Monthly: May

The Polish hard coal mining industry is in a difficult economic situation. In order to avoid losses, the management boards of mining companies are looking for ways to reduce operating costs. In this respect, the costs of renovation of machines and equipment operating in mines constitute an important item. Due to the above-mentioned difficult economic situation, purchases of new devices are limited, which necessitates the renovation of existing equipment.

The problem is important due to the difficult operating conditions in mines, as a result of which the frequency and scope of renovations are much greater compared to other types of industry. Additionally, the aspect of safety comes into play - machines operating underground in mines are not general-purpose machines, but must meet specific requirements related to, among others, the issue of work safety in an atmosphere at risk of methane or coal dust explosion. For this reason, mining machines are constructed according to special requirements and are subject to a special attestation procedure.

For the above reasons, the regulations governing the principles of repairs of machines and equipment operating in underground mining plants in force in recent years were strict. These regulations were questioned on the grounds that they limited market access for entities other than original machine manufacturers and created a risk of overpricing repair services. For this reason, these regulations have been liberalized. The Supreme Audit Office's report published a few months ago was devoted to this issue and was widely discussed in the media. Comments devoted to the report focused on the media-interesting issue of alleged lobbying by mining machinery manufacturers aimed at monopolizing the renovation market, and the liberalization of regulations was presented in these comments as a healthy tendency to open this market. In reality, the issue is much more complex and the regulations governing the manner of carrying out repairs of mining machines should be looked at not only from one point of view. When discussing the Supreme Audit Office's report, emphasis was placed on the examples cited in it of overpricing repair services by machine manufacturers taking advantage of their privileged position.

However, no attention was paid to the statement also included in the Supreme Audit Office's report that the mere reduction of prices of renovation services may not be beneficial to the economic interests of mining companies in the long run if the quality of these services is not maintained at the same time. The production and repair of mining machines of appropriate quality requires the use of appropriate technologies and expensive equipment. Garage-type companies offering renovation services do not have to include the costs of this equipment in the prices of their services, and as a result, they are able to perform renovations cheaper. In the long run, the consequences of using such services can be costly for mining companies. The costs of downtime and suspension of mining due to equipment failure may be many times higher than the costs of renovation services. The same applies to energy consumption. The devices that consume the most energy include main drainage pumps that pump water from mine undergrounds to the surface. It can be concluded that the cost of additional energy consumed by pumps as a result of improper renovation is many times higher than the cost of the renovation service itself. The benefits of reducing the prices of renovation services will only be real if the price reduction is not accompanied by a reduction in the quality of services. The NIK report points out that specifying the required quality standards when ordering renovation services and enforcing them from contractors leaves much to be desired in the Polish mining industry.

An obvious aspect is the issue of occupational safety. Polish mining boasts a system of attestation and certification of machines and equipment intended for operation in mine undergrounds, thanks to which it is one of the safest in the world, and the tragic indicator showing the number of fatalities per million tons of extracted coal is significantly lower compared to some other countries. This is a joint achievement of the mining industry itself, its scientific base and mining machinery manufacturers. Allowing companies to carry out overhauls of machines that have undergone scrupulous safety certification before putting them into service, for which the basic criterion of operation is the low price of overhaul services, creates a risk of a gap in the safety assessment system. Questions about whether machines operating underground in mines have been renovated in a way that ensures the level of safety of a new machine delivered by the manufacturer cannot be asked only during investigations aimed at explaining the causes of tragedies that cost many lives.

A less frequently noticed aspect of this case is the issue of copyright to the documentation of mining machines. These are machines produced for a niche market, sold in relatively small quantities, and at the same time, due to difficult working conditions and strict safety requirements, requiring significant expenditure on design and obtaining the required certificates. It is common practice among global manufacturers to include development costs not only in the price of a new product, but also in the costs of spare parts and renovations, so that the price of the new product is not excessive and at the same time the manufacturer can afford to invest in further development. Allowing a situation in which profits from renovations are primarily made by companies that do not incur expenditure on the development of safe mining machines, their testing and safety certification, is in fact promoting unfair competition. In the long term, this may mean that Polish producers will no longer be profitable to invest in the further development of mining machines.

Dr. Eng. Grzegorz Pakula

---

The article was published in 2010 on the wnp economic portal - www.wnp.pl

 

 

The experience of the last dozen or so years shows that the risk of flooding in our country is constant, and that subsequent floods on a local scale occur every year, and disasters on a national scale occur every few years.

