Boiler bits

Typical, Christmas Eve, get in from work, house cold.
I have a Glow Worm Ultimate FF boiler. I've always thought it a stupid idea having a fan in the hot gases from a boiler (yes I know, all the power stations have them, but they probably have guys with oil cans at the ready) and I've been proved right. The fan has seized up. A little oil in the bearings has got it going again in the meantime, but do you really have to replace the whole unit - fan, case, little pipes for the pressure switch, or is there a way of replacing the bearings?
If it is a matter of buying the whole unit, where's the best place to buy it?
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John Rouse

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geoff

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geoff wrote:

i had mine from yourselves about 3? years ago...not had any probs with it until recently it has started making dreaded rumbling noise again...i will be ordering another one soon! wouldnt it be great if they could be manufactered with a grease nipple? lol
steve
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downhill and we changed manufacturer having had about a 20% failure rate on soak test.
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geoff

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I've never looked closely at the bearings in one of these but I think I'd guess them to be the "oilite" type used in many small electric motors (e.g. car heater fans). This is very often a sintered bronze "ball" in a self-aligning housing: cheap, robust, reliable. The bronze on steel combination is a good bearing to start with, and being porous it's helped along by being impregnated with mineral oil. However, they can dry out (not helped by being in a draught). There's a trade-off in lubricating them: use something low viscosity and it soaks in better, but will be more volatile so won't last so long. Higher visosity oils won't soak in so well but won't evaporate so quickly either. With WD40 you have a thick mineral oil dissolved in a thinner one: should last quite well as long as it isn't too warm. Or you could try a silicone oil: a less good lubricant for metals, but will stand higher temperatures. The excellent screwfix spray sold for plumbing comes to mind although I have never tried it on a metal bearing.
My credentials: I've been using combis for > 10 years without a problem in fans (but have been a specialist in oily bearings for the best part of 35 years).
S
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Once ball bearings lose their grease, or sintered bearings dry out, it's only a matter of time before they fail completely.
Sintered bearings are lubricated with Anderol, a synthetic oil. WD40 will keep the bearing going for a short while, but is not a long term solution (pun not intended)
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geoff

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