Use Green Island Cement
for
Constructural Work of Every Description.
HOW GREEN ISLAND CEMENT IS MADE
Green Island Cement is manufactured from hard limestone and clay. It is necessary that these materials should be finely ground in order that they may come into intimate contact with ono another in the burning process.
The finely pulverised materials are mixed Fa certain definite proportion, roughly one to three of limestone, and are fed to part of the Rotary Kilns.
In these kilns they meet the hot gases and flames generated by pulverised coal blown in, at the other end of the kilns, and after various chemical actions have taken place, they combine to form Portland Cement Clinker.
The Clinker is ground down with a small percentage of gypsum to regulate the setting time, and Green Island Portland Cement is thua produced.
www
Although sounding so simple, in reality the process is an intricate combination of mechanical, physical and chemical operations, needing great....... skill and care, Nothing but constant and accurate supervision will yield the results so well-known with Green Island Cement, namely, strength, uniformity and reliability.
USE GREEN ISLAND CEMENT
Issued by the
GREEN ISLAND LTD,
CEMENT CO
2ND FLOOR,
EXCHANGE BUILDING.
HONG KONG DAILY PRESS SATURDAY SEPTEMBER 12, 1931
ENGINEERING AND
REDUCING VALVES IN THE CONTROL OF STEAM PRESSURES.
MEETING LOW PRESSURE STEAM REQUIREMENTS FROM HIGH PRESSURE SOURCE.
APPLICATION OF THE RELAY PRINCIPLE.
BUILDING
BLOCK DWELLINGS
FOR WORKERS.
·THE QUESTION OF HEIGHT:
returned to
London County should be noted that in Germany uncil in 1923
rohen there is control over plans
auch 82v6 review of the
neods, || N1" may well be provided in Britain deliberately embarked on a policy under the new Town and Country of buikling block dwellings, gener Planning Bill. Thus, in Cologne, ally of a height of five storeys, the local town-planning soheme especially to accommodate those allows buildings of varying heights workers who must live near their in various zones Five-storey blocks places of employment. The sum of are only allowed in nonos where £500,000 was voted for the nequisi they will not interfere with light tion of sites, and several blocks are, and traffle. Possibly the. Manobos already completed and occupied by ter Town-planning Committee; may contented tenants. The flats raak endeavour to solve local, problems The proposal to limit the height for subsidy under the Whontley Act, in a similar manner. of fats in Manchester suburbs to of 1981 Each is normally provided
In London the sites have been three storoys will certainly cause
with a fixed bath in a separate carefully chosen with
vion much surprise to all who have beenroom and with a scullery or kit light, air, and transport facilities. studying the more recent attemptschenette in addition to a living. The demand for central fata is con It is a commonplace in modera Reducing the Steam Pressure
to solve the housing problem in in-room and bed rooms. The bright ofsiderable. Many who have been dustrial centres not only in Britain the central portion of Ants at St. living on outlying catates like Be- engineering that the trend in steam practice is towards higher stear amount of low-pressure steam is ex- There is, of course, much to be whole estate at Osgulston Street fatigue and expense of the daily
Seldom will it happen that the but on the Continent
Pancras is six storeys, and the contree or Watling have found the pressure and temperatures. In fact, notly that available from the steam said in favour of the policy, adopt has vary heights of four, five, and journey to and from work to be so large economies are already being which has passed through the tured since the war by every progres six storeys, providing in all, when grout that they have effected by the application of these hine for the production of power. sive housing authority, of building completed, 1,014 rooms. Theen central areas, further congesting conditions in power stations of Additional steam will frequently be cottage estates, mainly consisting buildings are supposed to be the bones already overtrowded. much greater capacity than these required, and this can be forthcom of semi-detached dwellings with answer to the demand for flats on cordingly, the new London. County formerly in unc. These higher presing by the application of a redus separate gardens, on the outskirts the Vicanese model in London, and Council that was elected last month sures and temperatures are by no ing valve on to the high-pressure of our largo towns. This policy is it generally agreed that both lay is steadily pursuing the policy start- menns freak conditions. The pro- system. Briofly, this is a devies by being continued in so far as it out and plaining are excellent.