Climate changes associated with the greenhouse effect contribute to an increase in the frequency of intense rainfall, as a result of which floods are becoming more frequent.

The flood that occurred in 2010 showed that despite the dedicated involvement of both rescue services and civilians in combating its effects, our country is systemically poorly prepared for floods. One manifestation of this fact is the lack of appropriate pumps for flood prevention operations. It should be noted that flood prevention exceeds human technical capabilities, as it is not possible to build and maintain a protection system that would be able to protect every place against every amount of water carried by rivers. Retention reservoirs, embankments, etc. are prepared for some statistically determined increased rainfall.

However, statistics has it that randomly there are rainfalls that exceed even the expected maximum. In such cases, protection systems turn out to be insufficient and we encounter phenomena such as overflow of retention reservoirs or ruptures of embankments. When a embankment break occurs, the amount of water flowing in is such that no pumps can contain it. The only thing that can be done is to limit the negative effects of the disaster by pumping water from the floodwaters back into the river once its level has fallen. Otherwise, floodwaters in the areas affected by the natural disaster would persist for a longer time, increasing losses. The lack of suitable pumps for this purpose has again made itself felt. The fire brigade mainly has small pumps, suitable for pumping water from basements, but not from large, flooded areas. As a result, the management of the flood control operation was forced to appeal for the provision of higher efficiency pumps to the institutions that have them, and the media reported on the supply of such pumps by neighboring countries as part of aid. This does not reflect well on the flood protection system or the ability to draw conclusions from previous floods.

It should be noted that the Polish industry has design solutions and technologies enabling the production of pumps for this purpose. The thing is that the production cycle of pumps with such parameters lasts several months, so they should be ordered well in advance and not requested when a disaster occurs. Ensuring the availability of such pumps is not only a technical and financial problem, but also an organizational and logistic one. Due to the unpredictability of when and where floods will occur, it would be uneconomical to store pumps in every flood-prone location. It is more advisable to collect them in a centralized warehouse from which they would be delivered to the flood site. However, keeping pumps that are used only occasionally and ready for the next operation requires having appropriate warehouses and qualified personnel to service them, which involves significant costs.

The Powen-Wafapomp SA Group, as the largest Polish manufacturer of industrial pumps, proposes a solution to this problem. The company declares its readiness to produce appropriate pumps and then store and service them in its own warehouses, which would keep them constantly ready for use. This would free state services from the need to have warehouses and qualified specialist staff. In the event of another flood, the pumps would be put at the disposal of emergency services. The Powen-Wafapomp SA Group has two plants: in Warsaw and Zabrze, whose location coincides with the regions most at risk of flooding. Zabrze is located in the region of the upper Vistula and Oder and relatively close to Lesser Poland and Lower Silesia, while Warsaw is located in the region of the middle and lower Vistula. As a result, pumps from our warehouses can be at the action site within a few hours.

Dr. Eng. Grzegorz Pakula

1. Introduction.

Hydraulic transport of solids in pipelines is used in many industries and economies (e.g. mining, energy, mineral resources industry, food industry, chemistry, environmental protection) [1].

Without going into details, it can be said that most often (and in large masses) solids with dusty granulation (diameter of the so-called medium grain δs50 < 0 mm) and fine-grained (δs075 < 50 mm) are transported in the water stream. Thicker solids (several - several dozen mm) are transported less frequently and this usually applies to hydroexcavation and subsequent hydraulic transport of mineral aggregates, and sometimes agricultural produce.

Solids have very different shapes, regardless of size. Mixtures of dusty particles with water (called suspensions) are treated as homogeneous liquids; the velocities of liquids and solid particles during flow are virtually identical, and solid particles are distributed evenly in the flow cross-sections of pumps and pipelines. To put it simply, such suspensions can be treated as homogeneous liquids - but characterized by increased viscosity towards water, which causes a certain increase in the flow resistance of the suspensions compared to water. They are treated as non-sedimenting. Appropriate fluidity of the suspension is a condition for its ability to be pumped through pumps, transported in pipelines and spread on a flat surface. It depends on the density of solids, which should not exceed reasonable limits. Mixtures of fine-grained particles with water are two-phase heterogeneous liquids in which solid particles move slower compared to water, which causes energy losses during the flow of the mixture. Under the influence of gravity, solid particles in such mixtures fall in the pipelines (or move under the influence of centrifugal forces in the rotating channels), therefore their density in the flow sections is not uniform. A comparison of the distribution of dusty (P) and fine-grained (D) solid particles in the pipeline cross-section during the mixture flow is shown in Figure 1.

