Note: Descriptions are shown in the official language in which they were submitted.
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Device for sealing a lance in an opening for introduction of the
lance into a container under pressure
This invention relates to a device for sealing a lance in an opening for
introduction of the lance into a container under pressure, in particular a shaftfurnace.
To enable measurement of the gas concentrations in a shaft furnace it is
5 already known how to introduce a lance with a measuring probe through a
lateral hole into the shaft furnace. As an overpressure prevails inside the
furnace, this hole must be sealed against the lance to prevent outflow of the
gases in part injurious to health.
Sealing devices, which enable introduction and withdrawal of the lance and at
10 the same time prevent outflow of the gases from the shaft furnace, are provided
for this purpose.
Plastically deformable packings, which are arranged in a tight casing and rest
tightly against the lance to be introduced with the result that a seal against the
casing is achieved, are the simplest form of sealing device. However, the cross-
15 section of the lance is subject to relatively marked fluctuations. These changesin the lance cross-section may result on the one hand from deposits or wear,
with the result that the cross-section is increased or reduced, while on the other
hand operating temperature fluctuations and the associated thermal expansion
or contraction cause changes in the lance cross-section. However, the effect of
20 these changes is that the plastic packings no longer rest tightly against thelance relatively quickly with the result that the sealing property is lost.
DE-A-29 50 672 discloses a sealing device having an elastic tubular seal, which
can be pressed down, joined to the seal and resting on the lance. This elastic
seal is subjected to pressure when the lance is introduced with the result that it
25 fits even more tightly around the lance and thus increases the tightness. As the
tubular seal rests continuously against the lance the stressing of the material by
friction when the lance is introduced and withdrawn is considerable, which leads
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to rapid wear and destruction of the tubular seal and the associated loss of
sealing function.
As the elasticity of the seal must be ensured, the wear cannot be prevented
even by reinforcing or coating the friction surface. In other words it is not
5 possible to increase the wall thickness at will, as is customary with plastic seals,
or coat the friction surface with a wear-resistant material, because this generally
does not have a high elasticity.
To avoid this disadvantage of the attached elastic seal the patent specificationDE-A-44 15 219 and DE-A-44 1~ 221 disclose a sealing device, which
10 comprises an elastic inflatable seal, which is pressurised so that it fits tightly
against the lance when the latter has already been introduced, but is retracted
so far during insertion and withdrawal of the lance that it no longer rests against
the latter. To ensure the tightness during introduction or withdrawal of the lance,
however, several annular seals, e.g. flexible seals or packings, which rest
continuously against the lance, are provided. Whereas the disadvantage of
rapid wear of the elastic material s eliminated in this sealing device, a new
problem arises. As the inflatable, elastic seal no longer rests against the lance
when the latter is moved, it is no longer possible to compensate in this phase
for radial play caused by the changes in the lance cross-section.
Furthermore, various sealing devices, which can be used to seal shafts or
journals in a casing, have been described. FR-A-1.600.190 describes, for
example, a sealing device for a journal with inflatable seal, which rests tightly
against the journal when pressurised. The inflatable seal is arranged in a ring in
a radial chamber in a casing, the ring being movable radially in the latter in such
a way that radial displacements between the journal and the casing can be
compensated. However, this device again has the disadvantage of the rapidly
wearing tubular seal already described above.
DE-A-14 25 523 discloses a sealing device for rotating shafts, in which two
flexible packings are arranged around the shaft inside a casing, the packings
being held in their axial position by an open cage construction under spring
tension or by a shell made from an easily deformable material. The flexible
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packings are forced in a radial direction against the sealing face of the shaft by
admission of a pressure medium to the casing and the contact pressure on the
shaft is increased. US-A-2,273,129 describes a seal for an anti-friction bearing,
in which two sealing rings with a U-shaped cross-section rest against the shaft
5 in a casing coaxial with a shaft, the legs of the U section each forming a sealing
lip. The seals are axially spaced in such a way that the recesses in the
U-shaped cross-sections are axially opposite each other, so that the recesses
terminate in a pressure space formed between the seals. Admission of a
pressure medium to the pressure space forces the two sealing lips of each seal
10 radially apart, so that the sealing lip resting on the shaft fits more closely to the
latter. US-A-3,434,728 describes a device for sealing a shaft bushing into a
pressure space with a casing integrated with the latter, the casing extending
coaxially with the shaft outside the pressure space. Packings, which are each
pressed by a sleeve-type piston against the corresponding end face of the
15 casing, are arranged around the shaft at each end face of the casing inside the
latter. However, these devices are not suitable to compensate for radial
displacements between a lance and the axis of a bushing.
