Receptacles – Closures – Having means for securing or retaining closure in its closed...
Reexamination Certificate
1999-04-22
2001-05-01
Hughes, S. Thomas (Department: 3726)
Receptacles
Closures
Having means for securing or retaining closure in its closed...
C220S263000, C292S138000, C081S057000, C081S037000
Reexamination Certificate
active
06223925
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to pressure vessels, and more particularly, relates to a stud tensioning device for securing a cover to a flange of such a vessel.
BACKGROUND OF THE INVENTION
Many industrial processes, such as coking processes or chemical treatment processes, employ large pressure vessels, often disposed vertically with top and bottom closure mechanisms. The bottom closure usually includes a cover that is generally quite massive and secured to the vessel by dozens of bolts. In order to remove the bottom cover from the vessel (a process sometimes referred to as “unheading” the vessel), the bottom cover is generally first supported by a hydraulic lifting mechanism, then disengaged from the vessel, at which point it can be lowered by the hydraulic mechanism. The operation is reversed to resecure the cover in place. The disengagement and reengagement of the bottom closure can be quite labor intensive, given the mass of the bottom cover and the numerous bolts that hold it in place.
Examples of removable closures are shown in U.S. Pat. Nos. 4,820,384 and 5,290,072, each to Pechacek, and U.S. Pat. No. 5,221,019, to Pechacek et al. For example, the Pechacek '384 patent discloses a remotely operable vessel cover assembly including a cover
10
, which can be attached to a flange
5
surrounding an opening in the vessel. When the cover
10
is raised into position, a series of connector pins
60
fits through corresponding holes
20
f
in a force ring
20
and keyhole-shaped holes
30
a
in a lock ring
30
, which is rotated so that heads
60
e
of the connector pins
60
are locked behind the lock ring
30
. Fluid pressure is then applied to a force actuator
40
, pressurizing inner and outer annular rings
40
a
,
40
b
, which expand to pre-stress the pins
60
and the cover
10
. A ramp ring
50
is then rotated until a series of ramps
50
a
firmly contacts a complementary series of ramps
10
b
on the cover
10
. The force actuator
40
is then depressurized. According to the Pechacek '384 patent, the angle of inclination of the ramps
50
a
is sufficiently shallow that friction between the ramp ring
50
and the cover
10
prevents slippage.
The Pechacek '384 patent shows a mechanism for facilitating engagement and removal of the cover
10
. Rather than individually tightening and loosening a large number of bolts, connector pins
60
are selectively locked behind a locking ring
30
. However, the mechanism disclosed in the '384 patent is complex. For example, in order to secure the cover
10
, the mechanism requires first setting the lock ring
30
in position behind unstressed pins
60
, then stressing the pins
60
by means of a complex pressure ring assembly, and then utilizing a separate ramp ring
50
to support the pins
60
once they are stressed. Further, as can be seen in
FIG. 1
thereof, when the cover
10
is brought into or out of engagement with the vessel, the pins
60
are exposed so as to be susceptible to damage due to contact with the cover
10
.
Another example, U.S. Pat. No. 5,228,825, to Fruchtbaum et al., discloses a pressure vessel closure device in which a vessel V is equipped with a head assembly A, which includes a lower flange F at an opening into the vessel V. A generally circular bottom head H (blind flange) is secured against the flange F for sealing the vessel V with a suitable gasket. In normal use, the vessel V is sealed by a plurality of springs
14
and hooks
12
. The hooks
12
anchor a movable retaining element
10
to the bottom head H. The springs
14
bias the retaining element
10
away from the flange F to tension the hooks
12
to seal the bottom head H against the flange F.
In the '825 patent, a plurality of cylinders
30
is disposed to draw the movable retaining element
10
downwardly toward the flange F. Before the bottom head H is attached, the hooks
12
are spread, as shown in
FIG. 7
of that patent. The cylinders
30
are pressurized to compress the springs
14
, the bottom head H is raised to engage the flange F, and the hooks
12
are then pivoted inwardly below forks
36
. The cylinders
30
are depressurized, and the springs
14
then bias the retaining element
10
upwardly from the flange F, and the hooks
12
, in turn, engage the forks
36
and securely hold the bottom head H in place against the flange F.
Rather than using traditional bolts or pins, the device of the '825 patent utilizes hooks and forks in combination with an axially movable retaining element. The described device also requires that each of the hooks be pivoted in order to engage them behind or disengage them from the forks.
Similarly, U.S. Pat. No. 2,734,824, to DeLuca, shows an autoclave or pressure vessel that includes a vertically disposed tank
10
having a bottom cover. A plurality of bolts
46
is spaced about the tank
10
and arranged to engage a cover
13
when the cover
13
is closed. Each bolt
46
is threadably secured at its upper end to a bifurcated member
47
and has a shoulder
48
which rests tightly against the lower surface of the member
47
. Corresponding to each bolt is a radial slot
61
′ in the edge of the cover and a slot
61
in a flange
65
of the tank
10
. The lower end of each bolt
46
is provided with a nut
59
and washer
60
to engage the underside of the cover
13
. Cylinders
49
function to move their respective bolts downwardly, and a series of cams
56
cooperates to swing the bolts outwardly to disengage the bolts from the cover and flange to permit opening of the cover
13
.
The bolts
46
in the '824 patent, while providing the basic means for holding the cover
13
in position, would not, according to that patent, prevent accidental opening of the cover
13
should the hydraulic pressure on cylinders
49
fail. In order to avoid such an occurrence, a locking ring
64
is provided on top of the flange
65
. The upper shoulder
48
of each bolt
46
is spaced slightly above the top surface of the locking ring
64
when the cover
13
is locked closed. The ring
64
has a plurality of rectangularly shaped cut-out portions
66
, and one edge of each of these cut-out portions
66
is provided with a narrow slot
67
. The ring
64
can be rotated to a locked position in which the slot
67
engages the body of the bolt
46
and is aligned with its upper collar
48
, as shown in
FIGS. 4 and 5
of the '824 patent. On the other hand, each member
47
may be aligned with its associated cut-out portion
66
when the cover
13
is to be opened.
The apparatus shown in the '824 patent utilizes a relatively complex mechanism that requires the bolts
46
to be pivoted to be seated and unseated. Further, the same hydraulics that actuate the pivoting must also bear the downward force on the bolts when the tank is sealed. Thus, the locking ring must be employed separately to guard against accidental opening in the event of hydraulic failure.
Thus, there is a need in the art for a mechanism that selectively and reliably secures a cover to a flange of a pressure vessel, which can be simply and efficiently engaged and disengaged. There is a further need for such a mechanism that is conducive to remote actuation. There is a still further need for such a mechanism that does not rely on hydraulic pressure to maintain the engagement. There is an additional need in the art for a mechanism that utilizes bolts or studs to selectively secure a cover to a flange of a pressure vessel, wherein the bolts or studs can be retracted when the cover is disengaged from the flange.
SUMMARY OF THE INVENTION
Our invention addresses the foregoing needs in the art by providing a stud tensioning device that selectively secures a cover to a flange of a pressure vessel. A plurality of such devices can be employed, using a plurality of studs that extend through matching openings in the flange and cover. A movable anchor plate or plates, also with holes through which each stud extends, is disposed adjacent to the flange or cover. The head of each stud will fit through its a
Kalinosky Joseph
Klick Richard
Malsbury Allen S.
Myszka Ronald T.
Fitzpatrick ,Cella, Harper & Scinto
Foster Wheeler Corporation
Hong John C.
Hughes S. Thomas
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