The FOX VSA Series Flow Regulator, designed for oil-side installation, is an essential component for the safety and efficiency of hydraulic systems. The use of this device is indispensable on all hydraulic accumulators without an integrated poppet valve, particularly where the circuit is subject to negative pressure peaks.

Hydraulic Accumulator Protection

The primary function of the regulator is to preserve the physical integrity of the bladder or diaphragm contained inside the accumulator. By controlling the flow, the device prevents the diaphragm from violently hitting the bottom of the accumulator during pressure transients, a condition that would otherwise cause irreparable damage and compromise the operation of the entire system.

Calibration and Optimal Adjustment

To ensure proper hydraulic damping and diaphragm protection, it is essential to perform a precise calibration procedure. The optimal oil flow adjustment is achieved through a mechanical operation on the control screw: the operator must first bring the screw to the end of its travel and then turn it counterclockwise by exactly one quarter turn (1/4 turn).

Technical Specifications and Performance

The entire product range is sized to withstand heavy-duty operating loads, guaranteeing a maximum allowable pressure of 330 bar for all models in the series: VSA 18, VSA 21 and VSA 34.

Volumetric Flow Rate Management

The maximum flow rates differ according to the model and operating conditions. Without the accumulator installed in the circuit, the VSA 18 and VSA 21 models allow a maximum flow rate of 50 l/min, while the VSA 34 model guarantees a flow rate of up to 90 l/min. When the system operates with the accumulator installed, the maximum flow limit varies dynamically: the value increases according to a function directly proportional to the nitrogen precharge value present inside the system.

Dimensions and Hydraulic Connections

The regulators feature specific connection interfaces for the accumulator side (F) and the system side (F1). The VSA 18 model uses an M 18×1.5-M connection on the accumulator side and an M 18×1.5-F connection on the system side. The VSA 21 shares the M 18×1.5-M connection for the accumulator, but connects to the system through a 1/2″ BSP-F connection. The VSA 34, intended for higher flow rates, adopts 3/4″ BSP-M threads on the accumulator side and 3/4″ BSP-F threads on the system side. In terms of overall dimensions, the VSA 18 and 21 models weigh 0.3 kg and require a 32 mm hexagon (height 45 mm, dimension A 53 mm), while the VSA 34 weighs 0.45 kg and uses a 36 mm hexagon (height 57 mm, dimension A 65 mm).

Technical Summary Table