< Boiler Repairs 2 >
This time I spent three holidays for the boiler repairing. I started from the inner firebox. In order to avoid damages of the healthy parts, I prepared a shield for the tubeplate and a disc for the firehole made from copper.
First I tried to do with a large propane gas torch. However, when I blew whole flame into the firebox, a misfire happened due to a lack of oxygen. Therefore I employed oxygen-propane torch for the inner firebox repair. So as to prevent partial overheating, I started with turning the nozzle to warm whole forebox and finally concentrated on the sick point.
The forth pressure test was done. It was the first time of applying pressure by the handpump but limited to 0.8MPa due to immediate drop by leaks. There are leak point at lower part of the inner backplate near the previous leak point. And in the right side, two of inner sidestay heads and different two of outer sidestay heads have leaks. I ignored leaks on outer firebox and concentrated on repairing the inner firebox.
I repaired the inner backplate. In order to avoid new leaks around the current leak point, I spread the solder along the joint.
The fifth pressure test was done. Also with 0.8 MPa pressure, I found leaks at three sidestays in the right and one sidestay in the left in the firebox. In addition, upper point of the right side flue has a new leak.
I repaired the leak points in the firebox and do the sixth pressure test. This time the pressure could be raised to 1.0 MPa. Now the upper point of the left side flue, a tube under the flue and some rivets around them have new leaks. As for the sidestays, there are new leaks at the different two stays from the before.
First I repaired flue, tube and rivets. At the time the oxygen gas cylinder became empty. So I gave up repairing the inner firebox in this time.
In the seventh pressure test, the leaks from flue and tube stopped, but a new leak appeared between the tubeplate and inner wrapper. And a front stay, too. Regarding the sidestays, the leak points increased to six in the right and three in the left. Since the condition becomes worse and worse, I decided to repair all of the soldering point in the firebox next time.
With the rest of the time, I repaired the outer firebox.
I tried anti-heat gel for the backhead. I applied it around the backhead and around the healthy bushes. However it has the same problem as the ceramic sheet. It wastes heat from the flame and block temperature rising. Finally I removed it during the repairing operation.
The eighth pressure test was done. This time I checked only the outer firebox. In the top line of the right sidestays, five out of seven stays have leaks!. Finally I found that the protrusion of the stays are lower than other lines. I guess the repeat of heating deforms the firebox and withdraws the sidestays from the outer side plates. The sidestay's outer end has a fine step to induce solder. So The pulling increase the gap around the stay. Moreover the backhead has many leaks. Here time is up.
I borrowed a testing hand pump from a club member. It contains large hand pump, pressure gauge, two stop valves and pressure release valve. It will make the following pressure tests easier.
One week later, with a filled oxygen gas cylinder, I restarted inner forebox repair. I repeated four soldering operations for front, back, right and left to apply solder to all of tubes, flues, stays and joints. However I could not stop leaks. Speaking of outer firebox, the sidestays in the right side top line became unable to stop leaks with any repairing operation. The pressure tests reached to 10th. Here I stopped repairing operation and started devising a strategy.