The Sinking of the Vane Tempest Colliery)
This new winning, consisting of two pits, known as the Vane and Tempest pits, is being sunk for the purpose of winning and working inland and undersea coal lying on the north side of a large fault which intersects the Seaham Royalty, practically dividing it into two equal portions. The fault, which runs in an easterly and westerly direction, is a “dipper” to the north. In the vicinity of the Seaham Colliery it has a throw of 105 feet, while near to the coast it has a throw of upwards of 600 feet. The coal measures dip normally to the east at the rate of about 2 inches per yard. Between the new winning and the fault the measures dip in a southerly direction 9 inches per yard or thereabouts.The site of the new winning is 350 yards west of high water mark and 70 feet or thereabouts above this datum.
The following workable seams will be passed through in the pits:
- The Five Quarter … .251 fathoms from the surface–1506 ft
- The Main Coal ……… 278 fathoms from the surface–1668 ft
- The Maudlin ………….287 fathoms from the surface–1722 ft
- The Hutton…………… 309 fathoms from the surface–1854 ft
- The Harvey ……………336 fathoms from the surface–2016 ft
Maudlin and Hutton Seams have to some extent been worked to the Seaham Colliery. Workings were abandoned some years ago for economic reasons.The new pits will be 200 feet apart, each having a finished diameter of 21 feet. The south, or Vane pit, will be the downcast and chief coal-drawing pit.The north, or Tempest pit, will be used as an upcast, also for the raising and lowering of the workmen and for coal-drawing.
The first sod was cut by Lord Castlereagh on December 19th, 1923. A trial borehole was in the first instance put down to prove the thickness of the water-bearing strata, which was found to be 485 feet, of which k25 feet consists of magnesian limestone with 40feet of sand between the base of the limestone and the coal measures.
The water met with in the foring was found at “sea level” to be salt and that it altered in level to an extent of 3 feet with the rise and ebb of the tide, thus indicating that the fissures in the limestone communicated with the sea. Having regard to the large feeders of water likely to be met with in sinking through the Permian formation, also the nature of the yellow sands as disclosed in the trial borehole, together with the close proximity of the winnings to the sea, it was decided to freeze the measures.
A contract was entered into with Messrs. The Trefor Boring Co. and the Franco Belge Freezing and Sinking Company (both Belgian firms), who are acting jointly as Contractors for boring and sinking through the Permian formation into the coal measures For the purpose of freezing, 33 boreholes were decided upon for each pit, 32 being spaced out at regular intervals around an outer circle of 30 feet diameter for freezing purposes, the remaining hole being bored in the centre of the pit for inspection purposes during the process of freezing.Prior to the boring the pits were sunk 39 feet 6 ins. in diameter to a depth of 16 feet for the purpose of fixing guide tubes for the boring and to admit of connections for freezing tubes with the necessary valves, etc.
A concrete platform was laid around each pit at the surface level having a radius equal to the full length of the boring derricks and their engine houses. Five concentric rings consisting of flat-bottomed steel rails were partly embedded in the concrete at regular intervals to facilitate the removal of the derricks from one hole to another. Three boreholes are bored at one time.The boreholes were bored from the surface with an 8 in. diameter H-shaped chisel provided with chambers on either side through which the boring water could be discharged.
The rods attached to the bits were hollow, having an inside diameter of 2 inches to allow passage for the flushing water.The water used for flushing purposes was pumped from the sea by a turbo pump placed upon the beach. The water used in boring rarely appeared on the surface, evidently disappearing in the fissures.The 8 inch diameter holes were bored to as great a depth as was possible (generally about 300 feet) when they were altered to holes of 6 inch diameter.
The holes were lined with steel tubes which were afterwards withdrawn to permit of the insertion of the freezing tubes. With the exception of the centre hole all holes were bored to a depth of 535 feet, thus penetrating into the coal measures 50 feet.The greatest distance bored in one shift of 8 hours was 150 feet. The average rate of boring, including the insertion of the tubes, was approximately 42feet per day of 24hours.Boring operations around the Tempest pit began on October 29th, approximately 42feet per day of 24hours. Boring operations around the Tempest pit began on October 29th, 1924 and finished on September 9th, 1925.Boring around the Vane pit commenced July 1st, 1925 and finished February 11th, 1926.For the purpose of freezing, as each borehole was completedan outer tube 5 inches in diameter with the bottom end sealedis lowered into the hole.
