U.S. patent application number 11/073146 was filed with the patent office on 2005-09-08 for gas compressor dual drive mechanism.
Invention is credited to Manning, John B..
Application Number | 20050196298 11/073146 |
Document ID | / |
Family ID | 34915186 |
Filed Date | 2005-09-08 |
United States Patent
Application |
20050196298 |
Kind Code |
A1 |
Manning, John B. |
September 8, 2005 |
Gas compressor dual drive mechanism
Abstract
A dual drive mechanism for a gas compressor includes a pulley
and belt drive system to provide power to a gas compressor using
either an electric motor or a reciprocating engine. The source of
the power can be chosen by the operator of the system depending on
a number of variables, including the cost of electric power.
Inventors: |
Manning, John B.; (Lakeland,
FL) |
Correspondence
Address: |
BURNS & LEVINSON LLP
1030 15TH STREET NW, SUITE 300
WASHINGTON
DC
20005-1501
US
|
Family ID: |
34915186 |
Appl. No.: |
11/073146 |
Filed: |
March 4, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60550812 |
Mar 5, 2004 |
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Current U.S.
Class: |
417/364 ;
417/410.1 |
Current CPC
Class: |
F04B 35/04 20130101;
F04B 35/002 20130101 |
Class at
Publication: |
417/364 ;
417/410.1 |
International
Class: |
F04B 017/00; F04B
035/04 |
Claims
I claim:
1. In a dual-drive system for operating a natural gas compressor
using a natural gas engine, an electric motor, or both to
redundantly and alternatively drive the natural gas compressor, the
improvement comprising: retro-fitting a pre-existing natural gas
compression system that includes a natural gas engine and a natural
gas compressor operably connected to each other by a main drive
shaft, said retro-fitting being effected by providing an electric
motor operably connected to a second drive shaft and means to
operably connect said second drive shaft to the main drive shaft so
that the electric motor can drive the natural gas compressor.
2. The improvement of claim 1, wherein the means to operably
connect said second drive shaft to the main drive shaft is a pulley
and belt drive system.
3. The improvement of claim 1, wherein the main and second drives
share load.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority benefit from provisional
U.S. application Ser. No. 60/550,812 filed Mar. 5, 2004, the
contents of which are incorporated herein by reference in their
entirety.
FIELD OF THE INVENTION
[0002] The invention is related to the natural gas energy industry
and more particularly to the field of mechanical drive systems for
gas compressors.
BACKGROUND OF THE INVENTION
[0003] In the natural gas gathering industry, there have been two
basic gas compressor units available in the 1000 to 4000 hp range.
One is an electric driven gas compressor and the other is a
reciprocating engine driven gas compressor. Electric driven gas
compressors in this class range have been predominantly utilized in
the offshore drilling industry and in isolated cases for landside
use. Electric driven gas compressors are particularly useful in
cutting down on polluting emissions and tend to be easier to
maintain.
[0004] Although an electric driven gas compressor offers more
favorable maintenance features, the fluctuating and often high
price of electricity have prevented electric driven compressors
from being more widely utilized. For example, the majority of
electric utilities in the US consider the availability of extra
capacity when establishing an electricity rate to larger industrial
users of electricity. Larger industrial users are often penalized
in the form of higher electricity prices for peak electricity
demands that exceed the industry's base load requirements,
especially when the industry requires instantaneous and short
spikes, for example when starting an electric motor. Starting an
electric motor can require up to a 650 percent increase in the
normal operating demand of the electric motor while starting the
motor. This power demand requires the utility to have the extra
capacity in reserve. This reserve or peak load demand is more
expensive to provide. The extra cost in most cases makes the use of
electric motor driven compressors less feasible than running a gas
compressor on a reciprocating gas engine.
[0005] Reciprocating gas engine driven compressors are utilized in
the majority of gas compressor stations. A portion of the natural
gas being forwarded at the gas compressions station is utilized to
operate the natural gas fired engines that drive the gas
compressors. Due to the high cost of a reciprocating gas fired
engine, most gas compressor units utilize high speed reciprocating
gas engines in the compressor packages to reduce cost, rather than
utilizing slower speed engines. The operations and maintenance cost
of the reciprocating gas engines is usually high and a large
portion of the overall cost of operating a gas compressor.
