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Title:
A VENTILATION FOR TUNNELS AND A METHOD FOR CONTROL OF SAME
Document Type and Number:
WIPO Patent Application WO/2000/036275
Kind Code:
A1
Abstract:
A ventilation system for tunnels (1) comprising active ventilation components such as controllable fans (6, 7) and/or throttles, and a method for controlling same. The ventilation system which is to be used during the tunnel excavating process, comprises at least one group of detectors (12, 13, 14) adapted to measure the air quality within the tunnel (1), signal generators providing siganals representative for the measured values, and transmitters adapted to send out these signals and transmit them to a processor (19). The processor (19) is adapted to receive signals and compare them to reference values corresponding to the required air quality. The active ventilation components (6, 7) are controlled in accordance with the difference between the reference value and the detected value to maintain the quality of air within the required values. The system allows a fast setting to desired ventilation capacity by commands stating the type of activity in the tunnel (1) and transition positions with e.g. increasing and/or decreasing ventilation in transition intervals between the typical activities. The transmission of detected values and of control signals takes place via communication plants which also may have the capacity to take care of speech communication, preferably between portable units, e.g. mobile telephones or mobile radio phones; and changes required may be transmitted to the system from each single operator.

Inventors:
HAALAND SVEIN INGE (NO)
Application Number:
PCT/NO1999/000171
Publication Date:
June 22, 2000
Filing Date:
May 31, 1999
Export Citation:
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Assignee:
HAALAND SVEIN INGE (NO)
International Classes:
E21F1/00; (IPC1-7): E21F1/00
Foreign References:
US5269660A1993-12-14
EP0205979A11986-12-30
Other References:
P.O. ANDERSSON ET AL.: "Mine ventilation control at Boliden Mineral AB", INTERNATIONAL SYMPOSIUM ON MINE MECANISATION AND AUTOMATION 2,, 1993, ROTTERDAM BALKEMA,, pages 855 - 660
K. LINDKVIST.: "Behovsstyrd gruvventilation", VERKSTAEDERNA,, 1995
Attorney, Agent or Firm:
Abc-patent, Siviling Rolf Chr Larsen B. A. S. (Brynsveien 5 Oslo, N-0667, NO)
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Claims:
Claims
1. A ventilation system for tunnels (1) comprising active ventilation components such as fans (6,7) and ventilation tubes (3,4), one or more detectors or set of detectors (12,13, 14) adapted to detect critical parameters within the tunnel (1), a central control unit (19) e. g. such as a processor, c h a r a c t e r i z e d in that the system also com prises: at least one first communication system (15,16, 17; 18) adapted to transmit measurement signals representative for the detected measuring values of the detectors (12,13, 14) to the processor (19), and a second communication system (20,22 ; 21,23) for transmitting control signals from the processor (19) to active ventilation components (6,7) preferably comprising controllable fans and/or throttles/ valves adapted to receive control signals according to one or more of the detected values from the processor (19); as the control unit (19) computes the signal values by means of a predetermined algorism which both takes the economic operation of all of the fans and also the safety conditions within the tunnel into consideration.
2. A ventilation system according to claim 1, c h a r a c t e r i z e d in that the system also com prises a command system (10) adapted to transmit fast commands (ABC) for adjusting the processor (19) according to predetermined values adapted to specific activities at the moment or to specific anticipated future activities in the tunnel (1).
3. A ventilation system according to claim 1 or 2, c h a r a c t e r i z e d in that each fast command (ABC) results in a varying, e. g. increasing or decreasing ventilation, continuously or stepwise, during a predetermin ed transition interval.
4. A ventilation system for tunnels, as stated in claim 1, 2 or 3, c h a r a c t e r i z e d in that the detectors (12,13, 14) are arranged at several locations along the tunnel (1), e. g. both close to the location where the tunnel excavation takes place (2) and close to the tunnel mouth (s) (5).
5. A ventilation system according to claim 1,2, 3 or 4, c h a r a c t e r i z e d in that the active ventilation components comprises fans (6,7) having a controllable blowing capacity.
6. A ventilation system according to claim 1,2, 3,4 or 5, c h a r a c t e r i z e d in that at least one of the communication systems also are adapted to transmit speech and possibly in addition the desired changes in the local ventilation.
