Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

AIR LOCKS FOR SINKING CAISSONS, &c. (See Illustrations on page 76.) The following is a description of one of the best forms of Air Lock employed in connection with cylinder sinking operations, and as used by Messrs. Sir W. Arrol and Co., Ltd., on such important works as the Forth Bridge, etc. There are two locks—the material-lock and the man-lock—placed one above the other. The lower (man) lock has two compartments. It is semi-circular at the ends and flat in the centre, and has room for three men in each compartment. The lock is of steel plates, strengthened where necessary with beams and angles. The doors are of cast steel, and have rubber joints. Bull’s-eye glasses are fitted. The joints are caulked, and the whole is tested to a pressure of 50 lb. to the square inch. Cocks are provided to enable the workmen to regulate the air pressure when passing from one compartment to the other ; the outer space is used as an intermediate stage in entrance and exit. The material-lock is placed above the zmw-lock, the doors in this case being horizontal, and opened and shut by a hand rack-motion, worked from large hand wheels. A small steam-engine is provided for operating the winding drum. To throw this lifting- drum quickly out of gear, a clutch is provided so that when the buckets arc resting on the bottom door an overhead lifting arrangement may be brought into gear, and the buckets raised above the lock to tip the excavated material into the shoot. QUANTITY OF MATERIAL “LOCKED THROUGH” PER DAY. As to the rate at which excavated material can be “locked through,” it may be mentioned that, with a plant as described above, 160 buckets 2ft. 910. deep by 2ft. diameter = 8 cubic feet capacity, have been taken out in eight hours. This includes filling, hoisting 60ft., “ unlocking ” and emptying, also returning bucket to the working chamber. The time required to reduce the air pressure in the man-lock is regulated according to the pressure (see remarks on " decompression ” in preceding pages). Io reduce the pressure in the material-lock is a matter of a few seconds only. The Air Supply should be arranged so as to keep the CO2 below one-half per cent, (measured at atmospheric pressure). To ensure proper ventilation and allow for the gases generated by blasting, &c., four to five cubic feet per man per minute will generally be required, When asking for estimates for Air-locks, particulars of construction of caissons, and their dimensions should be supplied. 75