The present invention relates to a shutdown system for shutting down electrical power and/or a pressurized area in response to the detection of irregularities by means of sensors and to a habitat system for performing hot work including said shutdown system.

The use of equipment that may ignite inflammable gas leaks in environments where gas leaks may occur, causing the presence of an inflammable concentration of the gas in the environment, is heavily regulated to avoid smaller or larger accidents in a situation in which there is a gas leak. Offshore and onshore petroleum installations, petrochemical plants etc. are environments in which the ignition of a gas leak may have disastrous consequences. Company standards, national standards as well as international standards have therefore been introduced to regulate which kinds of operations are allowed and not allowed in certain defined areas, and which precautions have to be taken for an operation to be performed in an area where the standards do not allow such work.

In offshore oil and/or gas fields, such as in the North Sea, hot work on board an oil and/or gas installation in operation was not allowed. However, large maintenance projects in the early 1990s made it practically and economically difficult and/or impossible to keep such strict regulations. Shutdown centres were introduced, i.e. mobile units comprising a central unit designed to shut down any hot work if irregularities were detected, either by personnel hitting a shutdown button manually, and/or by automatically shutting down the hot work if gas was detected by sensors connected to the shutdown centre. The shutdown centres were arranged to cut the supply of electricity and/or pressurized air for the operation of tools that generate heat and/or sparks. Additionally, the work areas were preferably protected by means of habitats, i.e. temporary enclosures surrounding the work area. To further protect the work area from the ingress of inflammable gas, the habitats were pressurized by means of fans drawing air from an area assumed to be safe.

Examples of shutdown centres equipped and used for this purpose are the units TN 87-4 and TN 92-4, both produced and marketed by Technor AS, Norway, launched in 1987 and 1992, respectively. The units are designed to be connected to the electrical supply at the installation in question via a cable for input power, and are equipped with connectors for connecting cables for supplying electricity to electric tools. Typically, four gas sensors are connected to the unit, which unit is programmed to cut the power if one or more of the sensors detect gas. The units may also be equipped to stop the supply of pressurized air to tools driven by pressurized air.

However, the Technor units are mobile, but relatively heavy because of the strict requirements for Ex-protection of units powered by the working voltage of the shutdown centres and the electric tools involved, i.e. typically voltages such as 230 V or 480 V. The above-mentioned units have a weight of 150 to 115 kg, respectively. The weight and the Ex-protection do also make the units relatively expensive. The units may be moved by e.g. cranes. Other shutdown centres from alternative suppliers are available and their characteristics are substantially the same as the specifically identified units.

Even though the existing shutdown centres may be adopted to control even pressurized air, the shutdown centres require the supply of electrical power. The supply of electrical power is not required to a work space where only tools operated by pressu rized air are required. Using the presently available shutdown centre for such operations requires an electrical supply cable to be connected to the centre in addition to pressurized air. Availability of electrical power may be limited by the availability or electrical supply in the area and the maximum allowable length of such cables. In areas with risk for explosions, especially in areas at gas and oil installations, there is a maximum limit of the length of electrical power cables operating at 240 V or 480 V. The limit may be 25 m. For cables of 3-phase current, the limit may be 40 m. It is not allowed to join two power cables. A pressurized-air line is not regarded as posing a risk and may be as long as necessary, e.g. 300 m or even longer.

WO2004027724 of STS Stillasservice AS relates to a security system for the operation of habitats in hazardous areas, where a shutdown centre of the type described above is used to shut down the power to the habitat if "irregularities" such as the presence of inflammable gas are detected. EP2364238B1 of Safehouse Habitats (Scotland) Ltd relates to a corresponding control system, where the shutdown of the electrical power to a habitat is operated independently of a shutdown system for closing the air supply for pressurizing the habitat if gas is detected in the air intake. WO2013121197, also to Safehouse Habitats Ltd., relates to a control system for use with a hot work habitat. A gas sensing module is supplied with either 110 V or 240 V AC power and a multi sensor module is supplied with 110 V AC power.