7. A ventilation system as stated in claim 6, c h a r a c t e r i z e d in that speech communication takes place from/to mobile units (26) which transmit/receive signals to/from stationary units.
8. A ventilation system as stated in claim 1, 2,3, 4,5, 6 or 7, c h a r a c t e r i z e d in that the communication system also comprises a radio link station (27) adapted to receive/amplify/transmit the signals from the detectors and from other transmitting units.
9. A ventilation system as stated in any of the preceding claims, c h a r a c t e r i z e d in that at least parts of the communication system (15,16, 17 ; 18) is based on wireless or optical transmission.
10. A ventilation system as stated in one of the claims 2 9, c h a r a c t e r i z e d in that operator terminals (10,11) adapted for fast setting of the activity in the tunnel (1) are located both in a plant office outside the tunnel (1) and at the tunnelling face (2), and that said control units (19) comprises at least one memory including prestored reference values.
11. A method for controlling a ventilation system for tunnels, which ventilation system comprises at least one detector or one set of detectors (12,13, 14) adapted to detect pollution within the tunnel (1), at least one fan (6,7) and associated ventilation tube (s) (3,4) adapted to supply the tunnel (1) with fresh air, at least one control unit (19) such as a processor adapted to adjust the fan (s) (6,7) dependent on detected pollution values, c h a r a c t e r i z e d in that the method in particular is adapted for tunnels (1) under excavation, and where the tunnel accordingly is exposed to different activities in substantially regular sequences and at subsequent intervals, having a very different pollution degree within different intervals of time, and where the ventilation system substantially is controlled as an operator gives commands about anticipated activities and their duration, preferably by means of a number of predetermined program settings (A, B, C), while the detectors (12,13, 14) are connected in such a manner that they may overrule the predetermined commands (A, B, C) to ensure that the degree of pollution neither shall exceed the specified nominal values nor will fall much below these values, at least not for time periods of a long duration.
12. A method as stated in claim 11, c h a r a c t e r i z e d in that the point of time at which the predetermined and anticipated activities are set, precede the exact points of time when the activity changes character; so that the ventilation system in advance pre pares the air quality in the tunnel to the next activity condition in the sequence of activity conditions.
13. A method for controlling a ventilation system (3,4; 6,7) for tunnels (1) as stated in claim 8 or 9, c h a r a c t e r i z e d in that the quality of the air and/or different pollution values within the tunnel (1) are measured, and that signals representative of the momentaneous air quality are deduced therefrom, the signals representing the real air quality are transmitted to a control unit (19) and compared to pre determined reference values for the desired air quality, and if the desired quality of air is not present at the moment a control signal is transmitted to the active ventil ation components (6,7) to increase the supply of fresh air for the time being until the desired air quality has been reached, whereupon the fresh air supply is reduced to its previously value.
14. A method for controlling a ventilation system (3,4; 6,7) for tunnel excavation, c h a r a c t e r i z e d in that the quality of the air always is maintained better than the values required in the specifications, however, does not exceed such values with more than a predetermined percentage e. g. 3%. AMENDED CLAIMS [received by the International Bureau on 11 April 2000 (11.04. 00); original claims 114 replaced by new claims 111 (4 pages)] 1. A ventilation system for tunnels (1) during the excavating process, comprising active ventilation components such as fans (6,7) with a controllable blowing capasity and ventilation tubes (3,4), one or more detectors or set of detectors (12,13, 14) adapted to detect critical parameters within the tunnel (1), a central control unit (19) e. g. such as a processor, and where the system also comprises: at least one first communication system (15,16, 17; 18) adapted to transmit measurement signals representative for the detected measuring values of the detectors (12,13, 14) to the processor (19), and a second communication system (20,22 ; 21,23) for transmitting control signals from the processor (19) to the active ventilation components (6,7) adapted to receive control signals according to one or more of the detected values from the processor (19); c h a r a c t e r i z e d in that the control unit (19) computes the signal values by means of a predetermined algoritm which both takes the economic operation of all of the fans and also the safety conditions within the tunnel into consideration, and that at least one of the communi cation systems are adapted to transmit speech signals as well as signals representing the desired changes in the local ventilation.
