Following a successful survey of a failed syphon isolation valve in May 2008, see case history C1193, Whaves Brooke SW, PMP were tasked with repairing and refurbishing all 54 Lever Plug Valves on the Thirlmere Aqueduct.

Running concurrently with the planned inspections of the internal condition of the Thirlmere Aqueduct (which runs 100 miles from the Lake District to Manchester) PMP devised a repair method to return the 100 year old assets to full working operation using modern, maintenance free, materials.

Due to the age of the valves, all iron and steel components were heavily corroded rendering the valves likely to fail catastrophically into their closed position.

The vertical control rods were manufactured from mild steel hollow tubes and, although were originally protected, the current condition rendered them unsafe due to excessive corrosion.

The original mild steel counterbalance weight hangers and counterbalance lever arms were badly corroded leaving them prone to failure possibly allowing the 54″ cast ion syphon plug, weighing over ½ tonne, to drop uncontrollably onto its bellmouth seat.

The bearing linkages were manufactured from bronze and were fully operable requiring only a systematic strip, clean, lubrication and reassembly.

The casting of the syphon valve plug was analysed and proved to be in good working condition, despite its age.

Once data from the survey was analysed by the client, PMP were tasked with the refurbishment of all 54 syphon plug valves during the planned annual 4 week outages.

PMP carried out extensive R&D works into the metallurgy, and due to the risk of galvanic corrosion to the 100 year old cast iron castings, it was determined that the corroded mild steel vertical control rod could not simply be replaced with stainless steel. To reduce the galvanic series, PMP fabricated bespoke phosphor bronze couplers to isolate the stainless steel from the cast iron, and therefore protecting the valuable asset.

The schedule of repairs:

  • 2008 – 8 lever plug valves
  • 2009 – 12 lever plug valves
  • 2010 – 34 lever plug valves

In all three outages, the valves were surveyed, components fabricated, old valves removed and valves reassemble with new and refurbished components, all on time in a very tight 4 week outage and all without a single accident.