Note: Descriptions are shown in the official language in which they were submitted.
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NATURAL GAS BOOSTER COMPRESSOR SYSTEM
[0001] BACKGROUND OF THE INVENTION
[0002] Natural gas booster compressor systems are used to lower the pressure
at the
wellhead of a natural gas well to below the pressure in the pipeline it is
connected to. This
results in an increased rate of natural gas production by providing a higher
driving
pressure between the reservoir and wellhead with the result of increased flow.
[0003] There are two common compression technologies used to compress natural
gas, namely reciprocating compressor technologies which are most suited to
pressures
over 300-350 psi and oil flooded screw technologies that are most suited to
pressures less
than 300-350 psi.
[0004] The main components of a natural gas screw compressor package are:
a) Inlet Valve - Controls inlet flow and/or pressure and it can be a simple
manual
operated valve for on off and throttling (to control pressure) or a
sophisticated
control valve that automatically regulates pressure to the inlet of the
compressor.
b) Inlet Scrubber - A pressure vessel that is equipped and configured in such
a
way that it will remove liquids from the inlet gas stream. The liquids are
normally condensates (hydrocarbons that are liquid at the pressures and
temperatures inside the vessel) and water that are co-produced with the gas -
usually in relatively small volumes.
c) Oil Flooded Screw Compressor - A rotary device that is used to compress air
or process gases. Oil is introduced at the inlet of the device and moves
through
it with the gas that is being compressed. The oil absorbs the heat of
compression, lubricates the rotating elements and seals the two screws against
themselves and the outer housing
d) Oil Separation Scrubber - A device similar to the inlet scrubber that
removes
the oil from the gas stream so it can be recycled.
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e) Oil Coalescing Filter - A device that removes the oil that the oil
separation
scrubber does not remove and delivers a gas stream with oil carry over in the
order of 5 PPM
f) Oil Cooler - A heat exchanger that can be a liquid to liquid but in most
cases,
including this one, is an air to liquid type which cools the oil coming out of
the
oil scrubber and coalescing filter - thus the heat of compression.
g) Gas Cooler - Cools the gas before it enters the pipeline.
h) Recycle Valves - Allows a portion of the discharge gas to recirculate into
the
inlet for capacity control.
i) Engine - Provides power for compression, cooling fans and radiator fans.
j) Instrumentation/ Fault Annunciator - Monitoring of different performance
parameters and shutdown if out of condition event occurs.
k) Enclosure - Protects components from the elements.
[0005] Existing Technology
[0006] There are a number of manufacturers producing a number of different
configurations of gas compressors. In the most common configuration the
components are
assembled on a large skid and a self-framing building is installed around this
to protect it
from the weather and to make maintenance easy in the wintertime. In this
configuration
the main elements - coolers, scrubbers and engine are generally separated and
connected
by plumbing running overhead or under the floor so operators and repair people
can walk
between them for inspection and servicing. Some manufacturers mount these on a
trailer.
[0007] Some manufacturers build compact units that must be accessed through
external doors. To service process valves in these units the enclosure must be
removed or
the service personnel must work in a confined area thus increasing the time to
service and
repair.
[0008] Most manufacturers have the engine and compressor mounted in the same
enclosure as the compressor although one manufacturer has packaged a
compressor where
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the engine and compressor/process equipment are separated by a wall with a
driveshaft
running through the wall. The chief benefit of this is that the majority of
the electrical
equipment resides in the engine compartment that does not have a potentially
explosive
atmosphere and hence can be "General Purpose" equipment rather than "Explosion
Proof'
which is substantially more expensive. In this particular compressor system,
the following
design difficulties are noted:
a) The scrubber vessels are mounted at right angles to the driveshaft placing
the
process valves in a place that is not readily accessible from the outside.
b) The compressor is belt driven with the drive pulley shaft mounted to pillow
blocks mounted to the floor which makes it difficult to maintain alignment and
requires that the drive forces must be resisted by various mounts.
c) The fan is driven off the same shaft as the compressor placing the cooler
at the
engine end of the enclosure necessitating ducting to get cooling air to it.