Inside this tube is inserted another 2 inches in diameter with the bottom end open. These two are coupled up to cast iron collecting pipes with branch pipes and valves which encircle the shaft in the freezing cellar. The collecting pipes are coupled up to the intake and return pipes to and from the refrigerating house.After the insertion of the freezing tubes the lining tubes were withdrawn from the holes.The freezing machinery is in three units, each unit consisting of steam driven double acting compressors with ammonia vaporisers and condensers.
The total freezing capacity of the three machines is 450,000 negative calories at 20 degrees Centigrade. The freezing operation is as follows :-The brine, consisting of .25 solution of calcium chloride which- has been previously cooled, is pumped into the intake main by double acting steam pumps. It passes down the inner tube in each hole and returns through the outer tube, extracting heat from the strata in its passage. The brine returns to the vaporisers, in which are placed coils containing ammonia liquid which vaporises at a very low temperature, where it is cooled and returned to the boreholes.
The vaporising of the ammonia is obtained by means of gas pumps which create a depression causing vaporisation. The ammonia gas is pumped through a water cooler serpentine where it is liquified and returned to the vaporisers.The freezing of the Tempest Shaft was completed and sinking operations commenced l6th February, 1926. The shaft was sunk from the surface to within 10 feet above water level, 26 feet in diameter, to admit of walling 18 inches in thickness.
A water garland was laid at this point and the walling carried up to the surface. The space behind the brickwork was carefully packed with boiler ashes. At a depth of 48 feet a large cavity was encountered in the limestone which crossed the shaft and exposed the freezing tubes on the north and south sides.This was filled up solidly with concrete to prevent any surface subsidence. Upon completion of the walling, sinking was resumed, the shaft now being approximately 23 feet in diameter. The ground was found to be well frozen and the sinking quite dry.
At a depth of 109 feet the first cast iron tubbing curb was laid and the tubbing built upon it up to the walling.The cast iron curb was of the box section, 1 foot 9 inches wide by 10and a half inches deep, the metal being 1 and three quarter inches thick with the necessary strengthening ribs. 16 segments form a complete circle.The tubbing is 2 feet deep, likewise 16 segments forming the circle of the shaft.
All the courses were laid upon yellow pine sheeting 3/8th of an inch in thickness and the full width of the tubbing flanges. Sheeting was likewise inserted in the vertical joints.As the tubbing was built up the: space between it and the wall sides was packed with sand and gravel from the beach. Upon completion of the tubbing all joints were wedged with pitch pine wedges, until a chisel could no longer be inserted.Sinking was again resumed, and the shaft tubbed and wedged in four more stages, as described above (with the exception that the space behind the tubbing was filled with concrete) until the position of the main wedging curb was decided upon.
The sand was found to be frozen a compact mass, and was sunk through as ordinary in strata. A suitable bed for the main curb was found at a depth of 585 feet from the surface, or 50 feet below the bottom of the boreholes.The bed for the curb was carefully dressed and levelled and the first curb laid upon it. This curb was similar to those already described. The space between the back of the curb and the wall sides was closely packed with timber, the grain running vertically.
This was wedged with pitch pine wedges until a chisel could not be made to enterThe shaft sides were next shorn back to admit the main curb, which was 10 and a half inches deep by 2 feet 3 inches in width, 16 segments forming the circle of the shaft. The metal was 2 and a halfinches thick with suitable strengthening ribs. Yellow pine sheeting was laid upon the curb already laid, and the main curb placed upon it. Timber as before was packed between the back of the curb and the wall sides, then carefully wedged, the tubbing was then inserted in the ordinary way. The time occupied in sinking, wall, and tubbing this portion of the shaft was six and a halfmonths.The total depth of tubbing is 516 feet, the thickness of metal varying from 7/8ths of an inch at the top to 2-l/8th at the bottom.
