US2053413A - Superheater for high temperature steam - Google Patents

Description

Sept. 8, 1936. v w. H. ARMACOST 1 SUPERHEATER FOR HIGH TEMPERATURE STEAM Filed March 9, 1953 INVENTOR w/LBue ffi/MMACQST BY d/Vkzy ATTORNEY Patented Sept. 8, 1936 SUPERHEATER FOR PATENT] OFFICE HIGH TEMPERATURE STEAM Wilbur H. Armacost, New York, Y., assignor to The Superheater Company, New York, N. Y.

Application March 9,

5 Claims.

My invention relates to superheaters and particularly to those designed to produce steam of high temperature. V

In order that my invention, together with the 5 objects and advantages thereof, maybe clearly and readily understood, I will now describe in detail and in connection with the accompanying drawing a superheater installation selected by way of example from a number of possible embodiments of my invention. In the drawing,

Fig. l is a sectionalelevation of a superheater boiler having a superheater in accordance with my invention.

' Fig. 2 is a fragmentary detail on an enlarged scale of a superheater similar to that shown in Fig. 1 but including'certain modifications.

Fig. 3 is a'fragmentary detail of a portion of a superheater similar to Fig. 1 but embodying other modifications.

Fig. 4 is a fragmentary sectional view illustrating still further modifications.

A number of superheater installations have been proposed. in which the pressure and the final steam temperature are. quite high compared to the average of past practice. In such installations, it has usually been assumed to be necessary to employ special material for the superheater units to prevent undue rate of deterioration of such units from the high temperature gases and steam. It has been found, how.- ever, that superheaters employing such special materialfor the units are subject to undue leakage at the joints between the units and headers, particularly the high temperature header, unless such headers or header, are, or is, also made of the same material as the units. I have conceived that such diificulty of high leakage is due to the different coeflicient of thermal expansion of the material used for the units as compared to the coeiiicient of expansion of the material used for the header, such difference in the coeificients being important because the units are sometimes subjected to sudden changes in temperature of considerable amount due to changes in load and in firing conditions. I have conceived further that such difiiculty may be avoided in two ways.

One such way is by forming the units with end portions to be joined to the high temperature header and of the same ordinary material as such header. Such end portions should, of course, lie outside of the path of the heating gases and this is ordinarily readily arranged. In case such end portions are apt to be damaged by the steam, they may be given a. thin protec- 1933, Serial No. 660,108

tive coating of aluminum alloy, or other substance, adapted to protect them from the steam without changing their thermal coefiicient of expansion. The other such way is by making the units of special material throughout and using seat portions in the header of material having the same coefiicient as that of the units.

In thedrawing, I have illustrated a boiler ID of ordinary type having a gas pass I2 therein in which is a superheater composed of a plurality of: units, one of which appears at M. The units l4 extend in parallel between a header I6 for the saturated steam and a header I8 for the superheated steam. It is assumed that the installation of which boiler i0 is a part employs gases for heating the units l4 and a final steam temperature such that special material must be used for the portions, of the units in contact with such gases. The arrangement illustrated is one .-::ll adapted to such an assumption in that the steam flow is entirely counter-flow to that of the heating gases, a' condition well-known to produce the maximum metal temperature for a given final steam temperature and initial temperature of the heating gases. In the arrangement shown in Fig. 1, it is assumed that the high temperature ends of the units M are connected to header l8 by ordinary rolled joints. As usual, the header l8 isplaced outside the path of. the heating gases. The ends of units l4 pass-outside the contour of the boiler H] to make connection with the header l8 so that the end portions of the units are also out of contact with the heating gases. I take advantage of this fact to make an end portion 20 on each of the units M of the same material as the header I8, both such header and such portions being of the relatively cheap carbon steel while the main body portions of units M are of alloy steel or other material well adapted to withstand high temperatures even if in contact with gas and. steam also at high temperature. The material of the header I8 and that of the end portions 20 being, however, of substantially the same composition and therefore substantially the same thermal coeflicient of expansion, the oints 22 between the header and the end portions have no unusual tendency to leak steam. The end portions 20 can be readily united with the main portions of the units M by welding as indicated at 24.

