NO824426L - HYDRAULIC UNDERWATER EQUIPMENT CONTROL SYSTEM. - Google Patents

Description

The invention relates to a control system, more precisely a hydraulic control system for operating the valves on an underwater "Christmas tree" from a remote location.

It has long been common to extract oil and/or gas from sources on the seabed. In the past, however, such sources have mainly been drilled at relatively shallow depths. With the increasing demand for oil and/or gas, it has been drilled with constant increasing frequency at greater and greater depths.

As soon as the drilling of such sources on the seabed at these relatively great depths has been successfully carried out, i.e. as soon as the oil or gas has been found, one still has the problem of getting the oil or gas out of the borehole. For this purpose, it is known to place at the top of the borehole a structure with pipes and valves which is usually called "a Christmas tree". Such a "Christmas tree" is integrated with the source, so that it can be used to control the production of oil or gas from the source. For this purpose, the "Christmas tree" suitably provided with various valves.

Consequently, there is a need to establish control with these valves. Due to the fact that the "Christmas tree" and thus also the valves on it are located on the seabed, which • lies at a considerable water depth, the control of the valves is generally carried out from a remote location. This in turn necessitates the use of control equipment, which is effectively independent of the fact that the control is to take place over a certain distance, for example between the top of the borehole where the "Christmas tree" is placed and a remote location from which the control of the valves on the "Christmas tree" must be carried out.

In addition to being able to carry out the necessary operations on the valves on the underground "Christmas tree", a control system to be selected for use for this purpose should also have certain other characteristics. For example, such a control system should be able to work without failure also in the cases that it is exposed to intensive operation, That such characteristics are,' desirable, should be clear to everyone when one considers the position of the valves that the control system will affect and when one takes into account the difficulties that exist when repairing the control system at the place where the valves exists if such a need were to arise. Another property that is desirable for such a control system is related to the costs of the system. Because the control system must be able to operate over a considerable distance, as well as at great water depths, it is desirable that the equipment used to carry out the control function over the valves on the "Christmas tree" are both relatively simple and have a relatively low price.

DESPITE the fact that the control system, which is chosen for the purpose of use described above, should be relatively operationally reliable, there is still a need to carry out normal maintenance. Consequently, the ease with which such maintenance can take place, both with regard to the time consumption and the effort that must be exerted for this purpose, an important factor for the user. For this purpose, when drilling at sea at relatively shallow depths, it has been possible -:and advantageous to'use divers to carry out the necessary maintenance work and/ or repairs to the equipment placed on the seabed, including such equipment parts as the "Christmas tree" itself, the associated valves, etc., as well as the control system which stra-

from the "Christmas tree" and to a control center at the sea surface, from where the control of the valves on the "Christmas tree" takes place. However, as the production sources are drilled with increasing frequency at greater and greater depths, it is no longer possible to use divers to carry out the maintenance and/or repair work referred to above. Instead, a need has arisen for the use of control systems that have ever-increasing reliability, as well as control systems that are even easier to manufacture.

Attempts have been made with varying degrees of success,

on creating new and better forms of control over the production of oil or gas from underwater oil sources. There are thus known different forms of control systems that are used for remote control of "Christmas trees". These are, as mentioned above, out-

met to be placed on oil or gas wells to control the flow out of the wells. They usually comprise a series of vent-

equipped with hydraulic triggers for opening and closing the valves. For this purpose, the hydraulic triggers will

pressurizing a hydraulic medium causes the valve to either open or close depending on the position of the valve prior to the pressure supply. Then, when pressure is relieved on the hydraulic triggers, the valves will take the other position, d. v. p. f is returned to its original position. If the valve was previously closed, it will therefore be moved from a closed position to an open position when the hydraulic triggers are activated, and when the pressure is relieved, they will return from an open to a closed position. If the valve on the

hand was open, correspondingly the opposite will happen.

In general, known forms of underwater control systems can be categorized according to the way the activation of the hydraulic triggers on the valves on the "Christmas trees" is carried out. It can thus be said that there are underwater control systems that can be classified into the following categories: Direct hydraulic systems, sequence controlled hydraulic systems, electro-hydraulic systems and composite (multiplex) electro-hydraulic systems. A more detailed account of the control system, which is called a sequence-controlled hydraulic system above, will be given below.

A sequence-controlled hydraulic system is a system where it

with the help of a pilot line, specific hydraulic pressure levels are created, which correspond to specific operating conditions for a "Christmas tree", and these specific pressure levels are used to control the operation of the valves associated with the "Christmas tree". Known forms of sequence-controlled hydraulic systems have all had one or other clear disadvantage or weakness. They have particularly had problems with maintaining sufficient reliability through simple design, and in that way have in economic operation both with regard to system costs and operating costs.

