U.S. patent number RE37,153 [Application Number 08/518,266] was granted by the patent office on 2001-05-01 for variable pressure reducing device.
This patent grant is currently assigned to Sentry Equipment Corp.. Invention is credited to Richard R. Henszey, Bruce W. Weiss.
United States Patent |
RE37,153 |
Henszey , et al. |
May 1, 2001 |
Variable pressure reducing device
Abstract
A variable pressure reducing device for reducing high pressure
in steam and hot water samples forces the liquid through an annular
passageway between a pair of rods within a complementary pair of
tubes. The flow rate through the rod-in-tube device, or the
pressure drop across the device, is adjustable by means of a
rotatable guide screw for adjusting the position of the rods within
the tubes. The rods are tapered to provide a smooth flow of liquid
through the device. The seal around the guide screw is self
energized by means of a seal jacket between a valve gland and a
stem portion of the guide screw constructed so that the biasing
force of a spring on the seal jacket is supplemented by pressure
from liquid flowing through the device The guide screw is centered
within the valve gland to keep the guide screw properly aligned,
particularly when the device is used with a motor for rotating the
guide screw to adjust the position of the rods.
Inventors: |
Henszey; Richard R.
(Oconomowoc, WI), Weiss; Bruce W. (Whitefish Bay, WI) |
Assignee: |
Sentry Equipment Corp.
(Oconomowoc, WI)
|
Family
ID: |
25501641 |
Appl.
No.: |
08/518,266 |
Filed: |
August 23, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
959068 |
Oct 13, 1992 |
05333648 |
Aug 2, 1994 |
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Current U.S.
Class: |
138/26; 138/46;
277/647 |
Current CPC
Class: |
F15D
1/02 (20130101); G01N 1/2035 (20130101) |
Current International
Class: |
F15D
1/02 (20060101); F15D 1/00 (20060101); G01N
1/20 (20060101); F15D 001/02 () |
Field of
Search: |
;138/26,30,43-46 ;137/14
;251/214,264,266 ;277/205,188A ;73/863.81,863.86 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
American Veriseal Corp. brochure, Catalog No. AV984, 1984.* .
Sentry--"VREL Sample Pressure Reducing Device Application
Bulletin", Jan. 1989..
|
Primary Examiner: Brinson; Patrick
Attorney, Agent or Firm: Jansson, Shupe, Munger &
Stomma, Ltd.
Claims
We claim as our invention:
1. A variable pressure reducing device comprising:
a barrel;
a pair of tubes joined to one end of the barrel;
a pair of rods adjustably insertable within the tubes with each rod
having a relatively wide diameter at an upper end of the rod, a
relatively narrow diameter at a lower end of the rod, and a smooth
tapered outer surface extending from the upper end to the lower
end;
a rotatable guide screw and complementary threaded ring within the
barrel for adjusting the rods;
a valve gland, including an internal annular ridge seat with a
central opening therein, placed over the other end of the
barrel;
the threaded guide screw having an annular shoulder complementary
to the ridge seat and having a stem portion projecting through the
central opening of the gland;
a low friction thrust washer between the shoulder of the guide
screw and the ridge seat of the gland;
an annular seal jacket between the stem portion of the guide screw
and an inner wall of the gland;
a spring for biasing an inner wall portion of the jacket against
the stem portion of the guide screw and for biasing an outer wall
portion of the jacket against the inner wall of the gland;
a back-up washer abutting against the seal jacket;
annular centering means for centering the stem portion of the guide
screw within the gland; and
a nut with a central opening placed over the stem portion of the
guide screw and threaded over the gland.
2. The variable pressure reducing device according to claim 1,
wherein the centering means comprises a bearing and washer.
3. The variable pressure reducing device according to claim 1,
wherein the centering means comprises a bushing.
4. The variable pressure reducing device according to claim 1
further comprising a motor for rotating the guide screw to adjust
the position of the rods within the tubes.
5. The variable pressure reducing device according to claim 1,
wherein pressure from liquid flowing through the device further
presses the seal jacket against the guide screw and gland wall.
6. A variable pressure reducing device for reducing high pressure
of liquids comprising:
a pair of rods adjustably insertable within a complementary pair of
tubes by means of a rotatable guide screw;
each rod having a smooth outer surface tapered from a relatively
wide diameter at an upper end of the rod down to a relatively
narrow diameter at a rounded lower end of the rod;
the guide screw being held within a barrel by a valve gland;
a seal jacket within an annular space formed by the outer diameter
of a stem portion of the guide screw and the inner diameter of a
wall of the gland;
a spring for biasing an inner wall section of the seal jacket
against the stem portion of the guide screw and for biasing an
outer wall section of the seal jacket against the gland wall;
a washer abutting the seal jacket; and,
centering means for centering the stem portion of the guide screw
within the gland.
