WO1994023231A1

WO1994023231A1 - A servo operated stop valve installation

Info

Publication number: WO1994023231A1
Application number: PCT/DK1994/000144
Authority: WO
Inventors: Hans Nørgaard PEDERSEN
Original assignee: Abb District Heating
Priority date: 1993-04-07
Filing date: 1994-04-07
Publication date: 1994-10-13
Also published as: DK41393A; DK171282B1; DK41393D0; SE9503439D0; PL310943A1; GB2292420B; FI954760A; DE4491874T1; FI954760A0; AU6424994A; SE503992C2; GB9519929D0; CN1120368A; SE9503439L; GB2292420A

Abstract

A subterranean stop valve in a district heating system is laid out for servocontrolled operation from a nearby walkway cabinet, by hydraulic actuation of a double acting free piston block (8), which is displaceable with high power just as much as required for a full change-over of the valve (2). Just prior to the full change-over being reached it is automatically arranged that at the hydraulic return end of the piston the return flow (28) is shifted to now be forced (at 42) into a remote indicator (48), whereby a slide body (54) in the latter is changed over, affected by a high force immediately at the end of the full valve change-over. Hereby a robust and long-time durable change-over and indicator system is achievable.

Description

A SERVO OPERATED STOP VALVE INSTALLATION

The present invention relates to a servo operated stop valve installation, particularly for use in sub¬ terranean pipelines such as district heating systems, comprising a valve with an associated change-over motor and a power- or operating station located in an easily accessible place at distance from the stop valve.

In district heating systems there is usually moun¬ ted a number of stop valves, often placed beneath street level where they are accessible for manual actuation, as they are placed with a valve spindle projecting till just below an upper cover of a surrounding well ring. This installation demands a great del of work, and will cause disturbance of the traffic when the stop valve has to be actuated, as it is necessary to arrange some road blocking.

Therefore, for some valves the first mentioned installation is preferred, where the valve/motor unit can be totally buried and only through a current or hydraulic conduit be connected to the said operating station, which can be laid out in a nearby walkway cabi¬ net. The valve can then be actuated without any obstruc¬ tion of the traffic. However, an almost inverse problem can occur, namely that the valve so to speak never is actuated, whereby the swivelling part can get very stuck, and it is therefore a further advantage of the motor-actuated valves that it is possible to work with higher operating force than by manual actuation.

With the mentioned, totally buried valve units it can be a problem that it is impossible to observe whether a change-over order has been fully executed, which in practice is an important condition, as the valves are not normally designed to being left in an only almost completely closed or almost completely open position. It would therefore be desirable to establish some kind of sensor monitoring to ensure that the acti- vation actuation is actually terminated with the full change-over of the valve, and there has been many specu¬ lations and proposals concerning this. It is obvious that for operating- and control experts there will be a tremendous number of theoretical possible solutions, but they have all had to be rejected in a row due to the special mounting circumstances and to the demand for long-time full operating ability, for example 30-40 years. It is found irrelevant in the present connection to elaborate the possibilities and troubles of the above proposals closer, but it shall be mentioned that it is customary, however, to methodically make some kind of safety operation of the valves approximately once a year to prevent too severe rootings.

By the invention there has been provided a special actuating- and signalling system, which has been able to fulfill the extreme security demands posed for the func¬ tional performance of the system.

By the invention it is chosen to work with a hy¬ draulic actuation, as it is hereby relatively inexpen¬ sive and secure to use rather high operating forces, for instance a pressure of some hundreds of bars, which surely will loosen rooted valves. The associated pump equipment can be placed in the walkway cabinet, and down by the valve a hydraulic cylinder with a piston body can be placed, which by displacement respectively the one and the other way causes the spindel of the valve to rotate by co-operation between a toothed bar on the piston body and a toothed ring on the spindel.

In connection with this cylinder a special signal system is provided, from which, at the end of each change-over movement of the valve, is given a signal pressure, this being transferred to a hydraulic indica¬ tor unit in the cabinet.