In general, it can be said that all known forms of sequentially controlled hydraulic systems use some form of valve control designed to cooperate with the valves on the "Christmas tree". More specifically, all known sequentially controlled hydraulic systems use a design that requires a pressure bias of the valve control used. During operation,

which requires the use of a biasing pressure, it is however a disadvantage that an additional hydraulic line is required between the "Christmas tree" and the control center on the surface, from which the control of the valves on the underwater "Christmas tree" takes place. The need for a

such an additional hydraulic line is disadvantageous in terms of cost. Examples of known sequence controlled hydraulic systems that require a bias pressure have been available from the Hyderil Company. In US patent 3,993,100 another form of sequence controlled hydraulic system is described. A system is shown that does not require a separate hydraulic line to create bias on the valve control that the system uses. Instead, an underwater regulator device is used to create the required bias pressure. Although a system avoids the costs associated with having a hydraulic line between the "Christmas tree" and the control center, this system still has its disadvantages. More specifically, these in the use of an underwater control device. Such control devices have previously been shown to be unreliable. Thus, they have shown a tendency to be subject to drift and pressure variations.

due to this uncertainty, the biasing pressure to which the valve control in the system is exposed can change, so that erroneous biasing forces occur which can thus lead to misdirection, i.e. cause the product flow from the "Christmas tree" to which the valve is connected to be misdirected.

Another known form of sequence-controlled hydraulic system has been supplied by Cameron Iron Works. In this system, the biasing of the valve control has been dependent only on using the supply pressure of the hydraulic medium. Although this way of creating a biasing pressure for the valve control eliminates both the need in order to run an additional hydraulic line from the surface down and to make use of an underwater control device, the system is very dependent on the existence of a very stable supply pressure. This dependence creates disadvantages because a power requirement at the seabed together with the presence of the normal limitations the hydraulic supply lines can cause a pressure drop on the supply line, whereby the biasing pressure for the valve control is created, these pressure drops can in turn create uncontrolled variations in the biasing force and in this way cause mismanagement, i.e. incorrect management of the flow from the borehole.

Another known type of hydraulically actuated control system has been provided by FMC Corporation. Although this system is without the disadvantages of the described known sequentially controlled hydraulic systems, it does not utilize valve controls that are sequentially controlled and which respond to predetermined pressure levels created in a pilot line. This system cannot therefore fulfill the need for a sequence-controlled hydraulic system which has been shown to exist, and which is simple and reliable and at the same time as affordable in acquisition and operation as desired.

The main purpose of the invention is therefore to create a control system for an underwater "Christmas tree", which can be operated as a sequentially controlled hydraulic system, with valve controls that can be operated sequentially; - as a reaction to the existence of certain predetermined pressure levels in a pilot line.

The system should be designed so that it minimizes the number of control cables to be routed from the control center downwards and the number of control valves required for operation of the system to a minimum. At the same time, the system must be flexible enough to allow for a number of different operating programs for the "Christmas tree" to be controlled.

It is desirable that the valve control has a narrow dead band and that it allows looping of shuttle valves between the valve controls and the valves.

It is also a purpose of the invention to create a new and improved control unit for sequential operation, which can be placed in or on top of the so-called "Christmas tree".

According to the invention, the main purpose can be achieved by designing the control system in accordance with the characterizing part of patent claim 1.

Further advantageous features of the invention appear from the subclaims, as these features each contribute to giving the system according to the invention certain advantages.

The invention will be described in more detail below with reference to the drawings, where: Fig.1 shows a schematic diagram of an underwater system

for production management, designed in accordance with the invention,

fig.2 shows a flow diagram for the valve control which

included in control systems according to the invention,

fig.2a shows a schematic diagram of an underwater "Christmas tree" of the type which is particularly suitable to be controlled by the valve control in the diagram in fig.2,

fig.2B is an appropriate operating program, shown in tabular form,

for an underwater "Christmas tree" of the kind that is particularly suitable

for control using the valve control in fig.2,

Fig. 3A and 3B, which belong together, show sections through a four-

part of a new valve for sequence control which is particularly suitable

for use in connection with the present invention, with certain parts removed,

fig.4 shows a schematic representation in section of a first embodiment of a low-friction, double sealing element calculated for use in the valve according to fig.3A and 3B,

fig.5 shows a schematic section through a second embodiment of such a sealing element, which is also intended for use in the valve in fig.3A and 3B,

fig.6 shows an axial section in schematic representation through

a valve for sequence operation, designed as shown in Fig. 3A and 3B,

Fig. 7 shows a side view, partially sectioned, of a spring element with constant force, which is particularly suitable for use in a one-valve as shown in Figs. 3A and 3B,

fig.8 shows a plan view with some parts cut away of such a spring element with constant force, which is also intended for use in a valve as shown in fig.3A and 3B, while

Fig. 9 shows a section in schematic representation through an intermediate valve intended for use together with the valve according to Figs 3A and 3B.

