TECHNICAL FIELD

The present invention relates to one or several fluid flow control arrangements for regulating the flow of a fluid in a district heating conduit system and a method for regulating the flow of a fluid in a district heating conduit system using such fluid flow control arrangement. BACKGROUND OF THE INVENTION

Some energy distributions systems comprise conduits in which heated and/or cooled fluid are being transported. Such energy distribution systems usually have a power plant in one end of the pipe system and an end user, e.g. a plurality of houses which are to be warmed, in the other end of the pipe system. The heated or cooled fluid is circulated there between. Such an energy distribution system is often referred to as a district heating conduit system. To control the fluid flow in a district heating conduit system, a fluid flow control arrangement can be used. An example of a fluid flow control arrangement is known from the patent publication number SE 531 654 C2, Industriarmatur-Ari AB. The fluid flow control arrangement presented in SE 531 654 C2 can be adapted for remote control, however, as pipe systems of a district heating conduit system generally are very long, it has been found that remote control of fluid flow control arrangements are more difficult than first expected. Pressure peaks when opening or closing valves can damage equipment and impart high maintenance costs. For example, when a fluid valve is closed, an underpressure is created downstream of the valve while an overpressure is created upstream of the valve. Underpressure and overpressure can in cases differ as much as 10 bars. This problem becomes very prominent further upstream and further downstream of the valve as the pressure peaks pulses through the fluid in the conduit system. An improved fluid flow control arrangement and a method for regulating the flow of a fluid in a district heating conduit system are thus required. To reduce the risk for damaging equipment during such pressure peaks. SUMMARY OF THE INVENTION

It is an objective with the present invention to provide an improved fluid flow control arrangement for regulating the flow of a fluid in a district heating conduit system. The object is presently met by a fluid flow control arrangement comprising

a first hydraulic operated valve connected to a first hydraulic operating device and a second hydraulic operated valve connected to a second hydraulic operating device. The first and the second hydraulic operating devices are connected to at least one hydraulic pilot valve configured to enable a hydraulic flow in the first and second hydraulic operating devices thereby enabling the first and the second hydraulic operated valves to be varied between an open position and a closed position.

The fluid flow control arrangement, and preferably the at least one hydraulic pilot valve, is connected with a signal sending and receiving unit. The signal sending and receiving unit is adapted to receive a signal so as operate the first and second hydraulic operated valves between the open position and the closed position. The signal sending and receiving unit is further adapted to send a signal indicative of the position of the first and second hydraulic operated valves. The fluid flow control arrangement is further adapted to halt, open or close the first hydraulic operated valve as a function of the position of the second hydraulic operated valve

The present invention enables a closing or opening procedure/operation and thus reduces the risk of pressure peaks within the district heating conduit system. Such pressure peaks can severely damage equipment. According to an aspect of the present invention, the fluid flow control arrangement is adapted to operate the first and second hydraulic operated valves simultaneously. This can be done by using two hydraulic pilot valves or by using a single hydraulic pilot valve having a valve position permitting hydraulic operation of both said first and second hydraulic operated valves.

According to an aspect of the present invention, the fluid flow control arrangement is adapted to operate the first and second hydraulic operated valves separately one at a time. This can be done by using two hydraulic pilot valves which are operated one at a time or by using a single hydraulic pilot valve which switches between operating the first and second hydraulic operated valves. Having a single hydraulic pilot valve can be advantageous in cases where the space is confined however using at least two hydraulic pilot valves enables a simpler construction of each hydraulic pilot valve and thus a more robust construction. Optionally or additionally, one or at least two hydraulic pumps can be used with the fluid flow control arrangement. For example a single hydraulic pump can be used in

combination with two hydraulic pilot valves thus permitting hydraulic operation of both said first and second hydraulic operated valves simultaneously or separately. According to an aspect of the present invention, the first and second hydraulic operated valves are adapted to be operated separately one at a time. This can be done by using two hydraulic pumps which are operated one at a time or as preferred, by using a single hydraulic pump which switches between operating the first and second hydraulic operated valves. Having a single hydraulic pump reduces costs and simplifies the construction of the fluid flow control arrangement according to the present invention.

According to an aspect of the present invention, the signal indicative of the position of at least one of the first and second hydraulic operated valves is derived from a sensor. The sensor is adapted to sense the position of the first or the second hydraulic operated valves and can transmit directly to a central radio office or to a local processing unit or just relay the signal to a second fluid flow control arrangement.

According to an aspect of the present invention, the sensor is a potentiometer, pressure-, temperature-, flow sensor or combinations thereof.

According to an aspect of the present invention, a processing unit, such as a PLC or a computer, CPU, is arranged to the signal sending and receiving unit.

According to an aspect of the present invention, the signal sending and receiving unit is a wireless signal sending and receiving unit.