In the following this is explained in more detail with reference to the drawing, in which:

Fig. 1 is a schematic and partly sectional view of a system according to the invention, and

Fig. 2 is a corresponding view of a modified sys¬ tem.

The shown dotted transversal line a shows the ground level, below which is mounted a stop valve with valve spindel 2 designed with a toothed ring 4. This co-operates with a toothing 6 on a slide body 8, which at the ends constitute piston parts 10 co-operating with respective cylinder parts 12 and 14, which are strongly restrained to a common non-illustrated base. The two cylinder parts 12 and 14 have a cylinder head 16, in which is made a central bore 18 and a through channel 20 connected therewith. Furthermore these cylinder heads have a through channel 22 outside the central bore 18.

On the ends of the piston parts 10 is formed a protruding piston pin 24 fitting the respective cen¬ tral bores 18.

The slide body 8 is illustrated in a left hand-side position with possibility of performing a displacement towards the right corresponding to what is necessary for turning the spindel 2 through 90°, i.e. for actuating the stop valve between closed and open position.

The two channels 20 and 22 at each end of the sys¬ tem is connected to a common hydraulic conduit, respec¬ tively 26 and 28, being connected to a hydraulic change¬ over valve unit 30 in the walkway cabinet. Through this unit these conduits can be connected in a switchable way to respectively the pressure side of a hydraulic pump 32 with suction reservoir 34 and the same or preferably a separate receiving reservoir 36. It will be noted that in the situation shown the pump 32 can be started for pushing the slide body 8 towards the right for changing- over the stop valve, while succeedingly it is possible. after changing-over the valve unit 30, to provoke a re¬ turn motion of the valve.

At both ends of the cylinder system, between the connections to the channels 20 and 22, there is placed a check valve 38 allowing inflow of hydraulic fluid from the conduits 26 and 28 to the channels 22, but preclud¬ ing an outflow the opposite way, and the channels 22 are on the stopside of these check valves connected through respective conduits 40 and 42 with a separate portion of the change-over unit 30, through which these conduits are alternatingly connectable to, respectively, the one and the other of the conduits 44 and 46, leading to an indicator unit 48 placed in the walkway cabinet, respectively to a receiving reservoir 50 connected therewith.

The indicator unit 48 has a cylinder part 52, in which is mounted a slide 54, which can be pushed from side to side by admission of pressure fluid through the respective conduits 44 and 46. At its middle area the slide 54 is shaped with a constriction 56, which can co-operate with the one or the other of two spring-load¬ ed balls 58 being connected with respective projecting arm parts 60, having at their outer end a projecting part 62, which will clearly indicate visually whether the slide 54 is in the one or the other outer position, according to the projecting part 60,62 being more or less projecting from the unit 48.

Assuming the valve is in open position and is want¬ ed to be closed, the pump 32 only needs to be started, whereafter pressure fluid through the conduit 26 is sent through the channels 20 and 22 to the entire cylinder chamber in the left cylinder part 12. In the pilot valve 30 there will be closed for outflow of pressure fluid through the conduit 40. Thus a very large opening mo¬ mentum can be exerted on the valve spindel 2, so that even the most rooted valve can be expected to be switch¬ able. Thus it will only exceptionally be necessary to dig up a valve for repair or replacement.

During the change-over of the slide body 8 the hydraulic fluid in the right cylinder chamber 14 can escape through the central channel 20 and the conduit 28 back to the tank 36. This can happen without significant resistance, whereas an outflow through the channel 22 to the connection conduit 42,44 to the indicator 48 will be resisted by the indicator slide 54 being exposed to a lock effect by the hold of the ball 58 in the groove 56.

However, at the end of the change-over movement the central bore 18 will be blocked by the piston pin part 24, whereby it will only be the fluid in the chamber 18 which will eventually escape to the tank 36, whereas the fluid in the surrounding chamber is forced to the con¬ duit 42,44 and thus provokes a change-over of the indi¬ cator slide 54. The length of the piston pin 24 is so adapted that at the final travel of the slide 8 there will be forced out just so much fluid that a full and safe change-over of the indicator slide is performed, as the fluid by the other end of the latter escapes through the conduit 46 to the tank 50.