In fig.l there is shown a schematic diagram for an underwater system for production control, designed in accordance with the invention and designated generally by reference number 10. It is not necessary to give a detailed description of the diagram in fig.1 in order to understand the essential aspects of the invention. However, a general description of the main components of this system 10, as shown in fig. 1, shall be given. The control system 10 is designed to carry out control from a location at the surface, over the flow of emissions from an underwater oil or gas source. The control system 1) comprises valve control means generally denoted by reference number 12, which is shown placed on top of a "Christmas tree" 14. The underwater system 10 is connected to a control center 16 at the surface, which is usually placed on a fixed sea platform, by means of a number of hydraulic control lines. The number of hydraulic control lines required for this purpose is in the example four, i.e. lines 18, 20, 22 and 24. Three of these lines, d .v. p. those designated with reference numbers 20,22 and 24 are intended for use while line 18 is intended to be a spare line between the control center 16 and the valve control 12.

With regard to the three hydraulic control lines 20, 22 and 24, one of these, in fig.1 24, is calculated as a supply line.

Hydraulic working medium under pressure is pumped through this

from the control center 16 to the valve control 12. The working medium flowing through the line 24 is supplied to the valve control 12 to provide hydraulic power to trigger the valves on the "Christmas tree" by means of the valve control 12 as described below. The valve control 12 causes the individual valves to open or close, and in that way release working medium to or away from the valve releases on the "Christmas tree". Another of the three lines, namely line 20, is a pilot line, which opens and closes the individual valves in the valve control 12, when a predetermined pressure is established in the line 20. For this purpose, the pressure in the hydraulic working medium in the pilot line 20 is raised or lowered to control the individual valves in the valve control 12. The last of the three lines, i.e. the line 22, is used to provide hydraulic working medium for and to control a safety valve on the seabed which is controlled from the surface (designated SCSSV). This is commonly used in underwater oil extraction and is designated in the figure with reference number 26. By connecting a control system 10 as shown in fig .l, the safety valve 26 is controlled independently of the valve control 12. It can, however, be controlled from the valve control 12, without this violating the basic idea of the invention. Finally, in connection with the control system 10 shown in Fig. 1, it should be mentioned that the dashed lines with reference number 28 shall represent electrical connections that extend between the control center 16 and various maneuvering components in the control system 10.

In fig.2 in the drawing, a flow diagram for the valve control 12 is illustrated.1 additionally, 2A shows a schematic diagram for a "Christmas tree", generally designated by reference number 30, of the type that is calculated to be used in the control system 10 in fig.l. In fig.2B is the illustrated in tabular form an actual operating program, generally denoted by reference number 32, for the "Christmas tree" 30 in fig. 2A.

Description of the valve control flow diagram 12

in fig.2, does not need to be complete to understand the basic idea of the invention. Therefore, only a general description of the main components in fig.2 should be given. shown in fig.1 and which serves to feed hydraulic working medium to the safety valve 26. As shown in fig.2, a quick-release valve 34 of an appropriate, known type is inserted into the supply line 22. The flow diagram in fig.2 also shows

the pilot line 20 and the supply line 24 for hydraulic working medium, which is also shown in fig.l.

As can be seen from fig. 2, the pilot line 20 and the supply line 24 are both led to a series of five valves 36, 38, 40, 42 and 44 for sequential operation. According to the relevant operating program 32 for the "Christmas tree" 30, each of these valves 36,38,40,42 and 44 are three-way, two-position valves which are normally closed. Although five such valves are shown at the valve control 12 in fig.2, this number can be both lower and higher. The number of valves 36, 38, 40, 42 and 44 which are used in the valve control 12 is a function of the number of valves on the "Christmas tree" 30 which it is desirable to man-over. For this purpose, the triggers of six such valves are illustrated in fig.2, namely the triggers 46,48,50,52,54 and 56,

which is thus associated with the relevant "Christmas tree" 30. To clarify the functional description of the valve control 12 that will be given below, these six valve triggers can be further characterized as follows: The triggers 46 and 48 are each associated with a valve which is characterized by the "PM" trigger 50 is associated with a valve marked "PW", trigger 52 is associated with a valve marked "AM", trigger 54 is associated with a valve marked "AW" and trigger 56 is associated with a valve marked "XO". Finally, a pair of intermediate valves 58 and 60 are inserted into the valve control 12, which will be described in more detail. Each of the intermediate valves 58 and 60 is formed by a normal open, three-way, two-position valve. The intermediate valve 58 is inserted into the line to the trigger 50 for "PW"- the valve, while the intermediate valve 60 is inserted into the line to the trigger 56

for the "XO" valve.