According to an aspect of the present invention, a first, a second and a third fluid flow control arrangements are arranged in working cooperation. The first fluid flow control arrangement is adapted to communicate with the second fluid flow control arrangement and a central radio office, and the second fluid flow control arrangement is adapted to communicate with the third fluid flow control arrangement and the first fluid flow control arrangement, preferably only. The present system requires only one fluid flow control arrangement which is capable of long range communication with a remote central radio office, e.g. across a whole nation, while the other fluid flow control arrangements can be adapted to shorter range communication, e.g. a few kilometres.

According to a second aspect of the present invention, the present invention also relates to a method for operating the fluid flow control arrangement. The method comprises the steps of;

initiating an opening or closing procedure of at least one of the hydraulic operates valves upon a received signal to said signal sending and receiving unit;

-detecting the position of at least said first hydraulic operated valve;

-stopping, opening or closing said second hydraulic operated valve as a function of the detected position of said first hydraulic operated valve.

The method significantly reduces the risk of having pressure peaks in the pipe system.

According to the second aspect of the present invention the initiated procedure is a closing procedure and,

wherein the position of the first hydraulic operated valve is determined and

the position of the second hydraulic operated valve is determined. The first hydraulic operated valve is moved to a synchronized position with the second the hydraulic operated valve, whereafter the first and second hydraulic operated valves are closed substantially simultaneously.

According to the second aspect of the present invention the fluid flow control arrangement is adapted to communicate with a second fluid flow control arrangement having at least a first hydraulic operated valve, before or during the opening or closing procedure, to synchronize the first or the second hydraulic operated valves of the first fluid flow control arrangement with at least the first hydraulic operated valve of the second fluid flow control arrangement.

The first and second hydraulic operated valves can be moved stepwise towards an open or closed position in an alternating manner, and as a function of the determined positions of said first and second hydraulic operated valves.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be described in greater detail with reference to the

accompanying figures in which;

figure 1 shows a fluid flow control arrangement according to the present invention;

figure 2 shows a district heating conduit system having a plurality of fluid flow control arrangements according to the present invention;

figure 3a-3b show a diagram of the degree of opening Vs time for a first and a second hydraulic operated valve.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A fluid flow control arrangement 100 will first be described with reference to figure 1 whereafter a district heating conduit system 30 using a plurality of fluid flow control arrangements 100 will be described with reference to figure 2.

Figure 1 shows a fluid flow control arrangement 100 for regulating the flow of a fluid in a district heating conduit system, as shown in figure 2. The fluid flow control arrangement 100 comprises a first and a second hydraulic operated valve 2a, 2b connected to a first and a second hydraulic operating device 1 a, 1 b. The fluid flow control arrangement 100 can be used to control the opening and the closing of the hydraulic operated valves 2a, 2b and thereby controlling the fluid flow. The hydraulic operating devices 1 a, 1 b are arranged to a hydraulic pilot valve 8, which in the shown embodiment is a hydraulic pilot valve, which in turn is arranged in working cooperation with a wireless signal sending and receiving unit 10 adapted to receive a signal so as operate said first and second hydraulic operated valves between said open position and said closed position from a remote position. The fluid flow control arrangement 100 is adapted to enable on opening or closing operation of at least one of the hydraulic operated valves 2a, 2b as a function of the position of at least one of the hydraulic operated valves 2a, 2b. Optionally to enable a synchronized opening and/or closing operation of the first and the second hydraulic operated valves 2a, 2b to reduce the effects of, fluid pressure fluctuations within a pipe system. An embodiment of a fluid flow control arrangement 100 will be described hereafter. A hydraulic operating device 1 a is mounted to a hydraulic operated valve 2a to permit operation thereof. The hydraulic operating device 1 is in fluid communication with a hydraulic pilot valve 8 via hydraulic hoses or pipes 3a. The hydraulic pilot valve 8 is

5 arranged in a cubicle 4 to protect the hydraulic pilot valve 8 from the ambient

environment. Electricity and signal cables can be connected to the cubicle 4 to provide power and communication options. The hydraulic pilot valve 8 is arranged with a hydraulic pump 6 which is in fluid communication with a fluid source, such as an oil container. The hydraulic pilot valve 8 is thus coupled to a pressurized fluid source for regulating the

10 hydraulic operating device 1 a. An operating system 12 is used for surveillance and for operating the hydraulic components. The operating system is advantageously arranged in a heated cabinet 9. The heated cabinet 9 is arranged in the cubicle 4.

The operating system 12 can be operated via the wireless signal sending and receiving 15 unit 10. The operating system 12 and thereby the hydraulic pump 6 and the hydraulic pilot valve 8 can be operated using a protocol such as Profibus, CANbus or l2C-bus. To communicate with a central radio office cables such as TP-cable, fibre optics or wireless communication can be used.

