Repair to the Dump Valve

As previous blogs will relate (once I get round to entering them - I am blogging most of this stuff retrospectively), we have a sort of "emergency stop" lever for the mill. It works by dropping a board out of the bottom of the launder close to the wheel, stopping the flow of water much more quickly than closing the diverter. We call this the Dump Valve.

During Sunday 19th June's operation, we found that the dump valve was not closing properly, spilling a lot of water. It then failed to open properly and stop the wheel at the end of the afternoon.

Investigation showed that there was a lot of algae and other green slimy stuff in the works, but once this was removed it became apparent that the arm that works the valve flap was not fixed securely to the operating shaft. In fact the coach screws were in soft, wet timber and could not be tightened.

The Dump Valve operating arm,
showing the rigid link

We therefore bored out the holes in both the arm and the shaft to take 12mm studding, made and drilled 2 plates from 3mm mild steel, and reattached the arm. We also removed a bit of the timber cladding where the operating lever comes through the end of the wheelhouse to allow the lever to move further.

After we had adjusted the operating chain, the valve worked perfectly until the drop board jammed in the hole.

12 July 2011 fitted a rigid arm so the lever now pushes the drop board open rather than allowing it to fall under its own weight..