Abstrict Method, apparatus and computer program product are provided for
controlling desiccant regeneration in air dryer equipment for a
railroad locomotive. The method allows calculating an amount of
air conditioned by the air dryer equipment over a period of time.
The method further allows storing predefined criteria for initiating
desiccant regeneration in the air dryer equipment. The calculated
amount of air conditioned by the air dryer equipment is correlated
relative to the predefined criteria, and upon the calculated amount
of air conditioned by the air dryer equipment meeting the predefined
criteria, desiccant regeneration is initiated in the air dryer equipment.
Claims I claim as my invention:
1. A method for controlling desiccant regeneration in air dryer
equipment for a railroad locomotive, said method comprising: calculating
an amount of air conditioned by said air dryer equipment over a
period of time; storing a predefined criteria for initiating desiccant
regeneration in said air dryer equipment; correlating the calculated
amount of air conditioned by said air dryer equipment relative to
said predefined criteria; and upon the calculated amount of air
conditioned by said air dryer equipment meeting said predefined
criteria, initiating desiccant regeneration in said air dryer equipment.
2. The method of claim 1 wherein the calculating of the amount
of air conditioned by said air dryer equipment over said period
of time comprises measuring air flow rate passing through said air
dryer equipment, and mathematically integrating the measured air
flow rate to calculate the amount of air conditioned by said air
dryer equipment over said period of time.
3. The method of claim 1 with the air dryer equipment having two
desiccant tanks for drying compressed air, further comprising delivering
a flow of air to be dried to one tank, constituting a first tank,
and directing a volume of air that has been dried in the first tank
to the other tank, constituting a second tank, for regenerating
the desiccant in the second tank.
4. The method of claim 3 wherein said calculating comprises calculating
an amount of air conditioned by the first tank over a period of
time.
5. The method of claim 4 wherein said storing comprises storing
a predefined criteria for initiating desiccant regeneration of the
first tank of said air dryer equipment.
6. The method of claim 5 wherein said correlating comprises correlating
the calculated amount of air conditioned by said first tank relative
to said predefined criteria.
7. The method of claim 6 wherein upon the calculated amount of
air conditioned by said first tank meeting said predefined criteria,
initiating desiccant regeneration of said first tank by reversing
the flow of air as between the tanks, with a flow of air to be dried
being directed to the second tank and directing a volume of the
dried air from the second tank to the first tank to regenerate desiccant
in the first tank.
8. Apparatus for controlling desiccant regeneration in air dryer
equipment in a locomotive, said apparatus comprising: a first processor
configured to calculate an amount of air conditioned by said air
dryer equipment over a period of time; memory for storing a predefined
criteria based on the amount of air that has been conditioned for
initiating desiccant regeneration in said air dryer equipment; a
comparator configured to correlate the calculated amount of air
conditioned by said air dryer equipment relative to said predefined
criteria; and a second processor for initiating desiccant regeneration
in said air dryer equipment when the calculated amount of air conditioned
by said air dryer equipment meets said predefined criteria.
9. The apparatus of claim 8 further comprising a flow meter for
measuring air flow rate that passes through said air dryer equipment
over said period of time.
10. The apparatus of claim 9 wherein said flow meter generates
a signal indicative of air flow rate.
11. The apparatus of claim 8 wherein the first and second processors
are present in one processing device.
12. The apparatus of claim 11 wherein said processing device is
embedded within said air dryer equipment.
13. The apparatus of claim 10 wherein said first processor is configured
to mathematically integrate said signal indicative of air flow rate
over said period of time, the result of said integration comprising
the calculated amount of air conditioned by said air dryer equipment
over said period of time.
14. The apparatus of claim 8 wherein said air dryer equipment comprises
a tube having a constriction for passing air conditioned by said
air dryer equipment, and further wherein a pressure sensor is disposed
across said constriction to measure pressure changes across said
constriction as air flows by said constriction, said pressure changes
indicative of air flow rate that passes through said air dryer equipment
over said period of time.
15. The apparatus of claim 14 wherein said first processor is coupled
to said pressure sensor to receive a signal indicative of said pressure
changes.
16. The apparatus of claim 10 wherein said first processor is configured
to mathematically integrate said measurement of pressure changes
over said period of time, the result of said integration comprising
the calculated amount of air conditioned by said air dryer equipment
over said period of time.
17. The apparatus of claim 14 wherein said first and second processors
comprise a processing device external relative to said air dryer
equipment.
18. The apparatus of claim 14 wherein said first and second processors
comprise a processing device embedded within said air dryer equipment.
