U.S. patent application number 14/362520 was filed with the patent office on 2014-10-30 for dry gas seal for supercritical co2 pump-high pressure buffer.
This patent application is currently assigned to NUOVO PIGNONE S.P.A.. The applicant listed for this patent is NUOVO PIGNONE S.P.A.. Invention is credited to Carlo Del Vescovo, Donato Antonio Ripa, Maurizio Sciancalepore.
Application Number | 20140321972 14/362520 |
Document ID | / |
Family ID | 45571624 |
Filed Date | 2014-10-30 |
United States Patent
Application |
20140321972 |
Kind Code |
A1 |
Del Vescovo; Carlo ; et
al. |
October 30, 2014 |
DRY GAS SEAL FOR SUPERCRITICAL CO2 PUMP-HIGH PRESSURE BUFFER
Abstract
Systems and methods for assuring a safe working condition of a
dry gas seal when a pump/compressor is in a standstill condition. A
small booster compressor is added to boost the pressure of an
intermediate buffer gas injected into the chamber between a primary
seal and a secondary seal of the dry gas seal. Control components
detect when the barrier gas pressure drops below a preconfigured
value and when detected, closes a valve in a line to a flare safe
area and turns on the compressor. The boosted intermediate buffer
gas, Nitrogen or dry air, slows the flow of untreated process gas
through the primary seal of the dry gas seal and prevents icing of
the primary seal.
Inventors: |
Del Vescovo; Carlo;
(Firenze, IT) ; Ripa; Donato Antonio; (Firenze,
IT) ; Sciancalepore; Maurizio; (Firenze, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NUOVO PIGNONE S.P.A. |
Florence |
|
IT |
|
|
Assignee: |
NUOVO PIGNONE S.P.A.
Florence
IT
|
Family ID: |
45571624 |
Appl. No.: |
14/362520 |
Filed: |
November 27, 2012 |
PCT Filed: |
November 27, 2012 |
PCT NO: |
PCT/EP2012/073720 |
371 Date: |
June 3, 2014 |
Current U.S.
Class: |
415/1 ;
415/112 |
Current CPC
Class: |
F16J 15/3484 20130101;
F04D 29/124 20130101; F16J 15/406 20130101; F04D 29/108
20130101 |
Class at
Publication: |
415/1 ;
415/112 |
International
Class: |
F04D 29/10 20060101
F04D029/10 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 5, 2011 |
IT |
CO2011A000057 |
Claims
1. A system for assuring a safe working condition of a dry gas
seal, associated with a pump or a compressor, during standstill
operating conditions, the system comprising: a barrier fluid
pressure detector configured to determine when barrier fluid
pressure of a barrier fluid drops below a preconfigured lower limit
and when said pump or said compressor, at said standstill operating
condition is pressurized at a settle-out pressure; a controllable
valve connected to a chamber between a primary seal and a secondary
seal of said dry gas seal, said controllable valve associated with
a vent to a flare-safe area; a booster compressor configured to
boost the pressure of an intermediate buffer gas injected into said
chamber; and a control system configured to operate said
controllable valve and said booster compressor based on said
barrier fluid pressure.
2. The system of claim 1, wherein said controllable valve is
associated with a flare line connected to said dry gas seal.
3. The system of claim 1, wherein said barrier fluid is carbon
dioxide.
4. The system of claim 1, wherein said intermediate buffer gas is
Nitrogen.
5. The system of claim 1, wherein said intermediate buffer gas is
dry air.
6. The system of claim 1, wherein said booster compressor boosts
said pressure of the intermediate buffer gas to a preconfigured
pressure when said barrier fluid pressure drops below said
preconfigured pressure.
7. The system of claim 6, wherein said preconfigured pressure is
less than a pressure of an area to be sealed associated with said
dry gas seal.
8. The system of claim 6, wherein said preconfigured pressure is
greater than a pressure of an area to be sealed associated with
said dry gas seal.
