Infrared heater to remove bearings and couplings from rotating equipment shafts

When you say, "in the field", do you mean, literally, outdoors, probably requiring a self-contained energy source, or merely away from your home location, with AC electrical power usually available? In this second case, the equipment would still need to be portable, but could run off standard AC current with the proper extension cable. This could make a big difference in the type of equipment available.

Also, while the idea of using infrared heat may be a good one, it may not be the only available flame-less heating option. What temperatures are necessary and how isolated must the heat application be? Electric or gas powered soldering "irons" or "guns" may be equipped with appropriately shaped tips to conduct heat directly to specific parts. Also, hot air guns, such as are used to re-flow solder paste or to shrink heat shrinkable tubing may direct heat to limited areas, but could also cause ancillary heating of nearby parts as well. These can generate temperatures high enough to burn human skin, but NOT to ignite paper or other flammable materials, such as greases and plastics, although there certainly could be (desirable?) softening involved.

There are some small, high watt density electric radiant heating elements, notably of the "cal-rod" type, such as are used in electric ovens and broiler units. Check out www.watlow.com for some of these. Also, some ceramic electric heating elements are used for infrared applications. Google "Elstein heaters" for information on one brand. These are often referred to as "Soap dish" heaters due to their similarity to ceramic soap dishes used in home bathrooms.

Away from our home location, power would be available. Generally temperatures in the range of 250f. Diameters and size of the bearings vary but we could consider bearings in the range of 100-200mm ID with a weight of say 10-20lbs. Couplings could be up to a couple hundred pounds but in most cases they will have a 3-5in bore with an 8-12in OD with estimated weight of 20-50lbs.

Soldering irons are not a good option already been tried.

FYI

The heat source will need to heat the mass that is being removed fairly quickly within say 3-5 minutes. These components usually have about .001" interference fit. If they can not be heated in this time frame heat transfer will occur causing the shaft to grow thermally thus defeating the purpose of applying heat to assist with removal.

Mark. Something that may be worth trying would be using an arc welder and connect both leads directly to the item to be heated. Experiment whith the amp setting and time to find the most appropriate for heating the race or other pressed fit item quick enough to release without swelling the shaft. If direct connection of the cables don't work you could try using a rod held in the lead that is made for cutting and move around the item in such a manner as to create heat without actually cutting. If a large cutting rod is not available take a large welding rod and soak in water before using. I would suggests first trying on a scrap item till you have a feel for it. The electrical resistance should heat the item very quickly to any desired temperature. Check the ground to be sure the current doesn't flow down the shaft and cause other problems such as a path through a bearing. Proceed with caution J Conway

Have you considered induction heaters?

Is this technology already available in the industrial field? Or the plastics field?

Difficult problem removing bearings and couplings from heavy construction equipment in the field without flame was solved by using a carbon rod and a small (100 amp) welding supply (available for about $120 from tool discount houses such as Northern Tool or Harbor Freight). The current can be adjusted to match the job. The tip of the carbon rod is placed at various locations on the part to be heated. The ground cable is attached to the same part to be heated or simply pressed against the part (make sure that good electrical contact is made). A scrap of heavy copper (good heat conductor) can be placed between the surface to be heated and the carbon rod tip to prevent localized melting of the surface for heavy current settings where the carbon rod tip can become white hot. I used this method successfully many times under very adverse weather conditions.

Hi.

Put away the welders and all that stuff - not needed and more than likely detrimental.

CoronaCameraMan gave you some good advice. The typical thing for putting bearings on in the first place and recommended for removal is using dry ice or liquid nitrogen or at least an ice bath on the shaft. In some cases the bearings are also heated, but one must be somewhat careful here to ensure that they are not overheated. Heating is usually done with a radiative heater that is essentially a glorified hair dryer - and looks like one as well. Difference is that these babies can output over 700 degree air (handle with care!). Smaller ones with less oomf are also available - depending on needs and required temps. Although fine for the typical shop or garage, I would not use these in explosive environments as the elements obviously get very hot and the switches can sometimes spark. As mentioned by CoronaCameraMan, you will have an impossible time trying to get dry ice or liquid nitrogen to spark.

Some bearings are literally pressed on and are recommended to be pressed off. If you don't have the equipment to do this properly, it is probably cheaper to have this done for you by someone with the equipment rather than buying it unless you have lots to do.

What you really want to do is check with the manufacturer to see how the bearings were put on and how they recommend removal and replacement. Some of them may even have the procedures listed on their websites.

Good luck.

Using BTU input or extraction calculations will help you decide what is practical given any field situation.

BTU (British Thermal Unit) is the energy required to raise 1 lb of water 1 degree F. Materials are rated as to how much temperature they will gain per pound of material for each BTU of energy applied to them. One lb. of carbon steel will increase in temperature approximately 9 deg. F. for each BTU input into the metal. Removing 1 BTU from a lb. of steel will lower its temperature 9 deg. F. The important factors are how much heat you need to gain or lose, how much the part weights, how quickly you need to gain or lose the heat from the part, and how much surface area of the part can be exposed to heating or cooling.

For example:

If your metal bushing requires heating to 200 deg F over its current temperature within 2 minutes and the bushing weighs 50 lbs, and the specific heat of the metal bushing is 0.11 (carbon steel) then you need to transfer a minimum of 550 BTUs per minute into the bushing plus makeup BTUs lost through radiation and conduction. Assume 650 BTUs per minute total because of transfer inefficiencies, radiation and conduction losses.

If 12 square inches of bushing surface is available for thermal transfer, and thermal conductivity of steel is 26 BTUs per sq.ft. per degree F. per hour, then having a usable heat transfer area of 1/12 of a sq.ft. (guessing) gives you 2.17 BTU transfer ability per deg. F. per hour or 0.036 BTU transfer ability per deg. F. within each minute period. 650 BTU per minute required / 0.036 = 18,000 BTU per minute input over 12 square inches of bushing surface to raise the bushing an additional 200 deg. F. within two minutes.

Doubling the available heating time to 4 minutes would mean 9,000 BTU per minute would be required. Whether you are using dry ice to shrink shafts or using heat to expand bushings, you need to figure the total energy to be added or removed within the required time period and how much surface area for thermal transfer you have to work with. Looking at the problem as BTUs to be gained or lost by the metal within your time period is the best way to handle the problem.

Hello Mark

Yes thereis a device that clamps on the bearing seen up to 12inch (30 centimeter ) bearing magnetic heated using 110 volts and another using 600vac but I can't rememberthe company that made the units even though I have repaired both . Yes they work good and no burnt up motor windings because of an over zealous flame....

SKF, FAG, TIMKEN make bearing induction heaters. Also you will get the induction heaters from several suppliers. These are the most preferable method of removing a bearing.

However take care that

a) The induction heater have a demagnetisation facility

b) The fill ratio of the coil is maintained so that the bearings do not get over heated locally.

The liquid nitrogen, we as assemblymen do not prefer due to thermal shock.

A component at room temperature say 20 deg C brought to -193 deg C in seconde or less is approx 200 deg C/sec cooling rate. consider what will happen to the component, especially bearings having quite a few sectional changes and notches.

Ind Heating with bearing pullers may be your solution. Bearing manufacturer may give you the equipment with may be a couple of different coils for the range.

We are chinese equipment and tool supplier. We can supply the tool for you. Henryzhang1@hotmail.com

See website www.teamindustrialservices.com for induction heaters