Consequently the present invention is based on the task of providing a device
for sealing a lance on entry into a container under pressure, which can
20 compensate both for radial play as a result of changes in the lance cross-
section and also displacements of the lance axis with regard to the bushing axiswithout jeopardising the tightness of the device due to excessively rapid wear.
According to the invention this problem is solved by a device for sealing a lance
in an opening for leading the lance into a container under pressure, in particular
25 a shaft furnace, which comprises an outer casing with an end wall on the shaft
furnace side and on the environment side, which are provided axially with an
opening for a lance, and a sealing element arranged in the outer casing, and
which is characterised by the fact that the sealing element comprises an inner
casing with axial end walls provided with an opening for the lance as well as at30 least one packing and at least one axially movable annular piston, which are
arranged inside the inner casing coaxially with an axis of the inner casing, that
the packing is arranged between the piston and one of the end walls of the
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inner casing in the actuating direction of the piston, that the packing can be
compressed axially against one of the end walls of the inner casing by actuationof the piston whereby the packing extends radially and forms a seal around a
lance which is being led through, and that the inner casing is radially movable in
5 the outer casing, so that the inner casing together with the packing and the
piston is self-centering on a lance led into a container.
The negative effects of the wear on the seal arrangement can be significantly
reduced by using a packing, i.e. a plastic seal, as sealing element. In reality the
problem of maintaining their elasticity is not encountered with plastic seals.
10 Hence with this packing the material thickness can be increased and the friction
surface coated with a wear-resistant material without any adverse effect on the
sealing properties.
It should be noted that the term packing is used as a generic term here. It is
obvious to the expert that a packing as used in the present invention may also
15 consist or several packing rings arranged axially next to each other. In this case
the individual packing rings are pressed against each other on actuation of the
piston, a first packing ring being supported by one of the end walls, whereas a
second packing ring rests directly against the piston and transfers the piston
pressure to the interposed packing rings.
20 As the packing can be compressed by a piston, a feature of the device
according to the invention is that the seal can be adapted to variations in the
lance cross-section. In addition the actuation of the piston can be discontinuedfor movement of the lance in the device. Consequently the tight fit of the
packing around the lance is loosened and the latter can be moved with less
25 frictional resistance.
Furthermore, according to the internal pressure in the container, the tightness of
the entire device can be adapted to the conditions in the container by stronger
or weaker actuation of the piston. In other words the required greater tightnessof the sealing devices, e.g. in the case of a pressure increase in the container,
30 can be achieved by stronger actuation of the piston.
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The possibility of radial displacement of the inner casing in the second casing
enables it to adapt to an inclined or axially displaced position of the lance in the
sealing device. Hence the inner casing can be freely centered on the lance, if
the latter is introduced at an angle or with axial displacement into the sealing5 device.
In a preferred embodiment the sealing element comprises two pistons and two
packings, which are arranged coaxially with the axis of the device, the two
pistons being arranged axially between the two packings, so that they act in
opposite directions when actuated and each of the packings can be
10 compressed by a piston against one of the end walls of the inner casing.
The stress on the individual packing can be reduced by the use of several
packings. In addition an adequate sealing effect of the device is achieved with a
weaker actuation of the pistons.
To facilitate the introduction and withdrawal of the lance and to reduce the wear
15 on the seals it is advantageous to install an elastic element within the at least
one packing, concentrically with the axis of the device, which is enclosed by the
packing and at least partially reverses the axial deformation of the packing
when the piston is not actuated.
On reduction of the piston pressure on the packing the elastic element
20 endeavours to reassume its original shape. If the piston is no longer actuated,
the potential energy stored in the elastic element during compression of the
packing by the pistons is released and the packing is extended axially. This is
associated with a radial contraction with the result that the close fit of the
packing around the lance is loosened.
25 To ensure the tightness of the entire device the inner casing is advantageously
sealed against the end walls of the outer casing with annular flexible seals
which are attached to the end walls of the inner casing.
An embodiment in which two pistons are arranged in such a way that an
annular pressure chamber is formed between the two pistons, is particularly
30 advantageous. If each of the pistons is sealed with an inner annular seal radially
inwards against a guide sleeve, which is mounted coaxially with the axis, and
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with an outer annular seal radially outwards against the inner surface of the
inner casing, the annular pressure chamber is sealed axially and the two
pistons can be actuated simultaneously by admission of a pressure medium to
the pressure chamber.
