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October 22, 1937

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Mechanical And Electrical Engineering On Tyneside

The Heaton works of C. A. Parsons and Co., Ltd., were founded in 1889 by the late Sir Charles Parsons, to permit of the development of steam turbines and high speed generators on a larger scale than had been possible at his previous works in Gateshead. These works, which at the time of their inception comprised a single workshop, patternmakers and smiths' shops, testing room and offices employing 48 men in all, have, since then, grown to cover an area of 25 acres and to employ a total personnel of approximately 2,800. We recently had the opportunity of seeing these works when a visit of the technical Press was made to various concerns on Tyneside, of which we describe this week the works of C. A. Parsons and Co., Ltd.. and the newly opened factory of Pyrotenax, Ltd.

C. A. Parsons And Co., Ltd.

The Heaton and Walkergate Works.

The heavy machine and erecting shop consists of four bays, three being 40 ft. wide by 385 ft. long, and the fourth 80 ft. wide by 416 ft. long. Bays No. 1 and 2 are mainly occupied by heavy machine tools, amongst which are several lathes capable of dealing with work varying from 14 ft. to 8 ft. in diameter. There are several boring machines of corresponding sizes, and a piano-milling machine of which the column has a horizontal traverse of 15 ft. and the saddle a vertical traverse of 10 ft. At the eastern end of No. 1 bay is an exceptionally large planing machine built specially for Messrs. Parsons. It is able to take work up to 12 ft. 6 in. wide. 12 ft. high and 29 ft. long, and machining completely assembled bedplates and cylinders. This machine is driven by a 60 h.p. motor, the feeds and power traverses being operated by a separate motor of 9 h.p. with push button control stations. Another interesting machine is that for cutting gear wheels on the "creep" system devised by Sir Charles Parsons.

The eastern ends of the third and fourth bays are largely devoted to the manufacture of electrical generators, the winding of stators and rotors also being carried out there. Opening into the north side of the shop are two vacuum chambers for drying out and impregnating the insulation of machines after winding. A Schenck dynamic balancing machine for verifying the dynamic balance of rotors at all speeds is also located in No. 3 bay.

The erection of large turbines and their running under steam is carried out at the western ends of bays 3 and 4. Provision is made for driving separately the largest alternators both fully excited and on short circuit for accurate measurement of the losses. The sets on test at the present time include an 18.750 kw. turbo-alternator for the Broken Hill Proprietary Co., Australia. This is one of two similar machines on order at the present time. The h.p. and l.p. cylinders of the first of two 30.000 kw., 33,000 volt turbo-alternators for the Calcutta Electric Supply Co., are in process of blading. There are also in course of construction certain condensing plant and various high power turbo alternators. In the armature shop are the stator and rotor of a 33.000 volt, turbo alternator for Table Bay Power Station, Cape Town, in course of being wound. The stator embodies the Parsons patent concentric conductors employed for direct generation at high voltages. The old test house contains an experimental steam turbine capable of developing about 4,500 h.p. specially constructed and equipped for the practical investigation under running conditions of the results of proposed changes in design. By means of this machine exhaustive tests of new types of blading, glands and other details can be carried out before their incorporation into commercial machines.

At the western end of the insulating shop insulation for stator conductors is made. Mica flakes are built up into sheets (with or without silk or other backing), the whole being bonded with a special insulating varnish which retains its flexibility permanently under all operating conditions. The sheets thus prepared are tightly wrapped round the conductors by machines designed for the purpose, and the complete bars after being taped are dried and impregnated in steam heated vacuum ovens. The stator conductors in all Parsons alternators are of stranded copper wire, in the form of cables, each strand being separately insulated by asbestos or cotton covering. On the cable conductor making machines near the eastern end of the shop the double and triple concentric conductors which are a distinguishing feature of Parsons high voltage alternators are made, while ordinary stator conductors can be made of any desired form, rectangular or otherwise, without the necessity for any subsequent mechanical operations. These processes have been developed entirely in Parsons' works and the patented construction of conductors has proved of great value in the construction of large turbo alternators. The manufacture of micanite mouldings and other details is also carried out in the insulating shop.

The coreplate stamping shop is occupied with machinery for shearing, stamping, dressing and varnishing the laminations used in the construction of electrical machinery. Varnishing is effected in continuous ovens through which the laminations are carried on an endless chain, emerging dry at the far end, ready for assembly into cores. In the transformer erecting shop, which is at present being extended, power transformers of various sizes are in the course of erection and testing; the welded steel tanks for containing them are made at the adjoining Walkergate works of the company. The adjoining coil winding shop is reserved exclusively for the manufacture of coils of transformers of all sizes and types and air cleaning and ventilating plant is installed and every precaution is taken to ensure cleanliness.

Manufacture of turbine blading of all kinds, not only for themselves and their licencees, but also to meet the requirements of other manufacturers, is an important part of the business of the firm. In the blade shop the processes of rolling, drawing, heat-treating, machining, etc., of the blade material, which includes stainless iron and steel, monel metal, brass, etc., are carried on. An interesting process is the rolling of individual blades, integral with their root pieces.

