Title: Steam line closing valve and steam turbine plant comprising such a steam line closing valve
Abstract: The invention relates to a steam line closing valve for closing a steam line, especially in a steam turbine plant between a first partial turbine and at least one second partial turbine that is operated at a lower pressure than the first partial turbine. According to the invention, the steam line closing valve is subdivided into a plurality of elements that cooperate to cover the cross-section of the steam line, thereby reducing the moment of inertia Iy of the elements.
Patent Number: 6,929,447 Issued on 08/16/2005 to Haje
| Inventors:
|
Haje; Detlef (Bottrop, DE)
|
| Assignee:
|
Siemens Aktiengesellschaft (Munich, DE)
|
| Appl. No.:
|
650885 |
| Filed:
|
August 28, 2003 |
Foreign Application Priority Data
| Mar 08, 2001[DE] | 101 11 187 |
| Current U.S. Class: |
415/151 |
| Intern'l Class: |
F01D 025/00 |
| Field of Search: |
415/151
60/653,679
137/301.08,301.09,301.11
|
References Cited [Referenced By]
U.S. Patent Documents
| 1766527 | Jun., 1930 | Meyer.
| |
| 2837991 | Jun., 1958 | De Roo.
| |
| 3444894 | May., 1969 | Norelius.
| |
| 3532321 | Oct., 1970 | Bowman et al.
| |
| 3677297 | Jul., 1972 | Walton.
| |
| 4077432 | Mar., 1978 | Herr.
| |
| 4187878 | Feb., 1980 | Hughey.
| |
| 4448026 | May., 1984 | Binstock et al.
| |
| 4455836 | Jun., 1984 | Binstock et al.
| |
| 4693086 | Sep., 1987 | Hoizumi et al.
| |
| 5765592 | Jun., 1998 | Karlicek.
| |
| 6045332 | Apr., 2000 | Lee et al.
| |
| 6131882 | Oct., 2000 | Suzuki.
| |
| 6293306 | Sep., 2001 | Brenes.
| |
| Foreign Patent Documents |
| 36 07 736 | Sep., 1987 | DE.
| |
| 0 049 302 | Apr., 1982 | EP.
| |
| 0 383 185 | Aug., 1990 | EP.
| |
| 0 780 608 | Jun., 1997 | EP.
| |
| 2 589 517 | May., 1987 | FR.
| |
| 58074804 | Jun., 1983 | JP.
| |
| 59134303 | Aug., 1984 | JP.
| |
| 60261906 | Dec., 1985 | JP.
| |
| WO 01/0452/2 | Jan., 2001 | WO.
| |
Primary Examiner: Nguyen; Ninh H.
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is the US National Stage of International Application No. PCT/DE02/00684,
filed Feb. 25, 2002 and claims the benefit thereof. The International Application
claims the benefit of German application No. 10111187.8, filed Mar. 8, 2001, both
of which are incorporated by reference herein in their entirety.
Claims
1. A steam line isolation valve for closing a steam line, particularly in a steam
turbine system between a first expansion stage and least one second expansion stage
which is operated at lower pressure than the first expansion stage, characterized
by a plurality of elements jointly covering the cross-section of the steam line,
at least one of the elements is provided with one or more permanent recesses which
do not extend over the entire thickness d of the elements.
2. The steam line isolation valve according to claim 1, wherein the recesses-become
deeper towards the edge of the element.
3. The steam line isolation valve according to claim 2, wherein the elements
are matched to the cross-section of the steam line, or the cross-section of the
steam line is matched to the elements, or both the cross-section of the steam line
and the elements are varied.
4. The steam line isolation valve according to claim 2, wherein the elements
have the same width b.
5. The steam line isolation valve according to claim 2, wherein the elements
have different dimensions for matching to the cross-section of the steam line.
6. The steam line isolation valve according to claim 2, wherein the elements
have the same moment of inertia Iy about an axis of rotation y.
7. The steam line isolation valve according to claim 2, wherein the elements
of the steam line isolation valve can move independently of one another.
8. The steam line isolation valve according to claim 2, wherein a plurality of
elements of the steam line isolation valve are connected to a common drive via
a gear.
9. The steam line isolation valve according to claim 1, wherein the elements
are matched to the cross-section of the steam line, or the cross-section of the
steam line is matched to the elements or both the cross-section of the steam line
and the elements are varied.
10. The steam line isolation valve according to claim 9, wherein at least one
of the elements has a rounding.
11. The steam line isolation valve according to claim 10, wherein the elements
have the same width b.