7. The variable pressure reducing device according to claim 6,
wherein the guide screw is held within the barrel by the valve
gland by means of an annular ridge seat within the gland, a
complementary annular shoulder on the guide screw, and a thrust
washer between the shoulder and ridge seat.
8. The variable pressure reducing device according to claim 8,
wherein the centering means comprises a bearing and washer.
9. The variable pressure reducing device according to claim 8,
further comprising a belt drive motor for rotating the guide screw
to adjust the position of the rods within the tubes.
10. The variable pressure reducing device according to claim 7,
wherein the centering means comprises a bushing.
11. The variable pressure reducing device according to claim 10,
further comprising a direct drive motor for rotating the guide
screw to adjust the position of the rods within the tubes.
12. An improved variable pressure reducing device of the type which
includes a pair of tubes joined to one end of a barrel, a
complementary pair of rods adjustably connected to a threaded ring
on a rotatable threaded guide screw within the barrel, the pair of
rods being insertable within the pair of tubes, respectively,
thereby forming a passageway between the outer diameter of the rods
and the inner diameter of the tubes for fluid to flow therethrough,
the improvement comprising tapering the rods with a smooth outer
surface from a relatively wide diameter at an upper end of the rod
which is connected to the threaded ring down to a relatively narrow
diameter at an opposite rounded end of the rod to form a
progressively narrower annular passageway to smooth the flow of
fluid therepast.
13. The improved variable pressure reducing device according to
claim 12, further comprising an improvement in the sealing means of
the device comprising:
a valve gland on the other end of the barrel including an internal
annular ridge seat and a central opening therein;
the guide screw having an annular shoulder complementary to the
ridge seat and a stem portion projecting through the central
opening of the gland;
a low friction thrust washer between the shoulder of the guide
screw and the ridge seat of the gland;
a seal jacket in an annular space formed by the inner diameter of a
wall of the gland and the outer diameter of the stem portion of the
guide screw;
a spring for biasing the seal jacket against the wall of the gland
and the stem portion of the guide screw;
a washer abutting the seal jacket;
centering means for centering the guide screw; and,
a nut over the open end of the annular space in the gland.
14. The variable pressure reducing device according to claim 13,
wherein the centering means comprises a bearing and washer.
15. The variable pressure reducing device according to claim 13,
wherein the centering means comprises a bushing.
16. The variable pressure reducing device according to claim 13,
wherein pressure from liquid flowing through the device further
presses the seal jacket against the guide screw and gland.
17. The variable pressure reducing device according to claim 16,
further comprising a motor connected to the stem portion of the
guide screw for motorized adjustment of the position of the rods
within the tubes..Iadd.
18. A variable pressure reducing device for reducing high pressure
in steam and liquid sampling lines, said device comprising:
at least one tube forming at least one elongate passageway, wherein
said at least one elongate passageway has an inlet end for
receiving fluid at an elevated first pressure and an exit end for
discharging fluid at a second pressure lower than said elevated
pressure;
at least one elongate rod mounted for movement in said at least one
elongate passageway, wherein said at least one elongate rod has a
first end and a second end such that said at least one elongate rod
is smoothly tapered from said first end to said second end for
providing a substantial pressure loss therealong;
an adjustment mechanism for moving said at least one elongate rod
into and out of said at least one elongate passageway, wherein said
adjustment mechanism is connected to said first end of said at
least one elongate rod; and
an annular gap between said at least one elongate rod and said at
least one elongate tube wherein said annular gap becomes
progressively narrower along said at least one elongate rod in a
linear direction from said first end of said at least one elongate
rod to said second end of said at least one elongate rod.
.Iaddend..Iadd.
19. The device of claim 18 wherein said at least one elongate rod
tapers from said first end to said second end. .Iaddend..Iadd.