For safety reasons, known habitat systems require the presence of two fire guards. One fire guard is positioned at the shutdown centre, and one fire guard is present at the habitat.

There is a need for a habitat system which may be positioned in any location irrespective of distance to a permanently installed source of power, e.g. 240 V or 480 V AC. It is time consuming to install a temporary power line for e.g. a 240 or 480 V current supply to comply with restrictions and regulations. There is further a need for a habitat system which can operate without a current supply of e.g. 110 V, 240 V or 480 V AC, when the tool or tools that are operated within the habitat is not requiring 240 V or 480 V electrical power, e.g. using pressurized air or batteries at low voltage as energy source, and at the same type operate the habitat system according to company and governmental restrictions and guidelines.

An object of the present invention is to provide a shutdown centre which increases the flexibility to enable control of pressurized air and/or electrical power to a work area, such as a habitat. A further object is to provide a shutdown system and a habitat system which can be operated continuously on low voltage DC such that it can be operated by batteries only. A further object is to position the shutdown system and its control centre close to the habitat such that it is sufficient with one fire guard.

The invention has for its object to remedy or reduce at least one of the drawbacks of the prior art or at least provide a useful alternative to the prior art.

The object is achieved through features which are specified in the description below and in the claims that follow.

According to a first aspect, the present invention relates to a shutdown system for shutting down at least one of pressurized air and electrical power to a habitat in response to the detection of irregularities by sensors, the shutdown system comprising a control unit connected to the sensors, at least one of a quick responding valve and a power switch for controlling the pressurized air and the electrical power, respectively, to the habitat, where:

- the control unit is continuously operated by low voltage DC from a battery;

- the at least one of the quick responding valve and the power switch is separate from the control unit; and

- the at least one of the quick responding valve and the power switch is connected to, and controlled by, the control unit by means of a low voltage control line.

The control unit may be operated by the battery (37) at a voltage of 48 volts or at a lower voltage.

The shutdown system may further comprise a fan unit, the fan unit may comprise a fan and a shutdown valve, and the fan unit may be connected to a gas sensor such that detection of inflammable gas above a predetermined concentration shuts down the fan and the shutdown valve. The quick responding valve may be comprised of a solenoid valve. The shutdown system may be portable.

According to a second aspect, the present invention relates to a habitat system for performing hot work in an environment where unshielded hot work is prohibited, the habitat system comprising a habitat for creating a barrier between a volume inside the habitat and the surroundings, an overpressure-air channel for providing pressurized air to the habitat, at least one of a pressurized-air line and a power line for providing pressurized air and electrical power, respectively for tools for performing hot work inside the habitat, and a control unit connected to sensors, of which at least one sensor is positioned within the habitat, the control unit being designed to shut down the supply of at least one of pressurized air and electrical power for the hot work, the control unit being arranged outside the habitat, and where the control unit is continuously operated by a battery at a voltage of 48 V or at a lower voltage.

At least one of a quick-responding valve and a switch for shutting down pressurized air and electrical power, respectively, is positioned inside the habitat.

According to one embodiment, the control unit may be operated by batteries at a voltage of 24 V or lower, such as 18 V or 12 V. The control unit may in one embodiment comprise the battery.

The quick acting valve may be comprised of a solenoid valve. At least one of the sensors may comprise a sensor for the detection of inflammable gas.

According to one embodiment, the habitat system further comprises a fan unit for providing overpressure air to the habitat via an overpressure-air channel. The fan unit may comprise a battery for providing power for controlling the supply of overpressure air to the habitat, for the control unit and for the sensors, quick acting valve and switch connected to the control unit. The control unit may be portable. The control unit may weigh less than 50 kg. The control unit may weigh less than 25 kg. The control unit may weigh less than 20 kg.

