GB2331254A

GB2331254A - Nitrogen generator

Info

Publication number: GB2331254A
Application number: GB9901006A
Authority: GB
Inventors: Graham Sinclair; Stuart Mcculloch
Original assignee: PRODUCTS OF TECHNOLOGY Ltd
Current assignee: PRODUCTS OF TECHNOLOGY Ltd
Priority date: 1999-01-19
Filing date: 1999-01-19
Publication date: 1999-05-19
Also published as: GB9901006D0; GB2331254A9

Abstract

Nitrogen generating apparatus 50 comprises a modular arrangement of tank cabinets 102 and control cabinets 100. The apparatus typically is controlled by a programmable logic controller (PLC) connected to transducers 122,124 and valves 104,112. The PLC enables the nitrogen production process to be monitored throughout the generator and switches the nitrogen production process off and on, depending on when nitrogen is required. Generating apparatus comprising pressure monitoring means for an air supply and/or the nitrogen product is further disclosed. The apparatus generally operates on compressed air 103 and the tank cabinet houses a carbon molecular sieve.

Description

0 NITROGEN GENERATOR 2331254 This invention relates to nitrogen

generators.

Previous types of nitrogen generators suffer from a number of disadvantages. In particular previous systems continue to generate nitrogen even when it is not required. This continual generation of nitrogen, therefore, requires the dumping of any unused nitrogen gas. This is obviously not very efficient. Many of the systems presently in use also have integral compressors which leads to excessive noise and vibration. As these systems are normally placed within a laboratory this can make the working environment very unpleasant. it should also be noted that there are now also safety regulations for excessive levels of noise is in the work place. The noise factor is compounded by the fact that it takes, from start up, around six hours to produce nitrogen of sufficient purity for most applications. This leads to the result that the generators have to be left on at all times.

In these previous types of generators there is also no monitoring control. This means that it is left to the user to change the filters when required. It is often found that due to this method of maintenance, upkeep of the generator is not maintained. This is obviously not acceptable, and damage may occur if, for example, filters are blocked, or if water gets into the system. The purity of the nitrogen will also decrease if the generator is not properly maintained.

0 Another disadvantage of previous generator systems is that they tend to take up large amounts of floor space, and in some instances as much as two square metres.

It is an object of at least one aspect of the present invention to obviate/mitigate one or more of the aforementioned problems/disadvantages in the prior art.

According to a first aspect of the present invention there is provided a nitrogen generating apparatus comprising a modular arrangement including a plurality of cabinets.

Preferably, there is at least one control cabinet and at least one tank cabinet.

Advantageously, a number of tank cabinets connected to a control cabinet.

Preferably, a networked nitrogen gas supply may be provided wherein the tank cabinets are situated in different working spaces, e.g. laboratories.

Preferably, the control cabinet includes at least part of a control means.

-In a first preferred embodiment the control means is an electronic control means and may comprise a programmable logic controller (PLC) which may be connected to two pressure transducers and two valves, preferably, solenoid valves.

Furthermore, in the first preferred embodiment each/the at least one tank cabinet may comprise a carbon molecular sieve (CMS), a (solenoid) valve and a nitrogen reservoir.

may be 0 In a second preferred embodiment the control means is an electronic control means and may comprise a programmable logic controller (PLC) which may be connected to two pressure transducers and three valves, preferably, solenoid valves.

Furthermore, in the second preferred embodiment each/the at least one tank cabinet may comprise a carbon molecular sieve (CMS), two (solenoid) valves and a nitrogen reservoir.

According to a second aspect of the present invention, there is provided a nitrogen generating apparatus comprising control means including means for monitoring the pressure of an air supply and/or formed nitrogen.

In a first preferred embodiment the control means is comprises electronic control means advantageously in the form of a programmable logic controller (PLC) and may be connected to two pressure transducers and two (solenoid) valves.

In a second preferred embodiment the control means is an electronic control means and may comprise a programmable logic controller (PLC) and may be connected to two pressure transducers and three valves, preferably, solenoid valves.

Furthermore, in the second preferred embodiment each/the at least one tank cabinet may comprise a carbon 0 molecular sieve (CMS), two (solenoid) valves and a nitrogen reservoir.