Unscheduled down time due to unexpected engine failures are a
common complaint, and major overhauls of the engine are costly and
frequently required. In comparison, an electric motor driven
compressor is appealing since an electric motor driven compressor
requires less maintenance and increased run time for the gas
compression system operators, subject to the cost constraints of
electricity.
[0006] It is thus desirable to reduce the cost of operating and
maintaining gas compression operations, while increasing efficiency
of the system employing the gas compressor.
SUMMARY OF THE INVENTION
[0007] It is an object of the invention to provide an alternative
drive source to power a gas compressor such that cost is reduced,
while maintenance and operating simplicity are magnified. A dual
drive mechanism provides an opportunity to reduce the price of
electricity to operate a gas compressor on an electric motor, and
allows a compressor operator to choose to operate the gas
compressor on a reciprocating engine or on an electric motor,
depending on the economic advantages of the energy source. When
compared to current methods and technology for driving a gas
compressor, the dual drive mechanism provides significant economic
benefit to gas compression operators.
[0008] The dual drive mechanism accomplishes such improvements by
incorporating the use of a pulley and belt drive system to
effectively provide the options of driving a single gas compressor
on an electric motor or on a reciprocating engine. The dual drive
mechanism is designed to retrofit an existing compressor that is
modified to accept the new dual drive mechanism and the addition of
an electric motor, or a new gas compressor unit can be assembled
with the dual drive mechanism. Retrofitting modifications can be
accomplished using a kit.
[0009] The dual drive mechanism will allow the operator to startup
the gas compressor and bring it up to speed with a reciprocating
engine. Through use of an electronic load-sharing device, the
electric motor will slowly begin to take over driving the
compressor. The dual drive mechanism prevents the electric motor
from requiring any peak or instantaneous load demands from the
utility, and allows the utility to provide the electricity required
to operate the motors at optimally reduced rates. The utility will
benefit from a constant base load consumption of electricity
without peak load demands, and the larger the load, the better the
benefit.
[0010] In circumstances where the utility offers a floating rate to
industry customers, or where the price of natural gas fluctuates,
the compressor station operators can switch back and forth from the
engine drive or electric motor drive depending on the price of
electricity verses the price of gas. The fluctuations in the price
of gas are a daily occurrence to which the industry pays close
attention. Thus, the retrofitted dual drive system includes an
operations and monitoring controls package that allows the unit to
be switched over from one drive to the other from a remote
location, or local computer network. For example, a desktop or a
laptop computer modem or phone line can be connected and
communicate with the system installed on the modified
compressor.
[0011] When operating the compressor on the electric motor, the
compression station operator can increase the profitability of his
operations by selling the available natural gas that is not being
burnt as fuel in the natural gas reciprocating engine.
[0012] Many gas compression operators operate gas compression
stations that could increase their capacity (throughput) at certain
sites by adding more gas compressor units, but cannot, due to the
emissions of current engines installed at the site. The dual drive
mechanism will allow an increase in compression capacity at such
sites by switching those sites to the dual drive mechanism and
running the compressor off of the electric motor instead of the
engines.
[0013] Further, the dual drive mechanism increases redundancy due
to the dual drive. Should the electric motor fail or be in need of
repair or maintenance, the compressor can be run on the
reciprocating engine until the unit can be put back into service
operating on the electric motor, or visa versa. The option of
switching to a different manner of operation can significantly
increase efficient production.
BRIEF DESCRIPTION OF THE FIGURES
[0014] For a better understanding of the present invention,
reference is made to the figures which are incorporated herein by
reference and in which:
[0015] FIG. 1 is a plain view drawing of the twin drive mechanism
common skid mounted with an electric motor and a reciprocating
engine driven gas compressor according to one embodiment of the
invention;
[0016] FIG. 2 is an elevation drawing of the twin drive and shaft
mechanism according to one embodiment of the invention; and
[0017] FIG. 3 is a plain view drawing illustrating the modification
process for existing compressor units.