19. A system for controlling desiccant regeneration in air dryer
equipment for a railroad locomotive, with the air dryer equipment
having two desiccant tanks for drying compressed air, with piping
and valving delivering a flow of air to be dried to one tank, constituting
a first tank, and directing a volume of air that has been dried
in the first tank to the other tank, constituting a second tank,
for regenerating the desiccant in the second tank, said system comprising:
a first processor configured to calculate an amount of air conditioned
by said first tank over a period of time; memory for storing a predefined
criteria based on the amount of air that has been conditioned for
initiating desiccant regeneration in said first tank; a comparator
configured to correlate the calculated amount of air conditioned
by said first tank relative to said predefined criteria; and a second
processor for initiating desiccant regeneration in said first tank
when the calculated amount of air conditioned by said first tank
meets said predefined criteria by reversing the flow of air as between
the tanks, with a flow of air to be dried being directed to the
second tank and directing a volume of the dried air from the second
tank to the first tank to regenerate desiccant in the first tank.
20. The apparatus of claim 19 wherein the first and second processors
comprise the same processing device.
21. An article of manufacturing comprising a computer program product
comprising computer-readable program code for controlling desiccant
regeneration in air dryer equipment for a railroad locomotive, the
computer-readable program code in said article of manufacture comprising:
computer-readable program code for calculating an amount of air
conditioned by said air dryer equipment over a period of time; computer-readable
program code for defining a predefined criteria for initiating desiccant
regeneration in said air dryer equipment; computer-readable program
code for correlating the calculated amount of air conditioned by
said air dryer equipment relative to said predefined criteria; and
computer readable program code for initiating desiccant regeneration
in said air dryer equipment once the calculated amount of air conditioned
by said air dryer equipment meeting said predefined criteria.
Description [0001] This application claims the benefit of U.S. Application
Ser. No. 60/581063 which is hereby incorporated by reference in
its entirety.
BACKGROUND OF THE INVENTION
[0002] It is known to use multi-cylinder air compressors on freight
and passenger locomotives to supply compressed air to various locomotive
systems, such as the operating and control equipment of a railway
air brake system. Prior art techniques for servicing the air compressor
system have essentially required uninstalling and shipping major
components of the air compressor system, such as the entire compressor,
to a specialized compressor servicing site. This approach may lead
to unnecessary costs and delays, if the type of component causing
the malfunction was one that could be replaced in-situ at the locomotive
(i.e., as installed onboard the locomotive) without having to incur
the delays and expenses associated with shipping the entire compressor
to the specialized servicing site. However, heretofore there was
no effective procedure or test apparatus to diagnose locomotive
air compressors in-situ to determine if the malfunction was due
to an in-situ serviceable component or to a cause that required
removal of the air compressor system and servicing off-board of
the locomotive.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The features and advantages of the present invention will
become apparent from the following detailed description of the invention
when read with the accompanying drawings in which:
[0004] FIG. 1 illustrates a schematic representation of an exemplary
locomotive air compressor system that benefits from aspects of the
present invention; and
[0005] FIG. 2 is made up of FIGS. 2A-2C that collectively depicts
a flow chart that illustrates an exemplary sequence of tests that
may be performed on the air compressor system of FIG. 1 for identifying
malfunctioning components while the system remains onboard the locomotive.
[0006] FIG. 3 is a schematic representation of one exemplary embodiment
of air dryer equipment, as may be configured for performing a condition-based
desiccant regeneration process in lieu of regenerating at a fixed
time interval.
DETAILED DESCRIPTION OF THE INVENTION
[0007] The inventor of the present invention has innovatively recognized
a sequence of diagnostics techniques that may be performed in-situ
onboard a locomotive for identifying in a locomotive air compressor
system (out of various components that make up such a system) a
specific malfunctioning component that is likely to require a servicing
action and further identifying a type of servicing action appropriate
for correcting the malfunction. This type of technique is particularly
advantageous in the locomotive industry since now one may be able
to replace certain identified components in-situ on the locomotive
while at a generic or non-specialized locomotive service shop without
having to uninstall and ship main components of the compressor system
for servicing at a specialized suppliers site. This is a significant
improvement over prior art techniques that have essentially required
uninstalling and shipping major components of the air compressor
system, such as the compressor, regardless of whether in fact there
is ultimately determined to be a need for such specialized servicing.
For example, a cylinder head including intake and outlet valves
could be replaced at the generic service shop without having to
uninstall and ship the entire compressor to the specialized suppliers
site. Below is a description of an exemplary compressor air system
that may benefit from the diagnostics techniques embodying aspects
of the present invention.
