Automation of the booster pumping station. The basic work program of the module (discipline) "Operation of pumping and compressor stations" Recommended list of dissertations

The basis of energy efficient use pumping equipment is the coordinated work on the network, i.e. the duty point must be within the operating range of the pump curve. Fulfillment of this requirement allows the pumps to be operated with high efficiency and reliability. The duty point is determined by the characteristics of the pump and the system in which the pump is installed. In practice, many water supply organizations are faced with the problem of inefficient operation of pumping equipment. Often, the efficiency pumping station significantly lower efficiency. pumps installed on it.

Studies show that, on average, the efficiency pumping systems is 40%, and 10% of pumps operate with efficiency. below 10%. This is mainly due to oversizing (selection of pumps with larger flow and pressure values ​​than required for the operation of the system), regulation of pump operating modes using throttling (i.e. valve), wear and tear of pumping equipment. The choice of a pump with large parameters has two sides.

As a rule, in water supply systems, the water consumption schedule varies greatly depending on the time of day, day of the week, season. At the same time, the station must ensure maximum water consumption in normal mode during peak loads. Often, the need to supply water for the needs of fire extinguishing systems is added to this. In the absence of regulation, the pump cannot operate effectively over the entire range of water consumption changes.

The operation of pumps in conditions of changing the required flow rates in a wide range leads to the fact that the equipment operates outside the working area most of the time, with low efficiency values. and low resources. Sometimes the efficiency pumping stations is 8-10%, while the efficiency pumps installed on them in the operating range is over 70%. As a result of such operation, consumers have a false opinion about the unreliability and inefficiency of pumping equipment. And given the fact that a significant proportion of it is made up of pumps of domestic production, a myth arises about the unreliability and inefficiency of domestic pumps. At the same time, practice shows that a number of domestic pumps in terms of reliability and energy efficiency are not inferior to the best world analogues. There are many ways to optimize energy consumption, the main ones are shown in Table 1.

Table 1. Methods for reducing the energy consumption of pumping systems

The effectiveness of one or another method of regulation is largely determined by the characteristics of the system and the schedule of its change over time. In each case, it is necessary to make a decision depending on the specific features of the operating conditions. For example, the recent widespread regulation of pumps by changing the frequency may not always lead to a reduction in energy consumption. Sometimes this backfires. The use of a frequency drive has the greatest effect when pumps operate on a network with a predominance of the dynamic component of the characteristic, i.e. losses in pipelines and shut-off and control valves. The use of cascade control by turning on and off the required number of pumps installed in parallel has the greatest effect when working in systems with a predominantly static component.

Therefore, the main initial requirement for carrying out measures to reduce energy consumption is the characteristics of the system and its change over time. The main problem in the development of energy saving measures is related to the fact that at existing facilities the network parameters are almost always unknown, and differ greatly from the design ones. The differences are associated with a change in network parameters due to corrosion of pipelines, water supply schemes, water consumption volumes, etc.

To determine the actual operating modes of pumps and network parameters, it becomes necessary to measure directly at the facility using special control and measuring equipment, i.e. conducting a technical audit of the hydraulic system. For the successful implementation of measures aimed at improving the energy efficiency of installed equipment, it is necessary to have as complete information as possible about the operation of the pumps and take it into account in the future. In general, there are several specific successive stages of the audit of pumping equipment.
1. Collection of preliminary information on the composition of the equipment installed at the facility, incl. information about the technological process in which pumps are used (stations of the first, second, third lifts, etc.)
2. Clarification on the spot of previously received information about the composition of the installed equipment, the possibility of obtaining additional data, the availability of measuring instruments, the control system, etc. Preliminary planning for testing.
3. Testing at the facility.
4. Processing and evaluation of results.
5. Preparation of a feasibility study for various options modernization.

Table 2. Causes of increased energy consumption and measures to reduce it

Rice. 1. The operation of the pump on the network with a predominant static component with frequency regulation

Rice. 2. The operation of the pump on the network with predominant friction losses with frequency regulation

During the initial visit to the site, it is possible to identify "problematic", in terms of energy consumption, pumps. Table 2 shows the main signs that may indicate inefficient operation of pumping equipment and typical measures that can correct the situation, indicating the approximate payback period for energy saving measures.

As a result of the test, the following information should be obtained:
1. Characteristics of the system and its changes over time (hourly, daily, weekly charts).
2. Determination of the actual characteristics of the pumps. Determination of pump operating modes for each of the characteristic modes (the longest mode, maximum, minimum flow).

The assessment of the application of various modernization options and the method of regulation is taken on the basis of the calculation of the life cycle cost (LCC) of the equipment. The main share in the life cycle costs of any pumping system is the cost of electricity. Therefore, at the stage of preliminary evaluation of various options, it is necessary to use the specific power criterion, i.e. the power consumed by the pumping equipment, related to the unit flow rate of the pumped liquid.

conclusions:
The tasks of reducing the energy consumption of pumping equipment are solved, first of all, by ensuring the coordinated operation of the pump and the system. The problem of excessive energy consumption of pumping systems in operation can be successfully solved by upgrading to meet this requirement.

