EP2865424A1

EP2865424A1 - Air compressor system

Info

Publication number: EP2865424A1
Application number: EP20140190291
Authority: EP
Inventors: Nitzan Gonen; Pat McGann
Original assignee: Factair Ltd; Sabre Safety Ltd
Current assignee: Factair Ltd; Sabre Safety Ltd
Priority date: 2013-10-28
Filing date: 2014-10-24
Publication date: 2015-04-29
Also published as: GB2522399A; GB201319019D0; GB2522399A8

Abstract

This invention relates to air intake units for air compressors and to air compressor assemblies for supplying breathable air. An air intake unit for an air compressor comprises an air chamber having an inlet and an outlet, the outlet being adapted for fluid connection to an air intake of an air compressor; a sensor located at the inlet of the air chamber, the sensor configured to detect the presence of unwanted fluid in an inlet air stream, the sensor having a T90 response time; and means for maintaining a positive pressure within the air chamber, wherein the air chamber is configured such that the time taken for air to flow from the inlet of the air chamber to the outlet of the air chamber is greater than the T90 response time of the sensor.

Description

BACKGROUND

a. Field of the Invention

This invention relates to air intake units for air compressors and to air compressor assemblies for supplying breathable air.

b. Related Art

It is known to provide a source of safe breathable air to personnel working in dangerous or confined environments, for example, in petrochemical environments. This air is supplied, via an air compressor and airlines, to suitable breathing apparatus such as facemasks worn by the user of the equipment.
In certain hazardous environments there is the potential for harmful gases to be drawn into the intake of the air compressor. These harmful gases may then enter the air stream that is supplied to the user of the breathing apparatus.
In some prior art systems it is known to position a gas sensor at the inlet of the air compressor to detect the presence of any harmful gases. If the sensor detects that the level of harmful gases has exceeded a predetermined threshold, the system sounds an alarm and switches to a reserve supply of clean air, thereby providing the user with a limited volume of breathable air to allow him time to evacuate the area.
The problem with prior art systems is that the gas sensor can take a relatively long time to respond to the presence of harmful gases. A suitable toxic gas sensor will typically have a T90 time (that is the time taken for the gas sensor to reach 90% of its final reading) of around 30 seconds. There is a risk, therefore, that, in this 30 second period before the sensor responds, air containing harmful levels of toxic gas may be drawn through the air compressor and supplied to the breathing apparatus of the user.
It is an object of the present invention to overcome the above mentioned disadvantages of prior art systems.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided an air intake unit for an air compressor, the air intake unit comprising:

an air chamber having an inlet and an outlet, the outlet being adapted for fluid connection to an air intake of an air compressor;
a sensor located in the inlet of the air chamber, the sensor configured to detect the presence of unwanted fluid in an inlet air stream, the sensor having a T90 response time; and
means for maintaining the pressure within the air chamber above atmospheric pressure,

Typically the unwanted fluids are flammable and/or toxic gases. The air intake unit, therefore, provides an intake protection unit that delays the entry of air into a compressor after that air has passed suitable gas sensors. Accordingly, the air intake unit can be used to prevent toxic gases entering the compressor and being supplied to a user's breathing equipment if harmful levels of toxic gases are detected. In addition, the intake unit can prevent flammable gases being drawn into the compressor and potentially igniting in the compressor due to the heat and compression process of the air compressor.
In preferred embodiments the air intake unit comprises at least two gas sensors. These sensors are selected to detect different chemical components of the air entering the air chamber. In embodiments comprising two or more gas sensors, the air chamber is configured such that the time taken for air to flow from the inlet of the air chamber to the outlet of the air chamber is greater than the longest of the T90 response times of each of the sensors.
In preferred embodiments the air intake unit comprises an air mover located in the inlet of the air chamber, the air mover being arranged to draw air into the air chamber. Preferably the air mover is driven by compressed air. The air mover is preferably located downstream of the gas sensors, between the gas sensors and the air chamber.
In preferred embodiments the inlet of the air chamber comprises a conduit through which the air flows before entering the air chamber. The conduit may include a restriction located downstream of the gas sensors, between the gas sensors and the air chamber. In embodiments comprising an air mover in the intake, the restriction is preferably located downstream of the air mover, between the air mover and the air chamber.
The air chamber preferably includes one or more baffles configured so as to direct the flow of air through the air chamber. In other embodiments the air chamber comprises an elongate conduit through which the air flows from the inlet of the air chamber to the outlet.
In some embodiments the air intake unit comprises a pressure sensor located at the outlet of the air chamber.
In preferred embodiments the air intake unit further comprises means to automatically shut down the compressor in the event that the sensor detects the presence of unwanted fluid in the inlet air stream.
The air intake unit preferably comprises an alarm, which may be an audible and/or visual alarm that indicates to the user when at least one of the following events has occurred: (i) detection of harmful gas, (ii) mechanical or electrical malfunction, and (iii) a loss of positive pressure within the air chamber.
According to a second aspect of the present invention there is provided an air compressor assembly comprising:

