how to cut rusty steel tube from thin SS skin.

[Fil]

I need some advise and help. i am facing my first stainless steel vessel mod.

i have this problem to deal with.

i think its a galvanised steel tube that has been welded or braised flush in a thin SS skin to create a bottom drain.

from the inside the rust ring of the tube top stands out. so it needs to go if i am to use this for brewing.

if i were to use an angle grinder i run the risk of creating too much heat and further damaging the SS finish?

could i cut the tube with a hacksaw close to the skin, and use a q max cutter? how much residual pipe could a qmax cutter cup deal with? would it cut thru the weld/braise?

or am i overlooking a simple solution?

once removed i will need a low profile bulkhead fitting, SS would be preferable where should i look for one?

there are also a few rust spots in the SS where water has gathered and 2 surfaces have rested, how is this best treated? I found this
http://www.ehow.com/how_7884554_rust-of ... ances.html
but no mention of cleaning off the rust with sandpaper first?? some of the rust here is a bit ingrained/ established? like here: around the thermo-pocket weld.

is pickling paste available anywhere in small quantities i can only find 2kg packs..

until recently my brewery has been totally plastic, so this shiny stuff is all pretty new, so any help is appreciated...

cheers

 

[EskiBrew]

Don't worry too much about the heat, you can remove the bluing with a bit of wire wool and elbow grease.

 

[Kev888]

yep, you may cause it to dis-colour but an angle-grinder isn't as bad as welding heat if you're just a tad careful. You can get special discs for stainless (sometimes called inox); the standard ones can sometimes transfer plain steel/iron to the stainless and start rust that way, though I must say i've not had massive problems when I've used them.

Could be a bit tricky to grind out, with the disk being much bigger than the tube, but it should be possible if you're reasonably handy with such things. Alternatively, you could use a TCT holesaw to cut around it, or less good/easy (but possible with care if you have a very slow drill) a cobalt holesaw; but either way if you try that, hammer a round bit of wood or something into the pipe so that the cutter's centre drill can drill in and locate itself, otherwise it'll wander about.

You can get brass tank connectors from most plumbers and DIY sheds. For stainless, I found ASAP supplies good - I think they do a version with a hosetail too, and a smaller range with longer threads.

Yes, stainless can rust in the right conditions. In some cases you can use chemicals (acids), but in most cases like this if you rub off/out the rust manually and leave the bare metal open to the air for some hours it will self 'passivate', i.e. develop its oxidised layer, but make sure its very clean (clean and de-grease it first) or you could prevent the air getting to it and stop that happening. Also, don't use iron/steel tools to rub it back, as again they could transfer rustable metal to the surface of the stainless.

Cheers
Kev

 

[evanvine]

**** a brick! I hope you could follow all that Fil.

 

[Fil]

followed digested both eagerly and thankfully evanvine :)..

Cheers Kev, those asap fittings look the business, no mention of the profile? how far they stick up in the pan.. with a large flat bottom mm mean litres..

a bit of poor mans scotchbrite (back of washing up sponge) work then on the superficial stuff.
and a lifetimes supply of pickling paste for the bits that remind me of the exhaust on my ol rat bike.

the drain itself, well im not skilled with any power tools, and only handled an angle grinder a couple of times, and to drill with a tct cutter with the base supported i would need to lean in with my top weight and gravity pushing onto the drill so no control at all.

As a short term plan im going to cap it off using SS washers with a long nut n bolt. my reasoning is if i tell everyone i cocked it up i will then again bump into the world expert who i always seem to meet a week or two after cocking up any job beyond my scope, however this time i will be ready to call their bluff ). i can then position the drain where i want it. closer to an end will allow me to tip slightly to empty more out minimising deadspace i hope.


cheers

 

[silverbrewer]

That stainless has some weird shapes and sides.......It's not an old trough style urinal is it?

Where are you based, then someone with tools could probably pop round to help. Wire wool may induce further rusting, so try to make do with your plastic Scotch brite type stuff.

Have you thought to cut a fair size hole say 6" dia and then get someone to weld in a shallow cone with your fitting in it's centre, or better still, a welded in pipe, that then takes a tap.

Tell peeps it is for a home made brewery and you sometimes get real good prices from fabricators.

 

[EskiBrew]

Personally I've never had a problem using wire wool on stainless - the passivation is very rapid :thumb:

 

[Fil]

That stainless has some weird shapes and sides.......It's not an old trough style urinal is it?

not quite. but since you ask.... :)

its a big steamer...

that top area is 45l :)

the whole thing is just shy of 90l capacity

its not evident in the pics but there is quite deep rust underneath the lid (other side of the hinge fittings, and underneath the false bottom in the corners..


I was looking for cheap catering stockpots, for a single level covererd and pumped brewery upgrade from my 45l mango barrel patio set up.. and this was mislabeled as a deep fat fryer on ebay..i chucked a £50 punt at it and won. It was a safe bet as a pal with a houseful would have snapped it up if it was a deep fat fryer..

However i am now considering turning this into a rims single vessel full volume biab type thingy, If I can sort out the rust, and fit a clean drain.

Ive asked about and nobody i know knows a SS fabricator locally so its down to yell.com or oxforddailyinfo and speculative calls i guess to get something like you suggest done? the wheels and handle make me think that a small ramp and a shove at the end of the emptying will tip the bottom end down low to minimise deadspace if i relocate the drain closer to the bottom/back edge..