The thickness increases l/8th of an inch every 20 rings. Special rings for carrying buntons for supporting rising mains, etc, are fixed in suitable positions. The total weight of tubbing is 1,880 tons.The thawing of the ice wall was commenced by Messrs.The Franco Belge Company, on April 1st, 1927. This consisted of circulating brine warmed by steam through the freezing tubes. A contract for the remainder of the sinking below the frozen ground has been entered into with Mr.H.Woodfield, of Messrs,Howard & Woodfield, and sinking resumed March 1st, 1927. The depth of the completed shaft is now (May l6th) 96O feet.The rate of progress below the frozen ground, including the insertion of nine inch brick walling, averages 8 feet per diem. The thawing is practically completed and the theoretical pressure of water due to the static head is now registered upon the gauge fixed in the tubbing. The sinking was delayed six months owing to the strike.The Vane shaft is now frozen, and all necessary erections completed for the sinking which will commence on May 17th,The headgears, which have been erected by Messrs. HeadWrightson & Co., are of the lattice girder type. Theheightfrom the surface to the centre of the pulley wheels is80 feet. The permanent pulleys will be 18 feet in diameter. The winding engine at the Tempest pit is temporary. It consists of two cylinders 26inches diameter, with 5 feet stroke.The drum is cylindrical, and 10 feet in diameter.The winding engine at the Vane pit is permanent, and erected by Messrs.Robey & Co., of Lincoln. It consists of a pair of 32 inch cylinders, with 72 inch stroke.
The drum is temporary, 14feet in diameter. The permanent drum will be semi-conical, with diameters varying between 14feet and 21 feet. The crab engines are built by Messrs.Worsley Mesnes. of Wigan, each having two heavy cast iron drums 3 feet 6 inches in diameter, with worm gearing and two cylinders 11 inches diameter by 10 inches stroke.The boilers at present consist of 4Woodeson patent water tube boilers, each capable of evaporating 20,000 lbs. of water per hour. The stokers are supplied by the Underfeed Stoker Co., and are of the forced draught type.Two of the boilers are fitted with Woodeson’s patent superheaters, and a Green’s Economiser has been placed in the main flue leading to the chimney.The chimney is 200 feet in height by 10 feet in diameter.
The boiler plant is laid out so that another economiser may be added, as also induced draught, if necessary.The water softener is of the “Becco” type, capable of treating 8,000 gallons of water per hour; the hardness of the water is thus reduced from 22 degrees to 4degrees.Ventilation in the sinkings is produced by two “Sirocco” fans, having a capacity of 15,000 cubic feet per minute, at a water gauge of 10 inches. They are electrically driven by motors 25 horsepower, each pit having a separate unit, the air tubes being of steel 24inches in diameter.The power station is at present erected of sufficient size to house one of the permanent fan engines, and a generating set of 100 k.w., by Messrs.Metropolitan Vickers. The turbine is of the high pressure type, taking steam at 140 lbs. per square inch at the stop valve. Speed 2,400 r.p.m. Alternator direct coupled 2,750 volts, 3 phase, 40 periods, cooled by enclosed ventilated system. Multiple jet condensing plant with motor driven air and extraction pumps.
The switchboard is of the drawout truck type.The house will afterwards be extended to contain a duplicate fan engine, two air compressors, and probably two exhaust steam driven turbines.The power station is linked up with the station at Seaham Colliery, and will subsequently be also linked with the plant at Dawdon Colliery.A cooling tower has been erected of the Premier Cooling and Engineering Coy.’s type, capable of cooling 230,000 gallons per hour from 100 Fahr. Height of tower 70 feet.A railway connection has been made with the L. & N.E.R. near to Hall Dene. By this means practically all the material required for the new sinkings is being delivered.A railway will shortly be constructed on the south side of the new winnings to connect them with the Seaham Harbour docks, at which the shipment of the coal will be effected.