[0008] FIG.1 shows an air compressor system 10 including a pair
of intercoolers 12 and 14 an aftercooler 16 a main storage reservoir
18 and associated piping. In one exemplary embodiment air compressor
system 10 comprises a multi-cylinder, two-stage, air-cooled compressor
having a first low pressure cylinder 20 and a second low pressure
cylinder 22 and a high pressure cylinder 24 each of which may be
provided with cooling fins. As shown, the pair of low pressure cylinders
20 and 22 and the high pressure cylinder 24 may be mounted on and
supported by a crankcase 26 in the usual manner and include respective
pistons which are actuated by connecting rods driven by a rotatable
crankshaft 28. In one exemplary embodiment the crankcase 26 includes
a breather valve 27 and an oil-fill plug 29. One end of the crankshaft
28 may be coupled to and driven by a suitable rotatable prime mover,
such as an electric motor 17 or the like, while the other end of
the crankshaft 28 may be attached to a rotary cooling fan assembly
(not shown). Crankcase seals 21 and 23 are commonly employed to
seal both ends of the crankshaft 28 to prevent leakage of lubricating
fluid. One or more side removable covers 25 may be provided to provide
access to the interior of the crankcase 26.
[0009] An inlet valve 30 of the low-pressure cylinder 20 is connected
by conduit 32 to an intake filter 34 while an inlet valve 36 of
the low-pressure cylinder 22 is connected by conduit 37 to an air
intake filter 38. An outlet valve 40 of the low-pressure cylinder
20 is connected to an inlet header of the first intercooler 12 via
a pipe 42. It will be appreciated that although FIG. 1 illustrates
just one inlet and outlet valve per cylinder head assembly, in one
exemplary embodiment, each cylinder head assembly may comprise a
pair of inlet and outlet valves per cylinder head. Typically, the
valves may be spring-loaded valves responsive to negative or positive
pressure to reach either a closed or an open condition.
[0010] An outlet header of intercooler 12 is connected to one inlet
of a T-pipe fitting 44. Similarly, an outlet valve 46 of the low
pressure cylinder 22 is connected to an inlet header of the second
intercooler 14 via a pipe 48. An outlet header of intercooler 14
is connected to the other inlet of the T-pipe fitting 44 while
the outlet of the T-pipe fitting 44 is connected to an inlet valve
50 of the high pressure cylinder 24. An outlet valve 52 of high
pressure cylinder 24 is connected by suitable conduits and fittings
forming piping 54 to an inlet header of the aftercooler 16. An outlet
header of aftercooler 16 is connected by suitable conduits and fittings
forming piping 56 to the inlet of the main storage reservoir 18.
[0011] Below is a description of an exemplary sequence of tests
for identifying in a locomotive air compressor system any of various
components that are likely to require a servicing action that, for
example may performed in-situ onboard the locomotive or at an specialized
compressor servicing site based on the results of the performed
test sequence.
[0012] Crankcase Inspection Test:
[0013] Evacuate oil from crankcase and then remove side covers
25 and inspect the interior of the crankcase 26 e.g., bearings
and lubrication system. For example, if one detects the presence
of pieces of metal, or bad bearings, then a servicing decision would
be to remove the compressor for an overhaul. If this upfront test
is passed, one would reattach the side covers 25 and continue with
the tests below.
[0014] Intercoolers and Low Pressure Cylinder Tests:
[0015] Test 1A (Pressurizing Intercoolers and One of the Two Low
Pressure Cylinders):
[0016] 1. Remove air filters 34 and 38.
[0017] 2. Remove oil-fill plug 29
[0018] 3. Block breather valve 27
[0019] 4. Block one of the intake conduits (e.g., the conduit 32
that provides an intake to one of the low pressure cylinders, e.g.,
low pressure cylinder 20).
[0020] 5. Block the pipe that provides a discharge outlet to the
aftercooler 16. That is, block pipe 56.
[0021] 6. Install on the other intake conduit (e.g., conduit 37
that provides an intake to low pressure cylinder 22), a pressurizing
fixture (e.g., including a pressure gage and valve).
[0022] 7. Pressurize to a predefined pressure (e.g., 60 psi) and
start to measure time, e.g., start a timer.
[0023] 8. Record time elapsed upon reaching one or more predefined
pressure levels, e.g., 55 50 45 and 40 psi pressure.
[0024] 9. Compare the actual elapsed time recorded at the predefined
pressure levels relative to predefined threshold times.
