The Steamboating Forum

lostintime wrote: ↑Sat Oct 16, 2021 3:52 am I very much like the "spin the turbulators" idea. I had planned on using them but will now go individuals rather than wire coil pairs.

Kelly Anderson wrote: ↑Sat Oct 16, 2021 3:23 amThe retarders are laser cut by a local shop and measure .050 smaller than the i.d. of the tubes. When new retarders are manually twisted. they seldom stay straight lengthwise, so when installed in the tubes they quite often scrape the tube wall on one side or the other for most of their length.

fredrosse wrote: ↑Sun Oct 17, 2021 5:05 pm With regard to rolling tubes in place, the ASME Boiler Code requires this, regardless of seal welding of tubes or not. If a boiler is made with tubes seal welded, yet not rolled in place, then there is a very small gap between the tube and the tubesheet. Water impurities tend to accumulate in this space, and harden with time. For a VFT type boiler, the lower tubesheet is getting the highest heat flux and this accumulation in the crevasse becomes a hard ceramic-like deposit. Repeated heat-up and cooldown conditions result in the deposit forcing the gap wider, with the kind of forces the are similar to what happens when water freezing within a pipe or pressure vessel. We all know how ice usually damages the steel pipe. I know of boilers made without rolling the tubes in place, and they generally continue to function OK, but why tempt fate, rolling the tubes is a simple operation.

Many small boilers have used ordinary steel pipe for firetubes or watertubes, however this practice is not recommended. Several specifications for steel pipe are prohibited for use in power boilers according to the ASME Boiler Code, so the first question: what specification of steel pipe are you thinking of using? Note that real steel boiler tubes for our pressure applications (ASTM A178 Steel boiler tubes) have the fine finish and precise tube outside diameter to allow professional tube rolling. If you look at the hours of labor needed to make a proper small steam boiler, and you value your time at something more than $10 per hour, then the economy if using sub-standard materials comes into perspective.

cyberbadger wrote: ↑Sat Oct 16, 2021 8:32 pm

Kelly Anderson wrote: ↑Sat Oct 16, 2021 3:23 amThe retarders are laser cut by a local shop and measure .050 smaller than the i.d. of the tubes. When new retarders are manually twisted. they seldom stay straight lengthwise, so when installed in the tubes they quite often scrape the tube wall on one side or the other for most of their length.

Maybe this could be a good winter project for my boiler...

Does the grade of stainless steel matter?

I am questioning because I wouldn't want the stainless steel causing corrosion on the steel firetubes...

Also what thickness or gauge?