5 This saves separate feed lines for the pressure medium to the two pistons as
well as expensive control of the pressurisation.
., In a further embodiment an elastic seal, which seals the pressure chamber ' outwards, is arranged in the pressure chamber.
In this embodiment the annular seals, with which each of the pistons is sealed
10 radially inwards against the guide sleeve and radially outwards against the inner
surface of the first casing, can be dispensed with.
To ensure a certain continuous pre-tension of the packings and thus a certain
tightness, elastic means, which can actuate the pistons, can optionally be
arranged between the pistons in the pressure chamber. These elastic means
15 may comprise, for example, a spiral spring. This spring presses the pistons
against the packings with a certain force even if the pressure chamber is not
under pressure. It should be noted that the spring force of the spring should besmaller than the spring force of the elastic means in the packings, because
otherwise the deformation of the packing cannot be reversed (even partially).
20 In a further variant of the embodiment radially movable, wedge-shaped
elements, which can actuate the pistons, are arranged between the pistons.
These wedge-shaped elements can then be moved radially inwards, e.g. by
admission of a pressure medium to a chamber between the first and second
caslng.
25 Elastic means, e.g. a pretensioned spiral spring ring or a pretensioned ring
made from elastic plastic, which exerts a force directed radially inwards on thewedge-shaped elements, can also optionally be arranged around the latter.
Elastic means, which rest radially inwards on the guide sleeve and press
radially outwards against the wedge-shaped elements, can be arranged
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between the guide sleeve and wedge-shaped elements as restoring element for
the latter.
It is advantageous for all embodiment variants to coat the supporting surfaces,
with which the inner casing rests on the lance, with a material, which reduces
5 the frictional resistance of the supporting surfaces on the lance.
Consequently the wear on these parts is, of course, reduced, thereby
substantially prolonging the life of the sealing device.
Various embodiments of the device according to the invention are described
below with reference to the figures.
10 Fig. 1 shows a section through the axis of a first embodiment of a device for sealing a lance,
Fig. 2 the central part of the device according to Fig. 1 in an enlarged section,
Fig. 3 - Fig. 7 sections through the central parts of different sealing devices,
Fig. 8 a cross-section along the iine A-A' at right angles to the axis through the
1 5 sealing device in Fig . 1 .
Fig. 1 shows a section through an embodiment of a sealing device. It comprises
an outer casing 2, which is divided in its interior into several chambers 4-8,
which are separated by ribs 10 in the axial direction and in which the individual
sealing elements are arranged. The casing 2 and ribs 10 are provided with an
20 opening for a lance 12 axially in the centre, the width of the opening being
dimensioned in such a way that the lance 12 has a relatively large radial play in
the opening.
The device in Fig. 1 comprises a further two sealing elements 16, 18 in
chambers 4 and 8, in addition to a central sealing element 14, which is mounted
25 in the central chamber 6. These may be of the type described in DE-A-
44 15 219 and DE-A-44 15 221. They comprise rings 20, 22, the inside cross-
section of which is adapted to the cross-section of the lance 12. Each of these
rings 20 or 22 is mounted in such a way in its chamber 4 or 8 that it can be
moved at right angles to the central axis 24 of the sealing device. This
30 possibility of moving the rings 20, 22 in their respective chamber 4, 8 of the
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casing 2 enables the rings 20, 22 to be adapted to an inclined or axially
displaced position of the lance 12 in the sealing device. Hence the rings with the
sealing elements can centre freely on the lance 12, if the lance is introduced
through the sealing device at an angle or axially displaced.
5 The rings 20, 22 constitute holders for packings or seals, which rest on the
lance 12. For example, the ring 20 is provided on the inside with a packing
consisting of two packing rings 26, via which it rests on the lance 12. The ring22 has an inflatable seal 30, which is accommodated in a hollow space 32 in
ring 22. In the uninflated position this inflatable seal 30 is retracted into its
10 hollow space 32; this enables the lance 12 to move without damage or wear to
the inflatable seal 30. In the inflated position, the inflatable seal 30 can,
however, compensate for substantially larger radial play than the two packing
rings 26 of the sealing element 16. The ring 22 advantageously lies on the lance12 via two packings 28, which are arranged on both sides of the hollow space
15 32. To apply pressure to the inflatable seal 30 pressure is advantageously fed
to the chamber 8. This is done. e.g. by supplying a pressure medium to the
chamber via a supply opening 34. The chamber 8 is connected via openings 36
in the ring 22 to the hollow space 30, with the result that the pressure medium
enters the inflatable seal 30. Finally, it should be noted that the inflatable seal
20 30 can be inflated by a liquid under pressure or a gas under pressure.
