Direct-acting, pressure reducing/relieving valve
Direct-acting, pressure reducing/relieving valves reduce 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). These valves incorporate a damped construction for stable operation allowing the use of high reduced pressure.
- Pressure at port 3 is directly additive to the valve setting at a 1:1 ratio and should not exceed 3000 psi (210 bar).
- 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.
- Cartridges configured with EPDM seals are for use in systems with phosphate ester fluids. Exposure to petroleum based fluids, greases and lubricants will damage the seals.
- All three-port pressure reducing and reducing/relieving cartridges are physically interchangeable (i.e. same flow path, same cavity for a given frame size). When considering mounting configurations, it is sometimes recommended that a full capacity return line (port 3) be used with reducing/relieving cartridges.
- 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.
- 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.
- Unlike pilot operated versions, direct acting valves exhibit a transitional step between reducing and relieving modes. This step equals 5% of the high end of the adjustment range, independent of the valve setting. Therefore, these valves may not be suitable for counterbalancing applications.
- Direct operated version offers superior dynamic response compared to equivalent pilot operated models.
- 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-17A |
| Series | 3 |
| Capacity | 40 gpm160 L/min. |
| Maximum Operating Pressure | 5000 psi350 bar |
| Factory Pressure Settings Established at | 0.25 gpm0.25 gpm |
| Maximum Valve Leakage at 110 SUS (24 cSt) | 4 in³/min.65 cc/min. |
| Adjustment - No. of CW Turns from Min. to Max. setting | 55 |
| Valve Hex Size | 1 1/4 in.31,8 mm |
| Valve Installation Torque | 150 - 160 lbf ft203 - 217 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 | 1.50 lb0,70 kg |
| Seal kit - Cartridge | Buna: 990017007 |
| Seal kit - Cartridge | EPDM: 990017014 |
| Seal kit - Cartridge | Polyurethane: 990017002 |
| Seal kit - Cartridge | Viton: 990017006 |
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.
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.
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