According to a third aspect, the present invention relates to a method for establishing a habitat system, where the method comprises the step of establishing a habitat in a classified area, and where the method further comprises:

- to provide a shutdown system according as described; and

- to position a control unit of the shutdown system in the vicinity of the habitat such that one fire guard overlooks both the habitat and the control unit. In the vicinity of the habitat means that the distance is less than 1 m, alternatively less than 2 m, alternatively less than 4 m, alternatively less than 6 m, alternatively less than 8 m, and alternatively less than 10 m.

The method may further comprise to establish the control unit at a distance from an approved high voltage terminal that exceeds local restrictions for connecting a high voltage cable between the control unit and the high voltage terminal. High voltage may be 240 V or 480 V. The distance from the approved high voltage terminal may exceed 20 m. The distance from the approved high voltage terminal may exceed 40 m. An approved high voltage terminal is a permanent electrical terminal on the installation. A temporary electrical terminal established for the performance of temporary work is not defined as an approved high voltage terminal.

In what follows, examples of preferred embodiments are described, which are visualized in the accompanying drawings, in which :

Figure 1 shows a principle sketch of an embodiment of the present invention ;

Figure 2 shows a principle sketch of an alternative embodiment of the present invention;

Figure 3 shows an alternative embodiment of the habitat system shown in figure 1;

and

Figure 4 shows an alternative embodiment of the habitat system shown in figure 2.

In the present description and claims, the term "habitat" is used for a temporary enclosure surrounding a work area. The enclosure may be a utility tent having walls of flame-retardant cloth, or a temporary house made of heat-resistant plates, or a combination of plates and cloth. The size and the shape of the habitat may differ substantially according to the specific needs. The actual construction and choice of materials etc. are common general knowledge of the person skilled in the art. The habitat is preferably equipped with an air supply for introducing overpressure air, to give pressure inside the habitat that is higher than the ambient air pressure to avoid an ingress of any inflammable gas present in the surrounding air into the habitat in case of a gas leak at the installation. Typically, the requirement is that there should be an overpressure corresponding to a water column of at least 5 mm.

In the figures, the reference numeral 1 indicates a habitat installation. The habitat installation 1 comprises a habitat 10 and a shut down system 2. The shut down system 2 comprises a control unit 20. The habitat 10 is arranged to enclose the work area in an unsafe area 99 or classified area 99. Operations carried out inside the habitat 10 are not allowed outside the habitat 10. Such operations are defined as hot work according to relevant standards, company instructions or governmental regulations, and are different kinds of work which generates hot surfaces, and/or sparks. Equipment not allowed outside the habitat 10 may be any equipment that is not Ex-safe according to the requirement, i.e. equipment that may create sparks that can ignite a gas.

A fan unit 3 is arranged in an overpressure-air channel 4 to deliver pressurized air to maintain a required overpressure inside the habitat 10. An air-inlet gas sensor 6, 60 is arranged in or close to an air inlet 41 of the overpressure-air channel 4. The air inlet 41 is positioned in a safe area 90 or unclassified area 90, being as far as possible from any gas-leak sources and upwind of the habitat 10 and any gas-leak sources. The air- inlet gas sensor 60 is connected to the fan unit 3 by an air-inlet gas sensor line 70.

The fan unit 3 comprises a fan 31, a shutdown valve 33, or dampener 33, arranged inside the fan 31, a fan-unit control unit 35 for shutting down the fan 31 and the shutdown valve 33 to close the overpressure-air channel 4 if gas is detected by the gas sensor 60, and a battery 37. The fan 31 is preferably operated by pressurized air received from the pressurized-air system 8 at the installation, via a pressurized-air line 38. The pressurized air in line 38 is preferably controlled by a quick acting valve 39 such as a solenoid valve 39 that is automatically closed to stop the supply of pressurized air to the fan 31 if inflammable gas over a preset concentration is detected by the sensor 60. The shutdown valve 33 is provided to ensure a rapid and full shutdown of the supply of overpressure air to the habitat 10 through the overpressure-air channel 4 in the case of gas being detected by the air-inlet gas sensor 60. The shutdown valve 33 is a valve that automatically closes if it is not actively held open. Preferably, the shutdown valve 33 is a valve which is held open by means of one or more electromag- nets powered by the battery 37 in the fan unit 3, and which closes automatically if the power from the battery 37 is cut.

