My problem is with a Dungs MVD 515/5 (1 1/2") gas valve here in Australia. It replaced an old 215/5 which had a burnt out rectifier board. Local agent did not have the same so supplied the higher pressure rated version. Has a 110VAC coil for this particular site. It worked for about a month. Then would not open unless the body was given a thump with your fist. The installation as with the original is with flow vertical up, so coil axis horizontal. This is approved by Dungs. Opened up valve and found no foreign material in the valve. Noted that the valve armature/ slug had a black finish (See attached). Like metal blueing. Have since found out it is a nitriding finish called Corr-I-Dur. The surface finish was not smooth and there was signs of rubbing on this coating. We have never seen this type of coating on a Dungs valve before. Also the small guide pin/spindle has a small wear ridge in it. No sign of any lubrication on either. From the markings it looks like the assembly has "cocked" and misaligned. We polished it up on a lathe with very light emery. The coating came off easy and produced a smooth silver finish. Sprayed on some Teflon dry lube on armature and spindle and refitted. There have been no problems since over the last few weeks. Have checked supply voltage OK. Pressure to this valve is natural gas at only 5.5kPa (The valve is rated to 50kPa). So far Dungs have been unhelpful. They say both the armature and the pin slide in a plastic bush and don't need lubrication. However the agent opened up another similar valve and found grease on the pin. We found no sign of any grease anywhere. Has anyone any ideas or experienced the same? Maybe specifically with a 110VAC coil?? Rod.

Rod Nissen.
Combustion & Engineering Diagnostics

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