9. A method for assuring a safe working condition of a dry gas seal
associated with a liquefied gas pump or a liquefied gas compressor
when said liquefied gas pump or said liquefied gas compressor is in
a transient operating condition, said method comprising: detecting
a barrier fluid pressure below a preconfigured value; closing a
valve connected to said dry gas seal; and starting a booster
compressor associated with an intermediate buffer gas and
maintaining said buffer gas pressure at said preconfigured
value.
10. A system for protecting a dry gas seal associated with a
liquefied gas pump or a liquefied gas compressor, said system
comprising: a barrier fluid pressure detector configured to detect
when a pressure, associated with a barrier fluid injected into said
dry gas seal, drops below a predefined lower limit; a controllable
valve configured to regulate flow from said dry gas seal to a
flare-safe area; a booster compressor configured to change pressure
of an intermediate buffer gas injected into said dry gas seal; a
chamber pressure detector configured to measure pressure in a
chamber between a primary seal and a secondary seal; and a control
system configured to control said controllable valve to regulate
flow and said booster compressor to change pressure based on said
the measured pressure in the chamber and a preconfigured pressure
value.
11. The system of claim 10, wherein said controllable valve is
associated with a flare line connected to said dry gas seal.
12. The system of claim 10, wherein said barrier fluid is carbon
dioxide.
13. The system of claim 10, wherein said intermediate buffer gas is
Nitrogen or dry air.
14. The system of claim 10, wherein said booster compressor boosts
said pressure of the intermediate buffer gas to a preconfigured
pressure when said pressure of the barrier fluid drops below said
preconfigured pressure.
15. The system of claim 2, wherein said barrier fluid is carbon
dioxide.
16. The system of claim 15, wherein said intermediate buffer gas is
Nitrogen or dry air.
17. The system of claim 16, wherein said booster compressor boosts
said pressure of the intermediate buffer gas to a preconfigured
pressure when said barrier fluid pressure drops below said
preconfigured pressure.
18. The system of claim 2, wherein said intermediate buffer gas is
Nitrogen or dry air.
19. The system of claim 18, wherein said booster compressor boosts
said pressure of the intermediate buffer gas to a preconfigured
pressure when said barrier fluid pressure drops below said
preconfigured pressure.
20. The system of claim 2, wherein said booster compressor boosts
said pressure of the intermediate buffer gas to a preconfigured
pressure when said barrier fluid pressure drops below said
preconfigured pressure.
Description
TECHNICAL FIELD
[0001] The present invention relates generally to dry gas seals for
compressors, pumps and, more specifically, to protect the integrity
of the primary dry gas seal during standstill conditions.
BACKGROUND
[0002] The application of dry gas seals to centrifugal compressor
shaft sealing has dramatically increased in recent years for many
reasons. The benefits offered by the use of dry gas seals on a
centrifugal compressor include improved compressor reliability and
the associated reduction of unscheduled downtime, elimination of
seal oil leaking into the compressor and the associated process
contamination, elimination of process gas contaminating the seal
oil and requiring sour seal oil reclamation through degassing
tanks, elimination of costs for replacement and disposal of sour
seal oil, reduction of operating costs based on the greater
efficiency of a dry gas seal, the reduction of maintenance costs
for the simpler dry gas seal system and the reduction of process
gas emissions.
[0003] Dry gas seal installation is also adoptable for centrifugal
pumps associated with liquefied gas. The many benefits of dry gas
seals at the running conditions of centrifugal compressors and
pumps mask problems associated with the use of dry gas seals on
centrifugal compressors and pumps at other operating conditions
such as the transient times of startup, shutdown and low-speed
idle. The reason dry gas seals are problematic at these times is
based on the requirement of a higher than suction pressure barrier
gas to prevent contamination of the dry gas seal with particulate
or liquid materials. The contamination can arrive, for example,
from the untreated process gas or from bearing lubrication oil.
[0004] A typical centrifugal compressor utilizing a dry gas seal
will divert a portion of the process gas from the high-pressure
discharge of the compressor then filter, dry and reduce the
pressure of the gas. The clean and dry barrier gas is then injected
upstream of the primary seal at a pressure slightly greater than
the suction pressure of the compressor. The higher pressure barrier
gas prevents the untreated process gas from entering the dry gas
seal where contaminates can infiltrate the tight tolerances of the
rotating dry gas seal surfaces and cause premature dry gas seal
ring failure.
