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Патент USA US2412887

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Patented Dec. 17,1946
“2,412,887 "
' UNITED' STATES PATEN fr '_ osi-‘lcs
Frederick P. Huston, Fanwood, and Lawton A.
Burrows,v Woodbury. NJ., and Walter E. Law
son, Wilmington, Del.; said Huston assignor to
The International Nickel Company, Inc., New
York, N. Y., a corporation of Delaware; said
Burrows and said Lawson assignors to E. I. du
VPont de Nemours & Company, Wilmington,
Del., a corporation of Delaware
Original application February 2, 1943, Serial No.
474,480. \ Divided and this appl’cation Decem
bei' 19, 1944, -Serial No. 568,882. ïn @aliada
`December 16,` 1942
l e claims. d(ci. ss-Lsl
lThe present invention relates to heat exchange
is largely eliminated.
invention will become apparent from the fol- i
‘ lowing detailed description of the invention taken
change apparatus as boilers.
Conventional staybolts for use in the assembly
in conjunction with the drawing in which:
of the nre sheets and wrapper sheets of boiler
Fig. l shows a fragmentary sectional view of a
lire boxes may be described as the screwed-`
locomotive boiler nre box showing two embodi
ments of staybolts produced according to the
10 present invention;
the staybolt was screwed so that the ends ex
ltended beyond the cuter faces of the fire sheet
and wrapper sheet a distance `at least equal to
two threads on the bolt. Flexible staybolts ex
tended through the nre sheet in a similar man
ner. _'I'hese extending ends were then upset so as
`o form a spread rounded head.
Other objects and advantages of the present
Wrapped sheets in the ilre boxes of such heat ex
through ends-riveted type of construction. In
fitting rigid staybolts in this ltype of construction
the nre sheets and wrapper sheets were provided
with aligned threaded openings through which
wrapper sheet due to notch eiiect in the threads-
apparatus and, more particularly, to the stay
bolts used for securing the fire sheets and
Fig. 2 is an enlarged fragmentary sectional
view of one end of a staybolt provided with a
charged explosive capsule, said staybolt being
screwed into a 1tapped hole of a lire sheet;
l Fig. 3 depicts a similar fragmentary sectional
view of a reduced body staybolt screwed> into a.
.tapped hole „in the ilre sheet, the bolt having a
charge of explosive within a bore provided in .this
end; and
diiliculty has been experienced with `this type of 20 Fig. e is a fragmentary sectional view showing
construction due to leakage of steam and/or
abolt similar to that of Fig. 3 in expanded con
water between the male and female threads where
dition following detonation of the explosive'
the bolt passes through the‘sheet. This difficulty
has been particularly 4acute on .the lire side of the
to Fig. l, ref
ñre box.
Difllculty was experienced not only in obtaining 25 erence character 2 represents the found-ation ring
a tight fit between the staybolts and the ñre
of a iire box having an outside nre box sheet or " `
sheets but also, particularly with staybolts of 4the
rigid type. it had been found that numerous
wrapper sheet ß and an inside iire box sheet or
lire sheet 8. The lire sheet and wrapper sheet
irá tlìe plane of the inner surface of the wrapper
nated by reference character I2, isa rigid stay of
are provided with aligned threaded holes` 8 in
bolts broke in service. >It has been almost uni 30- which
staybolts represented generally by th-e ref
versal practice to construct nre boxes with wrap
erence character S are litted. Two such staybolts
per sheets of heavier gauge than the fire sheets,
are illustrated in Fig. 1. One of‘these, desig
and it was found that the staybolts which -brolre
nated by the reference numeral l0, is a straight
I in service almost always fractured substantially
, body, rigid type of stay, whilefthe other, desig
ee .
We have invented a staybolt and a method for
expanding the ends thereof in the sheets or plates
the reduced body type.
Straight body rigid stays ordinarily are pro
with threads throughout theiriength, The
of heat exchange apparatus, boilers, or .the like, I vided
body rigid stays, on the’contraiyare
which provides ñuid tight joints at any elevated 40
threaded only at the ends and the center region
pressure normally encountered in such equip
of the stay has a body of reduced diameter with
ment, and we also have provided staybolts which
to the threaded ends. Both types of
are substantially free from breakage during use.
rigid stays may be provided with a tell-tale hole,
It is an object of the present invention to pro
vide a staybolt >with means for insuring a fluid
such as that illustrated‘at I4, or they may be
45 hollow .throughout their entire length as illus
tight joint with a sheet through which it passes
trated at it.
throughout the entire areas of adjacency between
said staybolt and sheet.'