Preferably, the transducers are located in a control cabinet whereby one transducer is situated at or near the exit of an air supply from the control cabinet, and the second is situated at or near an entrance of the control cabinet where formed nitrogen enters the control cabinet.

In the first embodiment the control cabinet may comprise an air supply inlet which is connected to a a (solenoid) valve, a flow controller, optionally an auto-drain filter assembly, two transducers, a pressure regulator, a flow controller, a nitrogen supply out and an exhaust.

In the second embodiment, the control cabinet may is comprise an air supply inlet which is connected to a compressor, a (solenoid valve), a flow controller, two transducers, a pressure regulator, a flow controller, and a nitrogen supply out.

In the first preferred embodiment, the tank cabinet may comprise a carbon molecular sieve (CMS), a (solenoid) valve and a nitrogen reservoir.

Preferably, the nitrogen generating cycle involves a first phase wherein a solenoid valve in the control cabinet is open allowing air to flow to the C-MS in the tank cabinet, and wherein the valve in the tank cabinet is closed; a second phase wherein the pressure transducer connected at the exit at the air supply into the tank cabinet senses a preset pressure, the PLC opens the valve compressor.

0 Sin the tank cabinet allowing pure nitrogen to flow into the reservoir; a -third phase where the pressure in the reservoir reaches another present value, wherein the PLC then shuts the valve in the tank cabinet; and a fourth phase wherein the valve in the control cabinet switches so that oxygen rich air is vented to the atmosphere via the exhaust connected to the solenoid valve in the control cabinet.

In the second preferred embodiment the tank cabinet may comprise a carbon molecular sieve (CMS), first and second (solenoid) valves, an exhaust out and a nitrogen reservoir.

Preferably, the nitrogen generating cycle involves a first phase wherein a valve in the control cabinet is open allowing air to flow to the CMS in the tank cabinet, and wherein the first valve in the tank cabinet is closed; a second phase wherein the pressure transducer connected at the exit at the air supply into the tank cabinet senses a preset pressure, the PLC opens the first and second valves in the tank cabinet allowing pure nitroTen to flow into the reservoir; a third phase where the pressure in the reservoir has reached another preset value, wherein the PLC then shuts the second valve in the tank cabinet and the valve in the control cabinet; and a fourth phase wherein so that exhaust the first valve in the tank cabinet is switched oxygen rich air is vented to the atmosphere via the connected to the first valve in the tank cabinet.

Preferably, the PLC has a display, e.g. a liquid 0 crystal display (LCD) which displays information.

Preferably, the display indicates when filters in the system need to be changed.

Preferably, there is provided means by which in the PLC can be updated at any time.

Preferably, further tank cabinets may be connected to the same control cabinet.

Preferably, the PLC provides an ability to constantly monitor the apparatus whereby it is possible to have the apparatus move into a standby mode wherein generation of nitrogen gas is suspended. In this way the apparatus works only upon user demand.

Preferably, the nitrogen formed is of a purity of 99.9995%.

According to a third asp ect of the present invention there is provided a method of supplying nitrogen comprising the steps of:

A. providing a nitrogen generating apparatus according to the second aspect; monitoring the pressure of the formed nitrogen by the pressure monitoring means such that once the pressure of the formed nitrogen falls to a first predetermined level, air is supplied to a nitrogen generating means; removing nitrogen from the air supplied; D. monitoring the pressure of the air supplied to the nitrogen generating means such that once the pressure of the air rises to a second predetermined level the collected is B. c.

0 nitrogen is supplied.

Preferably, the nitrogen generating means is a carbon molecular sieve (CMS).

Preferably, the nitrogen is supplied to a nitrogen reservoir tank.

Advantageously, stages B, C and D may be repeated as required.

A previously known type of nitrogen generator, along with a embodiments of the present invention, will now be described by way of example, with reference to the drawings in which:

FIGURE 1 is a schematic representation of an existing nitrogen generating apparatus; FIGURE 2 is a schematic representation of a nitrogen generating apparatus according to a first embodiment of the present invention; FIGURE 3 is a schematic representation of electronic circuitry associated with the nitrogen generator of Fig. 2; FIGURE 4 is chart of pressure versus time for parts of the nitrogen generating apparatus of Fig. 2.

