BE PREPARED FOR A TRICKY STEAM TEST

By William Powell

Are you ready for the unexpected?

While putting a loco through a steam test the injector clack failed to seat. This happened at possibly the worst time, just after the safety valve accumulation test (blower hard on, good bright fire), during which the safety valve had performed well (Smith pop valves?). However, being sited on the steaming bay rather that the track made it easier to deal with the issue.

The 1/3 to a 1/4 of water in the gauge glass was disappearing! The key was not panicking! After  turning the blower off, I tapped the offending clack in the hope of reseating it.

I have had it before where its possible to get the injector to pick up by pouring water over to cool it. However,  the last of the water in the watering can had been used to top the injector feed up for the testing of the water feeds. So while the hand pump was steadily pumped, the witness for the steam test was dispatched with the watering can for more water.

Despite steady use of the hand pump, the water remained just in bottom nut, the fire still had a brightness. While wanting to save the steaming and possibly the test, a split-second decision was made to drop the fire.

The grate was held in by screws with knurled heads either side, not as quick as a pin to pull (possibly more secure though?), these  were unscrewed and placed on the tank top. While the ash pan dropped away the grate remained wedged in place! The nearest, longest implement was the shovel; while the heat and colour was reducing from the fire it was still hot, and with the clack still hissing away, a prod from the shovel did not dislodge it.

Another harder dig in the bottom only resulted in the shovel end falling off! A hole had been made in the fire, the only moments ago bright fire was looking mostly dark but still with dull red patches. The final act was the stuffing of a rag in the chimney, and with the blower open the remaining pressure was used to kill the fire.

The grate did decide to drop out at this point, the parts of the shovel were fished out, and as the final steam pressure  hissed away conclusions were drawn.

The whole event happened far quicker than you could have read this or I could have written it. Hindsight being what it is, the rag could have been stuffed in the chimney earlier.

I did still think after the initial event the injector could have been flooded and used to reseat the clack or at least a tap on the clack body would have reseated it.

The screws holding the grate were just able to be undone with fingers, partly due to the screws having large knurled heads, but if they had been tighter, needing a tool, more time would have passed. A long single pin being much easier!

After allowing it to cool, the offending clack top was unscrewed and the ball removed. While there was some lime scale, there was no obvious damage to the ball or seat. After the loco was checked, another attempt at the steam test was made, and this time the clack behaved.

Lessons learnt or reinforced:   

  1. Always have a bit of rag handy. Nothing kills a fire quicker than covering the chimney and turning the blower on.

  2. While the clack can sometimes be reseated, it can lead to a distraction when the fire should be dropped/killed and the clack sorted after the boiler has cooled down.

  3. While I understand some prototypes had the clacks under the fire hole door (Webb LNWR locos spring to mind), clacks above the water level are much preferred. Where this can't be achieved, put a 2nd clack in line as a fail safe.

  4. Ensure the boiler is washed out, and the water feeds have filters to remove debris that might cause a clack to fail to reseat.

  5. Don't Panic!

 
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