Viewed in the direction of introduction of the lance 12 an inlet opening 38 for
lubricant is provided in the rib 10 of casing 2 behind the chamber 8.
Consequently lubricant enters the annular hollow space 40, which is limited
axially on the environment side by the ring 22 and on the shaft furnace side by
25 the central sealing element 14 and is enclosed radially on the inside by the
lance 12 and on the outside by the rib 10. The lubricant serves both to lubricate
the packings with the result that their wear is reduced during movement of the
lance and also to coat the lance with an anti-corrosion film.
An inlet opening 42 for sealing gas is provided in front of the sealing element 16
30 in the direction of introduction. Sealing air at high pressure can be blown into
the hollow space 44 through this opening 42. If the pressure in the hollow space
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44 is greater than the pressure in the shaft furnace gases harmful to health
such as carbon monoxide are prevented from escaping from the shaft furnace
in the event of a leak in the sealing element 16.
The central sealing element 14 is shown in enlarged form in Fig. 2. It comprises5 an inner casing 46 with an end wall on the shaft furnace side and on the
environment side, which are provided with an opening for a lance 12. This inner
casing is mounted in the central chamber 6 of the outer casing 2 in such a way
that it can be moved at right angle to the central axis 24 of the sealing device.
This possibility of displacement of the inner casing 46 in the chamber 6 of
10 casing 2 enables free centering of the inner casing 46 on the lance 12, as in the
case of rings 20, 22, if the lance is introduced at an angle or with axial
displacement through the sealing device.
At its two end walls the inner casing 46 is sealed axially against the ribs 10 of
the outer casing 2 with annular seals 48, which are seated in a groove cut into
15 the front sides coaxially with the axis 24. Inside ihe casing 46 a packing 50cG"sisting of two packing rings is arranged coaxially with the axis 24 both on the
shaft furnace side and on the environment side. These packings 50 preferably
rest against the respective end wall of the inner casing 46. They are
dimensioned in such a way that they rest on the lance 12, if the latter is pushed
20 into the sealing device. To increase the tightness still further when the lance 12
is introduced, two annular pistons 52 are provided in the casing 46. These
annular pistons 52 are guided radially outwards on the inner wall of the inner
casing 46, whereas they are guided inwards by a guide sleeve 54, which is
arranged coaxially with the axis 24 and its inside width is dimensioned in such a
25 way that the lance has a certain radial play in the sleeve 54. The annular
pistons are each sealed by two annular seals 56, e.g. O-rings or quad rings,
radially against the inner casing 46 and the guide sleeve 54 with the result that
a sealed pressure chamber 58 is formed between the pistons in an axial
direction.
30 To actuate the pistons 52 simultaneously, the pressure chamber 58 is
pressurised. This is preferably done by supplying a pressure medium via a
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supply opening 60 to the chamber 6 sealed by the annular seals 48. The
chamber 6 is connected to the pressure chamber 58 via openings 62 in the
casing 46 with the result that the pressure medium enters the pressure chamber
58. It should be noted that the admission of pressure to the pressure chamber
5 58 can be carried out by a liquid or gas under pressure.
The annular pistons 52 are axially movable, so that on actuation one of the
piston is forced against the packing resting on the end-wall on the shaft-furnace
side whereas the other piston is forced against the packing resting on the end
wall on the environment side. The resulting axial pressure exerted forces the
10 packings 50 against the respective end wall of the inner casing 46 and
compresses them axially, whereby they extend radially. This causes the
packings to fit more tightly against the lance 12 with the result that the tightness
of the entire device is increased.
To withdraw the lance 12 from the device, the overpressure in the chamber 6
15 and the- pressure chamber 58 is first reduced. Consequently the prsssure
exerted by tt,e pistons 52 on the packings 50 is discontinued and the packings
50 can extend axially again with the result that the radial extension is partially
reversed. To ensure that the packings 50 resume their original shape, each
packing is provided with an elastic element 64 in its interior, which is mounted20 concentrically with the axis 24 of the device and is enclosed by the packing on
its entire circumference. This elastic element 64, e.g. a rubber core, causes atleast partial reversal of the axial deformation of the packing when the piston is
not actuated. The packing 50 thus rests less tightly against the lance 12 with the
result that the frictional resistance and thus also the wear is considerably
25 reduced. The life of the packings 50 is thus in turn prolonged and they need not
be replaced as frequently.