FIGURE 5 is a schematic representation of a nitrogen generating apparatus according to a second embodiment of the present invention; and FIGURE 6 is a schematic representation of electronic circuitry associated with the nitrogen generator of Fig. 5.

Referring to Figure 1, there is shown a schematic 0 -8 representation of a known nitrogen generating apparatus (system) generally designated 5 providing a single cabinet 6. First of all, the apparatus requires a supply of air. This air is compressed either through an integral compressor, or from an external source. If the air is compressed via an external source, then a flow controller 10, and a solenoid valve 12 are fitted into an air inlet of the apparatus 5. Air is only allowed into the apparatus 5 when a timer switch inside the apparatus 5 is in an on position. The timer switch also controls start-up of an integral compressor - if provided.

once the air is compressed it is fed through a filter 14. The filter 14 has a pressure gauge 16 attached to it to allow the pressure in the filter 14 to be monitored.

is An exhaust solenoid 18 is also attached to the filter 14. An exhaust filter 20 is further attached to the exhaust solenoid 18.

The compressed air then passes by a safety valve 22, normally set at 120 psi. The compressed air then reaches a carbon molecular sieve (CMS) 24.

The CMS 24 binds to the oxygen molecules in the compressed air. As the pressure in the CMS 24 increases the percentage of oxygen retained rises. This retention of oxygen reaches a maximum at around 95 psi, creating nitrogen with a maximum purity of approximately 99.9995% which flows from the top of the CMS 24 through a non-return valve 26 into a reservoir 28.

Flow from the CMS 24 to the reservoir 28 occurs when 0 pressure is equalised on both sides of a non-return valve 26. This allows the valve 26 to open, and the gas to flow in a direction towards the reservoir 28. The pressure on either side of the non-return valve 26 will increase together until the timer switch switches off the air supply, and opens the exhaust solenoid 18, allowing waste gas in the CMS 24 to vent to the atmosphere through the exhaust filter 20. This exhausting takes place within the cabinet 6. At this point gas pressure in the reservoir 28 is about 120 psi, and the gas is ready to be supplied for the customer's use. This complete cycle takes about four minutes.

The nitrogen reservoir 28 is connected to a pressure regulator 30. The pressure regulator 30 sets the output pressure at a maximum of 80 psi, which is indicated on a pressure gauge 32. The nitrogen is then passed through a mass flow controller 34 before leaving the apparatus 5.

one of the major disadvantages with this type of apparatus 5 is that whether or not the application uses nitrogen dur-Lng the time that the timer has the air supply shut off, the timer will switch on the apparatus 5 which will continue to go through the aforementioned cycles, except that the non-return valve 26 will not open, since the pressure in the reservoir 28 will be higher than the pressure in the CMS 24. In this circumstance the air from the supply continues to be dumped through the safety valve 22.

Referring now to Figure 2 there is shown a schematic 0 - 10representation of a first embodiment of a nitrogen generating apparatus generally designated 50, according to the present invention, wherein therein is provided a control cabinet 100, and a tank cabinet 102. First of all a compressor 103, which can be from an external source, or from an integral item in the apparatus 50, preferably contained in a soundproof cabinet, provides air through a solenoid valve 104. During an on-cycle air is directed to a f low controller 106. During an off-cycle air cannot pass further into the apparatus 50 as it cannot pass the solenoid valve 104.

The flow controller 106 regulates the rate at which pressure builds up in downstream components hereinafter described. The compressed air then passes through an is auto-drain assembly 108 before it reaches a carbon molecular sieve (CMS) 110 - often referred to as a CMS column - in a separate tank cabinet 102. As is normal with CMS's as the pressure in the CMS 110 increases the percentage of oxygen absorbed rises. Maximum absorption occurs at about 95 psi. This results in nitrogen with a purity of around 99.9995% being fed into a nitrogen reservoir 114 via a solenoid valve 112. To enable the nitrogen to flow to the nitrogen reservoir 114, the solenoid valve 112 needs to be energised. The nitrogen gas then exits the tank cabinet 102.