12. The steam line isolation valve according to claim 10, wherein the elements
have different dimensions for matching to the cross-section of the steam line.
13. The steam line isolation valve according to claim 10, wherein the elements
have the same moment of inertia Iy about an axis of rotation y.
14. The steam line isolation valve according to claim 10, wherein the elements
of the steam line isolation valve can move independently of one another.
15. The steam line isolation valve according to claim 10, wherein a plurality
of elements of the steam line isolation valve are connected to a common drive via
a gear.
16. The steam line isolation valve according to claim 9, wherein the elements
have the same width b.
17. The steam line isolation valve according to claim 9, wherein the elements
have different dimensions for matching to the cross-section of the steam line.
18. The steam line isolation valve according to claim 9, wherein the elements
have the same moment of inertia Iy about an axis of rotation y.
19. The steam line isolation valve according claim 9, wherein the elements of
the steam line isolation valve can move independently of one another.
20. The steam line isolation valve according to claim 9, wherein a plurality
of elements of the steam line isolation valve are connected to a common drive via
a gear.
21. The steam line isolation valve according to claim 1, wherein the elements
have the same width b.
22. The steam line isolation valve according to claim 21, wherein the elements
have the same moment of inertia Iy about an axis of rotation y.
23. The steam line isolation valve according to claim 21, wherein the elements
of the steam line isolation valve can move independently of one another.
24. The steam line isolation valve according to claim 21, wherein a plurality
of elements of the steam line isolation valve are connected to a common drive via
a gear.
25. The steam line isolation valve according to claim 1, wherein the elements
have different dimensions for matching to the cross-section of the steam line.
26. The steam line isolation valve according to claim 25, wherein the elements
have the same moment of inertia Iy about an axis of rotation y.
27. The steam line isolation valve according to claim 25, wherein the elements
of the steam line isolation valve can move independently of one another.
28. The steam line isolation valve according to claim 25, wherein a plurality
of elements of the steam line isolation valve are connected to a common drive via
a gear.
29. The steam line isolation valve according to claim 1, wherein the elements
have the same moment of inertia Iy about an axis of rotation y.
30. The steam line isolation valve according to claim 29, wherein the elements
of the steam line isolation valve can move independently of one another.
31. The steam line isolation valve according to claim 29, wherein a plurality
of elements of the steam line isolation valve are connected to a common drive via
a gear.
32. The steam line isolation valve according to claim 1, wherein the elements
of the steam line isolation valve move independently of one another.
33. The steam line isolation valve according to claim 1, wherein a plurality
of elements of the steam line isolation valve are connected to a common drive via
a gear.
34. The steam line isolation valve according to claim 1, wherein the elements
have the same width b.
35. A steam turbine system with at least one first expansion stage and at least
one second expansion stage which is operated at lower pressure than the first expansion
stage, of which there is at least one, and having at least one steam line for feeding
the second expansion stage, characterized in that there is disposed in each of
the steam lines, upstream of supply lines to the second expansion stage, a steam
line isolation valve of claim 1.
36. A steam line isolation valve for closing a steam line, particularly in a
steam turbine system between a first expansion stage and at least one second expansion
stage which is operated at lower pressure than the first expansion stage, comprising:
a plurality of elements jointly covering the cross-section of the steam line;
and
a permanent recess provided in at least one element, the recesses does not extend
over the entire thickness d of the element and become deeper towards the edge of
the element.
Description
FIELD OF INVENTION
The present invention relates to a steam line isolation valve for shutting a
steam line, specifically in a steam turbine system between a first expansions stage
and at least one second expansion stage which is operated at lower pressure than
the first expansion stage.
Expansion stage is taken to mean both separate turbine cylinders, each
having its own casing, and stages of a turbine cylinder disposed in-line in a common
casing, each having its own steam supply.
BACKGROUND OF INVENTION
Steam line isolation valves of this kind, also known as reheat stop valves,
are a safety device. They are provided before the entry of the steam into-the low-pressure
turbines downstream of the first turbine cylinder in saturated steam turbo sets
if the overspeed occurring in the event of load shedding of the system cannot be
limited to permissible values in any other way. In the event of load shedding as
the result of a three-phase line fault, for example, the load torque of a generator
driven by the turbo set quickly disappears. In this case the main steam valves
are closed so as to prevent further steam from being supplied to the first turbine
cylinder. However, the steam still stored in this turbine cylinder, the intervening
steam lines and any moisture separator or reheater continues to expand. Because
of the absence of load torque, the expansion causes the speed of the turbo set
to increase. It is therefore necessary to prevent this expansion and to prevent
steam from entering the second and any other turbine cylinders. A completely leak-tight
isolation is not necessary. Small leaks can be tolerated.
