R900423724 DBDS6K1X/200 Direct acting relief valve from Rexroth, Germany

FAQ - Frequently Asked Questions

Q1: What does the "/200" suffix mean? Can I adjust it to 250 bar?

A:​ The "/200"​ indicates the valve is equipped with a spring calibrated for a maximum setting of 200 bar. While the valve body is rated for 400 bar, the spring in this specific model is not designed for higher pressures. Do not attempt to set it above 200 bar, as it will not function correctly and may damage the valve. For higher pressures, select a model like DBDS6K1X/315 or /400.

Q2: What is the correct installation cavity and torque?

A:​ You must use a standard DBD NG6 (M28×1.5) threaded cavity. Using an incorrect cavity will cause leakage or malfunction. The recommended tightening torque is 50±5 Nm. Over-tightening can damage the threads or seals, while under-tightening will cause leaks.

Q3: How does backpressure on the T (tank) port affect the valve?

A:​ Backpressure is additive.​ Any pressure at the T-port is directly added to the pressure required to open the valve. For example, if the valve is set to 150 bar and the T-port has 20 bar of backpressure, the system will relieve at approximately 170 bar. Ensure the total pressure (set pressure + backpressure) does not exceed the valve's 400 bar maximum rating.

Q4: Why is the valve chattering or oscillating near the set pressure?

A:​ Chatter is common with direct-acting valves at high flows. Primary causes are:

1. Excessive Flow:​ The NG6 size is optimized for flows up to 50 L/min. If your flow is higher, consider an NG10 valve.

2. High Tank Backpressure:​ Unstable or high backpressure disrupts the poppet's stability.

3. Contamination:​ Dirt can cause the poppet to stick and then release erratically.

Q5: Can I use this valve with phosphate ester (HFD) fluid?

A:​ No, not with the standard version.​ The standard R900423724 has NBR seals, which are not compatible​ with phosphate ester (HFD) fluids. For HFD fluids, you must order a variant with FKM (Viton®) seals, which typically have a /V​ suffix (e.g., DBDS6K1X/200V).