On re-entering the control cabinet 100, the nitrogen gas is fed through a pressure regulator 116 and a mass flow controller 118. The nitrogen gas then exits the control 0 - 11cabinet 100 for supply to the required use.

The CMS 110 requires to be re-generated for approximately two minutes after it has been pressurised. This re-generation occurs by the solenoid valve 112 being deenergised, and closing, and solenoid valve 104 changing state, so that the waste gas in the CMS 110 is purged to the atmosphere through an exhaust 120.

The nitrogen generator apparatus 50 is controlled by a programmable logic controller (PLC) 200. The PLC 200 receives two inputs, one from a transducer 122, and another from a transducer 124. Both of these components are in this embodiment located within the control cabinet 100 at or near an exit from the control cabinet 100 into the CMS 110, and at or near a return entrance of the control cabinet 100, respectively.

Software written into the PLC 200 controls pressure in different sections of selectively energising, valves 104 and 112.

the air/nitrogen gas flow by and de-energising the solenoid The PLC 200 also monitors the condition of the transducers 122 and 124, and by comparison can calculate when the filter elements in the exhaust 120, and filter assembly 108 require to be changed. For the exhaust element 120 the software monitors the time it takes the waste gas to exhaust from the CMS 110 after the valve 112 has changed to allow this. This is achieved by monitoring of the pressure via pressure transducer 124. This time is compared to the previous time and calculated as a percentage increase, this value is stored in the PLC 0 memory. As the exhaust element 120 becomes clogged over time and the percentage rises above a set value the user is warned via a display comprising an LCD screen 205 that the element 120 requires to be changed. This process is similar for the filter element in the assembly 108 with the percentage increase being calculated from the time taken for the CMS 110 to reach a set pressure; this is measured via pressure transducer 122.

The software incorporated into the PLC 200 also enables a warning system to be initiated when the air supply is under producing with respect to pressure or flow, allowing appropriate action to be taken. The collected information is displayed on an LCD screen 205 located on a front of the control cabinet 100.

with the ability to constantly monitor the apparatus 50 it is also possible to have the apparatus 50 move into or adopt a standby mode, whereby generation of the nitrogen gas is suspended. This also helps to extend the working life of the CMS 110, filters and compressors.

The software incorporated into the PLC 200 can also be upgraded with future new and improved software technology at a low cost and also little or no down-time for nitrogen production.

As can be seen from Fig. 2 the apparatus 50 also enables the addition of further tank cabinets 102 to be connected to the same control cabinet 100. This is obviously advantageous as only one control cabinet 100 needs to be initially procured and the apparatus 50 can be 0 is - 13 upgraded at any time should the nitrogen generating capacity require to be increased.

In Figure 3 is shown a schematic of electronic control circuitry 210 for the nitrogen generating apparatus so. An AC/DC power supply 215 is used to power the PLC 200 and any other electronic components. The PLC apparatus 50 has the LCD 205 to enable an operator to monitor the production of nitrogen, e.g. by displaying relevant pressure measurements from transducers 122, 124.

The PLC 200 is also connected to the pressure transducers 122 and 124 through ananalogue-to-digital converter 220. A signal from the PLC 200 is then fed through the analogue-to-digital convertor 220, which sends a signal to solenoid valves 104 and 112.

The modular design of the separate control cabinet and tank cabinet 102, and also optionally a separate compressor cabinet 103, allows space to be saved in a laboratory or other working environment which is highly desirable as previous types of these machines usually tend to take up a substantial amount of floor space. Cabinets 100, 102, 103 can, for example, be placed in different parts of a laboratory, e.g. on work surfaces or below work benches.

The modular design also enables a number of tank cabinets 102 - perhaps remotely located one from another, e.g. in different laboratories - to be networked to a single control cabinet 100.

Referring now to Figure 4 is a graph showing 0 variation in pressure for the nitrogen reservoir 114 and the CMS 110. At time 0, the solenoid valve 104 changes over allowing air to flow from the air supply to the CMS 110. It should be noted that solenoid valve 112 does not allow any flow from the CMS 110 to the nitrogen reservoir 114 at this point.