U.S. Pat. No. 3,444,894 discloses a device for controlling the pressure or the
quantity of a gaseous medium. The device has a housing which defines a longitudinally
extending channel and has an inlet port and an outlet port for the medium. Two
so-called damping paddles are disposed in the housing and can be moved against
one another vertically with respect to the longitudinal axis. In addition, a central
element is disposed essentially centrally in the channel between the damping paddles.
The central element is streamlined for favorable flow and extends along the longitudinal
axis in the channel. At its upstream end it has a round profile of appreciable
thickness, whereas it runs to a point at its downstream end.
DE 36 07 736 C2 describes a shutoff valve for pipework and the like whose housing
contains a swivel-mounted valve which in its closed position bears on the inside
of a seal lining disposed continuously over the entire housing width and made of
a rigid or only slightly flexible plastic such as a fluoroplastic. In the sealing
area, in which it has a slightly smaller clear diameter compared to the valve in
the open position, the seal lining is compliantly disposed toward the closed position
of the valve via a spring bridge and a gap between spring bridge and housing, the
spring bridge, which has slots, being permanently fixed in the seal lining by partial
or complete encasing, and the seal lining forming a unit with the spring bridge.
DE 38 26 592 A1 discloses an arrangement for actuating a stop valve in a steam
line, preferably a steam line of a steam turbine. On a rotating shaft of the stop
valve there is disposed a pinion with which two pairs of racks are engaged. One
pair of racks is used in conjunction with hydraulic means for opening the stop
valve, the other pair in conjunction with closing springs for rapid closing. By
ensuring zero backlash, the two separate systems for opening and closing reduce
mechanical wear and, via appropriate hydraulic circuitry, allow damping of the
disk of the stop valve when it assumes the closed position. In order to maintain
this damping irrespective of different operating states, manometric balances are
used in conjunction with an interceptor throttle which can be adjusted as a function
of the rotation angle. To relieve the pressure on the stop valve at opening, a
bypass line is used which can in turn be shut off by fast-closing shutoff valves.
In the case of the known steam line isolation valves, a single valve is provided
which is rotated to close the steam line. The pressure in the steam line is generally
between 10-15 (18) bar for a diameter of 1.2 to 1.4 m. The closing time of the
steam line isolation valve must be between one and two seconds. Because of the
high stress due to the pressure, the steam line diameter and the temperatures obtaining,
the valves must be of comparatively sturdy design. They are therefore very large
and very heavy, resulting in a high moment of inertia about the rotational axis
provided. To achieve the short closing time required, considerable acceleration
torque therefore has to be applied to the valve.
Increasing the diameter of the valves currently in use is very difficult
to achieve in terms of mechanical design. Drives capable of applying the required
acceleration torques must first be provided. Difficulties in implementing the valve
seating may also arise. Increasing the diameter would be desirable, however, as
the entire cross-sections of the steam lines between the individual turbine cylinders
can no longer be shut off at the current outputs of steam turbine systems. The
steam line isolation valves must therefore be disposed in the supply lines to the
individual second turbine cylinders. A separate steam line isolation valve is then
necessary for every second turbine cylinder. This results in a high mechanical
design complexity and financial outlay and an increased space requirement.
SUMMARY OF INVENTION
The object of the present invention is therefore to provide a steam line isolation
valve having a reduced moment of inertia with the same dimensions or having larger
dimensions with the same moment of inertia, thereby allowing a steam line with
larger cross-section to be shut.
This object is achieved according to the invention by a steam line isolation
valve of the type mentioned above, in that it is subdivided into a plurality of
elements which are jointly able to cover the cross-section of the steam line.
This sub-division enables smaller elements to be used. The moment of inertia
increases as the square of the distance from the axis of rotation. By means of
the proposed subdivision according to the invention into a plurality of elements,
this distance can be substantially reduced, resulting in an overall much smaller
moment of inertia. As each element's surface area exposed to steam pressure is
also reduced, lower bearing forces occur. The seatings of the individual elements
can therefore be implemented comparatively simply. For the same steam line cross-section,
the acceleration torque required is therefore significantly reduced. Alternatively
a larger cross-section can be closed for the same acceleration torque.
These relationships are formulated in the description of the figures.
Advantageous embodiments and developments of the inventions will emerge
from the dependent claims.
