Monday, 4 July 2011

Water Pump Won't Pump Water!

The last episode of the Worthington-Simpson Boiler feed pump destined for the cab left a cliff-hanger: it was merrily allowing air to be blown through the pump section forwards or backwards.  As such, the chances of it actually being much better when faced with pumping water were not good. And guess what?  I was dead right; not a sausage of a spurt!

Up to this point, I'd looked fairly carefully at the steam end but ignored the water end of the pump assuming it would 'just work'. I should have known better; it's always the assumed bits (that make an 'ass' out of 'u' and 'me') that don't work.

I began with the section drawing.

WS BFP Pump Section
The inlet is the lower and the outlet the upper of the orifices on the right hand side. The inlet feeds up through the middle of the two cylinders to the lower of the two banks of four valves. As the pistons move back and forth, they suck water in through the lower set of valves and then blow out through the upper set; the valves enable water to pass one way against a spring pressure but lock themselves closed for the other way. Hence they are non-return valves (a bit like diodes if you are that way inclined).

Even though I'd previously suspected the piston rings, the fact that I could easily blow through would not be affected by the piston rings. Therefore it had to be the valves so I took them apart one by one.  Fortunately, a large hex key worked well to undo them all.

Hex key removing the valves
(with a little help from me when needed but it sat there just nicely for the photo!)
Being a water pump, all fittings are brass and not corroded despite being 60 years old.
Top view (water is pumped up from below the valves)
All of the upper set of four outlet valves are clear and in good condition.
View of valve seats from underneath
The lower set which receives the incoming water was rather more interesting. Clearly a filter had not been used to sift out rubbish and something akin to pieces of a matchstick and other 'detritus' had got into the seats of three of the valves.
One of the offending pieces of matchstick...
... and where it was not very usefully lodged!
Detritus (bits of old sock to you and me) also in the works.
No socks-appeal here!
Having cleared all the bits and pieces and reassembled the valves and the pump section, it was clearly harder to blow any air through albeit that there was not a complete seal so perhaps the valve faces will need regrinding. So, the bit you've been waiting for, here's a little more video with the valves seated. (Also on YouTube).
As well as the view from the water end, there is also a very subtle acoustic difference to before in that there is a feint 'raspberry' in time with the pump strokes. But as with deep-seated raspberries, you'll probably need a good subwoofer with your speakers to hear it!

Just to complete the picture, some photos follow of other WS bits and pieces.

Valve components
Broken spring, later suitably 'bent' into shape and stretched to fit.
Now, how to ensure that it will pump into 275psi boiler pressure! Continued here.

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