Research on the assessment of flow and pressure pulses in oscillating hydraulic intensifiers

Some mining activities, such as interventions in the event of accidents, are carried out in narrow spaces, using small (single-or double-acting) hydraulic cylinders to obtain high static (press and squeeze) or dynamic (push and pull) forces. The opposite load of these forces can occur: at the end of the advance stroke; on the entire advance stroke; on both directions. There are two types of pumping units for these cylinders: units with positive displacement pumps and high-pressure hydraulic components, units with positive displacement pumps and low-pressure hydraulic components, plus oscillating pressure intensifiers (miniboosters). The second type, which generates high pressures with low-pressure systems, has the following advantages: lower price, higher energy efficiency and operational safety. The manufacturers of miniboosters do not specify the amplitude and frequency of pulses of pressure oscillators. In order to use these hydraulic pressure intensifiers in dynamic applications specific to mining activities, under conditions of maximum safety, the authors propose a solution for a test stand on which one can determine: flow and pressure pulse characteristics, their influence on the uniform displacement of the load of hydraulic cylinders supplied by pumping units equipped with miniboosters, functional characteristics, in dynamic and stationary modes, of pumping units with embedded miniboosters.Niektóre prace górnicze, takie jak akcja ratunkowa, są wykonywane w wąskich przestrzeniach, przy użyciu małych siłowników hydraulicznych (jednostronnego lub dwustronnego działania), w celu uzyskania dużych sił statycznych (naciskających i ściskających) lub dynamicznych (pchających i ciągnących). Przeciwny zwrot tych sił może wystąpić: po całkowitym wysunięciu tłoczyska; przy dowolnym wysunięciu tłoczyska przy przemieszczaniu tłoczyska w obu kierunkach. Istnieją dwa typy zespołów pompujących dla tych siłowników: z pompami wyporowymi i wysokociśnieniowymi elementami hydraulicznymi, z pompami wyporowymi i niskociśnieniowymi komponentami hydraulicznymi oraz oscylacyjnymi wzmacniaczami ciśnienia (miniboostery). Drugi typ, który generuje wysokie ciśnienia za pomocą systemów niskociśnieniowych, ma następujące zalety: niższa cena, wyższa efektywność energetyczna i bezpieczeństwo eksploatacji. Producenci minibosterów nie określają amplitudy i częstotliwości impulsów oscylatorów ciśnienia. Aby zastosować te hydrauliczne wzmacniacze ciśnienia w dynamicznych zastosowaniach specyficznych dla działalności górniczej, w warunkach maksymalnego bezpieczeństwa, autorzy proponują koncepcję stanowiska badawczego, na którym można określić: charakterystyki pulsacji przepływu i ciśnienia, ich wpływ na równomierny rozkład obciążenia siłowników hydraulicznych zasilanych przez agregaty pompowe wyposażone w minibostery, charakterystykę funkcjonalną w trybie dynamicznym i stacjonarnym zespołów pompowych z wbudowanymi miniboosterami

Use of pumping units equipped with oscillating hydraulic pressure intensifiers for displacement of cylinders with heavy loads over the entire stroke

Working and moving in confined, limited and narrow spaces, specific to underground mining activities, also requires the use of hydraulically operated equipment, capable of developing large forces, with small dimensions. An example of such equipment includes pumping units comprising low-pressure electric pumps and oscillating hydraulic pressure intensifiers. They use low pressure in the primary side of the intensifier and generate high pressure in the secondary side of the intensifier. Such pumping units are usually used to achieve and maintain high pressure, either in the volumes of closed spaces (in strength tests on pipes and tanks) or at the end of the active stroke of hydraulic cylinders (in hydraulic presses). On an experimental laboratory bench, which comprises a test cylinder, powered by a pumping unit, equipped with an oscillating hydraulic pressure intensifier, and a load cylinder, powered by another pumping unit, with the possibility of load control, the authors show that: the application range of these pumping units can be extended in the third direction, too, useful for underground mining activities, namely for drive of hydraulic cylinders with low gauge / displacement speeds and constant high load (high working pressure) over the entire working stroke length; the uniformity of displacement of these cylinders, with load throughout the stroke length, which are powered and driven with such pumping units, is slightly affected by the pulsating mode of operation of the hydraulic pressure intensifier. A set of experimental measurement results is presented for a constant value of the load over the entire displacement stroke of the test cylinder

Predictive maintenance techniques for wear reducing and elimination of equipment failures in hydrostatic drive systems

