Strong-Rooms and Vaults Safes

Time locks with two, three or four chronometer movements are frequently employed to control the hours for opening safes and vault doors. These locks are fitted in addition to either the key or dial operated locks, and are intended to prevent the door being opened at any other than the official times.

Strong-rooms and Vaults.

For the purpose of providing security for deeds, papers and books against the risk of fire, rooms are built either of brick or concrete, according to the con ditions existing on the site and the amount to be expended on the construction, the thickness of the walls varying from inches to 18 inches if built in brick, and from 8 to 14 inches in concrete. Bank vaults and strong-rooms for the custody of se curities, cash, etc., are now mainly constructed of reinforced con crete or with a combination of brick and concrete, the thick ness of the walls varying with their importance and the ground space available. Generally speaking, reinforced concrete walls can be built of less thickness than brickwork to provide equiva lent security against penetration, but in all important vaults and strong-rooms it is advisable to reinforce the walls, roof and floor with linings of steel and flame resisting alloy, forming a self contained safe inside the concrete shell.

The most effective method of employing steel to reinforce the concrete construction is to use it in the form of plates attached to the inner face of the walls by rag bolts or other suitable connections. The steel then has the protection of the full thick ness of the concrete and itself prevents the breaking away of the inner face of the concrete in large sections into the void forming the strong-room, whereas if the steel reinforcement is distributed throughout the concrete walling in the form of bars or mesh work, it can be quickly and easily cut through with the blow-pipe.

In the design of strong-rooms and vaults, the formation of the roof and floor is frequently of more importance than that of the walls, the latter are usually subject to inspection (unless the room is built against an exterior or party wall, which should be avoided if possible), whereas the floor is liable to attack by means of tun nelling which can be carried out without any indication being given until the actual breaking through of the floor of the room.

The highest degree of security is obtained when the vault is built as an island with an inspection or patrol passage entirely sur rounding it, the floor of the vault being laid on sleeper walls providing for full visibility below the floor level, with suitable lamps and switches for illumination.

Electrical devices are frequently installed to give an alarm in the event of a burglarious attempt upon strong-rooms, either upon the main structure or the door. In no case should they be regarded as a primary means of defence, for they may be put out of action through failure of an essential feature or neglect of maintenance and inspection duties.

A new type of bank vault that is said to be virtually immune to burglar attack through the use of copper in construction has been recently announced by the Copper and Brass Research Association in America. It is said that a burglar would require about six hours of uninterrupted effort with the oxyacetylene torch to penetrate a modern vault door 20 in. thick, containing a 12 in. plate of pure copper. The high resistance of copper to torch attack is explained by the fact that this metal is a rapid conductor of heat, in contrast with other metals of low heat conductivity heretofore used in vault construction. A torch capable of developing a heat between 5,000° and 6,000° F will penetrate the first few inches of a copper plate in a comparatively short time. However, the flame loses its efficiency as the copper conducts the heat rapidly away before the entire body of the metal can be raised to a fusing point, and the torch becomes ineffective. The ductility of the metal makes it unsuited for successful attack with explosives. The largest bank in Asia, Mitsui Bank building in Tokyo, is of this construction.