15. 2 A ventilation system as stated in claim 1, c h a r a c t e r i z e d in that speech communication takes place from/to mobile units (26) which transmit/receive signals to/from stationary units.
16. 3 A ventilation system according to claim 1 or 2, c h a r a c t e r i z e d in that the system also com prises a command system (10) adapted to transmit fast commands (ABC) for adjusting the processor (19) according to predetermined values adapted to comply to specific activi ties at the moment or to specific anticipated future activities in the tunnel (1).
17. 4 A ventilation system as stated in claim 1,2 or 3, c h a r a c t e r i z e d in that the communication system also comprises a radio link station (27) adapted to receive/amplify/transmit the signals from the detectors and from other transmitting units.
18. 5 A ventilation system as stated in any of the preceding claims, c h a r a c t e r i z e d in that at least parts of the communication system (15,16, 17; 18) is based on wireless or optical transmission.
19. 6 A ventilation system according to any of the claims 3 5, c h a r a c t e r i z e d in that each fast command (ABC) results in a varying, e. g. increasing or decreasing ventil ation, continuously or stepwise, during a predetermined transition interval.
20. A ventilation system as stated in one of the claims 3 6, c h a r a c t e r i z e d in that operator terminals (10,11) adapted for fast setting of the activity in the tunnel (1) are located both in a plant office outside the tunnel (1) and at the tunnelling face (2), and that said control units (19) comprises at least one memory including prestored reference values.
21. A method for controlling a ventilation system for tunnels, which ventilation system comprises at least one detector or one set of detectors (12,13, 14) adapted to detect pollution within the tunnel (1), at least one controllable fan (6,7) and associated ventilation tube (s) (3,4) adapted to supply the tunnel (1) with fresh air, at least one control unit (19) such as a processor adapted to adjust the fan (s) (6,7) dependent on detected pollution values, c h a r a c t e r i z e d in that the method in particular is adapted for tunnels (1) under excavation, and where the tunnel accordingly is exposed to different activities in substantially regular sequences and at subsequent intervals, resulting in a very different pollution degree within different intervals of time, and where the ventilation system substantially is controlled by an operator giving commands about anticipated activities and their duration, preferably by means of a number of predetermined program settings (A, B, C), while the detectors (12,13, 14) are connected in such a manner that they may overrule the predetermined commands (A, B, C) to ensure that the degree of pollution neither will exceed the specified nominal values nor will fall much below these values, at least not for time periods of a long duration.
22. A method as stated in claim 8, c h a r a c t e r i z e d in that the point of time at which the predetermined and anticipated activities are set, precede the exact points of time when the activity changes character; so that the ventilation system in advance pre pares the air quality in the tunnel to the next activity condition in the sequence of activity conditions.
23. A method for controlling a ventilation system (3,4; 6,7) for tunnels (1) as stated in claim 8 or 9, c h a r a c t e r i z e d in that the quality of the air and/or different pollution values within the tunnel (1) are measured, and that signals representative of the momentaneous air quality are deduced therefrom, the signals representing the real air quality are transmitted to a control unit (19) and compared to pre determined reference values for the desired air quality, and if the desired quality requirements of air are not met at the moment a control signal is transmitted to the active ventilation components (6,7) to change the supply of fresh air for the time being until the desired air quality has been reached, whereupon the fresh air supply is reduced to its previously value.
24. A method for controlling a ventilation system (3,4; 6,7) for tunnel excavation, according to one of the claims 810, c h a r a c t e r i z e d in that the quality of the air always is maintained better than the values required in the specifications, however, does not exceed such values with more than a predetermined percentage e. g. 3%.
Description:
A VENTILATION FOR TUNNELS AND A METHOD FOR CONTROL OF SAME.

