Monthly: April 2015

Entry.

In the pre-war years and immediately after the war, only foreign-made pumps were used in Polish power plants to power steam boilers. The largest Polish power plant in Łaziska, with a capacity of 1939 MW, until 100, had imported pumps. During the reconstruction of the country after the war damage, power pumps from the USSR were delivered to the Skawina, Żerań, Jaworzno and Stalowa Wola Power Plants. At that time, feed pumps manufactured by Halberg were of the type HD150x5 i HM200x3 was delivered to the Adamów Power Plant and the Konin Aluminum Mill was equipped with feed pumps from KSB and Halberg.

The largest Polish Bełchatów Power Plant, built in the 70s, with a capacity of 12 x 360

MW = 4320 MW has 24 pot-type feed pumps supplied by Worthington and Weir.

All other feed pumps installed in Poland are pumps manufactured in the Warsaw Pump Factory, the number of which, together with those delivered to foreign markets, exceeds 600 units.

Achievements of Wafapomp SA in the field of feed pumps.

With the development of the energy industry in the 60s, there was an intensive development of the design of centrifugal pumps intended for Polish power plants and combined heat and power plants.

The production of feed pumps at WAFAPOMP means 40 years of experience and several stages of design development.

The first Polish original development of technical documentation for a feed pump took place at the Warsaw Pump Factory in 1960. Prototype pump marked with the symbol 15WWz35, made according to this documentation, was installed in the Żerań Heat and Power Plant in 1964, where it worked until the 10s. XNUMX-stage pump 15WWz35 working at a speed of 2980 rpm, it supplied 290 m3/h of water at a pressure of 150 bar to the collector feed system of steam boilers.

The experience gained in the construction and production of multi-stage centrifugal pumps, the commissioning of the new WFP production plant in Warsaw Żerań Wschodni and the large foreign exchange expenditure incurred by the state on the import of feed pumps for the Turów, Pątnów and Adamów Power Plants contributed to the decision to purchase a license from the company Halberg for the Warsaw Pump Factory. The license authorized WFP to produce:

• 50 percent type feed pump HD150x8 for a 200 MW unit (Q = 396 m3/h, H = 2040m, n = 3920 rpm), driven by an electric motor with a power of 3150 kW via a gearbox with a torque converter,

• a set of feeding pumps for the 120 MW unit, including:

– type pre-pump HM200x3 (Q= 469 m3/h, H = 376 m, n = 2980 rpm, t = 120 C)

– main pump type HD150x5, Q = 508 m3/h, H = 1570 m, n = 4600 rpm, t = 228 C)

The first licensed sectional feed pumps were produced in 1966:

– type HD150x8 intended for El. Pątnów, 200MW unit,

– type HM200x3 i HD150x5 for El. Siersza and El. Łagisza units of 120 MW.

In later years, the Warsaw Pump Factory supplied pumps HD150x8 to the Pątnów, Rybnik, Kozienice, Dolna Odra, Łaziska Górne, Ostrołęka, Kraków Łęg Power Plants, 3 pieces for each power unit with a capacity of 200 MW, a total of over 100 pumps. Units with pumps type HM200x3 i HD150x5 were delivered to the Siersza, Łagisz, Łaziska and Siekierki Power Plants. Worn-out KSB and Halberga pumps in the Adamów, Konin and Stalowa Wola Power Plants were replaced, a total of 110 pumps. Licensed HM and HD pumps were also exported to power plants in Yugoslavia, Bulgaria and India, approximately 30 pumps in total.

As part of the police licensing proceedings in the 30s, its own technical documentation was developed and the production of a whole series of Z-type pumps was launched with capacities ranging from 500 to 3 m800/h and lifting heights from 2200 to 3000 m, at rotational speeds from 5000 to 165 rpm. These pumps are used to power steam boilers in power plants and combined heat and power plants. The permissible temperature of pumped water for pumps in the standard version is 230ºC and in the special version XNUMXºC.

Type pumps Z these are horizontal, multi-stage, centrifugal pumps with a sectional structure. The pump shaft is guided in sliding bearings circulatingly lubricated with pressurized oil. The place where the shaft passes through the stuffing boxes is sealed with a soft packing or a mechanical front seal. To balance the axial pressure acting on the rotating unit, a relief disc was used. In order to increase the certainty of movement in transient conditions, an additional double-sided, bidirectional, hydrodynamic extended bearing was used.

The series of Z-type feed pumps includes pumps:

- 15Z33, replacing, among other things, the pump HD150x8, operating parameters: Q = 400 m3/h, H = 255m. from stage, n = 3920 rpm, number of stages 5 -10,

- 15Z28 for a heating unit with a boiler (BC50, 230t/h) operating parameters: Q = 275 m3/h, H = 260m. from stage, n = 4660 rpm, number of stages 4-9,

- 6Z18 intended to power the OR 32 t/h boiler, operating parameters: Q = 40 m3/h, H = 100m. from stage, n = 5000 rpm, number of stages 6-11,

- 8Z25x12 operating parameters: Q = 80 m3/h, H = 1020m. , n = 2980 rpm, number of stages 5 – 14.

Type feed pumps 15Z33 - rys.1, in various construction versions, were installed, among others, in the Połaniec, Jaworzno, Rybnik, Konin, Poznań, Karolin, Łódź, Skawina, Żerań, Siekierki, Kraków Łęg Power Plants and the PKN Orlen Heat and Power Plants, Huta Katowice, Elany Toruń. They were also exported to Czech, Turkish, Yugoslav and Indian power plants.

Type feed pumps 15Z28 they work mainly in heat and power plants in Łódź, Gdańsk and Gdynia, Białystok, Poznań, Wrocław, Szczeciń, Bielsko Biała. Type feed pumps 6Z17 i 8Z25 are used in smaller heating plants, linen and fiberboard industries, etc.

