Elbow forming in jacketed pipes while maintaining separation between core shape and jacket pipe

Gardner, J. N.

Nielson, T. L.

English

NASA Technical Reports Server

8 f A- 
n accordance with the procedures agree 
and Code USI, the attached NASA-awned U, 8 ,  P 
folswarded for abstracting and announcement i n  
rtng infomation i s  prwidedt 
m Patent NO. 8 
overnment or 
Corporate Employee 8 
8 
t 
https://ntrs.nasa.gov/search.jsp?R=19710015203 2020-03-17T02:57:39+00:00Z
Dec. 15, 1970 T. O. PAINE 3,546,9 1 7 
ADMINISTRATOR OF THE NATIONAL AERONAUTICS 
A N D  SPACE ADMlNlSTRATlON 
TESHNIQUE OF ELBOW BENDING SMALL JACKETED TRANSFER LINES 
Filed Sept. 30, 1968 
FIG. I 
FIG. 2 
ATTORNEYS 
3,546,9 17 United States Patent Ofice ,,,,,,., ...* , ,,,, 
3,546,917 
TECmPQUE OF ELBOW IBENMNG SMALL 
JACKETED TRANSFER LINES 
T. 0. Paine, Depnty Administsator of tbe Nationall Aero- 
nautics and Space Administralio~, with respect to an 
invention of James N. Gardner and Thomas L. Nielson, 
Soarks. Nev. 
A 2 
Filed Sept. 30, 1968, Ser. No. 763,868 
Pnt. CIl. B21d 9/00 
U.S. CI. 72-369 5 CPaims 
ABSgRACT OF THE DISCLOSURE 
A method of forming elbows or bends in a length of 
jacketed pipe, such as a cryogenic transfer line is dis- 
closed. Two lengths of tubing are coaxially assembled 
and the annular space between them is filled with a 
congealable liquid such as water. The water is frozen, 
preferably very quickly, by passing liquid nitrogen 
through the core of the inner tube. The assembly is then 
bent to the desired radius using conventional pipe bend- 
ing techniques while maintaining the water frozen. Satis- 
semblies are fabricated by forming a coaxially asesnibi> 
of two pipes. The annulus between the pipes is pluggcci 
a t  one end and is filled with a congealable liquid. The liq- 
uid is congealed and the assembly bent to the desired 
radius while the liquid in the annulus is maintained in 5 the congealed condition. 
The invention will now become better understood by 
reference to the following detailed description wben con- 
sidered in conjunction with the accompanying drawings. 
10 BRIEF DESCRIPTION O F  THE DRAWINGS 
FIG. 1 is a schematic cross sectional view 04 a jacketed 
pipe illustrating the first part of the inventive method; 
FIG. 2 is a perspective view of a straight length of 
15 jacketed pipe in a bending apparatus; 
FIG. 3 is a further perspective view of the apparatus 
of FIG. 2 showing the pipe in posirion after formation 
of a 90' elbow. 
FIG. 4 is a side view of a finished bent-jacketed pipe 
20 according to the invention. 
DESCRIPTION O F  THE PjREFERRED 
EMBODIMENTS 
factory spacing between the G e r  and outer tubing is Referring now to FIG. 1, there is shown a length of 
maintained for bends up to about 90". Elbows of pipe UP 25 jacket pipe 10 and a greater length of core pipe 12. The 
to about 2% inch in outside diameter can be fabricated core pipe 12 is inserted into the jacket pipe 10 so that: a 
on site with portable bending machines. short length extends from each end of the jacket pipe PO. 
These pipes are coaxially assembled and maintained in 
concentric separation by means of perforated end spacers 
ORIGIN O F  INVENTION 30 14and16. 
A liquid tight seal 26) is formed at one end of the an- The invention described herein was made in the per- 
nulus 18 between the pipes by wrapping core formance of under a NASA 'Ontract and is sub- 12 with adhesive cloth tape until the tape ove~laps the ject to the provisions of Section 305 of the National jacket pipe The nozzle end 23 of a water 30 feeds Aeronautics and Space Act of 19-58> Public Law 85-568 into the open of the annulus 18, one end of the core (72 Stat. 435; 42 USC 2457). 35 pipe is flared at  22 and receives a flared tube fitting 24. 
BACKGROUND O F  THE INVENTION A liquid nitrogen line 26 is connected to the fitting 24 
Field of the invention and the other end of the line 26 is connected to a source 
of liquid nitrogen at  -320" F. housed in Dewar container 
This invention relates to the bending of assemblies of qo 28. 
concentric tubing and more particularly to a method for In the fabrication of a jacketed pipe elbow according 
forming elbows in jacketed pipes while maintaining the to the technique of the invention, a len& of core tubing 