20 The hydraulic pump 6 and/or the hydraulic pilot valve 8 can further be controlled using a local operating panel (not shown). The hydraulic operated valves can be manually controlled using coupling arrangement 1 1 for connecting a portable pump.

Figure 1 further illustrate that suitable components to be positioned below the ground level 25 17 is the hydraulic operating device 1 a and the hydraulic operated valve 2a, as these are the components best suited for the harsh sub ground level environment. Electrical components are thus removed from that environment. The hydraulic hoses 3a can be protected using flexible plastic pipes. As the hydraulic hoses 3a connects the hydraulic operating device 1 a and the hydraulic pilot valve 8, no electricity is required to be drawn to 30 a sub ground level, i.e. subterranean. By controlling the hydraulic pilot valve 8 with

electronic components, opening and closing functions can be achieved. By controlling the hydraulic pump 6 with electronic components on/off or changes in fluid flow functions can be achieved. The hydraulic pump 6 and the hydraulic pilot valve 8 can thus be remotely controlled from a central radio office.

35 The cubicle 4 is provided with means for remote control 13. The means for remote control can comprise copper wires, such as a two wire system 16, either through dedicated communication lines or through public telephone line, or power line communication, i.e. communication through one or more power grids, fiber optics or wireless communication. Wireless communication is preferred. The wireless communication can be operated through GSM/GPRS-net, UMTS, CDMA2000, or similar technique with long transmitting and receiving range.

The language used for communication can be Profibus, or any other protocol or net work based protocol such as Ethernet or Internet protocols. A protocol module 15 can be arranged in the cabinet 9 which is communicating with a programmable logic computer 14 (hereafter referred to as a PLC). The protocol module translated the signals to the PLC when receiving the signals and from the PLC when transferring the signals to a second protocol module at a central radio office. The protocol can be either analog or digital.

In the embodiment shown in figure 1 the hydraulic pilot valve 8 is coupled to a plurality of hydraulic operating devices 1 a, 1 b mounted to hydraulic operated valves 2a, 2b to permit operation thereof. As is indicated with the arrows A _Lef t and A _Ri g _ht (hereafter referred to as A _L and A _R ), the flow direction in the pipes are different, as will be described in greater detail below.

Figure 2 shows a district heating conduit system 30 comprising a heating source 31 , such a district heating power plant 32 (hereafter referred to as the plant 32), a pipe system 33 for transferring fluid between a facility 34 and the heating source 31. The facility 34 can be a single house or a plurality of facilities which are connected to the district heating conduit system 30. The general principle is that a fluid, such as water, is transferred from the plant 32 via the pipe system 33 to the facility 34 in a direction A _L at which it either releases heat or collects heat, to thereafter be transferred back to the plant 32 in a direction A _R . The pipe system 33 can be several kilometers long. Due to the long distances in such pipe systems, it is important to maintain constant flows or continuous flow changes to reduce the risk of pressure peaks from the fluid in the pipe system 33.

Fluid flow control arrangements 100, as described herein, are arranged at different positions along the pipe system 33 to regulate the fluid flow in the pipe system 33. Each of the fluid flow control arrangements 100 are adapted to communicate, preferably wireless, with a central radio office 40 and/or between other fluid flow control arrangements 100. As is noticed the central radio office 40 is separated form the fluid flow control arrangements 100 as one important aspect of the invention is to enable remote control operation of fluid flow control arrangements 100 in an accurate manner.

In an embodiment of the present invention, a district heating conduit system 30 comprises at least three fluid flow control arrangements 100, wherein one fluid flow control arrangement 100 is adapted to communicate with the central radio office 40 and with a second fluid flow control arrangement 100, and at least two fluid flow control

arrangements 100 are adapted to communicate only between themselves.

At least one fluid flow control arrangements 100, preferably all, further comprises at least one hydraulic operated valve positioning sensor 20, which enables direct or indirect detection of the position of the hydraulic operated valve. The detected position can be open, closed or a position there between such as 10 % open (90 % closed), 20 % open (80 % closed), 30 % open (70 % closed), 100 % open (0% closed), etc. The percentage is determined as 0 % open being fully closed and 100 % open being fully open, permitting maximum flow through the hydraulic operated valve. The percentage between 0 % open and 100 % open being determined as a function of the maximum distance the hydraulic operated valve is displaced, or rotated, compared with the actual displacement, or rotation, of the hydraulic operated valve.

