Mechanical Lubricator's Central Heating

It was April 2013 when I last wrote about 7109's mechanical lubricator. I'd been concerned that the heating system using exhaust steam had not been working although it didn't seem to be a significant problem.

Aluminium heater (centre top of photo)

Exhaust steam is fed to a blind Aluminium tube fixed into the bottom of the lubricator underneath the four pumps. The idea is that the steam condenses giving off its latent heat to the lubricator and the condensate drains via an external hole in the fitting.

Aluminium Heater close-up

Recently 7109 was running without the near-side engine covers in place and somebody pointed out that steam and water were being sprayed all over the rear engine when moving. On inspection, the spray was coming from the condensate drain hole.

Not having given the subject much thought, I'd originally installed the heater with the drain hole pointing upwards and this was the cause of the spray. It had also not caused me any concern because, for a long time after I'd had trouble with gland packing disintegration, the exhaust steam feed pipe to the lubricator had become blocked with the spifflicated packing. Thus the spray only became obvious when I unblocked the feed pipe.

Unfortunately, the PTFE washer used to seal the heater had worn such that I couldn't just rotate the heater and so it all had to come apart to do the job properly.

Corrected down-facing condensate drain hole.
The squashed white item is the new PTFE washer.

Disassembly does have the advantage that it gives an opportunity to do other bits of maintenance. In particular, it had always been impossible to see the oil level in the sight glass as the glass tube itself was dirty. I hadn't originally had access to a parts washer but I now it is an invaluable tool for cleaning such items and the result is below.

Newly cleaned level sighting tube

It does show the level (I tightened the leaky seal later)

To tighten the tube, the lubricator's lid fixing bolt above the sight glass has to be removed and a tapered flat-blade screw driver used to turn a hidden grub-screw. Removing the grub-screw allows the glass tube to be removed.

The top and bottom of the glass tube had originally been sealed using leather washers; the leather had deteriorated so I used a pair of fibre washers instead.

Oil consumption now seems to have increased, no doubt due to the oil being thinner at the raised temperature.