Solenoid operated pilot relief assembly
|A, A/S||Ports 1 & 2: 1/4" NPTF; Port G: 1/4" NPTF;|
|I, I/S||Ports 1 & 2: SAE 6; Port G: 1/4" NPTF;|
|T, T/S||Ports 1 & 2: 1/4" BSPP; Port G: 1/4" BSPP;|
This assembly consists of a direct-acting relief cartridge which are normally closed, pressure-limiting valves used to protect hydraulic components from pressure transients. When the pressure at the inlet (port 1) reaches the valve setting, the valve starts to open to tank (port 2), throttling flow to limit the pressure rise. These valves are smooth and quiet, essentially zero leak, dirt tolerant, immune to silting and are very fast. The 2-way, 2-position solenoid directional valve provides a means to unload (bypass the relief valve) the system.
- Back pressure on the tank port (port 2) is directly additive to the valve setting at a 1:1 ratio.
- Suitable for use in load holding applications.
- This assembly 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.
- The assembly's direct acting relief valves exhibit rapid response characteristics that minimize pressure overshoot and also provide low reseat leakage (less than 5 drops/min (0,3 cc/min) @ 85% of cracking pressure).
- 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.
|Capacity||.25 gpm1 L/min.|
|Body Type||Line mountLine mount|
|Mounting Hole Diameter||.34 in.8.6 mm|
|Mounting Hole Thread||.250-20 UNC - 2B in..250-20 UNC - 2B in.|
|Mounting Hole Depth||ThroughThrough|
|Mounting Hole Quantity||11|
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.
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%.
- 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.
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