Tin-lined pipe.
Lead pipe is lined with tin in order to prevent the formation of deleterious salts by the action of the water on the lead.
Although the action of pure water upon metallic lead when there is no access of air to the pipe is so slight as to be uninjurious, yet it is found in practice that, owing to various causes, all water used for domestic purposes containing air and more or less mineral impurities, the water after its passage through lead pipes is found to become charged to a greater or less extent with the poisonous salts of lead.
Tin is much less subject to be thus acted on, and its salts are comparatively innocuous.
The earliest attempt to remedy this evil by lining the tin pipe with lead appears to be found in
Alderson's English patent of January 26, 1804.
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Machine for making tin-lined lead-pipe. |
In this the lead was cast around a core or mandrel in a twopart mold, the mandrel was then withdrawn and replaced by a smaller one, around which the fused tin was poured.
A reversal of the process was provided for, the tin lining being first cast, and the lead afterward poured around it. The compound pipe was afterward lengthened by being drawn out upon a mandrel.
A method of drawing out the tin lining upon a mandrel, inserting it in a larger leaden tube, and drawing out the two together, is also specified.
The first specified methods are still generally followed, various improvements having been made in the details.
In
Fig. 6461, the piston
B of a hydraulic press serves to operate the central plunger
E and the annular plunger
D F. The former forces out the tin contained in the central cylinder
H, and the latter the lead in the annular cylinder
G I.
J is the mandrel.
The machine admits of being arranged for making pipes all of one metal, as in the lower portion of the figure.
In
Fig. 6462, two or more cylinders
H H, K K are employed.
The hollow ingot of tin
B B is placed on a mandrel and forced through the central opening previously made to receive it in the ingot of lead
A. The pressure unites the two together, and the compound pipe is forced through a die and passes out through the opening
E.
In
Fig. 6463, the tin is cast around the mandrel
e, and is protected by a tube from the heated lead when the latter is poured into the cylinder
a a. By a motion of the plunger
b b or cylinder
a a, either of which may be the working part, the two metals are forced through a die at the bottom of the cylinder and united together.