separation between and the shape of the core and jacket 12 and jacket tubing 16) are cut to the correct respective 
pipes. lengths. The core tubing 12 is flared at one end 23 to 
Description of the prior art 45 receive a flared tube fitting 24. The outer or jacket tub- 
increasing number of applications such as con- ing 10 is slipped over the inner tubing, positioned so t h d  
swuction of heat transfer or cryogenic facilities in the the core tubing extends from each end of the jacket tub- 
aerospace, ship building, chemical and food processing in- ing and the assembly is coaxially a b e d  by inserting per- 
dustries requires extensive use of jacketed piping. Often forated spaces 14 and 16 at each end of the annulus 18. 
bent lengths of particular dimensions and radius are re- 50 Cloth tape is wrapped from the inner to the outer tubing 
quired. The fabrication of bent, jacketed pipe requires to provide a watertight seal ZO. 
a different radius bend for the jacket and the core pipe The liquid nitrogen line 26 is connected to the fitting 
2nd the on site fabrication of these bent lengths has been 24. The assembly of tubing is held in an incline? position 
time consuming and expensive. and water is fed through the water nozzle 23 into the 
In one standard technique, the inner and outer tubes 55 ~ ~ D U ~ U S  114. The liquid nitrogen is turned on and flow? 
are separately bent to the required radius. ~h~ outer tube through the core tubing freezing the water. The assembly 
is then split longitudinally and the bent inner tube is is then placed in a conventional pipe bender and iongi- 
placed inside the two halves of outer tube, and the seams tud ina l l~  bent lo the desired radius. 
are welded closed. Referring now to FIGS. 2 to 4 the concent] ic assembly 
60 of pipes containing a frozen ice annulus is placed in x OBJECTS AND OF THE INVENTION conventional radial pipe bending machine. The principal 
It  is an object of this invention to provide a quick and operating elements of the machine include a loxgitudirlaIljl 
inexpensive technique for bending concentric assemblies curved die 40, a holding shoe 42 and a stiR back mcm- 
of tubing to a selected radius. ber 44. 
Yet another object of the invention is the provision of 65 The curved die 40 as shown has a hcnlispherical-shaped 
a technique which is capable of on site production of recess 46 along its outer length adapted to engage the 
jacketed piping in a greatly reduced fabrication time outside surface of the outer pipe 10. The ci~rved die 40 
and at a considerably reduced cost. is mounted for rotation on a turntable 48. A. rotation 
These and other objects and advantages of the inven- arm 50 is attached to the die 40 and lo the turntable 48. 
tion will become readily appreciated as the description 70 The holding shoe 42 is mounted on this arm and includes 
proceeds. a jaw 52 having grooved edges for siidingly gripping the 
According to the invention, bent, concentric pipe as- arm 50 and a screw member 54 for moving the 1 2 ~ ~  toward 
3,546,917 
3 4 
the corl ed die 40. The jaw 52 receives a holding shoe into ice, which expanded and projected a slight amount 
dlc 56 hav.rng an outer hemispherical recess to grip the from each end of the annulus. 
lace of the outer pipe PO opposite the curved die 46). The assembly was quickly placed in a conventional 
The stiff back member 44 comprises a straight die 60 pipe bender and with the use of a semicircular die was 
having a hemispherical pipe engaging recess 62. The stif£ bent to an angle of 90". A midpoint of the bend was 
b3ck 1s moilntetl on a track 64 and is adapted on turning sectioned and examined, and satisfactory spacing was 
of a,iew member 66 to engage a section of the pipe 10 evidenced. All wall surfaces were smoolh with no evl- 
sdjdccnt the holding shoc die 56. dence of wrinhling or material upset. 
To complete the bending operation the pipe 10 is placed Many fluids may be utilized as the coagealable liquid 
~n th- recess 46 of the curved die 40 and the holding to be filled into the annulus. For example, saline solu- 
sboc cite 56 1s moved inwardly to engage the pipe at a tions or organic hydrocarbon or silicone liquids may be 
golnt correspond~ng to the initial curvature of the desired uscd and if desired these liquids may be recovered and 
bend The siiR back die 60 is also moved into engagement reused. The liquid seal for the annulus may be provided 