In this way a clearly visible indication of the fulfilled valve change-over is achieved by the arm parts 60 and 62 changing positions between the more and the less projecting position, and this indication will not appear until during the very last few degrees of turning of the valve spindel 2.

With reference to the diagram blocks shown in the change-over valve 30 it will not demand any further explanation here that a following re-opening of the valve will take place in exactly the same way, only with the valve 30 being switched over. It is rather essenti¬ al, that the sign of the indicator for re-achieved full opening only appears at the actual establishing of the full opening; an extensive and in a sense sufficient opening could very well be detected already by the re- appearence of the hot water to the stretch behind the valve, but because of the special valve construction it will normally be destructive for the valve, if it is not re-positioned to full opening under all circumstances.

It will be natural that after every use of the system or at least after every opening/closing operation the hydraulic fluid being caught in the tanks 36 and 50 is collected and deposited, and that this 'old' fluid is replaced with a new fluid being lead to the tank 34.

The invention will not be limited to the illustra¬ ted embodiment, and especially not as to the way in which the very indication of the changeover is achieved. Also, the arrangement of the working cylinder can be modified for achieving that the pressure which changes over the indicator will only appear in the very last phase of the valve change-over.

In fig. 2 such a modification is illustrated, by which is achieved even a simplification of the hydraulic system, as the double valve 30 is replaced with a single change-over valve 30'. In the main cylinder 12', 14' the central bores 18 are left out, and in return the piston 8' is made with yieldable, inwards squeezable, project¬ ing central pins 24', the associated bores 64 of which are mutually connected through a channel 66, which, when filled with hydraulic liquid, even enables the project¬ ing pins 24' to be depressed one at a time. Such a depressing will take place when the piston 8' reaches one of its outer positions, as the pin 24' then will close for the outflow of hydraulic fluid through the bore 20' directly to the return tank 34, 36', whereafter this closing is maintained during the remaining final movement of the piston 8', by which the remaining confi- ned fluid portion is pushed forward through the conduit 42' to the indicator 48', here through a valve 68, which only opens at a certain over-pressure at the inlet side, for instance at approximately 30 bars, and which is con¬ nected to a check valve 70 in the conduit 46'.

The indicator unit 48' is also here designed as a slide housing with an internal slide, but the means for indicating the slide position is, in a manner not de¬ scribed in more detail, replaced with outer, magnetical¬ ly operating indicator means, which can signal whether the slide 54' stands in the one or the other of its outer positions.

Claims

C L A I M S :

1. Servo operated stop valve installation, particu¬ larly for use in subterranean pipelines such as in dis¬ trict heating systems, comprising a valve having a hy¬ draulic change-over motor and an associated operation station located in an easily accessible place at distan¬ ce from the valve, which installation includes indicator means for remote indication of the stop valve assuming a fully open or a fully closed position, respectively characterized in that the change-over motor is a double acting cylinder unit with a piston rod which is operati- vely connected with the acutation unit of the valve for turning of this to full opening or closing of the valve by hydraulically forcing home the piston of the cylinder unit in the one or the other direction, respectively, and in that the indicator means are arranged for change- -over dependent on the piston during the last part of its change-over movement provoking a blocking of the hydraulic return flow and a succeeding forced outflow of the remaining trapped hydraulic fluid for change-over of the indicator means.

2. Installation according to claim 1, characterized in that the piston being constructed as a free piston block, the opposite ends of which are received into res¬ pective cylinder head parts, and in that the hydraulic driving- and return connection to these parts are lead through local cylinder bores in the inner end surfaces of the cylinder head parts, the piston block at both ends having a projecting pin part, which, by movement against the associated cylinder bore closes this in a position of the piston, from which the piston is finally moveable through a volumen containing just as much hy¬ draulic fluid as required for a correct change-over of the indicator means.

3. Installation according to claim 1, characterized in that the indicator means comprise a hydraulically ac¬ tuated slide equipped with mechanical sensors for indi¬ cating the slide position.