The valve control 12 as shown in fig.2 and the operating program 32 indicate preferred embodiments, but there is the possibility of a number of variations in the operating program based on differences in the structure of the individual "Christmas trees" as well as on differences in the operating conditions required by the individual users. it is therefore clear that any control system, e.g. the system 10 in fig.1, is chosen so that it has the ability to be varied with respect to the operating program so that it can be adapted without the system having to be subjected to significant transformations.

Based on the control system in fig.1 in general and the valve control 12 in particular, as it is illustrated in fig.2, flexibility in the sense that the system has the ability to carry out different operating programs for the "Christmas tree" it is connected to, is mainly achieved in the control system 10 due to the fact that the valves 36,38,40,42 and 44 can be used to form the variants in the operating program 32, as shown in Fig. 2B. The operating program 32 in Fig. 2B is designed so that it has six operating states designated by the reference numbers 62,64,66,68,70 and 72.Each of the six horizontal lines corresponds to a determined operating condition, e.g. so that state 1, which is indicated by reference number 62, is identical

for

meaning with the operating state in the "Christmas tree" 30 which is called "OFF", etc. the valves 36,38,40,42 and 44 control the states 62,64,66,68,70 and 72 in the shown operating program 32 depending on the pressure on the corresponding valve's outlet opening when a predetermined pilot pressure is reached in the pilot line 20. As shown in Fig.2,

will triggers that are directly connected to the valve's output, i.e. as the release 54 which is connected directly to the output of the valve 36 is kept open during the entire program.

The flexibility of the system for the control system 10 in Fig. 1 in general and the valve control 12 in Fig. 2 in particular is improved by the use of a return piston shown with an opening marked G for all valves 36, 38, 40, 42 and 44. 1 Fig. 2 is these stamps are designated with reference numbers 36a, 38a, 40a, 42a and 44a respectively. Pressurized, each of these pistons 36a, 38a, 40a, 42a, 44a will cause the respective valves 36, 38, 40, 42 or 44 to return to the closed position after they have first been opened by the respective pilot pistons in response to the application of a certain pressure level in the pilot line 20. Generally, the return pistons 36a, 38a, 40a, 42a, or 44a will be used when one of the valves in the "Christmas tree" 30 in accordance with the operating program 32 is to be opened and then closed again only once during the program. For example, the trigger 52 of the "AM" valve ("annular-master") in the flow diagram in fig.2, in accordance with the operating program 32 in £ig.2B, should be opened in state 4, i.e. the condition indicated by reference number 68 1 £ig.2B, and then closes in condition six, i.e. the condition indicated by reference number 72. To carry out this part of the program 32

the trigger 52 is connected to the output from the valve 40 and the additional opening for this valve, with the return piston 40a,

is connected to the output of valve 44.

Because modes of use, where there are several changes from closed to open state during operation, the flexibility of the system 10 is maintained by using intermediate valves, more specifically the intermediate valves 58 and 60 in Fig. 2. These valves are inserted into the lines that extend between the output of one of the valves 36, 38, 40, 42 and 44 and the respective triggers 46, 48, 50, 52, 54 or 56 which are correspondingly connected. With the operating program 32 shown in fig. 2B, such a case exists. The trigger which is associated with the valve for the production line (the "PW" valve)

to the "Christmas tree" 30, it is required that this valve is first opened in state 2, i.e. the state designated by reference number 64 in fig. 2B, then closed in state 4, i.e. the condition denoted by reference number 68, then reopened in condition 5, i.e. the state designated with reference number 70, and finally closed in state 6, i.e. the condition denoted by reference number 72. The return piston enclosed in this valve cannot perform as

many changes. Consequently, there is a need for an intermediate valve, e.g. the valve 58 in fig. 2, which can be opened and closed by different pilot valves connected to the correct outlet from the valve. For this purpose, the intermediate valve 58, as shown in fig. .2, connected through an output line 74 to the trigger 50, and is connected by a line 76 to the output of the valve 40, with a line 78 to the output of the valve 42 and with a line 80 to the output of the valve 44. The working medium that flows through the lines 76, 78 and 80 from the valves 40, 42 and 44 respectively, are at different pressure levels, to cause the necessary movement of the various pilot pistons in the intermediate valve 58 to achieve the desired openings and closings of the trigger 50. It should be clear from this , that by using only two types of active components, i.e. the sequential operation valves 36,38,40,42 and 44 and the intermediate valves 58 and 60, it is possible to achieve any combination of closings and openings found in an operating program, for example the program 32 in fig.2B,

which is designed to be used to control the valves on the "Christmas tree".. As shown above, it is necessary that the number of changes that each valve actuator will carry out is determined and that a decision is made as to whether a return piston alone will be sufficient to satisfy the requirement for this number of exchanges, or an intermediate valve is necessary. The latter

"from*

step is to obtain the necessary connections^the return piston ,d. v. p. The G opening to the valves, and from;;; the pilot pistons in the intermediate valves to the outputs of the correct valves.