20. A variable pressure reducing device for reducing high pressure
in steam and liquid sampling lines, said device comprising:
first and second elongate passageways;
first and second elongate rods extending along said first and
second passageways, respectively, wherein each rod of said first
and second elongate rods has a length and a first end and a second
end such that at least said first rod is free of a step and
therefore smoothly tapered along a length from a relatively wide
diameter at said first end to a relatively narrow diameter at said
second end; and
first and second separate annular gaps between each passageway of
said first and second elongate passageways and said first and
second elongate rods extending therealong, respectively, wherein
each gap of said first and second separate annular gaps has a
linear, unstepped outer boundary along said length of said first
and second elongate rods, respectively, such that fluid pressure
decreases along said first passageway from said relatively narrow
diameter of said second end of said first rod to said relatively
wide diameter of said first end of said first rod.
.Iaddend..Iadd.
21. The device of claim 20 wherein a diameter of each gap of said
first and second separate annular gaps changes along a length of
each gap of said first and second separate annular gaps. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a variable pressure reducing device to
reduce the pressure and control the flow of high pressure liquids.
In particular, the invention relates to a rod-in-tube-type pressure
reducing device with an improvement in construction of the rods to
smooth the flow of liquid through the device and an improvement in
the sealing means to provide easier adjustability of the
device.
2. Background of the Art
Numerous applications of high pressure fluid systems require, at
some point in the system, reduction of the pressure to allow safe
handling of the fluid. For instance, a sample withdrawn from a
steam and hot water system in a power plant must be reduced in
pressure before the sample can be introduced into analyzing
instrumentation or handled safely by plant personnel. A number of
devices are used in the power plant industry to reduce the high
pressure of steam and hot water, such as fixed orifice valves or
pressure regulators, but material erosion frequently experienced in
such devices can lead to loss of function. Capillary tubing, also
commonly used to reduce high pressure in liquid samples, may become
blocked by crud or scale, requiring complete shutdown of the sample
line while the capillary tubing is cleaned or replaced.
Another type of device for reducing high pressure in liquids is
applicant's earlier version of a variable pressure reducing element
(VREL.TM.). The VREL is a rod-in-tube device in which the pressure
of an incoming liquid is reduced as the liquid is forced to travel
through a narrow gap between a stepped rod and the inner diameter
of a tube. Because the work is done over the entire length of the
stepped rod, localized stresses are held to a minimum, resulting in
a very long service life compared with orifice valves and pressure
regulators in which the pressure drop is taken over a very short
distance. The flow through the VREL, or the pressure drop across
it, can be adjusted while the liquid is flowing through the device
by changing the position of the rods in the tubes. Turning the
handle in one direction or the other moves the rods in or out of
the tubes. If crud blocks the flow of liquid, the rods can be fully
retracted to allow the high pressure liquid to blow the dirt
through the device.
This earlier version of the VREL, however, has a number of
drawbacks and disadvantages. The flow past the steps in the stepped
rod causes turbulence and unsteady liquid flow, which is
undesirable particularly when the device is used in connection with
applicant's new automated sample conditioning panel (which is the
subject of a co-pending application). Scale and crud also have a
tendency to build up on the steps of the stepped rod, inhibiting
flow through the device.
In the earlier version of applicant's VREL device, a packing seal,
comprised of a thick Teflon .TM. ring sandwiched between two
washers and compressed ("packed") within a valve gland by a
threaded nut, caused high compressive forces making it difficult to
adjust the device. A leak in the seal would typically be fixed by
plant personnel merely tightening the nut further, which in turn
simply increased the compressive forces and making it further
difficult to adjust the device.
SUMMARY OF THE INVENTION
An improved variable pressure reducing device comprising an
adjustable rod-in-tube construction, with smoother flow and easier
adjustability than earlier devices, is disclosed.
Flow through the device is improved by tapering the rods, thereby
eliminating the turbulence caused by the stepped rods experienced
in the earlier version of the device. Adjustability of the device
is greatly improved by replacing the packing seal with a spring
biased seal jacket which is not dependent on compressive forces to
seal the device. The seal jacket is also uniquely designed to
utilize the high pressure liquid within the device to enhance the
sealing characteristics of the seal jacket, thereby providing, in
effect, a self-energized seal. The invention is further provided
with a means for centering and adjusting an internal guide screw,
used to adjust the position of the rods within the tubes, for
adapting a device for use in motorized applications.
The primary objects of the invention are therefore to provide a
variable pressure reducing device comprising a pair of rods
adjustably inserted within a pair of tubes for reducing high
pressure liquid samples over the length of the rods; to provide a
relatively smoother flow of liquid through the device by gradually
tapering the rods as compared with the stepped rod design of
applicants earlier device; to provide an improved, self-energized
sealing means which allows easy adjustment of the device; to adapt
the device for use with motorized adjustment means; and, to provide
an improved variable pressure reducing device adapted especially
for use on an automated sample conditioning system.