In turn, any modernization activities must be based on reliable data on the operation of pumping equipment and system characteristics. In each case, it is necessary to consider several options, and as a tool for choosing the best option, use the method of estimating the life cycle cost of pumping equipment.

Alexander Kostyuk, Candidate of Physical and Mathematical Sciences, Director of the Water Pump Program;
Olga Dibrova, engineer;
Sergey Sokolov, lead engineer. LLC "MC "HMS Group"

1. Analytical review of the fundamentals of pumping theory, pumping equipment and technology for solving problems of creating and increasing pressure in water supply and distribution systems (WDS).

1.1. Pumps. Classification, basic parameters and concepts. The technical level of modern pumping equipment.

1.1.1. Basic parameters and classification of pumps.

1.1.2. Pumping equipment for increasing pressure in water supply.,

1.1.3. An overview of innovations and improvements in pumps from the point of view of their application practice.

1.2. Technology for the use of superchargers in SPRV.

1.2.1. Pump stations of water supply systems. Classification.

1.2.2. General schemes and methods for regulating the operation of pumps with increasing pressure.

1.2.3. Optimizing blower performance: speed control and synergy.

1.3. Problems of providing pressure in external and internal water supply networks.

1.4. Conclusions but chapter.

2. Ensuring the required pressure in external and internal water supply networks. Increasing components of SPRS at the level of district, quarterly and internal networks.

2.1. General directions of development in the practice of using pumping equipment to increase pressure in water supply networks.

2.2. Problems of providing the required pressure in water supply networks.

2.2.1. a brief description of SPRV (on the example of St. Petersburg).

2.2.2. Experience in solving problems of increasing pressure at the level of district and quarterly networks.

2.2.3. Features of the problems of increasing pressure in internal networks.

2.3. Statement of the problem of optimizing boosting components

SPRS at the level of district, quarterly and internal networks.

2.4. Chapter conclusions.

3. Mathematical model for optimizing pumping equipment at the peripheral level of the SPRS.

3.1. Static optimization of pumping equipment parameters at the level of district, quarterly and internal networks.

3.1.1. general description structures of the district water supply network in solving problems of optimal synthesis.

3.1.2. Minimization of energy costs for one mode of water consumption.

3.2. Optimization of the parameters of pumping equipment at the peripheral level of the water supply system when changing the mode of water consumption.

3.2.1. Multi-mode modeling in the problem of minimizing energy costs (general approaches).

3.2.2. Minimization of energy costs with the possibility of controlling the speed (wheel speed) of the supercharger.

3.2.3. Minimization of energy costs in the case of cascade-frequency regulation (control).

3.3. Simulation model for optimizing the parameters of pumping equipment at the peripheral level of the PRS.

3.4. Chapter conclusions.

4". Numerical methods for solving problems of optimizing the parameters of pumping equipment.

4.1. Initial data for solving problems of optimal synthesis.

4.1.1. Studying the water consumption regime by the methods of time series analysis.

4.1.2. Determination of the regularity of the time series of water consumption.

4.1.3. Frequency distribution of costs and coefficients of uneven water consumption.

4.2. Analytical representation of the performance of pumping equipment.

4.2.1. Modeling the performance of individual blowers

4.2.2. Identification of the performance characteristics of blowers in the composition of pumping stations.

4.3. Finding the optimal objective function.

4.3.1. Optimal search using gradient methods.

4.3.2. Modified Holland plan.

4.3.3. Implementation of the optimization algorithm on a computer.

4.4. Chapter conclusions.

5. Comparative effectiveness of the boosting components of the PDS based on life cycle cost assessment using MIC for parameter measurement).

5.1. Methodology for assessing the comparative effectiveness of boosting components in the peripheral areas of the SPWS.

5.1.1. Life cycle cost of pumping equipment.

5.1.2. The criterion for minimizing the total discounted costs for evaluating the effectiveness of the incremental components of the PDS.

5.1.3. Objective function of the express model for optimizing the parameters of pumping equipment at the peripheral level of the PDS.

5.2. Optimization of step-up components in the peripheral sections of the water supply system during reconstruction and modernization.

5.2.1. Water supply control system using a mobile measuring complex MIK.

5.2.2. Expert evaluation of the results of measuring the parameters of the pumping equipment of the PNS using the MIC.

5.2.3. Simulation model of the life cycle cost of PNS pumping equipment based on parametric audit data.

5.3. Organizational issues of implementation of optimization solutions (final provisions).

5.4. Chapter conclusions.

Recommended list of dissertations

• Energy-saving methods for selecting parameters and optimizing the control of a group of vane blowers in non-stationary technological processes 2008, Doctor of Technical Sciences Nikolaev, Valentin Georgievich

• Energy-saving methods for controlling the operating modes of pumping units of water supply and sanitation systems 2010, Doctor of Technical Sciences Nikolaev, Valentin Georgievich

• Improving methods for calculating water supply and distribution systems in conditions of multi-mode and incomplete initial information 2005, doctor of technical sciences Karambirov, Sergey Nikolaevich

• Automatic control of material flows in engineering life support systems 1999, candidate of technical sciences Abdulkhanov, Nail Nazymovich

