DK181198B1

DK181198B1 - Method and system for pressure regulation in a fluid supply network

Info

Publication number: DK181198B1
Application number: DKPA202100926A
Authority: DK
Inventors: Krantz Jensen Allan
Original assignee: Agerkrantz Controls Aps
Priority date: 2021-09-29
Filing date: 2021-09-29
Publication date: 2023-04-25
Also published as: DK202100926A1; WO2023051886A1

Abstract

A method for altering the pressure of a liquid supply network 2, wherein the supply network comprises a central plant 4, wherein the central plant 4 acts as the central location in the supply network 2, wherein liquid is pumped from the central plant 4 to the desired location within the network 2, wherein the network 2 further comprises a central control unit 42, a main pumping unit 8, and a plurality of supply pipes 10 and booster pumping units 12 connected to the supply pipes 10, wherein the supply pipes 10 are connected to the central plant 4, and wherein the central control unit 6 is arranged to regulate the pressure of the liquid that is distributed within the supply network 2 by providing instruction to the main pumping units 8 and booster pumping units 12. The method comprises the following steps: - locate the location of the central pumps 8 and the booster pumps 12; - for the central pump 8 and each of the booster pumps 12 measure at a local Maximum Pressure Point 22, - for the central pump 8 and each of the booster pumps 12 measure at an index point 20, wherein each index point corresponds to the location in the pipeline 10, - transmitting the measured pressure values (24) to an adjustment unit (26), wherein the adjustment unit (26) is configured to provide an adjustment signal (56) to the central control unit (6), - the adjustment signal (56) is provided based on a set of pre-set criteria, wherein the pre-set criteria are based on an aimed pressure value (34), a security maximum pressure value (32) and a security minimum pressure value (30).

Description

DK 181198 B1 1

Field of invention

The present invention relates to a method for controlling a water distribution system. The present invention also relates to a water distribution system with differential pressure sensors.

Prior art

Supply networks providing water and heating are integrated parts of modern cities, especially district heating has become commonplace in modern times. However, as the supply network is expanded upon as a city expands, a higher pressure is needed to ensure that the pressure is maintained even in the outskirts of the supply lines.

However, prior art supply networks are overly conservative by having a much higher pressure than needed, and while some systems have sensors for measuring the pressure, these are often placed in a wired connection with the originally built structure and therefore do not give an accurate reading of the pressure in the outskirts of the supply lines.

Thus, prior art systems can be more energy and cost-efficient by improving the pressure settings.

A method introduced in recent years is an Internet of Things (IoT) approach wherein smart sensors are placed in the buildings in the network.

While these technologies allow for a large data gathering and optimization on the basis of this, there is a large drawback in the high implementation cost, as the majority of buildings connected to the piping infrastructures need to be monitored in order to get sufficient

DK 181198 B1 2 and precise data.

Thus, there is a need for a method and an apparatus which enables better and more accurate pressure control for a liquid distribution system, while having a low implementation cost.

EP247607 Al discloses a solution for this issue. The system works by placing multiple sensors in so-called critical points, wherein said critical points respond to the expected lowest value, using this data from these critical points.

While this disclosed system provides low implementation cost, an alternative that provides more accurate pressure control and more flexibility is desired.

Summary of the invention

The object of the present invention can be achieved by a method as defined in claim 1 and a system as defined in claim 6. Preferred embodiments are defined in the dependent subclaims, explained in the following description and illustrated in the accompanying drawings.

The object of the invention can be obtained by using a method, wherein the method is a method for altering the pressure of a liquid supply network, wherein the supply network comprises a central plant, wherein the central plant acts as the central location in the supply network, wherein liquid is pumped from the central plant to the desired location within the network, wherein the network further comprises a central control unit, a main pumping unit, and a plurality of supply pipes and booster pumping units connected to the supply pipes, wherein the supply pipes are connected to the central plant, and wherein the central control unit is arranged to regulate the pressure of the liquid that is distributed within the supply network by providing instruction to the

