Condensation Hell

[Carlow52]

As someonme who is an owner of the aforesaid orange machinery what do people generally use to protect theirs?

Despite a liberal application of wax I still seem to end up with problems and a discoloured slab of cast iron. Lost count of the amount of time spent with white spirit and webrax cleaning it all off to start again :roll:

Any better ideas?

As has already been explained in some detail in this thread the probelm is caused by the relationship between humidity of the air and the temperature of the machine surfaces.

The ket temperature is the dewpoint and if the machines are kept above this then there wont be a problem

My grandfather had the following system , however am first to admit it is not practical in a full working shop and wont pass muster with health and safety

He had a number of heavy cast iron machines which in cold weqather were covered with a blanket and then a small electric bulb was shoved under the machine.

Just an idea which with modern small thermo stats......

 

[jimi43]

I think a lot of the problems are probably exacerbated by the quality of the cast metals.

I noticed that some cast steel/iron in my workshop do get a blume of surface corrosion the minute the humidity rises above "Gobi desert level" yet my old Taylor lathe made a the turn of the last century never gets any...none...

Strange that! 8)

I think it is the "Forth Road Bridge" syndrome! :mrgreen:

Jim

 

[ondablade]

Cast iron is as you know surprisingly variable stuff Jimi - depending on the metallurgy and casting conditions. The working/physical properties can vary a lot depending on the composition and casting processes: http://en.wikipedia.org/wiki/Cast_iron

It corrodes about 30% slower than steel (the graphite content slows the rusting, as does the 'rind' on un-machined parts), but the big factor I seem to recall is the use of alloying elements like silicon, nickel and chromium which if my memory isn't bust all improve the situation.

So you can conceivably get something made of a low alloy content very basic/cheap cast iron material. The physical properties of this may be variable/reduced too.

Rusting needs water and oxygen present, and is worsened by various forms of air pollution and surface contamination - even by hand marks. Despite what we have been saying about the importance of not getting below the dew point/saturation temperature it's apparently possible to get some moderate rusting of at least steel even when the air is dryer. That said my shop has been around 70%RH/60 -65 deg F for months, and there's no sign of any issues on my machines.

Judging by what's come up during several years of US bike and woodwork forum watching though there doesn't seem to be a simple fix. Lots have their pet cleaning regimes/rust killing products, but pretty much all seem to come down to hitting it with a rust killer, then busting a gut with a abrasive pad and then polishing - with various wash downs along the way. There's an electrolysis based method too which might be a good move for small parts.

It's fairly clear too from the posts that there's stuff out there that's much more corrosion prone than other apparently similar stuff...

If the situation is bad most of these may entail a total strip down to get at stuff/enable rinsing - although the machined/bare metal surfaces are often accessible. So it's probably one of those situations where prevention is a lot easier than the cure.....

 

[Richard T]

Since my dad built his shed in the early 70s, he has been warming the lathe, and pillar drill with 40w lightbulbs under plastic sheets. This keeps the temperature of the machines more constant than otherwise and has worked very well for all these years. The bulbs hardly ever go as they are never switched off.
Probably not the most energy efficient system though ....

 

[LynnJ]

On the subject of dehumidifiers having fairly minimal capacity at low temperatures, there was an article in the January 2011 'The Woodworker' magazine that touched on this (Shop notes page 52).
Basically conventional dehumidifiers don't work below 10 to 15 deg C but a new type of dehumidifier on the market works down to 1 deg C.
In the article Keith Smith recommends the 'X-Dry' dehumidifier for workshop use (£184 inc delivery from http://www.breathingspace.co.uk).

Lynn

 

[ondablade]

Ta Lynn, that one is right on the nail for me. I have a domestic model and found that out the hard way that it's not much use, so I'll be doing a bit of digging on their kit.

I got caught because it never struck me that a domestic unit couldn't be set to the required %RH (they actually seem to use some sort of pre-set dew point system, and the refrigerant is such that the capacity falls away rapidly below normal domestic room temperatures).

Yet it's common enough to find people talking of using domestic dehumidifiers to kiln dry timber in the US, with the only caveat being that you can eventually run into problems with dust and corrosion caused by acidic compounds from the wood. Don't know if they are talking sunshine, but maybe they get the sort you have listed.

EBAC do dedicated woodworking specific models which control to a %RH set point I understand (which is what is needed), but they are pricey at up towards £1,000 I seem to recall.

The other option is possibly some sort of modular air conditioning unit, but not having looked am not too sure what their capability might be.

 

[hunggaur]

Hi carl as requested details of my workshop roof. cheap and condensation free.

hope it helps

jon

 

[myturn]

My workshop is in a detached garage which is unheated and has a flat roof with fibre-glass insulation between the roof and a plasterboard ceiling.

I rely entirely on a dehumidifier which has a permanent drain directed to the outside. No need to empty its container and I have it on a timer switch so it runs for 2 hours every 2 hours. I did have it running permanently but that almost doubled our electricity bill!

I have no problem with condensation although sometimes in very cold and wet conditions the inside of the windows can get wet. But the tools and machinery are all kept in perfect condition and I never have a need to use anything to protect bare metal surfaces.

 

[Eric The Viking]

+1 for the don't ventilate when you're not in there thing.

We had our workshop, er, garage roof done in the summer. It's now corrugated aluminium on top of 3" Rockwool-type insulation, on top of the original corrugated steel (coil-coated) roof. It's made a huge difference to the temperature in there, BUT I haven't yet plugged all the draughty holes.

So after the December freeze, once the outdoor temperature warmed up, guess what? Condensation on the roof again! Sigh.