• Development of functional and structural diagnostic models for optimizing water supply and distribution systems 2006, candidate of technical sciences Selivanov, Andrey Sergeevich

Introduction to the thesis (part of the abstract) on the topic "Optimization of pumping stations of water supply systems at the level of district, quarterly and intra-house networks"

Similar theses in the specialty "Water supply, sewerage, building systems for the protection of water resources", 05.23.04 VAK code

• Development of methods for diagnostics and operational management of water supply and distribution systems (WDS) in emergency conditions 2002, candidate of technical sciences Zaiko, Vasily Alekseevich

• Experimental and numerical simulation of transient processes in circular water supply networks 2010, candidate of technical sciences Likhanov, Dmitry Mikhailovich

• Analysis, technical diagnostics and renovation of water supply and distribution systems based on the principles of energy equivalent 2002, Doctor of Technical Sciences Shcherbakov, Vladimir Ivanovich

• Improving the methods of hydraulic calculation of water supply and distribution systems 1981, candidate of technical sciences Karimov, Rauf Khafizovich

• Energy-saving regulation of the operation mode of the main drainage installations of mines and mines by means of an electric drive 2010, Candidate of Technical Sciences Bochenkov, Dmitry Alexandrovich

Dissertation conclusion on the topic "Water supply, sewerage, building systems for the protection of water resources", Steinmiller, Oleg Adolfovich

List of references for dissertation research candidate of technical sciences Steinmiller, Oleg Adolfovich, 2010

Please note the above scientific texts posted for review and obtained through recognition of original texts of dissertations (OCR). In this connection, they may contain errors related to the imperfection of recognition algorithms. There are no such errors in the PDF files of dissertations and abstracts that we deliver.

The fulfillment of this task is based on carrying out full-scale tests of pumping units, which are carried out on the basis of the developed methodology for diagnosing pumping stations, shown in fig. 14.
To optimize the operation of pumping units, it is necessary to determine their efficiency and specific power consumption by means of full-scale tests of pumping units, which will make it possible to assess the economic efficiency of the pumping station.
After definitions of efficiency pumping units is determined by the efficiency of the pumping station, from where it is easy to proceed to the selection of the most economical modes operation of pumping units, taking into account dis-
station feed rate, standard sizes installed pumps and the allowable number of their inclusions and deactivations.
Ideally, to determine the efficiency of a pumping station, you can use the data obtained
direct measurements during full-scale testing of pumping units, for which it will be necessary to perform full-scale tests at 10-20 delivery points in the operating range of the pump at various valve opening values ​​(from 0 to 100%).
When carrying out field tests of pumps, the speed of the impeller should be measured, especially in the presence of frequency controllers, since the current frequency is directly proportional to the engine speed.
According to the test results, the actual characteristics are built for these particular pumps.
After determining the efficiency of individual pumping units, the efficiency of the pumping station as a whole is calculated, as well as the most economical combinations of pumping units or their modes of operation.
To assess the characteristics of the network, you can use the data of automated accounting of costs and pressures for the main water conduits at the outlet of the station.
An example of filling out forms for field testing of a pumping unit is presented in Appendix. 4, graphs of the actual performance of the pump - in App. 5.
The geometric meaning of optimizing the operation of a pumping station lies in the selection of working pumps that most accurately meet the needs of the distribution network (flow rate, head) in the considered time intervals (Fig. 15).
As a result of this work, a reduction in electricity consumption by 5-15% is provided, depending on the size of the station, the number and sizes of installed pumps, as well as the nature of water consumption.

Source: Zakharevich, M. B. Improving the reliability of water supply systems based on the introduction of safe forms of organizing their operation and construction: textbook. allowance. 2011(original)

More on the topic Improving the efficiency of pumping stations:

1. Zakharevich, M. B. / M. B. Zakharevich, A. N. Kim, A. Yu. Martyanova; SPbEASU - SPb., 2011. - 6 Increasing the reliability of water supply systems based on the introduction of safe forms of organization of their operation and construction: textbook. allowance, 2011

Optimization of booster pumping equipment in water supply systems

O. A. Steinmiller, Ph.D., CEO CJSC Promenergo

Problems in providing pressure in the water supply networks of Russian cities, as a rule, are homogeneous. The condition of the main networks led to the need to reduce pressure, as a result of which the task arose to compensate for the pressure drop at the level of district, quarterly and intra-house networks. The development of cities and the increase in the height of houses, especially in the case of compacted buildings, require the provision of the required pressure for new consumers, including by equipping high-rise buildings (EPE) with booster pumping units (PPU). The selection of pumps as part of booster pumping stations (PSS) was carried out taking into account the development prospects, the flow and head parameters were overestimated. It is common to bring pumps to the required characteristics by throttling valves, leading to excessive consumption of electricity. Pumps are not replaced on time, most of them operate with low efficiency. Wear and tear of equipment has exacerbated the need for reconstruction of the PNS to increase efficiency and reliability.