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Construction development.

The construction of the Bełchatów power plant with power units with a capacity of 360 MW has placed new requirements on our company. Extensive experience in the design and production of centrifugal pumps for the power industry predisposed WAFAPOMP to launch the production of pot-type feed pumps. However, for the first 6 power units of the Bełchatów Power Plant, the feed pumps were purchased from Worthington.

Despite this, in the 80s, while implementing its own research and development program, WAFAPOMP developed technical documentation for a series of types of feed pumps. 20Z35, 25Z35, 30Z35 with a pot structure with a removable rotating unit, equipped with a piston disc or unloading drum and a double-sided hydrodynamic thrust bearing, with a mechanical shaft seal.

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These five-stage pumps with a pot body designed for direct welding to the discharge and suction pipelines are designed to operate with the following parameters:

– clean water with a temperature of up to 250ºC,

– nominal capacity: 800, 1250 and 2000 m3/h,

– lifting height: 3200

– max speed 5900 rpm.

Pump 20Z35x4 with parameters Q = 800 m3h, H = 2500 m, driven by an electric motor with a power of 6300 kW through a transmission with a hydrokinetic clutch, was adapted in terms of design and parameters to be replaced with the Worthington electropump in the Bełchatów Power Plant. Pump 25Z35x4 with parameters Q = 1250 m3/h, H = 2500 m, designed to be driven by a steam turbine, was adapted to be replaced with a Worthington turbopump in a 360 MW power unit. Pump 30Z35 with parameters Q = 2000 m3/h, H = 2500, driven by a steam turbine, was intended to operate in a power unit with a capacity of 500 MW.

In 1985, the design office designed a feed pump for the 1000 WWR power unit at the Żarnowiec Nuclear Power Plant. It was a two-stage type pump 40BZ25 pot construction, in a push-pull arrangement, with hydraulics from the pump 30Z35, without a piston disc, with a double-sided thrust bearing, designed to pump water at a temperature of 180ºC with a capacity of 3700 m3/h and a lifting height of 100 m.

New challenges and opportunities.

In recent years, intensive restructuring of the Polish energy sector has been carried out, including:

– replacement of worn-out devices,

– modernization of existing power units while increasing their power from 200 to 250 MW,

– construction of supercritical units with a capacity of 460 MW,

– construction of gas and steam units.

WAFAPOMP has many pumps in its production program that meet the expectations of the energy industry. In order to meet the expectations of this market sector, in 1999 the "Plan for improving the production of feed pumps" was developed and largely implemented. This plan includes activities in the field of design, technology, logistics, research, production and service. In each of these areas, actions were taken to produce feed pumps with better operational properties.

Currently, WAFAPOMP supplies sectional feed pumps guaranteeing:

• pump efficiency over 80%,
• flat efficiency characteristics enabling economical operation of pumps with capacities other than the nominal ones,
• very good dynamic condition of the pumps determined by the effective vibration speed below 2,5 mm/sec,
• good suction capacity,
• maintaining unchanged hydraulic properties such as efficiency, lifting height and efficiency over the long period of pump operation.

The pump as an element of the unit.

WAFAPOMP offers full engineering in the field of calculations and selection of accompanying devices, their mutual configuration and the implementation of a complete design of the feed pump unit. The project includes a technological diagram with I&C specifications and process interconnections, as well as an overall dimensions drawing with construction assumptions.

WAFAPOMP, in line with the customer's expectations, supplies feed pumps with full equipment for the unit, which may include:

1. variable-speed drive in one of the configurations: electric motor with gearbox and torque converter, electric motor with a frequency converter, electric motor with a thyristor cascade system, steam turbine,
2. diaphragm clutches,
3. pre-pump driven by an independent engine or the main engine,
4. integrated recirculation valve serving as a minimum flow valve and non-return flap,
5. slotted sieve at the pump suction with a differential pressure transducer,
6. shut-off fittings on the pump suction (three-eccentric M3M dampers manufactured by WAFAPOMP),
7. complete oil system with coolers, filters and instrumentation,
8. ISA nozzle with a differential pressure transducer for measuring the flow in the discharge pipeline,
9. monitoring of pump operation based on measurements of the bearing metal temperature, rotational speed, effective vibration speed, axial displacement of the rotating unit, pressure flow rate and temperatures of the feed water and lubricating oil,
10. common foundation frame for the entire unit, also with vibration isolators,
11. sound-absorbing cover of the entire unit made in accordance with applicable regulations and local conditions, including noise control measurements.

Deliveries and offers.

According to the principles presented above, new supply pumps have recently been delivered to:

1.  EC PKN ORLEN two units: feed pump HD150x5 with pre-pump HM200x3, with a torque converter, rotational speed of 4600 rpm and a 3MW engine, two more units are currently under construction,
2. PKN ORLEN OLEFIN installation: feed pump 15Z33x10 with left direction of rotation, driven by a steam turbine, the unit is adapted in terms of structure, installation and materials to work outdoors,
3. Currently, pumping units with feed pumps are manufactured 15Z33x10 VSP for EC. Siekierki and EC. Żerań, driven by an electric motor with a power of 2MW, with a torque converter and a frequency converter, respectively.

Feed pumps designed and manufactured at WAFAPOMP ensure operation after many years of operation, after inspections and renovations. By using original spare parts and acceptance tests carried out at the factory testing station, customers are guaranteed proper operation of the pump for years to come. The factory carries out major renovations combined with the modernization of feed pumps aimed at:

• matching the pump operating parameters to the installation,
• execution of stuffing box nodes with mechanical seals,
• increased efficiency and suction capacity,
• reducing the effective vibration speed,
• pump retrofitting for measurement, diagnostics,
• increasing the pump's operational availability.

The operational parameters obtained as a result of modernization are confirmed by testing at the factory test station and energy characteristics, i.e. the relationship between lifting height, power consumption, efficiency and critical anti-cavitation surplus as a function of efficiency.

