R900590334 DB10-2-5X/315 German Rexroth overflow valve

Frequently Asked Questions (FAQ)

Q1: Is DB10-2-5X/315 direct-acting or pilot-operated?

It is a pilot-operated (two-stage) relief valve. A small direct-acting pilot valve controls pressure over the main stage spool, giving better pressure stability and lower pressure override at high flow compared to a direct-acting valve of the same size.

Q2: What does "2 - 5X / 315" mean in the model?

• 2​ = adjustment type: hexagon socket with protective cap (Allen key adjustable).

• 5X​ = component series index 5X (dimensions fixed within series 50–59).

• /315​ = pressure stage, maximum adjustable relief pressure = 315 bar (adjustable roughly 4–315 bar).

Q3: How do I adjust the relief pressure?

Depressurize the system, remove the protective cap, turn the internal setscrew with an Allen key — clockwise to increase, counterclockwise to decrease. Reinstall the cap and verify with a pressure gauge at the P-port. Factory preset is typically near the low end of the range; always adjust on-site.

Q4: Which subplate is required?

Use a standard NG10 (Size 10) subplate​ per ISO 6264 with P and T ports. The valve mounts via four M10 bolts (tightening torque approx. 35–40 N·m). Subplate port threads are commonly G 1/2" BSP or M18×1.5. Optional port X (pilot remote control) and Y (external pilot drain) are available on the valve body if remote control or external drain is needed.

Q5: What is the difference between internal and external pilot drain?

This model has internal pilot drain (standard DB type)​ — pilot oil returns to tank via the T-port internally. If there is significant backpressure on T, consider the DB…Y version (external pilot drain to tank) to prevent backpressure from affecting the set pressure.

Q6: Common fault symptoms & causes?

• Pressure won't reach set value / unstable:​ contaminated pilot orifice/nozzle, wrong pressure stage, excessive T-backpressure (on internal drain version), or broken pilot spring.

• Slow response / pressure creep:​ clogged pilot line/nozzle, air in pilot circuit.

• External leak / dribble:​ damaged O-ring on mounting face, contaminated pilot seat — check subplate flatness and O-ring condition.

• Chatter:​ air in the system, excessively long pilot lines if remotely connected, or flow near Qmax — bleed air and verify proper subplate installation.

Q7: Fluid & seal compatibility?

Standard NBR seals suit mineral oil (HL/HLP) and HFC (water-glycol). For HEES/HETG biodegradable oils or HFD phosphate ester, FKM (Viton) seals are required — order the "V" seal variant if needed.