[0025] 10. Check for possible air leak through intercoolers 12
and 14 e.g., visual check.
[0026] 11. Check for possible airflow through oil-fill opening
29.
[0027] The predefined pressure (e.g., 60 psi) applied in step 6
above is sufficiently high to cause intake valve 36 to open and
pressurize the low-pressure cylinder 22 as well as intercoolers
12 and 14. The predefined pressure is also sufficiently low to stay
within the pressure ratings of the intercoolers 12 and 14 and avoid
actuating the intake valve 50 of the high-pressure cylinder 22 to
an open condition. At this point, presuming the outlet valve 40
is operating properly, the head of the low-pressure cylinder 20
has not been pressurized because the outlet valve 40 is in a closed
condition in response to the applied pressure. Thus, one would perform
another sequence of steps for pressurizing the head of the low-pressure
cylinder 20. More specifically,
[0028] Test 1B (Pressurizing Intercoolers and the Other One of
Low Pressure Cylinders):
[0029] 1. Block the other one of the intake conduits (e.g., conduit
37) that provides an intake to low-pressure cylinder 22).
[0030] 2. Install on the other intake conduit (e.g., conduit 32
that provides an intake to low pressure cylinder 20), the pressurizing
fixture
[0031] 3. Pressurize to the predefined pressure (e.g., 60 psi)
and start to measure time, e.g., start a timer.
[0032] 4. Record time elapsed time upon reaching one or more predefined
pressure levels, e.g., 55 50 45 and 40 psi pressure.
[0033] 5. Compare the actual elapsed time recorded at the predefined
pressure levels relative to predefined threshold times.
[0034] 6. Check for possible air leak through intercooler 12 and
14 e.g., visual check
[0035] 7. Check for possible airflow through oil-fill opening.
[0036] The foregoing sequence is essentially arranged for determining
whether there is a leak in any (or both) of the intercoolers 12
and 14 and whether there is a leak in any of the low-pressure cylinder
heads, such as air leaking by the piston rings of any of the low-pressure
cylinder heads and into the crankcase. The inventor of the present
invention has identified failure mode indications associated with
respective components of the compressor system that may be observed
during the test sequence. One key advantage of the present invention
over prior art techniques is being able to accurately distinguish
and identify the type of failure modes that may be corrected in-situ
from those that will require removal of major equipment from the
locomotive for servicing at the specialized servicing site. Occurrence
of specific indications would point out to a likely malfunction
in a given component. For example, intercooler leaks may be generally
characterized as relatively slow leaks compared to a low-pressure
cylinder wall leak. The presence of intercooler leaks may be determined
by visual inspection and/or a relatively moderate depressurizing
rate (e.g., if the elapsed time to reach 40 psi is approximately
15 seconds, this may be indicative of an intercooler leak). Intercooler
leaks tend to be visually detectable since intercoolers that have
been in operational use for some time tend to collect visually detectable
debris in their interior.
[0037] In the event of a low-pressure cylinder wall leak, e.g.,
air passes into the crankcase from a respective one of the low-pressure
cylinder heads, then one may be able to detect airflow through the
oil-fill opening. This detection may be accomplished by monitoring
the condition of a tape or other suitable thin flexible member placed
over the oil-fill opening. In addition, service personnel may feel
or hear such airflow. Moreover, a low-pressure cylinder wall leak
tends to exhibit a higher depressurizing rate as compared to an
intercooler leak. For example, while an intercooler leak may take
about 15 seconds to reach 40 psi, a low-pressure cylinder wall leak
may take just 5 seconds or less to reach 40 psi. The ability to
determine the presence of an intercooler failure versus a cylinder
wall failure is significant since the intercoolers may be readily
replaced at the locomotive without having to remove the entire compressor
whereas a cylinder leak into the crankcase typically requires removal
of the entire compressor for an appropriate overhaul at a specialized
service site.
[0038] It has been observed from test data that variation in the
recorded elapsed times (indicative of different depressurizing rates)
obtained during Tests 1A and 1B tend to indicate that the intercoolers
12 and 14 are functioning properly and that the cause of this variation
is likely to be caused by some other malfunctioning component, but
not the intercoolers. This follows since during Tests 1A and 1B
both intercoolers represent an assembly tested in common during
each test and thus variations that may arise in the recorded elapsed
times would tend to point to a different failure mode, such as leakage
in one of the low-pressure cylinder walls.
[0039] Test 2--Aftercooler and High Pressure Cylinder Tests:
[0040] 1. Open intake conduits to low-pressure cylinders 20 and
22.
