8. The apparatus should be so constructed that no lime sludge can gain access to any pipes intended for the passage of gas or circulation of water.
9. The use of glass gauges should be avoided as far as possible, and, where absolutely necessary, they should be effectively protected against breakage.
10. The air space in a generator before charging should be as small as possible.
11. The use of copper should be avoided in such parts of the apparatus as are liable to come in contact with acetylene.
The BRITISH ACETYLENE ASSOCIATION has drawn up the following list of regulations which, it suggests, shall govern the construction of generators and the installation of piping and fittings:
1. Generators shall be so constructed that, when used in accordance with printed instructions, it shall not be possible for any undecomposed carbide to remain in the sludge removed therefrom.
2. The limit of pressure in any part of the generator shall not exceed that of 20 inches of water, subject to the exception that if it be shown to the satisfaction of the Executive of the Acetylene Association that higher pressures up to 50 inches of water are necessary in certain generators, and are without danger, the Executive may, with the approval of the Home Office, grant exemption for such generators, with or without conditions.
3. The limit of pressure in service-pipes, within the house, shall not exceed 10 inches of water.
4. Except when used for special industrial purposes, such as oxy- acetylene welding, factories, lighthouses, portable apparatus containing not more than four pounds of carbide, and other special conditions as approved by the Association, the acetylene plant, such as generators, storage-holders, purifiers, scrubbers, and for washers, shall be in a suitable and well-ventilated outhouse, in the open, or in a lean-to, having no direct communication with a dwelling-house. A blow-off pipe or safety outlet shall be arranged in such a manner as to carry off into the open air any overmake of gas and to open automatically if pressure be increased beyond 20 inches water column in the generating chamber or beyond 10 inches in the gasholder, or beyond the depth of any fluid seal on the apparatus.
5. Generators shall have sufficient storage capacity to make a serious blow-off impossible.