The pressure in the reservoir 114 is falling, at this point, since it is assumed that nitrogen gas is being used up. Once the pressure transducer 122 senses a pre-set level e.g. 95 psi, the PLC 200 opens solenoid valve 112 to allow pure nitrogen to flow into the reservoir 114 during the time that the solenoid valve 112 is open. The CMS 110 and reservoir 114 pressure rises at the same rate. The PLC 200 monitors pressure through pressure transducer 124, is and waits until a pre-set time, e.g. approximately twenty seconds, after the pressure has reached a maximum preset level available before shutting solenoid valve 112, and changing solenoid 104 to allow oxygen rich air to vent to the atmosphere through exhaust 120.

The reservoir 114 pressure will now drop as the application uses gas from the reservoir 114. The process will begin again when the reservoir pressure 114, as measured by pressure transducer 124 drops to approximately 105 psi - that is to say the solenoid valve 104 will again allow air supply to the CMS 110.

It should also be noted that if the user does not use nitrogen for an extended period then the PLC 200 may be programmed to pressurise and depressurlse the CMS 110 0 - is- column, e.g. approximately once every hour, so as to obtain optimum performance once the application requires gas again.

In use, it is anticipated that a CMS 110 may provide an average of 2000 cc/min of nitrogen at a purity of around 99.9995%. However, since the CMS 110 typically needs to be re-generated for approximately the same time as it is pressurised then the final output flow of the generator will be 1000 cc/mm. Further the ratio of air in to nitrogen out will likely be around 12:1.

In Figure 5 there is shown a schematic representation of a second embodiment of a nitrogen generating apparatus generally designated 350, according to the present 304.

controller 306 invention, wherein there is provided a control cabinet 300 is and a tank cabinet 302. In use, initially, a compressor 303, which can be from an external source, or from an integral item in the apparatus 350, preferably contained in a soundproof cabinet, provides air through a solenoid valve During an on-cycle air is directed to a flow During an off-cycle al-r cannot pass further into the apparatus 350 as it cannot pass solenoid valve 304.

In this embodiment, an auto-drain assembly 308 is removably mounted on or adjacent an outside of the control cabinet 300 which enables easy maintenance.

The flow controller 306 regulates the rate at which pressure builds up in downstream components hereinafter described. The compressed air then reaches a carbon 0 -16 molecular sieve (CMS) 310 in a separate tank cabinet 302.

As is normal with CMS's as the pressure in the Cms increases the percentage of oxygen absorbed rises.

maximum absorption occurs at about 95 psi. This results in nitrogen with a purity of 99.9995% being fed into a nitrogen reservoir 314 via solenoid valves 312 and 305.

To enable the nitrogen to flow to the nitrogen reservoir 314, the solenoid valve 312 needs to be energised - this occurs when a preset pressure level is detected by transducer 322. The nitrogen gas then exits the tank cabinet 302.

On re-entering the control cabinet 300, the nitrogen gas is fed through a pressure regulator 316 and a mass flow controller 318. The nitrogen gas then exits the control cabinet 300 for supply to the required use.

Re-generation of the CMS 310 occurs by closing the solenoid valves 304 and 305 and solenoid valve 312 diverting waste gas from the CMS 310 to exhaust 320 allowing the oxygen enriched gas to purge to the atmosphere.

The nitrogen generator apparatus 350 is controlled by a programmable logic controller (PLC) 400. The PLC 400 receives two inputs, one from transducer 322, and another from a transducer 324. Both of these components are respectively located within the control cabinet 300 at or near an exit from the control cabinet 300 into the CMS 310 and at or near a return entrance of the control cabinet 300.

0 Software written into the PLC 400 controls pressure in different sections of the air/nitrogen gas flow by selectively energising, and de-energising the solenoid valves 304, 305 and 312. The PLC 400 also monitors the condition of the transducers 322 and 324 and by comparison can calculate when the filter elements in the exhaust 320 and filter assembly 308 require to be changed.

