Stainless steel tubes

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lostintime
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Re: Stainless steel tubes

Post by lostintime » 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.
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Re: Stainless steel tubes

Post by DetroiTug » Sat Oct 16, 2021 5:19 pm

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.
I sheared strips then twisted them. Then I welded on small rod and another short one at the top at 90 degrees to make a T handle. They really only need to be in the water section, so my turbulators only go about 2/3rds up from the firebox. Yes just move them up and down while turning to clean the flues. Their real purpose is to disrupt laminar flow where the hottest gases resist the cooler wall and travel up the center.

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Re: Stainless steel tubes

Post by cyberbadger » Sat Oct 16, 2021 8:32 pm

Kelly Anderson wrote:
Sat Oct 16, 2021 3:23 am
The 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?

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Re: Stainless steel tubes

Post by fredrosse » 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.
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Re: Stainless steel tubes

Post by fredrosse » Sun Oct 17, 2021 5:17 pm

Boiler Fabrication Margaret S VFT Boiler
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Re: Stainless steel tubes

Post by Kelly Anderson » Sun Oct 17, 2021 5:28 pm

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.
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Re: Stainless steel tubes

Post by fredrosse » Sun Oct 17, 2021 5:30 pm

Margaret S Boiler Fabrication Pix
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Re: Stainless steel tubes

Post by Kelly Anderson » Sun Oct 17, 2021 5:32 pm

cyberbadger wrote:
Sat Oct 16, 2021 8:32 pm
Kelly Anderson wrote:
Sat Oct 16, 2021 3:23 am
The 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?
My retarders are made of mild steel, .024 thick (24 gage).
It was not easy to convince Allnutt. All his shop training had given him a profound prejudice against inexact work, experimental work, hit-or-miss work.
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Re: Stainless steel tubes

Post by fredrosse » Sun Oct 17, 2021 5:33 pm

Seal Welds
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lostintime
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Re: Stainless steel tubes

Post by lostintime » Tue Oct 19, 2021 2:07 am

I do not mean to beat a dead horse, but.. when I was referencing tig welding in place I mean having the tubesheet backbeveled and open clearanced to the "pipe" tube so full penetration welded, no micro crevasses for mineral build up ( I am experienced in pressure vessel/piping welding, but in industrial refrigeration, ammonia systems, not steam, I "design, build, and run the "steam" machines backwards" for a living). Unfortunately i don't have a copy of the astm code for the "backwards" side of things. Using energy to move heat, I'm credentialed, backwards.. I'm trying to learn...conceptually very similar, but lots of devils in the details.
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