Solid particles in the mixture should remain suspended and at a certain distance (in the case of suspensions, even a very small one) from each other. This is different in the case of coarse-grained bodies, which are usually "dragged" along the bottom of the pipeline.

 

 

 

 

 

 

Since the pump efficiency and the liquid flow rate through the pipeline are measured in units of volume over time (e.g. m³ /s, m³ /h), so the parameter that most fully characterizes the composition and density of the mixture is volume concentration (volume fraction) c_v solid phase in the mixture, defined by the formula where: V_s is the volume of the solid phase in the mixture, V_w is the volume of the liquid phase (water) in the mixture, and V_m is the volume of the mixture. Volume concentration c_v Although it is an immeasurable quantity, its value has a significant impact on the fluidity (and therefore the "transportability") of mixtures and suspensions. It determines the degree of "occupation" of the space in which the mixture is located by solid particles.

Another parameter relating to the amount of mass contained in the mixture is mass concentration (mass fraction) c_M solid phase in the mixture. The relationship between c_M ac_v is as follows:

When mixtures with the same volume fraction c_v solid phases contain solids that differ in density, their mass concentrations (mass fractions) c_M   solid phases are different. For example, it can be said that hydromixtures with the same volume concentration c_v = 0,3, which includes crushed coal (ρ_s = 1400 kg / m³), fly ash (ρ_s = 2200 kg / m³) or fine sand (ρ_s = 2650 kg / m³) will be characterized by mass concentrations c_M 0,375, 0,485 and 0,532, respectively, which are very significantly different.

Figure 2 shows an overview of the uniform distribution of identical grains of spherical solids in the flow cross-section, in mixtures with different volume fractions c_v.. It is worth noting that already when c_v = 0,3, the solid particles are close to each other.

The density of the mixture ρm depends on the volume concentration cv, determined by measurement or calculated from a simple formula, in which: ρ_s – is the apparent density of the solid phase (taking into account the presence of open and closed pores and caverns), and ρ_w – is the density of water. The apparent density of solid particles should be determined using the carrier liquid in which they will be transported (in practice, water).

Figure 3 shows the dependence of the density of the mixture ρ_m on the volume fraction of the solid phase c_v, for solids with densities ρ_s = 1400, 2200 and 2650 kg/m³. This range includes the densities of the vast majority of solids transported hydraulically in large masses (e.g. fly ash, energy slags, post-flotation waste in copper ore mining, sand and gravel, limestone, dolomite, a significant part of waste from the process of enriching hard coal, crushed coal). The density of the mixture increases linearly as c increases_v and in practice it often exceeds 1500 kg/m³.

2. Efficiency of the hydrotransport system.

Volumetric yield (mixture) Q_m the hydrotransport system is expressed by a simple relationship,

where d – is the internal diameter of the transport pipeline, and v_m – is the design flow rate of the mixture.

It should be remembered that the flow rates of hydromixtures in pipelines are usually significantly higher than the water flow rates, as solids should not be allowed to settle at the bottom of the pipeline. Therefore, the volumetric efficiencies of the hydrotransport system are usually relatively significant.

Mass efficiency of the M hydrotransport system_m is given by the formula:

or in a more extensive form – a model,

which shows that the mass efficiency of the hydrotransport system increases rapidly as the pipeline diameter increases, especially since the mixture flow rates increase (to avoid the deposition of solid particles).

3. Pumps in hydraulic transport systems.

Since the flow of hydromixtures in the pipeline (and their possible lifting to a higher level) requires specific work, it must be forced by the pump. In a hydraulic transport system, the pump is an active element in which energy supplied from the outside (from the driving engine) is transferred to the mixture stream.

If the mixture flows with density ρ_m and volumetric intensity Q_m , the effective power P is transmitted in the pump_u , is the unit of weight of the mixture   (1 N) will obtain an increase in energy H (expressed in J/N, and after formal simplification of dimensions in "m") resulting from the formula:

and called the useful head of the pump. This name refers to the interpretation of this concept, according to which it defines the geometric height to which the pumped liquid (and therefore also the hydromixture) can be raised, but without any losses associated with it.

