Post by springcrocus on Jun 11, 2021 13:14:06 GMT
I took the Allchin boiler to Broadfields last Saturday and suffered the embarrassment of water pissing out of one of the hollow stays. I had drilled the through-hole too close to the edge and penetrated the wall of the stay in the water space. I hadn't been able to check this before because the club's test rig was leaking badly back past the pump. The boiler inspector was using his own kit for this test. Anyway, deciding to kill two birds with one stone, I offered to overhaul the test rig back in my workshop, then I could fix the boiler and test it with the refurbished pump.
To fix the leaking hollow stay, a piece of 3/32" dia copper rod was pushed through the offending hole and silver-soldered into place. The ends were dressed back to flush and a dummy, blind rivet will be used in the hornplate. The photo shows that a few more are near the edge, the result of me trying to get the boiler more central than when I originally spotted through the hornplates. Another lesson learnt!
After talking with a colleague at the club that day, I also decided to purchase my own test kit. This is a plumber's pressure test kit that I bought for under fifteen quid delivered. At this price, it just isn't worth making, I expect the gauge alone would normally cost twice this amount. It's a bit rough-and-ready but good enough for just checking for leaks.
The gauge shows that it goes to 25 bar which is approximately 360 psi, so rated much higher than anything I will ever need. I've already made an adapter for the outlet to reduce it to 1/4" x 40 for one of our standard test hoses and this close-up also shows the calibration of the gauge. With a blanking cap in place, I took the pressure to 13 bar just to test it.
Meanwhile, back on the club's test kit and this is how it was beforehand. The 7/32" balls in the pump body were not sealing properly and someone had incorporated a Schrader valve in the delivery pipe to try and stop the backflow. However, this promptly made the discharge/pressure-release valve non-functional and pressure had to be released by loosening the connecting hose and spilling water all over the work surface, or wait for it to naturally leak back to the reservoir. The valve on the right is pointless on it's own as it only isolates the boiler from the test rig.
I have stripped off all the pipework, including the Schrader valve, and incorporated isolating valves at both the inlet and the outlet so that, with both valves closed, the pressure chamber and gauge can be stored full of water and doesn't need to be drained after each use. During testing, a boiler can be pumped up to pressure and the inlet valve closed. The boiler and test gauge are still connected but there is no backpressure on the pump and the boiler can be left at pressure as long as one likes. If the gauge shows a drop in pressure, then it has to be the boiler (or hose connection) that is leaking, the valve is stopping water leaking back via the pump.
I also dressed the ball seats and reseated the balls although I would have replaced them with silicon nitride balls if I had any. These weren't particularly effective, though, so I inserted a schrader valve in the lower part of the hexagon pillar, having to make a special tap to cut the thread. This way, the pressure release valve still does the job it's supposed to.
And the other bit of good news is that the previous photo is of the Allchin boiler under test and the gauge shows that I have lost only 10 psi over the last twenty minutes. Hopefully, I won't embarrass myself when I next present it to the boiler inspector for the shell test.
Steve
To fix the leaking hollow stay, a piece of 3/32" dia copper rod was pushed through the offending hole and silver-soldered into place. The ends were dressed back to flush and a dummy, blind rivet will be used in the hornplate. The photo shows that a few more are near the edge, the result of me trying to get the boiler more central than when I originally spotted through the hornplates. Another lesson learnt!
After talking with a colleague at the club that day, I also decided to purchase my own test kit. This is a plumber's pressure test kit that I bought for under fifteen quid delivered. At this price, it just isn't worth making, I expect the gauge alone would normally cost twice this amount. It's a bit rough-and-ready but good enough for just checking for leaks.
The gauge shows that it goes to 25 bar which is approximately 360 psi, so rated much higher than anything I will ever need. I've already made an adapter for the outlet to reduce it to 1/4" x 40 for one of our standard test hoses and this close-up also shows the calibration of the gauge. With a blanking cap in place, I took the pressure to 13 bar just to test it.
Meanwhile, back on the club's test kit and this is how it was beforehand. The 7/32" balls in the pump body were not sealing properly and someone had incorporated a Schrader valve in the delivery pipe to try and stop the backflow. However, this promptly made the discharge/pressure-release valve non-functional and pressure had to be released by loosening the connecting hose and spilling water all over the work surface, or wait for it to naturally leak back to the reservoir. The valve on the right is pointless on it's own as it only isolates the boiler from the test rig.
I have stripped off all the pipework, including the Schrader valve, and incorporated isolating valves at both the inlet and the outlet so that, with both valves closed, the pressure chamber and gauge can be stored full of water and doesn't need to be drained after each use. During testing, a boiler can be pumped up to pressure and the inlet valve closed. The boiler and test gauge are still connected but there is no backpressure on the pump and the boiler can be left at pressure as long as one likes. If the gauge shows a drop in pressure, then it has to be the boiler (or hose connection) that is leaking, the valve is stopping water leaking back via the pump.
I also dressed the ball seats and reseated the balls although I would have replaced them with silicon nitride balls if I had any. These weren't particularly effective, though, so I inserted a schrader valve in the lower part of the hexagon pillar, having to make a special tap to cut the thread. This way, the pressure release valve still does the job it's supposed to.
And the other bit of good news is that the previous photo is of the Allchin boiler under test and the gauge shows that I have lost only 10 psi over the last twenty minutes. Hopefully, I won't embarrass myself when I next present it to the boiler inspector for the shell test.
Steve