The battery 37 in the fan unit 3 may conveniently have a voltage of 12, 18, 24, or 48 volts and a capacity sufficient to operate continuously the fan control unit 35, the air- inlet gas sensor 60, any solenoid valves 39 in the fan unit 3, and the control unit 20 for the habitat 10 for a predetermined period. The predetermined period is conveniently 2 to 24 hours, such as 4 to 12 hours, or about 10 hours. The predetermined period is a compromise between the optimal or wanted time of operation for the fan unit 3 and the practical limits to obtain an easily transportable fan unit 3 due to the weight of the battery 37. Optionally the fan unit 3 may be connected to a power cable (not shown) of a voltage of 240 V or 480 V to charge the battery 37. The power cable may be connected to an approved high voltage terminal 77. The battery 37 may be replaceable.

The air-inlet gas sensor 60 is connected to a switch unit 32 that may be switched on manually to give power to the solenoid valve 39 controlling the pressurized air for the fan 31, and for opening and keeping open the shutdown valve 33. Additionally, the switch unit 32 will also supply electrical power from the battery 37 therein to the control unit 20 via a control-unit power line 72 as soon as it is verified that the predetermined overpressure inside the habitat 10 is obtained. Verification of the overpressure may be done manually by means of manually hitting a button (not shown) or turning a switch (not shown) as soon as the required overpressure is obtained, or the overpressure may be measured by different well-known measurement methods. For example, an overpressure measurement line 13, being a flexible tube connecting the interior of the habitat 10 to the fan unit 3 where the pressure difference is measured, and the pressure-difference measuring device is connected to a switch unit (not shown) to switch on the battery power in the line 72 when the predetermined pressure difference is measured.

The fan unit 3 is mobile. The weight of the fan unit 3 exceeds 20 or 25 kg. Thus the fan unit 3 is not portable as defined herein. The fan unit 3 may optionally be provided with wheels.

The control unit 20 is in essence a mobile detection unit to which one or more sensors 6, 61, 62, 63 may be connected. Power is supplied to the control unit 20 from the battery 37 of the fan unit 3 via a control-unit low voltage power line 74, to give power to the sensors 61, 62, 63 connected to the control unit 20, for the operation of the control unit 20 and for providing power for a habitat low voltage control line 75 as will be further described below. The control unit may weigh less than 50 kg . The control unit 20 weighs less than 50 kg. The control unit 20 may weigh less than 25 kg. The control unit 20 may weigh less than 20 kg. The control unit 20 is portable as defined herein.

One or more of the sensors 61, 62, 63 are arranged outside the habitat 10, whereas at least one of the sensors 61, 62, 63 may be arranged inside the habitat 10. The number of sensors 6 may vary, and the number of sensors 6 may vary without departing from the scope of the invention. The sensors 61, 62, 63 are connected to the control unit 20 via sensor cables 71, 72, 73. The sensors 61, 62, 63 may be any sensors 6 for the detection of relevant parameters such as inflammable gas, air pressure, temperature, fire etc. At least one of the sensors 61, 62, 63 will always be a sensor 6 for the detection of inflammable gas when the control unit 20 is used in an environment where inflammable gas may be expected .

The control unit 20 comprises a switching unit 21 designed to control the supply of pressurized air, gas and/or power for tools for performing hot work inside the habitat 10. The switching unit 21 may be any suitable switching unit 21 arranged to turn on or off power to the habitat control line 75, i.e. turn off the power in the habitat control line 75 if any of the sensors 61, 62, 63 detects inflammable gas or any other irregularities, depending on the type of sensor 6 connected to the control unit 20. If any of the sensors 61, 62, 63 are detecting any inflammable gas or other irregularities, the power in the habitat control line 75 is cut by the switching unit 21 inside the control unit 20.