[0009] Other designs of the prior art show that most manufacturers direct
drive the
compressor whereas one manufacturer belt drives the compressor and uses an
idler pulley
as a clutch.
[00010] SUMMARY OF THE INVENTION
[00011] It is an object of the present invention to obviate or mitigate at
least one
disadvantage of previous natural gas booster compressor systems.
[00012] In a first aspect, the present invention provides a natural gas
compressor system
comprising:
a power module and a compressor module in separate compartments and
connected via a drive shaft;
the power module including an engine in operative connection to the drive
shaft;
the compressor module including a compressor in operative connection to an
inlet scrubber and an oil separator scrubber each having a long axis; and
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wherein the inlet scrubber and oil separator scrubber are configured
horizontally within the compressor module and the long axes of the scrubbers
are parallel to the drive shaft.
[00013] In an embodiment, the present invention provides a natural gas
compressor
system wherein the compressor includes a compressor discharge mounted directly
to an
inlet flange on the oil separator scrubber.
[00014] In an embodiment, the present invention provides a natural gas
compressor
system further comprising an oil and gas cooling system mounted at the
opposite end of
the scrubber vessels with respect to the compressor and wherein the axis of
the oil and gas
cooling drive system is parallel to the drive shaft.
[00015] In an embodiment, the present invention provides a natural gas
compressor
system wherein the compressor is operatively connected to the drive shaft
through a belt
and drive pulley system mounted to a shaft in a bearing housing mounted in
slots on a plate
mounted to the face of the compressor.
[00016] In an embodiment, the present invention provides a natural gas
compressor
system wherein the compressor is operatively connected to the drive shaft
through a belt
and drive pulley system mounted to a shaft in a bearing housing mounted in
slots on a plate
mounted to the face of the compressor and wherein the belt and drive pulley
system is
tightened by a fluid cylinder.
[00017] In an embodiment, the present invention provides a natural gas
compressor
system wherein the compressor is operatively connected to the drive shaft
through a belt
and drive pulley system mounted to a shaft in a bearing housing mounted in
slots on a plate
mounted to the face of the compressor wherein the belt and drive pulley system
is
tightened by a fluid cylinder and wherein the oil and gas cooling system is
driven by a
shaft connected by way of a flexible coupling at the end of the shaft in the
bearing housing
at opposite to the input end and having the opposite end mounted in a self
aligning bearing.
[00018] In an embodiment, the present invention provides a natural gas
compressor
system wherein cooling air for the power module and compressor module enter
each
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compartment at opposite ends and discharge through louvers adjacent a
separating wall
between each module.
[00019] BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described with reference to the drawings wherein:
Fig. 1 a is a top view of natural gas booster compressor in accordance with
the invention;
Fig. lb is a side view of natural gas booster compressor in accordance with
the invention;
Fig. 2a is a top view of a natural gas booster compressor drive system in
accordance with
the invention;
Fig. 2b is an end view of a natural gas booster compressor drive system in
accordance
with the invention;
Fig. 2c is a side view of a natural gas booster compressor drive system in
accordance with
the invention;
Fig. 3a is a top view of a compression module showing process plumbing and
valves in
accordance with one embodiment of the invention;
Fig. 3b is a side view of a compression module showing process plumbing and
valves in
accordance with one embodiment of the invention;
Fig. 4a is a photograph of a prior art natural gas booster compressor system
with its
enclosure in place; and
Fig. 4b is a photograph of a prior art natural gas booster compressor system
with its
enclosure removed.
[00020] DESCRIPTION OF THE INVENTION
[00021] With reference to Figures 1-3, the invention provides a design
configuration of
the major components a compressor system that overcomes the problems of the
prior art.
The system utilizes standard process equipment in a novel arrangement or
configuration as
compared to a typical prior art system shown in Figure 4.