[0041] 2. Install pressurizing fixture at aftercooler discharge
outlet. That is, pipe 56.
[0042] 3. Pressurize to a predefined pressure, e.g., 80 psi and
start to measure time, e.g., start a timer.
[0043] 4. Record time elapsed upon reaching one or more predefined
pressure levels, e.g., at 75 70 65 and 60 psi.
[0044] 5. Compare the actual elapsed time recorded at the predefined
pressure levels relative to predefined threshold times.
[0045] 6. Check for possible air leak through aftercooler 16 e.g.,
visual check
[0046] 7. Check for possible airflow through oil-fill opening.
[0047] One aspect of this test allows pressurizing the aftercooler
16 and determining the presence of a leak in the aftercooler. The
presence of such a leak may be determined by visual inspection and/or
a relatively moderate depressurizing rate (e.g., if the elapsed
time to reach 60 psi is approximately 15 seconds, this may be indicative
of an aftercooler leak. Another aspect of this test also allows
determining a malfunction in the outlet valve 52 of the high-pressure
cylinder 24. For example, if the outlet valve 52 is operating properly,
then when the aftercooler 16 is pressurized through pipe 56 that
valve should remain closed and the pressurization should be limited
to the aftercooler 16. In the event of a leaky outlet valve 52 in
the high-pressure cylinder, the head of the high-pressure cylinder
will also become pressurized. Test data reveals that once a leaky
valve has been found in a given cylinder head, there tends to be
a likelihood that the remaining valves associated with that cylinder
head will also require replacement. Thus, assuming the outlet valve
52 of the high-pressure cylinder is found to be leaky, one would
replace the cylinder head for that cylinder. This is a relatively
straightforward servicing operation that may be performed without
removing the entire compressor from the locomotive. As described
in the context of Tests 1A and 1B, monitoring whether there is airflow
through the oil-fill port may point to a leak in the high-pressure
cylinder head, such as air leaking by the respective high-pressure
piston rings and into the crankcase. Once again being able to determine
different failure modes is significant since different course of
actions will be taken depending on the specific malfunction or failure
mode that has been identified. For example, replacement of the aftercooler
16 and/or the high-pressure cylinder head including the respective
intake and outlet valves 50 and 52 may be performed at the locomotive
whereas a cylinder leak into the crankcase will require removal
and shipping of the compressor for overhaul at a specialized compressor
service site.
[0048] Test 3--(Crankcase Pressure Test):
[0049] 1. Remove test fixture from aftercooler discharge outlet.
[0050] 2. Install pressurizing fixture at oil fill port.
[0051] 3. Pressurize to a predefined pressure, e.g., 10 psi, and
start to measure time, e.g., start a timer.
[0052] 4. Compare the actual elapsed time recorded at the predefined
pressure levels relative to one or more predefined threshold times,
e.g., at 9 8 7 6 5 4 3 and 2 psi pressure.
[0053] This test primarily allows determining the health of the
crankcase seals 21 and 23. In one exemplary embodiment, with the
motor 17 installed, physical access to the end of the crankshaft
where seal 23 is situated is not realizable. Thus, by pressurizing
the crankcase and monitoring a depressurization rate and comparing
to a predefined threshold, (e.g., if the elapsed time to reach 2
psi is approximately 60 seconds), one may obtain an indication of
crankcase seal health without having to remove the compressor motor.
[0054] Referring back to FIG. 1 air dryer equipment 60 may be
connected to remove moisture and/or other particulates, such as
oil particulates, that may be present in the compressed air to avoid
condensation and/or contamination on the surfaces of one or more
locomotive equipment (not shown) situated downstream that receive
the pressurized air. In one known exemplary embodiment, the dryer
equipment may comprise adsorbent-type air dryer that uses a regenerative
desiccant that adsorbs moisture, at least up to a certain level
of adsorption capacity. The moisture accumulated by the desiccant
is then removed via a stream of dried air redirected through the
desiccant to purge the moisture into the atmosphere. In one known
technique, the air dryer equipment is responsive to a timer signal
so that the regeneration process is performed at a fixed interval,
(e.g., approximately every 2 minutes) regardless of actual usage
of compressed air by the equipment downstream. This known technique
forces the air compressor system to turn on and off based on the
fixed timing for regeneration regardless of the actual consumption
of compressed air by the locomotive equipment downstream.