Preferably also the inlet ends of the units l4 have portions 26 thereon of ordinary low carbon steel like that employed for saturated header 16, the portions 26 being united with the main port units I4 except that they are joined to the header |8a for superheated steam by a known type of releasable joint 220. instead of by the rolled joint shown in Fig. 1.

Fig. 3 shows a portion of a unit Mb and a' header for superheated steam; IBD united'b-y an ordinary rolled joint 22, the unit Mb, however i,

entering the header lBb on the side instead of at the top and the header lBb having normally" closed openings 30 therein to facilitate the rolling of the joints 32.

have illustrated a plate such as purpose.

It will be evident that much the same efiect as in Fig. 1 can be obtained by providing seatsof alloy steel in a carbon steel header and making the end portions of the units also of alloy steel of substantially the same coefficient of expansion as the seat portions of the header, whether or not the major portions oi the units. have said coefiijci'ent. Such an arrangement is illustrated in Fig. 4 and is the reverse in certain respects of that d? Fig. 1. In Fig. 4, the header I80 is of carbon steel but has apertured alloy steel inserts 30 shrunk therein to act as seats for the joints 32' for this T 220. In Fig. 4, however, the elements Mc are of alloy steel throughout so that they have no permanent joints 24 and the releasable joints 22c are formed by contacting surfaces of substantiallythe same thermal coefficients of expansion. I do not limit myself to shrinking inthe inserts 30, but may thread them into the header I80, or weld them into such header, or both thread and weld them in place in such header, certain known forms of screw threaded joints, as well as shrunk and welded joints beingv adapted to. be made up so tight as to be free of the danger of leaking and therefore to make the seat pieces 30-permanent parts of the header.

While I have shown my invention in connection with a boiler, it will be understood that my inven- Openings 3!] must of coursebe closed during periods when the apparatus is in use by known or other suitable means andI' tion may be used in separately fired superheaters.

What I claim is: I

1. A superheater having a header for superheated steam having a certain thermal coefiicient of expansion, superheater units connected to deliver steam to such header and having substantial heat absorbing portions of metal having a thermal coefiicient of expansion different from that of said header but having end portions integral therewith and contactingwith said header,

, said end portions having a thermal coefiicient of expansion substantially the same as that of the portions of said header with which they contact.

" 32. The combination of a carbon steel header,

units joined thereto and having substantially heat absorbing portions of high temperature alloy 'steelfbut having ends integral therewith of car- 1 bon steel' for joining to and contacting with said header.. I

3; The combination of a header whose major portion. is ofjcarbon steel, and heater'units arranged to deliver fiuid' thereto, said units having heat absorbing portions material sections of which are of alloy steel, and said header and units having joints therebetween intended to be broken when a unit: is removed from said header, the

parts in contact-in said joints having substantiallythe same coefficients of expansion and permanently fixed to the header and to the units.

4. A :superheater having: a headerfor superheated steam having a certain thermal coefiicient of expansion, superheater units connected to deliver steam to such header and having substantial-heat absorbing portions of metal having a thermal coeflicient of expansion different from that of the major portion of'said' header but having end:v portions integral with said units and contacting. with. metal portions joined to said header in such manner that the joints between said metal portions and said header remain tight against pressure upon removal of the units, the contacting parts of said units and header having substantially the same coefficient: of expansion.

:5. In a heater the combination of a header and a pipe. toxbe connected thereto,. the two parts being of metalshavin'g-different coefficients of expansion; and a metallic piece permanently secured to one of said'parts and releasably engaging. the other and having substantially the same coefiicient of expansion as the latter.

. i WILBUR H. 'ARMACOST.

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