But as explained, it's simple physics: The roof inside was cold, and insulated from the sun warming it, and below the dew point of the moisture-laden outside air. Once I've got it reasonably draught free, I'll be able to keep it drier than outside, and any tendency to rust will stop. Right now, all machine tables, etc are heavily covered with lubricating wax and then a weighed down bin liner. So far, it's worked pretty well.

Heating: try these from Toolstation:



If you want less power (15W or 30W is probably sufficient under a machine in a draught-free space), you can get smaller ones, or buy two of the ones above and wire them in SERIES (don't try this unless you know how to do it safely).

For some years we had a 30W tubular heater fixed to a board lying on the floor under the church's grand piano. It fixed the tuning drift problem, by stopping the worst of the cooling down in the winter and controlling the humidity, as the space was only really heated on Sundays.

There's no functional difference with an ordinary incandescent light bulb (apart from the unwanted light output). Using light bulbs would be a very good approach, if it wasn't for the idiotic rules stopping us having real bulbs now (don't get me started - politicians should be forced to read "Physics for Dummies" and get tested afterwards). You'll struggle to find something suitable now, but basically, the bulb wattage is it's HEAT output (the light power emitted is negligible in comparison). They'd probably work better than a tubular heater actually, because the small hot surface area would encourage convection more.

Having Googled, I can't find the low power ones any more - the smallest now seems to be 60W, which is probably overkill. You could use a 15W or 30W cheap soldering iron, I guess, but you'd have to put it in something to protect it from sawdust and avoid a fire. Hmm, 22mm copper pipe might do...

... wanders off, muttering something about a 'cunning plan.'

8)

 

[doorframe]

Hi.

My shop is 33ft x 11ft. All wooden constuction inc flat felted roof. It has a cold concrete floor, there is no insulation and it is ventilated. It had major condensation problems at first. My solution was more like using a sledgehammer to crack a nut. I have an old electric 1Kw electric fan heater (from the old greenhouse so rugged and water resistant) at one end, and a basic 16" desk fan at the other end. They run 24/7. I have hard wired the fan on the heater so that when the stat kicks in the fan keeps running so keeping the air circulating. I have absolutely no condensation and no rusty tools, and it's always a very comfortable temp, even in the recent heavy snow. Good thing also was the snow couldn't settle on the roof as it just melted. I know it costs me around £100-£200 per winter but I consider it money well spent.

Roy

 

[ondablade]

Must say I agree Roy - I put in rads hooked up to the household oil fired boiler this Autumn. Quite apart from not having to worry about corrosion it's such a pleasure to walk into a comfortably warm workshop. Well worth the cost!!!

One other heating related issue that is probably an important factor where condensation is concerned - and which may explain some of the different experiences reported here. If you have either a fire/stove or a forced draught oil boiler like mine it's going to drive a fairly decent rate of air change in the room. By drawing in outside air to replace that that goes up the chimney.

I've not looked at the sort of cfm a boiler or enclosed stove may move (it may not be that much), but for sure anything equivalent to an open fire will change the air in the workshop very quickly. Which I suspect may greatly increase the amount of heating and/or air conditioning (%RH/humidity reduction) needed to prevent condensation and/or deliver controlled room conditions for conditioning wood. This is another reason I think why my dehumidifier has struggled to control the humidity in my workshop.

My oil boiler is located in the workshop, but could easily have been placed in an adjacent room too only it wasn't an issue on the agenda back when it was installed. If I can figure out a method the burner won't object to I'll probably set it up to draw it's own air via a duct from outside the workshop to get over the problem of its filling the shop with cold/humid outside air.

This should also isolate it from any changes in pressure caused by the fairly powerful dust system I'm presently installing.

If I had an open fire like stove I'd at least want to switch to one of the more or less enclosed cast iron types that draw only the amount of air required by the combustion - once the airflow/draw gets established in the flue (after it heats up) the open type will draw far more air from the room than is required by the combustion alone.

Ideally though it's probably best to place any sort of boiler, stove or fire needing an air supply in an adjacent room, and heat indirectly using radiators or the like. There's a lot of discounted Quinn radiators around these days since the company went into administration - over here anyway. Stripped out used items are anyway easily picked up from a plumber who will normally be more than happy to avoid having to dump them...

 

[devonwoody]

At the beginning of this winter I got out some of my timber stock and stacked it on top of my cast iron tablesaw top.
Then covered it with a plastic sheet (to keep the condensation drips off ) and as soon as the spring weather arrives and extremes of temperature finish I am hoping that the top is not going to be quite as rusty as previous years.

 

[myturn]

At the beginning of this winter I got out some of my timber stock and stacked it on top of my cast iron tablesaw top.
Then covered it with a plastic sheet (to keep the condensation drips off ) and as soon as the spring weather arrives and extremes of temperature finish I am hoping that the top is not going to be quite as rusty as previous years.

I hope so too, but I suspect it could be even worse. The wood will absorb water that is in the air and then deposit it on your tablesaw top.

On occasion I have sawn wettish logs on my bandsaw and neglected to pick up the offcuts from the table and the next day the top was already stained from the wood and had to be cleaned up with wet-and-dry.

 

[devonwoody]

I will let you know, it minus something down here at the moment so I am not going to expose the tabletop until it warms up naturally.

btw the timber was around 11% when it went under the plastic, dont know how much it can hold?

 

[jimi43]

I wouldn't have said that storing stock on top of the cast iron table is the best idea in the world but you may very well have stumbled upon a new method. Perchance the heat of natural decomposition kept it warm! :lol:

Or...more likely...it didn't! :?

I would be interested to know the result of this experiment! 8)

Jim