Part 3 (2/2)

[Illustration: No 12]

All of the types mentioned, with the exception of Nos 5 and 6, had between their several parts a large number of bolted joints which were subjected to the action of the fire When these boilers were placed in operation it was de surfaces, leaks were caused due to unequal expansion

No 12 With this boiler, an attempt was made to re surface in a given space Water tubes were expanded into both sides of wrought-iron boxes, openings being made for the admission of water and the exit of steam Fire tubes were placed inside the water tubes to increase the heating surface This design was abandoned because of the rapid stopping up of the tubes by scale and the i them

[Illustration: No 13]

No 13 Vertical straight line headers of cast iron, each containing ts of tubes, were bolted to a connection leading to the steam and water druht-iron box was substituted for the double cast-iron headers In this design, stays were necessary and were found, as always, to be an element to be avoided wherever possible The boiler was an ie as introduced underneath the dru surface into the coe as found to be difficult to keep in repair and was of no particular benefit

[Illustration: No 15]

No 15 Each row of tubes was expanded at each end into a continuous header, cast of car wheel metal The headers had a sinuous forered position of the tubes when assens of header form were tried later, experience with Nos 14 and 15 showed that the style here adopted was the best for all purposes and it has not been changed irders resting on the brickwork Bolted joints were discarded, with the exception of those connecting the headers to the front and rear ends of the drums and the bottom of the rear headers to the mud drum Even such joints, however, were found objectionable and were superseded in subsequent construction by short lengths of tubes expanded into bored holes

[Illustration: No 16]

No 16 In this design, headers were tried which were ular boxes, in each of which there were three tubes expanded

These boxes were alternately reversed and connected by short lengths of expanded tubes, being connected to the drum by tubes bent in a manner to allow them to enter the shell normally The joints between headers introduced an element of weakness and the connections to the druive adequate circulation

[Illustration: No 17]

No 17 Straight horizontal headers were next tried, alternately shi+fted right and left to allow a staggering of tubes These headers were connected to each other and to the drums by expanded nipples The objections to this boiler were almost the same as those to No 16

[Illustration: No 18]

[Illustration: No 19]

Nos 18 and 19 These boilers were designed primarily for fire protection purposes, the require a small, compact boiler with ability to raise steam quickly These both served the purpose admirably but, as in No 9, the only provisionof dry steam was the use of the steam dome, shown in the illustration This dome was found inadequate and has since been abandoned in nearly all forested at the tieneral use as Nos 21 and 22 In Europe, however, where small size units were ely with excellent results These experih ns were built, clearly demonstrated that the best construction and efficiency required adherence to the following elen:

1st Sinuous headers for each vertical row of tubes

2nd A separate and independent connection with the drum, both front and rear, for each vertical row of tubes

[Illustration: No 20A]

[Illustration: No 20B]

3rd All joints between parts of the boiler proper to be made without bolts or screw plates

4th No surfaces to be used which necessitate the use of stays

5th The boiler supported independently of the brickwork so as to allow freedom for expansion and contraction as it is heated or cooled

6th Ample diameter of steam and water drums, these not to be less than 30 inches except for small size units