Other objects and advantages of the invention will become apparent
from the following description taken in connection with the
accompanying drawings which set forth, by way of illustration and
example, certain preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The drawings, which are a part of the specification and which
present exemplary embodiments of the present invention, include the
following:
FIG. 1 is a front plan view of an improved variable pressure
reducing element (VREL .TM.) constructed in accordance with the
principles of the present invention.
FIG. 2 shows the internal rods which fit within the tubes, and a
guide screw for adjusting the position of the rods within the tubes
of the variable pressure reducing element.
FIG. 3 is a cross sectional view of the seal assembly of the
variable pressure reducing element.
FIG. 4 is a cross-sectional view showing the rods within tubes.
FIG. 5 is a cross-sectional view of a bushing which, in some
applications, can be used in place of the bearing and washer shown
in FIG. 3.
FIG. 6 is a front plan view showing a direct drive motor for
adjusting the rods.
FIG. 7 is a front plan view showing a belt drive motor for
adjusting the rods.
DETAILED DESCRIPTION OF THE INVENTION
A variable pressure reducing element (VREL .TM.) 10 is used to
reduce the pressure and control the flow of high pressure liquids.
The device 10 is especially useful for reducing the pressure of
steam and hot water samples in a power plant front as high as 5000
psi down to about 50 psi so that the liquid can be safely piped to
an analyzer instrument or handled manually for a grab sample.
The VREL 10 is a rod-in-tube pressure reducing, flow control device
comprising two stainless steel tubes 12 joined to one end of a
larger tube or barrel 14. A pair of tapered rods 16 .[.is.].
.Iadd.are .Iaddend.inserted into the two tubes 12. One end 17 of
each rod 16 is connected to a threaded ring 22 on a threaded guide
screw 24 within the barrel 14. The other end 18 of each rod 16 is
rounded. Between the ends 17 and 18, the rod 16 is smoothly tapered
from a relatively wide diameter at the end 17 which is connected to
the threaded ring 22 down to a relatively narrow diameter at the
rounded end 18 of the rod 16. The tubes 12 have a fixed inner
diameter throughout their length.
The liquid enters the VREL 10 at inlet 26 and exits from outlet 28.
The pressure of the incoming liquid is reduced as the liquid is
forced to travel through the progressively narrower annular gap 30
between the outer diameter of the tapered rod 16 and the inner
diameter of tube 12. Taking the change in pressure over a long
length eliminates the problem of hydrogen ion dissociation. The
pressure drop through the VREL 10 is a function of the length of
the rods 16 which are inserted into the tubes 12, i.e. the pressure
drop across the VREL 10 is adjustable by changing the location of
the rods 16 within the tubes 12.
The flow through the VREL 10 can be adjusted, even while the liquid
is flowing through it, by changing the position of the rods 16 in
the tubes 12. By rotating the threaded guide screw 24 in one
direction or the other, the threaded ring 22 moves the tapered rods
16 in or out of the tubes 12. The position of the rods 16 within
the tubes 12, together with the tapered characteristic of the rods
16, control the pressure drop and flow rate of the liquid through
the VREL 10. In the event of a crud burst becoming lodged in the
space between the rod 16 and tube 12, the VREL 10 can be cleared by
backing off the rods 16 until the obstruction is blown free.
Furthermore, the tapering of the rods 16 provides a smooth liquid
flow through the device which is desirable for application of the
VREL on an automated sample conditioning system. The smooth taper
of the rods causes no flow disturbances which may lead to unsteady
flow rate (the stepped rods caused unsteadiness at certain
positions).
As the liquid flows through the VREL 10, the liquid exerts a
frictional force against the inlet rod in a direction toward the
top end of the VREL 10 (i.e. toward the threaded ring 22), and a
downward force against the outlet rod. Under optimal operating
conditions, the forces approximately balance each other. The
balanced arrangement facilitates low mechanical stress on the valve
for easy adjustment and promotes long valve life. As crud builds up
on the rods, however, a large unbalanced force may develop tending
to push the rods 16 and the guide screw 24 up and out of the VREL
device 10. For this reason, the VREL sealing means is designed to
hold down a large upward directed force in the device.