The hydraulic operated valve positioning sensor 20 can be in working cooperation with the hydraulic pilot valve 8 and measure the flow in the hydraulic pilot valve 8, thus

determining indirectly the position of the hydraulic operated valve 2a, 2b. Preferably to get an accurate reading the hydraulic operated valve positioning sensor 20 is arranged directly to the hydraulic pilot valve 8, although other positions along the hydraulic hoses 3 are possible. In an embodiment, the hydraulic operated valve positioning sensor 20, such as a potentiometer is arranged on the hydraulic operated valve 2a, 2b or on the hydraulic operating device 1 a, 1 b. Optionally or additionally, the hydraulic operated valve positioning sensor 20 can be a pressure or temperature sensor arranged on either side of the hydraulic operated valve giving indirect measurements of the hydraulic operated valves position. The hydraulic operated valve positioning sensor 20 is adapted to either communicate directly with the central radio office 40 and/or with the wireless signal sending and receiving unit 10. During operation, a hydraulic operated valve positioning sensor 20, associated with a specific hydraulic operated valve 2a, detects the position of the hydraulic operated valve 2a and synchronizes the detected position with the second hydraulic operated valve 2b during the opening or closing procedure.

In a preferred embodiment, the synchronization is performed before closing the hydraulic operated valves 2a, 2b and advantageously when at least one of the first or the second hydraulic operated valves 2a, 2b are between 1-20 % open, preferably 1-10 % open.

A closing sequence will hereafter be described in greater detail. An operator, or an automatic control function at central radio office 40, has detected that a fluid flow in the pipe system 33 needs to be redirected or terminated. Upon a command, a signal is transmitted via a satellite 41 , and/or ground based antenna(s), to a fluid flow control arrangement 100, in this case the fluid flow control arrangement 101. The fluid flow control arrangement 101 initiate a closing command to close the first and the second hydraulic operated valves 2a, 2b, by requesting the position of the first and the second hydraulic operated valves 2a, 2b. The hydraulic operated valve which is furthest from being closed, i.e. which has highest determined % open, is initiated first directing the hydraulic pilot valve 8 to that hydraulic operated valve and by starting the hydraulic pump 6. When the first and second hydraulic operated valves are determined to have substantially the same amount % open, the hydraulic pilot valve 8 can be instructed to alternate between the first and the second hydraulic operated valves 2a, 2b to close the first and the second hydraulic operated valves 2a, 2b a few % at a time, generally about 1 -4 % at a time, preferably 1 -2 % at a time.

As the hydraulic operated valve positioning sensors 20 indicate that the hydraulic operated valves 2a, 2b are 1-5 % open, preferably 1 -3 % open, the first and the second hydraulic operated valves 2a, 2b are closed simultaneously so that the first and the second hydraulic valves 2a, 2b reach 0 % open (100 % closed) substantially

simultaneously. In this way, the first and the second hydraulic operated valves are synchronized twice, one in the beginning of the closing procedure and a second time just before the end of the closing procedure. This reduced significantly the risk of having pressure peaks within the pipe system 33. In an embodiment of the present invention, at least two fluid flow control arrangements 100, herein referred to as the first fluid flow control arrangement 101 and the second fluid flow control arrangement 102, are synchronized during an opening or closing procedure. In this case the positions of the first and second hydraulic operated valves 2a, 2b of first fluid flow control arrangement 101 are synchronized with the first and second hydraulic operated valves 2c, 2d of the second fluid flow control arrangement 102, just before closing the first and second hydraulic operated valves 2a, 2b, 2c, 2d of first and the second fluid flow control arrangements 101 , 102.

Figure 3a shows a diagram of the opening/closing degree, i.e. the position, where 100 % is equal to 100 % open, of the first and the second hydraulic operated valves 2a, 2b as a function of time. Time is in this case illustrated in time units. One such time unit can be 20 seconds for example. According to the present invention, the opening and closing operation of the first hydraulic operated valve 2a is based on the position, e.g. degree open, of the second hydraulic operated valve 2b. As is seen in figure 3, the first hydraulic operated valve 2a is opened, i.e. moved towards 100 % degree open for one time unit. When the position of the first hydraulic operated valve 2a is detected to be at 10 % open, the opening procedure is stopped and the opening procedure of the second hydraulic operated valve 2b is initiated. When the position of the second hydraulic operated valve 2b has reached 10 % open, the second hydraulic operated valve 2b is stopped and the opening of the first hydraulic operated valve 2a is started again. In this way is a stepwise opening of the first and the second hydraulic operated valves 2a, 2b, is performed in an alternating manner. It has been found that this is a very safe and easy way to prevent pressure fluctuations in the conduit system.

Figure 3b shows the graph of the first hydraulic operated valve 2a during complications of the closing procedure of first hydraulic operated valve 2a. For example, the first hydraulic operated valve 2a is prevented from closing due a temporarily malfunction, the second hydraulic operated valve 2b will not start until the first hydraulic operated valve 2a has reached its intended position. As soon as the first hydraulic operated valve 2a has reached its intended position, in this case 30 % open, the second hydraulic operated valve 2b can continue to move towards 100 % open or the next stop. In this way, the risks for unintentional pressure peaks are significantly reduced even during malfunctions or deviations from the intended opening/closing procedure.