Tag Archives: feed pump

A final video: Everything running on the bench

First Fix the Bugs!

Following on from the Boiler test, and a quick trial we identified just over 20 items that needed some attention. So a week later, with all these items fixed (from leaking valves to painting and plating valve gear components), we are ready to try again.

The Fire-up Plan

We enlist the support of neighbour Micheal Slack (who is also housing the hull) and embark upon a frantic half hour of trying to put the water and steam where we need it and get the plant running properly.

This involves:

  1. Lighting the burner, and raising some steam.
  2. Getting the blue steam pump pumping cooling water thru the condenser to condense the exhaust steam from pump (and engine).
  3. Warming the engine thru with steam to get it ready to start.
  4. Getting the engine to run so that the air pump removes the condensed water from the condenser to create a vacuum.
  5. Getting the boiler feed pumps on the engine running (so Mike can stop with the hand pump).
  6. And get the alternator running to prove that we can provide electrical power for the burner, lights, radio etc.

Getting that lot to happen at the same time took some time and several attempts (and a lot of water on the floor)! It will me much easier when there is a lake providing the cooling feed water, rather than a hosepipe and bucket! But it all worked even the real McCoy lubricator and the whistle!

I was also pleased that the engine does not appear too noisy or knocking, just a bit of noise from the chains. So a good day!

A video of the day

Enjoy the video of edited highlights – with enthusiastic commentary from our “cameraman” Louise!

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Worthington Simpson Pump Restoration

You will have realised that I am a bit of a sucker for ageing lumps of cast iron in need of restoration. So I could not resist a circa 1940 Worthington Simpson Steam Pump that Mark Rudell offered to me. It seemed it would serve well as a boiler feed pump or circulating pump for the condenser. (providing I could ignore the fact that it’s about 5 times the size we need – but hey the designer said I needed 500KG of ballast in the bottom of the boat, and given I can barely lift this beauty it’s all grist to that mill!)

It clearly needed a bit of a clean and a check over, and it took about a week’s work. These are often known as “Donkey Pumps” as they tend to do their work for years with little in the way of maintenance or attention – it seems this one had certainly “done its time” in this mode.

Rather than provide a blow-by-blow commentary on the work it involved, the following pictures will hopefully provide the detail:

  1. Get it apart, Inspect, remove (many) layers of old paint, and clean inside and out.
  2. Reface the mating faces of the pump valve chests.
  3. Reseat/regrind the 8 suction and supply valves (using reciprocating valve grinder).
  4. Repack and adjust the glands on steam and pump cylinders.
  5. Make new packing rings for pump cylinders (in PTFE).
  6. Turn a blind eye to the wear in the pump cylinders (I might re-sleeve these later)
  7. Paint.

It runs well, and the remaining wear in the pump cylinders make it less efficient than it should be, but in it’s planned role as circulating pump it should be fine…. The pictures show some of the steps: (remember you can click to see a full size image…off to watch Strictly !)

 

 

A Boiler Full of Steam

Well the 10th November 2017 marks a major milestone – the boiler passed its initial inspection and steam test, and is now certified for use. (big smiles all round).

Picture of Engine, Boiler Etc. ready for test

Sadly, everything was too frenetic to take pictures during the steam test – but here it is just before we pressed go!

John, our inspector from SBAS Ltd (the SBA’s Boiler Inspecting Company) had been booked to arrive at 3:00pm – at 9:00am I set about final sealing of the try-cocks on the sight gauge – at 1:30pm I nearly called to cancel the appointment as no amount of fiddling and fitting would make them seal, with a constant drip from each of them at anything above 50psi 😦

Finally I made them seal with a combination of shredded graphite string and a binding of PTFE tape to seal the valve stems – dry as a bone at test pressure of 375spi, big sigh of relief. A final tightening of some of the 60+ joints in the steam circuit and we wound up with a boiler that held over 350psi for over one and a half hours without a single pump being needed. (This is a hydraulic test so the boiler is filled to the top (to exclude all the air and thereby minimise any “bangs” resulting from a failure.)