As can be seen from Fig. 5 the apparatus 350 also enables the addition of further tank cabinets 302 to be connected to the same control cabinet 300. This is obviously advantageous as only one control cabinet300 needs to be bought and the apparatus 350 can be upgraded at any time should the nitrogen generating capacity require to be increased.

In Figure 6 is shown a schematic of electronic control circuitry for the nitrogen generating apparatus 350. An AC/DC power supply 415 is used to power the PLC 400 and any other electronic components. The PLC apparatus 350 has an LCD 405 to enable an operator to monitor the production of nitrogen, e.g. by displaying relevant pressure measurements from transducers 322 and 324. The PLC 400 is also connected to the pressure transducers 322 and 324 through an analogue -to-digital converter 420. A signal from the PLC 400 is then fed through the analogue-to-digital convertor 420, which sends a signal to solenoid valves 304, 305 and 312.

The advantage of moving the exhaust 320 into the tank cabinet 302 is that it allows a control cabinet 300 to be 0 -is- manufactured wherein the presence of a noise source close to the user is eliminated.

0

Claims

1. A nitrogen generating apparatus comprising a modular arrangement including a plurality of cabinets.

2. A nitrogen generating apparatus according to claim 1 wherein there is at least one control cabinet and at least one tank cabinet.

3. A nitrogen generating apparatus according to claim 2 wherein a number of tank cabinets may be connected to a control cabinet.

4. A nitrogen generating apparatus according to any of claims 2 and 3 wherein a networked nitrogen gas supply may be provided wherein the tank cabinets are situated in different working spaces, e.g. laboratories.

5. A nitrogen generating apparatus according to any of claims 2 to 4 wherein the control cabinet includes at least part of a control means.

6. A nitrogen generating apparatus according to claim 5 wherein the control means is an electronic control means and comprises a programmable logic controller (PLC) which is connected to two pressure transducers and two valves, preferably, solenoid valves.

0 - 207. A nitrogen generating apparatus according to any of claims 2 to 6 wherein each/the at least one tank cabinet comprises a carbon molecular sieve (CMS), a (solenoid) valve and a nitrogen reservoir.

8. A nitrogen generating apparatus according to any of claims5 to 7 wherein the control means is an electronic control means and comprises a programmable logic controller (PLC) which is connected to two pressure transducers and three valves, preferably, solenoid valves.

9. A nitrogen generating apparatus according to any of claims 2 to 6 wherein each/the at least one tank cabinet comprises a carbon molecular sieve (CMS), two (solenoid) valves and a nitrogen reservoir.

10. A nitrogen generating apparatus comprising control means including means for monitoring the pressure of an air supply and/or formed nitrogen.

11. A nitrogen generating apparatus according to claim 10 wherein the control means comprises electronic control meails advantageously in the form of a programmable logic controller (PLC) is connected to two pressure transducers and two (solenoid) valves.

0

12. A nitrogen generating apparatus according to any of claims 10 and 11 wherein there is at least one tank cabinet which comprises a carbon molecular sieve (CMS), a (solenoid) valve and a nitrogen reservoir.

13. A nitrogen generating apparatus according to any of claims 10 to 12 wherein the control means is an electronic control means and which comprises a programmable logic controller (PLC) and is connected to two pressure transducers and three valves, preferably, solenoid valves.

14. A nitrogen generating apparatus according to any of claims 12 and 13 wherein each/the at least one tank cabinet comprises a carbon molecular sieve (CMS), two (solenoid) valves and a nitrogen reservoir.

15. A nitrogen generating apparatus according to any of claims 11 to 14 wherein the transducers are located in a control cabinet whereby one transducer is situated at or near the exit of an air supply from the control cabinet, and the second is situated at or near an entrance of the control cabinet where formed nitrogen enters the control cabinet.

16. A nitrogen generating apparatus according to claim 15 wherein the control cabinet comprises an air supply inlet which is connected to a compressor, a (solenoid) valve, a flow controller, optionally an autodrain filter assembly, 0 - 22two transducers, a pressure regulator, a flow controller, a nitrogen supply out and an exhaust.