The combination of these factors leads to the need to determine the optimal parameters of the PNS with the existing restrictions on the inlet pressures, under conditions of uncertainty and uneven actual flow rates. When solving such a problem, the questions arise of combining the sequential operation of groups of pumps and the parallel operation of pumps combined within a group, as well as combining the operation of parallel-connected pumps with variable frequency drive (VFD) and, ultimately, the selection of equipment that provides the required parameters of a particular system. Significant changes in recent years in approaches to the selection of pumping equipment should be taken into account - both in terms of eliminating redundancy and in terms of the technical level of available equipment.

The particular relevance of these issues is determined by the increased importance of solving energy efficiency problems, which was confirmed in the Federal Law of the Russian Federation of November 23, 2009 No. 261-FZ "On Energy Saving and Energy Efficiency and on Amendments to Certain Legislative Acts of the Russian Federation".

The entry into force of this law became a catalyst for widespread enthusiasm for standard solutions to reduce energy consumption, without assessing their effectiveness and feasibility in a particular place of implementation. One of such solutions for utility companies was to equip the existing pumping equipment in water supply and distribution systems with VFD, which is often morally and physically worn out, has excessive characteristics, and is operated without taking into account the actual modes.

Analysis of the technical and economic results of any planned modernization (reconstruction) requires time and staff qualifications. Unfortunately, the leaders of most municipal water utilities experience a shortage of both, when, in the conditions of constant extreme underfunding, they have to quickly master the miraculously obtained funds allocated for technical “re-equipment”.

Therefore, realizing the scale of the orgy of thoughtless introduction of VFD on pumps of booster water supply systems, the author decided to present this issue for wider discussion by specialists involved in water supply issues.

The main parameters of the pumps (blowers), which determine the range of change in the operating modes of pumping stations (PS) and FPU, the composition of the equipment, design features and economic indicators are pressure, flow, power and efficiency (COP). For the tasks of increasing the pressure in the water supply, it is important to connect the functional parameters of the blowers (flow, pressure) with the power ones:

where p is the density of the liquid, kg/m3; d - free fall acceleration, m/s2;

O - pump flow, m3/s; H - pump head, m; Р - pump pressure, Pa; N1, N - useful power and pump power (coming to the pump through the transmission from the engine), W; Nb N2 - input (consumed) and output (issued for transmission) engine power.

The efficiency of the pump n h takes into account all types of losses (hydraulic, volumetric and mechanical) associated with the conversion of the mechanical energy of the engine into the energy of a moving fluid by the pump. To evaluate the pump assembly with the engine, the efficiency of the unit na is considered, which determines the feasibility of operation when the operating parameters (pressure, flow, power) change. The value of efficiency and the nature of its change are essentially determined by the purpose of the pump and design features.

The design variety of pumps is great. Based on the complete and logical classification adopted in Russia, based on differences in the principle of operation, in the group of dynamic pumps, we single out vane pumps used in water supply and sewerage facilities. Vane pumps provide smooth and continuous flow with high efficiency, have sufficient reliability and durability. The operation of vane pumps is based on the force interaction of the vanes of the impeller with the flow around the pumped fluid, the differences in the mechanism of interaction due to the design lead to a difference in the performance of vane pumps, which are divided in the direction of flow into centrifugal (radial), diagonal and axial (axial).

Taking into account the nature of the tasks under consideration, centrifugal pumps are of greatest interest, in which, when the impeller rotates, each part of the liquid with a mass m located in the interblade channel at a distance r from the shaft axis will be affected by the centrifugal force Fu:

where w is the angular velocity of the shaft, rad./s.

Methods for regulating the operating parameters of the pump

Table 1

the greater the speed n and the diameter of the impeller D.

The main parameters of the pumps - flow Q, head R, power N, efficiency I] and speed p - are in a certain relationship, which is reflected in the characteristic curves. The characteristic (energy characteristic) of the pump is a graphically expressed dependence of the main energy indicators on the supply (at a constant impeller speed, viscosity and density of the medium at the pump inlet), see fig. 1.

The main characteristic curve of the pump (operating characteristic, operating curve) is a graph of the dependence of the head developed by the pump on the flow H \u003d f (Q) at a constant speed n \u003d const. The maximum value of efficiency qmBX corresponds to the flow Qp and the head Hp at the optimal operating point P characteristics Q-H(Fig. 1-1).

If the main characteristic has an ascending branch (Fig. 1-2) - an interval from Q \u003d 0 to 2b, then it is called an ascending one, and the interval is an area of ​​unstable operation with sudden changes in feed, accompanied by strong noise and water hammer. Characteristics that do not have an increasing branch are called stable (Fig. 1-1), the mode of operation is stable at all points of the curve. "A stable curve is needed when two or more pumps need to be used at the same time" which makes economic sense in pumping applications. The shape of the main characteristic depends on the speed factor of the pump ns - the larger it is, the steeper the curve.

With a stable flat characteristic, the pump head changes slightly when the flow changes. Pumps with flat characteristics are needed in systems where, at a constant pressure, a wide regulation of the supply is required, which corresponds to the task of increasing the pressure in the end sections of the water supply network

On quarterly PNS, as well as in the PNU of local swaps. For the working part of the Q-H characteristic, the dependence is common:

where a, b are selected constant coefficients (a>>0, b>>0) for a given pump within the Q-H characteristic, which has a quadratic form.

