JP2012172846A - Method for performing insertion/withdrawal of instrument in reservoir - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for performing insertion/withdrawal of an instrument in a reservoir, an air lock for performing the method, and the reservoir including the air lock.SOLUTION: The method includes a step providing a zone for interaction with a shuttle of a guide by using the shuttle for receiving the instrument and the guide for the shuttle in the instrument, in which the zone includes a tubular recessed part surrounding the shuttle; and a step maintaining a pressure in the tubular recessed part higher than a pressure of liquid held in the reservoir in conjunction with movement of the shuttle in a slide direction in the guide, in which maintenance under pressurization is achieved by injection of inert gas into the tubular recessed part. The tubular recessed part is defined in a lateral direction by an inner face of the guide and an outer face of the shuttle, and it is defined in a longitudinal direction by at least two contact zones in an upper side and a lower side between respective extension parts of the outer face of the shuttle and the inner face of the guide.

Description

  The present invention relates to a method for performing the insertion / removal of equipment in a reservoir, an airlock for performing such a method, and a reservoir with such an airlock.

  This method involves the introduction or removal of a low temperature reservoir, ie a high liquid level detector inside a reservoir containing a liquid at a low temperature (typically below −50 ° C.) with a top gas at a pressure above atmospheric pressure. Particularly adapted to enable. This method is also suitable for the introduction of other types of equipment such as cameras.

  Problems that arise in connection with the introduction or removal of such probes are related to ensuring the confidentiality of the reservoir. For example, in a reservoir for liquefied natural gas (or “LNG”), LNG is stored at about −165 ° C., and the upper gas of the reservoir is constituted by natural gas due to evaporation of LNG, The internal pressure that can be reached is several hundred hPa higher than the atmospheric pressure. The risk of leakage of very cold boil-off gas is present during the introduction or removal of equipment in the reservoir, at which time there is an ignition risk and on the other hand the operator risk associated with cold gas. Sex exists. Furthermore, it is possible for freezing to be configured to increase the size of the contact surface between the device and the reservoir.

  The object of the present invention is to overcome all or some of the above-mentioned drawbacks, i.e. the introduction / removal of the equipment inside the reservoir housing under pressure, in particular for low temperature combustible gases, for example. Is to propose a method for performing

The solution proposed by the present invention is a method for performing the insertion / removal of equipment inside a reservoir intended to contain a fluid under a pressure higher than atmospheric pressure,
In a method using a shuttle for receiving the device and a guide for the shuttle in the device through the reservoir wall, the shuttle is movable in a predetermined sliding direction within the guide, the method comprising: ,
A zone is provided for interaction of the guide with the shuttle, the zone comprising a tubular recess surrounding the shuttle;
In conjunction with the shuttle movement in the sliding direction in the guide, the pressure in the tubular recess is maintained higher than the pressure of the liquid contained in the reservoir, and the maintenance of the pressure is the injection of inert gas into the tubular recess. And the steps achieved by
The tubular recess is defined in the lateral direction by the inner surface of the guide and the outer surface of the shuttle, and in the longitudinal direction by at least two contact zones on the upper and lower sides between the outer surface of the shuttle and the individual extensions of the inner surface of the guide. It is a method characterized by being defined.

  The expression “method for performing device insertion / removal” means a method of placing the device in the reservoir or removing the device, or both in any order.

  The reservoir may in particular be a reservoir for storing LNG. Such a reservoir is at a temperature of about −165 ° C. and also contains natural gas (in the gaseous state) at a low temperature forming the top gas.

  This method allows introduction of the device into the reservoir or removal of the device for eg maintenance or replacement.

  The equipment can be of any type. The instrument collects information obtained about the interior of the reservoir or allows the work performed (including the use of probes) to be performed inside the reservoir. In particular, the device may be a detector for the presence of a liquid, for example a detector used for detecting the level in a reservoir. The device may be a camera.

  This method uses a shuttle that carries the equipment, which can be moved in a guide that penetrates the wall of the reservoir. The shuttle plays a role in protecting the equipment.