w,th the p i p  10. by soft deformable materials, such as hydrocarbon waxes 
A hoiizontal force is applied to the arm 50 and the 15 or putty like materials. The seal inay be inserted into 
61irved die 40 and holding. shoe 42 rotate laterally and both ends of the annulus and the liquid added through a 
mo11e the pipe past the stationary stiff back member 44 port drilled in the outer tubing. 
vcklch bends the pipe PO to conform the curved die 40. High pressure sealing arrangements may also be uti- 
As show17 rn FIG. 3 the curved die 40 and holding shoe lized. As the liquid freezes and expands, this will place 
42 have been rotated 90" and a 90" bend has been formed 20 the pipe walls in tension which can further alleviate ma- 
in the plpe. Many suitable radial bending machines are terial upset and wrinkling of the inner bend. However, 
avaiiablc on t\e market such as the Parker Tube Bender. it is possible in some cases that the excess pressure from 
With small-s &meter piping the assembly can be bent the transverse expansion of the liquid will be transferred 
by manual aciivation of the arm 50. With larger diameter to the pipe walls and could cause collapse of the inner 
tubing, pneumatic or mechanical actuation of the arm is 23 tubing or rupture of the outer tubing. Therefore, it is 
nequlrecl preferred to allow all expansion to proceed laterally and 
To complete the fabrication of the elbow, the temporary allow the frozen liquid to push out at least one end of 
spawrs 14 and 16 are removed and end place washers the annulus. 
are welded to both the inner and outer tubing. Vacuum Congealing the liquid in the annulus may be accom- 
bo-3:s a-i: then welded an each end of the outer jacket. 30 plished by any suitable refrigeration means, for example, 
A hole is then dlilPed through the vacuum bosses and the placing the assembly in a refrigerator cabinet or by flow- 
orries jacket to complete fabrication of a cryogenic trans- ing a heat exchange liquid in direct or indirect heat ex- 
fcr ilne elbow change relationship with the inner wall of the core or the 
As a restilt of forming a bend in a jacketed pipe, it is outer wall of the jacket tubing. It  is preferred to quickly 
apparent that [he outside pipe will contribute a larger 35 effect the freezing of the liquid annulus by flowing a corn- 
poltion of its lcngth to the elbow than in the smaller pressed, liquified gas through the core. This is a very con- 
radrus of cilivature suffered by the core pipe. Therefore, venient and simple technique and it results in a quick 
duiiirg the bending operation there will be relative move- freezing of the liquid. The compressed gas vaporizes with 
nen t  between the pipe walls of the core pipe and the a large absorption of heat from the surroundings with 
jacket ppe. It has been found that the annulus of ice 40 quick and even freezing of the liquid. With slow cooling, 
does not form a high friction bond with the walls. The crystal formation and freezing may proceed first at the 
ace readily separates from the wails of the pipes and ends and block off the expansion of remaining liquid as 
allows them to slide past the ice as the pipes are pro- it freezes with again a possibility of transferring excessive 
gressively bent in the bending machine. Another inherent or uneven forces laterally to  the walls of the tubing. Suita- 
restilt of bending a cylindrical pipe is to bend the inside 45 ble cryogenic liquids are compressed and liquified nitro- 
gadids less than the outside radius and to crowd the inner gen, helium, hydrogen, and the like. Nitrogen is preferred 
Send wltb excess material which can result in material since it is a readily available cryogenic liquid and is non- 
upset and the formation of wrinkles on the inner or outer toxic and can therefore be vented to the atmosphere with- 
walls. However, w ~ t h  the assembly of the invention which out hazard topersonnel. 
contains a rigid and incompressible annulus of ice as the 50 The elbow bending method of the invention has been 
tvbes slide past this rigid body of ice the wall surfaces successfully utilized for on site fabrication of jacketed 
ale srnoot~hcd and stretched to prevent the formation of piping. Longitudinal bends of over 90" should preferably 
