Heater removal can be very difficult, if the heater has arc welded itself to the inside of the heater hole. You will continue to experience heater failure if the heater is not removed with care. When a heater is removed by drilling with a size-for-size drill, the drill will cause scallops in the heater hole,

which will cause hot spots in the heater that will allow the heater to overheat and fail. The only good way to repair this damage is to redo the heater hole by making it oversized or opening it up to the next size heater. Sometimes this is impossible. Make sure heaters are available before you open up any heater holes. Also remember that if the heater manufacturer supplies you with oversized heaters, buy some spares. This special heater will not be available for quick delivery if you have a failure.

(1) Set up the manifold so the heater hole is parallel, square and centered with a mill or drill press. Drill the core out of the heater using a cement drill that is smaller than the I.D. of the sheath. This should prevent damage to the heater hole when the core is completely removed. Use a drill that is 1/64″ smaller than the heater. Dull sides of the drill, so it will only cut on the end. Making sure proper alignment is held, drill out inside of the sheath. Use water to make sure that the drill is kept cool or it may catch and break or cause other damage.

If the inside of the sheath is removed and the heater body is still stuck in the heater hole, make a tool from an old ejector pin that is shaped like the end of an ink pen. Grind away all but one side of an ejector pin until it is sharp but substantial. Place the sharp, chisel-like end between the heater sheath and the heater hole. Tap on the end of the ejector pin forcing it between the sheath and the heater hole.

This will break the weld and allow you to remove the heater without doing any serious damage to the heater hole. Before replacing the heater, ream the hole with the proper size reamer to make sure it is clean. Apply a heat transfer media to the heater and slide it into the heater hole. Do not force. This heater will be wet from being on the shelf and should be properly dried before it is subjected to full-rated voltage.

(2) Many manifolds manufactured today use a tubular-type heater. Some of these heaters are removable and others are cast in and are not removable. The non-removable tubular heaters will have to be serviced by the manifold manufacturer. The removable type of tubular heaters are usually placed in a machined channel and held in by cover plates or some type of potting/heat transfer media.

After the cover plates are removed, the heater should be easily removed. Heaters that have a heat transfer/potting media are removed by forming a piece of brass in the shape of a round chisel and driving it between the heater channel and the heater. This will lift the heater from the heater channel.

(3) When reinstalling the heater that is held in by cover plates, place the heater in the heater channel and replace the heater retainer plates. The problem with this type of heater installation is that there is a limited amount of contact with the heater channel unless some type of heat transfer media is used.

(4) When reinstalling heaters that have a heat transfer/potting media, remember these heaters are available in a pre-bent or straight form. If you would like a pre-bent heater, order it when the system is ordered or delivery may be a problem. If you choose to use a straight-length heater you can save some time and money. The straight-length heaters are annealed and reasonably easy to bend. Start in the middle of the heater channel and work to either end. This way the ends of the heaters will be the same length when you are done. You will need a piece of hard wood, a piece of brass, a hammer, a soft-faced hammer, gloves and a helper.

Gently tap the heater into the heater channel, making sure that the heater sheath is not cut or broken. When the heater is in the heater channel, the heater should be compressed making it a (D) shape. This can be done using a hydraulic press or with a hammer and a one-inch wide piece of brass. This will give the heater full contact with the sidewalls of the heater channel. By re-potting the heater with the manufacturer-recommended potting compound, you should have a good heat sink for your heater – providing even heating and long heater life.

(5) Before removing the tubular heater, make sure it needs to be replaced. If the terminal is broken off because of a leak or other damage, the heater can usually be repaired. The termination pin on most tubular heaters is a solid pin, one to one-and-a-half inches long. The sheath can be cut away using a hacksaw to expose a new lead to which you can connect your power lead.

(6) CAUTION: Do not remove more than 0.750 of an inch from the heater sheath and remove only what is required to make your connection. Also use caution in making the termination, so as not to create a short between the sheath and the heater element.