[0005] During transient times of operation, the pressure of the
process gas from the discharge of the compressor is reduced to the
point where it is equal to the suction pressure of the compressor.
Consequently, it is no longer possible to use the flow from the
discharge of the compressor as a barrier fluid. Upstream of the
primary seal, in the seal chamber, there is a pressure very close
to the suction pressure of the compressor or pump. Downstream of
the primary seal there is a pressure established by a buffer fluid,
typically nitrogen or air available at a pressure of four to seven
bar. Further, the higher pressure and un-treated process gas
permeates the primary dry gas seal, transporting particulate and
liquid contamination. This problem is emphasized with carbon
dioxide (CO.sub.2) as the process flow. The carbon dioxide
(CO.sub.2) expansion through the tight tolerances of the dry gas
seal rings can form ice on the seal rings. Subsequently, when the
compressor returns to normal operating conditions, the
contamination between the dry gas seal rings results in premature
wear and failure of the dry gas seal.
[0006] Prior attempts to resolve this problem have centered on
providing a booster for the process fluid to maintain the barrier
gas at the conditions provided during normal operation of the
compressor or pump. This solution requires the similar treatment of
the process fluid with respect to filtering and heating to prevent
contamination of the dry gas seal. Accordingly, market pressure is
building for a system and method for preventing the backflow of
process fluid, and the associated contaminates, through the dry gas
seal during transient operating conditions.
SUMMARY
[0007] Systems and methods according to these exemplary embodiment
descriptions address the above described needs by providing a small
secondary compressor for boosting the pressure of an intermediate
buffer gas during operating conditions (i.e., startup, shutdown and
low-speed idle) when the fluid pressure from the discharge of the
pump is equal to the suction pressure of the area to be sealed by
the dry gas seal. A simple control system detects a drop in barrier
gas pressure in the dry gas seal (i.e., the trigger signal could be
but is not limited to simply the "no running" condition of the
turbomachinery) and protects the dry gas seal from icing by closing
a valve between the dry gas seal and a flare-safe area and starting
the secondary compressor to boost the intermediate buffer gas to a
preconfigured pressure based on the pressure of the process fluid
in the area to be sealed by the dry gas seal.
[0008] According to an exemplary embodiment of a system for
assuring a safe working condition of a dry gas seal during
standstill operations, a barrier fluid pressure measuring system
detects a drop in barrier fluid pressure. The exemplary embodiment
continues with a valve connecting the chamber between primary and
secondary seal with the flare. Further, the exemplary embodiment
continues with a booster compressor for boosting the pressure of an
intermediate buffer gas injected into the chamber between the
primary and secondary seal. Next the exemplary embodiment comprises
a control system for operating the booster compressor based on the
measured pressure between the primary and secondary seal.
[0009] According to another exemplary embodiment, a method for
assuring a safe working condition of a dry gas seal installed on a
liquefied gas pump when the pump is in a transient operating
condition, is presented. Continuing with the first step of the
exemplary method embodiment, the method detects the barrier gas
pressure below a preconfigured value. In the next step of the
exemplary method embodiment, the method closes a valve connected to
the dry gas seal. Further in the exemplary method embodiment,
starting a booster compressor associated with an intermediate
buffer gas and maintaining said chamber pressure at a preconfigured
value.
