Modular compressor unit

The invention relates to improvements in compressor units, and in particular to a modular compressor unit which has separate sections for the compressor, the controls and the air intake. The modular compressor unit comprises three separate adjoining sections, being an intake section, a compression section and a control section. The intake section comprises air intake means which provide an inlet for ambient air to be compressed and for cooling the compressor motor and comprise filters to filter air entering the intake means, noise attenuation means provided in the air intake means, and means for directing air to components in the compression section. The compression section comprises a compressor, a motor arranged to drive all compressor and all components within the unit required to cool compressed air, the motor and to remove heat from the compression section. The control section houses all the control means for operating the compressor unit.

CROSS-REFERENCE TO RELATED APPLICATION

This Application is a Section 371 National Stage Application of International Application No. PCT/GB2007/002751, filed Jul. 19, 2007, published as WO 2008/025938, in English, the content of which is hereby incorporated by reference in its entirety.

The invention relates to improvements in compressor units, and in particular to a modular compressor unit which has separate sections for the compressor, the controls and the air intake.

Oil free compressors typically comprise a single or a multi-stage compressor, a motor and gear box to drive the compressor and controls for operating the compressor. Oil free compressors may also comprise means for directing a cooling flow of air. Hitherto the design of compressor units has been dictated by the components of the units and their operation, and little consideration has been given to the overall unit design. As a result of which, the units are typically not optimised for low noise and are usually unwieldy to handle, transport and service.

It is therefore an object of the present invention to improve the overall design of a compressor unit to overcome these disadvantages.

The invention therefore provides a modular compressor unit comprising three separate adjoining sections, being an intake section, a compression section and a control section; wherein the intake section comprises air intake means which provide an inlet for ambient air to be compressed and for cooling the compressor motor and comprises filters to filter air entering the intake means, noise attenuation means provided in their intake means, and means for directing air to components in the compression section; the compression section comprises a compressor, a motor arranged to drive the compressor and all components within the unit required to cool compressed air, the motor and to remove heat from the compression section; and wherein the control section houses all the control means for operating the compressor unit.

This modular design of the compressor unit is unique for oil free compressor units. No other compressor has a layout that is similar and many compressors are unpackaged.

The modular design provides the following advantages:—

Scaling—the modular design allows for scaling of model sizes up and down the range with ease. The assembly procedure will be the same for all models, but the components will just be a different size.Installation—the modular design enables all of the services (water, mains etc) to be located on the same side of the unit10, something that is very important in the installation of the compressor to reduce installation space.Assembly—the separate sections of the unit can be assembled separately, making the assembly process quicker and easier by building up sub-assemblies and reducing the down time of waiting for components.Cooling—the cooling of the unit provides two advantages. The modular design of the controls section and the compression section enables a single cooling flow to be used. If the unit was not modular, then the cooling of the controls section would have to be done separately, meaning more exhaust outlets and extra intakes in the housing, plus additional fans.Noise—with the housing in place, the noise level of the compressor is significantly reduced for a comparable compressor. The modular design of the present invention is key to this because all of the various noise sources are located in one section, which enables specific measure to be adopted to minimise the noise transmission to the outside. Each individual section has its own noise characteristics that can be dealt with separately. Sandwiching the compression section between the intake and controls sections enables all the high noise items to be enclosed without any direct openings to the outside of the unit, which are required for other reasons in the other sections.

Referring first toFIG. 1, the compressor unit10according to the present invention comprises three distinct sections; the intake section11, the compression section12and the control section13. The use of three distinct sections11,12,13permits the creation of a modular design which lends itself to ease of manufacture, installation, transportation and service. It also makes the design easier to scale up or down as required with the different input power (kW) ratings of the compressor range. The three sections11,12,13of the unit10are wholly encased within a housing comprising a number of removable side, end and roof cover panels/doors attached to a supporting frame.

Referring toFIGS. 2,3and4which illustrate the inside of the compression section12, the compressor (not illustrated) is the main component of the compression section12and comprises a variable high speed motor and two stage compressor combined as a single unit with oil free bearings.

In addition to the compressor, the compression section12of the unit10contains the motor, all ancillary items required to cool the compressed air and remove the heat from the section12itself. The ancillary items are a cooling blower (not shown), a ventilation fan49, coolers16,19, a water circuit and a blowdown circuit.

The air compressed by the 1ststage of the compressor exits the compressor through its discharge (not shown) and flows through the 1ststage cooler inlet manifold17and into the cooler where it is cooled before entering the 2ndstage of the compressor. This cooler will be referred to hereafter as the intercooler16. The air exits the intercooler16through the 2ndstage cooler manifold21and enters the 2ndstage. The compressed air, which is at final delivery pressure, exits the 2ndstage and is directed to an inlet18of the aftercooler19. The air is cooled by the aftercooler19before exiting the unit10via the air discharge20through a non-return valve (NRV) and into the customer's supply. The NRV prevents air from the customer's system from re-entering the circuit when the compressor is stopped or is “offload”.