I gave it a test boil with about 15- 20l in it 3-4 inches depth (just over its designed boil depth) and it achieved and maintained a rolling boil but the built in thermostat wavered around 59 to 75C when i set it to approx 67C.

next i will give it a test with about 80l in and see if it will maintain a rolling boil.. if not i can add a second element, and insulate the central pan, which i shall do anyway.

with a custom biab bag and using hop socks, a pid controller, pump, a small box of fittings, and some of vossy1's silicone tube its almost an out of the box solution..

If i work it out right i hope to brew 3 corny batches in this..

 

[Kev888]

Cheers Kev, those asap fittings look the business, no mention of the profile? how far they stick up in the pan.. with a large flat bottom mm mean litres

I've got the 3/4" ones (makes draining quicker when cleaning/rinsing); they sit about 5.5mm proud of the surface plus any sealing washer - although you could use a thin sealant such as LS-X or (more un-do-ably) JB-weld. They're also pretty robust things; if you're not going to give them too much jip I'm sure you could grind down the top a bit (either all over or in one or two places) - though they're quite smooth and shiny so would be a shame in some ways.

IIRC someone (Vossy?) clamped a brass flanged nut or tank connector 'under' the hole in the base by drilling holes for a ring of small bolts through both of them. Seems a good way to get zero deadspace, though I'd imagine it takes a bit of care/skill on the DIY front. I made a recess in a french stock pot for one of my ASAP fittings with a home-made wooden punch affair - but it wasn't that easy even in thin metal.

Cheers
kev

 

[Aleman]

As a replacement for the pipe consider a Through Deck Fitting . . . Available in stainless and a very low profile

Available in a variety of sizes from chandlers and a quick search on eBay reveals Lots

 

[Fil]

wey hey.. never looked at boaty bits before, i might have something to talk about with the g/fs ol'man at christmas this year now.

5.5mm or 6mm not too bad especially if i ramp one end up to drain more from the other, and a 3/4" drain would be quicker to empty :)

following silverbrewers advice i checked out local SS fabricators, and rang a local "and sons" business who responded very positively and said the lads dont turn down lunch time cash jobs :)
so im taking it over there for a look see later in the week.. They sounded familiar with the type of problem as i was not speaking the correct language being all layman like i am. and the chap i spoke with seemed to recognise the problem as he offered a new drain nipple as an option..

My pal had an observation about the rusty pipe, its rusty only near the weld. could it be SS and is rusting due to poor post weld treatment?? the other areas of deep rust in the thing support this as they are the back ends of welds and spot welds too? interesting take and something that didnt even dawn on me.

 

[Kev888]

yeah those ASAP fittings I linked to are skin or thru-hull fittings for boats too; I often feel theres a lot about marine life and boats that could be helpful!

Its possible the pipe is rusted stainless, though in the pic it appears very rusty, painted and with rust spots along it too, so not sure. Either way, it looks like a bit of a bodge job that a competant stainless fabricator could replace or rectify. I'm just learning to tig weld, and I've not yet caused anything stainless to rust like that.

Cheers
kev

 

[evanvine]

Am I being very naive, I thought the Chrome content prevented rusting, must be thinking of something else!

 

[Aleman]

Am I being very naive, I thought the Chrome content prevented rusting, must be thinking of something else!

The problem is that if you overheat the weld/stainless the carbon 'burns off' and reacts with the chrome removing the protection and hence it rusts

 

[Kev888]

+1

Also if you use steel tools on stainless you can leave tiny bits of plain steel/iron behind, stuck in the surface of the stainless, which can give rust a place to get started. I can't claim to have had massive problems with this myself, but I understand it can be a problem in the right circumstances.

Cheers
Kev

 

[evanvine]

Thanks AM, Kev.
Another myth blown to hell!

 

[Fil]

can i ask the experts....

with deep rust in stainless steel thats going to be acid paste treated, is it necessary to clean all the rust out first or will the acid deal with that too?

I ask as i have a few areas such s the inner weld seam of the false bottom corners, which would need a shot blaster ricochet to get at..

tia..

 

[wezil]

Hi the rust can be cleaned off with phosphoric acid (jenolite) this will also act as a flux if you solder or braze the new fitting in. Or clean the old fitting with the acid then paint with a cold galvanising paint. Hope this helps.

 

[Fil]

Hi the rust can be cleaned off with phosphoric acid (jenolite) this will also act as a flux if you solder or braze the new fitting in. Or clean the old fitting with the acid then paint with a cold galvanising paint. Hope this helps.

cheers wezil, im building up quite a list of things to read up on treating SS from salt and lemon juice, oxalic acid(rhubarb), bar keepers friend, off the shelf SS cleaner products among the weaker more freely available products..

and phosphoric acid too now.. :)

the friendly welder wanted £75 i didnt feel very friendly after driving 30 miles round trip to get the quote.. so will be attempting to cut it out and fit one of the skin fittings myself..

 

[wezil]

£75!!!!!!! to weld up 1 fitting!!! (im in the wrong game)! Get a blow lamp some acid and some silver solder and do it yourself!! prob less than £20! . And yes silver solder will be strong enough (you could try lead free but im not sure how it would take to s/s (just found a link on homebrewtalk.com on doing just this!!