Mindray DxH500/DxH800: dilution solenoid valves leaking internally and corroding
What happened
The Burkert solenoid valves in the dilution hydraulics fail: fluid leaks inside the valve body, the armature and internals corrode, and the valve keeps working until the coil wiring rots through. Reported in the case as a typical weakness on both models.
What was checked
- Pull the suspect valve and inspect the armature: corrosion, stiffness, whether it still travels freely.
- Open the valve and look for fluid inside the body — that is the internal leak at work.
- Soak and scrub the pistons clean, then lubricate with silicone grease.
- Check the coil: once the leak reaches the winding, the valve is living on borrowed time.
Cause
Reported in the case as a factory weakness of these Burkert valves: internal leakage lets fluid into the valve body, the internals corrode, and in time the corrosion eats into the coil wiring. Piston contamination adds sticking on top.
What was done
The engineers found two approaches that worked in this case. First, rebuild the original valves: disassemble, clean the pistons thoroughly, lubricate with silicone grease. Second, replace the Burkert valves with valves of another make, mounted through adapter fittings on a flange drilled to match — reported in the case as running a year without trouble. With non-original parts on an IVD analyzer, verify wetted-material compatibility and recheck analyzer performance before trusting results.
Safety
Treat every wetted part and drained fluid as potentially infectious, and before the analyzer returns to use run the decontamination cycle and an electrical safety check — a corroded valve with fluid where the coil should be dry is a leakage-current risk.
Lesson: On a wet analyzer a leaking solenoid valve is a countdown, not a one-off fault — open and service the valves at the first signs instead of waiting for the corrosion to reach the coil.
Covered in the course: Lab Analyser Service — Level 2: Fault-Finding →
Written from an anonymised case shared by service engineers. It is not a manufacturer instruction and grants no authorisation. Independent note; names are trademarks of their owners.