[0010] In a further exemplary embodiment, a liquefied gas pump dry
gas seal protection system is described. The exemplary embodiment
includes a means to detect when the pressure of the barrier fluid
drops below a lower limit. The exemplary embodiment further
includes a means to regulate the flow from the dry gas seal to a
flare-safe area. Continuing with the exemplary embodiment, included
is a means to increase the pressure of an intermediate buffer gas
injected into the dry gas seal. Continuing with the exemplary
embodiment, included is a means to measure the pressure of the
buffer gas. Next in the exemplary embodiment, a means to control
the means to regulate flow and means to increase pressure based on
the means to measure pressure and a preconfigured pressure
value.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The accompanying drawings illustrate exemplary embodiments,
wherein:
[0012] FIG. 1 depicts a prior art cross-section view of a dry gas
seal and the associated gas support system in an operating
condition;
[0013] FIG. 2 depicts a prior art cross-section view of a dry gas
seal and the associated gas support system in a standstill
condition;
[0014] FIG. 3 depicts an exemplary embodiment cross-section view of
a dry gas seal and the associated gas support system in an
operating condition;
[0015] FIG. 4 depicts an exemplary embodiment cross-section view of
a dry gas seal and the associated gas support system in a
standstill condition;
[0016] FIG. 5 depicts an exemplary embodiment pressure-enthalpy
diagram illustrating the gas leakage flow through the primary dry
gas seal when the pump is in the operating condition;
[0017] FIG. 6 depicts a prior art pressure-enthalpy diagram
illustrating the gas leakage flow through the primary dry gas seal
when the pump is in the standstill condition;
[0018] FIG. 7 depicts an exemplary embodiment pressure-enthalpy
diagram illustrating the gas leakage flow through the primary dry
gas seal when the pump is in the standstill condition; and
[0019] FIG. 8 is a flowchart depicting a method for maintaining
sufficient pressure in the chamber between the primary and
secondary dry gas seal to prevent contamination of the primary dry
gas seal.
DETAILED DESCRIPTION
[0020] The following detailed description of exemplary embodiments
refers to the accompanying drawings. The same reference numbers in
different drawings identify the same or similar elements. Also, the
following detailed description does not limit the invention.
Instead, the scope of the invention is defined by the appended
claims.
[0021] Looking to FIG. 1, a detailed diagram of a prior art
exemplary embodiment of a dry gas seal (DGS) system 100 for a
carbon dioxide (CO.sub.2) pump is presented. It should be noted in
the exemplary embodiment that any fluid in a supercritical state
can be used as a barrier fluid in place of the exemplary carbon
dioxide (CO.sub.2). The exemplary embodiment reflects the behavior
of the dry gas seal during operating conditions and includes a
CO.sub.2 pump 102 with its associated area to be sealed, a primary
(inboard) seal 104 of a dry gas seal, a secondary (outboard) seal
106 of the dry gas seal, a process fluid filter 108, a process
fluid heater 110, a valve and control element 112 for controlling
the flow to a flare-safe area, an intermediate buffer gas filter
114, intermediate buffer gas 116, barrier fluid 118, pressure
reduction valve 120, a primary dry gas seal chamber 122 and a
secondary dry gas seal chamber 124.
[0022] In general, this exemplary prior art embodiment depicts
process fluid, e.g. carbon dioxide, from the pump discharge being
used as a barrier fluid. The pressure of the barrier fluid is
reduced by a valve 120 and heated by a heater 110. Continuing with
the exemplary prior art embodiment, the barrier fluid is filtered
by filters 108 and injected into the primary dry gas seal chamber
122. In the exemplary embodiment, the pressure of the barrier fluid
is higher than the suction pressure of the pump and therefore
prevents the entry of any untreated process gas into the primary
seal 104.
[0023] Continuing with the exemplary embodiment, the carbon dioxide
(CO.sub.2) barrier fluid flows partly into the pump through the
inner labyrinth and partly to the primary vent through the primary
dry gas seal. Next in the exemplary embodiment, the carbon dioxide
(CO.sub.2) that flows into the pump reaches a suction pressure that
is higher than the critical pressure for carbon dioxide (CO.sub.2)
and accordingly will not experience icing or flushing. Further in
the exemplary embodiment, the carbon dioxide (CO.sub.2) that flows
through the primary seal to the primary vent expands from P1 to a
value established by the buffer gas (typically N.sub.2/air at 4-7
bar). It should be noted in the exemplary embodiment that the
temperature of the carbon dioxide (CO.sub.2) barrier fluid must be
maintained, by a heater, to a value high enough to avoid, during
the expansion, the risk of icing or flushing.
