X18 BULLETIN 173, U. S. NATIONAL MUSEUM 



carefully machined and are assembled, staggered, one on top of the 

 other, with a through bolt from top to bottom holding each vertical 

 row of tubes together. Two short lengths of tubes with tube ends 

 and T-head through bolt and plates comprise the exhibit. The tubes 

 and tube ends are of cast iron. 



The cast-steel sinuous header of 187 J^ is an example of a very early 

 type of continuous header. This is the form that was used on the 

 Centennial boiler of 1876 (see above). The header is in effect a 

 curved tube with expanded portions into which the ends of tha 

 boiler tubes are let. The expanded portions have circular holes cut 

 to receive the tube ends and opposite holes through which the tube 

 ends can be rolled in assembling and through which the tubes may 

 be cleaned. These holes are covered with outside fitting, circular 

 plates. The header is designed so that the tubes in one vertical row 

 are staggered in order that the next vertical row will fit snugly 

 against it. The header section exhibited is three tubes high with a 

 short length of tube rolled into the top tube opening. 



The ca^t-steel marine boiler header, 1901, is a sinuous header of 

 rectangular section, arranged to take 2-inch tubes in groups of four. 

 Each group of four tubes has a square hand-hole fitting. Boilers 

 with headers of this type were installed on naval vessels of the Okla- 

 homa and the Maryland type. The header section exhibited is about 

 four tube groups high, with the top group fitted with two short tube 

 ends and sectioned. The other tube openings are not bored. 



The vertical lorought-steel header of 1921 is used to the present 

 day for boiler pressures of 450 pounds per square inch. The header 

 is square in section, sinuous in form, and about five-eighths inch 

 thick. Hand holes are elliptical in shape, machine faced, and milled 

 to a true plane to form a gasket seat. The openings are closed by 

 inside fitting, forged-steel plates, shouldered to center in the opening. 

 The section exhibited is a 4-tube piece with the upper end and a hand- 

 hole cover in section. A short length of tube is rolled into the upper 

 tube opening. 



The forged steel header of 1926 for 1,400 pounds per square inch 

 steam pressure is designed for boilers for central power stations of 

 which there are a number operating at this pressure in the United 

 States. The header is rectangular in section with rounded corners,, 

 sinuous in form, and made of forged steel approximately 1 inch 

 thick. The tube openings are provided with grooves into which 

 the tube ends are expanded. The specimen exhibited is about three 

 tubes high, with a %-inch thick tube expanded into the upper open- 

 ing and sectioned. 



