Air-controlled, pilot-operated, balanced piston relief valve

Capacity: 200 gpm760 L/min. | Cavity: T-18A
RPKD : Air-controlled, pilot-operated, balanced piston relief valve
Technical Features [ + ]

Air-controlled, pilot-operated, balanced piston relief cartridges use compressed air over a diaphragm instead of an adjustable spring to control pressure setting. The air signal is supplied through a port in the hex-end of the cartridge. They 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).
  • Will accept maximum pressure at port 2; suitable for use in cross port relief circuits.
  • Maximum air pressure should not exceed 150 psi (10 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.
Technical Data [ + ]
Note: Data may vary by configuration. See CONFIGURATION section.
Cavity T-18A
Series 4
Capacity 200 gpm760 L/min.
Maximum Operating Pressure 2000 psi140 bar
Pilot Ratio 20:120:1
Maximum Valve Leakage at 110 SUS (24 cSt) 5 in³/min.@1000 psi80 cc/min.@70 bar
Maximum Air Pressure 150 psi10,5 bar
Response Time - Typical 10 ms10 ms
Valve Hex Size 1 5/8 in.41,3 mm
Valve Installation Torque 350 - 375 lbf ft474 - 508 Nm
Model Weight 2.50 lb1,15 kg
Seal kit - Cartridge Buna: 990018007
Seal kit - Cartridge Polyurethane: 990018002
Seal kit - Cartridge Viton: 990018006
Performance Curves [ + ]
FAQs [ + ]

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.

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.

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.
Additional Resources [ + ]