The present invention relates to a ventilation system for tunnels and also to a method for controlling such a system.

When tunnels are to be built ventilation of the tunnel is required, but in a different degree at different stages of the building process. Today such ventilation plants usually are built during the progress of the tunnel excavat- ing process in the subsurface formations, as ventilation tube (s) supplying fresh air and/or ventilation tube (s) re- moving polluted air is/are prolonged into the tunnel from fan aggregates which initially is/are arranged outside the tunnel, and which often are expanded by further fan aggre- gates arranged along the ventilation tubes at suitable sites in the tunnel-cross section. Such fans have usually only had an on/off-control.

For road tunnels ventilation plants have been estab- lished in which detectors measure different parameters and are controlling the ventilation accordingly. However, the activity in finished road tunnels is relatively constant, as the situations with heavy traffic and low traffic do not represent essentially different conditions, but may be said to represent modifications in degree only.

During the building of new tunnels the activity changes to the contrary very much, and then also the requirements for ventilation. Normally a tunnel will pass through the following stages in a cyclic range through a seven hours working period: boring, charging, blasting, airing, loading and transportation, securing, preparing and finishing.

As previously known examples of ventilation plants in road tunnels the following publications may all the same be cited: -EP 0205979-A1 (Mitsubishi) comprising some jet fans which may be switched on/off and others which may be operat- ed at a variable rate, -EP 0240713-A1 (Mitsubishi) comprising different detec- tors, and -US 5.377. 308 (Hitachi) showing a control system for both linear and non-linear systems, e. g. usable for tunnel

ventilation.

So far there has not been undertaken specific and continuous measurements to achieve optimal values for the ventilation plant in each specific tunnel or associated to the specific activity in the tunnel during tunnel-driving and excavation. The ventilation requirements will however change very much dependent of: -the activity in the tunnel at each period, -the level of activity within the tunnel, -local changes in the quality of the structure through which the process takes places, -the pressure and temperature conditions, and also dependent of -the situation at the tunnel openings.

In a similar manner there are at least two evaluation methods to determine the ventilation requirements associated to the present situation.

1) On the first side there is the security aspect accord- ing to which the conditions within the tunnel is considered from the view of the people working within. There may be established requirements related to the oxygen contents, the contents of dangerous gasses, respirable dust, especially with a particle size between 0,5 and 5 micron, humidity, temperature and other conditions important for the health and security of people working in the tunnel. The standard- ized security requirements must always be satisfied.

2) On the other side there is the energy aspect. The fans used for ventilation may each have an energy consumption on 500-1000 kW, and an optimal function of these will have a large effect on the economy of the system. When the energy is considered the air quality neither should be much above the requirements nor should it be considerably above the requirements for a long period.

An automatic control of the ventilation within tunnels in the excavation or tunnel-driving period has so far not been used in spite of the above mentioned relations.

The present invention relates to an intelligent tunnel ventilation plant based on the following details: -detectors which continuously or at specific points of

time detect the pollution, the quality of air and possibly other conditions of interest at predetermined locations in the tunnel, -an indication of the working condition, -active components (preferably controllable fans and/or throttles, -a computer or a programmable logical control unit (PLC) adapted to acquire data from the detectors and the operators, and also adapted for deducing control signals for the active components, -a communication system (preferably wireless or using optical fibres) to transmit information from the detectors to the computer, -an additional communication system for the transmission of the control signals from the computer to the active components of the system, and finally -a power supply system adapted to transmit power to the active components (fans) included in the system.

The object of the present invention accordingly is to provide a ventilation system for tunnels comprising active ventilation components which may be controlled continuously or in steps according to signals obtained from detectors located within the tunnel, and where this control preferably takes place in an automatic way from the detected values by means of a communication system and a computer to get econo- mic and safe operation of the ventilation plant according to the below stated claims. The object also is to provide a method for controlling such a ventilation system allowing a fast readjustment of the system from the working face when sudden changes in the working conditions occur or are anticipated, so that the readjustment takes place without large transients giving problems and without exceeding the standardized values.

By using the present invention a further advantage is obtained which enhance the security within the tunnel, results in better communication between groups and single persons within the tunnel and outside of the tunnel, and also enhance the working environments in the tunnel, almost without additional equipment and costs. All the same an

enhanced communication is obtained as a positive"side effect"of the invention.