[00022] Overview
[00023] The system 10 is divided into two modules, a compression module 12 and
a
power module 14, which are mounted in respective enclosures 12a, 14a with a
wall 16
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separating them and a drive shaft 18 penetrating the wall 16. The drive shaft
18 transmits
power from the power module 14 to the compression module 12.
[00024] Each module is assembled on a separate sub-frame 12b, 14b with all
plumbing
and wiring complete. That is, the power module 14 includes all components
necessary for
power generation including an engine 14c, radiator, wiring, extended run oil
and glycol
reservoirs, muffler and wiring harness as are known. The sub frames are then
mounted on
a trailer (or skid 26) with a driveline connecting them. The outer enclosure,
which
contains control panels, is mounted by way of fasteners to the trailer and the
modules are
connected to the control panel by way of appropriate electrical plugs
[00025] The compression module 12 includes an oil separator scrubber vessel
12c and
an inlet scrubber vessel 12d (collectively, "scrubber vessels") in a
horizontal configuration
and are preferably approximately the same size with their long axis parallel
to the drive
shaft 18.
[00026] The compressor 12e is mounted on the oil separator scrubber vessel 12c
with a
compressor input shaft being parallel to the long axis of the scrubber
vessels.
[00027] The compressor discharge is mounted directly to the oil separator
scrubber
vessel 12c by way of a discharge port 12f and discharges directly into the oil
separator
scrubber vessel 12c.
[00028] Process plumbing runs down the sides of the scrubber vessels with
interconnections on top of each scrubber vessel.
[00029] Process valves are all located on the sides of the scrubber vessels.
[00030] An oil and gas cooling system 12g is mounted crosswise at the end of
the
scrubber vessels with the face of the cooler facing outwards for easy access
to cooling air
at the rear end of the system.
[00031] The compressor is belt driven as shown in Figure 2 (Belt not shown for
clarity).
Power is delivered via drive shaft 18 driving a drive pulley 20a mounted to a
clutch belt
tightner system 20 and is transmitted by said belt to a driven pulley on the
compressor
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input shaft, the driven pulley being, for example, a largest driven pulley 20b
or a smallest
driven pulley 20g.
[00032] The drive shaft has a flexible coupling 22 on each end that allows the
motion of
the clutch idler system while power is being transmitted.
[00033] The flexible couplings 22 are preferably rubber couplings, which in
addition to
compensating for angular misalignment also act as a torsional spring providing
protection
of the screw from torsional vibrations.
[00034] The clutch belt tightener system 20 consists of a pulley shaft 20c,
which the
drive pulley 20a is affixed to, mounted in a set of bearings that are in turn
mounted in a
bearing housing 20d. The bearing housing 20d is mounted to a plate attached to
the
compressor-mounting flange in slotted holes or slides 20e that allow it to
move. The
movement allows the center distance between the drive pulley 20a and a driven
pulley to
change thus providing for clutching, belt tensioning, and accommodation of
belt stretch or
different center distances that are needed for different drive ratios. Use of
the plate also
ensures belt alignment and contains all the forces between it and the
compressor.
[00035] A double acting air cylinder 20f acts on the bearing housing 20d and
provides
force to clutch and make up for different center distances and provide
constant belt tension.
[00036] The double acting air cylinder 20f is connected to an air source by
way of a
regulator and directional control valve which provide constant force for
tightening and
directional movement for clutching.
[00037] The beneficial aspect of this is that changing the driven pulley and
the belt can
accommodate a number of different speed ratios. The two flexible joints allow
enough
misalignment of the drive shaft 18 between the engine 14c and drive pulley 20a
to
accommodate the following simultaneously: (1) The differences in center
distance, which
occur when different belt pulley combinations are used; (2) The increase in
center distance,
which occurs over time as a result of belt stretch; and, (3) The difference in
center distance
required to clutch the driven load (compressor).