Expected parameters and design features of feed pumps.

When reconstructing power units with a simultaneous increase in energy capacity from 200 MW to 250 MW, there is a tendency to replace two 50% feed pumps (Q=400m3/h, H=2050m) working in parallel with one 100% pump (Q=800m3/h, H= 2050m), with one 50% reserve pump.

For supercritical power units with a power of 460 mW with a flow boiler with a capacity of 1300 t/h, you need: 100% turbopump with a maximum capacity of 1843 m3/h at a water temperature of 185 ºC and a lifting height of 3652 m for a rotational speed of n=5952 rpm, with efficiency not less than 85,7%, 33% start-reserve feed pump with parameters Q = 600m3/h, t = 185 ºC, H = 3514m, n = 5800 rpm, with efficiency not less than 82,6%.

In the gas and steam unit with a total power of 240MW (including the power of the steam turbine 60MW), there are two feed pumps, high-pressure and low-pressure, feeding water to two drums of the recovery boiler. These are member pumps with a speed of 3000 rpm, with parameters corresponding to the pumps produced so far. Z or type pump WN in cast steel version.

 To sum up, it can be said that the development of centrifugal pumps, including feed pumps, on the Polish market is subject to certain global trends. These are:

• increase in lifting height from one stage by increasing the rotational speed,
• increasing the efficiency of pump units,
• lowering the required value of the anti-cavitation surplus,
• increasing reliability by ensuring an appropriately low level of vibrations,
• reducing the level of emitted noise,
• placing the units on a common foundation frame.

MSc. Andrzej Wesołowski

Prof. Stanisław Jaźwiński

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 Author's comment after many years:

GPW SA continues the good tradition of producing high-pressure pumps feeding steam power boilers. In the last few years, until 2015, we have produced over 20 new units with 15Z type feed pumps. We delivered these pumps to new heat and power plants in Częstochowa, Stalowa Wola, Zofiówka, Tychy, Szczecin and Bielsko-Biała. We delivered 15Z33 pumps in modernized designs to PKN Orlen in Plock and to the Żerań Power Plant in Warsaw.

We meet the demands and expectations of users in terms of parameters and design features of feed pumps, which I wrote about in the article.

Construction and development works are carried out on Z-type pumps in order to meet the current technological requirements in power plants and combined heat and power plants under construction or modernization. We have designed two new feed pumps: a 15Z40 type pump, the so-called a 100% pump for the 200 and 250 MW units and a small 80YSW feed pump intended for steam and gas units. We have improved the anti-cavitation capabilities of type 15Z pumps by using new designs and technologies of the 1st stage rotors. We have introduced design solutions that guarantee the operation of feed pumps with reduced vibration and noise levels. We have an alternative design solution of the bearing assembly for 15Z pumps without a pressurized oil system. We analyzed the structure and the possibility of producing 25Z35Ax4 pot-type feed pumps for the retrofit of 360 MW units.

We provide comprehensive services in the field of equipment and construction of pumping stations with feed pumps, including design, construction and completion works in the construction, mechanical and electrical industries, including supervision and commissioning.

 MSc. Andrzej Wesołowski

Entry.

The article shows, using the example of one contract, how much the customer's requirements for pump manufacturers have changed in a relatively short time and what technical, organizational and logistical problems this creates.

Contract.

In February 2002, WAFAPOMP SA received an invitation from ALSTOM Power to submit an offer for the supply of two new or renovation combined with modernization of the existing main cooling water pumps for the 460 MW power unit of the modernized Pątnów II power plant. This unit is to replace the existing two power units No. 7 and 8 with a capacity of 200 MW each. It will use the existing cooling system.

The submitted offer turned out to be the most attractive and WAFAPOMP SA won the tender. The client decided to renovate and modernize the 30P180 pumps that had been in use for 19 years. This decision is justified both technically and economically, because the user will receive a modernized pump with very good operational values ​​for a price much lower than the price of a new pump.

Description of the 180P19 pump.

Propeller pumps installed at the Pątnów power plant 180P19 produced at the Warsaw Pump Factory in 1972. They were intended to work with the following parameters:
– nominal capacity Q = 29000 m3/h,
– lifting height H = 10 m.
The kinematic speed factor is 190, the rotor diameter is 1400 mm, the discharge port diameter is 1800 mm. The weight of the complete pump unit is 62 t and its length is 15,5 m. Asynchronous electric motors with a power of 1250 kW and a rotational speed of n = 370 min-1 were used to drive the pumps. The dimensions of the pump and the levels of the ceilings on which it is supported in the Pątnów power plant are presented figure 1.

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There is an inlet port located in the ceiling of the chamber. In the intermediate ceiling, a ceiling ring was concreted, and an outlet elbow was placed on it. The engine base, on which the drive engine is mounted, is located on the upper ceiling. Water is supplied to the pump inlet port through a suction chamber made of concrete. Water is discharged from the pump through the discharge port of the outlet elbow. The pump shafts are guided in rubber bushings, lubricated with clean water supplied to each of them through conduits. The tightness of the shaft at the exit from the elbow cover is ensured by a stuffing box with a rope packing. The longitudinal loads resulting from the hydraulic pressure and the mass forces of the pump rotating unit are carried by a Michell-type plain bearing. This bearing is lubricated with water-cooled oil.

The design of the pump allows disassembly of the internal assembly without the need to dismantle its casing, i.e. the discharge pipes and the outlet elbow.

Pumps 180P19 are equipped with a mechanism for regulating parameters during operation by changing the angle of the rotor blades. The rotor blade is rotatably supported in two bronze bearings mounted in the rotor hub. The angle is changed using a system of two levers connected together.

Pump elements 180P19 are made of materials that guarantee durability and reliability in operation (e.g. rotor blades and rotor chamber - made of alloy cast steel).

