Conduit closure system for closing a conduit having a gripless inner surface

A system is provided for closing a conduit having a gripless inner surface, comprising a sealing wall and an annular seal disposed between the wall and the conduit. Beams connected to the wall by adjustable tie-rods, disposed bearing against the inlet end of the conduit, support and immobilize said sealing wall.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a system for closing a conduit having a 
gripless inner surface, which is to be tested under pressure from an open 
inlet end. 
Such a system is useful, for example, for periodic testing, by application 
of an overpressure, of the resistance of steam driers-superheaters in 
nuclear power stations. In fact, for carrying out an overpressure 
resistance test of such an apparatus, it is necessary to close the whole 
of the conduit which opens into this apparatus and in particular the 
conduit which in normal use brings the steam into the apparatus. Since it 
is important to check, at the same time, the pressure resistance of the 
connection between the drier-superheater and this conduit, the closure 
must be provided in the conduit beyond this connection, which corresponds 
therefore substantially to the open end of the conduit allowing the input 
of pressurized fluid during testing. In most cases, there is no grip on 
the inner surface of the conduit, which is therefore generally smooth 
coming straight from the braziery. 
2. Description of the Prior Art 
To close a conduit with a smooth inner surface, it is known to use a 
closure system formed essentially of an inflatable envelope, made for 
example from rubber, of a substantially cylindrical shape when it is 
inflated, and whose wall bears on the smooth inner surface of the conduit, 
under the effect of the pressure of a fluid with which the envelope is 
inflated. Sealing rings are generally formed on the outside of the walls 
of the envelope in contact with the inner surface of the conduit, so as to 
provide good sealing. Although such a system gives satisfaction in the 
case of a conduit of moderate diameter subjected to a pressure difference 
also moderate, it is unusable in the above described application, relating 
to pressure testing of a drier-superheater. In fact, in this case, the 
diameter of the conduit to be closed is generally of the order of 1.20 m 
and the testing pressure of the order of 20 bars. Now, in the case of a 
conduit of a diameter of 1.20 m, the maximum admitted pressure difference 
for an envelope of the above type is of the order of 0.3 bar. For higher 
pressure differences, adhesion of the envelope to the inner surface of the 
conduit is no longer ensured, and such an envelope cannot then be suitable 
for solving the problem raised. 
For this, a sealing wall could be placed inside the conduit, an annular 
seal possibly inflatable being placed between the two. This would require 
the fitting of fixing means to the inner surface of the conduit, so as to 
maintain the wall in position before testing and immobilizing it so that 
it does not move under the action of the forces exerted on the wall during 
testing. Now, for questions of safety, it is not tolerable to take the 
risk of damaging the inner surface of the conduit, which must remain in 
its initial condition during and after testing. Moreover, a closure wall 
dimensioned so as to resist and not be deformed under the action of such 
stresses would be very heavy and so difficult to install inside the 
conduit, in a position difficult of access for remote from the inlet end. 
The present invention aims at overcoming the above drawbacks by providing a 
closure system for a conduit having an inner gripless surface system which 
is capable of withstanding very high pressures in large diameter conduits, 
which requires the installation of no fixing means on the inner surface of 
the conduit and which is easy to position. 
SUMMARY OF THE INVENTION 
For this, the present invention has as object a closure system for a 
conduit having an inner gripless surface to be tested under pressure from 
one open inlet end, which system includes a sealed wall disposed inside 
the conduit, at a distance from the inlet end, for closing the conduit, an 
annular seal disposed between the wall and the inner surface of the 
conduit, means separated from the wall and connected thereto by connecting 
means for supporting it and preventing it from being deformed under the 
action of the pressure, disposed on the outside of the conduit, before its 
inlet end. 
In the system of the invention, the means for supporting the sealing wall, 
which make this latter capable of withstanding high pressures, being 
placed outside the conduit before its inlet end, it is easy to hold them 
in position before testing and to immobilize them during testing without 
damaging the inner surface of the conduit. Since the sealing wall in 
itself, separated from the supporting means, may be dimensioned so as to 
be relatively light, it is easy to install inside the conduit. 
