Flange joint

The invention relates to a flange joint for use at relatively low pressures, whereby the pipe to be joined is provided with a peripheral shoulder against which a flange abuts, the flange being tightened by means of clamping bolts. For each clamping bolt is provided a separate flange piece which abuts against only a small portion of the peripheral shoulder.

BACKGROUND OF THE INVENTION 
The present invention relates to a flange joint in which the end of the 
pipe to be joined is provided with a peripheral shoulder against which a 
flange to be tightened by means of bolts or similar is adapted to abut. 
Conventional techniques relating to flange joints involve the arrangement 
of a flange around the pipe end which flange abuts against the pipe end 
shoulder continuously around the pipe. In general the flange is made in 
one piece. In joints to fixed connections, such as pumps, provided with 
threaded bores for clamp bolts the flange is relatively often made of two 
halves in order to facilitate the installation. 
In each case specially dimensioned flanges are required for each pipe size, 
in addition to which the division and the number of clamp bolts differ. An 
example of this is the standard SAE (J 518 c) which for pipe sizes from 
1/2" to 5" requires fifteen different flanges. Moreover, the flanges are 
to a great extent used in connections with relatively low pressure, less 
than about 50 bar, for example, in water pumps, on the suction side in 
hydraulic applications, etc, in which cases only a fraction of the holding 
capacity of the flange is utilized. 
The object of the present invention is to provide a new flange joint which 
overcomes the above-mentioned disadvantages. 
SUMMARY OF THE INVENTION 
The flange joint according to the invention is mainly characterized in that 
for each clamp bolt is arranged a separate flange piece adapted to abut 
axially against the peripheral shoulder in the pipe end. 
Thus, the individual flange pieces each abut only against a relatively 
small portion of the peripheral shoulder in the pipe end which, however, 
is quite sufficient at rather low pressures of up to about 50 bar. 
However, the invention can also be applied at higher pressures by 
inserting between the clamp bolts and the flange pieces a continuous 
support plate which provides an additional holding capacity. 
An essential advantage of the invention is that the individual flange 
pieces can be made identical with each other and, consequently, can be 
used for practically all existing pipe sizes. In addition, a substantial 
saying of material is achieved as compared to continuously encircling 
flanges. The flange pieces are further inexpensive to manufacture in 
present automatic machines, especially if they are made of two cylindrical 
sections each having a different diameter. In this case the flange piece 
abuts axially against the peripheral shoulder of the pipe end with the end 
surface of the section of a larger diameter and preferably radially 
against the shoulder with the mantle surface of the section of a smaller 
diameter. 
A flange joint according to the invention is also easy to dismount in the 
radial direction, for example, in the case of four flange pieces spaced 
uniformly around the periphery of the pipe end, by removing one flange 
piece and by easing off the clamp bolts on the remaining pieces. 
Preferably the individual flange pieces can be shaped eccentrically in any 
of the following manners: 
both cylindrical section in the flange piece are concentric while the 
through bore is eccentric; 
the cylindrical section of the flange piece of a larger diameter and the 
through bore and concentric while the cylindrical section of the flange 
piece of a smaller diameter is eccentric. 
The last-mentioned embodiment has the advantage of requiring a minimum of 
material and space. A common feature in the different eccentric 
embodiments is that an exact abutment of the flange pieces against the 
peripheral shoulder in the pipe end is achieved regardless of the 
variation in the width thereof or of irregularities of the placement of 
the threaded bore holes into which the respective clamp bolts are intended 
to be screwed. Any errors in division can be easily compensated. Other 
than cylindrical shapes can, of course, also come into question. 
If the clamp bolts are provided with two oppositely directed threaded 
sections, each flange piece can advantageously be provided with an inner 
threading, whereby the flange piece will be pressed against the peripheral 
shoulder in the pipe and through said inner threading. This embodiment has 
a certain advantage over flange pieces with a plain bore because the play 
between the flange piece and the threads in the bolt is minimal, owing to 
which side forces occurring during tightening are somewhat better taken up 
by the clamp bolt. However, it should pointed out that neither a plain 
bore in the flange pieces generally does not cause problems in this 
respect because the peripheral shoulder of the pipe end usually is rather 
thin (in the axial direction of the pipe). 