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Requirements for modernized pumps.

Pumps must meet the requirements specified in the contract:
– capacity Q = 28050 m3/h for three different lifting heights, depending on the water level in the suction chamber and the characteristics of the pipeline

H = 9,5 m, H = 11,4 m, H = 7,7-m,

– minimum guaranteed efficiency

– parameters are adjusted when the pump is stopped by changing the angle of the rotor blades,

– pump bearing durability not lower than 40000 hours,

– increased durability of the choking knot,

– noise level of the pump unit max 85 dBA,

– adapting the pump structure to start with reverse water flow,

– guaranteed possibility of overloading the motor by 40% when starting the pump,

– the first critical pump speed is 25% higher than the pump rotational speed,

– equipping the pump unit with control and measurement equipment that monitors the parameters and dynamic condition of the pump,

– durability of anti-corrosion protection (paint coatings) min. 5 years,

– expected operating time of the pumps after renovation is not less than 35 years.

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Calculation requirements for technical documentation.

WAFAPOMP SA, in addition to preparing typical construction and technological documentation resulting from the scope of modernization, is obliged to provide the following documents:

1. detailed pump and motor data sheets,
2. pump operating characteristics H = f (Q), P = f (Q), M = f (Q), 7 = f (Q), NPSH = f (Q) in the capacity range 0-120% Qzn,
3. characteristics of the resistive torque and pump head as a function of positive and negative (reverse) flow through the pump,
4. static and dynamic loads on the foundation,
5. permissible loads on the discharge port,
6. technological diagram within the scope of delivery of the unit,
7. assumptions for the control and protection system of pumps and motors,
8. inspection and test plan,
9. procedures for filling the cooling water system using modernized 180P19 pumps,
10. 10. torque and starting current characteristics for the drive motor, M = f (n) and I = f (n) for U = 70%, 80%, 90% and 100% of the rated voltage.

Description of the cooling water installation.

To cool the 460 MW unit at the Pątnów II power plant, cooling water is taken from the lake and delivered through existing concrete channels to the pump suction chambers. In front of the suction chambers, grates and rotating cleaning sieves as well as devices for controlling the water level are installed. Two 180P19 pumps will pump water to two independent halves of the turbine condenser through individual DN 1800/2000 pipelines, 230 m long each. Water is also discharged from the condenser through individual DN 2000 pipelines, 75 m long each, to discharge wells. The ends of the discharge pipelines are permanently immersed below the water table.

The system is typically a lever system and to empty it of airbags, vacuum pumps will be installed, sucking air from the highest spaces of the system. The highest point of the siphon system are the water chambers of the main condenser, the upper edge of which is at + 0,4 m. For a low water level in the suction chamber (ordinate 8,5 m) and for a high water level in the discharge chamber (ordinate 7,4, 1,1 m), with the installation filled with water, the geometric lifting height is XNUMX m.

Fine filters will be installed on the water supply pipelines, just before the condenser. In the pressure pipelines, directly behind the pumps, instead of the existing truck check valves, it is planned to install hydraulically controlled stop-return valves with controlled closing time. The operating characteristics of these valves significantly affect the pump starting conditions and engine load. The non-return valve will be opened by a hydraulic actuator, and not automatically by the flow of water. Turning on the pump 180P19 will occur after the stop-and-return valve is fully opened, which means the pump will start with reverse water flow. This makes it necessary to protect the pump against reverse rotation and to properly select the engine torque, which is greater than the pump resistance torque, which will occur starting from negative flows.

Scope of design changes in modernized pumps.

The requirements for the renovated 180P19 pumps require the introduction of a number of new solutions or improvements to the design of its components.

1. The use of two-way sliding plates in thrust bearing,

2. Equipping the pump with a mechanism that protects against reverse rotation and balances the torque that occurs in the event of negative water flow,

3. Increasing the durability of the pump's transverse plain bearings by redesigning the bushings and using new elastomers,

4. Changing the design of the stuffing box to enable water to be supplied to it before the pump is started and during its operation,

5. Application of a new mechanism for regulating the pump operating parameters at standstill. The position of the mechanism lever in the rotor hub will also change. This will directly increase the operational reliability of the mechanism for setting the rotor top angle,

6. Introducing changes to the rotor hub and blade shells to ensure tightness and prevent water from entering the hub,

7. Introduction of material changes aimed at increasing reliability and durability, especially the adjustment mechanism,

8. Equipping the pump unit with control and measurement equipment:

– oil level and temperature sensors in the thrust bearing,

– sliding plate temperature sensors,

– measurement of rotational speed and direction of rotation,

– bearing vibration monitoring system.

Troubleshooting.

After WAFAPOMP SA accepted the terms of the contract, implementation dates and persons responsible for carrying out specific works relating to the technical documentation to be delivered to the client first were set. The scope of modernization works was determined. An analysis of the pump's structure was carried out, and on its basis, specific design changes were planned. The pump operating characteristics, resistance torque diagram, and overall dimensions drawing were developed. A preliminary design of the brake (one-way clutch) was made. Hydraulic and strength calculations were carried out.

A program of trials and tests was developed, in which the emphasis was placed on the control of those pump elements that have the greatest impact on the operating parameters, in particular on efficiency and reliability, including primarily:

– the shape of the blade blade to be consistent with the design dimensions,

– blade angles in the rotor palisade – all blades must have the same angle,

– gap (clearance) between the outer diameter of the blades and the rotor chamber; the volumetric efficiency of the pump depends on its size.

A procedure for filling the cooling system using modernized 180P19 pumps was developed. It describes all the activities that must be performed from the moment the pump is started until the system is filled with water.

When filling the system, the pump operates in extremely unfavorable conditions. When started, the pumping resistance is very small, so the pump operates at very high efficiency. Then the efficiency decreases as the pumping resistance increases, reaching its maximum when the capacitor is filled. The lifting height of the pump will then be approximately 17 m, and the engine will be loaded with power of over 1500 kW; motor overload = 40%.