It should be noted that the present method and the present ventilation system in particular is adapted for tunnelsduring a building process in which the tunnel in substantially regular sequences is exposed to different activities in subsequent intervals of strongly deviating pollution degree. Accordingly, the ventilation system first of all will be controlled by an operator giving commands related to the anticipated (activity) activities in the future sequence, and also the duration of each such future activity, and then preferably gives such instructions by means of a certain number of predetermined program values which may be pre-stored in the memory of the system.

It is also important that the detectors are connected to the system in such a manner that they at any time may overrule these preprogrammed commands and thus ensure that the degree of pollution will not at any time exceed the accepted specifications, a situation that could occur if e. g. the generation of dust during blasting was much higher than anticipated, e. g. due to local variations of the quality of the formations in which the blasting takes place.

The detectors also ought to have the ability to reduce the momentaneous value of the amount of fresh air supplied, if the quality of the air becomes substantially higher within the tunnel and at all detectors than required according to the specifications. In such a manner an economic operation of the system may be secured.

As this invention introduces communication systems mainly being developed to transmit detected measuring values to the computer and to transmit the control signals to the fans or blowers, these communication systems also introduces the possibilities to transmit further information through the same communication system. Successful tests have been done to combine a package switched, digital speech communi- cation system with a digital transmitting system for data values detected and control signals. Accordingly, a practi- cal solution has been found according to which small, port- able, mobile transceivers, corresponding to modern mobile

telephones and then also speech communication is obtained, and at the same time each single operator can send messages about desired changes in the ventilation from the operator's location. A very good communication may be obtain even with- in long tunnels, e. g. by providing a radio link station at each second kilometre along the tunnel length. In this manner a good speech communication may be obtained between operators within the tunnel, between operators within and outside the tunnel, and also to the site Office outside the tunnel. Such further speech communication may be obtained without great expenses as the base of the system is trans- mitters/receivers already incorporated in the detecting and control system. To get a good and fast communication within the tunnel, there has previously been necessary to use an additional communication plant, using this invention however, such an additional plant will be unnecessary as it may be integrated in the communication plant used for the control of the ventilation, and then in particular inte- grated with the wireless part of this communication plant.

As already mentioned all communication may take place in one single channel, but if desired it may of course also be distributed on two or more channels.

All these features are obtained by a ventilation system and a method according to the claims below.

To give a more clear understanding of the system according to the present invention it is referred to the detailed specification below showing different embodiments, and also to the accompanying Fig. 1 in which the most important components of a ventilation system arranged in a tunnel being in the excavating process are shown.

It should be mentioned that the figure only is meant to show the principles and the most important components in the system, that the scale in the figure not necessarily is the same in different directions and that even important compo- nents may be omitted from the figure if they should be obvious for skilled people in this technical field and does not comprise any part of the invention itself.

On Fig. 1 a tunnel is being built in a geological structure, and this tunnel is not finished, but is in the

excavating process in the tunnel face 2 and should accord- ingly be further extended by means of conventional tunnel boring equipment or similar devices.

To obtain sufficient fresh air within the tunnel 1 at least one supply tube 3,4 is/are arranged for the supply of fresh air. These tubes 3,4 may be of a conventional type and are usually extended further along the tunnel 1 during the blasting. It should already now be mentioned that the tunnel 1 on the figure may pass several kilometres into the subsur- face structures, while only the tunnelling face 2 and the area close to the tunnel mouth 5 is shown on the figure as being the most interesting areas of the tunnel.

In conventional ventilation plants a fan or blower 6,7 is arranged associated to the fresh air input for each of the fresh air supply tubes 3,4. Normally only one tube is used for such an air supply but instead it has a large cross section area. However, two or more such supply tubes 3,4 may be used instead. If the tunnel has a long length, it is also previously known to increase the blower capacity by arrang- ing additional fans or blowers 8,9 (assumed by dotted lines on the figure) along the supply tubes where required. In conventional plants these fans are however, built with a fixed and not changeable fan capacity, and accordingly the fans goes full speed when working, but may possibly be stopped completely in periods, e. g. for one or for a few supply tubes such as 3 and 4 on the figure.