_Another object of the present invention is to
` provide a means for expanding staybolts into 50
fluid-»tight engagement with the sheets with
which they are usedby the use of explosive force.
A further object of the present invention is
the provision of staybolts in which concentration
oi stresses in the plane of a lire sheet and/or 55
,Moreoven in order to reduce the notch eñect of
the threads, the threads may be machined off, as
indicated at _22, .to provide a bolt having the
lowest practical value of localized stress in the
plane of the inner face of the Wrapper sheet and
ñre sheet. The machining should extend only
slightly under the root diameter of the vthreads so
as not to reduce the net diameter or net larea
of .the bolt appreciably.
The 'nre ysheet and wrapper sheet> ordinarily
velocity explosive extending slightly beyond both
will be made of rolled steel plates or sheets. The
staybolts may likewise be made of steel but we
prefer to make them of a nickel-copper alloy of
’the type sold commercially under the trade-mark
charge 32 of the type of lead azide and mercury
fulminate is adjacent to the base charge and is
adapted to detonate said base charge at its maxi
edges ofthe fire wall.
A compressed primer .
mum velocity. The ignition charge 33 is fired by
“Monel" which contains approximately two parts
of nickel to onepart of copper.
`Great difliculty had been experienced in fitting
means of the fuse 34.'
‘ In carrying out our invention, various explo
' staybolts sufficiently tightly within the holes in
sivesmay be used. It ispreferred, however, to
prevented.' Attempts were made to .prevent leak
age by extending thestays beyond the plate not
less than two threads when installed and there
the copending United States application, Serial
_ the nre sheet and wrapper sheet that ‘leakage’ was 10 use the explosives described in greater detail in
No. 426,150.
_ It is essential that the explosive be one of the
after upsetting the end to provide a rounded head f
classl designated as “high velocity explosives," in
' such as> that illustrated in Fig. 1 by reference 15 other Words, one that possesses a normal velocity .
of detonation above 1000 meters per second when
character 24. This expedient did not solve the
dimculty since leakage still occurred ln- boilers
shot under the usual conditions of determining
velocity. \ The primary detonating compounds
. having the staybolts headed in this manner.
Moreover, in certain areas of the- fire box, the I may be employed, for example, mercury-fulmi
rounded heads of the staybolts were rapidly cut 20 nate, lead azide, diazodinitrophenol. Preferably,
y however, we- use explosives such at tetryl, nitro
away by the flow of cinders until the bolt was
lsubstantially flush with the exposed face of the
e ñre sheet, thus destroying the sealing eiîect that
the rounded heads were designed toproducïe.
l We have discovered I'that completely ñuidf
tight joints may be easily and inexpensively pro
duced by expanding the ends of the 'staybolts
through the use of explosive charges. For this
purpose the end of the staybolt which is to be
expanded is provided with a bore 26 adapted to
receive an explosive charge. This bore should
extend at least to the plane of the inner face of
the ñre sheet or wrapper _sheetand preferably
extends at least about '/s to 1% .inch beyond. In
mannite, pentaerythritol tetranitrate, and the
like, which detonate at high velocity and at the
same time develop great' strength because of the
26 larger gas volumes. The amount of explosive
may depend on the diameter of bolt, the charac- l
‘ 'teristics of the metal of the'bolt and other fac
tors. It will be understood that the diameter of
-the bore hole for containing the explosive should
30 lbe suinciently large to accommodate a charge of
the proper amount. At the same time, the thick--ness of metal betweeny the center ~hole and the
outer bolt wall must be enough to give.the nee
ess‘ary strength when the metal has vbeen expand-v
straight body staybolts the bore 26 may bea part 35 ‘ ed. An advantage of expanding. the staybolt in
accordance with our invention over mechanical
of the-tell-tale hole, but in reduced body stay
bolts the bore 26 has a larger diameter than the
expanding methods'lies in the uniformity of ex
tell-tale hole. The bore 26 must not extend be
yond the change of section since the net area
pansion in all directions.
’ 'l
. The following examples illustrate specific em
' bodiments of steybqlts Joined to metal wens
of the cross section of the metal at the end should
not be less than the net area in the reduced sec
4.o where the ends of said .bolts have been expanded
tion. The staybolt -is screwed into the threaded
holes in the rlre and/or wrapper sheet in the
usual _manner and it may extend only- iiush with
the exposed face as shown at 21 in Fig. 1, or it
by means of explosive charges.