The intercooler16and aftercooler19are of a different design to the traditional shell and tube coolers usually used with these type of compressors. They are more compact and therefore enable the mounting arrangement of the present invention to be used.

When the compressor stops, or goes “offload”, the residual air that has been compressed by the compressor has to be discharged to atmosphere to release the pressure in the compressor unit10. To enable this, a solenoid valve (not shown) is provided on the delivery pipe that is situated before the NRV. This valve opens on a signal generated by the controls and allows the air to flow through an exhaust silencer into the intake section11. The valve remains open until a signal is generated for it to shut again, i.e. when the compressor goes back “onload”.

The motor is usually cooled by water and/or air and the cooling air is provided by a suitable motor cooling blower and is exhausted, along with any leakage air from the compression process, through two exhaust tubes. These tubes are in line with a motor air exhaust box51. This is a box which is specifically designed to remove any noise generated by the compressor and direct the cooling flow, with minimal losses, to the outside of the compressor unit10. It contains various specially designed baffles and sound attenuation material to do this. Preferably the motor air exhaust box51is a foam lined sheet metal box which has a specific shape to remove line of sight to the exhaust ports and to knock out as much sound energy as possible before the exhaust air exits the housing roof panels63. The baffles have been designed in conjunction with the box so as to not only knock out noise, but also to assist the airflow so that the pressure drops stay within specified limits.

The motor cooling blower is preferably mounted directly to the aftercooler19and directly on to the motor cooling air inlet manifold.

The cooling water enters the compressor unit10through a water intake27and initially has to pass through a solenoid valve (not shown) that is only opened on a signal from the compressor when it starts. The water then flows to a water inlet manifold that distributes the flow to all areas which require cooling water, namely the motor, the intercooler16, the aftercooler19and the variable speed drive. The water flow to these components is controlled by an orifice in the water outlet manifold28that then channels the water back out of the compressor.

The compressor is mounted on the intercooler16via the cooler manifolds17,21. All of the components of the compression section12, except for the ventilation fan, are mounted on a sub-base22that sits on anti-vibration mounts23. The 1ststage inlet pipe24and the 2ndstage discharge pipe are preferably flexible connections, which allow for some movement and to allow for manufacturing tolerances of assemblies.

The arrangement of the compressor mounting is unique because it is mounted between the 1st stage discharge and 2nd stage intake flanges on the intercooler manifolds17,21with the motor suspended in the middle. The flanges allow for thermal expansion, thereby avoiding the need for more bulky and expensive expansion joints.

The mounting of the compressor and the design of the manifolds17,18also means that the compressor is suspended, which provides easy servicing access to the compressor and the coolers16,19. The unit10of the present invention has been specifically designed to provide this advantage.

The frame of the compressor unit housing comprises side rails60, centre rails61and columns64, and provides the structure which supports the weight of the compressor. The horizontal side rails60are located at the top of the housing and are attached to the intake section11and the controls section13at either end. The centre rails61are attached to each side rail60and support the roof panels63.

The centre rails61, which support the roof cover panels63, are also used to jack up the compressor from its mounted position at either end via suitable attachment means. The compressor is mounted directly on to specially designed manifolds, which connect it to the intercooler16. Instead of the traditional shell or tube cooler, the intercooler16has a special design, which facilitates this mounting arrangement. The use of some types of oil free bearings makes it possible for this mounting arrangement to be viable as the system is effectively vibrationless.

Mounting the compressor in this way has the following advantages:Ease of assembly—the assembly only has two connections for mounting. The entire compression section12can therefore be made as a sub-assembly and then put into the unit10.Compact design—the combined design of the 2nd stage cooler manifold and the 2nd stage inlet negate the need for a long length of straight pipe going into the second stage axially.Cost—only a simple gasket or O-ring is required to seal the flange connections, so this is cheaper than a complex coupling. There is no mounting foot for the compressor so no extra framework is required for mounting the motor. As the compressor is part of the compression section12, the whole assembly is isolated, removing the cost for separate isolators for the compressor.Servicing—as the compressor is only mounted via the first stage discharge and second stage inlet flanges to the intercooler manifolds17,21, this enables the discharge pipes of the compressor to be removed to give access to the rotors and also allows the coolers16,19to be removed for cleaning. No prior art compressor is supported in this way to provide for ease of servicing. One person can jack up the compressor, and no heavy lifting equipment is needed to suspend the compressor. The components can be inspected regularly if required, and components can be changed easily. This means that the unit10can be located in much smaller areas than the prior art compressors.