When filling the cooling system, the pump will cross the unstable operating area twice in the so-called "saddle".

Conducting an analysis of the pump's operation 180P19 in transient states, i.e. for starting with reverse water flow, turned out to be a very difficult task that we have not encountered before. Therefore, we turned to the Warsaw University of Technology for help in solving this problem. We were provided with substantive support by the Department of Pumps, Drives and Power Plants headed by Professor Waldemar Jędral.

A preliminary verification of the technical condition of the pump components was carried out. Parts that were unusable due to the introduced design and material changes were eliminated. The remaining pump components will be blast-cleaned and then subjected to precise measurements. Parts whose technical condition raises concerns will be replaced with new ones, and the remaining parts will be reinstalled in the pumps after regeneration. The scope of work is very extensive, and the deadline for delivery of two modernized pump units is: 180P19 expires in December 2002.

End.

The detailed conditions for the manufacturer presented in the article illustrate how demanding the customer is at the moment and how difficult and unusual tasks must be undertaken in order to obtain an order.

WAFAPOMP SA will meet all contract requirements. Pumps leaving the factory will be high-quality products, but it has long been noticed that in large pumps with capacities Q > 25000 m³/h, designed on the basis of the results obtained from tests of model pumps, there are discrepancies between the calculated parameters and those obtained during tests of the working pump. Operating conditions and scale effects have a significant impact on the characteristics. Deviations from the laws of similarity at the pump inlet play a particularly important role. The influence of the inlet shape is greater the greater the pump speed, so this problem largely concerns propeller pumps. Disturbances in the pump inlet area may also occur as a result of incorrect shapes and cross-sections of the inlet channels in the pumping station.

Inlet channels supplying water in the Pątnów II Power Plant to the pump 180P19 Unfortunately, they do not have favorable shapes, which was discovered during the on-site inspection. They are characterized by several changes in flow directions and (perpendicular to each other) step changes in cross-sections and, consequently, in speed. The highest speed = 1,2 m/s occurs at the point of entry to the rotary sieves and exceeds twice the recommendations (c = 0,3 - 0,6 m/s). The factors described may affect the pump's operating parameters.

MSc. Andrzej Wesołowski

Eng. Lucjan Urbański

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Author's comment after many years:

In 2002, we received an order from ALSTOM Power for the renovation and modernization of 2 180P19 pumps for a 460 MW power unit at EL. Patnów II. We then offered to install a mechanism for adjusting the angle of the rotor blades while the pump was running. However, ALSTOM decided that such regulation is not necessary, because the pumps will operate with a constant load and "while standing" regulation is sufficient. We then modified the design of the entire pump, including the lever system, blade journal bearings and the stainless steel adjustment mechanism in the rotor hub.

Over 10 years of failure-free operation of the modernized 180P19 pumps in the 460MW unit confirms the correctness of the adopted solutions.

Currently, for type 180P19 pumps, we offer a mechanical-electric system for regulating the angle of the rotor blades during operation and at standstill. The solution is a combination of proven solutions used in 180P19 pumps operating at EL.Pątnów II and a tested solution for the cooling water pump for EL. Broom. The proposed mechanism for adjusting the angle of the rotor blades during the movement of the 180P19 pump is equipped with an intelligent, reliable electromechanical actuator with positioning.

Advantages of our new regulation system for 180P19 pumps

1. A simple and durable mechanical system for converting the rotational movement of the electromechanical actuator into the sliding movement of the control rod.

2. High load capacity of the bearings used, durability 100 hours.

3. Oil lubrication of the mechanism.

4. High stiffness of the mechanism body.

5. Optimal selection of construction materials and high accuracy of machining of mechanism elements on numerically controlled machines

6. Possibility of installing the regulation system in already manufactured 180P19 propeller pumps with a small scope of adaptation works.

7 . There is no need to modify the drive engine, including drilling the engine shaft. Standard motors can be used.

9. Possibility to control a 4-20mA or digital signal

10. Possibility to adjust the rotation speed of the rotor blades.

11. Failure of the electromechanical actuator or loss of power supply does not limit the operation of the regulated pump because the mechanism is self-locking, manual regulation is also possible without stopping the pump.

12. GPW SA, as a recognized manufacturer of propeller and diagonal pumps, guarantees professional selection of the regulating mechanism and comprehensive service of these pumps.

MSc. Andrzej Wesołowski

1. Introduction.

There is a common opinion among pump users that the main advantage of free-flow pumps is the large gap between the impeller and the casing cover wall, which allows the passage of "thick" solids contained in the pumped liquid.

The relationship between the pump capacity and the size of the "free clearance" is very favorable in the case of free-flow pumps, and solids of a specific size can be pumped with relatively small capacities.

Potential users take into account the clearly lower efficiency of free-flow pumps compared to centrifugal pumps, usually with small numbers of blades, and this significantly influences their decisions.

However, situations often arise when the use of free-flow pumps is justified even when there are no "coarse" grains in the pumped mixture.

2. Free flow pump operation.

Free-flow pumps differ greatly from conventional centrifugal pumps in terms of the shape of the flow part and the hydrodynamic phenomena occurring during operation. Research conducted by various authors [e.g.1,2,3] showed that the liquid stream entering the pump flows through an open impeller (with curved or, less often, radial blades). However, since the flow rate through the impeller (impeller efficiency) is much higher than the pump efficiency, a circulating stream is created, characteristic of free-flow pumps, which circulates through the inter-blade channels of the impeller and the bladeless (free) space of the casing, as illustrated in Figure 1. liquids flow into the inter-blade channels of the impeller over its entire front surface [3], and in [1,3] it was shown that the intensity of the circulating stream is (at optimal pump efficiency) 2-3 times higher than the pump efficiency, which should be seen as the main reason low efficiency of free-flow pumps.