  As depicted by the solution of the present invention, the recess forms a delimited space (also referred to as “chamber” throughout this description).

  The resulting technical problem is solved by the interaction of the guide and the shuttle to form a chamber between the guide and the shuttle, which extends around the shuttle and when the shuttle moves, the pressure is Internally maintained at a pressure above the pressure inside the reservoir.

  The chamber may have a relatively small volume compared to the inner volume of the guide. The chamber may be reduced in the gap between the guide and the shuttle.

  In one embodiment, maintenance under pressure may be achieved by injection of an inert gas. The expression “injection” here means that the chamber is in fluid communication with a pressure source at a higher pressure than the chamber itself, and that an inert gas flows into the chamber in order to increase and maintain the pressure there. It means being placed. The chamber is a space that interacts on the passage of the gas contained in the reservoir, and the gas tends to escape to the outside through a gap space arranged between the shuttle and the guide. The chamber is at a pressure higher than the pressure inside the reservoir and higher than atmospheric pressure, and the inert gas leaks from the chamber toward the interior of the reservoir and from the chamber toward the exterior of the reservoir. Leaking outward of the gas contained in the reservoir is not possible because it must pass through the chamber.

  While playing a role in particular with regard to reservoir leakage, other sealing means with permanent properties, such as flange coupling assemblies or valves, for example, are temporarily released to form a passage for the shuttle in the guide In some cases, this dynamic stage using an inert gas may be permanently provided.

  The notation "inert gas" means a gas that is not dangerous for introduction into the reservoir or leakage to the outside.

  According to one particular embodiment, the surface of the guide defining the recess remains the same and the guide is fixed, while the surface of the shuttle defining the recess changes as the shuttle moves.

  In one embodiment, the inner surface of the guide defining the chamber comes into contact with the outer surface of the shuttle in the contact zone. The effect of the contact is to minimize any leakage of inert gas towards the reservoir or towards the outside. The amount of inert gas consumed is very small a priori. First, as a result of the approximation obtained, it is proportional to an excessive pressure, a duration of the stage, and a factor that decreases in proportion to the narrowness of the contact between the guide and the shuttle.

  The larger the gap between these two surfaces, the greater the leakage of inert gas from the chamber towards the interior of the reservoir or towards the outside air. In an advantageous manner, the guide and shuttle are shaped to minimize leakage. In any event, outward leakage through the gap between the guide and shuttle from inside the reservoir remains difficult as long as the pressure in the chamber is higher than the pressure inside the reservoir.

  In one embodiment, the inert gas includes nitrogen gas having a concentration of 99% or more by volume. Nitrogen is a frequently used gas for inactivation. Mixing with boil-off gas from LNG is not dangerous. In addition, boil-off gases often contain significant amounts of nitrogen. Possible leaks of nitrogen outside the reservoir are not hazardous in the atmosphere.

  In one particular embodiment, the pressure maintained in the recess is between 105% and 150% of the pressure of the fluid contained in the reservoir. By suppressing the pressurization in the recess, any leakage of inert gas towards the reservoir or towards the outside is minimized and the amount of inert gas consumed is also minimized.

  In one embodiment, the guide comprises at least two sealing gaskets arranged at the height of the individual extensions of the guide inner surface. The use of these seal gaskets allows the possibility of inert gas leakage from the chamber to the reservoir or outward to be largely ruled out. Furthermore, these sealing gaskets minimize as much as possible any leakage of natural gas towards the outside.

The present invention is an air lock for insertion / removal of equipment inside a reservoir intended to contain a fluid under a pressure higher than atmospheric pressure,
A guide intended to penetrate the wall of the reservoir;
A shuttle displaceable in a predetermined sliding direction within a bore in the guide, the shuttle comprising means (screws and bolts, welding or other means) for securing the instrument;
In the air lock equipped with this air lock,
A zone for interaction between the guide and the shuttle having a tubular recess surrounding the shuttle;
An inert gas inlet disposed in the tubular recess,
The tubular recess is defined in the transverse direction by the inner surface of the guide and the outer surface of the shuttle, and in the longitudinal direction, at least two contact zones on the upper and lower sides between the outer surface of the shuttle and the individual extensions of the inner surface of the guide. Is defined by

  Most of the elements of the airlock have been introduced in the previous description of the method according to the invention, and the description given with respect to the method also applies to the airlock.