Advantageously, the sealing wall is demountable. 
Thus, in the case of driers-superheaters where the inside of the conduit to 
be closed is only accessible by an operator who has passed through a 
manhole of reduced diameter, it is sufficient to provide elements forming 
the sealing wall manipulable by hand for using the system of the 
invention. 
In the preferred embodiment of the system of the invention, the inlet end 
of the conduit is in a cross sectional plane of the conduit and the means 
for supporting the wall are support beams disposed parallel to this plane, 
bearing on the inlet end. 
In this case, the force exerted on the sealing wall by the testing 
pressure, during testing, is transferred through the connecting means and 
the supporting beams to the end of the conduit itself. In general, this 
latter is fairly resistant so that there is no need to provide other 
immobilization means during testing. 
The annular seal may be an inflatable seal. 
Thus possible variations of the annular gap separating the wall from the 
inner surface of the conduit may be accomodated without difficulty during 
inflation of the seal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The closure system which will now be described is used here for 
periodically testing the pressure resistance of a nuclear power station 
steam drier-superheater, and of a part of a steam intake conduit connected 
to this apparatus. 
In FIGS. 1 to 4, only the parts 10 of the drier -superheater connected to 
conduit 1 with axis 20, to be closed, are shown. The inner surface of 
conduit 1 is smooth and offers no grip. Conduit 1 is in communication with 
the drier-superheater by its open inlet end 2. 
A sealing wall 3 is disposed inside conduit 1 at a distance from the inlet 
end 2. It includes a rigid cylindrical girdle 31, an assembly of bars 32 
mounted on girdle 31 and forming therewith a rigid frame on which an 
assembly of plates 33 is mounted so as to form a continuous wall. 
The rigid cylindrical girdle 31 of the sealing wall 3 is here demountable 
and includes an assembly of elements substantially in the form of an arc 
of a circle, assembled together by known means such for example as nuts 
and bolts. The cylindrical girdle 31 is dimensioned so that it fits, with 
a small clearance, in the cross section of conduit 1, the gap between the 
two being filled, as shown in FIGS. 1 and 3, by a hollow annular seal 4, 
here of elongate section parallel to the axis 20 of conduit 1. The hollow 
annular seal 4 is inflatable by means not shown because they are 
conventional. Collars 35, projecting with respect to the cylindrical 
girdle 31, serve for precentering the system in the pipe and immobilize 
the annular seal 4 in directions parallel to the axis 20 of conduit 1. 
The bars 32, whose section is in the form of a T, are mounted on the girdle 
31 so that their end parts corresponding to the cross-piece of the T are 
held in contact with the girdle 31 by known assembly means, the parts 
corresponding to the shank of the T being turned towards the inlet end 2 
of conduit 1. 
The parts of bars 32 corresponding to the cross-piece of the T and turned 
towards the inlet end 2 of conduit 1 include recesses 320 adapted for 
receiving the plates 33, here made from metal. FIG. 2 shows the wall 3 
during mounting, before fitting of plates 33, partly shown in their 
mounted position in the right-hand half of FIG. 4. In this figure, the 
hatched zones of plates 33 correspond to the zones bearing on the recesses 
320. 
After fitting of the plates, in the condition shown in FIG. 3, a deformable 
sheet 34, here made from rubber, is positioned. 
In sheet 34 openings 340 are formed for clearing the parts of the bars 32 
corresponding to the shank of the T, projecting towards the inlet end 2 of 
conduit 1. Sheet 34, shown partially in the left-hand half of FIG. 4, is 
thus applied to the flat parts of the sealing wall 3 so as to ensure good 
sealing thereof. Sheet 34, as well as plates 33, are held in position by 
known means, here retaining plates 341 and screws 342, as is shown in FIG. 
5. 