The elements advantageously cover the entire cross-section of the steam line.
This is taken to mean that maximally small gaps due to operation or manufacture
remain. In order to achieve complete sealing of the steam line, the elements are
matched to the cross-sectional shape of the steam line. Alternatively the cross-section
of the steam line can be matched to the shape of the elements in the region of
the steam line isolation valve. It is likewise possible to vary both the steam
line cross-section and the shape of the elements.
In an advantageous embodiment, when the steam line isolation valve opens, the
entire cross-section is not cleared at once within the short opening time. Instead
it is cleared gradually. This can be achieved by recesses in the form of grooves
or pockets in the elements which, when the steam line isolation valve opens, first
clear a small cross-section before the elements clear the cross-section as a whole.
This avoids abrupt loading of the second expansion stage. In addition, easier controllability
of the system as a whole is achieved when the steam line isolation valve is opened.
If the elements are matched to the cross-section of the steam line, at least
one
of the elements is advantageously rounded. Because of the high pressures and temperatures
obtaining, the steam line is generally circular in order to minimize and evenly
distribute the material stresses. The rounding of at least one of the elements
additionally achieves improved flow characteristics. The elements can have the
same width, resulting in simplified manufacturing. Alternatively the elements can
have different dimensions for matching to the cross-section of the steam line.
Specifically the width of the elements can be varied over their length.
The elements advantageously exhibit the same moment of inertia about an axis
of rotation. To close the steam line, the same acceleration torque is therefore
required for each of the elements. If the elements can move independently of one
another, the same drive can be used for each element, resulting in a reduction
in the parts count. If several elements are connected via a gear to a common drive,
the gear is evenly loading and a long service life can be achieved. In this case
the elements can be combined in groups. Alternatively it is possible to actuate
all the elements of the steam line isolation valve by means of a single drive.
The invention additionally relates to a steam turbine system with at least one
first expansion stage and at least one second expansion stage which is operated
at lower pressure than the first expansion stage, of which there is at least one,
and having at least one steam line for supplying the second expansion stages. In
this steam turbine system according to the invention, the steam line isolation
valve according to the invention is disposed in each of the steam lines upstream
of the supply lines to at least one second expansion stage.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference to exemplary
embodiments shown schematically in the accompanying drawings. The same reference
characters are used throughout to designate the same components having identical functions:
FIG. 1 shows a schematic representation of a steam turbine system;
FIG. 2 shows a schematic representation of a cross-section through a steam line
isolation valve according to the prior art;
FIG. 3 shows a schematic representation of an equivalent model of a steam line
isolation valve according to the invention in a first embodiment;
FIG. 4 shows a similar view to FIG. 2 in a second embodiment;
FIG. 5 shows a plan view of a steam line isolation valve according to the invention
in a third embodiment; and
FIGS. 6 to 11 show various schematic views of further embodiments of
a steam line isolation valve according to the invention, similar to FIG. 3.
DETAILED DESCRIPTION OF INVENTION
FIG. 1 schematically illustrates a steam turbine system
10. Saturated
steam generated by a device (not shown) is fed to a saturated steam turbine cylinder
11. On leaving this saturated steam turbine cylinder
11, the steam
is dewatered in a moisture separator
12 and then superheated in a reheating
device
13. It is then fed via a steam line
20 to two low-pressure
turbine cylinders
15 which are operated at lower pressure then the saturated
steam turbine cylinder
11. At the outlet of the low-pressure turbine cylinder
15 there is disposed a condenser
16 in which the steam is condensed
and fed back. The steam flows are schematically indicated by arrows. The saturated
steam turbine cylinder
11 and the low-pressure turbine cylinders
15
drive a common shaft
18 in the direction of the arrow
19. The shaft
18 in turn drives a generator
17 to produce electric power.
In the event of load shedding due, for example, to a three-phase line fault,
the
steam supply to the saturated steam turbine cylinder
11 via valves (not
shown) is interrupted. Steam stored in the saturated steam turbine cylinder
11,
the moisture separator
12 and the reheater
13 can expand still further
and enter the low-pressure turbine cylinders
15. In order to prevent this,
there is provided a steam line isolation valve
14 which is disposed directly
in the steam line
20 supplying the two low-pressure turbine cylinders
15.
In the exemplary embodiment shown, no shutoff valves and fittings are required
in branches
20a,
20b for the individual low-pressure
turbine cylinders
15.