  The guide comprises an internal bore intended to allow movement of the shuttle between at least one first position and a second position, in which the shuttle is partially or totally within the reservoir. The shuttle is arranged outside in the second position. The first position is the position where the device is inside the reservoir. In the second position, the instrument and shuttle are outside the reservoir.

  The chamber formed by the inner surface of the guide interacting with the outer surface of the shuttle comprises at least one inlet intended to be connected to the inert gas current, and the chamber is maintained at a pressure above the pressure inside the reservoir. Making it possible. In one particular embodiment, the inlet is located at the height of the inner surface of the guide.

In one embodiment, the shuttle is displaceable between a first position intended to engage the device within the reservoir and a second position intended to remove the device from the reservoir. The guide is
A first element disposed on the opposite side of the reservoir relative to a zone for interacting with the shuttle (3) to open and close the bore and to form a recess, The element closes the bore when the shuttle is in the first position and opens the bore when the shuttle passes from the first position to the second position;
A second element disposed on the side of the reservoir in relation to a zone for the guide to interact with the shuttle to open and close the bore and to form a chamber, the second element being A second element that closes the bore when in the second position and opens the bore when the shuttle passes from the second position to the first position;
Is further provided.

  The first element of the previous operation is typically a flange.

  For example, the second element is a full bore valve that engages within the valve when the shuttle passes from the second position to the first position, and when the shuttle is in the first position, the shuttle is within the valve. Remains engaged.

  In one embodiment, the outer surface of the shuttle comprises a mark, and from an observation point outside the reservoir, the mark is hidden by the guide when the shuttle is engaged in the second position, and the shuttle is in the second position. The mark is arranged so that the mark can be seen when the engagement is released. This mark is recognizable when the second element for opening and closing the bore is closed. The mark may be in the form of a shuttle or other signal. In fact, the distance between this mark and the tip of the shuttle located on the side of the reservoir is approximately the same as the distance between the second element and the opening of the guide on the opposite side of the reservoir. Also good.

  In one embodiment, the guide comprises at least two sealing gaskets located at the height of individual extensions of the inner surface of the guide.

  In one embodiment, the outer surface of the shuttle is cylindrical and does not have sharp edges in a given sliding direction.

  In one embodiment, the outer surface of the shuttle includes a circular base.

  When the shuttle is in the first position (or engaged position) and the device is inside the reservoir, the first element for opening and closing the bore in the guide, ie the airlock, guarantees a permanent airtightness. . The first element may be a flange that guarantees good airtightness in a permanent manner and may be removed to pull out the shuttle.

  The flange may comprise one or more sealing gaskets.

  The second element for opening and closing the bore in the guide can guarantee a permanent airtightness when the shuttle is in the second position (drawn position). This may be a full bore valve and shows the advantage that when opened, the shuttle can remain engaged in the valve.

  In one particular embodiment, the contact is improved by the presence of at least two sealing gaskets located at the respective extended day height of the inner surface of the guide in the contact zone between the inner surface of the guide and the outer surface of the shuttle, This guarantees a tight seal between the direction of the reservoir and the direction of the outside air.

  According to an advantageous embodiment, this cylindrical section does not have a concave or protruding sharp edge, especially in the sliding direction. In fact, such edges form corners or spots in the structure and any sealing gaskets. Therefore, the presence of an edge shows an advantage in terms of airtightness.

Finally, the present invention relates to a reservoir intended to contain liquefied natural gas or a natural gas top gas under a pressure higher than atmospheric pressure,
The above-mentioned air lock is provided, and the recess is in fluid communication with an inert gas source through an inlet, and the inert gas source has a pressure in the recess that is higher than the pressure of the upper gas contained in the reservoir. It is possible to maintain.