The projecting parts, corresponding to the shank of the T of the bars 32 
are connected in a way known per se to adjustable tie-rods 6, also of 
known type, and these tie-rods 6 are connected to support beams 5, 
disposed here parallel to the cross-sectional plane of conduit 1 which 
coincides with its inlet end 2 and bearing thereon. 
Beams 5 are held in position at the inlet end 2 by known means, here lugs 
51 connected by screws 52, shown in FIGS. 1 and 3. 
The support beams 5 are disposed parallel to bars 32 so as to simplify the 
arrangement of the adjustable tie-rods 6. Here, as is shown in FIG. 3, 
beams 5 have a substantially H section, a part 51 extending the central 
cross-piece of the H projecting towards wall 3 and connected to the 
adjustable tie-rods 6. 
Conventionally, the support beams 5 have the general shape of a rocking 
lever, i.e. their section is wider at the center than at the ends bearing 
against the inlet end 2, which lightens the weight thereof. 
The system which has just been described functions as follows. The 
inflatable seal 4 is inflated after positioning thereof and of the sealing 
wall 3, facilitated by the fact that the sealing wall 3, whose 
installation inside the conduit and at a distance from the inlet end 2 is 
relatively delicate, is relatively light since it has been dimensioned 
taking into account the fact that it is supported, during pressure 
resistance testing by the support beams 5. For pressure resistance 
testing, water is fed into the drier-superheater at a pressure of 20 bars. 
Because the gap between the sealing wall 3 and the inner surface of 
conduit 1 is small, the inflatable seal 4 may withstand such a pressure. 
The sealing of wall 3 is provided by sheet 34 which, under the action of 
the water pressure is applied against bars 32 and plates 33. Finally, the 
forces resulting from the pressure applied to wall 3 are transferred, 
through the tie-rods 6, to the support beams 5 which prevent the wall 3 
from being deformed and immobilize it in the position in which it was 
mounted. The support beams 5 bear against the inlet end 2 of conduit 1, 
the resultant of the forces due to the testing pressure being applied in 
the direction of axis 20. Thus, the lugs 51 and screws 52 are subjected to 
no force related to the test pressure and may be dimensioned solely for 
holding the support beams 5 in position before testing the test pressure 
is applied from the left hand side of the sealing wall 3. 
When the test is finished, the assembly may be disassembled, and the walls 
10 of the drier-superheater, as well as the inner surface of conduit 1 are 
intact, free of any damage related to the testing, except for lugs 51 
which, considering their position inside the drier enclosure and their 
small dimensions, related to the fact that they are only useful for 
positioning, are not troublesome. 
In the situation which has just been described, the fact is used that the 
conduit 1 has an inlet end 2 which advances inside the drier enclosure and 
which corresponds to a cross-sectional plane of the conduit. This is 
particularly convenient so that the support beams 5 bear against this 
inlet end 2 during pressure resistance testing. This is however not 
obligatory and, in different situations, where it is not possible to make 
use of such an advantage, the system of the invention remains still 
advantageous, to the extent that the means for supporting and immobilizing 
the sealing wall, which means are necessarily heavy and which must be 
firmly fixed, are placed outside the conduit, so in a larger volume than 
that of the conduit, where it will always be easy for a man skilled in 
that art to find gripping means for immobilizing these support means. 
In the embodiment which has just been described, an inflatable seal 4 has 
been used which has the advantage of being able to compensate for the 
possible variation of the annular gap separating the sealing wall 3 from 
the inner surface of conduit 1. This is not obligatory and in a variant of 
construction illustrated in FIG. 6a, an assembly of O seals 4' has been 
used, held in position by a single collar 35 and able to be deformed under 
the effect of the pressure, so as to provide a satisfactory seal. In 
another variant of construction illustrated in FIG. 6b, an assembly of O 
seals 4" is compressed, before application of pressure, by means of a 
known packing system. 
These O seals 4' and 4" may be replaced by any other type of seal, for 
example by braided packing. 
The system of the invention may obviously be used for testing pressure or 
overpressure resistance behavior of any type of apparatus with opening 
pipe, coming straight from the braziery or machined, using any fluid, 
liquid or gaseous.