The overspeed test plant is housed in a reinforced concrete chamber overlaid by thousands of tons of earth work, situated well away from the workshops. The chamber consists of an L-shaped gallery in the longer arm of which the rotor to be tested is placed. It is driven by an electric motor and after balancing in the usual way, is run at the required overspeed for a sufficient length of time. For electrical rotors, the standard overspeed test is 40 per cent, above the running speed, which has the effect of doubling the normal centrifugal stresses. All turbine rotors and discs are overspeeded before blading. While such tests are in progress no person is allowed to remain within the testing chamber, the whole of the operations being carried out and the observations made by means of apparatus in a separate control room. An essential department of the works is the material test house and laboratory in which are carried out the whole of the routine, physical and chemical, tests on metals in their raw and manufactured condition, to ensure that quality is maintained and specifications are complied with.

The electrical research laboratories were constructed in 1935 to afford better accommodation and improved facilities both for routine testing and electrical research. On the ground floor of the research laboratory are carried out investigations of electrical and magnetic properties of various materials and their behaviour determined under conditions similar to those which will be met with in service. Tests of insulating materials and particularly on micanite insulation form an important part of the work. A high voltage Schering bridge for accurate measurements of the internal dielectric loss and the power factor of insulation under various conditions of voltage and temperature is included in the permanent equipment, a second portable bridge of the same type for testing the insulation of complete alternator stators and transformers being employed in the works under the direction of the department. The upper floor of the research building is mainly employed for the development and testing of relays, automatic voltage regulators, etc. The calibration of the numerous electrical instruments used throughout the works is also done on this floor.

The high voltage laboratory forms part of the research department. The equipment includes test plant generating up to 500,000 volts, both at normal frequency and under impulse conditions. The impulse generator designed and constructed by the firm, consists of a nine-stage condenser bank, each stage having a capacity of 0-25 microfarad. The condensers can be charged in parallel to a d.c. potential of 70 kv. by means of a rectifier connected to a high voltage transformer. When charged, the condensers discharge automatically in series through interstage spark gaps, thus creating a momentary potential difference up to 500,000 volts across the terminals of the generator. By means of suitable inductances and resistances, the wave shape of the discharge can be varied to suit the requirements of any particular test. For tests at power frequency, two 50 k.v.a. transformers connected in series are available to give a peak voltage of 750,000 volts.

The whole of the high voltage testing plant is operated from a control panel on an overhead gallery running along one wall, from which a clear view of everything in the laboratory can be obtained. A high speed recording oscillograph of the Finch cold cathode type is used for determining the wave shape of the impulse applied to the apparatus under test and for the investigation of the phenomena that occur during the moment of discharge.

The Walkergate Foundry.

In the castings cleaning shop the larger castings made in the foundry are fettled before dispatch. Part of this shop has hitherto also been employed upon the turning and boring of ships' tail shaft liners, and general machine work. Plans are at present in hand for the removal of this work to a more suitable site, and for the conversion of this part of the shop into an extension to the foundry.

The hard sand foundry is chiefly devoted to the larger iron castings required for turbo-alternator work. The loam moulds for these parts are made in moulding pits. The pits being truly rectangular and having cast iron sides bedded in concrete, it is possible to ensure the production of castings accurate to pattern term with a minimum of risk of failure. In these pits castings up to 15 tons finished weight have been made.

The majority of the work carried on in the greensand foundry consists of repetition work, which is carried out on moulding machines of various kinds. Some of the castings, used for electrical work, are of metal only 1/8 in. thick, a high phosphorus and high silicon iron being employed to obtain the necessary fluidity. Non-magnetic iron castings of nickel alloy are also made.

The foundry contains two cupolas, each of four tons per hour capacity, and one of two tons per hour capacity. The smaller unit which was installed in 1936 is of the balanced blast type, and has shown an economy in fuel of 20 to 30 per cent. The balanced blastfurnace which was developed as a result of research work by the British Cast Iron Research Association, has specially arranged adjustable tuyeres which provide that the combustible gases from the melting process are usefully burned to preheat the charge.

The brass foundry undertakes non-ferrous castings up to 2½ tons weight and the manufacture of tail shaft liners has long been a speciality of the Walkergate works. An excellent structure is obtained by casting vertically, and a pit in the foundry floor enables liners to be cast in this way of over 20 ft. finished length.

The welding shop is occupied with the fabrication of steel condenser bodies, stator frames, transformer tanks, bedplates, pipework, etc., for the Heaton works and for outside customers. It is equipped for the manufacture of every kind of welded steel structure, and many fine examples of such work, such as hemispherical domes up to 34 ft. diameter for large observatories have been carried out. Steel sheets from 1/16 in. thick up to plates 2½ in. thick are dealt with in everyday work and plates up to 3 in. or 4 in. thick when necessary. 24 single operator welding sets are in regular use, of which 17 are rotary motor generator sets. Only the highest quality coated electrodes are used and specimens of weld metal regularly give 28 to 32 tons ultimate tensile strength, 21 to 22 tons yield point. 25 per cent, elongation, and 60 ft.-lb. izod impact value. A rigid system of inspection is employed on all fabricated parts both dining construction and upon completion.

The principal item of interest at the present time in the optical works of Sir Howard Grubb Parsons and Co. is the 74 in. reflecting telescope for Pretoria. The moving parts of this great telescope weigh 35 tons and the whole of the delicate and highly accurate driving mechanism is made by the firm.