  Other features and advantages of the present invention will become apparent from the following description of embodiments, given in a non-limiting manner with reference to the accompanying drawings.

FIG. 3 shows an airlock and a reservoir according to the present invention. It is the figure which showed the air lock of FIG. 1 in detail. FIG. 3 shows elements of the airlock of FIGS. 1 and 2. FIG. 3 shows the steps of the method according to the invention. FIG. 3 shows the steps of the method according to the invention. FIG. 3 shows the steps of the method according to the invention. FIG. 3 shows the steps of the method according to the invention.

  For reasons of clarity, the dimensions of the different elements shown in these figures are not necessarily proportional to the actual dimensions. In the figures, the same reference numerals correspond to the same elements.

  Shown in FIG. 1 is an airlock according to the present invention. This airlock comprises a guide 4 fixed to the dome-shaped roof 1b of the reservoir 1 for liquefied natural gas (or “LNG”) 1a. The reservoir is partially illustrated. The shuttle 3 is in place and is engaged in the storage container. The shuttle 3 utilizes a bore 5a provided in the guide 5 in a predetermined direction 5, in this case vertically. The shuttle penetrates the second roof 1c of the reservoir, which contributed to the insulation of the LNG 1a and the upper gas from the higher parts of the reservoir 1. An industrial quality nitrogen source 6b is also shown and can flow to the inlet 6a into the chamber formed by the guide and shuttle.

  The shuttle 3 has a generally tubular shape with a rounded tip on the reservoir side. Assembled around this section is equipment 2, which is secured to the shuttle along with fastening means such as screws and bolts, welding or some other means. This device 2 may be a detector for the presence of LNG, for example equipped with a thermocouple or a slave float. This device may be a camera or any other element for collecting information about the reservoir. This device may be an element intended to play an active role in the reservoir. The shuttle is potentially displaceable in a predetermined direction 5. In this position of the shuttle, a leak-free condition of the reservoir occurs at the height of the flange 4d which closes the guide 4 from the opposite side of the high section reservoir.

  FIG. 2 shows an air lock formed by the guide 4 and the shuttle 3. The guides are fixed in succession alternately and consist primarily of four sections forming the walls of the guides and bores 5a.

  Element 4c is intended to be fixed to the wall of the reservoir, for example the roof 1b. Element 4c passes through this wall to form a passage for equipment 2 carried by shuttle 3.

  Section 4b comprises an opening and closing element 4e, which may be a full bore valve. This element may close the bore 5a in a sealing manner when the shuttle is in a position that is no longer engaged within the element.

  The element 4a is intended to interact with the shuttle to form the chamber 6.

  The opening / closing element 4d is arranged at the opposite end of the reservoir. This element closes the bore 5a in a sealing manner, in particular when the shuttle is at least partially engaged in the reservoir, i.e. when the shuttle extends beyond the guide on the side of the element 4c. It is possible.

FIG. 3 shows an enlarged view of the element 4 a belonging to the guide 4. In the presence of the shuttle 3, the inner surface 5 b of the element 4 a of the guide 4 interacts with the outer surface 3 a of the shuttle 3, in this case comprising a tubular recess 6 surrounding the shuttle 3,
At least two contact zones laterally by the inner surface 5b of the guide and the outer surface 3a of the shuttle and between the outer surface 3a of the shuttle and the individual extensions (8a, 8b) of the inner surface 5b of the guide Depending on the vertical direction,
Is defined.

  Accordingly, the recess 6 forms a partitioned space and is also referred to as a “chamber” throughout the description of the present application.

  However, the chamber exists only if there is a shuttle in this section of the guide. The chamber is a gap space having a certain volume between the guide and the shuttle. This chamber interacts in the bore with respect to the gas, which may move outward from the reservoir between the guide and the shuttle.

  The chamber 6 is provided with an inlet 6a intended to connect the chamber to an inert gas source 6b via a duct 6c. The inert gas may be nitrogen having a purity of 99% or more by volume, and preferably 99.99% or more by volume. Therefore, it is possible to maintain the internal pressure of the chamber above the internal pressure of the reservoir during the use of the shuttle at a certain stage. In general, the objective is to achieve a pressure between 105% and 150% of the reservoir and to prevent leakage from the reservoir outward. LNG reservoirs are typically at a relative internal pressure of about 100-300 hPa, or an absolute pressure of about 1.1-1.3 atmospheres.

