The Lancashire boiler

 

This boiler has great similarities with the Cornish boiler, except for the number of tubes. The Cornish boiler has one tube, the Lancashire two. Thus the capacity is bigger, but at the same time the design causes automatic internal water circulation.

Especially when starting the boiler there is always a danger of uneven heating. Uneven heating causes tension in the metal of the boiler and that could cause the material of the boiler to crack. The Cornish boiler is more vulnerable to these cracks than the Lancashire. To prevent this, many boilers use a circulationpump to pump cooler water to heater parts of the boiler.

Like the Cornish boiler, this boiler needs extra draught in the firetubes. Therefore this boilers cannot operate without a huge chimney.