FIG. 2 shows a cross-section through a steam line isolation valve
14
according to the prior art. To shut the steam line
20 there is provided
a single, essentially circular valve
21 with a radius r. The valve
21
is swivel-mounted via bolts
30,
31 about an axis of rotation y in
the steam line
20. It has a moment of inertia I
y about said axis
of rotation y. A linear drive
23 which provides an acceleration torque M
y
via a lever
33 is used to swivel the valve
21. The moment of
inertia I
y of this valve is considerable. A high acceleration torque
M
y is therefore required.
FIG. 3 schematically illustrates a first exemplary embodiment of the invention.
The valve
21 has been subdivided according to the invention into four elements
25a,
25b,
25c,
25d, each
having its own drive
26a,
26b,
26c,
26d.
The elements
25a,
25b,
25c,
25d
are each rotatable about an axis y and have a moment of inertia I
y.
The drives
26a,
26b,
26c,
26d
each provide an acceleration torque M
y. The surface area covered
by the elements
25a,
25b,
25c,
25d
corresponds to the surface area that is also covered by the valve
21.
FIGS. 4 to
11 show further exemplary embodiments of the invention. The
cross-section of the steam line
20 is schematically represented by dash-dotted
lines. Whereas in FIG. 3 a separate drive
26a,
26b,
26c,
26d is provided for each element
25a,
25b,
25c,
25d, in the embodiment according
to FIG. 4 only two drives
26a,
26b are required. These
drives
26a,
26b act via lever gears
27a,
27b on two elements
25a,
25b and
25c,
25d respectively. The two outer elements
25a,
25d
are provided with roundings
28 for matching to the cross-section of
the steam line
20 and for improving the flow characteristics.
In the embodiment according to FIG. 5, all the elements
25a,
25b,
25c,
25d present are driven by a common drive
26
via a lever gear
27. In this exemplary embodiment the thickness d of the
elements
25a,
25b,
25c,
25d
is approximately half the width b. This ratio of width b to thickness d is
provided by way of example only, not as an advantageous embodiment. The precise
value of the thickness d is determined on the basis of strength considerations.
It is likewise shown that the width b corresponds to half the radius r and therefore
the statement b=2 r/n is applicable.
There are provided recesses
29 in the form of grooves or pockets which
do not extend over the entire thickness d. In the closed position illustrated in
FIG. 5, the cross-section of the steam line
20 is completely shut. The recesses
29 become deeper toward the edge of the elements
25b,
25c.
As soon as these elements
25b,
25c are rotated to clear
the cross-section of the steam line
20, a pre-opening is formed, as the
recesses
29 first reach the sealing plane approximately in the center of
the elements
25b,
25c.
As the elements
25a,
25b,
25c,
25d
are rotated, the cross-section of the steam line is therefore gradually cleared
and the load applied to the second turbine cylinders
15 is therefore increased
slowly. This improves the controllability of the steam turbine system
10
when the steam line
20 is cleared, e.g. for securing the station services
after load shedding.
One or more recesses
29 can be provided on one or more elements
25b,
25c. As shown in FIG. 5, the recesses
29 on adjacent elements
25b,
25c can be disposed on different sides, but advantageously
at the same height. However, other embodiments are also possible. The number, size
and arrangement of the recesses
29 are defined according the relevant considerations.
The additional figures show yet more embodiments of the present invention. FIG.
6 schematically illustrates the basic shapes of the four elements used
25a,
25b,
25c,
25d used as well as the projection
of the steam line
20 to be closed. The cross-section of the steam line
20
is locally matched to the shape of the elements
25a,
25b,
25c,
25d and is completely closed. It is likewise possible
to match the elements
25a,
25b,
25c,
25d to the cross-section or to match both the elements
25a,
25b,
25c,
25d and the cross-section,
as shown in FIG. 4, for example. The elements
25a,
25b,
25c,
25d can be made cuboid and matched to the modified
cross-section of the steam line
20 in the region of the steam line isolation
valve
14.
FIGS. 7 to
9 show further embodiments. In the case of FIG. 7, the central
element
25b is provided with lateral shoulders
32 in the peripheral
area of the steam line
20. These close cutouts on the lateral elements
25a,
25b which are required for rotating said elements
25a,
25b. FIGS. 8 and 9 show variants having three and four elements
25a,
25b,
25c,
25d respectively. These elements
25a,
25b,
25c,
25d can
be driven individually, in groups or all together. FIG. 10 shows an exemplary embodiment
with two elements
25a,
25b.