The pumps are connected in series and in parallel. When installed in series, the total head (pressure) is greater than each of the pumps develops. Parallel installation provides more flow than each pump separately. The general characteristics and basic relationships for each method are shown in fig. 2.

When a pump with a Q-H characteristic is operating on a pipeline system (adjacent conduits and a further network), pressure is required to overcome the hydraulic resistance of the system - the sum of the resistances of individual elements that resist flow, which ultimately affects pressure losses. In general, one can say:

where ∆H - head loss on one element (section) of the system, m; Q - fluid flow rate passing through this element (section), m3/s; k - head loss coefficient, depending on the type of element (section) of the system, C2 / M5

The characteristic of the system is the dependence of hydraulic resistance on flow. The joint operation of the pump and the network is characterized by a point of material and energy balance (the point of intersection of the characteristics of the system and the pump) - a working (mode) point with coordinates (Q, i / i), corresponding to the current flow and pressure when the pump is operating on the system (Fig. 3) .

There are two types of systems: closed and open. IN closed systems(heating, air conditioning, etc.) the volume of liquid is constant, the pump is necessary to overcome the hydraulic resistance of the components (pipelines, devices) during the technologically necessary movement of the carrier in the system.

The characteristic of the system is a parabola with a vertex (Q, H) = (0, 0).

Open systems are of interest in water supply, transporting liquid from one point to another, in which the pump provides the required pressure at the points of analysis, overcoming friction losses in the system. It is clear from the characteristics of the system that the lower the flow rate, the lower the friction losses of the ANT and, accordingly, the power consumption.

There are two types of open systems: with a pump below the point of parsing and above the point of parsing. Consider an open system of the 1st type (Fig. 3). To supply from tank No. 1 at the zero mark (lower pool) to the upper tank No. 2 (upper pool), the pump must provide the geometric lifting height H, and compensate for the flow-dependent friction losses of the AHT.

System characteristic

Parabola with coordinates (0; ∆Н,).

In an open system of the 2nd type (Fig. 4)

water under the influence of height difference (H1) is delivered to the consumer without a pump. The height difference between the current liquid level in the tank and the point of analysis (H1) provides a certain flow rate Qr. The pressure due to the height difference is insufficient to provide the required flow rate (Q). Therefore, the pump must add a head H1 to completely overcome the friction loss ∆H1. The characteristic of the system is a parabola with the beginning (0; -H1). The flow rate depends on the level in the tank - when it decreases, the height H decreases, the system characteristic shifts upward and the flow rate decreases. The system reflects the problem of lack of inlet pressure in the network (pressure equivalent to R) to ensure the supply of the required amount of water to all consumers with the required pressure.

the needs of the system change over time (the characteristic of the system changes), the question arises of regulating the parameters of the pump in order to meet current requirements. An overview of methods for changing pump parameters is given in Table. 1.

With choke control and bypass control, both a decrease and an increase in power consumption can occur (depending on the power characteristic centrifugal pump and the position of the operating points before and after the control action). In both cases, the final efficiency is significantly reduced, the relative power consumption per unit of supply to the system increases, and unproductive energy loss occurs. The impeller diameter correction method has a number of advantages for systems with a stable characteristic, while cutting (or replacing) the impeller allows you to bring the pump to the optimal operating mode without significant initial costs, and the efficiency decreases slightly. However, the method is not applicable quickly, when the conditions of consumption and, accordingly, the supply continuously and significantly change during operation. For example, when “a pumping water installation supplies water directly to the network (pumping stations of the 2nd, 3rd lifts, pumping stations, etc.)” and when it is advisable frequency regulation an electric drive using a current frequency converter (FCT), which provides a change in the rotational speed of the impeller (pump speed).

Based on the law of proportionality (conversion formula), it is possible to build a number of pump characteristics in the range of rotational speed change from one Q-H characteristic (Fig. 5-1). Recalculation of coordinates (QA1, HA) of a certain point A of the Q-H characteristic, which takes place at the rated speed n, for frequencies n1

n2.... ni, will lead to points A1, A2.... Ai belonging to the corresponding characteristics Q-H1 Q-H2...., Q-Hi

(Figure 5-1). A1, A2, Ai -, form the so-called parabola of similar modes with a vertex at the origin, described by the equation:

A parabola of similar modes is the locus of points that determine, at different speeds (speeds), the pump operation modes, similar to the mode at point A. Recalculation of point B of the Q-H characteristic at a speed of rotation n to frequencies n1 n2 ni, will give points B1, B2, Bi defining the corresponding parabola of similar regimes (0B1 B) (Fig. 5-1).

Based on the initial position (when deriving the so-called recalculation formulas) on the equality of natural and model efficiency, it is assumed that each of the parabolas of such modes is a line of constant efficiency. This provision is the basis for the use of VFD in pumping systems, which is represented by many as almost the only way to optimize the operating modes of pumping stations. In fact, with a VFD, the pump does not maintain a constant efficiency even on parabolas of such modes, since with an increase in the rotational speed n, the flow rate increases and, in proportion to the squares of the speeds, the hydraulic losses in the pump flow path. On the other hand, mechanical losses are more pronounced at low speeds, when the pump power is low. The efficiency reaches its maximum at the calculated value of the rotational speed n0. With others n, smaller or larger n0, pump efficiency will decrease as deviation increases n from n0. Taking into account the nature of the change in efficiency with a change in speed, marking on the characteristics Q-H1, Q-H2, Q-Hi points with equal values ​​of efficiency and connecting them with curves, we obtain the so-called universal characteristic (Fig. 5-2), which determines the operation of the pump at variable speed, efficiency and pump power for any operating point.