_ Example No. 1 Y
' A threaded bolt of % inch diameter made of@
. may extend any-desired distance beyond, as illus
the _nickel-copper alloy sold under the trade-mark
vtrated in Figs. 2, 3 and 4. In Figs. 2 _and 3 the
» play between the bolt S and the sheet 6 prior
to expanding the end of the bolt has been exag-v
“Monel” was screwed into the tapped hole of a
gerated forpurposes of illustration.
Either> before or after the bolt is in position,
an explosive charge 28 is placed inthe bore 26. '
'.Ehe explosive charge 28 may be loaded directly
into the bore hole, if desired, as illustrated in Fig.
nre sheet of 1/2 inch thickness until it extended
slightly‘beyond the outside face of said sheet.
A -bore hole of 0.235 inch diameter and of -% inch
depth had been provided at the end of the bolt
adjacent to the fire sheet and into this bore was
inserted a cylindrical metal shell, adapted lto _ilt '
' said bore and containing a compressed charge
In such case it` may be desirable to insert a 55 „of 10 grains of pentaerythritol tetranitrate at `its
disc'or closing- device at the base of the hole to
keep the explosive from extending into the nar
base, a primer charge of 2 grains of compressed
lead azide adjacent to the base charge, and an
' row tell-tale hole. Since controlled compression l' ignition charge of a suitable mixture. The base
of the charge is advantageous, it will ordinarily
charge had been loaded under a pressure of about
be preferred to precharge the explosive into a 60 5000 pounds per square inch and extended slightly
cylindrical container adapted to f_it into the hole.
beyond both faces of the wall. The charges were - '
This will obviate the hazards present in handling
brought to explosion by means of a fuse. A close- '
and pressing _exposed explosive charges under
fitting junction, impervious to high‘pressures,
shop conditions. Various methods of bringing
resulted from the expansion of thebolt'metal. .
about the explosion ‘are suitable, such as the ap 65
Example No. 2
plication >of heat, percussion, the name from a
fuse or other source, electrical methods, etc.
In Fig. 2, an assembly is shown similar to that '
of Fig. 3, with the preferred method of loading
Similarly, a threaded 7A; inch metal bolt was ‘
>screwed into another V2 inch steel plate. The
and firing illustrated more'in detail. After the 70 bore hole in the bolt end wasof % inch depth and „
0.235 inch in diameter. A cylindrical metal con
bolt S is screwed into the ñre wall 6 so that the
former extends slightly beyond the outer edge - tainer was inserted into thebore hole, said con
tainer being loaded with a. 10 grain base charge
of said wall, ametal shell 30 is inserted into the
of tetryl, and suitable primer'and ignition combore hole 26 in the bolt and contains a com
pressed base charge 28 Vof a high strength, high 75 positions. Again the base charge was such that
' it extended slightly beyond both wall edges. 'I‘he _
explosion was brought about by fuse, and a tight
joint resulted between the staybolt and the sur
rounding metal.
6 Y
Example No. 4
Heat exchange apparatus was constructed by
means of explosive staybolts. A cylindrical cata- ' '
Example No. 3
lyst chamber was spaced within a cylindricalv
steel case by means of steel staybolts 7g inch in
Additional joints were made between staybolts
and metal plates in which the tightness ofthe
within the 1%; inch steel plate forming the steel
diameter. The bolts were expanded exploslvely>
case, and within the 5A; inch steel walls defining
junctures were tested. A length of 4" diameter
extra heavy steel pipe was first taken and closed 10 the catalyst chamber. The result was a heat
exchange apparatus wherein the staybolt connec
at -both ends by welding thereon pieces of % inch
tions were pressure-tight both with respect to
boiler plate. A tube was likewise welded onto
the `heat exchange medium and the chemical
the pipe-to allow the application ofhydraulic
`liuid being treated in the catalyst chamber. The
pressure and its measurement by a gauge. Two
diiierent bolts made of the` above mentioned 15. connections between the bolts and the walls were
effected by forming bore holes 0.235 inch in diam
nickel-copper alloy were used with such a pres
eter in each end ofthe bolt, and about 5/8 inch
sure container, being screwed into opposite open
in depth. The metal defining these-holes was
ings in the two plates. Longitudinal holes were
expanded into contact with the walls to be spaced
drilled into the bolts, 0.235 inch in diameter to
depths varying from 1% inch to 1/2 inch. Charges 20 apart, by means of .an explosive capsule loaded
with a 10 grain base charge of tetryl and conven
of pentaerythritol tetranitrate were used, varying
tional primer and ignition compositions. Explo
from 5.75 grains to 9.0 grains. In some cases the
sion was brought about by means of a fuse to
explosive charge was co-extensive with the thick
cause the pressure-tight joints already described.