DK 181198 B1 3 main pumping units and booster pumping unit, wherein the method comprises the following steps: - locate the central pumps and the booster pumps; - for the central pump and each of the booster pump measure a pressure value, at a local Maximum Pressure Point, wherein said Maximum Pressure Point for the central pump is placed after the central pumps outlet for the central pump and each of the booster pumps measure at an index point, wherein the relatively lowest pressure is measured, - Transmitting the measured pressure values to an adjustment unit, wherein the adjustment unit is configured to provide an adjustment signal to the central control unit, - The adjustment signal is provided based on a set of pre-set criteria, wherein the pre-set criteria are based on an aimed pressure value, a security maximum pressure value and a security minimum pressure value. - adjust the speed of the central pump and the booster pump based on the adjustment signal.

Hereby, a method that allows for accurate regulation of the pressure without a high implementation cost is obtained.

By the term “liquid supply network” is meant any system that supplies liquid from one or more central locations to another location within a connected network e.g. a water distribution system wherein water is transported from a central plant to houses or a district heating system wherein typically a heated brine solution is transported to buildings to keep them heated.

The concept of an index point is explained in detail under the section “Detailed description of the invention”.

DK 181198 B1 4

In a standardized network, it is expected that a change caused by adjusting the pumps can be registered within 10 seconds, and even for larger systems less than 1 minute.

Therefore, the system can run continuously even while receiving data from the pressure sensors.

As such, the system is able to alternate pressure in real-time.

Each of the terms “aimed pressure value, security maximum pressure value and security minimum pressure value” are to be understood as not literal pressure values but a corresponding value that the computer can relate to the value e.g., it can also be a minimum speed of a pump that would correlate to a certain pressure in the pipeline.

By keeping the adjustment signal within certain pre-set values of different pressure, reaching critical pressure levels can be avoided.

As an example, if more than one sensor is used, the control box would send an adjustment signal on the basis of the average set value of the sensors, such that if one sensor shows no value or no change, the pumps will not keep increasing pressure due to an error.

In the same manner, the adjustment signal has built-in limits such that it would not cause the pumps to reduce the pressure too low or increase the pressure too high.

Lastly, when the aimed pressure value has been reached and has remained stable for a predetermined period, no adjustment signal is sent until a deviation from the aimed pressure value is registered.

In general, it is expected in a routine setting that there will be longer

DK 181198 B1 periods where no adjustment is needed, as such the above-mentioned situation is expected to be the norm.

In one embodiment, the pre-set criteria are installed in the control box. 5

In one embodiment, the pre-set criteria are based on set values already in the control box.

In one embodiment, the pre-set criteria are continuously updated and sent by the sensors.

In one embodiment, the system allows a 0.1 bar deviation from the aimed value prior to adjusting the signal.

Having a lowered pressure in a supply network provides a variety of benefits.

Especially, in older systems with an older piping structure small leakages can be a problem.

By reducing the pressure, it is possible to reduce the overall usage (m? of liquid) in the systems, both through less leakage and in general.

Furthermore, in central heating systems the difference in temperate (cooling) has a reciprocal relationship with overall usage (m? of water), and as such a better cooling is obtained when overall usage is lowered, thus improving the overall energy efficiency of the system.

In one embodiment, the liquid distribution system is a district heating system, and the differential pressure is measured.

In one embodiment, the method comprises the steps of

DK 181198 B1 6 - selecting one or more bypasses as a location for measuring pressure. - selecting the one or more bypasses as the index point.

In one embodiment, the measurement of pressure in the bypasses are performed by differential pressure sensors, wherein the differential pressure sensors are built together with a temperature sensor that are configured to measure and wirelessly transmit one or more measured temperature values to the adjustment unit, wherein the adjustment unit is configured to transmit an adjustment signal to the central control unit, wherein the adjustment signal is provided based on a set of pre- set criteria, wherein the pre-set criteria are based on an aimed pressure value, a security maximum value and a security minimum value and an aimed temperature value, a security maximum temperature value and a security minimum temperature value.

In one embodiment, the method comprises the step of locally altering the pressure valves located in the bypasses based on a communication between the central control unit and the sensor.