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[00038] The oil and gas cooling system 12g is driven by a cooler drive shaft
12h
connected by way of a flexible coupling 22 to the end of the drive shaft 18 of
the clutch
arrangement and mounted between the scrubber vessels with a self aligning
bearing at the
opposite end which has a pulley on it providing power through a belt to a
pulley mounted
on a bearing arrangement mounted to the oil and gas cooling system 12g. The
driven end
of the cooler drive shaft 12h is attached to the back end of the drive pulley
shaft 20c and
consequently moves with it. There is a flexible joint between the drive pulley
shaft 20c
and the fan drive and a self-aligning bearing at the other end of the shaft
that
accommodates this motion. The drive pulley for the fan drive is located
adjacent to the
self-aligning bearing and slight differences in center distance between the
drive and driven
pulley's is compensated by a spring-loaded idler pulley.
[00039] The compressor is mounted in such a way that it is easy to change the
rear plate
that changes the compression ratio of the compressor. This allows the
compression ratio to
be optimized for the inlet and outlet pressure desired for the specific site.
[00040] Discussion
[00041] This configuration can be used to advantage for either trailer or
building
installations.
[00042] The basic configuration in which parallel scrubber vessels with a
compressor
mounted to one, the center line of the vessels parallel to the engine drive
line, the drive
coming into a pulley mounted on bearings mounted to plate attached to
compressor with a
driveshaft out the back driving fan on cooler mounted crossways at the end
provides
numerous advantages in the maintenance and operation of the system.
[00043] These include but are not limited to: a) as the compressor is belt
driven, it is
easy to change drive ratios b) the clutching and belt tensioning mechanism
enables
effective power transmission c) the system provides a favorable cost /
performance
solution in a highly portable package that is easy to maintain
[00044] Furthermore, the separation of the compressor into two compact
(compared to
existing practice) modules each built up on a sub frame allows them to be
assembled much
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faster than a conventional arrangement because the assembler can easily reach
all areas
with out moving, in addition the compact nature means less piping is used. In
a typical
compressor, instead of components being separated by inches they are separated
by feet
requiring more time to move between parts of the machine to assemble parts and
the use of
2 people to mount the long piping runs.
[00045] The modular arrangement provides significant maintenance and overhaul
benefits. The engine is the most maintenance and overhaul intense component in
the
machine and over the life of the machine will be removed for service/overhaul
several
times. In a conventional configuration it takes several hours to remove and
replace the
engine as all the accessories and connections must be removed and reattached
to the
replacement engine, In the case of this invention the engine module can be
replaced in a
few minutes as the only connections to the rest of the compressor are
driveshaft, battery
cables a wiring plug and 4 bolts holding the sub assembly to the trailer/skid.
This allows
the compressor to go back into service generating revenue for the user while
the engine can
be repaired over a longer period of time in a proper maint facility (rather
than in the field
where most engines are replaced) with a complete supply of parts and tools
[00046] The configuration is much lighter and smaller than conventional
packages that
make it easier to transport for installation and maintenance.
[00047] It is easier to assemble as all the work can be done on a stand with
easy access
and then the module can be mounted on a trailer or in a building.
[00048] Because most of the plumbing and process valves are mounted on the
sides of
the scrubbers it is easy to access through inspection doors when mounted on a
trailer. All
the components with moving parts can be replaced while standing outside the
compressor.
[00049] Because the compressor is mounted directly on the scrubber it is less
expensive
and has less opportunity for leaks.
[00050] Because the cooler is at the opposite end of the package from the
drive it has
access to an outside wall. This is more economical than ducting air and brings
warm air
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(having gone through the cooler) into the enclosure to keep the rest of the
components
warm.
[00051] The belt drive arrangement makes it possible to clutch and accommodate
different drive ratios without the use of an idler pulley while at the same
time providing
isolation from torsional vibrations and a constant belt tension. The constant
belt tension
and the lack of an idler pulley results in much longer belt and bearing life.
Typically, belts
fail from burn-out due to too low belt tension, which induces slippage or
fatigue from
bending (the idler pulley makes the belt undergo one extra bend per
revolution.