So the pressure test is complete. Next the steam and accumulation tests. So we wheel the complete set of machinery (engine, boiler, steam pumps, battery and regulator) outside (with a lot of puffing and blowing), drained the water in the boiler down to operating level, and we light the burner.

The burner needed some adjusting to get it to light and burn fairly cleanly (a little more tweaking needed) and we quickly had 10psi on the gauge (5-6 mins)  – so we turned off the burner and checked round for leaks or other problems and to let the boiler “adjust” to its new state of hotness.

All looked good so we brought it up to 50psi to check the water gauge (sight glass) was reading correctly and all the various blowdows operated correctly – they did! (more smiles).

The next step is to make sure the safety valve opens at the correct pressure and is able to control the pressure within 10% of safe working pressure with the burner full on.

So, burner on and another 10mins to come to working pressure of 250psi (17Bar) – whereupon I got an impromptu (but complete) hot shower. The safety valve did open OK, but as the water was quite high in the boiler. and had been dosed with washing soda to bring the PH up to 11 (and probably because of all the crud left in the boiler) we got a lot of water carried over into the exhaust steam (what is known as priming) which provided the aforementioned hot shower. There was enough showering down on the 240v wiring of the burner that I decided to kill the power while we dried things off….

So with a little less than a litre of diesel left for the burner we lit it once more and went for the accumulation test. By now it’s getting a little cold and dark, so reading the gauge within the billowing clouds of steam was quite hard for John, but after a few minutes he was happy that all was good – we were passed.

Not wanting to waste all this nice steam we tried the Worthington Simpson steam pump (A post on the restoration of this is on the way) in anger, and it performed quite well – supplying feed water at over 200psi….. and then we tried the engine!  after some warming thru this ran too and even the generator seemed to be making 7.5amps at a modest speed – but we highlighted the next (somewhat expected) list of jobs:

  • Two of the relief-drain valves seemed not to want to close (more clouds of steam and investigation needed)
  • The circulating pumps (engine driven) did not deliver enough cold water to the condenser to condense the exhaust steam and create the vacuum. So we are going to revert to the original design of the engine-driven pumps acting boiler feed pumps and the steam pump as a circulating pump.
  • I think I saw a couple pin-hole leaks in the feed pump plumbing which need checking
  • We need to finalise the plumbing from the cylinder drains
  • On the next run we need to get the displacement lubricator running.
  • We need to check the alternator performance to make sure we can generate the 20+amps we need to drive the inverter for the burner.

….then we can think about attempting to install the whole she-bang in the hull!!!! (Spring ’18 Launch – yes,  I think we might make it!)

Edwards and Feed Pump VIdeoz

Here’s a better video (with iffy commentary) showing the feed and air pumps (and alternator) drive in action.

The Edwards pump is working, but I’m not sure that the flap valves are holding pressure (as it seems to have to start from atmospheric on each stroke…) but clearly the ball valves on the feed pumps are very sound (they actually hold 50psi for hours)…..

enjoy…

A Suitable end to a winter’s engineering!

The plan is to work with the seasons and transition from boat building when it’s warm to mechanical engineering when it’s winter – and we are clearly heading into spring and temperatures in the boat house are becoming tolerable, and suitable for working with Epoxy; however, I was loath to make the switch back to boat building until I had concluded the design and construction of the pump and alternator drive assembly.

This has proven a very slow process, and as my good friend  David Mattingley pointed out there is a world of difference between building something from drawings and designing and building from scratch.

The design process – solid modelers

pump/alternator drive

Isometric of the planned pump and alternator assembly

I used PunchCAD’s ViaCAD 3D to draw the basic arrangement of this assembly, and this solid modeler was a new experience for me having previously only used 2D CAD systems (like Autocad). With this new solid modeling approach you manipulate 3d objects (cylinders, cubes etc.) to construct a computer model of the thing you are planning to build. You drill holes in things (by subtracting a “hole-sized” cylinders from the object) and merge primatives to create more complex shapes (like the alternator and gear box in the attached pic). This approach allows you to see clashes of components and get a good feel for clearances and shape of the final assembly. It requires a very different mindset. When the model is complete it is possible to create dimensioned 2D drawings of each part (although I confess I found it hard to get this feature to provide exactly what I wanted.)