This is a unique arrangement for compressors. In prior art arrangements having an air end/motor unit mounted on top of a cooler, this requires flexible connections on the 1st stage discharge and the 2nd stage intake and the motor is mounted via feet on top of the coolers.

Each of the above features contribute to the compact nature of the inventive arrangement.

The intake section11provides the means for the compressor to draw air into the unit10. The air initially passes through a coarse filter mesh30on the outside of an intake duct31, as shown inFIGS. 3 and 5. The intake duct31has a noise attenuation baffle32which is specifically designed to remove the compressor intake noise without reducing the airflow or increasing the pressure drop. The air is drawn through the intake duct31and into the intake chamber33where the air is then drawn through two air intake filters34. The air intake filters34are attached to the underside of a plenum chamber35with plenty of surrounding space to aid servicing operations. The 1ststage intake to the compressor is attached to an intake bellmouth36via a rubber connector and the bellmouth36is attached inside the plenum chamber35. The air flows into the 1ststage through the bellmouth36, which provides uniform airflow into the 1st stage of the compressor.

Cooling air for the compressor motor is also drawn through the coarse filter mesh30before passing through a gap in the intake duct31, through a secondary filter37and into the cooling air blower housed in the compression section12.

The controls section13contains all of the electrical components required to control the compressor14. As can be seen inFIG. 6this section13is sub-divided into three sub-sections, an incoming power supply section40, a variable speed drive section41and an auxiliary component section42.

As a safety requirement, incoming mains electricity passes through an isolating switch43in the first sub-section40before it is distributed to the rest of the electrical circuits. It then passes through an EMC (Electromagnetic Compatability) filter44to a line reactor and into the variable speed drive45, which is housed in the second sub-section41. The supply for the auxiliary components is taken off in between the EMC filter44and the line reactor to power the control transformer, bearing controller, contactors and user interface in the third sub-section42.

The auxiliary components section42and the incoming power supply section40have openable doors46(seeFIG. 1) but the variable speed drive section41is accessed though a lift off end panel47. This is to help control EMC emissions.

The controls section13is cooled by air that is drawn through two external filters48that are situated in the top of the two hinged access doors46of section13. The air is directed through the section13by finger protection guards, which have been designed to also aid with noise reduction. The control section13has various openings that allow the air to flow between the incoming power supply section40, variable speed drive section41, and auxiliary component section42to cool the components as necessary. These openings are different sizes to direct the correct amount of air to the various parts of the control section13and then through openings46into the compression section12.

A ventilation fan49which is situated at the opposite end of the unit10(seeFIG. 4) draws the air into the unit10through the external filters48, through the controls section13, into the compression section12before exiting the unit20via duct50(seeFIG. 1), which is situated above the intake plenum chamber35. This air is directed by the exhaust box51which acts as a cooling/noise attenuation baffle to draw air over the hot surfaces in the compression section12and therefore keep the temperature within the unit10at an acceptable level.

Baffles are also provided in the controls section12, which have four functions;1) to attenuate any noise that may come through the external filters48;2) to assist the unit10cooling by directing the air flow over the correct components in the section13;3) to help with EMC screening; and4) to protect the user from electrical shock and comply with electrical safety codes.
Remote Monitoring

The unit10may be provided with a remote monitoring facility. This enables the service schedules to be dynamic so that components are only replaced when they need to be, thus helping with environmental issues and product lifecycle costs. It also enables remote fault diagnosis that reduces down time of the compressor.

Set service schedules for consumable elements of the compressor can be eliminated, as all temperatures and pressures can be monitored remotely. Using this facility, it is possible to determine when components need changing or cleaning. A controller constantly monitors certain parameters and files of data can be extracted remotely. This data can be analysed to determine when to change filters or clean coolers.

The advantages of remote monitoring are as follows:For the compressor—if the unit10is operating in a dirty environment the filters may need to be changed on a more regular basis. This prevent the efficiency of the machine from dropping below specified levels and prolongs the compression life.For the customer—if the unit10is used in a clean environment, the consumable items are only changed as and when required, thereby reducing service costs and downtime of the compressor for cleaning.For the environment—items are only changed as and when they need to be and chemicals for cleaning the coolers16,19are only used when necessary.
Transportation

The design of the sub-base22and the design of the mounting arrangement means that the only component that needs to be supported during transportation is the compressor. The anti-vibration mounts23used for the sub-base22do not need any attachments to isolate movement during transportation, which makes transportation significantly easier.