Site Records


SiteName:Nenthead: Brewery Shaft & The Nent Force Level

Nenthead
Cumbria
OS Grid Ref: NY78184350

Sub Brit site visit June 1997

[Source: Nick Catford & Paul Thorne]

Figure 2 identifies how the sources and destinations of the compressed air are interlinked. As one would expect, there are various manually operated valves to cater for different operating conditions and maintenance. The most interesting section is that surrounding the separator/receiver. The inside of the regulating valve is my conjecture. However a simple float operated valve should work here because it would not see any significant differential pressure across the top air valve; all it is doing is basically keeping the water surface at a level about two thirds up the vessel. When operating, the 'water surface' would be in a highly turbulent state as the air floats upwards out of the incoming air/water emulsion. This emulsification process would have occurred at the top of the 90 foot tall tower that used to stand above the shaft collar until 1954. Here the air was entrained with the column of water falling 400 feet down the two 12" pipes. The air inlet is described as through 'snore' holes; presumably a very apt name. A photograph of the tower clearly shows three large pipes running up it, one would be the water feed from Smallcleugh Dam with the other two pipes descending the shaft.

Photo:Figure 2
Drawn by Alan Lawrence from an original drawing by Paul Thorne

The waste water re-ascends through a 14" pipe to the reservoir at Rampgill Horse Level 260 feet above. This is about the right head needed for an air output up to 90 pounds/square inch, if allowance is made for some air remaining entrained in the wastewater, thus reducing its density.

The inside of the bottom half of the separator presumably contains baffles to aid the separation. The 2.5" pipe leaving the vessel over half way up I believe would be necessary to allow the system to self bleed during start-up to avoid becoming air locked. This pipe is open at Rampgill Level (roof level) and during normal running the head of water in it would prevent escape of air or water from its open end. About half way up the 14" return pipe is a non-return valve, presumably to prevent any possibility of the water in the pipe running back into the air inlet pipe during shut-down.

Photo:Pelton wheel driving the compressors
Photo by Nick Catford

The appearance of the arching in this engine room suggests that it was constructed in two stages, the join between the two different types of arching being slightly untidy. All the machine beds within are of cast concrete.

The large Pelton Wheel (Figure 3) is said to be 140 horsepower, made by Kilkes of Kendal and installed in 1905; there is no obvious nameplate visible now. Control is manual with a hand wheel controlling the spear.


The air compressor while still in use

Power is taken off both ends of the Pelton Wheel shaft to two reduction gearboxes, I would estimate a reduction of 3 or 4:1. All that remains is the casing of one gearbox. The gearboxes would drive one compressor each.

Photo:Figure 3
Drawn by Alan Lawrence from an original drawing by Paul Thorne

There are two compressor crankshafts remaining, one with a large flywheel attached; one is quite a bit larger than the other. Broom and Wade, Engineers of High Wycombe must have made one or both as a cast iron name plate remains. It is clear from a photograph of the machinery in use that the larger machine was a two cylinder tandem, single acting, single stage, water cooled compressor; i.e. a fairly basic design.

The workbenches and cupboards in this engine room contain various tools and spare parts as would be expected. The connecting rods from one of the scrapped compressors also lie here.

Figure 3
Drawn by Alan Lawrence from an original drawing by Paul Thorne

Figure 3 shows the generating plant which is driven by a twin arrangement of Pelton Wheels, each having an independent water supply. The right hand Pelton Wheel has a somewhat cobbled together appearance with its pipe and nozzle lashed to its left hand neighbour. It also has no cover fitted now or any remains of the fittings for one. A figure of 80 horsepower has been stated for the generator.

The speed governor mechanism is a sophisticated unit which uses a weight and spring loaded centrifugal unit to control a hydraulic valve (missing). The valve output feeds a control cylinder that operates the deflector vanes, thus able to deflect part of the water jet that will control the speed. There is an upper cylinder on the governor which has no obvious purpose.

Photo:A Pelton Wheel in the generator room
Photo by Nick Catford

The electrical output from the generator/alternator I would assume to be a single phase AC at perhaps 110 or 220 volts. One clue is the remains of four capacitors near the unit; these would not have any use on a DC system.

Further information and pictures about this site continues here

[Source: Nick Catford & Paul Thorne

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