The use and construction of the sequential operation valves 36, 38, 40, 42 and 44, which are used in the valve control 12 in fig. 2, will be described with reference to fig. 3A, 3B and 6 in the drawing. Fig. 3A and 3B together constitute a four-part section through one of the valves 34, 38, 40, 42 and 44 in Fig. 2, while Fig. 6 is a schematic representation in section through such a valve. The valve in Fig. 3A

and 3B is assumed to be the valve 38 in fig. 2, and it has a main part, which is generally denoted by reference number 81 and which has a bore 82. The bore 82, which is generally cylindrical, extends along the longitudinal axis of the main part 81. A port or slide 84, which comprises several, e.g. four sealing elements 86, as shown in the illustrated embodiment, is conveniently stored in the bore 82 for movement in its axial direction. A spring with constant force, in Fig. 3A provided with reference numbers 88, is appropriately accommodated in a spring housing 90 which for this purpose is arranged in the main part 81, so that the slide 84 is biased to the left in fig.3A. Y further bias is applied to the slide 84 with the help of the working medium which is supplied to the valve 38 through a supply opening 92. This extra pre-tension is created by the effect of the pressure in the hydraulic working medium which acts in the annular space which is delimited by the sealing elements 94 and 96. The significance of this extra pre-tension, which is exerted on the slide 84, will be described in more detail below in connection with a description of an option for rapid exchange that exists

at valve 38.

As regards the mode of operation of the valve 38, when a pilot medium is supplied under pressure to the main part 81 through an inlet opening 98, an influence will occur on a pilot piston 100, which has a sealing element 102 in a part of the bore which is denoted by reference number 82a , and a force is thus created to the right in fig. 3A. When the pilot pressure rises, a force greater than the spring force 88 added to the frictional forces on the seals 94, 96 and 102 as well as the frictional forces from the sealing elements 86 will develop,

which causes the slide 84 to move to the right in fig.3A.

When pressure medium enters the main body 81 through the inlet opening at the return piston shown in dashed lines at 104 in 3A and is pressed over the annular return piston 106, a force is developed which is greater than the force developed by the pilot piston 102. Accordingly the slide 84 in the valve 38 will again be moved to the left in fig.3A. The outlet opening, through which the working medium leaves the valve 38, is denoted by 108 in fig.3A. It is important to note here that the valves 36,38,40,42 and 44 for

operation of the valve control 12 in fig. 2 changes in response to different pressure levels on the pilot pressure in the pilot line 20. This is achieved by the fact that the individual valves 36, 38, 40, 42 and 44 are

seen with pilot pistons of different diameters. This means that the diameter of each individual pilot piston in the valves 36,38,40, 42 and 44 is appropriately chosen so that they react to the force applied when the level of the pilot pressure in the line 20 reaches a certain value.

An advantageous feature that each of the valves 36,38,40,42 and

44 have, is that they have a narrow dead band.1 this connection is "dead band" the difference in the pilot pressure that causes the valve to switch from open to closed position when the pilot pressure is increased together

similar to when the pilot pressure is lowered. It can be shown that the dead band is a function of both the frictional forces in the valve and the spring constant of the bias spring. The valves 36, 38, 40, 42 and 44 used in the control system 10 according to the invention represent a significant improvement compared to known sequence operation- valves when it comes to the deadband. Much of the reason why this is so small has its cause in the use of sealing elements as shown at 86 in fig.3A,

with low friction and also in the use of a compression spring with constant force, as shown at 88 in fig.3A.

A further advantageous feature of the valves 36,38,40,42 and 44 lies in their ability to be quickly changed. This feature contributes

to help the slide<1> to move in both directions of movement. The advantage achieved by this is that positive switching of the valve is ensured and that a slow and stuck slide is prevented during switching. This feature of the valve can best be explained with reference to fig. 6. This is a schematic representation of the valve 38.

They share at the valve 38 which is common to figures 3A and 3B

and fig. 6, are given the same reference number. In fig. 6, the following dimensional ratio should be pointed out. The sealing member 102 always has a larger diameter than the sealing member 94 and the sealing member 94 always has a larger diameter than the sealing member 96. With this ratio as a starting point, when the slide 84 is moved towards the right in fig.6, the valve 38 is opened to lead working medium through the outlet opening 102

from the supply 92 to the valve actuator 48 to which the valve 38 is connected in accordance with the flow diagram in Fig. 2. When this occurs, i.e. when working medium is released to the trigger 48, a temporary pressure drop occurs in the supply line 92. This redu-

sees the biasing force applied to the annular space between the sealing members 94 and 96, i.e. the biasing force that develops in this area. This reduction in biasing force,

has the effect that it helps the slide 84 in the movement towards the right seen in fig.6.