In one embodiment, the method comprises the following step: - The adjustment unit performs a security check after sending the adjustment signal the second time to avoid a negative feedback loop.

By the term “security check” is meant an action that has the purpose of ensuring that certain restriction criteria are fulfilled.

As an example, the system can delay sending another signal until the central control unit has obtained data from a minimum number of sensors, e.g. four.

Hereby, it is possible to ensure that a negative feedback loop occurs if for example a sensor is faulty and therefore does not register a

DK 181198 B1 7 pressure change.

In one embodiment, the adjustment signal will contain instructions for the control unit to give an alarm in case the security check shows that a measured value is outside the security criteria.

The object of the invention is fulfilled by a system, wherein the system is a liquid supply network comprising: a central plant, comprising a central control unit, a main pumping unit, and a plurality of supply pipes and booster pumping units connected to the supply pipes, wherein the supply pipes are connected and branch off from the central plant, and wherein the central control unit is arranged to regulate the pressure of the water that is distributed in the system by providing instruction to the main pumping units and booster pumping units, wherein the liquid supply network further comprises one or more pressure sensors installed in a selected location in the supply pipes, wherein the selected location corresponds to a maximum pressure point and index point in the supply pipes, wherein the pressure sensors are configured to measure and wirelessly transmit the measured pressure values to an adjustment unit, wherein the adjustment unit is arranged and adjusted to send an adjustment signal to the central control unit, wherein the adjustment signal is based on an aimed pressure value, a security maximum pressure value and a security minimum pressure value.

In one embodiment, the liquid supply network is a district heating system wherein the pressure sensors are differential sensors.

In a district heating system, the central plant is a central heating plant.

In one embodiment, the differential pressure sensors are powered by an energy harvester.

DK 181198 B1 8

In one embodiment, the differential pressure sensors are built together with a temperature sensor, wherein the sensor assembly is configured to be placed in a bypass.

In one embodiment, the sensor assembly also comprises means to regulate the local pressure by using an actuator movement.

In one embodiment, the adjustment is arranged to receive data from the sensor assembly, and the adjustment signal is further based on an aimed temperature value, a security maximum temperature value and a security minimum temperature value.

In one embodiment, the sensor assembly comprises means for performing a security check.

Description of the Drawings

The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:

Fig. 1 shows a schematic view of a prior art system

Fig. 2 shows a schematic view of a liquid supply network with pumps and an index point marked

Fig. 3 shows a schematic view of a city section with a bypass;

Fig. 4 shows a flowchart of the method according to the invention.

DK 181198 B1 9

Detailed description of the invention

Fig. 1 illustrates a schematic overview of a prior art solution.

A typical liquid supply network 2 comprises a central plant 4 connected to buildings through a pipe network 10.

In fig. 1, the triangles represent pressure measurement points 14. Both measurement points 14 are wired to the central plant.

However, as can be seen the pipeline 10 is expanded beyond the measurement's points 14.

The stripped lines represent future building areas as the city further expands.

Such a prior art system has difficulties optimizing the pressure used.

As such, in general a system such as this operates mainly on a caution principle, wherein it is better to use a higher pressure to ensure that the pressure in outer areas is high enough, such that customers do not send in complaints.

In a typical liquid system such as this multiple pumps are used, instead of just a central pump.

Fig. 2 illustrates a liquid supply network, wherein pumps are marked.

In a typical supply network, there is a main (central) pump 8 and multiple booster pumps 12 throughout the supply network.

DK 181198 B1 10

In the centre is the central plant 4 which contains the control central for the system and the central pump 8.

To ensure that the main pump is set at an appropriate level of speed (interval) two measurements points for measuring the output of the central point are chosen.

One is placed right after the central pump’s outlet, in such a manner that maximum pressure is measured, termed Maximum Pressure Point (MPP).

Another point is termed the Index Point (IP).

The Index Point corresponds to the location wherein the relatively lowest pressure is measured.

It is important to note that the location of the index point is not a straightforward matter.

In a water distribution system, the Index Point IP is defined by two factors, the pipe length (D) and the altitude (A).