DETAILED DESCRIPTION OF THE INVENTION
[0018] A dual drive mechanism for a gas compressor is used in the
gathering of natural gas. The dual drive mechanism can be used in
other industries and for other applications in addition to the
natural gas and oil industries. The dual drive mechanism can be
used to drive a single gas compressor or a plurality of gas
compressors, as will be apparent according to the description
below.
[0019] A dual drive mechanism for use in driving a gas compressor
includes a twin shaft drive mechanism. With reference to FIG. 1, it
is shown that the twin drive mechanism effectively transfers the
physical shaft break horsepower of either an engine or an electric
motor to a single shaft drive of a gas compressor. FIG. 1 shows an
engine crankshaft and a compressor crankshaft that share the same
centerline. The engine is equipped with a weighted flywheel (sized
from torsional analysis) and an overrunning clutch assembly. With
continued reference to FIG. 1 and referring to FIG. 2, the engine
drive shaft extends from beyond the overrunning clutch and is
flange bolt connected to the center drive shaft section 1 of the
dual drive mechanism. As illustrated, FIG. 2 shows that the
electric motor is equipped with a steel flex coupling and shaft
flange bolted to the center drive shaft 2 of the dual drive
mechanism. The engine drive shaft 1 extends through the end of the
rear pillar block bearing and is flange bolt connected to a steel
flex coupling. The shaft extends beyond the steel flex coupling and
is flange bolt connected to a weighted flywheel mounted on the gas
compressor crankshaft. The electric motor drive shaft 2 extends
through the end of the rear pillar block and terminates.
[0020] An existing gas compressor unit can be retrofitted with the
dual drive mechanism. For example, an existing unit can be shipped
to the Genergistics facility in Houston, Tex. so that the existing
unit can be retrofitted. Referring to FIG. 3, the existing unit
steel skid is cut in half at a point between the engine and the gas
compressor, and the unit is separated into two corresponding
sections. The dual drive mechanism is then mounted onto a
fabricated steel skid matching the dimensions of the existing unit
steel skid, which is installed and fitted as an added middle
section between the engine section of the steel skid and the
compressor section of the steel skid. The dual drive shafting
mechanism is then connected to the engine and compressor
crankshafts through the dual drive mechanism flex couplings, shafts
and the overrunning clutch assemblies. The electric motor is then
mounted on another steel skid matching the dimensions of the steel
skid of the existing unit, and attached to the newly modified skid
with permanent alignment brackets, such as using steel bolts. Other
attachment means are foreseeable and effective.
[0021] Referring again to FIG. 1 and FIG. 2, a shaft mounted drive
pulley is mounted on drive shaft 1 and on drive shaft 2 of the dual
drive mechanism, and a single drive belt connects the twin drive
shafts together.
[0022] The dual drive mechanism along with the overrunning clutch
allows the compressor to be driven by either the engine or the
electric motor. The mechanism and overrunning clutch allows the
compressor to be started up and driven by the engine. During this
time, the engine is driving the compressor and rotating the
electric motor at the same time. The electric motor is then
energized and electrically excited to exceed the RPMs of the
engine. Once the electric motor exceeds the RPMs of the engine, the
operating overrunning clutch allows the electric motor to begin to
drive the compressor. The engine is then slowed down to a stop, and
the electric motor takes over in running the compressor
continuously.
[0023] If the operator of the compressor wishes to run the
compressor on the engine only, the electric motor is rotated along
with the compressor and the added inertia is designed to enhance
stability. If the operator does not want to run the electric motor,
it can be easily isolated from the drive by removing the shaft
flange bolts, and the removal of the electric motor is possible if
desired.
[0024] What has been described is a specific design of dual drive
mechanism intended for use on gas compressors that offers the above
described features and benefits. The dual drive mechanism can be
integrated into newly designed gas compressors or retrofitted into
existing gas compressors to improve energy efficiency in the
collection of natural gas. Possible modifications on the system as
described are possible and envisioned.
[0025] Having thus described at least one illustrative embodiment
of the invention, various alterations, modifications and
improvements will readily occur to those skilled in the art. Such
alterations, modifications and improvements are intended to be
within the scope and spirit of the invention. Accordingly, the
foregoing description is by way of example only and is not intended
as limiting.
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