CLP: The construction of Hok Un power station 1921, Part Two

Graham Wood has kindly sent a copy of the souvenir brochure issued at the official opening of the Hok Un power station in 1921.

HF: I have retyped the original PDF version of the brochure sent by Graham and as it is a fairly lengthy document this is the second in a series of articles. I will include all the images and script shown in the original brochure but am unable to reproduce its exact format.

Thanks to SCT for proofreading the retyped copy.

NEW STATION

The new station has been designed by Mr. S.E. Faber, A.F.C., M.Inst.C.E., M.I.Struct.E., who was responsible for the preparation of the drawings and specifications and for the supervision of the erection of the station building.

The specifications of the equipment were prepared by the Company’s Executive staff, Mr. D.W. Munton. A.M.I.E.E., Manager, Mr. I.N. Murray, B.Sc., M.I.E.E., A.M.I.Mech.E., Deputy Manager, and Mr. F.C. Clemo, F.Inst.F., Executive Engineer-Station Superintendent, to the requirements of the Board of Directors.

Messrs. Preece, Cardew & Rider, Consulting Engineers of 8 and 10 Queen Anne’s Gate, London, S.W.1. acted in an advisory capacity.

SITE

The site of the new station lies immediately to the south of the original station on land reclaimed from the harbour in 1929 inside a sea-wall of massive granite blocks. The sub-soil consists of sandy “decomposed granite,” sand and boulders overlying the solid bedrock. On about half of the site it was possible to take the foundations down to the rock, on the remainder, however, concrete piles were necessary. Owing to the sandy nature of the reclaimed ground and the close proximity to the sea, the deep excavation for the pump pits and foundations gave trouble, as it was difficult to unwater the pits, so that in some cases it was necessary to sink reinforced concrete caissons.

BUILDINGS

The buildings are, in general, of steel frame construction, faced with reinforced concrete walls, to resist the high pressures of typhoons and to ensure complete water-tightness. Interior walls are of brick, floors of reinforced concrete and the roofs of hollow reinforced concrete, insulated against the tropical sun with cork under the water-proofing.

Special consideration was given to resistance to wind, as the site is exceptionally exposed to typhoons. During the storm of September 1937, a wind velocity of 167 m.p.h. was recorded together with a record high water level.

The necessity for adequate protection from such winds which are accompanied by driving rain and spray from the harbour, led to the adoption of reinforced concrete outer walls. All concrete for the buildings was vibrated and gave excellent results on test.

The present buildings are designed to accommodate 60,000 kW. plant capacity. When the anticipated increase in demand warrants the completion of the plant, it is intended that the old station will be demolished and new buildings to house a further 60,000 kW. of generating plant will be erected on the site, thus bringing the total capacity to 120,000 kW.

The boiler house is arranged to house four boilers, the first of which has been completed and the second nearing completion. The building is 220′ long, 51′ 9″ wide between centres of columns, 93′ from basement to underside of roof trusses, the roof being 100′ from ground level. The firing floor is 15′ above the basement and the fans, grit arresters, air heater and chimney are mounted on the fan floor, 70′ above the basement.

The turbine room lies parallel with the boiler house and is 185′ long, 60′ wide and 73′ high and is equipped with a 50-ton electric travelling crane. Between the boiler house and turbine room, a pump bay accommodates some of the auxiliaries at basement level, the boiler feed pumps and L.T. switchgear at firing floor level and the reserve tanks and surge tanks on upper floors. This bay is 28′ wide and of the same height and length as the turbine room to which it is open.

The high tension switch house is parallel with the turbine room, but separated from it by a fire-wall. It is a single storey building 110′ long, 38′ wide and 17′ high, completely cut off from the station by reinforced concrete walls. Special attention was paid to the layout of this room to minimise the damage in case of fire or explosion and to protect the gear from probable spray swept over the building during typhoons.

The switch house is both physically and electrically sub-divided into four sections separated by fire-walls and fire-doors, with flame barriers between the inter-connector switches. Separate oil-drainage is provided for each compartment, leading to a pebble-filled sump outside. Cables in the cable basement below are also segregated and

buried in pebbles. As a further protection, remote controlled CO₂ fire-extinguishing equipment has been provided for each compartment. Ample release of pressure due to explosion is ensured by continuous storm-proof louvres just below the roof, while daylight is provided by glass inserts in the roof slab, obviating the need for opening windows.

Adjoining the switch house and adjacent to the turbine room are the offices, battery room, laboratory and control room as well as mess room, changing room and lavatories with showers. The control room has been made splinter-proof, and is provided with ample artificial lighting, including emergency lighting, and Carrier air-conditioning equipment. A separate floor under the control room accommodates the control multi-core cables, which are then led through a reinforced concrete duct of ample size to the basement under the switch house.

The auxiliary transformers are located in the open outside the boiler house, underground ducts being laid to take the H.T. cables from the switch house and the L.T. cables to the switchboards at operating floor level.

VENTILATION

The ventilation was considered separately for each section of the station. The boiler house is provided with vertical storm-proof louvres, of ample capacity to give air both for combustion and free ventilation, assisted by the natural chimney effect of the high building.

The turbine room has eight 54″ Robertson ventilators with exhaust fans, to provide eight full air changes per hour. Air is admitted through storm-proof louvres.

LIGHTING

The natural lighting in the turbine room is taken from the roof by wide lights, which also also act as expansion joints for the roof slab. To reduce the heat transmission into the room in the hot season,

Calorex heat-resisting glass is provided in the lights, the greenish light giving an appearance of coolness apart from the actual heat absorption.

CIRCULATING WATER SYSTEM

The sea water used as cooling water is taken in near the South end of the boiler house through rough screens, and led in short culverts to a screen house with four rotating belt screens, from which it is admitted to the twin culverts running the whole length of the Station under the Pump Bay. Sluice gates are provided so that each section can be isolated and dried for inspection and repair without shutting down the Station. From the culverts, branches are taken to individual pump-pits for each generating set. After passing through the condensers, the discharge is led away through syphonic tanks to an outlet culvert under the offices. For the major part of its length the intake culvert is in rock excavation, and considerable blasting under water was required, as the culvert is fully submerged even at lowest low water.

This article was first posted on 7th November 2021.

Related Indhhk articles:

1. CLP: The construction of Hok Un power station 1921, Part One
2. CLP – Hok Un (Yuen) Power Station 1921-1991 – updated
3. John M. Henderson, Engineering Company, Aberdeen, Scotland…link to Hok Un power station, Hong Kong
4. Andrew Wood biography – involvement in the repair of Hok Un power station at the end of the Japanese occupation of Hong Kong
5. Hok Un Power Station, post World War Two images
6. CLP’s Hok Un Power Station – immediately post World War Two
7. Preece, Cardew and Rider – Consulting Engineers for Hok Un power station
8. CLP’s Hok Un Power Station during the Japanese occupation
9. CLP- Lawrence Kadoorie speech 1977 – HK + Hok Un Power Station during WW2
10. Robert Gordon Shewan – CLP, Green Island Cement and HK Rope Manufacturing