Space-saving, pressure-compensated flow control with FLeX Series FREP

Sun offers an electro-proportional orifice & pressure compensator in one cost-effective flow control valve

Sun released the company's first solenoid-operated, 3-way proportional flow control valve as part of the expanding line of FLeX Series valves. The patent-pending, compact FREP combines an electro-proportional adjustable orifice and pressure compensator in one valve and can provide a constant priority flow rate independent of load pressures. It’s well suited for situations where you need to maintain constant actuator speed regardless of the load on the actuator, and it provides excellent variable flow control when using a fixed-displacement pump.

The FREP valve brings precise control to orbital motors on conveyors, spinners or fans for equipment like salt spreaders, agricultural spreaders and seeders. Equipment designers and operators can control material output directly, avoiding excess application of material, saving money, optimizing yield and protecting the environment. With these applications in mind, Sun offers a standard assembly for the FREP with the OMP motor interface so it can be mounted easily on an orbital motor, reducing hosing and providing a more compact solution.

Sun offers six standard OMP-mount manifolds in a range of port sizes. The manifolds include a set of deep mounting holes to accommodate direct mounting of the Sun XMD Mobile Driver to the manifold.  See example shown on the right.

See more product detail regarding these six new OMP-mount assemblies.

The FREP is a compact single valve that features a 30-gpm (120-L/min) rated input in versions with priority flow up to 22 gpm (88 L/min) in three ranges: 

• A range:  0-8 gpm (0-30 L/min)
• B range:  0-15 gpm (0-60 L/min)
• C range:  0-22 gpm (0-88 L/min)

The three ranges allow the designer to dial-in the best resolution for the application and to balance the needs for priority flow and bypass flow.  The FREP can split one input into two flows that are controlled proportionally, allowing you to operate motors and cylinders on both port 3 and port 2.  With the ability to divert oil from the main line of a system without disrupting primary functions, this valve is well suited to power accessories or attachments.

The benefits of the FREP are clear:

• Space-saving, pressure-compensated flow control in a single-valve solution
• Very low leakage compared to competitive valves
• More compact than competing valves with comparable flow rates, using a large hit area on port 3 to deliver higher flows

The FREP’s patent-pending design uses a pull-type solenoid that allows the main throttle spool to be less sensitive to flow forces.  This means you get greater efficiencies, with more flow control using less power than similar valves from the competition.

Material spreaders: control force and speed in one compact assembly

By combining the FLeX FREP and RVCK two-stage relief valve, you can create a solution that controls speed and force using two FREP valves in one compact assembly. In the example below, the augur/conveyor motor is protected against pressure spikes resulting from variations in material size and density using a Sun RDDA direct-acting relief valve. The circuit also includes an anti-cavitation check valve for spin-down on the spinner motor. This kind of circuit can be readily installed on fertilizer or salt spreaders for more simplified, effective machine control.

In this circuit, the second FREP (shown in the center of the circuit above) will close if the spinner motor stalls, causing the conveyor to stall as well, which prevents excess material from dumping into the stalled spinner. In this case, the RVCK will protect the pump. Also, the auger/conveyor drive’s own resistance can keep it from overrunning, so it maintains a positive load on the motor and can make the addition of an anti-cavitation check or brake valve unnecessary in certain applications.

It is important to note that this is a sample circuit, and, as always, you should consider your system requirements carefully when finalizing your design.

Driving attachments & accessories: full-rated bypass flow powers secondary circuit

With the circuit below, as expected, priority flow is always satisfied first, with flow rate determined by the command signal sent to the FREP coil. Using an XMD valve driver with closed-loop control, you can easily dial in the FREP valve flow output and ramping rates for your specific application.

The circuit includes the FLeX two-stage priority relief valve (RVCK) to unload the pump in standby and to serve as the primary pump relief valve. If the priority port is blocked, the FREP will send flow to the bypass port. The bypass port can be fully pressurized independent of the priority port, meaning you can drive a secondary function on another circuit, or you can send the oil back to the reservoir for filtration and cooling.

One of the big advantages in this application is that a single FREP serves as both the variable orifice and the bypass pressure compensator in the circuit. With this one valve in the right circuit, you can reduce complexity and cost while improving performance and efficiency.

In demanding, cost-sensitive applications, the FREP is the smart solution.  Spread the word.

For more information on the FREP valve, download the full data sheet. For expert advice on applying this valve in your application, contact your local Authorized Sun Distributor.