ness of the plate, while in others it extended
It is not essential in all cases that the stay
slightly beyond the edge or just to said edge. It
bolts and perforations be threaded as pressure
vwas found, generally, that the tightest joints
tight joints can be produced-by the process of
resulted when the explosive charge overlapped
the present invention between unthreaded bolts
both edges of the plate slightly. In these cases
and smooth walledl perforations or between stay
it was found that the metal of the vstaybolt sur
rounding the bore not only had expanded tightly 30 bolts and perforations'which are threaded’for
only a portion of the thickness of thepllate. Nor «
into contact with the wall of the perforation in
is it essential that the base chargeof the ex
the sheet but that it had even bulged slightly on
plosive extend beyond both faces of the ñre or
either side of the sheet, resulting in avery strong
pressure-tight joint. Somewhat weaker joints
’were obtained when the explosive charge did not
extend past the edge although these joints were
also satisfactorily pressure-tight. Under condi
tions where the charge extended slightly beyond
both edges of the plate, tests indicated that no
leaking occurred even under a pressure of 4800 ,
pounds per square inch.
In no case did even a
slight leak occur at a pressure less than 2200
pounds per square inch. This appears very strik
wrapper sheet. Satisfactory fluid-tight joints are
also obtained when the bolt terminates at the
plane of the exposed face of the sheet,` as illus’
trated at 2l in Fig.- 1. This has the advantage
of providing’ a smooth surface which is not cut
away to any appreciable extent by the now of
the cinders therealong. The bolt may also exl
tend beyond the face of the'ñre sheet, as shown
in Figs. 2, 3, and 4 and be upset after expansion
to provide a, rounded head 26 as illustrated in
staybolt I2 of Fig. 1.
The present invention provides an extremely
simple and rapid method of >ñtting staybolts 'so `
tightly in the boiler plates that the joints are
fluid tight at pressures 1000% to more than
ing and significant when it is realized that steam
boilers ordinarily operate at pressures around
about 225 pounds to about 250 pounds per square
Using a similar test and an explosive charge `
2000% greater than the ordinary working steam
of 10.5 grains of pentaerythritol tetranitrate, an
pressure. In the United States the boilers ordi
unthreaded nickel-copper alloy bolt was used.
After the explosive charge had been detonated, _ narily operate at a pressure between the ranges
of about 200 to> 300 lbs. per square inch, with an
the joint was found to withstand a pressure cf
average of about 225 to about 250 lbs. per square
3200 pounds per square inch without any leaki
inch. The present >invention provides a high
ness, which was the maximum pressure that
safety factor even for boilers operating at very
could be exerted on this. particular assembly.
An additional test of an annealed 18-8 chro
mium-nickel stainless steel bolt under similar
conditions showed that leakiness occurred in no
case at a pressure below 4600 pounds per square
In the immediately foregoing examples, bolts
much higher working pressures such as have been
contemplated and to a certain extent used abroad
with Working pressures in excess of 1000 lbs. per
square inch. These joints are not only fluid-tight
initially but they will remain fluid-tight in serv-~
ice.` As those skilled in the art are aware, stay
bolts are exposed in service to severe stresses »
have been used consisting of stainless steel and
tending not only to loosen the joint between the
Vthe nickel-copper alloy sold under the trade-mark
“_Monel.” It will be understood that various other 65 staybolts and the boiler plates but even to fracture
the bolt. Many boilers operate at temperatures
metals having satisfactory mechanical, metallur
up to 550° F. and even higher. These high tem»
gical and chemical propertiesv for staybolts may
peratures impose stresses on the staybolt and the
be fitted bythe process embodying the present
joint due to thermal expansions «of the metals of
invention. Such metals as aluminum, nickel and
copper; various nickel, aluminum and copper 70 the staybolts and boiler plates. Moreover, at
alloys; steel and certain steel alloys; and many ` least once each month the locomotive must be
washed out by emptying the hot water and re
others may be applicable. It is preferable that
ñlling with fresh water which sometimes is cold.
a metal for expansion in accordance with our
This invariably results in uneven -cooling of the
invention have a potential elongation value of
boiler producing very high stresses known in the
at least 20%.