To ensure a certain continuous pretension of the packings and thus a certain
tightness, an elastic means 66, e.g. a spiral spring, can be arranged optionallyin the pressure chamber 58 between the two pistons 52. This is shown in Fig. 3.
30 This spring 66 presses the pistons against the packings with a certain force
even if the pressure chamber 58 is not under pressure. It should be noted that
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the spring force of spring 66 should be smaller than the spring force of the
elastic means 46 in the packings 50, because otherwise the deformation of the
packings cannot be reversed (even partially).
Fig. 4 shows a further variant of the sealing element 14. In this embodiment no
5 annular seals 56 are used to seal the pressure chamber 58. Instead the entire
pressure chamber 58 is lined with an elastic seal 68, which is clamped with an
insert 70 in the inner casing 46. This seal 68 is likewise subjected to pressureas in the preceding exemplified embodiments. As the seal 68 is supported
against the guide sleeve 54 radially towards the axis 24, it extends in an axial10 direction with the result that the two pistons 52 are again actuated
simultaneously.
Fig. 5 shows a further possible embodiment of the sealing element 14. In this
variant the two pistons 52 are actuated only by an elastic means 72. This
advantageously comprises a spiral spring and is pretensioned in such a way
15 that the spring force exerted is adequate to compress the packings 50 axiallyvia ~he pistons 52. The sealing element thus automatically adapts to variations
in the lance cross-section.
A further externally controllable variant is shown in Fig. 6. The two pistons 52are actuated by wedge-shaped elements 74, which are mounted between the
20 two pistons 52 in such a way that they force the two pistons 52 axially apart by
radial displacement towards the axis. The actuating elements 74 have a part 76
facing radially outwards with lateral faces parallel with each other. The elements
74 are guided by these lateral faces in a guide opening 78 in the inner casing
46 and sealed against them by flexible seals 80.
25 The wedge-shaped elements 74 are actuated by admission of pressure to
chamber 6 via the inlet opening 60. The overpressure building up in the
chamber acts on the outer lateral face of the wedge-shaped elements 74 and
exerts on them a force directed radially inwards. When the overpressure is
discharged from the chamber 6 the elements 74 are again pushed radially
30 outwards by elastic means 82. These elastic means 82 advantageously
comprise a spiral spring, which is supported radially inwards on the guide
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sleeve 54, and presses radially outwards against the inner surface of the
actuating element 74. To prevent the actuating elements 74 being pushed
radially outwards from the guide openings 78 by the spring 82 when the
chamber 6 is pressureless, stops 84 are provided on the outside of the guide
5 openings 78.
A further variant, which adapts automatically to changes in cross-section, is
based on the embodiment in Fig. 6. This is shown in Fig. 7. In this case the
wedge-shaped elements 74 are no longer actuated by admission of pressure to
chamber 6, but by an elastic element 86, which is laid around the outside of the10 wedge-shaped actuating elements 74. This elastic element 86 may for example,
be a spiral spring ring or a ring made from an elastic plastic, which is fitted
pretensioned in an annular groove 88, which is cut coaxially with the axis into
the parts 76 of the actuating elements 74 radially inwards from the outer lateral
face. It should be noted that in this variant the flexible seals 80 are unnecessary
15 just like the inlet opening 60.
Fig. 8 shows a cross-section along the line A-A' in Fig. 1 at right angles to the
axis through a sealing device when the lance 12 is inserted. It can be seen thatthe lance 12 and thus the opening in this case do not have a circular cross-
section, but a non-circular cross-section. However, this is only one possible
20 embodiment; the lance cross-section may, of course, also be circular.
The lance 12, which is introduced into the opening 90 in the inner casing 46 in
such a way that a certain play exists between the lance 12 and the inner casing
46, can be seen in the centre of the arrangement. The chamber 6 which is
limited inwards by the inner casing 46 and outwards by the outer casing 2, can
25 also be seen in the outer area of the arrangement in Fig. 8.
The inner face of the opening 90 is coated in its upper area with a material 92,which has particularly good sliding properties. This material 92, with which theupper partial areas of the inner faces of the rings 20, 22 are also coated,
reduces the friction of rings 20, 22 or the sealing element 14 on the lance and
30 thus prevents rapid wear of the areas, which during centering of the rings 20, 22
or sealing element 14 on the lance 12 rest and slide to and fro on the latter.
