Strong-Rooms and Vaults Safes

About 1888 the "solid" safe was introduced. In this the top, bottom and two sides of the safe, together with the flanges at the back only or at both back and front, are bent from a single steel plate. This construction, with solid corners, only became practicable in consequence of the great improvements which had been made in the quality of steel plates.

The Modern Safe.

The requirements of a modern safe may be briefly summarized as follows: For fire resisting safes, the safe body must be constructed of steel plate of sufficient thickness, this varying with the dimen sions of the safe, to withstand the effect of a fall from an upper floor in the event of a fire and to resist the crushing effect of falling masonry, displaced girders, etc., as safes are frequently buried by falling debris in the ruins of office buildings. The crucial test of the fire resisting capacity of a safe is fully ap plied under these conditions, i.e., when buried under a red hot mass of ruins, often for a period of several days, before it can be dug out and removed from the collapsed building. The "proofing" of the safe must be of sufficient quantity, packed around the whole area of the body and door to preserve the heat resistance over a long period, otherwise when this reserve is exhausted the safe would become a slow oven and its con tents charred and completely destroyed.

Safes which are intended to resist burglars, as well as fire, must be made with greater constructional strength successfully to resist brute force and destructive violence. In addition, they need to be formed from such a combination of metals and alloys as will withstand all forms of cutting and piercing tools and appliances, in addition to the oxy-acetylene cutting blow pipe. This appliance, which is now in wide industrial use, will cut through practically all known steels, so that modern safe makers have had to resort to the metallurgist for the production of ferrous alloys which possess the power to resist the cutting ef fect of the gas flame, and are impervious to all drilling methods. The more successful of these alloys, although they can be heated by the gas flame to their melting point, cannot be cut, like steel, by the application of a stream of pure oxygen when their melting temperature has been reached.

It is essential that the walls and doors of such safes should be of considerable thickness, as mass is of great importance in providing resistance to the blow-pipe method of attack. The doors of such safes must be closely and accurately fitted to the opening in the safe body and secured in the closed position by a number of suitable moving bolts operated by an external handle. The actual shape of the bolts is not of vital importance,

provided they are of sufficient strength and rigidity to resist all forces that can be brought to bear against them in an effort to force the door away from the safe body. The majority of safe manufacturers use bolts formed from either round or flat sec tion steel bars, but others are of special shape and design.

In America, fire-resisting safes usually are not made burglar proof ; the highest standard of requirement being 20 minutes' protection against amateur attack through the door. Burglar proof alloy steel chests are however frequently fitted into fire resisting safes. Most important are the locks used to control its operation. To provide the maximum amount of security and lengthen the period of resistance that a safe will offer to forcible entry, more than one lock should be employed and the locks need to be made as large as possible to increase the amount of material which has to be removed to expose the lock. It is also advisable to provide the lock with more than one moving bolt to engage with the bolting mechanism, as it is this moving lock bolt which prevents the bolt action being operated and the bolts retracted into the door.

When gunpowder was the only explosive available, it was possible to construct safe locks to resist its use, but with present day high power explosives other methods must be employed. In good quality safes these take the form of independent bolting actions which are brought into active operation only by the actual force of an explosive, when used to destroy the working lock; the effect of such an explosion being to substitute the dogging action of the special device for that of the lock which it was sought to destroy. To prevent the insertion of explosives in the keyholes it is the practice with work intended for bankers' use to provide a shutter, either in the form of a rotating disc or a sliding bar built into the door, to close the entrance to the locks after the keys have been used, the shutter action being in turn locked by a dial on the face of the door. In some instances, keyless combination locks only are used to control the bolting mechanism, but these locks are not in general use or favour in Great Britain, although their use is practically universal in the United States.