This got me to phase 1, with the worm box, chain-wheels, v-belts and alternator all in position, and running smoothly (although it did not predict that the chain would need a tensioner as the centre distance I had chosen for the chainwheels forced us to fit a chain that was almost exactly one link too long) 😦

The lengthier part of the build/design process was to then mate this assembly to the air and feed pump assembly we completed a month or so back.

Feed Pump Drive

I had decided to use the worm-box output shaft to drive two cranks, each being used to form a scotch crank assembly (see this nice video if you are not familiar with how a scotch crank (AKA Scotch Yoke) works). This meant I could remove the uneven stress on the worm box if we only drive the pumps from one side. It became clear we should mount the pumps over the worm box, to avoid adding too much height to the engine assembly, and so an arrangement with 4 “side levers” running down from the pump crosshead to the scotch cranks seemed right. Mounting the pump assembly required a stiffened plate which I fabricated from some 3mm Brass plate I had in the “stock pile”.

The cranks are fitted to a keyed shaft, and each crank pin is 10mm silver steel. I found some thin section ball races (10mm ID, 15mm OD and 4mm wide) from Bearing Boys, and used two on each crankpin. However, I was unsure of the load capacity of the bearing, and the spreadsheet I had constructed for the pumps suggested that the four bearings needed to support a dynamic load of almost 100lbs (when pumping @ 200psi), and while this theoretically would be shared across 4 bearings, this would require “perfect” conditions. During an initial test I accidentally jammed a plastic mug! into the assembly stalling the engine – this resulted in two of the bearings failing with split outer races. I suspect the jam caused the bearings to be axially overloaded, but none the less this failure was worrying.

I contemplated fitting needle roller races to raise the load capacity, but as an initial “fix” I fitted 3mm thick outer “retaining rings” in silver steel to the bearings to strengthen the outer races… with this fix in place and some hose pipe to prime the pumps I ran a test with a pressure gauge on the feed line, and a 200psi safety valve to regulate the pressure (as you can see we reached over 250psi in practice).

As the video below shows we appear to have a working system (with hints of Tardis – don’t you think!!!) – the variability in pressure is to some extent caused by the safety valve, but also I think the pump valves may be slow to seat…

I feel I can now get on with the “wood work”, with a job well done!!!

 

Gaskets and Unions

Well, the last week or so has been dedicated to finishing the air pump and feed pump assembly. The original owner of the castings had partially machined and assembled the main air pump castings, but they needed “fettling” to fit. This ranged from minor adjustment of PCD bolt holes, replacement of pump rod, and other minor work thru to remachining / truing of all of the mounting faces, fitting o-ring to undersized piston, reboring the feed-pump rams (to provide increased capacity needed for geared-down operation), the making of all the feed-pump valves and manufacture of all (bar one) of the pipe unions.

This involved a variety of odd-ball threads… I think this assembly now includes all the following:

  • 1/4 x 25 TPI British Standard Fine
  • 3/8 & 1/2 British Standard Pipe (parallel)
  • 9/16 x 26 TPI (actually a British Standard Cycle Thread)!
  • 2BA (British Association)

The larger ones of these were either entirely screw cut on the lathe or screw cut and then “chased” with a standard split die. With the new insert/index threading tools this all went really well.

Interestingly (and as a demonstration of the value of “keeping everything”) a great many of the bolts on the engine are 1/4 BSF, and luckily at a club Auction at Guildford Model Engineering Society (I used to be a member), I managed to purchase a bucket of 1/4 BSF Allen Bolts for about a fiver …. I just had to look after them from 1985 ’till now to find a use for them!

The assembly also needed a number of gaskets (about 7) and these were all cut using a ball-peen hammer and centre punches to tap them out from the components they were sealing. This is such a simple and effective process (but one that many people seem not to know) that I included some pictures of the process in the slideshow below….

(also see link about drawing errors on this part here)

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