  In order to improve the leakage of the chamber 6, two O-rings or lip seals 7a, 7b are arranged in a zone that closes the chamber between the inner surface of the guide and the outer surface of the shuttle.

  Having a rounded shape with no sharp edges (protrusions or depressions) in the sliding direction 5 is an advantage with respect to the shuttle. Indeed, such an edge reduces hermeticity and increases the consumption of inert gas in order to maintain the desired chamber internal pressure.

  4A-4D illustrate the different stages of the present invention, which uses a preoperative airlock to remove the device from the LNG reservoir and then return the device into the LNG reservoir. is there. The reservoir is symbolized by a dome-shaped roof 1b. The airlock guide 4 and the shuttle 3 are shown in a stylized manner. The chamber 6 is connected by a duct 6c to an inert gas source not shown here.

  In FIG. 4A, the shuttle is shown in the first position and the instrument is engaged in the reservoir. The flange 4d is in place, which ensures the tightness of the reservoir. The full bore valve 4e is open and the shuttle is shown through the valve. The shutoff valve for the duct 6c is closed. This is the standard operating position of the device 2 in the reservoir.

  In FIG. 4B, the device is about to be removed. The chamber 6 defined by the upper and lower contact zones between the outer surface of the shuttle and the individual extensions (8a, 8b) of the inner surface of the guide is added by opening the valve of the duct 6c. Placed under pressure, this pressure is controlled to a value above the reservoir pressure, preferably between 105% and 150% of the reservoir pressure. It is therefore possible to remove the flange 4 and slide the shuttle upwards, and the chamber 6 is airtight in the reservoir in the sense that the gas contained in the reservoir cannot escape. Guarantees sex.

  In FIG. 4C, the detection of the visible mark 3b present on the outer surface of the shuttle contributes to the confirmation that the shuttle is sufficiently raised in the guide. In this position intended to remove the device, the valve 4e is disengaged, but the valve 4e may still be closed. At that time, as long as necessary, the tightness of the reservoir is guaranteed, for example for the repair or replacement of the equipment. At that time, since the work is undertaken by the valve 4, it is possible to stop maintaining the chamber 6 under pressure.

  In FIG. 4D, the equipment maintenance is complete and the equipment is about to be returned to the reservoir. The chamber 6 is again placed in the first position under pressure. At that time, the valve 4e is opened. At that time, the shuttle is sliding toward the bottom. The shuttle returns the instrument into the reservoir. When the shuttle is fully lowered to the first position, the flange 4d returns and closes the reservoir again. Here, it is possible to stop maintaining the chamber 6 under pressure. Here, the starting position is re-established, the equipment is repaired or replaced, and the tightness of the reservoir is always guaranteed.

DESCRIPTION OF SYMBOLS 1 ... Reservoir, 1a ... Liquefied natural gas (LNG), 1b ... Roof, 1c ... Second roof, 2 ... Equipment, 3 ... Shuttle, 4 ... Guide, 5a ... bore, 6 ... chamber (tubular recess), 6a ... inlet, 6b ... inert gas (nitrogen) source, 6c ... duct, 7a, 7b ... lip seal

Claims (13)

