Constant Flow Regulator Valve

Constant Flow Regulator Valve
UF series

Easy flow rate setting and outstanding constant flow characteristics

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Structure & Principle (PAT.)

Constant Flow Regulator Valve


By adjusting the opening of the adjustment valve disk with the handle, the required flow rate is set. Inlet pressure (primary pressure) P1 is adjusted to intermediate pressure Pd by the throttle resistance in passage A.


Inlet pressure P1 acts on the top of the diaphragm via the primary pressure pipe, and pushes down the sliding valve.


From the lower side, intermediate pressure Pd and working force of the coil spring push up the sliding valve until it is balanced. Then it forms passage B and outlet pressure P2 is created by convergence.


When inlet pressure P1 rises, the transmission of pressure P1, which acts on the top of the diaphragm, pushes down the sliding valve. The sliding valve throttles passage B automatically until the sliding valve can regain balance against intermediate pressure Pd and the force of the coil spring, so that the discharge amount is automatically controlled.
According to this principle, the sliding valve is operated only by the differential pressure between P1 and Pd as generated by the opening of the set adjustment valve, and therefore the flow becomes constant at a rate proportional to the adjustment valve opening regardless of the fluctuation of inlet pressure P1 or outlet pressure P2 as caused by the pressure fluctuation in the pipeline.


When the adjustment valve is nearly closed, the adjustment valve disk and the sliding valve disk are integrated via a shaft. Then pressure P1 against the adjustment valve disk from underneath balances with pressure P1 against the diaphragm from above. This makes operation of the handle lighter and facilitates the planning of mechatronics using a low-powered actuator.

Constant flow rate characteristics


Constant Flow Regulator Valve / Constant flow rate characteristics

Flow rate stays at a constant value regardless of inlet pressure (primary pressure) P1, outlet pressure (secondary pressure) P2, and their fluctuation.
Fig.1 shows the valve's ability to maintain a highly accurate constant flow by following the adjustment valve disk opening {S denotes opening (stroke %) in fig.1}, regardless of the large variation of P1 and P2, or the large fluctuation of differential pressure (P1-P2). Further, with the linear characteristic (refer to fig.2), the valve is not influenced by various pipe conditions during operation, and works with good control response and wide control range.

Flow rate control characteristics

Constant Flow Regulator Valve / Flow rate control characteristics

The YOKOTA Constant Flow Regulator Valve has a lift type construction, which shows superb characteristics as a flow rate adjustment valve. Fig.2 shows performance close to the ideal linear characteristic parallel to a 45 degree diagonal line.

Cavitation characteristics

Constant Flow Regulator Valve / Cavitation characteristics

The allowable cavitation coefficients (cc) for the YOKOTA Constant Flow Regulator Valve are:
With a bore less than 100mm: cc = 0.45
With a bore more than 150mm: cc = 0.24

As a result, the range in which the valve can be used safely, including the allowable differential pressure range, can be set extremely wide as shown in fig.3.

Fluctuation of inlet pressure and constant flow rate characteristics

Constant Flow Regulator Valve / Fluctuation of inlet pressure and constant flow rate characteristics

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