controlled one-way check valve that can control the flow. It is normally installed onto the connection pipe between transformer and oil tank. When there is massive oil flowing out or leakage due to internal failure with transformer or for other reasons, such flow control valve will respond with "shutting off against oil release" so that oil supply between oil reservoir and oil tank can be cut off immediately. Consequently, oil reservoir will not provide any supply to oil tank. Therefore, it is ideal and auxiliary protection for oil immersed power transformer.
2. Technical data
2.1 Nominal diameter: ф80mm
2.2 Nominal pressure: 0.2Mpa
2.3 Applicable temperature: -40°C~95°C
2.4 Min. cut-off flow rate: 0.3~0.5m/s
2.5 Signal contact point: normally closed contact: 1 pair
2.6 Contact capacity: 20VA
3. Principle of construction
3.1 Flow control valve consists of valve body, valve bonnet, valve plate, dry-reed contact and reset handle (as seen in fig.1). Junction box is located on the valve bonnet. While transformer is in normal service, magnet 5 located on valve plate is attracted by the magnet on support 4. Valve plate 1 is projected at about 35° for half opening. Normally closed dry-reed contact 2 is in open position due to attraction by another magnet on valve plate. There is no signal output coming out of it.
3.2 In case transformer has failure and there is oil release with flow rate reaching the setting, valve plate will automatically shut off so that oil reservoir will stop supply to oil tank of transformer.
3.3 After valve plate is closed, dry-reed contact is not attracted by the magnet so that it closes. It will send out alarming signal through junction box 3.
3.4 While transformer is in normal service, valve plate can stably stay at half open for two reasons: mutual attraction between magnets and pulling by a spring of resetting mechanism. In case of transient overpressure or accidental vibration against transformer, the valve plate will not close up.
4. Installation and operation
4.1 Correct installation of flow control valve: Set up flow control valve in serial connection to the connection pipe between oil reservoir and transformer. Valve body should not tilt. The arrow should point towards the transformer.
4.2 Signal out-lead should be connected to wire terminal. Valve plate is in engagement position and dry-reed contact is disengaged.
4.3 Once valve plate is closed off, it does not have auto reset function. In case valve plate closes during operation, open up the valve plate by turning the handle in clockwise direction. Then get it reset by turning the handle in counterclockwise direction.
4.4 Once the handle is reset, it should stay horizontal. Lock the handle up with screw to avoid any unexpected operation. When oil is filled through oil reservoir or oil is manually released at bottom of the transformer, turn the handle in clockwise direction so that valve plate opens. Then lock it up with screw as seen in fig. 2.
5.1 During normal operation, signal light should not be switched on. Implement a check when signal light is switched on.
5.1.1 Check to see if valve plate is closed. If handle is still in engaged position as normal, it indicates the dry-reed contact for item 2 as in fig. 1 is not disengaged. In this case, make adjustment to contact in fig 1 so that such contact disengages.
5.1.2 Check up the lead wire. In case falloff or poor contact, repair the connection so that there is normal signal communication.
6.1 Dismantling or adjustment to pullback spring is prohibited after flow control valve is delivered out of factory.
6.2 After valve spool is removed, please proper set up the flow rate and test it after assembly. Flow rate must fulfill requirement of 2.4.
7. Notes to improvement
Based on original arrangement, three positions are added to flow control valve: ON, Operation and OFF. Flow rate remains unchanged. Now flow valve is more flexible and reliable.