When the slide 84 is moved to the left in fig.6, the working medium will

from the trigger 48 flow into the cavity 82 in fig. 6 and then out of the valve 38. This creates a pressure rise in the cavity or bore 83, which in turn creates a pressure force which acts against the back of the pilot piston 100. Consequently, a force is developed which helps the slide 84 in its movement to the left in fig.6 .

A third advantageous feature of the valves 36,38,40,42 and 44 lies in the way these valves are designed so that twice the flow capacity <at a given opening size.

the result of this is that the stretch along which the valve slide must be moved,

i.e. to go from fully open to fully closed, is a significant factor in the design of a sequence operation valve. In this context, it is desirable to keep this movement as small as possible. As a general construction rule, the distance that the slide moves when switching is twice the opening size with an addition for a certain distance due to the tolerances. Due to the design of the valves 36, 38, 40, 42 and 44, the opening size in the example

approx. 3mm (1/8") and the slide movement is slightly larger than 6.2mm (1/4"). Furthermore, the hydraulic working medium will be the clearest

according to fig. 3A and 3B, enter between the sealing members 94 and 96

and then flow through a hole in the slide 84 with a diameter in the example of 4.7mm (3/16"). The medium flow is then divided and leaves the slide 84 through a pair of double sealing elements 86

and goes into a bore which in the example is approx. 3mm (l/8").

Consequently, the pressure drop in valve 38, which is representative, will

for all valves 36,38,40,42 and 44, be only half of what occurs with known valves with approx. 3mm (l/8") openings.

Reference should now be made to fig. 4 and 5, where it is illustrated

an embodiment of double sealing elements with low friction and no cross flow, of the kind intended for use in valves 36, 38, 40, 42 and 44. The elements are shown in valve 38 at 86 in Figs. 3A, 3B and 6. Then the sealing elements shown in figures 4 and 5 have largely the same mode of operation and are more or less the same structure, the description below will take place with reference to fig.5.

The double sealing element which is shown in Fig. 5 and which is denoted by reference number 86, as indicated in Fig. 3A and 6, is suitably received in a suitably designed bore which is made for this purpose in a slide, e.g. the slide 84 in the valve 38. As shown in Fig. 5, the double sealing element 86 in the design example has four bone-like sealing members, 86a, 86b, 86c, 86d.

These four bodies can be perceived as two pairs, namely an inner pair formed by the bodies 86b and 86c and an outer pair formed by the bodies 86a and 86d. The sealing element 86 can actually be perceived as a sealing element with a sealing element, namely an inner sealing element 110 which consists of the piston area 112 and the bone-like bodies 86b and 86c, and an outer sealing element 114 which consists of the piston area 116 and the bone-like bodies 86a and 86d.

As shown in fig. 5, the double sealing element 86 has a first spring element 118 which exerts a biasing force on the pressure area 112 of the first sealing element 110, and a second spring element 120 for the pressure area 116 of the second sealing element 114.1 In addition, there is arranged in the slide 84 a suitably placed hole 122 which acts as an inlet opening to the sealing element 86 for hydraulic working medium under pressure. The sealing element 86 has the following special characteristics. Firstly, the pressure areas 112 and 116 of the sealing elements 110 and 114 equal in size.

Secondly, the operation of the double sealing element 86 is such that

only one of the individual elements 110 and 114 can seal at a time.

Thirdly, each of the individual sealing elements 110 and

114 individually in sealing contact against parts of the slide 84 that lie opposite each other. Fourthly, the sliding friction of the sealing element 86 is low due to the small dimensions of the pressure areas 112

and 116 to the respective sealing elements 110 and 114.

the manner of the double sealing element 86 will be clear from fig.5, where certain relative positions that the element 86 can take are shown with solid lines for the position denoted by reference number 124, and with dashed lines for the positions denoted by reference numbers 126, 128 and 130. For this purpose, the sealing with the element 86 in the position shown in fig. 5 with reference number 124 will take place with the inner sealing part 110. When the element 86 comes into position 126, a by-flow occurs around the legs 86b and 86c to the inner sealing element 110, but this flow is stopped by the outer sealing element 114. Then, when the element 86 comes into position 128, a by-flow occurs around the legs 86a and 86d to the outer sealing element 114, but the inner sealing element 110 blocks this flow .Finally,

when the element 86 is in position 130 shown in fig. 5, the sealing takes place with the help of the inner element 110. Finally, it should be noted that the parts of the double sealing element which are shown in figures 4 and 5 and which are similar, are provided with the same reference number with an apostrophe in fig.4.