[0055] In one exemplary embodiment of a system in accordance with
aspects of the present invention, a flowmeter 62 may be coupled
to provide a signal indicative of the flow rate and/or pressure
changes of the compressed air passing therethrough to a controller
64. The flow rate may be mathematically integrated over a period
of time to calculate the actual volume of compressed air passing
through the flowmeter 62. A memory or look-up table 66 may be used
to compare the volume of compressed air actually used relative to
a predefined volume for performing the regeneration process, as
may be based on the adsorption capacity of the desiccant. Once the
volume of compressed air actually used equals or exceeds the predefined
volume for performing regeneration, a regeneration signal would
be sent by controller 64 to the dryer equipment to perform the regeneration
process. That is, in lieu of regenerating at a fixed time interval,
one commences the regeneration process using a condition-based regeneration
technique, such as may based on the actual utilization of pressurized
air, as may be actually utilized by the equipment downstream supplied
by the air compressor system.
[0056] FIG. 3 is a schematic representation of one exemplary embodiment
of air dryer equipment 60 as may be configured for performing a
condition-based desiccant regeneration process in lieu of solely
regenerating at a fixed time interval. The description that follows
will provide a brief operational overview of air dryer equipment
60. Furthermore, details will be provided of a relatively low-cost
and uncomplicated modification to commercially available air-drying
equipment that would allow for performing a condition-based regeneration
process embodying aspects of the present invention. By way of example,
such a modification may be performed to air dryer model 994 purveyed
by Graham-White Manufacturing Co. It will be understood that in
its broad aspects, the present invention is not limited to any particular
type of air dryer model and/or manufacturer.
[0057] After a coalescer 300 has substantially removed bulk liquids
and particulates, e.g., oil particles, from compressed air passing
from reservoir 18 (FIG. 1), air that flows from coalescer 300 essentially
just includes water vapor. This moist air may be directed though
a first set of desiccant-filled towers; let us say desiccant towers
302 and 304 by an inlet diverter valve 306. By way of example,
air may flow in a first direction (e.g., upwards) in desiccant tower
302 and then in a second direction (e.g., downwards) in desiccant
tower 304. Air from desiccant tower 304 flows through an outlet
valve 308 that passes substantially dry, oil-free and clean compressed
air. This air passes through a constriction 309 in outlet tube 311
and at least a portion of this air is directed to air-driven equipment
(not shown) situated downstream relative to air dryer equipment
60. As air passes through constriction 309 a change in pressure
(Venturi effect) develops across such a constriction. The inventor
of the present invention has innovatively recognized that the addition
of a suitable pressure sensor 313 across constriction 309 provides
one alternative embodiment for measuring the airflow rate passing
through outlet tube 311. Essentially, this embodiment may be viewed
as one practical way for achieving the operational functionality
of flowmeter 62 (FIG. 1) without requiring costly and time-consuming
equipment redesign. That is, a relatively low-cost and uncomplicated
modification can be made to presently existing equipment to provide
an airflow rate measurement that may be mathematically integrated
by controller 64 to calculate the actual volume of compressed air
passing through tube 311.
[0058] It will be appreciated that controller 64 need not be a
separate controller relative to air dryer equipment 60 since the
processing functions for performing a condition-based desiccant
regeneration may be programmed into an embedded controller, as may
be part of the air dyer equipment 60. Once a condition-based determination
is performed relative to the first set of desiccant-filled towers,
the inlet diverter valve 306 is actuated to switch the flow of air
through a second set of desiccant-filled towers, such as desiccant
towers 310 and 312.
[0059] Although FIG. 3 illustrates two sets of desiccant towers,
wherein each set is made up of two desiccant towers or tanks, it
will be appreciated that the present invention is not limited to
any specific number of desiccant tanks. Generically, one may use
just two desiccant tanks for drying the compressed air. For example
the piping and valving may be set for delivering a flow of air to
be dried to one tank, e.g., constituting a first tank, and directing
a volume of air that has been dried in the first tank to the other
tank, e.g., constituting a second tank. One may start regeneration
of desiccant in the second tank when the calculated amount of air
conditioned by the first tank meets a predefined criteria by reversing
the flow of air as between the two tanks. The predefined criteria
is based on the amount of air that has been conditioned by the first
tank. Once desiccant in the second tank has been reconditioned,
a flow of air to be dried is directed to the second tank and a volume
of the dried air from the second tank is directed to the first tank
to regenerate desiccant in the first tank. The above process of
air drying and desiccant regeneration is repeated in alternating
fashion switching from one tank to the other tank based on the amount
of air that has been conditioned at any given tank, as opposed to
performing regeneration based on a fixed time interval that may
have little to do with the actual condition of the desiccant.