As a rule of thumb, a long pipe length D in combination with a high- altitude A would result in a low pressure.

However, due to the layout of the piping structure, the selection of an index point is not a simple action.

The index point is selected by finding the point with the highest &R, wherein SR is the loss of pressure.

DK 181198 B1 11

In water distribution systems water is moved from an area of high pressure to lower pressure.

The pressure difference between the high pressure and low pressure point is the pressure difference needed to move a specific amount of water, the relationship is described by:

MEA Es r N N YY ye o NOE

Wherein q is the amount of water [m?/s] and p is pressure [Pa].

The amount of energy needed to transfer (distribute) water to its desired location by moving a pump is given by:

EN

The needed amount of pressure is found by calculating the pressure drop in the pipeline and components such as vents that the water is distributed to.

For a straight pipeline, the loss of pressure during transport can be calculated by using the following formula:

ENS

TERN

Wherein:

A is the friction coefficient. ep is the density of water [kg/m?]. v is the median transfer speed of water [m/s]

L is the pipe length [m] & is the internal diameter of the pipes [m]

DK 181198 B1 12

In a simplified case pipe length is the main determining factor determining where the latest loss of pressure will occur.

In case the liquid transport network is a district heating system, the setup is similar to that of a water distribution system.

The major difference is that the piping system has a recycling mechanism built in such that the heated water from the central plant is pumped back to the central plant after use.

To ensure the backflow is regulated properly bypasses are placed at the ends of the line to ensure a continuous process.

Furthermore, differential pressure is measured instead of static pressure.

In one embodiment the sensor has an additional sensor unit arranged and configured to measure static pressure.

The Index Point IP is selected based on the pipe diameter and length.

The information can be found in GIS (Geographical Information System)

Maps.

In order to ensure Booster pumps is at the correct level, the same setup with two measurements points is selected.

It is also important to note that if the pipelines move through a housing area, there will be a pressure drop and as such, it is better to measure prior to the pipe going to the housing area and get the relative lowest value instead.

DK 181198 B1 13

During operation it is a benefit if control rounds are made in order to ensure that the Index Point is selected correctly.

Thus, by using a map and information related to pipe infrastructure, a skilled person can calculate the Index Point.

The diamond figure 14 represents a schematic point wherein an IP could be placed for the booster pump close to it.

By correlating with the MPP and the IP maximum and minimum threshold values are chosen, such that the pressure is not too high.

Nor should the pressure be too low, as this will have a negative effect for user of the system.

Furthermore, the booster pumps (BP) that are arranged to increase speed in the pipelines further away from the central pump CP (in terms of pipe length D) would need to overcompensate for the decrease in pressure, which could lead to an overall loss of efficiency.

At the measurement points, static pressure sensors are placed that can wirelessly transmit data back to an adjustment unit.

The adjustment unit can either independently or through contact with the central control system adjust the speed of the central pump and the booster pump based on the measured pressure values from the

Maximum Pressure Points MMP and Index Points IP and a set goal value.

In the case of a district heating system, the setup is similar to that of a water distribution system.

The major difference is in that the piping system has a recycling mechanism built in such that the heated water from the central plant is

DK 181198 B1 14 pumped back to the central plant after use.

Furthermore, differential pressure is measured instead of static pressure.

The Index Point IP is selected based on the pipe diameter and length.

The information can be found in GIS (Geographical Information System)

Maps.

In Fig. 3 a schematic view of a city section is shown with bypasses 18.

In some city sections, a booster pump 12 is placed prior to the city section.

It is common for some city sections, especially those further away from the central plant, to have bypasses. Bypasses 18 are used to ensure a continuous flow, even in periods of low activity. As such, bypasses make a for a useful location to place a sensor for measurements of the index point (22).

While a bypass will not always correspond to the lowest possible pressure, it is a place that where it is easy and convenient to mount

Sensors.

DK 181198 B1 15

As a bypass is used in district heating systems, it is also an advantage to collect temperature information to ensure this is regulated as well.

This can be done by using a sensor assembly 16 that is located in a bypass wherein it can measure and transmit pressure and temperature values.

