Anti-Shock, pilot-operated, balanced poppet relief valve

Capacity: 200 gpm760 L/min. | Cavity: T-18A
RPKT : Anti-Shock, pilot-operated, balanced poppet relief valve
Technical Features [ + ]

Pilot-operated, anti shock relief cartridges limit maximum system pressure and also limit the rate of pressure rise. The valve opens and then ramps closed at a constant speed, independent of settings and flows. The adjust screw determines the maximum (relief) setting and the minimum (threshold) setting.

  • Will accept maximum pressure at port 2; suitable for use in cross port relief circuits.
  • The seals on the adjust screw are exposed to system pressure which means this valve can only be adjusted when the pressure is removed. The setting procedure is; check the setting, remove the pressure, adjust the valve, check the new setting.
  • Not suitable for use in load holding applications.
  • When pressure at the inlet (port 1) exceeds the threshold setting, the valve opens to tank (port 2). The pilot section moves forward at a steady rate, increasing the setting by compressing the pilot spring. Maximum setting is achieved when the pilot section reaches a mechanical stop.
  • Valve provides protection for pumps and motors from pressure transients due to sudden load changes, especially variable displacement pumps, since the displacement mechanism is sometimes too slow to catch these pressure transients.
  • Valve provides protection for hydrostatic drives by reducing the jerk caused by sudden reversals. The valve is suitable for cross-port applications.
  • When used with a switching device, the valve can provide the ramp characteristic typically provided by proportional valves.
  • Small power units can be started against an anti shock relief to provide longer pump life.
  • Back pressure on the tank port (port 2) is directly additive to the valve setting at a 1:1 ratio.
  • All 2-port relief cartridges (except pilot reliefs) are physically and functionally interchangeable (same flow path, same cavity for a given frame size).
  • 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.
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Technical Data [ + ]
Note: Data may vary by configuration. See CONFIGURATION section.
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.
Control Pilot Flow 10 - 25 in³/min.0,16 - 0,41 L/min.
Pressure Ramp Up Time 400 - 600 ms400 - 600 ms
Response Time - Typical 2 ms2 ms
Adjustment - No. of CW Turns from Min. to Max. setting 4.54.5
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
U.S. Patent # 6,039,0706,039,070
Seal kit - Cartridge Buna: 990318007
Seal kit - Cartridge Viton: 990318006
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Performance Curves [ + ]
Performance Curve for RPKT: Anti-Shock, pilot-operated, balanced poppet relief valve Performance Curve for RPKT: Anti-Shock, pilot-operated, balanced poppet relief valve
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FAQs [ + ]
Can I use a kick-down relief for my system relief?

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 or pilot operated - what do I use?

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.

Where would I use a kick-down relief?

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.

What are the tolerances on pressure settings for Sun's pressure control valves?

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.

How big is a drop of hydraulic oil?  

There are exactly 250 Sun drops in a cubic inch or 15 in a cc.

What parts of the Sun cartridge valve are field serviceable?
Only external seals are serviceable.  Sun offers replacement seal kits for all cartridge models. The applicable kit part number can be found in the product page's Technical Data table or by using our Cartridge Seal Kit search function located under Accessories. Please note: Converting the external seals from one material to another does not ensure fluid compatibility with that material due to the existence of internal seals within the cartridge.
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Additional Resources [ + ]
Highlights
Technical Tips
Technical Information
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