an air compressor; and
an air intake unit according to the first aspect of the present invention, the outlet of the air chamber of the air intake unit being fluidly connected to an intake of the air compressor.

In embodiments in which the air intake unit comprises means to automatically shut down the compressor in the event that the sensor detects the presence of unwanted fluid in the inlet air stream, the assembly will typically further comprise a vessel housing a reserve source of compressed air. In this way breathable air can be continuously supplied to a user even if the compressor is shut down.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only and with reference to the accompanying drawings, in which:

Figure 1 is a schematic illustration of the arrangement of an air intake unit of the present invention; and
Figure 2 is a perspective view of an air intake unit according to a preferred embodiment of the present invention, with the pipes and/or ducts between components of the unit removed for clarity.

DETAILED DESCRIPTION

Figure 1 illustrates an air intake unit 10 for an air compressor according to the present invention. The air intake unit 10 is designed, in particular, for use with an air compressor supplying breathable air to a user's respiratory equipment, such as a face mask. The air intake unit 10 may also be used as a protection system for an air compressor, preventing potentially ignitable and/or explosive gases entering the air compressor.
The air intake unit and compressor of the present invention is particularly suited for use in potentially harmful environments, such as offshore and petrochemical environments, in which the air may include flammable or toxic gases.
The air intake unit 10 comprises an air chamber or air plenum 12 having an air inlet aperture 14 and an air outlet aperture 16. In this example the air chamber 12 is substantially cuboidal having opposing first and second end walls 18, 20, and two pairs of opposing side walls extending between the first and second end walls (only two of which 22, 24 are shown in Figure 1), thereby defining an internal volume of the air chamber 12. The air inlet aperture 14 is provided in the first end wall 18 and the air outlet aperture 16 is provided in the second end wall 20.
The air outlet aperture 16 is fluidly connected, by a suitable outlet conduit 26, to an inlet of an air compressor (not shown). The air compressor may be of any suitable type for supplying breathable air. In preferred embodiments the compressor is an air cooled rotary vane compressor able to supply air at 450 to 600 litres per minute at a pressure of 7 bar (700 kPa).
An air inlet conduit or duct 28 is connected to the inlet aperture 14 of the air chamber 12.
Two gas sensors 34 are positioned in the inlet conduit 28 and are arranged to detect the presence of flammable or toxic gases in an inlet air stream flowing through the inlet conduit 28. In preferred embodiments one of the gas sensors is a sensor for detecting methane and the other one of the gas sensors is a sensor for detecting hydrogen sulphide. It will be appreciated that in some embodiments there may be only one gas sensor located in the inlet conduit, while in other embodiments there may be more than two sensors, for example up to four sensors, located in the inlet conduit. Additional sensors may be selected to detect other contaminants in the inlet air stream. The required number of sensors will, in general, depend on the type of environment in which the unit is being used.
Each of the gas sensors 34 has a T90 response time, which is the time taken for the gas sensor to reach 90% of its final reading. Typically this T90 time will be around 30 seconds.
Also located within the inlet conduit 28 is an air mover or air amplifier 36. The air amplifier 36 is configured to draw air into the air chamber 12 through the inlet conduit 28. In preferred embodiments the air amplifier 36 is driven by compressed air and utilises the coanda effect. In these embodiments the air amplifier 36 comprises a compressed air inlet 38 that is fluidly connected to an annular chamber 40 that surrounds the inlet duct. The compressed air enters the interior of the inlet conduit 28 over a 'coanda' profile that causes a low pressure region within the inlet conduit 28. This low pressure region induces an amplified air flow into the inlet conduit 28 from the surroundings, and produces a high volume, low pressure output air stream that enters the air chamber 12 through the air inlet aperture 14. In preferred embodiments the relatively small volume of compressed air needed by the air amplifier 36 is supplied by the compressor connected to the air intake unit 10. In other embodiments the compressed air may be obtained from any other suitable source.
Air amplifiers driven by compressed air have the advantage that they have no moving parts. In other embodiments, however, other types of air movers or air amplifiers may be used such as those comprising blades or other moving parts.
In addition to helping to draw air into the inlet conduit 28 of the unit 10, the air amplifier 36 also increases the air pressure within the air chamber 12 so that this is above atmospheric pressure. This positive pressure (indicated by the shading region in Figure 1) within the air chamber 12 ensures that there is no ingress of air from the surroundings directly into the air chamber 12 if a leak forms. The air amplifier 36 is preferably located downstream of the gas detectors 34 and as close to the gas detectors 34 as possible. This guarantees that all of the air entering the air chamber 12 has passed the gas detectors 34 in the inlet conduit 28 and that there is no possibility of contaminated air by-passing the gas detectors 34 and reaching the intake of the compressor.