[0024] Continuing with the exemplary embodiment, an intermediate
buffer gas 116, e.g. nitrogen or dry air is filtered by filters 114
and injected into the secondary dry gas seal chamber 124. It should
be noted in the exemplary embodiment that gases other than nitrogen
or air are usable as a buffer gas. In the exemplary embodiment, the
pressure of the intermediate buffer gas 116 is higher than the
pressure of the barrier gas passing through the primary seal 104
and prevents the barrier gas from reaching the secondary seal 106.
In the exemplary embodiment, the mixture of barrier gas 118 and
intermediate buffer gas 116 in the secondary dry gas seal chamber
124 passes through a valve 112 and flows to a flare-safe area.
[0025] Looking now to FIG. 2, a detailed diagram of a prior art
exemplary embodiment of a dry gas seal (DGS) system 200 for a
carbon dioxide (CO.sub.2) pump is presented. The prior art
exemplary embodiment reflects the behavior of the dry gas seal
during a transient, e.g. standstill, condition and includes a
CO.sub.2 pump 202 with its associated area to be sealed, a primary
(inboard) seal 204 of a dry gas seal, a secondary (outboard) seal
206 of the dry gas seal, a process fluid filter 208, a process
fluid heater 210, a valve and control element 212 for controlling
the flow to a flare-safe area, an intermediate buffer gas filter
214, intermediate buffer gas 216, barrier fluid 218, pressure
reduction valve 220, a primary dry gas seal chamber 222 and a
secondary dry gas seal chamber 224.
[0026] Continuing with the prior art exemplary embodiment, the
CO.sub.2 pump is in a standstill condition and accordingly the
discharge pressure from the pump is equal to the pressure in the
area to be sealed 202. When the pump is in a standstill condition,
the pressure into the pump reaches a uniform value very close to
the suction pressure, know as "settle out pressure". It should be
noted in the prior art exemplary embodiment that the result of the
standstill condition is the process fluid from the pump discharge
can no longer act as a barrier fluid to prevent the flow of
untreated process fluid, from the area to be sealed 202, into the
primary seal 204. Further in the prior art exemplary embodiment,
the untreated process fluid is not heated or filtered and therefore
contaminates can enter the primary seal 204 and icing can occur in
the primary seal 204. It should also be noted in the prior art
exemplary embodiment that the pressure of the untreated process
fluid is greater than the pressure of the intermediate buffer gas
216 therefore the intermediate buffer gas 216 cannot prevent the
flow of untreated process fluid through the primary gas seal
204.
[0027] Continuing with FIG. 3, a detailed diagram of an exemplary
embodiment of a dry gas seal (DGS) system 300 for a carbon dioxide
(CO.sub.2) pump is presented. The exemplary embodiment reflects the
behavior of the dry gas seal during a operating, e.g. running,
condition and includes a CO.sub.2 pump 302 with its associated area
to be sealed, a primary (inboard) seal 304 of a dry gas seal, a
secondary (outboard) seal 306 of the dry gas seal, a flare valve
312, and a control element for controlling the flow to a flare-safe
area, an intermediate buffer gas filter 314, intermediate buffer
gas 316, barrier fluid 318, a primary dry gas seal chamber 322, a
secondary dry gas seal chamber 324, a booster compressor 326 and, a
booster compressor 326 discharge valve 328, a booster compressor
326 inlet valve 330 and a booster compressor 326 bypass valve
332.
[0028] In a non-limiting exemplary embodiment, while the pump is in
a running condition, the pressure in the area to be sealed 302 is
lower than the pressure of the barrier fluid 318, provided from the
pump discharge, and while the barrier fluid pressure is higher than
the pressure of the area to be sealed, flare valve 312 and booster
compressor 326 bypass valve 332 are open, booster compressor 326
discharge valve 328 and booster compressor 326 inlet valve 330 are
closed and booster compressor 326 is deactivated. Continuing with
the exemplary embodiment, the pressure of the barrier fluid does
not allow the process fluid to flow through the primary seal 304
and prevents contamination and icing of the primary seal 304.