The flange joint according to the invention is primarily intended for use 
in connections in which a pipe end is to be joined to a fixed connecting 
piece provided with threaded bores into which the clamp bolts are intended 
to be screwed. However, the invention is also applicable in scarfed joints 
if a holding ring preventing the flanges from sliding radially outwards is 
arranged round the cylindrical sections of the flange pieces of a smaller 
diameter.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
The end of the pipe to be joined is designated by numeral 1, and the fixed 
connection piece to which the pipe is to be joined, for example, a pump is 
denoted by numeral 11. The pipe 1 is in its end abutting against the 
connection piece 11 provided with a peripheral shoulder 2. The joint is 
tightened by means of bolts 3 which are screwed into bores in the 
connection piece 11, said bores, however, not being shown in FIG. 1. 
Contrary to hitherto existing flange joints, the invention does not employ 
a flange abutting continuously against the shoulder 2 around the pipe 1 
but, instead, a separate flange piece 4 for each clamp bolt 3. In the 
embodiments shown in the drawings said flange pieces comprise two 
cylindrical sections 5 and 6 of different diameters so that the end 
surface 7 of the larger cylindrical section 5 abuts axially against the 
shoulder 2 while the outer mantle surface 8 of the smaller cylindrical 
section 6 abuts radially against the shoulder 2. As appears clearly, e.g., 
from FIG. 2, the flange pieces 4 abut in total only against a relatively 
small portion of the shoulder 2 which, however, is quite sufficient for 
the pressure primarily concerned herein, namely pressure of up to about 50 
bar. A sealing between the pipe end 1 and the connection 11 is provided in 
the conventional manner by means of a sealing ring 10 accommodated in a 
groove in the end surface of the pipe end. 
The same flange pieces 4 can be used for a plurality of different pipe 
diameters. Thus, the earlier mentioned seventeen different flanges for the 
standard SAE (I 518 c) can be substituted by only six different flange 
pieces of the kind disclosed herein which, moreover, are easy and 
inexpensive to manufacture while utilizing existing automatic machines. 
FIG. 2 shows an embodiment in which both cylindrical sections 5 and 6 in 
the flange pieces 4 and the bore 9 passing through them are all concentric 
with each other. 
FIG. 3 shows an embodiment of the invention in which each flange piece, 
denoted 4a, is provided with concentric cylindrical sections 5a and 6a 
while the through bore 9a is eccentrically arranged. 
FIG. 4 shows an embodiment in which each flange pieces 4b has its 
cylindrical section 5b of a larger diameter and the through bore 9b 
arranged concentrically with each other while the cylindrical section 6b 
of a smaller diameter is eccentric. FIG. 5 further shows an embodiment in 
which the corresponding parts 5c, 6c and 9c of the flange piece 4c are all 
eccentric with respect to each other. These eccentric embodiments always 
permit, through a suitable rotation, an exact fitting-in against the 
shoulder 2. In the embodiment according to FIG. 5, the cross-sectional 
circles of the cylindrical sections 5c and 6c are tangent to each other, 
which results in a minimal consumption of material and a minimal need for 
space. When the bore hole in the embodiments according to FIGS. 3 and 5 is 
suitably positioned, it is also possible to turn the flange piece entirely 
free of the peripheral shoulder 2 in the pipe end. 
FIG. 6 illustrates an alternative embodiment in which a special screw 3d is 
utilized which is provided with two section 12 and 13 threaded in opposite 
directions. The bore in the flange piece 4d is provided with a threading 
corresponding to the threading 12 in the screw 3d. The joint is tightened 
through the thread portion 12 and the corresponding inner threading in the 
flange piece 4d while turning the screw 3d. This embodiment has the 
advantage that the play between the thread 12 and the inner thread of the 
flange piece is minimal, owing to which side forces occurring during 
tightening are more uniformly distributed over the entire screw, which is 
of advantage if the construction is relatively high. 
In FIG. 7, the afore-mentioned fixed connection 11 is replaced by a welding 
nipple 11a, which makes the connection 11a, 11b, conventional scarf joint. 
The connections is in this case tightened by means of a nut 14, and the 
separate flange pieces in the connection are held in place against radial 
movement outwards by means of a holding ring 15 which is arranged outside 
the sections 6 of the flange pieces of a smaller diameter. 
In the embodiment according to FIG. 8, a support plate 16 is placed between 
the heads of the clamp nuts 3 and the flange pieces 4. Said plate is, on 
one hand, provided with a central hole for threading on the pipe end 1 
and, on the other hand, with holes for the clamp bolts 3. In this way the 
connection will be better held together in the radial direction, which 
makes it possible to use the separate flange pieces 4 in connections of 
higher pressures requiring a correspondingly greater tightening moment.