[0060] Desiccant towers undergoing regeneration, let us say desiccant
towers 310 and 312 may be isolated relative to compressed air flow
by inlet diverter valve 306 and outlet shuttle valve 308. The exhaust
valve 314 which is connected to the desiccant towers undergoing
regeneration (e.g., desiccant towers 310 and 312), may be opened
to reduce to atmosphere the pressure in such desiccant towers. Some
amount of dry pressurized air may pass through a self-adjusting
purge valve 316. Details regarding the operation of purge valve
are well known to those skilled in the art and for the sake of not
burdening the reader with minutia for purposes of the present invention
such details are omitted from the present description. Suffices
to say that self-adjusting purge valve 316 is responsive to the
amount of air that passes through outlet tube 311. More specifically,
the more air that passes through outlet tube 311 the more air that
self-adjusting purge valve 316 passes to the desiccant towers undergoing
regeneration.
[0061] In one exemplary embodiment, air that passes through purge
valve 316 is directed through one of a pair of purge check valves
320 and then through the desiccant towers undergoing regeneration.
As dry air flows through the desiccant beads in desiccant towers
310 and 312 this dry air flushes adsorbed water from the desiccant
beads therein and discharges such air to atmosphere through open
exhaust valve 314. At the end of a regeneration cycle and prior
to switching inlet diverter valve 306 exhaust valve 314 is closed
and air from self-adjusting purge valve 316 may be used to gradually
repressurize the regenerated desiccant towers. Switching of diverter
valve 306 and exhaust valve 314 may be performed in response to
pressurizing effects caused upon applying regeneration switching
signals to solenoid valves 324 and 326 by controller 64. That is,
aspects of the present invention are directed to a regeneration
control strategy that is based on the actual condition of the desiccant
beads, as opposed to a purely timed regeneration control strategy
regardless of whether or not the desiccant has reached (or is relatively
close) to moisture saturation. It is estimated that when using a
condition-based regeneration process during a locomotive idling
condition, the period of time for initiating a regeneration cycle
may be approximately 30 minutes, as compared to performing regeneration
approximately every 2 minutes under the known temporal-based regeneration
control strategy. It will be appreciated that this regeneration
technique substantially reduces the operational demands on air compressing
system 10 (FIG. 1) and is conducive to a relatively longer air compressor
life as well as incremental reductions in operational and servicing
costs for the compressor.
[0062] The inventor of the present invention has further recognized
that the flow meter 62 may be used to monitor degradation in the
air compressing ability of the air compressor system. For example,
the air compressor may be rated to supply a volume of compressed
air within a predefined range at a predefined pressure. For example,
in one exemplary embodiment, the compressor may be rated to deliver
pressurized air in a range from approximately 145 cfm to approximately
180 cfm at a pressure of about 140 psi. As the air compressor ages,
the ability to compress air will be gradually diminished, and it
is thus desirable to determine whether the air compressor is able
to pressurize air within an acceptable range. It is further contemplated
that one could, based on past and present air compressing capacity,
predict a future point in time when the air-compressing ability
of the compressor system may be unacceptable. One may collect data
from field-deployed air compressors and/or analytically or empirically
derived data to extrapolate in time the present compressing ability
of a given compressor to predict the point in time at which the
compressing ability of the given compressor may no longer be acceptable
so as to perform appropriate maintenance for that given compressor
before reaching an unacceptable level of performance. For example,
one may collect and store historical data from a plurality of air
compressors like the one undergoing inspection to establish reference
data for comparing actual data from the compressor undergoing inspection
to predict the point in time when that compressor is likely to require
a comprehensive servicing action, e.g., compressor overhaul. This
data may be collected and stored on a suitable memory device and
the data may be downloaded either during a servicing operation at
a locomotive service site, or the data may be transmitted by communications
equipment onboard the locomotive to a remote diagnostics center.
One exemplary sequence for determining air-compressing capacity
may be as follows:
[0063] Air Compressing Capacity Test:
[0064] 1. Run air compressor for a predefined amount of time (e.g.,
30 minutes) with the compressor motor at a predefined first rpm
(e.g., 600 rpm).
[0065] 2. Hold the pressure at a predefined pressure (e.g., 140
psi).
[0066] 3. Monitor parameters indicative of reaching a set of predefined
operational conditions, an example of such parameters may be lubrication
oil temperature and oil pressure.
[0067] 4. Use the signal from the flowmeter 62 to calculate volume
of pressurized air actually supplied by the compressor.