Fig.7 and 8 show a spring with constant force, which is

particularly suitable for use in a sequential operation valve, e.g. valves 36, 38, 40, 42 or 44, of the type intended for use in the control circuit 12 in fig. 2. In fig. 7 and 8 this spring is designated generally with the reference number 88, and this number has also been used to designate the constant force spring in the valve 38 in fig. 3A, 3B and 6. As mentioned above, it has proven appropriate to use such a spring in sequential operation valves for underwater use. A main reason for this is that such a spring creates a lower deadband than could be achieved with a normal spring. This means that a normal spring has a spring coefficient, that is, when the spring is pressed further together that gives a higher force. When a spring with non-constant force used in a sequence-operated valve, a higher pilot pressure is required to complete the stroke than to start it, creating dead-

band. On the other hand, a constant-force spring has zero spring constant over a sufficiently large area of influence, so that no deadband occurs in such a vein, p. g. a. the f j ør effect.

In connection with the use of a constant force spring in a sequential operation valve, it should be noted that the biasing force in such a valve must be relatively high, because it creates

maintain a small dead band, must be high compared to the frictional forces found in the valve. For example, such a valve usually requires a spring that is able to create a biasing force of about 816 kp over a movement range of approx. 8mm. Compression springs with constant force are not new in the area. However, known forms of constant force springs have been used for purposes that require relatively low forces, and it is not known that constant force springs have been used in equipment that requires forces in the surrounding area lOOOkp. (2000 pounds). In addition, known constant-force springs have had various disadvantages. Firstly, springs with too high forces have had too great stresses in the spring material. In addition, they have had the disadvantage that the pin at the end has had too high sliding friction. However, these disadvantages have been removed by the spring 88 which is shown in fig.7 and 8.

In the embodiment shown in Fig. 7 and 8, the spring 88 comprises four spring elements 132 which are placed evenly distributed around a common axis. In addition, the spring 88 comprises a pair of end covers 134

and 136, of which at least one, e.g. end cover 136, is threaded so that it can be screwed onto the member 178. Finally, the construction comprises a pair of locking elements 140, only one of which is shown in fig.8.

Fig.9 shows an intermediate valve of the type that is

intended for use together with the sequential operation valves, e.g. valves 36, 38, 40, 42, and 44 in fig. 2. The valve in fig. 9 is given the same reference number 58 as the intermediate valve 58 in fig. 2. As shown in fig.9 it comprises a housing or a main part 142 with a generally cylinder-shaped bore 144. In the bore 144, a slide 146 is suitably placed. A pair of sealing members 148 and 150 are placed in the slide 146, so that the axis of the sealing members 148 and 150 corresponds to a pair of generally circular holes 152 and 154 formed in the side walls of the valve housing 142, so that one 152 forms an inlet and the other 154 forms an outlet from the bore. With the components in the intermediate valve 58 shown in fig.9, the inlet opening 152

communicate with the outlet opening 154 through the bores for this purpose in the sealing elements 148 and 150. The elements 148 and 150 create a seal that prevents working medium under pressure from entering the openings surrounding the slide 146. The slide 146 is biased to the left in fig.9 by a spring 158, so that the valve 58 is usually in the open position. When the opening 160 is exposed to pressure, however, a force will develop over the piston 162 which is sufficient to press against the spring 158 and the friction from the sealing elements 148 and 150, so that the slide 146 is moved to the right in fig. 9. This movement causes the outlet opening 154 to be closed by the lower sealing element 150 and allows the incoming working medium into the valve 58 and into a cavity 156 and from there to venting, e.g. against sea pressure. When pressure is supplied through the opening 164 in the valve housing, the slide 146 will be displaced to the left in fig.8, because the piston 162 has the same area as an opposing piston 166, consequently the forces that are formed over the pistons 162

and 162 be equal, because the pressure is the same on these, which allows the spring 158 to displace the slide 146 to the left in fig.9. When an inlet opening 168 is put under pressure, the slide 146 will again move to the right in fig.9, because an associated piston 170 has double the area compared to the pistons 162 and 166.

According to the invention, a new underwater control system has been created, which can be used to control the production of a "Christmas tree" from a control center at the surface. This control system can be operated as a sequence-controlled hydraulic system, as it includes control circuits that can be triggered sequentially by the occurrence of certain predetermined pressure levels in a pilot line. According to the invention, a control system has been created that reduces both the number of control lines that must be routed between the "Christmas tree" and the control center, i.e. removes the need for a line to be used to create a reference pressure, and the number of control valves that required for the operation of the system. In addition, this control system provides a flexibility that enables a number of different operating programs. According to the invention, a control system has also been created with an improved valve control which has a smaller dead band and which allows the looping of pendulum valves inserted between the valve control and the valves on the "Christmas tree" .The control system according to the invention includes a new and improved constant force spring which can create . preload for the valve element in the valve control, so that this has the possibility of operation under the action of both a mechanical spring element and hydraulic pressure, and where the hydraulic pressure works to displace the internal components in the valve control so that these provide either an open or a closed operating position. The invention also includes

a control system with new and improved sealing elements in the valve control, which prevents leakage in it. Finally, the invention includes an intermediate valve with several pistons, placed in the connecting lines between the valve control and the valves on the "Christmas tree".