Near the external diameter of the rotor, the streams are separated - transit and circulating, with the transit stream heading to the pump's collecting channel, and the circulating stream flowing in the centripetal direction, rotating intensively at the same time, and the peripheral component of its speed is not much different from the peripheral speed of the rotor blades at a given location. radius, and near the inlet area (defined by the diameter of the inlet stub) it is even greater [1,3]. Near the inlet area, part of the circulating stream is mixed (mixed) with the liquid stream flowing into the pump (transit). When both streams mix, momentum is exchanged between them and, as a result, a pre-curve of the liquid flowing into the inter-blade channels is created. Pre-turbulence may even appear in the inlet pipe, even though it is far from the impeller.

The presence of solids significantly complicates the already very complex hydrodynamic phenomena occurring during pump operation.

Within the inter-blade channels of the rotor, the solid body is subjected to the centrifugal force (usually 200-300 times greater than the force of gravity) and the Coriolis force (much smaller, approximately 50-100 times greater than the force of gravity), which are shown in Figure 2. They are defined as follows : :

                             F_od = mω²r ( 1– ρ_w/ρ_s) ( 1 )

                             F_C = m2ωw ( 1– ρ_w/ρ_s) ( 2 )

and their ratio is:

                F_od /F_C = (ωr) / (2w ).

In formulas (1) and (2): m – is the mass of the particle, ω – is the angular speed of rotation of the rotor, w – is the relative speed of the particle in relation to the rotor, r – is the radius defining the position of the particle, ρ_s and ρ_w are the densities of the solid and water, and the term (1– ρ_w/ρ_s) takes into account the influence of buoyancy (Archimedean).

Within the free flow space (in which the rotating liquid heads towards the pump axis, but also successively flows into the impeller channels), the centrifugal force also acts on the solid. The impact of these forces on solid bodies causes their motion trajectories to differ from the motion trajectories of liquid particles.

Finally, due to a rather abrupt change in the flow direction of the liquid stream entering the rotor from axial to radial, solids will be "rejected" towards the rotor disc.

The magnitude of the forces acting on solid bodies is also influenced by their density (because centrifugal and Coriolis forces are proportional to the density difference of the solid body ρ_s and liquid ρ_c ) as well as their size, because the resistance of the liquid to the grain moving in it is relatively (in relation to the weight of the grain), the greater the smaller the grain.

It is also worth noting that while "fine" bodies flow through the inter-blade channels of the rotor, at least some of the "coarse" bodies, as a result of the initial swirl of the liquid in the inlet area and the intense swirling of the liquid in the bladeless space, are directed through the bladeless space under the influence of centrifugal force. to the pump collecting channel, bypassing the impeller.

The above-mentioned phenomena undoubtedly influence the operating parameters of the free-flow pump, and the assessment of this influence is basically only possible experimentally.

One of the authors has been conducting research for several years on the influence of the solid phase content in fine-grained mixtures and suspensions on the operating parameters of a free-flow pump, and the results of these studies constitute an extensive set of information. Their development and analysis allowed for the formulation of interesting theses and conclusions.

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3. Operating parameters of a free-flow pump pumping a mixture of solids in water.

Extensive research has been carried out [e.g. 4, 5] on a free-flow pump with an impeller located in a free flow space, the flow system of which is shown (with proportions) schematically in Figure 3. The main geometric features of the pump and their characteristic dimensionless relations are as follows:

d₂ = 0,190 m, b₂ = 0,023 m, b_k = d_t = 0,065 m, d_s = 0,080 m, b₂/d₂ = 0,121 ; b_k/d₂ = 0,342 ; d_s/d₂ = 0,42. Number of radial rotor blades z = 10.

The pump tests were carried out at a rotational speed of n = 1460 rpm. Pump parameters when pumping water at the selected capacity Q = 0,01225 m³/s (≈12 l/s) - close to optimal efficiency - were as follows: lifting height H = 13,4 m, shaft power P = 2,82 kW, efficiency η = 0,57. Kinematic speed factor n_sQ = 23,1 ; and the dimensionless factor of the lifting height is ψ = 2gH/(u₂)² = 1,25.

Really pumped mixtures of fine-grained bodies or suspensions usually contain solids with dusty granulation (less than 0,1 mm) or fine-grained (less than 1 mm), so such solids were used during the tests. The research whose results will be presented used solids with the following characteristics:

• ground carbon ρ_s = 1441 kg / m³ , δ₅₀ = 0,19mm,
• fine sand ρ_s = 2553 kg / m³ , δ₅₀ = 0,37mm,
• fly ash ρ_s = 1930 kg / m³ , δ₅₀ = 0,071mm,
• magnetite dust ρ_s = 3618 kg / m³ , δ₅₀ = 0,042mm,

(with δ₅₀ means the diameter of grains with a mass fraction of 50%.

Pump tests were programmed and carried out in conditions of pumping various (specially prepared for this purpose) mixtures in which the volume concentration of the solid phase (volume fraction) c_v increased every 0,05 up to the maximum value c_max, different for each pumped mixture. In the case of ground coal and fly ash c_max = 0,45, while in the case of sand and magnetite dust c was achieved_max 0,25 and 0,30 respectively. Even though the pump operated with a geometric inflow (at a level of approximately 1 - 1,3 m), at values ​​c_v > c_max carrying out measurements became risky due to the blockage of the short pipe (Ф 80 mm) connecting the mixture tank with the pump inlet, even though there was a mixer in the tank to agitate the mixture.

In the case of suspensions of fly ash and magnetite dust in water (quasi-homogeneous liquids), their rheological characteristics were determined. It was found that when c_v > 0,15 – 0,18 then they appear in suspensions and as c increases_v the features of a plastically viscous body (Bingham) become more intense.

