The jars usually stacked in tiers between permanent and temporary floors covered with tan. A stack formed in this way is left for about three months to ferment, when the heat vaporises the acid and causes the tan freely to give off carbonic acid gas. This forms a coating of carbonate on the lead, which is then removed and ground. To bring it to its ordinary commercial form, as used by the painter, it is then reground in linseed oil.
Lead in Contact with Portland Cement. It is now known that lead is affected chemically by damp Portland cement, and for this reason it is suggested that lead which comes into contact with cement should be previously coated with bitumen.
<Callout type="warning" title="Safety Hazard">Using lead pipes without coating can result in chemical reactions leading to potential health risks.</Callout>
Lead Pipes. At one time lead pipes were made by bending the lead around a core and soldering the joint, and pipes of this kind are still sometimes found in old houses. Nowadays, however, solid drawn-lead pipes are used, and are seamless. They are made by forcing semi-molten lead through a die by means of a hydraulic press, or by the use of a ram actuated by steam.
Over the head of the ram a thick cylinder of lead is enclosed in a very strong casing. At the top of the casing interchangeable dies can be fixed, varying of course with the size of the intended pipe. The ram works around a rigid pillar, to the top of which a short length of core is fixed, having a diameter equal to that of the pipe. Around this is fixed the die, which is larger in radius by an amount equal to the thickness of the pipe.
Through the opening so left, the ram forces the lead in the form of a continuous tube.
<Callout type="tip" title="Efficient Manufacturing">The use of dies and hydraulic presses ensures consistent quality and reduces labor costs.</Callout>
Tin-lined Lead Pipes. In somewhat the same category as lead pipes are tinned-lead pipe and tin-lined pipe. The former is of drawn lead thinly coated with tin by the simple process of pouring a little molten tin into the lead pipe as it comes from the pipe machine, the pipe being sufficiently hot to keep the tin in a molten state.
The object of tinning or tin lining a pipe is to make it suitable for the conveyance of soft water without injuring its quality, but there is often considerable trouble with the joints, the lining being destroyed and laying the surface of the lead bare. Standard Specifications for lead pipes (No. 602) and for ternary alloy pipes (No. 603) are available.
<Callout type="risk" title="Joint Failure">Poorly sealed joints can compromise the integrity of tin-lined pipes, leading to water contamination.</Callout>
Bends and Traps in Lead. Bends and traps can be formed from drawn-lead piping by means of special bending appliances, but the solid drawn-lead bends and traps can be made in a pipe machine very similar to the one described already.
The difference lies in the fact that, in place of the vertical ram, two horizontal rams are used. By setting them to work at varying speeds the lead is forced through the die at a faster rate on one side than on the other. Thus giving a bend of radius depending on the relative velocities of the rams.
Lead Wool or Leadite. This substance consists of fine threads or shavings of lead, twisted to form a sort of rope. It is used instead of ordinary molten lead for caulked lead joints and is particularly suitable for work under water or in positions difficult of access.
Key Takeaways
- Lead pipes can be made by bending the lead around a core and soldering the joint, but modern seamless drawn-lead pipes are more common.
- Tinning or tin lining of pipes is used to protect them from chemical reactions with water, though it poses risks at joints.
- Special machinery ensures efficient manufacturing of bends and traps in lead piping.
Practical Tips
- Use bitumen coating on lead pipes that come into contact with damp Portland cement to prevent chemical reactions.
- Regularly inspect tin-lined pipe joints for signs of damage or bare lead exposure, as these can compromise water quality.
- Utilize specialized machinery for manufacturing bends and traps in lead piping to ensure consistent quality.
Warnings & Risks
Health Risks
Improper use of lead pipes without proper coating can result in lead contamination of drinking water, posing serious health risks.
Poorly sealed joints in tin-lined pipes can allow for water contamination and lead exposure. Lead pipes are susceptible to corrosion over time, especially when exposed to acidic water.
Modern Application
While the manufacturing processes described in this chapter have evolved significantly since the early 20th century, understanding these historical techniques provides valuable insights into the principles of pipe design and material selection. Modern materials like PVC and copper offer improved durability and safety but still benefit from the foundational knowledge presented here.
Frequently Asked Questions
Q: What is the process for making lead pipes using a hydraulic press?
Lead pipes are made by forcing semi-molten lead through a die using a hydraulic press. The process involves enclosing a thick cylinder of lead in a strong casing and fixing interchangeable dies at the top, which vary according to the intended pipe size. A short length of core is fixed around a rigid pillar, with a die larger in radius than the core's diameter. The ram forces the lead through an opening, creating a continuous tube.
Q: Why are tin-lined pipes used and what are their limitations?
Tin-lined pipes are used to protect against chemical reactions between damp Portland cement and lead, but they pose risks at joints where the lining can be destroyed, exposing bare lead. This can compromise water quality and lead to potential health hazards.
Q: What is the purpose of using bitumen coating on lead pipes in contact with Portland cement?
Bitumen coating is used to prevent chemical reactions between damp Portland cement and lead, which could otherwise affect the integrity of the pipe. This helps ensure that the lead remains stable and does not leach into the water supply.