In fig. 4, a flowchart of the method according to the invention is seen.

The first step is (for a skilled user) to locate the central pumps and booster pumps in the liquid transport system.

The second step is to measure at the local maximum pressure points, in most circumstances this point is right at the outlet of the pump.

The third step is to measure at an index point.

The index point is calculated by a skilled user for instance by using a

GIS map to determine an optimal point. A skilled user, however, will take into consideration the current supply network structure in order to measure at an appropriate location.

The fourth step is to transmit the measure information.

The transmitted information is sent to the central control unit.

The information is transmitted as an adjustment signal.

The fifth step is to provide an adjustment based on the received signal.

The specific action taken will depend on the individual system, but it is expected that in the majority of systems the adjustment will consist of

DK 181198 B1 16 the central control system adjusting the speed of the individual pumps.

The sixth step is to perform a check to see if the pre-set criteria is met.

Depending on if the criteria are not met or met it goes to the seventh step.

If the criteria are not met, an additional adjustment signal is sent.

In one embodiment, an additional step of a security check is performed after this step is performed.

If the criteria are met (after a short time), the system awaits a deviation from the aimed value.

Fig. 5 shows a schematic overview of the fourth step to the seventh step, wherein the measured data come from a pressure sensor.

A measurement is taken at index point 20 and local maximum pressure point 22, wherein the sensor data 24 is transmitted to the adjustment unit 26.

The adjustment unit 26 starts a calculation 28 wherein it works within the pre-set criteria.

This is represented by a pressure scale 40 wherein the security maximum pressure 32 and security minimum pressure 30 is represented by bars.

The scale 40 shows the registered measurement value 36 (represented by the circle) and its deviation 38 from the aimed pressure value 34

DK 181198 B1 17 (represented by a star).

Based on the calculation, an adjustment signal 56 is generated and send to the central control unit 42.

Fig. 6 shows a schematic overview of the fourth step to the seventh step, wherein the measured data come from a temperature sensor.

When a temperature is measured, the same procedure is carried out.

The major difference is in the fact that a sensor assembly 16 is used instead of just a pressure sensor.

For instance, a sensor assembly 16 located in a bypass can use this location as the index point 22.

Similar to the case for a pressure measurement, a temperature scale 44 with security maximum temperature 48 and security minimum temperature 46 is used for the calculation 28.

In the same manner as shown in Fig. 6 the deviation of the measured value 54 between the measured temperature value 50 (represented by the square) and the aimed temperature value (represented by the star) is found.

Based on this value, an adjustment signal 56 is sent to the central control unit 42.

The calculation 28 can occur for both temperature and pressure at the same time.

As such, the adjustment signal 56 can contain information relating both

DK 181198 B1 18 to pressure and temperature, if needed.

It is expected that the measured value is within the range between the maximum (32, 48) and minimum value (30, 46).

However, in case the value is in the range of the minimum or maximum values, a security check is made.

If after the security check the measured value is the same, the adjustment signal will contain an alert, such that an operator may be contacted, or an emergency protocol be carried out.

DK 181198 B1 19

List of reference numerals 2 Liquid supply network 4 Central plant 6 Central control unit 8 Main pumping unit

Supply pipes 10 12 Booster pumping units 14 Pressure sensor 16 Sensor assembly 18 Bypasses 20 Index point 22 Maximum pressure point 24 Sensor data 26 Adjustment unit 28 Calculation 30 Security minimum pressure value 32 Security maximum pressure value 34 Aimed pressure value 36 Measured pressure value 38 Deviation from the aimed pressure value 40 Pressure scale 42 Control unit 44 Temperature scale 46 Security minimum temperature value 48 Security maximum temperature value 50 Measured temperature value 52 Aimed temperature value 54 Deviation from the aimed temperature value 56 adjustment signal