Effective power of the pump P_u expresses a familiar pattern

Transferring energy to the hydromixture is accompanied by various types of energy losses in the pump, so the power P (supplied to the pump) is greater than the useful power P_u . The pump efficiency η, defined by the formula, characterizes the efficiency of energy transfer to the pumped medium.

4. Selection of pumps for the hydrotransport system.

When selecting a pump for a specific hydraulic system for transporting solids, the following factors should be taken into account:

– required pump operating parameters achieved under the conditions of pumping the hydromixture,

– pump design solution appropriate for a specific hydromixture,

– expected durability of the pump's internal components.

4.1. Determining the pump operating parameters.

The necessary operating parameters of the pump at the expected operating point in the hydrotransport system should be determined as precisely as possible. With the expected volumetric efficiency of the Q system_m (identical to the pump efficiency), the energy transferred to the unit weight of the mixture in the pump must balance the geometric height H_z (to which the mixture will be lifted) and the amount of hydraulic losses ΣΔh_m in the transport pipeline (also related to the unit weight of the mixture), which arise during the flow of the hydromixture. The sum is the lifting height of the hydromixture transport system (H_i), the simplest diagram of which is shown in Figure 4, and the characteristics of the hydrotransport system H_i = f(Q) is shown in Figure 5.

 

Solids in the hydromixture leaving the impeller have a certain kinetic energy. In the case of dusty particles, this energy is transferred to the liquid almost completely, in the case of fine-grained particles - to some extent, and in the case of "coarser" particles it is completely dissipated.

 

The presence of solids in the pumped mixture therefore affects the operating parameters of the pumps, in particular the useful lifting height, efficiency and shaft power, which change in relation to the parameters achieved when pumping water.

Changes in pump parameters are characterized by the following dimensionless coefficients:

– lifting height change factor K_H

 

 

 

– efficiency change coefficient K_η

 

K coefficient values_H and K_η depend on the type of solids (density ρ_s and medium grain size δ_s50) and their volume fraction c_v. It is also influenced by the size of the pump. K-type algebraic graphs and relationships_H = f(Q) and K_η = f (Q) published in the literature enable approximate prediction of the impact of the presence of solids on the characteristics H = f(Q) and η = f(Q) of the pump pumping the water-solids mixture. However, they should not be treated uncritically, as they usually refer to a specific pump and specific solids. An example of such relationships quoted from [2] is shown in Figure 7. They refer to a pump with a four-blade impeller, but of unspecified size and unknown operating parameters.

 

Figure 8 shows an overview of the characteristics of the lifting height H - Q and efficiency η - Q of a centrifugal pump pumping mixtures with the same volume concentration, but containing solids of different grain sizes - against the background of the characteristics related to water.

When selecting a pump in a specific situation, you should first determine the lifting height of the pump installation H_im under the conditions of pumping the mixture (at the required system capacity Q_m), which at the expected operating point of the system must be identically equal to the useful lifting height achieved by the pump pumping the mixture (H_im = H_M). Required effective pump head H_m (in the conditions of pumping the mixture) cannot be directly used to select a specific pump, because pump manufacturers provide pump characteristics determined when pumping water. Therefore (after adopting reliable values ​​of the K coefficients_H and K_or), the useful lifting height H must be determined_w, which the analyzed pump would achieve by pumping water (because always H_w ≥ H_M).

and calculate power   on the pump pumping the mixture (P_m) from the relationship:

To more precisely adjust the pump parameters to the required ones, it may be necessary to reduce the outer diameter of the impeller or change the rotational speed (e.g. by selecting appropriate pulleys).

Note that the K ratio_H / K_η is usually close to 1 and only in the case of coarse-grained mixtures and more dense fine-grained mixtures it is lower, so the power on the pump shaft under the conditions of pumping the hydromixture increases approximately in proportion to the density ratio ρ_m /ρ_w . The increase in power demand must be taken into account when selecting the engine (and possible belt transmissions) to drive the pump.

Selecting a pump for a specific mixture hydrotransport system is often (due to the complexity of the problem) a difficult matter and it makes sense to use the support of specialists. Reputable manufacturers of hydrotransport pumps usually have experience and knowledge in this field, and relying on the suggestions of bidders without experience is risky.

