Electro-proportional, direct-acting, pressure reducing/relieving valve with drain to port 4
This electro-proportional, direct-acting reducer/reliever valve reduces a high primary pressure at the inlet (port 2) to a constant reduced pressure at port 1, with a full flow relief function from port 1 to tank (port 3). The valve is biased to the relieving mode. Energizing the coil connects port 2 to port 1. Increasing the current to the coil will proportionally increase the reduced pressure at port 1. If pressure at port 1 exceeds the setting induced by the coil, pressure at port 1 is relieved to port 3. Draining port 4 makes the valve insensitive to pressure at port 3. This valve is closed in the transition between reducing and relieving resulting in very low consumption of oil. Optional full manual control is available.
- Maximum pressure at port 3 should be limited to 3000 psi (210 bar).
- All spring ranges are tested for correct operation with 5000 psi (350 bar) inlet pressure.
- Suitable for accumulator circuits since the absence of pilot control flow results in reduced secondary circuit leakage.
- Direct acting concept provides highly reliable operation in contaminated systems, especially at dead headed conditions.
- Leakage specified in Technical Data is out of port 3 with a supply pressure of 2000 psi (140 bar) and the valve set at mid range. This leakage is directly proportional to pressure differential and inversely proportional to viscosity expressed in centistokes.
- The transition from reducing to relieving is closed. The result is very low leakage. However, there is a transitional step increase in pressure between reducing and relieving modes. This step equals about 5% of the high end of the adjustment range, independent of the valve setting.
- For optimum performance, an amplifier with current sensing and adjustable dither should be used. Dither should be adjustable between 100 - 250 Hz.
- Full reverse flow from reduced pressure (port 1) to inlet (port 2) may cause the main spool to close. If reverse free flow is required in the circuit, consider adding a separate check valve to the circuit.
- Uses for the 'L' manual screw adjustment include: emergency valve setting during power failure or alternatively boosting the valve setting
- With the 'L' adjustment screw, all ranges are factory set at zero (adjustment screw fully backed out). With the coil de-energized, clockwise adjustment of the screw will increase the spring bias load up to the maximum setting for that range. With the coil energized, any mechanical pressure setting is directly additive to the coil induced value.
- By controlling the pressure at the drain (port 4), the effective setting of the valve can be increased over the nominal valve setting.
- Pressure on the drain (port 4) is directly additive to the valve setting at a 1:1 ratio and should not exceed 3000 psi (210 bar).
- 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.
| Cavity | T-21A |
| Series | 1 |
| Capacity | 5 gpm20 L/min. |
| Maximum Operating Pressure | 5000 psi350 bar |
| Maximum Valve Leakage at 110 SUS (24 cSt) | 2.5 in³/min.41 cc/min. |
| Optimum Inlet Pressure | 3000 psi210 bar |
| Adjustment - No. of CW Turns from Min. to Max. setting | 55 |
| Solenoid Tube Diameter | .75 in.19 mm |
| Valve Hex Size | 7/8 in.22,2 mm |
| Valve Installation Torque | 30 - 35 lbf ft41 - 47 Nm |
| Adjustment Screw Internal Hex Size | 5/32 in.4 mm |
| Locknut Hex Size | 9/16 in.15 mm |
| Locknut Torque | 80 - 90 lbf in.9 - 10 Nm |
| Model Weight (with coil) | 1.20 lb0,55 kg |
| Seal kit - Cartridge | Buna: 990021007 |
| Seal kit - Cartridge | Polyurethane: 990021002 |
| Seal kit - Cartridge | Viton: 990021006 |
| Seal and nut kit - Coil | Viton: 990770006 |
| Hysteresis (with dither) | 6%6% |
| Hysteresis with DC input | <8%<8% |
| Linearity (with dither) | <2%<2% |
| Repeatability (with dither) | <2%<2% |
| Recommended dither frequency | 140 Hz140 Hz |
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.
Yes. A reducing or reducing/relieving valve is normally open. If the pressure in the secondary circuit is less than the setting, it will be open.
2 caveats: (1) If the valve is in the reducing mode and you suddenly reverse the flow, the valve will not have time to open and will shift into relieving mode or (2) If the back flow generates a pressure drop through the valve that exceeds the setting, the valve will shift into the relieving mode.
When in doubt, use a reverse flow check.
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.
Yes. If you look in the sandwich section you will see that we offer many such packages. When you are pressurizing B, A is connected to tank, allowing the reducer to do its job. When you reverse, the drain or tank port of the reducer is pressurized by A. This increases the setting of the reducer and helps keep the reducer open in the reverse flow direction.
Our reducing valves are outside-in valves; the supply pressure on the outside of the working parts is higher than the inside. At some pressure differential, the outside (sleeve) will close in on the piston and cause the valve to stick. A D range is adjustable from 25 to 800 psi with a maximum differential of 2000 psi. This means you could set the valve at 600 psi and expect it to work correctly with a supply pressure of 2600 psi. The valve may work at higher differentials, but we do not recommend it. The W and C ranges are tested over their entire range with an inlet pressure of 5000 psi. All direct-acting valves are tested with an inlet pressure of 5000 psi.
No. A reducing/relieving valve throttles a supply of oil to maintain a set pressure in a secondary circuit. The valve is open until the secondary or downstream pressure rises to the setting of the valve at which time it starts to close to limit the pressure. If the secondary or downstream pressure is caused to go above the setting, the valve shifts into relieving mode and throttles the secondary circuit back to tank to prevent over-pressure. At no time can the valve connect the supply to tank.
There are exactly 250 Sun drops in a cubic inch or 15 in a cc.
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