Relief valve assembly with reverse flow check and start-up valve


Function for YFRC
Port Designators [ + ]
Modifiers Ports
D, D/S Ports P, S, T2: 3/4" NPTF; Port T1: 1/2" NPTF; Gage Port: 1/4" NPTF; Tank Port: 3/4" NPTF;
L, L/S Ports P, S, T2: SAE 12; Port T1: SAE 8; Gage Port: 1/4" NPTF; Tank Port: 3/4" NPTF;
W, W/S Ports P, S, T2: 3/4" BSPP; Port T1: 1/2" BSPP; Gage Port: 1/4" BSPP; Tank Port: 3/4" NPTF;
Technical Features [ + ]

This assembly consists of a 30 PSI check and a pilot-operated, balanced-piston relief cartridge which is a normally closed pressure regulating valve. When the pressure at the inlet (P port) reaches the valve setting, the valve starts to open to tank (T port), 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.

This assembly also incorporates an air-bleed and start-up cartridge which is used to purge air trapped in the system to help reduce power requirements and facilitate pump priming during the start-up of blocked center circuits.

  • Back pressure on the tank port (port 2) is directly additive to the valve setting at a 1:1 ratio.
  • Air-bleed and start-up valves require a minimum of 4 gpm (15 L/min.) flow rate and 80 psi (5,5 bar) system pressure.
  • The air-bleed and start-up valve will re-open when system pressure falls below 25 psi (1,7 bar)
  • After air has been purged, closing times vary from approximately 12 seconds at 4 gpm (15 L/min.) to 0.5 seconds at 50 gpm 200 L/min.).
  • Suitable for use in load holding applications.
Technical Data [ + ]
Body Type Line mountLine mount
Capacity 40 gpm160 L/min.
Check Cracking Pressure 30 psi2 bar
Mounting Hole Diameter .41 in.10,4 mm
Mounting Hole C'bore Diameter .59 in.15,0 mm
Mounting Hole C'bore Depth .31 in.8 mm
Mounting Hole Quantity 22
FAQs [ + ]

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

Reasons to anodize:

  • To increase corrosion resistance. Sun uses 6061-T651 aluminum. It is one of the most corrosion resistant aluminum alloys there is. Whether or not anodizing improves the corrosion resistance of 6061 aluminum is debatable. We have yet to have a manifold returned because of corrosion.
  • Appearance (color). The 2 colors that would appeal to Sun would be blue or black. Unfortunately these are the colors that are hardest to do consistently.
  • To provide a hard wear surface. Sun does not make parts-in-body valves. The manifold is just plumbing. We don't need a wear surface.
  • Because everyone else does it. Bad reason. 

Reasons to not anodize:

  • Cost. It's another process.
  • Logistics. When you make tens of thousands of manifolds a month and you anodize hundreds, it's a problem. Consistency. See above.
  • Stamping. After a body is anodized you cannot do any more stamping without making a mess.
    Inspection. Have you ever tried to look for burrs in a black anodized body? It's the old blackboard factory at night scenario.
  • Torque. You will experience an increase in breakaway torque when removing items from an anodized manifold.
  • Fatigue life. This is the best reason to not anodize. Fatigue failure is a very complex phenomenon. What it takes to initiate a crack is difficult to predict. What it takes to propagate a crack is readily defined. Anodizing produces a very thin, very hard, and very brittle surface on aluminum. The first time you pressurize an anodized aluminum manifold you have initiated fatigue cracks. Whether or not the stress is enough to propagate the cracks is a matter of pressure and manifold geometry. Anodizing an aluminum manifold grossly reduces the fatigue life by anywhere from 20% to 50%.

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.

Notes [ + ]
  • Important: Carefully consider the maximum system pressure. The pressure rating of the manifold is dependent on the manifold material, with the port type/size a secondary consideration. Manifolds constructed of aluminum are not rated for pressures higher than 3000 psi (210 bar), regardless of the port type/size specified.
  • For detailed information regarding the cartridges contained in this assembly, click on the models codes shown in the Included Components tab.
Additional Resources [ + ]