In addition to reducing the efficiency of the pump, one should take into account the decrease in the efficiency of the motor due to the operation of the inverter, which has two components: firstly, the internal losses of the frequency converter and, secondly, the losses at harmonics in the regulated electric motor (due to the imperfection of the sinusoidal current wave during VFD). Efficiency of a modern frequency inverter at nominal frequency alternating current is 95-98%, with a functional decrease in the frequency of the output current, the efficiency of the frequency converter decreases (Fig. 5-3).

Losses in motors due to harmonics produced by VFD (ranging from 5 to 10%) lead to heating of the motor and a corresponding deterioration in performance, as a result, the efficiency of the motor drops by another 0.5-1%.

A generalized picture of the “constructive” losses in the efficiency of the pumping unit during VFD, leading to an increase in specific energy consumption (on the example of the TPE 40-300/2-S pump), is shown in fig. 6 - reducing the speed to 60% of the nominal speed reduces la by 11% relative to the optimal one (at operating points on the parabola of similar modes with maximum efficiency). At the same time, electricity consumption decreased from 3.16 to 0.73 kW, i.e. by 77% (the designation P1, [(“Grundfos”) corresponds to N1, in (1)]. Efficiency with a decrease in speed is provided by a decrease in useful and, accordingly, consumed power.

Conclusion. The decrease in the efficiency of the unit due to "constructive" losses leads to an increase in specific energy consumption even when operating near points with maximum efficiency.

To an even greater extent, the relative energy consumption and efficiency of speed control depend on the operating conditions (type of system and parameters of its characteristics, position of operating points on the pumping curves relative to the maximum efficiency), as well as on the criterion and conditions of regulation. In closed systems, the characteristic of the system can be close to a parabola of similar modes, passing through the points of maximum efficiency for different speeds, because both curves uniquely have a vertex at the origin. IN open systems water supply characteristic of the system has a number of features that lead to a significant difference in its options.

Firstly, the peak of the characteristic, as a rule, does not coincide with the origin of coordinates due to the different static head component (Fig. 7-1). The static head is more often positive (Fig. 7-1, curve 1) and is necessary to raise water to the geometric height in the type 1 system (Fig. 3), but it can also be negative (Fig. 7-1, curve 3) - when the backwater at the inlet to the type 2 system exceeds the required geometric head (Fig. 4). Although zero static head (fig. 7-1, curve 2) is also possible (for example, if the back pressure is equal to the required geometric head).

Secondly, the characteristics of most water supply systems are constantly changing over time.. This refers to the displacements of the top of the characteristic of the system along the axis of pressure, which is explained by changes in the magnitude of the backwater or the magnitude of the required geometric pressure. For a number of water supply systems, due to the constant change in the number and location of actual consumption points in the network space, the position of the dictating point in the field changes, which means a new state of the system, which is described new characteristic with a different curvature of the parabola.

As a result, it is obvious that in, the operation of which is provided by one pump, as a rule, it is difficult to regulate the speed of the pump in unambiguous accordance with the current water consumption (i.e., clearly according to the current characteristics of the system), while maintaining the position of the pump operating points (with such a change in speed) at a fixed parabola of similar regimes passing through points with maximum efficiency.

Especially significant decrease in efficiency during VFD in accordance with the characteristics of the system is manifested in the case of a significant static pressure component (Fig. 7-1, curve 1). Since the characteristic of the system does not coincide with the parabola of such modes, then when the speed decreases (by reducing the frequency of the current from 50 to 35 Hz), the point of intersection of the characteristics of the system and the pump will noticeably shift to the left. A corresponding shift in the efficiency curves will lead to the zone of lower values ​​(Fig. 7-2, "raspberry" points).

Thus, the energy saving potentials for VFD in water supply systems vary significantly. Indicative is the assessment of the efficiency of VFD in terms of specific energy per pumping

1 m3 (Fig. 7-3). Compared to type D discrete control, speed control makes sense in a type C system - with a relatively small geometric head and a significant dynamic component (friction loss). In a B-type system, the geometric and dynamic components are significant, speed control is effective at a certain feed interval. In a type A system with great height lift and a small dynamic component (less than 30% of the required head), the use of VFD is inexpedient in terms of energy costs. Basically, the problem of increasing the pressure at the end sections of the water supply network is solved in mixed-type systems (type B), which requires a substantive justification for the use of VFD to improve energy efficiency.