17. A nitrogen generating apparatus according to any claims 15 and 16 wherein the control cabinet comprises air supply inlet which is connected to a compressor, a (solenoid valve), a flow controller, two transducers, a pressure regulator, a flow controller, and a nitrogen supply out.

is of an

18. A nitrogen generating apparatus according to any of claims 12 to 17 wherein a tank cabinet comprises a carbon molecular sieve (CMS), a (solenoid) valve and a nitrogen reservoir.

19. A nitrogen generating apparatus according to any of claims 10 to 17 wherein the nitrogen generating cycle involves a first phase wherein a solenoid valve in the control cabinet is open allowing air to flow to the CMS in the tank cabinet, and wherein the valve in the tank cabinet is closed; a second phase wherein the pressure transducer connected at the exit at the air supply into the tank cabinet senses a preset pressure, the PLC opens the valve in the tank cabinet allowing pure nitrogen to flow into the reservoir; a third phase where the pressure in the reservoir reaches another present value, wherein the PLC then shuts the valve in the tank cabinet; and a fourth phase wherein the valve in the control cabinet switches so 0 23that oxygen rich air is vented to the atmosphere via the exhaust connected to the solenoid valve in the control cabinet.

20. A nitrogen generating apparatus according to any of claims 12 to 17 wherein a tank cabinet comprises a carbon molecular sieve (CMS), first and second (solenoid) valves, an exhaust out and a nitrogen reservoir.

21. A nitrogen generating apparatus according to any of claims 12 to 17 and 20 wherein the nitrogen generating cycle involves a first phase wherein a valve in the control cabinet is open allowing cabinet, and wherein the is closed; a second phase connected at the exit cabinet senses a preset and second valves in air to flow to the CMS in the tank first valve in the tank cabinet is wherein the pressure transducer at the air supply into the tank pressure, the PLC opens the first the tank cabinet allowing pure nitrogen to flow into the reservoir; a third phase where the pressure in the reservoir has reached another preset value, wherein the PLC then shuts the second valve in the tank cabinet and the valve in the control cabinet; and a fourth phase wherein the first valve in the tank cabinet is switched so that oxygen rich air is vented to the atmosphere via the exhaust connected to the first valve in the tank cabinet.

0 -24

22. A nitrogen generating apparatus according to any of clams 6 to 21 wherein the PLC has a display, e.g. a liquid crystal display (LCD), which displays collected information.

23. A nitrogen generating apparatus according to claim 22 wherein the display indicates when filters in the system need to be changed.

24. A nitrogen generating apparatus according to any of claims 6 to 23 wherein there is provided means by which the PLC can be updated at any time.

25. A nitrogen generating apparatus according to any of is claims 2 to 24 wherein further tank cabinets may be connected to the same control cabinet.

26. A nitrogen generating apparatus according to any of claims 6 to 25 wherein the PLC provides an ability to constantly monitor the apparatus whereby it is possible to have the apparatus move into a standby mode wherein generation of nitrogen gas is suspended.

27. A nitrogen generator apparatus according to any preceding claim wherein the nitrogen formed is of a purity of 99.9995%.

0

28. A method of supplying nitrogen preceding claim wherein there is.:

A.

B. according to any a nitrogen generating apparatus; monitoring of the pressure of the formed nitrogen by pressure monitoring means such that once the pressure of the formed nitrogen falls to a first predetermined level, air is supplied to a nitrogen generating means; C-'.,,removing nitrogen from the air supplied; and D. monitoring the pressure of the air supplied to the nitrogen generating means such that once the pressure of the air rises to a second predetermined level the nitrogen is supplied.

29. A method of supplying nitrogen according to claim 28 wherein the nitrogen generating means is a carbon molecular sieve (CMS).

30. A method of supplying nitrogen according to any of claims 28 and 29 wherein the nitrogen is supplied to a nitrogen reservoir tank.

31. A method of supplying nitrogen according to any of claims 28 to 30 wherein stages B, C and D may be repeated as required.

32. A nitrogen generating apparatus substantially as hereinbefore described with reference to the accompanying drawings.

0 32. A method of generating nitrogen substantially as hereinbefore described with reference to the accompanying drawings.