The VREL sealing means, shown in FIG. 3, comprises a valve gland 34
placed on the top end of the barrel 14, i.e. opposite the tapered
rods 16. The valve gland 34 has an internal annular ridge seat 36
with a central opening. An upper stem portion 31 of the guide screw
24 projects through the central opening of the annular ridge 36 on
the gland 34. An annular shoulder 32 on the guide screw 24
complementary to the ridge seat 36 of the gland 34 holds the guide
screw 24 within the barrel 14. A thrust washer 38 is placed between
the shoulder 32 on the guide screw 24 and the ridge seat 36 of the
gland 34. The thrust washer 38, despite being compressed between
the shoulder 32 of the guide screw 24 and the ridge seat 36 of the
gland 34, permits the guide screw 24 to turn fairly easily relative
to the gland. The thrust washer 38 should be made of a low friction
material which causes negligible contamination to the liquid
flowing through the device, such as PEEK .TM. Teflon .TM., nylon,
acetal or other suitable material. PEEK .TM. is a high lubricity
material (i.e. very smooth, low friction material)available from
LNP Engineering Plastics, Malvern, Pa.
The seal is designed to facilitate easy rotation of the guide screw
24 with relatively low torques, and to be effectively
self-energizing by utilizing the pressure from the liquid flowing
through the device. A Teflon .TM. jacket 40 with a U-shaped cross
section is placed in an annular space formed by the inner diameter
of the wall of the gland 34 and the outer diameter of the stem
portion 31 of the guide screw 24. Inner and outer wall portions of
the Teflon jacket 40 provide a seal against the outer diameter of
the guide screw 24 and the inner diameter of the gland 32,
respectively. An annular spring 42 placed within the channel of the
U-shaped jacket 40 presses the inner wall portion of the jacket 40
against the outer diameter of the guide screw 24, and presses the
outer wall portion of the jacket 40 against the inner diameter of
the wall of the gland 34. Further, pressurized liquid "leaking" up
through narrow gaps past the guide screw shoulder 32, thrust washer
38 and ridge seat 36 provides additional force to press the walls
of the jacket 40 against the outer diameter of the guide screw 24
and the inner diameter of the gland 34. The sealing effect of the
jacket 40 is therefore effectively self-energized in that high
pressure liquid within the VREL 10 acts in cooperation with the
seal jacket 40 and spring 42 to improve the seal.
On the "dry" side, a backup washer 44 also made of PEEK .TM. is
placed against the upper side of the Teflon jacket 40. Teflon under
high pressure has a tendency to flow, so the PEEK .TM. backup
washer 44 inhibits distortion of the Teflon jacket 40 to maintain
its integrity and sealing capability. The PEEK .TM. backup washer
44 is very hard and has no gaps, and it also has a close fit around
the outer diameter of the guide screw 24 and inner diameter of the
gland 34.
In applications in which a motor is used to turn the guide screw 24
to adjust the rods 16 within the tubes 12, it is important to
ensure that the guide screw 24 remains centered in the device. Two
types of motor drive units have been designed and tested for use
with the VREL device disclosed herein--a direct drive and a belt
drive. In a belt drive, the drive axis of the motor is displaced
laterally from the axis of the guide screw 24, and the drive axis
of the motor is connected to the stem portion 31 of the guide screw
24 with a V-belt assembly. Since the V-belt assembly places a
lateral load on the guide screw, a bearing 46 is used to center the
guide screw 24 in the gland 34. The lower portion of the bearing 46
fits within the annular space inside the gland 34 with the bottom
face of bearing 46 abutting the top surface of the backup washer
44. The bearing 24 has an annular flange which fits on the upper
surface of the gland 34. The bearing 46, made of stainless steel,
keeps the guide screw 24 centered and provides for relatively easy
rotation of the guide screw even with a lateral load applied
against it by the belt drive motor. A bearing washer 48 placed over
the bearing 46 provides support over the entire top surface area of
the bearing 46.
In applications where very little lateral loading of the guide
screw .[.46.]. .Iadd.24 .Iaddend.is expected, like in the case of a
direct drive motor where the drive axis of the motor aligned with
the axis of the guide screw 24, a bronze bushing 50 as shown in
FIG. 5 may be used in place of the bearing 46 and washer 48. A
threaded nut 52 with a central opening is placed over the stem
portion 31 of the guide screw 24 and threaded onto the top of the
valve gland 34. Thus, the shoulder 32 of the guide screw 24 holds
the guide screw 24 within the gland 34, and the nut 52 then holds
the seal jacket 40 and spring 42, backup washer 44, bearing 46 and
bearing washer 48 (or bushing 50) within the gland 34.
* * * * *