The air chamber 12 further comprises a series of baffles 42 arranged to deflect the flow of air through the air chamber 12, as indicated by the arrow in Figure 1. In this example the baffles 42 extend from two opposing side walls 22, 24 of the air chamber 12 and form a zig-zag or substantially sinusoidal flow path for the air between the inlet and outlet apertures 14, 16 of the air chamber 12. The baffles 42, therefore, lengthen the flow path and the transit time of the air flowing through the air chamber 12. The number and arrangement of the baffles 42 is designed such that the time taken for the air to flow through the air chamber 12 is greater than the longest T90 time of the gas sensors 34 in the inlet conduit 28. Typically, this results in the time taken for the air to flow through the air chamber 12 being more than 30 seconds.
In other embodiments different constructions of the air chamber 12 may be used. For example, the air chamber may comprise an elongate pipe that extends from the air inlet 14 to the air outlet 16 and provides a suitable tortuous air flow path.
A pressure sensor 44 is located in the outlet conduit 26 of the air intake unit 10. This pressure sensor 44 monitors the pressure of the outlet air stream and, therefore, the air pressure within the air chamber 12, and is configured to detect if there is a loss of positive pressure within the air chamber 12.
In use, air is drawn into the inlet conduit 28 and past the inlet gas sensors 34 by the air mover 36. The air then enters the air chamber 12 of the air intake unit 10. The tortuous flow path through the air chamber 12 provides a suitable delay, between the air entering and exiting the air chamber 12, such that the gas sensors 34 have time to react to the presence of harmful gases or contaminants in the air stream before the air reaches the outlet 16 of the air chamber 12.
If one or more of the gas detectors 34 detects the presence of a harmful gas the compressor is automatically shut down and an audible alarm is activated to alert the user. Preferably the audible alarm is pneumatically operated. Upon shut down of the compressor, a high-pressure reserve source of air (not shown) is used to continue to supply breathing air to the user.
If the gas detectors 34 do not detect the presence of any harmful gases, the air flows through the outlet conduit 26 and into the air intake of the compressor.
Preferably the air intake unit 10 is also configured to trigger an audible and/or visual alarm and, in some embodiments to also shut down the compressor, in the event of a mechanical or electrical malfunction, or in the event that a loss of pressure within the air chamber 12 is detected.
Figure 2 illustrates a preferred embodiment of an air compressor assembly 50 including the air intake unit 10 of the present invention. Figure 2 shows all of the primary components of the air intake unit 10 with the pipes or conduits forming fluid connections between the components removed for clarity.
In this embodiment the air intake unit 10 and compressor 52 are mounted within a supporting frame 54. A base 56 of the frame 54 comprises channels 58 sized and positioned to receive the forks of a forklift arm or truck, to enable the air compressor assembly 50 to be manoeuvred.
In use, air is drawn into the air compressor assembly 50 through an air intake 60 and first passes through an air filter 62. The filter 62 filters the air so that it is of a suitable purification to protect the gas sensors and the air compressor. Subsequent filtration downstream of the air compressor purifies the air to a standard in excess of that required by British Standard EN12021.
After passing through the filter 62, the air then enters a first portion 30 of the inlet conduit which is in the form of a manifold 30 containing the gas detectors 34. In this example one of the gas detectors is a methane gas detector set to trigger at 10% of the lower explosive limit (LEL) (LEL for methane is 5% v/v). Another of the gas detectors is a hydrogen sulphide gas detector set to trigger at 10ppm (parts per million). The T90 response time of each of the gas sensors is approximately 30 seconds.
An air amplifier (not shown in Figure 2) is mounted at an end of the manifold 30 and draws air through the manifold 30 and into the air chamber 12. Baffles (not shown in Figure 2) within the air chamber 12 delay the passage of air such that it takes the air stream more than 30 seconds to pass through the air chamber 12. Once the air has passed through the air chamber 12 it flows through the outlet conduit to the intake of the air compressor 52. The compressor 52 is preferably an air cooled rotary vane compressor directly driven at either 1450 rpm (50 Hz) or 1760 rpm (60 Hz).
The air compressor assembly 50 further comprises a vessel containing air at high-pressure (not shown). This vessel provides a reserve source of compressed air should the compressor be shut down in the event of the detection of harmful gases by the air intake unit 10, allowing breathable air to be continuously supplied to the user of the assembly.
The air intake unit 10 of the present invention provides a means for detecting the presence of harmful gases within a stream of intake air and a means for delaying the passage of the air to a compressor, such that the air stream can be prevented from entering the compressor if harmful gases are detected.
The present invention, therefore, provides an improved air intake unit for air compressors that may be used to prevent the entry of harmful levels of toxic and/or potentially ignitable or explosive gases into the compressor. The present invention also provides an improved air compressor assembly for providing breathable air.