Hot work, such as sandblasting, welding, megging, grinding, cutting, chiselling, and other operations that may generate heat, open flame and/or sparks, may be performed inside the habitat 10 in zone 1 or 2, i.e. zones where such operations are prohibited without the use of a habitat 10. The hot work may require one of electrical power, pressurized air and welding gases. Hot work using pressurized air is indicated by reference numeral 17, and hot work using electricity is indicated by reference numeral 19.

Pressurized air for tools operated by pressurized air is introduced through a pressur- ized-air line 81, preferably from the pressurized-air system 8 of the facility, such as the offshore installation, onshore factory etc. involved. The pressurized air is controlled by means of a quick responding valve 83, such as a solenoid valve 83 operated from the control unit 20 via the low voltage habitat control line 75. The solenoid valve 83 is designed to be kept open by the electrical power from the habitat control line 75, and to automatically close the supply of pressurized air to air-driven tools when no electrical power is present in the habitat control line 75. The skilled person will understand that gas for welding or heating objects inside the habitat 10, which may be both an inflammable gas and oxygen, may be controlled by quick responding valves, such as solenoid valves similar to the solenoid valve 83 to stop an open flame if inflammable gas is detected by one of the sensors 61, 62, 63 or by the air-inlet gas sensor 60.

If electric tools are to be used inside the habitat 10, electrical power may be supplied to the habitat 10 via a power line 78, the electrical power being at a higher voltage normally used for professional electric tools, such as 240 or 480 volts. The power line may be connected to an approved high voltage terminal 77. A low voltage electrically controlled power switch 79 is connected to the habitat control line 75. The power switch 79, if present, is turned on by the current in the low voltage habitat control line 75 and is automatically turned off when there is no current in the habitat control line 75. Accordingly, if any of the sensors 60, 61, 62, 63 detect irregularities, the power switch 79 is returned to the off position to stop the power supply to the electric tools for hot work 19. The control-unit power line 74 is connected to the fan unit 3 for delivering electrical power, i.e. direct current (DC) from the battery 37 in the fan unit 3, to the control unit 20. The control unit 20 is connected to two or more sensors 61, 62, 63, and is arranged in connection with the habitat 10, i.e. either inside or outside the habitat 10. The number of sensors 6 may vary, depending on the need. Even though three sensors 61, 62, 63 are shown in the figures, the number of sensors 6 connected to the control unit 20 is at least one, and may be as many as found practical. Four sensors 6 are often found to be a suitable number.

When starting up the present habitat system, the fan 31 is started and the shutdown valve 33 is opened if the air-inlet gas sensor 60 indicates that the concentration of gas in the air-intake area is below a set limit of typically 10 % of the Lower Explosion Level (LEL), or 20 % of LEL, or any other limit set by authorities or company sta ndards, or preferably that no detectable concentration of inflammable gas is present in the air. The overpressure generated in the habitat 10 relative to the surrounding pressure is monitored, and as soon as the overpressure has reached a predetermined overpressure, e.g. 5 or 10 mm water column higher than the ambient pressure, a switch is tripped in the fan unit 3 for turning on the power in power line 74, to deliver power to the control unit 20.

As soon as the control unit 20 receives power through the power line 74, the sensors 61, 62, 63 are activated. Power in the habitat control line 75 is off. The power in the habitat control line 75 may be turned on by means of a switch (not shown), arranged on the control unit 20, as soon as the sensors 61, 62, 33 confirm that there is no gas above the predetermined level, which is the same level as that indicated for the fan unit 3 above. The current in the control line 75 will in turn open at least one of the solenoid valve 83 and the power switch 79 inside the habitat 10.