[0029] Looking now to FIG. 4, a detailed diagram of an exemplary
embodiment of a dry gas seal (DGS) system 400 for a carbon dioxide
(CO.sub.2) pump is presented. The exemplary embodiment reflects the
behavior of the dry gas seal during a transient, e.g. standstill,
condition and includes a CO.sub.2 pump 402 with its associated area
to be sealed, a primary (inboard) seal 404 of a dry gas seal, a
secondary (outboard) seal 406 of the dry gas seal, a valve 412, and
control element, for controlling the flow to a flare-safe area, an
intermediate buffer gas filter 414, intermediate buffer gas 416,
barrier fluid 418, a primary dry gas seal chamber 422, a secondary
dry gas seal chamber 424, a booster compressor 426, a booster
compressor 426 discharge valve 428, a booster compressor 426 inlet
valve 430 and a booster compressor 426 bypass valve 432.
[0030] In a non-limiting exemplary embodiment, in "no running"
conditions of the pump or compressor (trip, shutdown, startup,
pressurized standstill, etc.), the pressure into the pump is
uniform and is equal to the settle out pressure value and can no
longer be used as a barrier fluid. In this exemplary embodiment
condition, the flare valve 412 and the booster compressor 426
bypass valve 432 is closed, the booster compressor 426 discharge
valve 428 and the booster compressor 426 inlet valve 430 is opened
and the booster compressor 426 is activated. It should be noted in
the exemplary embodiment that the booster compressor raises the
pressure of the intermediate buffer gas 416, injected into the
secondary dry gas seal chamber 424, to a predetermined pressure
(P3) just below the pressure in the area to be sealed 402.
Continuing with the exemplary embodiment, the increased pressure of
the intermediate buffer gas reduces the flow of process gas through
the primary seal 404 and prevents contamination and icing of the
primary seal 404. The exemplary embodiment booster compressor 426
operates in a discontinuous fashion, performing ON/OFF cycles.
Next, the exemplary embodiment booster compressor 426 is turned on
and the pressure into the secondary seal chamber 424 rises until it
reaches the pressure P3 and the booster compressor 426 is turned
off. The exemplary embodiment continues with the pressure in the
secondary seal chamber 424 slowly dropping, because of leakage of
buffer gas through the secondary seal 406. Continuing with the
exemplary embodiment, when the pressure in the chamber 424 between
the primary seal 404 and the secondary seal 406 drops below a
predetermined value (P3-dP3), the booster compressor 426 is turned
on. Further, it should be noted in the exemplary embodiment that
when the pump returns to operating conditions and barrier fluid 418
pressure rises above the pressure in the area to be sealed 402 the
booster compressor 426 is finally turned off
[0031] Turning now to FIG. 5, in a pressure-enthalpy diagram 500
illustrated is the pressure reduction of the barrier fluid through
the control valve 120, the temperature rise of the barrier fluid
through the heater 110 and the expansion of the treated leakage
flow through the primary seal to the primary vent with the pump in
running condition. The temperature in the exemplary embodiment is
high enough to avoid flushing and icing during the expansion.
[0032] Continuing now to FIG. 6, a carbon dioxide pressure-enthalpy
diagram 600 of a prior art exemplary embodiment dry gas seal system
in a standstill operating condition is presented. The prior art
exemplary embodiment illustrates the pressure difference 602
occurring through the primary seal 604 during a standstill
condition. In another aspect of the prior art exemplary embodiment,
the enthalpy diagram 600 depicts the expansion 604 of the untreated
carbon dioxide leakage flow through the primary seal and crossing
the triple point 606 and the bi-phase zones of the diagram for
carbon dioxide. Accordingly, the prior art exemplary embodiment
indicates that icing will occur in and around the primary seal and
will lead to premature failure of the primary seal.
