High Temperature Cable (Wire Rope) 2

[jamesjm]

Hello everyone.

I have a large utility boiler and I need to lower a large piece of steel safely to the bottom. The load that I am lowering is about 400 pounds and the furnace temperature is about 2500 - 3000 F. Does anyone have any experience or know of any type of cable out there that is used in furnaces or ovens?

 

[Goahead]

No iron base cable or chain can stand a temperature so near the melting point. Even the large piece of steel risks to melt down. Are you sure of your data?

http://www.welding-advisers.com/

 

[metengr]

Typically, we don't move steel inside our boilers when there is fire in the primary furnace or when the unit is on-line producing steam! Even if the boiler trips or is taken off-line for maintenance, you need to cool the furnace for safe entry. Sounds to me like steel is being moved external to the boiler. If this is the case, the furnace skin casing and refractory will protect regions external to the boiler.

Depending on how well your boiler is insulated, external temperatures adjacent to the boiler setting should run no hotter than 125 deg F.

 

[jamesjm]

I will explain more. We have a sootblower lance stuck in the furnace and it is bent 90 degrees downward so there is no way to get it back out through the port. At another plant in our system a lance broke free and caused a tube leak on impact. The idea is to attach a high temperature cable to the lance on the outside of the boiler and then shove it into the furnace and lower it down quickly with a tugger. I only need the cable to withstand about 60 seconds of heat in the furnace.

 

[unclesyd]

The hottest I've seen cable used for short periods of time was around 1200°F for very short periods and light loads. As you get up in temperature the use of high temperature chains is common in the heat treating industry. The hottest I've seen them used is handling parts around 2000°F for short periods.
As stated above nothing will last at those temperatures, much less a cable with the fine wires. I look at my information on ceramic coatings for steel but all of them crap out way below your temperature.

We have a Thermal Reduction Unit that operates in you range, but the first metal penetration of the refractory is only when the temperature gets below 2500°F and even then we use air or steam purge.

Could you put water, air or steam on lance to lower the temperature until a more opportune time?

What type boiler do you have that operates at these temperatures.

 

[MikeHalloran]

Maybe you could get a cable to last a minute by firesleeving it, i.e. encapulating it in a thick silicone hose, or maybe a firehose with water flowing through it.

That unfortunately, increases the risk that the assembly will snag on the snatch blocks.

You might want to mock up everything but the fire outside and practice the operation a few times; I can imagine a lot of bad outcomes.



Mike Halloran
Pembroke Pines, FL, USA

 

[metengr]

Don’t waste your time. Leave the stuck sootblower lance alone with no air or steam flow. It will eventually burn off or oxidize away. We have had stuck sootblower lances in our boilers over the years and I have never heard of anyone trying to attempt what you propose.

 

[jamesjm]

Thanks everyone for your input. The boiler that I am talking about is a Foster Wheeler Once Through Supercritical. It is a 900 MW unit with a max feedwater flow of 6.6 million pounds/hour.

 

[Metalguy]

I don't see this as such a big problem--*if* you can lower it quickly but under control. I'd use a stainless steel chain in a fairly large size. Every foot you can lower it (assuming the chain would fail) would reduce the impact at the bottom.

I'd determine how far you need to lower it and make sure the tug driver slows way down just before it reaches bottom.

If you leave it there you run the risk that it may drop at some point.

 

[Tofflemire]

Hi All,

I have to ask who is the poor fool that will be working above this furance with all that heat flying out the top? What kind of suit will this person be wearing?

You could not pay me enough to even try this...

Tofflemire

 

[metengr]

Pay? Our safety director would have my job if I recommended doing this with a supercritical boiler on-line.

 

[Tofflemire]

Hi Metengr,

What will be 2500 F if this furnace is off line? Why do you need a cable to handle this temperature if the furance is ambient? If there is something that is still 2500F? Then the heat is going up a you if open the top access port.

Tofflemire

 

[NickE]

Tofflemire- My father always likes to tell the story of cleaning the soaking pits at Great Lakes Steel. They gave them 18" thick chunks of wood to put under their boots to keep them from melting. When the wood was charred down to nothing you could have a smoke, get a salt pill, drink of water, and some new wood blocks.

IE: It costs lots and lots of money to cool something to ambient, so usually things are worked on hot. (I dont know anything about this application however.)

Are steel ladles in mills still re-lined when cherry red? Ive seen films that my grandfather had where the machines would be used to bust out the old lining and then guys in the silver suits would put the new lining in.

(Hot metal is soooo cool!)

 

[metengr]

Off-line (boiler fire out) is how it should be done, not on-line. The original poster wanted to do this operation on-line. Take the boiler off-line, cool for 12-16 hours, open the inspection door(s), sling the stuck blower lance and lower away.

 

[jamesjm]

We just cannot afford to wait for it to burn up and fall off on it's own. There have been a couple tube leaks in our system from sootblower lances falling and causing tube leaks on the bottom ash slope. We are good enough to have very long runs between forced outages, so waiting for an outage is not an option.

This weekend we have decided to drop load a bit to get the furnace temperature down around 2200F and atempt to lower it with a 1/2" Stainless Steel cable.

 

[Metalguy]

Good luck. Keep us posted. I'd go buy a SS chain, but even with the SS cable I'm betting you make it OK.

 

[Tofflemire]

Hi All,

Thanks for answering my question. Like Metalguy, I say Good Luck and I hope you have been practicing your lasso throwing.

Tofflemire

 

[Tofflemire]

Hi Jamesjm

I was wondering how you made out this weekend with your furnace fix?

Tofflemire

 

[jamesjm]

Well, we made it through. We had the sootblower lance about 20 foot from the bottom before the cable failed and fell to the bottom ash. We're extremely happy with the effort since a lance falling from over 120 feet could have taken us off.

Thanks everyone for your words of wisdom!

 

[arto]

Is it just me, or does this sound negligent/risky?
Where was the OSHA/insurance inspector or Safety officer?
Did they say when they approved the procedure?