An alternative embodiment is shown in figure 2. In this embodiment the fan unit 3 is omitted and overpressure air is obtained from an air source 8' on the installation on which the habitat 10 is arranged. The control unit 20' will then include a battery 37' or be connected to a battery 37' for the operation of the control unit 20' and the units connected to it, i.e. such as sensors 61, 62, 63, solenoid valve(s) 83, switches 79, etc. A control unit 20' designed to be used without the electrical connection to a fan unit 3 as described with reference to figure 1, will be designed to have an overpressure- sensing unit, as e.g. described above for the fan unit 3 using a tube 13' for connecting the interior of the habitat 10 and the control unit 20'. Alternatively, one of the sensors 6 may be used to measure the overpressure.

The switch 79 and the solenoid valve 83 are in the embodiments shown in figures 1 and 2, positioned inside the habitat 10. In the embodiments shown in figures 3 and 4, the switch 79 and the solenoid valve 83 are positioned outside the habitat 10. Other embodiments are also possible, e.g. that the switch 79 is positioned inside the habitat 10 and the solenoid 83 positioned outside the habitat 10 or vice versa (not shown).

The different switching units mentioned above may be any suitable switching units, such as units based on relays, PLSs, or any other suitable switching units. Relays are presently preferred because of the simplicity thereof, the cost and the low power consumption.

The control unit 20, 20' and/or the fan unit 3 may also comprise optional equipment such as an emergency switch for manually shutting down the equipment connected to the control unit, and units for visual and audible alarm signals, such as a flashing light and an alarm horn. This may be performed by a fire guard 95 who is present in the vicinity of the control unit 20, 20'. The skilled person will understand that an optional emergency switch, optional flashing light, and/or optional alarm horn may be mounted on the control unit 20, 20' or fan unit 3, or may be connectable to the control unit 20, 20' or fan unit 3 via connectors not illustrated.

If gas of a concentration above the allowable concentration as discussed above is detected by the air-inlet gas sensor 60, the fan unit 3 will be shut down by cutting off the pressurized air or electrical power to the fan 31, and shutting the shutdown valve 33. Additionally, the power in line 74 is shut off, resulting in a loss of power in the habitat control line 75, which in turn results in any solenoid valve(s) 83 and/or power switches 79 controlled by the control unit 20 being closed. Loss of overpressure will have the same effect as loss of overpressure measured via the tube 13, causing the fan unit 3 to shut down as described. However, the shutting-down of the fan unit 3 due to the loss of overpressure is preferably somewhat delayed to avoid a shutdown of the system due to windy conditions causing a short and temporary loss of overpressure. The shutting-down of the fan unit 3 due to a loss of overpressure may therefore be delayed for e.g. 5, 10 or 30 seconds and be dependent on the overpressure not being re-established during said period. The same will apply to the alternative embodiment, in which overpressure air is received from the installation's air source 8' and the habitat system does not have a fan unit 3 of its own.

A detection of gas, or any other irregularities, by the sensors 61, 62, 63 connected to the control unit 20, 20' will only cut the power to the habitat control line 75 and, thus, cut power, gas and/or pressurized air to hot work inside the habitat 10. Accordingly, the overpressure will be maintained as it may be an advantage to continue the supply of overpressure air to the habitat 10 if gas is detected by any gas sensor 61, 62, 63 but not by the gas sensor 60 arranged at the air inlet 41 of the fan unit 3. Allowing the supply of overpressure air to maintain the overpressure in the habitat 10 if gas is detected by any other gas sensor 6, and no gas is detected in the air inlet 41, may make it possible to prevent gas ingress into the habitat 10 until hot work pieces are cooled sufficiently not to represent any danger with regard to ignition of the gas.

The skilled person will understand from the description above that, in its basic configuration, the present shutdown system 2 comprises the control unit 20 with sensors 6, habitat control line 75 and one or more solenoid valve(s) 83 and/or power switches 79 to control the pressurised air and/or electrical power for tools to be used inside the habitat 10. The shutdown system 2 preferably also comprises the fan unit 3 including the sensor 60, the power line 74, the fan 31 and the overpressure-air channel 4, if the shut down unit is to be used for a habitat 10 to be operated under internal overpressure relative to the surroundings.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb "comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a cla im. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.