4.2. Selection of the pump design solution.

Centrifugal pumps for hydrotransport are generally single-stage, although there were multi-stage versions for special needs. Examples of design solutions for hydrotransport pumps are presented in the following figures 9 and 10 [4] and 11. The common features of these pumps are large impeller widths (which allows for the "passage" of larger solids), large collecting channels - with a constant cross-section or in the form of "incomplete" spiral, the possibility of adjusting the radial gap at the impeller inlet - which allows to reduce internal leakage at the impeller inlet, the use of elements directly in contact with the pumped mixture as relatively easily replaceable, solid bearings of the rotating unit due to the usually much higher axial and radial forces, and closure water stuffing boxes. The pump shown in Figure 10 is also equipped with a specific impeller that relieves the stuffing box, which significantly increases its durability in the case of uninterrupted water supply. This solution is intended for difficult working conditions.

Pumps whose internal elements are made of hard metal materials (e.g. Fig. 9 and 10) can be used to pump hydromixtures containing grains of any size. A hard material resists "cutting" - by coarser particles - especially "angular" ones - and "grinding" by fine particles. However, pumps (Fig. 11) whose internal elements are made of elastomers (rubbers, polyurethanes) are generally intended for pumping mixtures containing fine particles. An elastomer with appropriate abrasion resistance absorbs the energy of striking particles and, to some extent, causes them to bounce off the attacked surface.

Recently, there has been a tendency to use cast steel impellers in pumps with a collecting channel and liners made of elastomer. This allows for a noticeable increase in pump efficiency.

The choice of a specific pump should be aimed primarily at achieving the longest possible operating periods between the inevitable replacements of impellers and other elements (housings, side linings), which is conditioned by the high durability of the internal elements of the pump, and this criterion is even more important than achieving slightly higher efficiency by the pump. .

It is advantageous when hydrotransport pumps have low speed (750 - 1200 (1500) rpm), because it is found that impeller wear (understood as the loss of element mass) increases approximately in proportion to the square of the rotational speed. Also, the rate of increase in the width of the radial gap sealing the rotor inlet and the wear of the stuffing box seals decreases as the rotational speed decreases.

4.3. Durability of pump components.

The impeller of the hydrotransport pump is the element subject to the fastest wear, and the places of the most intense wear are marked in Figure 12. In the case of the content of "coarse" particles in the mixture G the largest losses occur in the inlet area of ​​the rotor (inlet edges of the blades and rear rotor disc), and in the case of pumping "fine" particles D although the losses in these places are smaller, significant losses are observed at the ends of the blades, on their active side, which - when they become large enough - adversely affect the velocity distribution of the outflowing mixture, which leads to a noticeable reduction in the pump lifting height. As a result, the blades and rear disc of the rotor are thickened, especially in places of the most intense wear. The number of blades is small, z = 3 – 4 (sometimes 5), in order to maintain sufficiently large clearances at the impeller inlet and not excessively impair the suction capacity of the pump.

The bodies of collecting channels are subject to accelerated local wear in the area where the channel enters the outlet connector. as a result of "impacts" of solid bodies on the edge acting as a residual "tongue".

Rotors and replaceable metal elements (collection duct bodies and side linings) are made of cast steel containing significant amounts of alloy additives and are heat treated to increase their hardness, which requires an appropriate technological level. Replacement elements used during replacements and renovations should be of appropriate quality (ensuring appropriate durability) and for this reason it is risky to use "replacements" of undocumented quality, as it may turn out to be unprofitable. Hydromixture pumps are, for obvious reasons, inferior to water pumps in terms of efficiency, so the expected durability of their components is a decisive factor in their selection. It should also be taken into account that faster wear of the pump components leads to an extension of the period during which it operates at low efficiency.

5. Some issues regarding the operation of pumps in hydrotransport systems.

The phenomena occurring during the flow of the hydromixture through the pump are much more complex than during the pumping of water. Therefore, you should pay attention to several circumstances that affect the proper operation of the pump, which determines the uninterrupted functioning of the hydrotransport system as a whole.

5.1. Consequences of increased factor density.

The relatively high density of the mixture increases the power consumption of the pump (and the need to use an engine with appropriate power) and increases the pressure in the pump discharge port, which is important in the event of a possible need to connect two pumps in series. Not every pump is designed to operate in conditions of significant pressure increases, so such uncertainty should be clearly explained. Care should also be taken to supply water with appropriately increased pressure to the water "lock" of the stuffing box of the second pump in the series.