In principle, speed control makes it possible to expand the range of operating parameters of the pump upwards from the nominal characteristic Q-H. Therefore, some authors suggest choosing a pump equipped with a frequency converter in such a way as to ensure the maximum time of its operation at the nominal characteristic (with maximum efficiency). Accordingly, with the help of VFD, with a decrease in flow, the pump speed decreases relative to the nominal, and with an increase, it increases (at a current frequency above the nominal). However, in addition to the need to take into account the power of the electric motor, we note that pump manufacturers pass over in silence the issue of the practical application of long-term operation of pump motors with a current frequency that is significantly higher than the nominal one.

The idea of ​​control according to the characteristics of the system, which reduces excess pressure and the corresponding excess energy consumption, is very attractive. But it is difficult to determine the required pressure from the current value of the changing flow rate due to the variety of possible positions of the dictating point in the current state of the system (when the number and location of consumption points in the network, as well as the flow rate in them) and the top of the system characteristic on the pressure axis (Fig. 8- 1). Before the mass application of instrumentation and data transmission, only “approximation” of control by characteristic is possible on the basis of network-specific assumptions that specify a set of dictating points or limit the system characteristic from above depending on the flow rate. An example of such an approach is the 2-position regulation (day/night) of the outlet pressure in the PNS and PNU.

Taking into account the significant variability in the location of the top of the system characteristic and in the current position in the field of the dictating point, as well as its uncertainty in the network diagram, we have to conclude that today in most spatial water supply systems, control is applied according to the criterion constant pressure(Fig. 8-2, 8-3). It is important that when the flow rate Q decreases, excess pressures are partially preserved, which are the greater, the more to the left of the operating point, and the decrease in efficiency with a decrease in the speed of the impeller, as a rule, will increase (if the maximum efficiency corresponds to the intersection point of the pump characteristic at nominal frequency and line set constant pressure).

Recognizing the potential for reducing power input and output in speed control to better suit the needs of the system, it is necessary to determine the actual efficiency of a VFD for a particular system by comparing or combining this method with other effective methods of reducing energy costs, and primarily with a corresponding reduction in feed rates and / or head per pump with an increase in their number.

An illustrative example of a circuit of parallel and series-connected pumps (Fig. 9), providing a significant number of operating points in a wide range of pressures and flows.

With an increase in pressure in sections of water supply networks close to consumers, questions arise about the combination of sequential operation of groups of pumps and parallel operation of pumps combined within one group. The use of VFD also raised questions of optimal combination of the operation of a number of parallel-connected pumps with frequency control

When combined, high comfort for consumers is ensured due to soft start / stop and stable pressure, as well as a reduction in installed power - often the number of standby pumps does not change, and the nominal value of power consumption per pump is reduced. The power of the PCT and its price are also reduced.

In essence, the consideration is clear that the combination (Fig. 10-1) allows you to cover the necessary part of the working area of ​​the field. If the selection is optimal, then in most of the working area, and primarily on the line of controlled constant pressure (pressure), the maximum efficiency of most pumps and the pumping unit as a whole is ensured. The subject of discussion of the joint operation of parallel-connected pumps in combination with a VFD is often the question of the expediency of equipping each pump with its own frequency converter.

An unambiguous answer to this question will not be accurate enough. Of course, those who claim that equipping each pump with a PST increase the possible space for the location of operating points for installation are right. They may also be right who believe that when the pump is operating in a wide range of feeds, the operating point is not at the optimum efficiency, and when 2 such pumps operate at a reduced speed, the overall efficiency will be higher (Fig. 10-2). This view is shared by the suppliers of pumps equipped with built-in frequency converters.

In our opinion, the answer to this question depends on the specific type of characteristics of the system, pumps and installation, as well as on the location of the operating points. With constant pressure control, no increase in operating point space is required, and therefore a plant equipped with a single VST in the control box will operate similarly to a plant with each pump fitted with a VST. To ensure higher technological reliability, it is possible to install a second PCT in the cabinet - a backup one.

At correct selection(maximum efficiency corresponds to the point of intersection of the main characteristic of the pump and the constant pressure line) The efficiency of one pump operating at nominal frequency (in the zone of maximum efficiency) will be higher than the total efficiency of two of the same pumps providing the same operating point when each of them operates at a reduced speed (Figure 10-3). If the operating point lies outside the characteristics of one (two, etc.) pumps, then one (two, etc.) pump will operate in the “network” mode, having a working point at the intersection of the pump characteristics and the constant pressure line ( with maximum efficiency). And one pump will work with the VST (having a lower efficiency), and its speed will be determined by the current supply requirement of the system, ensuring that the operating point of the entire installation is properly localized on the constant pressure line.

It is advisable to select the pump in such a way that the constant pressure line, which also determines the operating point with maximum efficiency, intersects with the pressure axis as high as possible relative to the pump characteristic lines determined for reduced speeds. This corresponds to the above statement on the use of pumps with stable and flat characteristics (if possible, with a lower speed coefficient ns) when solving problems of increasing the pressure in the end sections of the network of pumps.

Under the condition “one pump in operation...”, the entire flow range is provided by one pump (in operation in this moment) with adjustable speed, so most of the time the pump operates with less than the nominal flow and, accordingly, at a lower efficiency (Fig. 6, 7). Currently, there is a strong intention of the customer to limit himself to two pumps in the installation (one pump is working, one is standby) in order to reduce initial costs.