A method for performing insertion / removal of equipment (2) inside a reservoir (1) intended to contain a fluid (1a) under a pressure higher than atmospheric pressure,
Using a shuttle (3) for receiving the device and a guide for the shuttle within the device, wherein the shuttle is movable in a predetermined sliding direction (5) within the guide; The method
Providing a zone for interaction of said guide (4) with said shuttle (3), said zone comprising a tubular recess (6) surrounding said shuttle (3);
In conjunction with the operation of the shuttle in the sliding direction (5) in the guide, the pressure in the tubular recess (6) is maintained higher than the pressure of the liquid contained in the reservoir, and under pressure The maintenance of is accomplished by injecting an inert gas into the tubular recess (6),
The tubular recess (6) is defined in the lateral direction by the inner surface (5b) of the guide and the outer surface (3a) of the shuttle, and in the longitudinal direction, the outer surface (3a) of the shuttle and the inner surface (5b) of the guide. ) Defined by at least two upper and lower contact zones between the individual extensions (8a, 8b).   The method according to claim 1, wherein the inert gas contains nitrogen gas having a concentration of 99% or more by volume.   The method according to claim 1 or 2, characterized in that the pressure maintained in the front and rear (6) is between 105% and 150% of the pressure of the fluid contained in the reservoir.   2. Method according to claim 1, characterized in that the guide comprises at least two sealing gaskets (7a, 7b) arranged at the height of the individual extensions (8a, 8b). An air lock for insertion / removal of equipment (2) inside a reservoir (1) intended to contain a fluid (1a) under pressure higher than atmospheric pressure, the air lock comprising:
A guide (4) intended to penetrate the wall of the reservoir (1b, 1c);
A shuttle (3) displaceable in a predetermined sliding direction inside the bore (5a) in the guide (4), the shuttle (3) having means for fixing the device (2) )When,
In the air lock comprising:
A zone (4a) for interaction between the guide (4) and a shuttle (3) comprising a tubular recess (6) surrounding the shuttle (3);
An inert gas inlet (6a) disposed in the tubular recess (6),
The tubular recess (6) is defined in the lateral direction by the inner surface (5b) of the guide and the outer surface (3a) of the shuttle, and in the longitudinal direction, the outer surface (3a) of the shuttle and the inner surface (5b) of the guide. ) Defined by at least two upper and lower contact zones between the individual extensions (8a, 8b). The shuttle is displaceable between a first position intended to engage the device in the reservoir and a second position intended to remove the device from the reservoir. ,
The guide (4)
In order to open and close the bore (5a) and to form the recess (6), the reservoir (in relation to the zone (4a) for the guide to interact with the shuttle (3) ( 1) a first element (4d) arranged on the opposite side of 1), said first element (4d) closing said bore when said shuttle is in said first position, and said shuttle being said A first element (d) that opens the bore when passed from a first position to the second position;
In order to open and close the bore (5a) and to form the recess (6), the reservoir (in relation to the zone (4a) for the guide to interact with the shuttle (3) ( A second element (4e) arranged on the side of 1), said second element (4e) closing said bore when said shuttle is in a second position, and said shuttle being in said second position A second element (4e) that opens the bore when it passes from the first position to the first position;
The air lock according to claim 5, further comprising:   The airlock according to claim 6, wherein the first element (4d) is a flange.   The second element (4e) is a full bore valve, and the shuttle engages in the valve when the shuttle passes from the second position to the first position, and the shuttle is in the first position. The airlock according to claim 6 or 7, wherein the shuttle remains engaged in the valve.   The outer surface (3a) of the shuttle is provided with a mark (3b), and from the observation point outside the reservoir (1), the mark is guided by the guide when the shuttle is engaged with the second position. The airlock according to claim 8, wherein the mark is arranged so that the mark is visible when the shuttle is disengaged from the second position.   10. The guide according to claim 5, wherein the guide comprises at least two sealing gaskets (7a, 7b) arranged at the height of the individual extensions (8a, 8b). Air lock as described in the section.   11. The airlock according to claim 5, wherein the outer surface (3a) of the shuttle is cylindrical and does not have a sharp edge in the predetermined sliding direction (5).   The airlock according to claim 11, characterized in that the outer surface (3a) of the shuttle comprises a circular base. In a reservoir (1) intended to contain liquefied natural gas (1a) or the upper gas of natural gas under a pressure higher than atmospheric pressure, the reservoir comprises:
The air lock according to any one of claims 5 to 12, wherein the recess (6) is in fluid communication with an inert gas source (6b) through the inflow port (6a). The reservoir (1), wherein the active gas source can maintain the pressure in the recess higher than the pressure of the upper gas accommodated in the reservoir.

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