Claims

An air intake unit for an air compressor, the air intake unit comprising:
- an air chamber having an inlet and an outlet, the outlet being adapted for fluid connection to an air intake of an air compressor;

- a sensor located at the inlet of the air chamber, the sensor configured to detect the presence of unwanted fluid in an inlet air stream, the sensor having a T90 response time; and

- means for maintaining a positive pressure within the air chamber,
wherein the air chamber is configured such that the time taken for air to flow from the inlet of the air chamber to the outlet of the air chamber is greater than the T90 response time of the sensor.
An air intake unit as claimed in Claim 1, wherein the unwanted fluid comprises flammable and/or toxic gases.
An air intake unit as claimed in Claim 1 or Claim 2, wherein the air intake unit comprises at least two gas sensors.
An air intake unit as claimed in any preceding claim, wherein the air intake unit comprises two or more gas sensors and the air chamber is configured such that the time taken for air to flow from the inlet of the air chamber to the outlet of the air chamber is greater than the longest of the T90 response times of each of the sensors.
An air intake unit as claimed in any preceding claim, wherein the air intake unit comprises an air mover located at the inlet of the air chamber, the air mover being arranged to draw air into the air chamber.
An air intake unit as claimed in Claim 5, wherein the air mover is driven by compressed air.
An air intake unit as claimed in Claim 5 or Claim 6, wherein the air mover is located downstream of the gas sensors, between the gas sensors and the air chamber.
An air intake unit as claimed in any preceding claim, wherein the air chamber includes one or more baffles.
An air intake unit as claimed in any preceding claim, wherein the air intake unit further comprises a pressure sensor located at the outlet of the air chamber.
An air intake unit as claimed in any preceding claim, wherein the air intake unit further comprises means to automatically shut down the compressor in the event that the sensor detects the presence of unwanted fluid in the inlet air stream.
An air intake unit as claimed in any preceding claim, wherein the air intake unit further comprises an alarm configured to alert the user when an unwanted fluid is detected in the inlet air stream and/or a loss of positive pressure within the air chamber occurs.
An air compressor assembly comprising:
- an air compressor; and

- an air intake unit as claimed in any one of Claims 1 to 10, the outlet of the air chamber of the air intake unit being fluidly connected to an intake of the air compressor.
An air compressor assembly as claimed in Claim 12, wherein the air intake unit comprises means to automatically shut down the compressor in the event that the sensor detects the presence of unwanted fluid in the inlet air stream, and the assembly further comprises a vessel housing a reserve source of compressed air.