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Technical Shafts

Section under repair

Contents:

 

Introduction

There were two shafts at Pleasley colliery, each 14 ft (4.42 m) diameter and 95 yds (86.9 m) apart. Although aligned on a NE-SW axis they were referred to as the North and South shafts.  The North shaft was originally known as the Florence shaft and the South as the Nightingale shaft [1] but at some point later the North shaft began to be referred to as the Nightingale and the name Florence disappeared.

They were both originally sunk to a depth of about 520 yd (475.5 m) with pit-bottoms constructed at the Top Hard seam level at about 514 yds (470 m) .  The Top Hard seam had a gradient of about 1 in 12 at this point and there would have been a difference in depth of around 24 ft (7.3 m) between the two shafts, with the North shaft being the deeper of the two. 

The upper portions of both shafts were lined with English type cast iron tubbing to hold back the heavy water feeders encountered whilst sinking. As at many other collieries using this type of tubbing, it was not entirely successful, usually as a result of the acidic water rotting the thin wood strips used to caulk the joints between the individual segments. Between 1891 and 1917 there were 3 occasions when water broke through in the South shaft and stopped work.  In June 1917, after work was again stopped for two days, it was decided to pump concrete behind the tubbing - at an estimated cost of between 1,000 & 1,500

The shaft pillar (the block of coal left unworked to avoid subsidence affecting the shafts) was 260 yds (238 m) broad by 800 yds (731.5 m)s long but it would appear that this was insufficient since it was reported that:

    “creep came on so seriously that great fears were entertained that the shaft would be lost. The pit bottom arching had to be put in three times, finally with layers of oak and brickwork alternately” [2]

Deepening

In the summer of 1919 the downcast shaft was extended past the Dunsil seam to 550 yds (502.9 m) and the deepening of the South shaft was commenced. The Blackshale seam, at 903 yds (825.7 m), was reached in December 1920 and inset arches were constructed at the Deep Hard, Low Main and Blackshale seam levels. After short exploratory headings were driven to evaluate the coal, it was concluded that the two lower seams could not be mined economically at that time.  Their insets were bricked up and a pit-bottom was constructed to service the Deep Hard seam at 769 yds (703.2 m).  A small inset was also constructed  about 60 ft (18.3 m) below the Deep Hard level and a steep narrow drift was driven from one of the pit-bottom roads down to the inset. A triple-throw electrically driven pump was then installed and the rest of the shaft below this point was used as a sump for shaft drainage and water pumped from the workings. At some point the lowest 115 yds (105 m) of the shaft was filled in.

Cages

Coal was wound from the Top Hard seam on multi-deck cages. The North pit was originally the only coal winding shaft and this shaft was configured for two-deck simultaneous loading.  Until about 1907 a two-deck cage with 2 tubs per deck was used but with the increased power available from a new winding engine installed in 1905 it was subsequently decided to install a four deck cage whilst retaining the two-deck loading.

After 1888 the South shaft was converted to coal winding. Two deck and then three deck cages were installed, with one tub per deck and single-deck loading.  In 1900 this shaft was upgraded to full coal winding and two-deck simultaneous loading arrangements with two tubs per deck were installed there [3]. 

Following the deepening of the South shaft in 1920, a three-deck cage with two tubs per deck and simultaneous loading of each deck was operated [4]. 

After the modernisation in the 1950’s, both shafts had two-deck cages with one mine-car per deck installed and the shaft-tops and pit-bottoms were converted to single-deck loading.

Ropes

In the 1800s the winding ropes were made from plough steel with a round stranded construction.   These were replaced by steel locked-coil ropes in the South shaft in the early 1900s [2] and at some time later in the North shaft.

A balance rope hanging between the cages helped to equalise the load and reduce the starting torque on the winders although these do not appear to have been employed at Pleasley prior to 1921 when one was installed at the North pit after larger detaching hooks had been fitted.  A balance rope may have been  fitted to the temporary winder installed at the South pit  in 1922 and when coal began to be wound in three deck cages from the Deep Hard seam at the South pit in 1923 a balance rope became essential.

Guides

The cage-guides in the North shaft were made of wood, four per cage. These worked quite satisfactorily, although breakages sometimes occurred and on one occasion, following renewal of some of the guides, the descending cage became stuck until the weight of the slack rope above freed it. The cage then plunged down the shaft, breaking the rope and crashing into the pit bottom. The wooden guides were finally replaced by steel rails in the 1950s modernisation (but see B.Brewster’s article in 2011 News-letter re another incident)

The South shaft originally had rope guides suspended from the headframe and tensioned by cheese-weights in the sump [3].  During the deepening of the shaft it was realised that these would not be adequate for winding from the deeper seams and were replaced in 1922 by pairs of steel guide rails running down the centre of the shaft [5].

NB it is popularly believed that there was a bend in the S shaft and  that was why guide-rails were used  - this seems doubtful, however, since the shaft guides were plumbed during installation and would have been corrected if any subsequent movement were found to have occurred.  It would appear that a more likely explanation could be found in the presence of the Dunsil inset discharging large volumes of ventilation air into the shaft from one side as well as the natural oscillations that are set up in the winding ropes due to the pulsations produced by the winding engine.

 

References

  1. Mansfield and North Notts. Advertiser, Feb 1879
  2. Longden, J.A. Trans. Chest. Inst. Min. Eng. 
  3. Longden, G.A. Trans. Fed. Inst. Min. Eng.,  1906
  4. Jrnl. Assoc. Notts. Mining Students  1923
  5. Stanton Ironworks Co. Technical Reports, Derbyshire County Records Office

Bibliography

  • Colliery Guardian 1892
  • Hughes H.W., A Text Book of Coal Mining, 1901
  • Caleb Pamely, The Colliery Managers Handbook Vol 1, 1904
  • Stanton Ironworks Co. Minutes, Derbyshire County Records Office

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