To illustrate the thickening of the mixture as the volume fraction of the solid phase increases (c_v), the next figure 4 shows ash-water suspensions with an already sedimented ash bed, which was originally dispersed throughout the volume. As you can see, with larger proportions of solids ( c_v > 0,30), the amount of overlying water is small or even negligible.

After measuring the pump parameters, its characteristics of lifting height H = f (Q), shaft power P = f (Q) and efficiency η= f (Q) were determined, taking into account the actual densities of mixtures or suspensions in the calculations.

In the case of all mixtures, it was found - with water as a comparative factor - that as the share of the solid phase increased (c_v) flow characteristics H = f ( Q ​​) shift towards lower values, and shaft power characteristics P = f ( Q ​​) shift towards higher values. However, the efficiency characteristics η = f (Q ) as c increases_v initially move towards higher efficiency values, and after reaching the highest position, they move towards lower efficiency values, and with larger shares of c_v reach positions below the characteristics for water.

For example, Figures 5, 6 and 7 show the characteristics of a pump pumping ash-water suspensions. In the case of other mixtures, the changes in characteristics were of a similar nature. Maximum efficiency was achieved basically regardless of the volume fraction of solids (c_v ) and their density (ρ_s ) with practically the same pump capacity Q ≈ 0,01225 m³/ s.

In order to synthetically present the influence of the share of the solid phase in individual suspensions on the operating parameters of the pump, Figures 8, 9 and 10 present changes in the operating parameters H, P and η depending on the share of the solid phase c_v, with the same efficiency Q = 0,01225 m³/ s.

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Analyzing these parameters, you can notice that:

● as share increases c_v solid phase, the useful lifting height H decreased (and more and more quickly), and the decrease in lifting height is greater the higher the density of the solid phase, and the effect of grain size is ambiguous,

● with increasing share c_v solid phase, the power P on the pump shaft increased (approximately linearly) - throughout the entire range of changes in the volume fraction c_v, however, in the case of fly ash (with dust granulation), it can be seen that the shaft power increased faster when_v > 0,3, when the features of a non-Newtonian (Bingham) fluid intensified in the suspension,

● pump efficiency η initially increased and reached its maximum value at volume fraction c_v ≈ 0,1 in the case of sand, – with c_v ≈ 0,2 in the case of magnetite dust, – with the participation of c_v ≈ 0,25 in the case of ground coal, – with c_v ≈ 0,3 in the case of fly ash, and then decreased rapidly,

● maximum efficiency η_Max reached a level of approximately 0,60 - 0,61 in the case of dusty bodies (fly ash and magnetite dust), and slightly lower values ​​of 0,59 in the case of fine-grained bodies (ground coal and sand), while in the case of water pumping they were achieved (with comparable efficiency) efficiency 0,57.

A similar nature of changes is also observed at other capacities, significantly lower than the nominal capacity.

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4. Discussion of the obtained measurement results.

In order to generalize the obtained results to some extent, the following dimensionless discriminants were introduced:

          

where the subscripts (m, w) denote the mixture and water, respectively.

These discriminants are determined with the same pump capacity (Q_m = Q_w ) pumping the mixture or water.

Distinguishing features k_H   and k_η determine changes in the useful lifting height or efficiency of the pump pumping the mixture or suspension in relation to the parameters obtained when pumping water. However, the distinguishing feature k_P   determines the ratio of energy supplied to the pump per unit mass of the pumped medium, in the case of pumping a mixture and water.

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Otherwise, writing k_P , you will receive

 

Distinguishing features k_ηk_H first_P binds dependency

                                                                     

Graphical relationships of the discriminants k_Hk_η first_P on volume fraction c_v solid phase in mixtures (calculated for efficiency close to optimal Q ≈ 0,0125 m³/s ), shown in Figures 11, 12 and 13.

Analyzing these graphical relationships, it is easy to see that:

● the useful head of the pump decreases as the proportion of solid phase increases c_v in the mixture, and the drop in lifting height increases as the density of the solid phase increases, but the effect of grain size is not clear,

● pump efficiency increases as c_v initially it increases noticeably, then decreases and only at the highest values ​​of c_v is lower than the efficiency achieved when pumping water,

● power on the pump shaft as c increases_v increases slower than would result from the increasing density of the mixture.

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Therefore, changes in the parameters of a free-flow pump differ from changes in the parameters of a centrifugal pump with similar parameters, operating in similar conditions.

The useful unit work of a free-flow pump decreases with increasing volume fraction c_v solid phase in the mixture, and this effect is clearly greater as the density of solids increases. In the c range_v < 0,3 – 0,4 (depending on the density of the solid phase) decreasing H (or k_H ), however, is not caused by an increase in hydraulic losses in the pump, as it is not accompanied by a decrease in pump efficiency, and the pump efficiency in this range c_v it even increases slightly. It can be hypothesized that the reduction in the pump lifting height occurs as a result of the increase in the initial swirl of the stream flowing into the pump. The exchange of the amount of motion that occurs when the circulating stream (which is characterized by a significant peripheral component of velocity) mixes with the stream of the mixture flowing to the pump is more effective in the case of a mixture of dusty and fine-grained solids with water, compared to the mixing of water streams during water pumping. This hypothesis is based on the results of research on the efficiency of the exchange of the amount of motion between solid phase particles and gas, cited in [6].

However, when, as a result of the increase in the share of the solid phase (when c_v > 0,3), the conditions for the exchange of the amount of motion between the mixing streams deteriorate, and moreover, when the non-Newtonian properties of the mixture (plastic-viscous body) increase, this causes an increase in hydraulic losses in the pump, which causes an increasingly rapid decrease in the pump lifting height.