75 art as wash-out stresses. The staybolts and boll- .
contribution to the boiler art in greatly reducing '
I er plates are also under static stress due to the l
such breakage and leakage. Thev ends of the bolts
steam pressure. Moreover, _particularly in boil
that are explosively expanded by the methodv em
ers of locomotives and marine vessels, the stay-.
bodying the present invention contact the."wa11s
bolts also are exposed to dynamic stresses, me
of the holes in the boiler sheets so tightly that
chanical shocks, and vibrations resulting from
the joints will remain fluid tight in service de- '
the movement of the boiler. The'movement of
spite thermal stresses due to heating, cooling,
the boiler may also impose sheer stresses from
wash-outs, etc., and mechanical stresses resulting
lwarping or wrenching oi.' the boiler assembly.
from shocks, vibration, warping, and the like. .
Thus, in locomotive boilers the weaving and
warping of the locomotive frame is transmitted 10 The present application is a division of our co
pending application Serial No. 474,480, ñled _Febto the boiler assembly and causes it also to weave
and warp. The Association of American Rail
Although the invention has been described and
illustrated in connection with certain-speciñc em
roads and various engineering societies, including
the American Society of Mechanical Engineers
and the American-Society for Testing Materials, 15 bodiments, it will be appreciated that many modi
iications maybe made therein without depart
as a result of many' years of experience and re-'
‘ ing from the scope of the invention as deilnedin
search, have developed codes and speciñcations,
-deslgned to reduce staybolt breakage and leakage
the following claims.
to a minimum. See for example, the A. S.
We claim:
Boiler Construction Code, 1940 edition, and the 20 - 1. A metallic staybolt having circular ends
adapted for insertion into circular holes in re
specifications lof _the .Association ofy American
'spective plates, whereby said plates are to. be
Railroads, 1939 revision.` Some of-:tlie more im
portant provisions relating to staybolts appearing ' joined and maintained at a predetermined dis
' tance apart, bores provided in each of said ends
in these codes and specifications are as follows:
25A of sumcient depth to extend at least to the inner
,Physical and mechanical properties v .
face of the respective plates, and a charge of high
velocity explosive substantially filling at least one
Tensile strength: 47,000 lbs. per sq. inch mini
of said bores, said bores >being open- for escape of
Yield point :` 60% oil the tensile strength as a. min- Y
the products of explosion.
30. 2. A metallic staybolt having` circular ends
Elongatlon in 8 inches: 28% minimum.
adapted for insertion intocircular holes in re
Reduction in area: 48% minimum.
Maximum allowable stress on staybolts: 7,500 lbs.
joined and maintained at a predetermined dis
spective plates, whereby said` platesl are to« be
tance apart, concentric bores provided in each of
said ends of suillcient depth to extend atleast
to the inner face of the respective plates, a. cap
per sq.,inch and 8,000 lbs. per square inch', de
pending upon the staybolt length, design and
Permissible variation in size: The staybolt must
be truly round within 0.01 inch and the diam
. sule containing a charge of high velocity explosive
substantially illling at 'least one of said bores, said
bores being open for fescape of the products of
mtcêre than 0.020 inch over the specified diam 40 explosion, and means for detonating said charge.>
e r.
`3. A metallic staybolt having circular threaded
Tests: steybeits shan be tested et least every . ` ends adapted for insertion into circular threaded
month and after every hydrostatic test.
holes vin respective plates, whereby said plates are
to be joined and maintained at a predetermined
The hydrostaticy test shall be made at least
every twelve months and it must `be carried out 45 distance apart, each of said ends being- provided
with a concentric bore of suiiicient depth to ex
at 25% greater pressure than the working steam
pressure. In this'connectionit is signiñcant that ' tend at least to the inner face of the respective
eter shall not be less than 0.005 inch over nor
plate, a capsule containing a charge of high ve- ~
the staybolts iitted in accordance with the pres
locity explosive substantially filling each of said
ent invention will> stand over pressures from 8 to
50 bores, said bores being open for escape oi the
_ i6 times that specified for the hydrostatic test.
Even vwith the precautions taken in these speci
ilcations and codes breakageof the staybolt and
leakage `between the staybolts and the boiler
plates have occurred‘in normal operation of boil-- -
ers. The' present invention makes an important 55
products of explosion, and means for detonating
said charges.
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