Pilot-operated, balanced piston relief valve
Symbols for RPKC
Pilot-operated, balanced-piston relief cartridges are normally closed pressure regulating valves. When the pressure at the inlet (port 1) reaches the valve setting, the valve starts to open to tank (port 2), throttling flow to regulate the pressure. These valves are accurate, have low pressure rise vs. flow, they are smooth and quiet, and are moderately fast.
- All 2-port relief cartridges (except pilot reliefs) are physically and functionally interchangeable (same flow path, same cavity for a given frame size).
- 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.
- Will accept maximum pressure at port 2; suitable for use in cross port relief circuits. If used in cross port relief circuits, consider spool leakage.
- Main stage orifice is protected by a 150-micron stainless steel screen.
- Not suitable for use in load holding applications due to spool leakage.
- Back pressure on the tank port (port 2) is directly additive to the valve setting at a 1:1 ratio.
- W and Y controls (where applicable) can be specified with or without a special setting. When no special setting is specified, the valve is adjustable throughout its full range using the W or Y control. When a special setting is specified, this setting represents the maximum setting of the valve.
- Corrosion resistant cartridge valves are intended for use in corrosive environments and are identified by the model code suffix /AP for external stainless steel components, or /LH for external zinc-nickel plated components. See the CONFIGURATION section for all options. For further details, please see the Materials of Construction page located under TECH RESOURCES.
- 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-18A |
| Series | 4 |
| Capacity | 200 gpm760 L/min. |
| Maximum Operating Pressure | 5000 psi350 bar |
| Factory Pressure Settings Established at | 4 gpm15 L/min. |
| Maximum Valve Leakage at 110 SUS (24 cSt) | 5 in³/min.@1000 psi80 cc/min.@70 bar |
| Response Time - Typical | 10 ms10 ms |
| Adjustment - No. of CW Turns from Min. to Max. setting | 55 |
| Valve Hex Size | 1 5/8 in.41,3 mm |
| Valve Installation Torque | 350 - 375 lbf ft474 - 508 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 | 2.50 lb1,15 kg |
| Seal kit - Cartridge | Buna: 990018007 |
| Seal kit - Cartridge | EPDM: 990018014 |
| Seal kit - Cartridge | Polyurethane: 990018002 |
| Seal kit - Cartridge | Viton: 990018006 |
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.
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.
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.
There are exactly 250 Sun drops in a cubic inch or 15 in a cc.
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.
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