Other experimental tests have shown that when a free-flow pump pumped oil with increasing viscosity, the coefficient k_P increased, and the coefficients k_H first_η decreased with increasing oil viscosity. Therefore, an increase in the viscosity of the pumped medium always causes deterioration of the pump's operating parameters.

In the case of pumping mixtures, when the volume fraction of the solid phase c_v < 0,3 – 0,4, it is concluded that k_P < 1 and at the same time k_P < k_H. It can be concluded that the hydraulic losses in the pump, caused by the presence of solids, are reduced, because due to the centrifugal force, the solids flowing through the pump impeller are mostly directed to the pump collecting channel, and the circulating stream is characterized by a slightly reduced share of solids, is therefore "diluted" in relation to the transit stream of the mixture. Since it generates the dominant part of the hydraulic losses in the pump [1,3], even a very slight reduction in its density affects the size of these losses and, as a result, reduces the power demand and the achieved efficiency. This is presented illustratively in Figure 14. This hypothesis was confirmed by research on the mixture density in the chamber of a bladeless pump, consisting in the analysis of the density of mixture samples taken from the bladeless chamber [7].

They show that in the area of ​​the bladeless pump space, the volume fraction of solids in the mixture is slightly lower (on average by ∆c_v ≈ 0,01 – 0,03) than in the pump discharge port.

Occasional measurements were also carried out under conditions of pumping coarser grains (coarse sand, δ₅₀ ≈ 0,9 mm) and no increase in pump efficiency was observed, but efficiency drops were small.

5. Suction capacity of free flow pumps.

It is known [8, 9] that free-flow pumps are characterized by very good suction properties, which under certain conditions may determine the possibility of uninterrupted operation of the pump.

To confirm the good suction properties of the pump used in the tests, limited measurements of its suction characteristics were carried out. Figure 15 shows the suction characteristics H = f (p_s ) determined at capacities Q = 0,0089 and 0,01225 m³/s, using water as the working fluid.

At both capacities, the suction characteristics H = f (see_s ) decrease slowly, and a sudden breakdown of the characteristics occurs at pressures (absolute) p_s < 9 or 17 kPa. The energy surpluses in the pump inlet port corresponding to these pressures were approximately 1,20 m and 2,15 m, respectively, which confirms the very good suction capacity of the tested pump.

Unfortunately, measurements of suction characteristics using suspensions have not been performed. However, it can be expected that in the case of pumping suspensions, especially those with reasonable densities, the necessary energy surpluses in the pump inlet port will not be much different from the energy surpluses in the case of pumping water. Fine solid particles in suspension will, to some extent, "suppress" the development of cavitation.

Excellent suction properties are an important feature of free-flow pumps, thanks to which in some situations the use of a free-flow pump can solve potential problems.

6. Final remarks.

The beneficial effect of the presence of a fine-grained solid phase on the operating parameters of a free-flow pump presented in the publication is a little-known effect and is not usually taken into account. In repeated measurements using various solids, it was found that the presence of dusty and fine-grained solids (less than 0,5 mm) in mixtures and suspensions (even with their significant volume fraction) causes a slight increase in pump efficiency (up to 3 points). percentages) compared to the efficiency achieved when pumping water. This feature, although very advantageous, is not important enough to recommend the use of free-flow pumps in every situation when it is necessary to pump suspensions and fine-grained mixtures. However, in some situations it is justified.

In cases where "coarse" bodies may even occasionally be found in fine-grained mixtures, a free-flow pump will allow them to be pumped without fear of them "blocking" in the pump. The use of centrifugal pumps in such cases - even with small numbers of blades - often involves the need to accept an increase in efficiency.

In situations where the pump is to pump dense suspensions or fine-grained mixtures, using a free-flow pump can avoid problems that may be caused by the limited suction capacity of centrifugal pumps.

The use of free-flow pumps should be considered when there is a need to desilt or clean various types of sumps and settling tanks, as well as tanks and trenches with layers of silt at the bottom. Then, the very good suction capacity of free-flow pumps may determine the success of the project.

It is also worth taking into account that the deterioration of pump parameters caused by erosive wear of the impeller will become visible - compared to centrifugal pumps - after a much longer time. It is also easy to make the impeller of a free-flow pump from materials that are highly resistant to erosion abrasion.

From many reports it can be concluded that free-flow pumps are often used and fulfill their tasks.

Dr. Eng. Jerzy Rokita

MSc. Zbigniew Krawczyk

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Literatura:

1. Grabow G.: Untersuchung der Energieübertragung das Fördermedium im Arbeitsraum von Freistrumpumpen mit Hilfe von Geschwindigkeits- und Druckverteilungsmessungen, Maschinenbautechnik, 2, ( 1970).

2. Schivley GP, Dussourd JL: A analytical and experimental study of a vortex pump, Journal of Basic Engineering, (1970), 12.

3. Błaszczyk A. et al.: New design of a free-flow pump, Pompy Pompownia, No. 5 (43), 1966.

4. Rokita J.: The influence of volume concentration of fly ash in water on the operating parameters of a free-flow pump, Works of the Institute of Fluid-Flow Machinery of the Polish Academy of Sciences, Issue 83-84, Gdańsk, 1984.

5. Bracha Z., Kowalski J.: Diploma thesis prepared at the Institute of Energy Machines and Devices of the Silesian University of Technology in Gliwice under the supervision of J. Rokita, Gliwice, 1982.

6. Soo SL: Fluiddynamics of multiphase systems, Bleisdell Publishing Company, Waltham, Massachussets, 1968.

7. Tudaj J.: Diploma thesis prepared at the Institute of Energy Machines and Devices of the Silesian University of Technology in Gliwice under the supervision of J. Rokita, Gliwice, 1982.

8. Rütschi K.: Die Arbeitsweise von Freistimpumpen, Schweizerische Bauzeitung, 32, ( 1968).

9. Łazarkiewicz Sz., Troskolański AT, Centrifugal pumps, WNT, 1973.