Hotwell position

[quinten1231]

Thank you all for the replies

First off, I was planning on building the boiler myself anyway, so labor cost is of no relevance for me. I have sufficient knowledge on welding etc.

Second, I was planning on burning mainly coal, however would love to have the possibility to burn wood as well as lower quality wood incase of emergency. (Guess that is where the extra grate area comes in handy)

How much do you guys spend on average on boiler material costs?

Because built boilers are incredibly expensive from what i saw, of course most of the price is labor hours, but how much are items such as safety valves etc and the actual metal prices.

And are there special types of steel needed for boiler construction? (Due to heat) I was thinking of using a seamless pipe of about 10-12 mm (preferably 12) wall thickness as the outer shell for the dry-leg vft boiler, similar thickness for tubesheets.
of course high quality steel bought at shipyard, not some random pipe dug up somewhere.
Dont know specifics yet of heating surface etc because I don't know precisely what engine and haven't given much thought to boiler specifications yet.

Am currently looking for a stuart 5a or something alike, do you think that 20sqft are enough for such an engine?


Regards Quinten

[DetroiTug]

We are doing a VFT boiler 16" diameter X 18" tall with 48 1-1/4" tubes (Copying Fred's boiler, hey don't fix what ain't broke ). The outer shell is ASTM A106 seamless with .375 wall. The endsheets are .375 1014 hot roll plate. The cost after some shopping around was $835 shipped Less the threadolets. Some of the quotes were high as 1200..

My take on small VFT's is roughly 6-7 sq feet of heating surface per Horsepower. I've read 5 and 10 sq/ft per horsepower etc. Somewhere in between there - 6 or 7 on average. Many things can affect that though. Boiler design, Turbulators in the flues, economizers, type of fuel, exhausting up the stack (forced draft).

Water tube boiler are around 2 sq ft per horsepower.

There is a lot of cost in piping and of course it's relative to how complex the system is. A simple system, figure on about $600 for valves and piping. That's steam rated valves and schedule 80 pipe.

-Ron

[S. Weaver]

Quinten, if you're building the boiler to code, then your jurisdiction is going to want to see the documentation for the proper steels, welding procedures to be employed, etc. I did that by sending prospective pressure vessel purchase orders for the specified steel to the suppliers. These type of PO's flag that a pressure vessel is under consideration so they need to send properties, heat numbers, etc.

We're finding that the fees for the inspector - plan inspection, fit up and hydro - were going to be as expensive as the steel. So we asked our inspector if we could pool three boilers under one inspection. He consented, so that cut that by two-thirds. I have about $1,500 US in materials for my scotch. The labor (me) for the three is "free."

[Lopez Mike]

Thanks Fred.

One thing I might add is that I have built two wet leg boilers and simplified the 'close quarters at the bottom end of the tubes' issue.

I set up the top and bottom tube sheets in a jig and roll in the tubes first. Only after they have been installed and, in my case, welded in, do I build the rest of the boiler around the tube sheet and tube assembly.

Next is the inner fire box tube. Then the mud ring. And, last of all, the outer shell. With good root welds (TIG) followed by simple 7018 stick welding of the rest, I get a solid, cheap and fast building unit. The firebox opening is done last with a cutting torch and hand grinder.

This make the whole thing much easier. No barked knuckles. No tight quarters doing the seal TIG welds on the tube ends.

I am sooo lucky to live where the only people I need to please are my club inspectors!

Mike

[fredrosse]

Ron, I sent you an e-mail.

[fredrosse]

Mike, looks like you have a good fabrication sequence to put a wet leg boiler together. I was wondering how you get good alignment of the firetubes where they go through the upper tubesheet (while you are making the lower tubesheet connections/welds), perhaps with temporary supports?

[Lopez Mike]

Let's hear it for big lengths of threaded rod, washers and nuts. I set the distance between the sheets with a stick of wood cut to the correct length. I drill the holes for the 3/8" rods at the same time as I bore the fire tube holes, all stacked on the mill. I use the mill as a nice power feed drill press.

I do my layout on the sheets with bluing dye and drafting tools and punch the intersection of the lines with a center punch and a big ugly hammer. The a succession of center drill, bigger and bigger drills and a reamer. Then shim the reamer with a bit of thin stock on one side to get the clearance I want for rolling. Then take the two sheets apart for deburring with an old plumber's reamer.

The 3/8" holes for the thread stock are easily welded up when not needed any more.

I have a friend who is a certified pipeline welder do the welding, both TIG and stick. Root weld with starts and stops ground out and the same for the 7018 stick work. I have a work bench boiler here that runs at 100 psi that I have hydro tested to 400 with no creaking. Only eight inches in diameter and made of sched. 40 well pipe. It ate up a week of evenings in the shop to get it ready for welding. A Saturday of welding. A nice dinner out for the welder and his sweetie. A bigger unit takes longer in proportion.

Some of the detail prep of the steel won't bear letting a customer watch. A circle cutting rig for my cutting torch. A seven inch hand held grinder for the bevels needed for the welding. Sort of like sausage or legislation. Ugly to watch the process.

Our N.W. Steam Society requires a supervised hydro test to 1.5 times the safety valve setting followed by a live test of the valve all done annually. Our state government, confronted with zillions of espresso machines has run screaming form any regulation of hobby boilers (size undefined, I believe). Zero incidents so far. One dolt who refused a test and was sent away to kill himself privately.

Mike