R900935659 DBW20B1-5X/200-6EG24N9K4 German made electromagnetic relief valve Rexroth

Rexroth DBW20B1-5X/200-6EG24N9K4 — Pilot-Operated Solenoid Relief Valve (P/N: R900935659)

Technical Data / Specifications

Frequently Asked Questions (FAQ)

Q1: What is the difference between A1 and B1 versions (DBW20A1 vs DBW20B1)?

Both are subplate-mounted pilot relief valves with solenoid unload and identical adjustment method (hex socket + cap). The B1 version has a different pilot-stage damping orifice​ — it provides slightly different dynamic response (pressure overshoot/settling) vs A1. Pressure range, flow rating, solenoid, and mounting are identical. A1 is the general-purpose default; B1 is selected when system stability/damping tuning is required.

Q2: Is this direct-acting or pilot-operated?

It is a pilot-operated (two-stage) relief valve with solenoid unloading. A pilot stage controls the main spool for stable high-flow relief; the integrated solenoid can command the valve to dump system pressure to tank.

Q3: How do I adjust the relief pressure?

With system depressurized, remove the protective cap, turn the setscrew with an Allen key — clockwise to increase, counterclockwise to decrease. Factory preset is typically near minimum of the spring range. Reinstall cap and verify with a pressure gauge. The solenoid does NOT change the set pressure.

Q4: What is the solenoid logic?

Standard: Solenoid DE-energized = relief active​ at set pressure. Solenoid ENERGIZED = system unloaded​ (P connected to T, near tank pressure). Confirm this matches your control logic before wiring.

Q5: Which subplate and electrical connector are needed?

• Subplate: standard NG20 (ISO 6264)​ with P and T ports (G 3/4" BSP or M27×2 on subplate), four M12 bolts @ ~70–80 N·m.

• Electrical: EN 175301-803 Form A (DIN 43650-A) 3-pin + PE connector, 24 V DC. If the plug has LED indication, observe (+) / (–) polarity markings.

Q6: Common faults & causes?

• Solenoid clicks but system does NOT unload:​ pilot orifice clogged, main spool stuck, no coil current (check ~18–28 Ω), manual override jammed.

• Pressure won't reach set value / creeps early:​ wrong spring (not /200), pilot damping hole blocked, contaminated pilot seat, excessive T-backpressure (internal pilot drain).

• Coil overheats / burnt smell:​ overvoltage (>10% above 24V), wrong voltage coil fitted — replace only with correct G24 wet-pin coil.

• Chatter / unstable:​ air in system, high T-backpressure, worn pilot seat — bleed air first.

Q7: Does T-port backpressure affect set pressure?

Yes — this model has internal pilot drain. Backpressure at T adds 1:1 to the relief setpoint. If your tank line has >5 bar sustained backpressure, consider the DBW…Y version (external pilot drain to separate tank line).

Q8: Fluid & seal compatibility?

NBR seals = mineral oil (HL/HLP) & HFC (water-glycol). For HEES/HETG biodegradable oils or HFD phosphate ester → specify FKM (Viton) seal variant. Maintain oil cleanliness per ISO 4406 code 18/16/13 or better.