RBAP | Cartridges » Pressure Control » Relief

This 2-port, pilot-stage, direct-acting relief cartridge is an electro-proportionally controlled, pressure regulating valve. The proportional control allows for infinite, step-less adjustability within the selected pressure range. When the pressure at port 1 (inlet) is sufficient to overcome the solenoid forces, as determined by the analog input signal, the poppet lifts and allows flow from port 1 to port 2 (outlet). This pilot control cartridge utilizes the T-8A cavity so it can be used in conjunction with Sun's main stage, pressure control elements.

Varying the analog input signal to the proportional solenoid provides a step-less control of pressure.
This electro-proportional cartridge utilizes the Sun T-8A, 2-port cavity making it the ideal choice to use in conjunction with Sun's main stage cartridges. Separate pilot lines are eliminated and only one cavity needs to be machined to accommodate both the control and primary function. Note: All 2-port pilot stage control cartridges utilize the same cavity and are physically interchangeable. Functionality is the only consideration.
All pressure ranges will drop to a setting of 0 with no analog input signal. The pressure ranges indicate the valve's area of acceptable performance.
The L control (Manual Override - Adjustable) allows one to manually adjust the valve in case of an electrical failure. The L control also allows one to offset the pressure range. For instance, if an A range valve is mechanically offset to a setting of 1500 psi (105 bar), the new maximum will be 4500 psi (310 bar).
The 'E' manual control assembly has a mechanical life expectancy of approximately 7,000 cycles.
Damped construction provides stable operation over a wide range of operating conditions. Note: Models equipped with an 'M' control do not incorporate the dampening orifice in the solenoid armature.
The momentary/twist override option "E" allows the operator to shift the valve by twisting the manual override clockwise 90 degrees.
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.
Note: The main stage valve should first be installed to the correct torque value followed by the T-8A pilot control section into the main stage valve to its required torque value.
For optimum performance, an amplifier with current sensing and adjustable dither should be used. Dither should be adjustable between 100 - 250 Hz.
NOTE: There is no upper limit to the pressure setting when using the M control. The more force you exert on the manual override, the higher the resulting pressure.
High pilot capacity allows for operation of larger size main stage elements.
Capable of operating with pressures up to 5000 psi.
Low leakage levels in the closed position. (Reseat occurs at 85% of cracking pressure.)
Coils are interchangeable with Sun's other full flow, solenoid operated valves and can be mounted on the tube in either direction.
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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Note: Data may vary by configuration. See CONFIGURATION section.

Cavity	T-8A
Series	P
Capacity	.25 gpm1 L/min.
Maximum Operating Pressure	5000 psi350 bar
Maximum Valve Leakage at Reseat	1.5 in³/min.25 cc/min.
Manual Override Force Requirement	10 lbs/1000 psi @ Port 166 N/100 bar @ Port 1
Reseat	>85% of setting>85% of setting
Solenoid Tube Diameter	.75 in.19 mm
Valve Hex Size	7/8 in.22,2 mm
Valve Installation Torque	20 - 25 lbf ft27 - 33 Nm
Model Weight (with coil)	1.00 lb0,45 kg
Seal kit - Cartridge	Buna: 990208007
Seal kit - Cartridge	EPDM: 990008014
Seal kit - Cartridge	Viton: 990208006
Seal and nut kit - Coil	Viton: 990770006

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Note: Data may vary by configuration. See CONFIGURATION section.

Hysteresis (with dither)	<4%<4%
Hysteresis with DC input	<8%<8%
Linearity (with dither)	<2%<2%
Repeatability (with dither)	<2%<2%
Recommended dither frequency	140 Hz140 Hz

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Performance Curve for RBAP: Electro-proportional relief valve - pilot capacity

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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.

How big is a drop of hydraulic oil?

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

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.

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.

How do I get a kick-down relief to reset?

The kick-down relief acts much like a circuit breaker. When the pressure at the inlet (port 1) of the relief valve rises to the setting, the valve pops open and drops the pressure down to 100 psi or so. The valve stays open until flow through it stops. Shutting off the supply of oil will reset the valve; reversing pressure on the valve is a positive way of resetting it.

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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991070 T-8A cavity weatherized coil seal kit
991238 Momentary/twist operation, extended resolution, manual override control kit, E control
991243 Red momentary/twist operation, extended resolution, manual override control kit, E control

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