XN000022-1977-07-17 — Page 4

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SUNDAY, JULY 17, 1977

+EXPLOSIVES HAVE LONG BEEN AN IMPORTANT TOOL IN THE BUILDING AND CONSTRUCTION INDUSTRY AND WITHOUT THEM MANY OF OUR LARGE SCALE PROJECTS SUCH AS THE HIGH ISLAND WATER SCHEME, TUEN MUN ROAD, ABERDEEN TUNNEL AND, MORE RECENTLY, THE MASS TRANSIT RAILWAY WOULD EITHER BE IMPOSSIBLE OR TAKE AN INCREDIBLY LONG TIME TO ACHIEVE, HE SAID.

+EACH BLASTING OPERATION IS SUPERVISED AND ONLY EXPERIENCED PEOPLE ARE PERMITTED TO HANDLE EXPLOSIVES, HE SAID.

VARIOUS BLASTING METHODS ARE USED CALLING FOR A VARIETY OF TECHNIQUES, AND WHEN NECESSARY EXTRA PRECAUTIONS ARE TAKEN TO REDUCE GROUND VIBRATION AND CONTAIN FLYROCK. SPECIAL TYPES OF DETONATORS ARE WIDELY USED WHICH ALLOW EXPLOSIVES CHARGES, EVEN THOUGH CONNECTED INTO ONE CIRCUIT, TO FIRE IN SEQUENCE. INSTRUMENTS ARE ALSO AVAILABLE WHICH CAN ACCURATELY MEASURE AND MONITOR GROUND VIBRATIONS RESULTING FROM A BLAST.

IN HONG KONG, VARIOUS TYPES OF EXPLOSIVES ARE BEING USED IN QUARRYING, MINES AND CONSTRUCTION PROJECTS -- THE MOST COMMON BEING AMMONIUM NITRATE FUEL OIL BLASTING AGENT (ANFO), SLURRY OR WATER-GEL EXPLOSIVES AND OTHER HIGH ENERGY EXPLOSIVES SUCH AS GEL IGNITE AND DYNAMITE.

+LAST YEAR WE PROVIDED A TOTAL OF 3,232.7 TONNES OF EXPLOSIVES TO VARIOUS MAJOR CONSTRUCTION SITES AND QUARRIES, COMPARED WITH ABOUT 950 TONNES TEN YEARS AGO, HE SAID.

AND WITH THE STEPPED UP GOVERNMENT BUILDING AND CONSTRUCTION PROGRAMME, COUPLED WITH THE INTENSIFIED ACTIVITIES IN THE PRIVATE CONSTRUCTION INDUSTRY, HE EXPECTED THE AMOUNT TO RISE FURTHER.

MR. RANSON SAID THAT OF THE CARTRIDGED EXPLOSIVES IMPORTED AND USED IN HONG KONG AT PRESENT ABOUT 75 PER CENT WAS DYNAMITE, AN EXPLOSIVE CONTAINING NITRO-GLYCERINE.

DYNAMITE HAS BEEN SUCCESSFULLY USED THROUGHOUT THE WORLD SINCE THE BEGINNING OF THE CENTURY. IT IS EFFECTIVE AND SAFE IF USED PROPERLY AND IS IN GOOD CONDITION BUT, BECAUSE OF ITS NATURE, ITS HANDLING, STORAGE, TRANSPORTATION AND USE NEED TO BE STRICTLY GOVERNED BY LEGISLATION.

HE SAID THAT AS A RESULT OF ADVANCES IN EXPLOSIVES TECHNOLOGY A NEW TYPE OF HIGH EXPLOSIVE MUCH LESS SENSITIVE THAN DYNAMITE, AND CONSEQUENTLY SAFER, HAD APPEARED IN HONG KONG IN THE LAST THREE YEARS. THIS EXPLOSIVE IS KNOWN AS WATER-GEL OR SLURRY.

ESSENTIALLY, WATER-GEL IS AN EXPLOSIVE WHICH CONTAINS AN OXIDIZER AND FUEL DISPERSED IN AN AQUEOUS MEDIUM, WHICH IS GELLED TO KEEP THE SOLIDS IN SUSPENSION AND WHICH IS SENSITIZED BY A NON-EXPLOSIVE INGREDIENT, THUS MAKING STORAGE, TRANSPORTATION HANDLING AND USE THAT MUCH SAFER THAN THE OLDER TYPE OF HIGH EXPLOSIVE.

/+IN FACT,