Claims

DK 181198 B1 20 Patent claim

1. Method for changing the pressure for a liquid supply network (2), where the supply network comprises a central plant (4), where the central plant (4) functions as a central place in the supply network (2), where liquid is pumped from the central plant (4) to a desired place inside | the network (2), wherein the network (2) further comprises a central control unit {42}, a main pump unit (8) and a plurality of supply pipes (10) and booster pump units (12) connected to the supply pipes (10), where the supply pipes ( 10) is connected to the central plant (4) and where the central control unit {6} is arranged to regulate the pressure of the liquid distributed into the supply network (2) by providing instructions to the main pump units (8) and booster pump units 13 (12), characterized in that the initial procedure includes the following steps: - locating the location of the central pumps (8) and the booster pumps (12); - for the central pump (8) and each of the booster pumps (12), a pressure value (24) is a measurement at a local maximum pressure point (22), for the central pump (8), where — the maximum pressure point (22) of the central pump ( 8) is placed after the discharge of the central pump, and each of the booster pumps (12) measures at an index point (20), where each index point corresponds to the place in the pipeline (10) where the relatively lowest thickness is measured, - transmission of the measured pressure values (24) to an adjustment unit (26), where the adjustment unit (26) is configured to provide an adjustment signal (56) to the central control unit (6), - the adjustment signal (58) is provided based on a set of preset criteria, where the preset criteria are based on a target pressure value (34), a maximum safety pressure value (32) and a minimum safety pressure value (30), m—- adjusting the speed of the central pump and the booster pump based on the adjustment signal (56).

2. Method according to claim 1, characterized in that the liquid distribution system {2} is a district heating system and the differential pressure is measured.

DK 181198 B1 21

3. Method according to claim 2, characterized in that the method comprises the following steps: - selection of one or more diversions (18) as a place for pressure measurement, - selection of one or more diversions (18) as the index point (20).

4, according to Method claim 3, characterized in that the pressure measurement in the diversions is carried out with differential pressure sensors (14), where the differential pressure sensors are built together with a temperature sensor (16) that is configured to measure and wirelessly — send one or more measured temperature values (50) to the adjustment unit (26), where the adjustment unit (26) is configured to send an adjustment signal (56) to the central control unit (6), where the adjustment signal (56) is provided based on a set of preset criteria, where the preset criteria are based on a target pressure value (34), a maximum safety value (32) and a minimum safety value (30) and a target temperature value (52), a maximum safety temperature value (48) and a minimum safety temperature value (46).

5. Method according to one of the preceding claims, characterized in that the method comprises the following steps: - the adjustment unit (26) performs a safety check after sending the adjustment signal (56) the second time to avoid a negative feedback loop.

6. Liquid supply network (2) comprising: a central plant (4) comprising a central control unit (6), a main pump unit (8) and a plurality of supply pipes (10) and booster pump units (12) connected to the supply pipes (10), where the supply pipes (10) are connected and branched from the central plant (4), and where the central control unit (6) is arranged to regulate the pressure of the liquid distributed in the system by providing instructions to the main pump units (8) and the booster pump units (12), characterized in that the liquid supply network (2) further comprises one or more pressure sensors (14) installed at selected locations in the supply pipes (10), where the selected location corresponds to a maximum pressure point (20) and index point (22) in the supply pipes (10), where the pressure sensors (14) are configured to measure and wirelessly send the measured pressure values (24) to an adjustment unit (26), where the adjustment unit (26) is arranged and

DK 181198 B1 22 adjusted to send an adjustment signal (56) to the central control unit (6), where the adjustment signal (56) is based on a target pressure value (34), a maximum safety pressure value (32) and a minimum safety pressure value (30).

7. Liquid supply network according to claim 6, characterized in that the liquid distribution system is a district heating system and where the pressure sensors (14) are differential sensors.

8. Liquid supply network according to claim 7, characterized in that the differential pressure sensors are operated by an energy harvester.

9. Liquid supply network according to claims 7-8, characterized in that the differential pressure sensors (14) are built together with a temperature sensor (16), where the sensor unit (16) is configured to be placed in a diverter (18).

10. Liquid supply network according to claim 9, characterized in that the adjustment unit (26) is arranged to receive data from the sensor unit (16), and in that the adjustment signal (56) is also based on a target temperature value (52), a maximum safety temperature value (48) and a minimum safety temperature value (46).