wiri~hles. Furthermore, the annulus of ice acts as a die be avoided, due to the danger of exceeding the elastic 
with res2ect to the core pipe and prevents any portion of limit of the outer bend and causing excess crowding of 
i t  from going out of round during the bending operation. 55 material a t  the inner bend. Portable bending machinery 
The following example is offered by way of illustra- for on site utilization of the method is usually only effec- 
tioil and is not intended to in any way limit the invention. tive to bend pipes having an OD of no more than about 
EXAMPLE 3 inches and wall thicknesses of less than about 0.125 inch. 
A three and one-half foot length of 1% OD sleel tubing 
a.~d a four loot lergth of 1 inch OD steel tubing were cut 
fron: tubing stock having a wall thickness of 0.065 inch. 
The inner tubing was flared at one end and the outer 
tubing was slipped over the inner tubing so as to be 
positioned about 5 inches from each end of the inner 
t~abing. The tubes were concentrically located by insert- 
ing perforated spacers at each end of the annulus. Cloth 
tape was wrapped from the inner tubing to the outer 
tubing to provide a water seal. 
A liquid nitrogen line was connected to the flared end 
of the inner tubing through a flared end fitting. The 
assembly of tubing was inserted into a vise in an inclined 
position, taped end down. Water was poured into the 
annulus until it was filled. Liquid nitrogen at -320" F. 
was fiocved through the core quickly freezing the water 
It  is to be understood that only preferred embodiments 
of the invention have been disclosed and that numerous 
alterations and modifications and substitutions are permis- 
sible without departing from the scope of the invention 
as defined in the following claims. 
What we claim is: 
1. A method of forming a bend in a concentric as- 
sembly of pipes comprising the steps of: 
inserting a longer core pipe into a length of jacket pipe 
to  form an annulus therebetween such that a portion 
of the core pipe extends from each end of the jacket 
pipe; 
concentrically spacing said pipes by inserting a per- 
forated; temporary toroidal end spacer near each 
open end of the annulus between said pipes; 
5 6 
forming a low pressure water seal a t  one end of said a static body of water filled into the antrriiris through 
annulus; the open end thereof; 
filling the annulus between the pipes with water through refrigerating means comprising a source of liquid ni- 
the open end of said annulus; trogen communicating with the core pipe through 
quickly congealing the water to form a rigid, con- said fitting for congealing said water to form a 
tinuous body of ice in said annulus by flowing liquid solid, rigid, slidable body of ice in said annulus feu 
nitrogen through said core pipe; and forming concentric radii on bending said pipes. 
simultaneously bending the pipes at a locatiton between 4. A method according to claim 1 wherein said ?ow 
said ends while maintaining the ice in the annulus pressure water seal is formed by closing the end of the 
in a congealed and rigid condition. 10 annulus between said pipes with adhesive tape. 
2. A method according to claim 1 in which the tubing 5. An assembly according to claim 3 in which said 
has an outside diameter of no more than about 3 inches. means for forming a temporary water-tight seal conIpriseb 
3. An assembly for forming a jacketed pipe elbow Corn- a body of adhesive tape disposed over the open end of prising: the annulus between said pipes. 
a first length of cylindrical core pipe having a flared 15 
end; 
a flared end fitting secured to said end; 
a shorter length of a larger diameter cylindrical jacket 
References Cited 
UNITED STATES PATENTS 
pipe surrounding said core pipe forming an annulus 
and spaced such that each end of said core pipe ex- 20 3,343,250 911967 Berto et al. 72-369 
- - 
tendstherefrom; 
temporary, toroidal perforated end spacer means in- A. LARSQNy Primary Examiner 
serted into said annulus near the ends thereof for co- 
axially spacing said core and jacket pipes; U.S. Cl. XR. 
means for forming a temporary water tight seal a t  25 2 9 4 2 3  
the end of the annulus opposite said flared end; 


Technique of elbow bending small jacketed transfer lines Patent

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server