Operating costs influence the choice to a lesser extent. At the same time, for the purpose of “reinsurance”, the customer often insists on the use of a pump whose nominal delivery value exceeds the calculated and / or measured flow rate. In this case, the selected option will not correspond to the actual water consumption regimes over a significant period of the day, which will lead to excessive consumption of electricity (due to lower efficiency in the most “frequent” and wide supply range), reduce the reliability and durability of the pumps (due to frequent reaching at least 2"in of the allowable flow range, for most pumps - 10% of the nominal value), will reduce the comfort of water supply (due to the frequency of the stop and start function). As a result, recognizing the "external" validity of the customer's arguments, one has to accept as a fact the redundancy of most newly installed booster pumps on internal ones, which leads to a very low efficiency of pumping units. The use of VFD in this case provides only a part of the possible savings in operation.

The trend of using two pumping PNUs (one - working, one - reserve) is widely manifested in new housing construction, because. neither design nor construction and installation organizations are practically interested in the operational efficiency of the engineering equipment of housing being built, the main optimization criterion is the purchase price while ensuring the level of the control parameter (for example, flow and pressure at a single dictating point). Most of the new residential buildings, taking into account the increased number of storeys, are equipped with PNU. The company headed by the author ("Promenergo") supplies PNU both manufactured by "" and its own production based on Grundfos pumps (known under the name MANS). The statistics of Promenergo's deliveries in this segment for 4 years (Table 2) allows us to note the absolute predominance of two pumping FPU, especially among plants with VFD, which will mainly be used in drinking water supply systems, and primarily residential buildings.

In our opinion, the optimization of the composition of the PPU, both in terms of electricity costs and in terms of reliability, raises the question of increasing the number of working pumps (with a decrease in the supply of each of them). Efficiency and reliability can only be ensured by a combination of step and smooth (frequency) control.

An analysis of the practice of booster pumping systems, taking into account the capabilities of modern pumps and control methods, taking into account the limited resources, made it possible to propose, as a methodological approach to optimizing the PNS (PNU), the concept of peripheral modeling of water supply in the context of reducing energy intensity and the cost of the life cycle of pumping equipment. Mathematical models have been developed to rationally select the parameters of pumping stations, taking into account the structural relationship and the multi-mode nature of the functioning of the peripheral elements of the water supply system. The model solution allows justifying the approach to choosing the number of blowers in the PNS, which is based on the study of the life cycle cost function depending on the number of blowers in the PNS. When studying a number of operating systems using the model, it was found that in most cases the optimal number of working pumps in the PNS is 3-5 units (subject to the use of VFD).

Literature

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M.: Stroyiz-dat, 1986. - 320 p.

3. Karttunen E. Water supply II: per. from Finnish / E. Karttunen; Association of Civil Engineers of Finland RIL g.u. - St. Petersburg: New magazine, 2005 - 688 p.

4. Kinebas A.K. Optimization of water supply in the zone of influence of the Uritskaya pumping station of St. Petersburg / A.K. Kinebas, M.N. Ipatko, Yu.V. Ruksin et al.//VST. - 2009. - No. 10, part 2. - p. 12-16.

5. Krasilnikov A. Automated pumping units with cascade-frequency control in water supply systems [Electronic resource]/A. Krasilnikova/Construction engineering. - Electron, yes. - [M.], 2006. - No. 2. - Access mode: http://www.archive-online.ru/read/stroing/347.

6. Leznov B.S. Energy saving and adjustable drive in pumping and blower installations / B.S. Leznov. - M.: Energoatom-published, 2006. - 360 p.

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8. Industrial pumping equipment. - M.: Grundfos LLC, 2006. - 176 p.

9. Steinmiller O.A. Optimization of pumping stations of water supply systems at the level of district, quarterly and intra-house networks: abstract of the thesis. dis. ... cand. tech. Sciences / O.A. Steinmiller. - St. Petersburg: GASU, 2010. - 22 p.

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Director of the Institute of Natural Resources

A.Yu. Dmitriev

Basic work program of the module (discipline) "Operation of pumping and compressor stations"

Direction (specialty) PEP 21.03.01 "Oil and gas business"

Cluster number ( for unified disciplines)

Profile(s) of training (specialization, program)

« Operation and maintenance of transport and storage facilities for oil, gas and refined products»

Qualification (degree) Bachelor

Basic Admission Curriculum 2014 G.

Well 4 semester 7

Amount of credits 6

Discipline code B1.VM5.1.4

Correspondence form of education

Type of intermediate certification exam

Supporting unit Department of THNG IPR

2014

1. The objectives of mastering the module (discipline)

As a result of mastering the discipline B1.VM5.1.4 "Operation of pumping and compressor stations", the bachelor acquires knowledge, skills and abilities that ensure the achievement of the goals of C1, C3, C4, C5 of the BEP 21.03.01 "Oil and Gas Business":

The overall goal of studying the discipline is the acquisition by students of basic knowledge related to the operation of pumping and compressor stations.

The study of the discipline will allow students to acquire the necessary knowledge and skills in the field of pumps and compressors. Acquire knowledge, skills and abilities in the design, construction and operation of pumps and compressors and their ancillary equipment.