WORLD'S LATEST

Evening Post, Volume CXXIII, Issue 104, 4 May 1937, Page 12

WORLD'S LATEST

EVANS BAY PLANT

VELOX STEAM GENERATOR

15,000 K.W. ADDITIONS

Towards the end of 1935 the Wellington City Council decided, only after long and sharply-divided discussion, to step out boldly in its order for new plant to add to the generating capacity of the Evans Bay power station, by purchasing a 15,000-kilowatt Parsons turbo-genera-tor and two Velox steam generators of Swiss manufacture and of altogether radical design. The huge turbogenerator, by far the largest steam unit in New Zealand, is now practically assembled, and the "drying out" of the windings by clays of running without output of power is to be commenced in a week or so. The first of the remarkable Velox steam machines is also now largely assembled, and when the tests are commenced the Evans Bay power station will become a centre of keen engineering interest and inquiry, for these two units will be the first installed for civil purposes in the British Empire.

Velox steam generators are in operation in a number of European countries, and the British Admiralty has had one under test for some time. What the Admiralty discovers by test and research it does not publish, but from European countries have come reports of the extraordinarily high efficiency and economy of this new type of steam machine under certain operating conditions—which conditions are almost exactly those which govern the operation of Evans Bay as a standby station. OUTPUT GREATER THAN MANGAHAO. The Velox steam generators must not be confused with the turbo-generator: they are boilers of-most unusual design, which produce the steam to drive the turbo-generators, the producers of electrical power. With the 15,000 k.w. Parsons turbo-generator in commission the station will have an output of 25,000 kilowatts, for there are at present in the station one 6000 k.w. and two 2000 k.w. turbo-generators, and Evans Bay will then have an output greater than that of Mangahao and an elasticity in operation not paralleled in any other steam station in Australia and New Zealand and probably in the Southern Hemisphere. There is a third new unit, a 600 k.w. Diesel-driven generator, but this will not supply power to the city, but will be used to supply power for the station auxiliaries—pumps, motors, etc.—when the normal power supply is interrupted.

Each of the two T/elox steam generators is capable of supplying steam for the production of up to 7500 k.w. of electrical power, so that together they will drive the great 15,000 k.w. Parsons set, or singly each will easily look after the 6000 k.w. Metropolitan Vickers turbo set or the two earlier Parsons 2000 k.w. sets. Further, the standard boilers (some of which are coal and some oil-fired) and the Velox generators feed into a common steam line, 'and with this combination a great elasticity of operation will be obtained. NEW PRINCIPLES IN STEAM. PRODUCTION. The steam generator is best described (if the engineers will excuse it) as a giant oil-fired caliphont. In the standard boiler —and in the household hot water system—a mass of water is heated; in the steam generator—and in the caliphont over the bath —there is no mass of gradually heating water, but a flow of water is rapidly heated. The idea of the steam generator is not new, and several types have been evolved, but for the Brown Boveri type is claimed a remarkable efficiency from its particular features. The standard boiler is able to make use of from 80 to 85 per cent, of the heat units which are theoretically extractable from a given quantity of fuel, the balance 'of the heat escaping by the flues and chimney stack as hot gasses and smoke or soot (which are particles of partially consumed fuel) and by radiated and other heat losses. On the tests made upon the first Velox at the Brown Boveri works before it was dismantled for shipment to Wellington 94 per cent. of heat efficiency was achieved.

AH boilers make use of forced draught to gain the highest possible combustion of fuel, for the draught drives in a greater supply of oxygen. In the Velox generator the extreme velocities of gases in the combustion chamber and through the evaporator tubes are the keys to the great speed at which the heat developed by the burning of the fuel is absorbed by the water passing through the tubes.

There is no great vault of boiler floor and fire-bricked walls in, the Velox steam generator, nor are there great masses to be heated before evaporation commences. It is, compared with the standard boiler, extremely compact. From this new section of the power house one walks a few yards to stand in front of one of the present boilers, occupying three, four, or five times the ground space and towering upwards, and is told that the new unit will produce double the steam. ' ( SPEED OF GASES. Velocities are the thing—hence the name Velox. Fuel and oil are forced into the combustion chamber at pressure sufficient to give the mixture a high initial velocity and combustion increases the velocity further, high above what had been dreamed of in

earlier design. The combustion chamber is surrounded by a wall of evaporator tubes, with more complicated tubing insfde them. From these inner tubes the steam passes to the tubular super-heater, round \yhich the furnace gases rush on at terrific velocity. The gases then pass on to operate a gasturbine blower which creates the pressure for the forced draught of the combustion chamber. Still the gases are at high temperature, and they arc used finally to pre-heat the water before it is pumped into the evaporator tubes lining the combustion chamber.

It sounds complicated, and it is immensely so, for with the five main sections of the generator there are associated a score or more of auxiliary appliances. Such a unit can only be described with a full range of diagrams and in great technical detail, not possible in a daily, newspaper, and even to engineers the new principles are so radically different as to demand study and inquiry, step by step. To the public the chief point of interest is that , the steam generator is capable of producing a full head of steam within minutes from standing cold, whereas the standard boiler must be kept with a head of steam day after day, at heavy annual cost of fuel, or the city must face the possibility of a complete shut-down of power-supply, should anything go amiss with the hydro-electric system, for an hour or two hours, while the boilers are brought up to steam-pro-ducing temperature. : However, the production of the head of steam is only the first step towards the bringing of a steam plant into operation, and though steam may be available to the turbo-generators in five, six, or ten minutes, a long sequence of operations must be followed before the city reticulation is made alive again. But in place of the delay of an hour or two hours before this sequence of operations can be commenced the delay will be reduced by the new steam producers to one of minutes only. THE DIESEL'S PART. In operation the Velox supplies its own power to its auxiliaries (pumps, blower, fuel, and water feeds), but it must have outside power to get under way. If the power interruption is complete neither fuel, water, nor draught can be started upon their cycles and this great steam machine will stand cold and helpless. It is here the Diesel has its place, for it is a self-sufficient auxiliary to the steam generator, as well as a supplier of power to other station auxiliaries in the event of breakdown. The Diesel starts, the steam machine starts, the sequence smarts, and the interrupted power supply, affecting every industry, the city's transport, the city's sanitation, and every household, is taken up again. It is probable that at no time will all the standard boilers at Evans Bay stand cold, but the installation of the new steam generators will enable great economies to be made in the fuel bill. The same, and even greater, speed of production of power from the standby station might have been achieved by the installation of Diesel plant to drive generators of 15,000 k.w. capacity, but the capital ' cost would have - been enormous.

The assembly of the first Velox generator has been supervised by Mr. H. Heiniger, an engineer sent to New Zealand by the makers, and in about a fortnight- a specialist engineer, Mr. Deitler, is to arrive to supervise and direct the tests and to supervise the final adjustments. The present plans are that the new plant should be ready for operation by mid-winter. The first cases of parts for the second steam generator will araive shortly.