ed in 1989 of erecting block dwell- gress is too definite to be regarded means of which steam at the re-
meets the needs of those who are. quired low pressure can be uniform able to live some distance from
me dis
London and Continental Practice, ings of five storeys, partly to house those who have to start their There are, however, numerously supplied from the high-pressure their work, although most students
This is only one of some eight daily work at a very early hour, other requirements of steam in system and maintained at practical of housing are of the opinion that
estates recently completed of new
and partly to accommodato those which distinctly lower pressures are ly unvarying pressure in spite of the provision of towns like Letch block dwellings, generally with a required. These include the numer-variations of the high-pressure. If
worth or Welwyn, in which it is height of five storeys. A typicalho will be displaced by the clear- ous operations covered by the term
possible to walk from home to example, is Broxholme House, Tuance of slums under the 1830 Act. production. "which marks many process work,"
factory, is in every way more desir-ham, which has the ground floor Experience has shown, however, The system has long been in use. able. industrial operations-the numerous Briefly, it comprises a main valve, But a large section of the com- and second floors to fats, and the dwellings must be carefully chosen. devoted to lock-up shops, the first that the tenants of these high block operations attached to the chemical, the control of which is effected by manity which at prosent lives in third and fourth floors to two manufactures for avaporation, and means of a diaphragm and spring. tions, cannot live miles away from where all the heat gathers from applicante from the central arese unhealthy and overcrowded condi- storey maisonetts. In the roof, They are selected primarily from for general heating, in addition to The main valve is operated so that its daily work, nor is it possible to the flues, are drying lofts for domen. power purposes, in which it is im-1 possible to utilise the steam in if the low-pressure steam builds and sufficions land in our congested these exceptional conditions which up, thereby increasing the pressure,cottages sufficient to accommodate cities on which to build separate now mark turbine practice,
the valve closes, it being ordinarily all those who ought to be removed kept open by the notion of the from insanitary areas. Il land has spring or an equivalent mechanical to be purchased at £25,000 an are device.
figure by no means unusual in Central London-the erection of cottages means either impossible rents or impossible losses.
(Continued on next Oolumn.),
now as even novel.
**
Combined
Excential Requirementa,
de
til washing On the Oliver Gold who are obliged to reside in reason. are five-storey buildings, with employment, The rents still ro smith Estate in Camberwell thereable proximity to their places of garden, for it must be noted that main too high for the pockets of the by building higher space can be poorest and most necesaltous cases. easily allocated to the provision of The actual cost of constructing a gardens and recreation grounde; building of five storeys is, of course, The planning of a these flats, high per room, but this method is especially as regards the internal more economical when the high cost pet arrangements, is decidedly higher of land is taken into consideration, in standard than can be found The architectural staff, too, have usually on the Continent. In Stock- gained much from past experience, hoka flats of six ad seven storeys | and the intest London tenement tivo. societies. In Copenhagen Taylor is responsible under the have been erected by local co-opera | dwellings, for which Mr. Minton per cent. of the new accommodation direction of the chief architect, Mr. built since the war is at least five Topham Forrcat, compare very France, and Roland (Amsterdam) healthy conditions, and economical storeys in height. In Germany, favourably as regards amonitics. high fats are the type of working planning with any post-war work- clase dwelling mest favoured by Jing-class Cats erected either in the public utility societies. But if United States or on the Continent.
To meet these differing needs it has formerly been the practice to generate high-pressure steam in one boiler or battery of boilers, while low-pressure boilers have been in- For such a reduction valvo a num stalled and run independently for bar of casontial requirements will the more general usages of stepm. become obvious. It will be requir It has, however, been frequently ed to maintain a constant pressure which can be placed in any con pointed out that this dual produc on the low-pressure side quite invenient position for necessor ins tion of steam is not the most econo dependently of the high-pressure, so pection and even enclosed to keep mical proposition, and that where that large Auctuations in the latter steam is required for both purposes will not affect the former Further, the main steam valve by means of it free from dirt wane 18 operates on any large scale, considerable it should be capable of operation chains passing over guide pulleys, economies stand to be effected by over large ranges of reductions of the generation of high-pressure pressure, and also be capable of The main steam valvo is of the steum, which is first utilised in a adjustment for definite saugen ingle balanced tyne. When clos turbing from which, after some ex As a reducing, Alve functions by scating by the full force of the od the valve is kept down upon its pansion, it can be extracted and reason of difference of pressure, high-pressure steam. This valve then applied to purposes requiring such a device should be sensitive to is operated from the relay through relatively low pressures.
small differences. Moreover, ita lever which is weighted so that The principle has been consider should be sufficiently sensitive to it can be set to any required pre- ably adopted in bleeder or extracmaintain the low pressure to withare on the low-pressure side. tion turbines. On this principle in say one pound or in some cases When shut the valvo is kept very eambined power and heating, plant even a few ounces. The whole re tight, and banking-up" is pre- can be run at a distinctly higher duction of pressure abould vented sharing S overall efficiency than if both these realisable in a single stage and go purposes were served by separate down to ritmospheric pressure of the lever opens a pilot valve. In operation the first movement boilera, In fact, in cases in which even below
is the main stem valve bringing the low-pressure steam requirements Such low pressures are usually the latter foto equilibrium, subse are large, high-pressure steam is dealt with by means of large disquent to which further movement first developed, and from it is exphragms, but these are not possible of the lever raises the main atcam tracted a part of its power in a high- with pressures greater than 15th valve without appreciable effort. pressure turbine which exhausta per square inch. into the general heating system. By such means the low-pressure Bimpe Construction.