In the embodiments shown in FIGS. 3,
10 and
11, the elements
25a,
25b,
25c,
25d or
25a,
25b
used have the same moment of inertia I
y about their axis of rotation
y. The width of the individual elements
25a,
25b,
25c
is selected such that the elements
25a,
25b,
25c
have the same moment of inertia I
y about their axis of rotation
y. The central element
25b therefore has a smaller width. By using
elements
25a,
25b,
25c,
25d
with the same moment of inertia I
y, the same drive
26a,
26b,
26c,
26d can be used for each of
the elements
25a,
25b,
25c,
25d.
With a common drive for several or all of the elements
25a,
25b,
25c,
25d, the gear
27 provided is evenly stressed
and therefore has a longer service life.
The physical relationships will now be described in greater detail. The principles
used for the calculation may be obtained, for example, from W. Beitz, K. -H. Küttner
(Editors), "Dubbel-Taschenbuch für den Maschinenbau" [Dubbel's Mechanical
Engineering Pocket Book], Springer Verlag, 16th Edition, 1987, page B 32.
According to the prior art, the steam line
20 is closed by rotating
the valve
21 which covers the entire cross-section of the steam line
20.
The rotational acceleration {umlaut over (φ)} for closure depends on the
acceleration torque M
y applied and the moment of inertia I
y about
the axis of rotation y.
##EQU1##
The thickness of the valve
21 is much lower than its radius and can therefore
be disregarded for calculating the moment of inertia I
y. The moment
of inertia I
y,valve of a valve
21 is given by:
##EQU2##
where: m: mass of the valve
The moment of inertia I
y,cuboid of a cuboid element
25, likewise
disregarding the thickness, is given by:
##EQU3##
where: m: mass of the cuboid
The mass of valve
20 and element
25 may be regarded as identical,
as in both cases the same cross-section of the steam line
20 is to be closed.
Splitting the individual element
25 into a number n of identical
elements
25a,
25b,
25c,
25d produces:
##EQU4##
##EQU5##
When using 4 elements
25a,
25b,
25c,
25d, i.e. n=4:
##EQU6##
##EQU7##
Comparing the moments of inertia I
y,valve, I
y,cuboid
of an individual valve
21 and of four elements
25a,
25b,
25c,
25d, we get:
##EQU8##
Generalizing:
##EQU9##
By splitting up the single valve
21 into four identical elements
25a,
25b,
25c,
25d, the moment of inertia
I
y can therefore be reduced to a third. If a constant rotational acceleration
{umlaut over (φ)} is to be maintained, the acceleration torque M
y can
therefore likewise be reduced to a third. Even with a slight increase in the mass
through using a plurality of elements
25a,
25b,
25c,
25d, there is still a significant reduction in the moment of inertia I
y.
This picture is essentially unchanged even taking into account an appreciable
thickness d of the elements
25a,
25b,
25c,
25d. If, for example, we make the thickness d half the width b, we
get:
##EQU10##
Using n identical elements
25a,
25b,
25c,
25d gives
##EQU11##
##EQU12##
For n=4 we get:
##EQU13##
##EQU14##
Generalizing:
##EQU15##
Even allowing for the thickness d of the elements
25a,
25b,
25c,
25d, a reduction in the moment of inertia I
y
to less than half can be achieved. The acceleration torque M
y for the
drive
26 can therefore be significantly reduced with the rotational acceleration
{umlaut over (φ)} remaining constant.
Larger cross-sections can also be closed without significantly increasing
the acceleration torque M
y and with the rotational acceleration {umlaut
over (φ)} remaining constant. For the calculation, the dimensions of the
elements
25a,
25b,
25c,
25d
are varied in such a way that the same acceleration torque M
y is
produced as in the case of a valve
21. We then get:
##EQU16##
Disregarding the thickness d of the valves:
##EQU17##
If we in turn make n=4, this gives:
rnew=1.73
rold
Allowing for the thickness d of the elements
25a,
25b,
25c,
25d, we get:
##EQU18##
In turn putting n=4, we get:
The radius of the steam line
20 to be closed can therefore be increased
by 73% or 55% without it being necessary to increase the acceleration torque M
y
in order to retain the desired rotational acceleration {umlaut over (φ)}.
This corresponds to increasing the cross-sectional area of the steam line
20
by a factor of 3 and 2.4 respectively.
On the whole there is produced using the subject matter of the present invention
a steam line isolation valve
14 with a reduced moment of inertia I
y.
The acceleration torque M
y can therefore be significantly reduced, with
the dimensions of the steam line
20 to be closed remaining constant. Alternatively
larger cross-sections can be closed using the same acceleration torque.
*