5.2. Ensuring geometric inflow to the pump.

The mixture should flow to the pump from the tank (with the bottom inclined towards the inlet) to the shortest possible supply pipeline located above the pump axis (Fig. 4). Pressure in the pump inlet p_sm when pumping the mixture should be significantly higher compared to the situation when pumping water. At low volume concentrations of solids in mixtures (c_v ≤ 0.1) the anti-cavitation surpluses are close to each other in both cases (NPSH3_w ≈ NPSH3_m) [5] , but even then the required ("safe") pressure in the pump inlet port when pumping a mixture must be higher due to the higher density of the mixture

(with NPSH3_m is the anti-cavitation surplus of the pump under the conditions of pumping the mixture).

When the volume fraction of solids in mixtures and suspensions c_v > 0,1, then NPSH3_m, and therefore the required pressure value in the pump inlet port, increase quickly because in the inlet area of ​​the rotor solid bodies (especially those with larger granulation) are "pressed" by the force of inertia against the rear disc of the rotor (Fig. 13) [6], and their displacement causes much greater losses, and therefore a local pressure drop. However, in the case of suspensions of very fine particles, as their density increases, additional pressure losses occur due to the existence of non-Newtonian fluid characteristics in the suspension.

Therefore, ensuring an appropriate geometric inflow of the mixture to the pump is necessary.

5.3. Pump operation at close to optimal efficiency.

The pump should permanently operate at a capacity close to optimal, i.e. close to the point of highest efficiency. Then, the bearing loads caused by the radial force acting on the rotor are relatively small, the flow in the inter-blade channels of the rotor takes place with the smallest turbulence and is most even, and the rotor wear is the slowest. Of course, the pump operation is then the most economical.

Operating the pump at increased efficiency causes increasing losses in the inlet area of ​​the impeller, and reducing efficiency during operation increases the risk of solids settling in the pipeline.

5.4. Other.

In addition to the issues mentioned above, the condition of the pump should, of course, be checked, especially the pressure in the pump discharge port, the water supply to the stuffing box, the temperature of the bearings, the vibrations of the rotating unit and the current electrical power consumption of the motor (or at least the intensity of the electrical current consumed). It is also worth remembering that the dominant influence on costs is the correct selection of the pump and its operation close to the point of maximum efficiency, and above all, avoiding pumping too dilute mixtures, because then a significant part of the energy is used to pump excessive amounts of water.

6. Ending.

Hydrotransport systems, although they contain similar elements (tanks, pumps, pipelines) and water pumping systems, operate in different conditions. Pumps must meet requirements in terms of solids throughput and durability. Tanks should be appropriately designed (slanted bottom and possibly equipped with a mixer), and pipelines and fittings should be selected appropriately. Operating parameters and values ​​characterizing the system should be determined based on the identified characteristics of the mixture or suspension and a reliable calculation methodology, and the pump selection should be made carefully.

Pumps in hydrotransport installations must perform in usually difficult conditions - primarily in terms of durability and operational reliability, and their operation requires understanding of the problems and knowledge of the supervisory team, as well as increased involvement of the staff. As a result, however, it will limit unexpected disruptions in the functioning of the system and, to some extent, also the frequency of renovations, and in the medium term it will reduce costs.

Literatura:

The literature on the issues discussed is very extensive, so due to the nature of the publication, the publication is limited only to items directly related to the issues discussed.

1.Palarski J., Hydrotransport, WNT, Warsaw, 1982

2.. Surek J., Probleme der Flüssigkeits-Feststoffgemisch – Förderung mit Kreiselpumpen, Maschinenbautechnik, Heft 9, 1972.

3. Roco NC, Wear mechanism in centrifugal slurry pumps, Journal of Science and Engineering, Vol. 46, No. 5, 1990.

4. National Forum of Producers and Users of Pumps in Mining, Lubiatów, May 6-8, 1998, (collection of materials)

5. Źiwotowskij Ł.S., Smojłowskaja Ł.A., Techniczeskaja mechanica gidrosmiesiej i primerowyje nasosy, Izd. Mashinostroyeniye, Moscow, 1986.  

6. Karielin W., Iznashiwanije łopasnych nasosov, Izd. Mashinostroyeniye, Moscow, 1973.

 

Dr. Eng. Jerzy Rokita

MSc. Zbigniew Krawczyk