[0033] Looking now to FIG. 7, an exemplary embodiment of a carbon
dioxide pressure--enthalpy diagram 700 of a dry gas seal system in
a standstill operating condition is presented. The exemplary
embodiment illustrates the pressure difference 702 occurring
through the primary seal during a standstill condition. In another
aspect of the exemplary embodiment, the enthalpy diagram 700
depicts the expansion 704 of the untreated carbon dioxide leakage
flow through the primary seal and not crossing the triple point 706
and neither bi-phase zone of the diagram for carbon dioxide.
Accordingly, the exemplary embodiment indicates that icing will not
occur in and around the primary seal.
[0034] Continuing now to FIG. 8, an exemplary method embodiment 800
for assuring a safe working condition of the dry gas seal and
preventing flushing and/or icing when the pump or compressor is in
a standstill condition is depicted. Starting at exemplary method
embodiment step 802, the pressure of the barrier fluid in the
chamber upstream of the primary seal is measured. In this exemplary
method embodiment, the measured barrier fluid pressure is compared
to a preconfigured value and an indication is generated if the
measured barrier fluid pressure is below the preconfigured
value.
[0035] Next at exemplary method embodiment step 804, if the
indication is presented that the barrier fluid pressure is below
the preconfigured value then a valve associated with the dry gas
seal and a flare-safe area is closed. In one aspect of the
exemplary method embodiment, the valve prevents the exit of any gas
from the chamber between the primary seal and the secondary seal
except by passing through the secondary seal. In another aspect of
the exemplary method embodiment, closing the valve reduces the
volume of intermediate buffer gas required to maintain the desired
pressure. Further in the exemplary method embodiment, the
intermediate buffer gas can be, but is not limited to, Nitrogen or
dry air.
[0036] Next at exemplary method embodiment step 806, a booster
compressor is started to boost the pressure of the intermediate
buffer gas injected into the chamber between the primary seal and
the secondary seal. In another aspect of the exemplary method
embodiment, the booster compressor is operated to maintain the
pressure based on a preconfigured value for the chamber pressure
that is near the value of the pressure of the process fluid in the
area to be sealed by the dry gas seal. Continuing with the
exemplary method embodiment, the preconfigured value can
dynamically change based on changes in the pressure of the process
fluid in the area to be sealed by the dry gas seal. It should be
noted in the exemplary method embodiment that the process fluid can
be, but is not limited to, carbon dioxide.
[0037] Continuing with the exemplary method embodiment, at step 808
the rise in pressure in the chamber between the primary seal and
the secondary seal is monitored until the pressure reaches a
specified pressure (P3). Next, at step 810 of the exemplary method
embodiment, when the pressure reaches pressure P3, the booster
compressor is turned off. Further, at step 812 of the exemplary
method embodiment, the pressure is monitored until it falls to a
lower specified threshold and the method returns to step 806 and
restarts the booster compressor. It should be noted that the
exemplary method embodiment continues to cycle in this fashion
until the pump/compressor returns to a running condition.
[0038] The disclosed exemplary embodiments provide a system and a
method for protecting a dry gas seal from at least icing conditions
brought on by process fluid expanding through the primary seal of a
dry gas seal. It should be understood that this description is not
intended to limit the invention. On the contrary, the exemplary
embodiments are intended to cover alternatives, modifications and
equivalents, which are included in the spirit and scope of the
invention as defined by the appended claims. Further, in the
detailed description of the exemplary embodiments, numerous
specific details are set forth in order to provide a comprehensive
understanding of the claimed invention. However, one skilled in the
art would understand that various embodiments may be practiced
without such specific details.
[0039] Although the features and elements of the present exemplary
embodiments are described in the embodiments in particular
combinations, each feature or element can be used alone without the
other features and elements of the embodiments or in various
combinations with or without other features and elements disclosed
herein.
[0040] This written description uses examples of the subject matter
disclosed to enable any person skilled in the art to practice the
same, including making and using any devices or systems and
performing any incorporated methods. The patentable scope of the
subject matter is defined by the claims, and may include other
examples that occur to those skilled in the art. Such other
examples are intended to be within the scope of the claims.
* * * * *