[0068] 5. Run air compressor for a predefined amount of time (e.g.,
10 minutes) with the compressor motor at a second rpm (e.g., 1050
rpm) and repeat steps 2-4 above.
[0069] 6. Compare actual volume of pressurized air delivered by
the compressor relative to a predefined air volume range indicative
of whether the capacity of the compressor to deliver pressurized
air is acceptable or not.
[0070] FIG. 2 is a flow chart of a sequence of tests embodying
aspects of the present invention for performing diagnostics of an
air compressor system on board a locomotive. In one exemplary sequence,
as illustrated at block 200 one may initially perform crank case
inspection to determine the health of mechanical components within
the interior of the crankcase. As shown at decision diamond 202
if the crank case inspection is not passed then, as shown at block
244 the corrective action would be to remove the compressor from
the locomotive for compressor overhaul at a specialized service
site. If the crank case inspection test is passed one proceeds to
block 204 to perform Test 1A, that is pressurizing the intercoolers
and one of the two lower pressure cylinders. As shown at decision
diamond 206 if an intercooler leak is detected, as shown at block
208 one proceeds to replace the leaking intercooler in-situ. To
verify that the intercooler leak has been corrected, one would return
to block 204 and repeat Test 1A. As shown at decision diamond 210
another possible failure mode that may be detected while performing
Test 1A is detecting a low-pressure cylinder wall leak. If a low-pressure
cylinder wall leak is detected, one proceeds through connecting
node 100 to block 244 to remove the compressor from the locomotive
for compressor overhaul at a specialized service site.
[0071] Presuming that no intercooler leak or low pressure cylinder
wall leak has been detected, one continues at block 212 to perform
Test 1B. That is, pressurizing the intercoolers and the other one
of the low-pressure cylinders. As shown at decision diamond 214
if an intercooler leak is detected, as shown at block 216 one proceeds
to replace the leaking intercooler in-situ. To verify that the intercooler
leak has been corrected, one would return to block 212 and repeat
Test 1B. As shown at decision diamond 218 another possible failure
mode that may be detected while performing Test 1B is detecting
a low-pressure cylinder wall leak. If a low-pressure cylinder wall
leak is detected, one proceeds through connecting node 100 to block
244 to remove the compressor from the locomotive for compressor
overhaul at a specialized service site. Presuming that no intercooler
leak or low-pressure cylinder wall leak has been detected, one continues
at block 220 to perform Test 2. That is, aftercooler and high-pressure
cylinder test. One of the possible failure modes that may be diagnosed
while performing Test 2 as shown at decision diamond 222 is an
aftercooler leak. In the event of an aftercooler leak at block 224
one proceeds to replace the aftercooler in-situ. To verify that
the aftercooler leak has been corrected, one would return to block
220 and repeat Test 2. As shown at decision diamond 226 another
possible failure mode that may be detected while performing Test
2 is a malfunctioning high-pressure valve, e.g., a malfunctioning
intake high-pressure valve. If a malfunctioning high-pressure valve
is detected, then one proceeds to block 228 to perform a corrective
action in-situ, such as replacing the high-pressure cylinder head
assembly. To verify that the high-pressure valve malfunction has
been corrected one may return to block 220 to restart Test 2. As
shown at decision diamond 230 a third possible failure mode that
may be detected while performing Test 2 would be to detect a high-pressure
cylinder wall leak. If such a high-pressure cylinder wall leak is
detected, one proceeds through connecting node 100 to block 244
to remove the compressor from the locomotive for compressor overhaul
at the specialized service site.
[0072] Once Test 2 has been successfully passed, one proceeds to
block 232 to perform Test 3. That is, the crankcase pressurization
test. As shown at decision diamond 234 in the event no crankcase
seal leak is detected, one then proceeds to block 236 to perform
the air compressing capacity test. In the event a crank case seal
leak is detected, one proceeds to block 238 to replace the crankcase
seals. As shown at decision diamond 240 if the air compressing
capacity is determined to be within an appropriate range of volume
of pressurized air this would be the end of the test sequence as
shown at block 242. If the air compressing capacity is unacceptable,
then one proceeds to block 244 to remove the compressor from the
locomotive for a compressor overhaul servicing.
[0073] While the preferred embodiments of the present invention
have been shown and described herein, it will be obvious that such
embodiments are provided by way of example only. Numerous variations,
changes and substitutions will occur to those of skill in the art
without departing from the invention herein. Accordingly, it is
intended that the invention be limited only by the spirit and scope
of the appended claims. |