Some kind of simple tele control has previously been used for the fans in the most sophisticated of known plants as the fans may be started and stopped by an operator being at the working face 2 from where he can use a remote control unit to start or stop fans at the tunnel mouth or somewhere else along the supply tubes for fresh air.

Such remote control stations can both give the opera- tors and working people at the tunnels face a better safety and better working conditions as the persons themselves can effect the quality of the air when desired, and also enhance the working environments on the tunnel face.

Such a remote control may also take place from the site office 11 situated outside the tunnel, but it is found

advantageous to have the possibility to overrule commands from the site office directly from the tunnelling face by means of a separate control panel 10.

The control panel 10 shown on the figure may be com- bined with or replaced by one or several mobile transceivers as assumed on the figure by reference 26. Each operator may then also talk with other operators within or outside the tunnel. These units may in addition be adapted to transmit desires of increased or reduced ventilation, e. g. to obtain a reduction of draught on the working site, and the plant may evaluate such desires and accomplish the same if within the given specifications and allowed limits. Finally the system may include time-out functions, such that the desired changes which are allowed when all the different statements are considered, only will be changed for a certain period of time whereupon the automatic system again takes control.

According to the present invention groups or arrays of detectors 12,13, 14 are now also mounted on different locations along the tunnel. Each such group of detectors normally may include one detector for detecting nitrogen or nitrogen oxides, one detector for carbon oxide, and also one detector for dust particles and then especially for respir- able dust having a particle size between 0,5 and 5 micron.

For specific conditions other detectors may of course be used as well in these detector arrays.

Each detector array 12,13, 14 is connected to an associated signal source with a transmitter 15,16, 17. These signal transmitters are on the figure assumed by aerials for wireless transmission of signals representing the values measured by the detectors. However, other solutions are viable, e. g. using a normal electric wire connection for the transmission of signals representing the detected values out of the tunnel. These arrays may be autonomous, battery operated units, or they may receive energy from the mains within the tunnel.

No matter how the signals representing the detected values within the tunnel are generated and transmitted, they are applied to a receiver 18 arranged in connection to a programmable, logical, control unit (PLC) or a suitable

computer 19. This unit or computer 19 converts the signals received according to a predetermined algorithm and converts the received signals into control signals transmitted further through communication channels 20,21 to control units 22,23.

Eventually the working capacities of the fans or blowers 6 and 7 are to be controlled. In a preferred embodiment of the invention these fans have such a con- struction that they may be frequency controlled, i. e. their velocity or rotational speed and accordingly their blowing capacity is controlled by changing the frequency of the input signal. With this preferred embodiment of the system, the control units 22 and 23 may be frequency regulating circuits which provide output voltages having frequencies resulting in the desired speed of the blowers 6 and 7.

Equivalent control systems of a different kind may of course also be used. The fans may e. g. be power controlled by means of thyristors changing the duty cycle of the alternate current applied to the fans. Also other well known controlling principles may be used.

During the working of the plant the control may e. g. be carried out in such a manner that predetermined maximum values are established for the detectors mounted along the tunnel. Normally there will not be accepted that the detected values exceed or fall below predetermined limit values any place along the tunnel. Accordingly each single detector may transmit a control signal to the control unit 19 as soon as any detected value exceeds/falls below the predetermined values within the tunnel. Then the fans will increase their working velocity and more fresh air will be supplied to the tunnel face each time the detected pollution exceeds predetermined limit. The limit values of the detec- tor (s) may in a practical embodiment be adjusted to a some- what stronger value than specified in suitable specifi- cations and regulations, i. e. so that the activity of each fan will be changed before this advantageous measuring value are registered. The detected values resulting in changes of the ventilation may e. g. be approximately 5% below (i. e. 5% more strict) specifications agreed upon. Therefore the

ventilation quite surely will be increased before the real, predetermined limit values are met, e. g. so that the real air quality always will be at least 3% better (for one single or for each detected value) than stated in the specifications. In this manner each single detected value may be given a different security limit.