In cases it is argued that such electric power may be produced, after making due allowance for the heat recovered in the process work, at an exceptionally low figure.
COLORCRETE
ANTI-GLARE
COLOURED
SNOWCRETE WHITE
FERROCRETE
RAPID HARDENING
PORTLAND CEMENT
BOLE-AGENTS –
STOCKS CARRIED.
DODWELL & CO., LTD.
QUEEN'S BUILDING
PHONA 260817
HONG KONG.
steam is automatically maintained. Thus with a steam pressure of 50015, per square inch, the low pressure might be set at 50, this latter figure remaining constant for any diminn tion of high-pressure down to the 50lb, at which the valve delivers steam at boiler pressure, and at any lower pressure which may bo attain ed. But with the increase of boiler pressure the low pressure will Brst rovert to the figure at which it was originally set, and, with increasing boiler pressure, still remain ena stant. Automatic pressure control is thus achieved.
The relay" mechquíam con
comprises doublo-acting piston, mounted in cylinder above a weighted lever, which rests on knife edges on a diaphragm. The whole is of sun- plo construction, with few wearing parts and these readily accessible. The reduced pressure has access to the underside of the diaphragm. Variations of the reduced pressurs are transmitted to an accurately made and almost frictionless pilot valve, which controls the "relay piston by the admission of water Pressure to one end, the other be.. Ing open to exhaust.'' The "platon is thus moved in a direction which, when transmitted to the main valve, effects the required con
The variation of the reduced stancy of the low pressure.st pressure is effected by a movable weight on the diaphragm lever.
The application of these reducing valves are numerous. For many years in marine work bailer prea sures commonly exceeded that re- quired by the steam unit, and the necessary reduction was effected by valves of this type, thus maintain ing constant speed even with varia. The system admits of very fine tions of steam pressure. By apply control of about it and this. ing them at some distance from the figure can be reduced to as low as engine a small reservoir of low- a few ounces. Further, this reduce: pressure steam became available, el pressure may be within a pound avoiding the possibility of the valvor so of the boiler pressure if de feeling the pulsations of the engine.
sired re
*** Relay Reducing Valver,
In recent times there, has arisen
the need for the application of reducing valves in canection with
|
Whore both high and low pros sure boilers are installed the re-
lay reducing valve in-serviceable for passing over to the low pres suro erstem any surplus-steam generated by the high-pressurs.
| high-pressure and temperature boilor. Under such circumstanoca steam. These arduous and exact the relay valve is set to operate ing conditions impose spbolat 'reat about fib per square inch below quirements which can only vs melt the blowing off presmire of the by the application of the highear high-pressure "hpiler. The low- nings of workmanship, and, ther pressure boilers can then be steadi fore, both in deign, and produs is fred to keep the reducing alve |tion, reducing valves have been open," to that there will be no op brought to a remarkably high cosion to resort to the ancconomi stato of perfection,
cal procedure of increasing the |--- In addition, owing to, the par-firing of the low-pressure boilers.
ticularly severe conditions of me- By this separation of the relay dern steam practice it has been mechanism there is gained the ad-] found, necessary and possible, by vantage that with superheated| the adoption of the relay princi- stcjm the controlling mechanism la ple, to separate the contralling altogether away from the steam, mechanism from the main steam and the principle is capable of a salve Roducing, valres of this ory wide range of--inplication type are now availablog and meet. Thus with a large diaphragm, the many demands and conditione full travel of the relay can be which were not readily catered
arcted for a change of pressure
for in the more briginal types of of a fów ounces," while by the sub-
stitution of piston for thr
The whole mechefiam convenienb | diaphragm bydraulic pressures "up" MEDITATES |tx=300-tbx, per square inch can be mechaniem, I controll:
There
THE EXPRESS
LIFT CO. LTD. WITH WHICH IS INCORPORATED THE BUSINESS OF
SMITH, MAJOR & STEVENS, LTD,
EXPRESS SMS
LIFTS
MODERN LIFTS
FOR MODERN BUILDINGS
SPEEDY RELIABLE SERVICE
FOR DETAILS APPLY TO
THE G.E.C., QUEEN'S BUILDING, CHATER ROAD,
EVERYTHING (S&C.) ELECTRICAL