The shown examples of embodiments of the various parts of the invention can be modified in different ways within the scope of the patent claims.

Claims (11)

1. System for controlling the outflow from an underwater source, with valves located at the outlet of the source, a control center located at the surface, for control of through-flow, <611> of the valves and lines for working medium between the control center and the valves, characterized by that it includes wait Uncontrollers (12) for sequence operation, connected both to the valves (14) and to the control center (16), since these valve controls can be brought selectively into different positions that define different operating states, and where there are constant-force springs that keep the valve controls biased towards a specific position , as the valve controls, when they occupy one of the different positions, can be moved into another position, which gives an influence on a valve, by transferring an influence from the control center, and a pilot line (20) which connects the control center with the valve controls, as this pilot line transfers the influence from the control center to the valve controls, so that they take another of the possible positions. 2. System in accordance with claim 1, characterized in that the valves (14) have at least one valve with a trigger (46,48, 50,52,54,60) and that the valve control comprises at least one sequence operation valve (36,38, 40,42,44) with connection for working medium to the trigger. 3. System in accordance with claim 2, characterized in that the sequence operation valve (36,38,40,42,44) can take different positions, which form different operating states for the valve, since the valve has an independent, constant force element (88) which keeps the valve biased towards one of the different positions, and that the valve, when it is in this position, can be moved under the influence of the control center (16) so that another position It takes Vror to put the trigger on the control valve (46,48,50,52,54,60) into operation. 4. System in accordance with claim 3, characterized in that the constant force element (88) comprises a spring with constant force. 5. System in accordance with claim 2, characterized in that the sequence operation valve (36,38,40,42,44) comprises a double sealing element (86) built into the valve to prevent leakage of working medium when the valve's control element moves from one to the other of the possible positions. 6. System in accordance with claim 2, characterized in that the valve control (12) includes at least one intermediate valve (58, 60) inserted between the sequential operation valve and the other valves (36,38, 40,4ii,44) and the trigger or triggers ' (46 , 48 , 50 , 52 , 54 , 60) on the valve or valves to be controlled, as the intermediate valve or intermediate valves are designed to increase the number of changes the sequential operation valve or valves can make between different positions, and thus the number times the trigger ei;-! the triggers are switched by the valve or valves. / . Sequential operation valve for use in a system in accordance with one of the requirements 1-6, with a housing with a bore, an inlet in this housing, which is connected to a working medium source, an outlet from the housing which is also the outlet from the valve, a slide mounted in the bore moves between a first position which constitutes a first operating condition for the valve and a second position which constitutes a second operational condition for the valve, k^ to be characterized in that it comprises a 'constant force element (88) placed in the housing to exert a bias against the slide (84), and a pilot inlet (98) which can be connected to a pilot pressure source, so that when the pilot pressure reaches a predetermined level and the slide (84) is in the first position, it is caused to move into the second position, so that pressurized medium is released through the outlet opening. 8. Valve in accordance with claim 7, characterized in that the constant force element is a spring. 9. Valve in accordance with claim 7 or 8, characterized in that it comprises a double sealing element (86) connected to the slide (84), the sealing element having the task of preventing leakage in the valve when the slide moves between the two positions. 10. System in accordance with claim 1, characterized in that a valve in accordance with claim 7 is used for controlling a "Christmas tree" with valves for controlling the outflow from an underwater. o <l> j <e> - <og> / electric gas source. 11. Valve for sequential operation, in accordance with claim 7, characterized in that the slide (84) is provided with a sealing element (86) which comprises: a) An internal sealing element comprising a first sealing member which extends substantially symmetrically about an axis perpendicular to the slide and has a substantially closed end and a free end, in which a first spring member (118) presses against the closed end of the first sealing member (86b, 86c) so that it is pressed sealingly against an opposing surface with a free end, and b) an outer sealing element which forms a unit with the inner sealing element, so that together they create a double seal, in that the outer sealing element comprises a second sealing member (86a, 86d) which extends approximately symmetrically in the same direction and about the same axis as the first sealing member, concentric with this, and similarly with a largely closed end and a free end, in which a second spring element (120) presses the free end of the second sealing member against the opposite surface, to form a seal against this .