A different condition which also will affect the pollution level within the tunnel, is the kind of activity taking place within the tunnel at the moment. As one single example it may be mentioned that the dust pollution is much higher during blasting than during boring as the latter process is relatively free for dust. During the transport- ation the pollution of the air within the tunnel normally will be on a more average level.

To get a fast adaption of the ventilation system to the prevailing conditions, a controlling process using a control panel 10 operated directly by the operator may be used in addition to the control obtained by means of the detectors.

This control unit may be provided with a functional keyboard A, B, C, where the activity may be loaded, e. g. by stating that transportation takes place. This control panel may also be provided with a remote control unit having an aerial 24, which in a similar way as the remote control units of the detectors 12,13, 14 transmits control signals out of the tunnel, e. g. via wireless auxiliary means, as assumed by the arrow 25. The signal 25 may be received by the control unit 19 via its antenna 18 and adjusts the fans 6,7 immediately to the correct level for this type of activity, a command which may be over-ruled by signals from each single detector group 12,13, 14 if the detected parameters any place in the tunnel come close to the predetermined limit values. By this functional setting the desired quality of the air in the tunnel may be achieved much faster each time when changes occurs in the working process.

There may also be certain transient intervals in which the ventilation may be adjusted, not only dependent of the prevailing conditions but also related to anticipated conditions within a short time horizon. The degree of ventilation may in such transient intervals be increased or

reduced according to predetermined rules. In this connection empirical, theoretical and practical information may be crucial. Practical conditions which should be taken into account are: The fresh air supply should not be so generous just before blasting that the ventilation tube are complete- ly blown up during the blasting process. If so the air pressure may tear down the complete ventilation tube and destroy it. On the other side the air flow within the tunnel should not be so fast that resting, i. e. settled dust is agitated. This will only increase the pollution. All such conditions may be taken into concern during the transition intervals.

The plant should work in such a manner that the pollution never exceeds normative values given in the specifications and regulations, and only in short intervals it should give a pollution well below the requirements.

The supply tubes 3,4 for fresh air may also be provided with detectors adapted to measure the amount of fresh air supplied to the tunnel face Qs and in a corresponding way the amount of air passing specific cross sections of the tube may be measured on several places. The supply tubes 3,4 will normally not have joints and side walls quite without a leak, and some of the fresh air supply will leak out along the tube or at local places of the tube. In a similar way the pressure of the supplied air may be detected on differ- ent places along the tube and also at the tunnel face and the values of the amount of air and air pressure may be used both as an indication of a proper operation of the control system and as parameters in the algorism converting the detected values registered to the necessary frequency change in the regulating system.

Large amounts of energy may be saved by a correct use of the equipment at any or all time. The rpm of the fans varies with the third power of the energy consumption, and in a practical case it will be seen that a reduction of the rpm of the fans to the half will reduce the energy require- ments to one eight. Still more important is that such a control system can ensure that harmful conditions do not occur. Accordingly the control system will have a positive

influence on health, environment, security and working economy. By using a control system according to the invention one will find that the ventilation costs are reduced with approximately 50% without changing the requirements to security and environments.

As mentioned above the transmitters, the antennas and the receivers 12,13, 14 and 24, may also be used for mutually speech communication between the operators and also between the operators and the plant office. One or more radio link stations 27 which each receives/amplifies/transmits all the received signals, may be arranged alongside the tunnel, e. g. one station per each second kilometre if this is the range of the transmitters and receivers.

As assumed above many parameters may be changed without leaving the scope of the present invention. Thus the number of supply tubes for fresh air may be changed, the control of the fans may be changed and also the communication systems both from the detectors to the controlling computer, and the system acting from the controlling processor to the fans, which may be modified in numerous ways within the scope of the invention. All equivalent techniques may also be used.

Detectors of different types and also detectors of quite another kind than mentioned above may be included in the detector groups. Is should also be mentioned that fibre optical cables may give large advantages in connection with the communication from the tunnel and out to the control system, as an optical communication system has an extremely large band width and never impose any risk of explosions.




 
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