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Replacing a Ludlow Pot Element

Started by Mechanic, March 17, 2015, 06:57:19 AM

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I hope no one ever needs to use the information on how to replace a faulty Ludlow element. Just in case you do, I have written the procedure we use to replace the element at Pimpama. I have never replaced a Ludlow element before, but I have replaced numerous Linotype elements. I mention that I had intended to bail the pot out. If you do this you need to be able to pour hot metal into the pot or have lots of Linotype metal slugs to get the elements covered as soon as possible, as they are not designed to operate in air.


The Ludlow pot has two elements, wired in parallel. This means that if the circuit in one element opens the other will still heat. The single element is not enough to heat the pot to a temperature that will allow the machine to cast lines of type, so the faulty element has to be replaced.
You will need a blowtorch, the old fashioned kind that uses kerosene or petrol. The heat of modern propane gas torches is too intense and tends to melt and burn the metal as soon as it melts. You need to raise the temperature gradually.

There are two methods of replacing a faulty element.

1. Turn off the power and bail out all the metal when the plunger becomes free and can be removed. You may have to keep the blow torch on to complete the removal of the faulty element. This is the method I had intended to use but we could not get a ladle suitable to do the job.
2. Remove the element when the pot is molten as described below.
The elements float when not clamped down so you need a way of holding them in place when the element clamp is removed. To do this you will need a couple pieces of timber about 25mm x 50mm and 300mm. 1"X 2"X 12". Cut a groove about 10mm 3/8" across the width at one end of the timber.  The timber needs to be dry. The groove is to stop the timber from slipping off the element while it is being held down. This can be dangerous, I have the scars to prove it.

In order to proceed you need to do a number of things.

(1) Turn off the main power to the machine and remove the element cover. It is held on by 5 allen cheese head screws. At this point it would be a good idea to spray the nuts holding the wires on the elements with WD40.  If you are not qualified you should involve an electrician to remove and rewire the elements.

(2) Lift the table and remove the felt mouthpiece wiper 805D and close the mouthpiece wiper bracket. The wiper will rest on the mouthpiece in step (5) and burn if not removed.

(3) Remove the plunger connecting lever by removing the three pins.

(4) Close the table and manually rotate the machine so that with table down you can unscrew the right hand element clamp screw.

(5) Remove the table filler piece 52A. This gives you access to the pot when the table is down.

(6) Remove the wires from the elements. You may find two brass plates connecting the elements together. Remove these and put them aside.
This was where we ran into trouble at Pimpama. When we tried to remove the element nuts two of them stripped and had to be split apart using a device made by John Setek, the third member of the print shop trio. I also had to cut one of the brass plates in half in order isolate the faulty heater prior to getting the nut splitter.

(7) Wire the good element up to the power and turn on the power to the pot.

(8) Light the blow torch and play the flame steadily on the side occupied by the faulty element.

Keep the flame away from the temperature sensing bulb. It will take about an hour and a half to two hours to melt the pot. Watch the pot thermostat when it gets to around 530 or 550 deg F the plunger will be free and start to float. Remove the plunger clean it oil the surface with Ludlow oil and put it aside so that it will not be damaged. Place the new element in the pot so that it can warm up.

This is the most difficult part of the operation.

Turn off the blowtorch and the power. Use one of timber pieces to hold the good element in place. Remove the element clamp. The faulty element will start to float. Remove it and replace it with the new element which has been warming in the pot. You will need to hold the new element down with the second piece of timber. The temperature sensing bulb will also start to float and will need to manoeuvered back into place. Replace the clamp making sure that you do not trap the tube of the sensing bulb.

Rewire the elements making sure that when element terminal cover is replaced it will be well clear of any wires. Rotate the machine to the home position.

Turn on the power and replace all the parts you have removed. Let the plunger warm up in the pot before replacing it in the well.

George Finn (Mechanic)
Gold Coast

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