Electro-proportional relief valve - pilot capacity, high pressure setting with no command
This 2-port, pilot-stage, direct-acting relief cartridge is an electro-proportionally controlled, normally-closed pressure regulating valve. The valve is spring biased closed to its highest setting (customer specified). Increasing current to the coil will proportionally decrease the pressure setting. When the pressure at port 1 (inlet) is sufficient to overcome the spring force minus the solenoid force, as determined by the analog input signal, the poppet lifts and allows flow from port 1 to port 2 (outlet). This pilot control cartridge utilizes the T-8A cavity so it can be used in conjunction with Sun's main stage, pressure control elements.
- Customer must specify a relief setting that falls within the selected pressure range. This setting represents the maximum relief pressure which the valve will default to with no command. As the command increases, the relief setting will decrease. See performance curves for selected pressure range. This setting is not adjustable in the field.
- Varying the analog input signal to the proportional solenoid provides a step-less control of pressure.
- This electro-proportional cartridge utilizes the Sun T-8A, 2-port cavity making it the ideal choice to use in conjunction with Sun's main stage cartridges. Separate pilot lines are eliminated and only one cavity needs to be machined to accommodate both the control and primary function. Note: All 2-port pilot stage control cartridges utilize the same cavity and are physically interchangeable. Functionality is the only consideration.
- High pilot capacity allows for operation of larger size main stage elements.
- Damped construction provides stable operation over a wide range of operating conditions.
- Low leakage levels in the closed position. (Reseat occurs at 85% of cracking pressure.)
- Coils are interchangeable with Sun's other full flow, solenoid operated valves and can be mounted on the tube in either direction.
- For optimum performance, an amplifier with current sensing and adjustable dither should be used. Dither should be adjustable between 100 - 250 Hz.
- Note: The main stage valve should first be installed to the correct torque value followed by the T-8A pilot control section into the main stage valve to its required torque value.
- Incorporates the Sun floating style construction to minimize the possibility of internal parts binding due to excessive installation torque and/or cavity/cartridge machining variations.
|Capacity||.25 gpm1 L/min.|
|Maximum Operating Pressure||5000 psi350 bar|
|Maximum Valve Leakage at Reseat||1.5 in³/min.25 cc/min.|
|Reseat||>85% of setting>85% of setting|
|Solenoid Tube Diameter||.75 in.19 mm|
|Valve Hex Size||7/8 in.22,2 mm|
|Valve Installation Torque||20 - 25 lbf ft27 - 33 Nm|
|Model Weight (with coil)||1.00 lb0,45 kg|
|Seal kit - Cartridge||Buna: 990208007|
|Seal kit - Cartridge||Viton: 990208006|
|Seal and nut kit - Coil||Viton: 990770006|
|Hysteresis (with dither)||<4%<4%|
|Hysteresis with DC input||<8%<8%|
|Linearity (with dither)||<2%<2%|
|Repeatability (with dither)||<2%<2%|
|Recommended dither frequency||140 Hz140 Hz|
The kick-down relief acts much like a circuit breaker. When the pressure at the inlet (port 1) of the relief valve rises to the setting, the valve pops open and drops the pressure down to 100 psi or so. The valve stays open until flow through it stops. Shutting off the supply of oil will reset the valve; reversing pressure on the valve is a positive way of resetting it.
One graphic example is on a portable grain auger for silos. When the farmer gets caught in the auger the kick-down relief trips and allows him to escape.
There are exactly 250 Sun drops in a cubic inch or 15 in a cc.
Pressure setting tolerances are listed in our Performance Data page. A link to this page can also be found in the Additional Resources tab of the applicable product page.
Maybe not. We build in a good amount of overlap in the kick-down reliefs to prevent false tripping. This means they are not as fast as our standard pilot-operated reliefs. A direct-acting relief valve set just above the kick-down relief valve would be good insurance.
Direct-acting valves are used to prevent over pressure, and pilot-operated valves are used to regulate pressure. If you are unsure, use a direct-acting valve. Sun's direct acting valves are very fast, dirt tolerant, stable, and robust. Sun's pilot-operated valves are moderately fast, they have a low pressure rise vs. flow curve, and they are easy to adjust.
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