Maintenance is a very important activity, which is necessary for the good operation of any technical system, even for the hydraulic drive systems. The predictive maintenance evaluates the state of technical performances of a system, by identifying the wear and thus avoiding the failures of the equipment. Using three methods of the predictive maintenance, namely infrared thermography, vibration analysis and oil analysis, the authors present their results of an experimental research on hydraulic pumps. The authors obtained thermograms, vibration spectra and diagrams of the oil contaminants which helped them indicate the proper or the malfunction of the studied pumps. Although they were only made on pumps, their investigations highlight the need of widely implementation of these modern and efficient methods in the industrial activities for the quick monitoring of the hydraulic machinery and equipment wear, before their failure occurs. Obviously, the goal is to have strong maintenance instruments in hydraulic drive systems diagnosis.Konserwacja to bardzo ważna czynność, niezbędna do prawidłowego działania każdego systemu technicznego, nawet hydraulicznych układów napędowych. Konserwacja predykcyjna ocenia stan wydajności technicznej systemu poprzez identyfikację zużycia i unikanie w ten sposób awarii urządzeń. Wykorzystując trzy nowoczesne metody konserwacji predykcyjnej, tj. termografię w podczerwieni, analizę drgań i analizę oleju, autorzy przedstawiają wyniki badań eksperymentalnych hydraulicznych pomp. Autorzy uzyskali termogramy, widma drgań i diagramy zanieczyszczeń olejowych, które pomogły wskazać prawidłową lub nieprawidłową pracę badanych pomp. Chociaż zostały wykonane tylko na pompach, ich badania podkreślają potrzebę szerokiego wdrażania tych nowoczesnych i efektywnych metod w działalności przemysłowej do szybkiego monitorowania zużycia maszyn i urządzeń hydraulicznych, zanim dojdzie do ich awarii. Oczywiście celem jest posiadanie mocnych narzędzi konserwacyjnych w diagnostyce hydraulicznych układów napędowych

Research on the use of hydro-pneumatic accumulators in order to reduce the flow rate and pressure pulsations of oscillating hydraulic intensifiers

Oscillating hydraulic pressure intensifiers, of the minibooster type, are supplied at the inlet, in the primary, by low-pressure pumps and provide, at the outlet, in the secondary, high pressure to the hydraulic consumers (linear or rotary hydraulic motors under load). The pressure increase in the secondary, proportional to the amplification factor of the intensifier occurs at a much lower flow rate than the supply flow rate, and thus the two hydraulic parameters (pressure and flow rate) at the outlet of the intensifier are affected by oscillations. Because of this, the miniboosters are designed for static applications, which require low displacements of hydraulic motors. The authors aimed to expand the field of use of miniboosters by reducing the flow rate and pressure pulses with the help of hydro-pneumatic accumulators mounted on the primary and secondary of the intensifiers. If these pulsations can be mitigated, then low-pressure pump units of small dimensions, equipped with miniboosters, can be used in dynamic mining-specific applications, in complete safety, such as, for example, those involving relatively uniform displacement, under load, of some hydraulic jacks. A numerical simulation model developed in Simcenter Amesim highlights the effect of using hydro-pneumatic accumulators on the mitigation of flow rate and pressure pulsations of the oscillating hydraulic intensifiers. Numerical simulations performed with and without hydro-pneumatic accumulators mounted on the primary and secondary of the intensifier highlight the following aspects: • hydro-pneumatic accumulators can be used successfully for the partial damping of flow rate and pressure pulses, but they must be dimensioned for each specific application and work optimally for a relatively narrow pressure range; • using hydro-pneumatic accumulators can sufficiently improve the uniformity of displacement and the velocity of displacement of a hydraulic cylinder, so that it can be used in less demanding dynamic applications, as well

Optimization of Manufacturing Processes by Reducing the Costs of Tools and Equipment on Hydraulically Operated High-Pressure Technological Lines

Most technological manufacturing lines include hydraulically operated stationary tools, devices and equipment. During a manufacturing cycle, there are phases, usually short, in which part of the hydraulic cylinders of the drive systems concerned, with small gauges and displacement speeds, have to generate / maintain high clamping or pressing forces, which implies functioning at high working pressures. The solution for such cylinders is to use modular hydraulic pumping units comprising: oil tank; low-pressure electric pump; hydraulic directional valve for starting, stopping and changing the direction of displacement of the cylinder; electric pump pressure control valve; pressure filter; return filter; oscillating hydraulic pressure intensifier (minibooster mounted directly on the cylinder). Such pumping units, which consume low pressure (in the primary side of the minibooster) to generate high pressure (in the secondary side of the minibooster), are cost-effective when it comes to the procurement of components, installing them, the space required for installation, and their maintenance, too. The classic applications of using them are for achieving and maintaining high pressure values, either in volumes of closed spaces (endurance tests on pipes and tanks), or at the active stroke end of hydraulic cylinders (hydraulic presses). The authors demonstrate, on a laboratory test bench, the following: - The range of applications of such pumping units can be extended in a third direction, namely for actuation of hydraulic cylinders with low gauge / speeds and constant high load (high working pressure) over the entire stroke; - The uniformity of displacement of these cylinders with load over the entire stroke, fed and actuated by such pumping units, is weakly affected by the pulsating mode of operation of the hydraulic pressure intensifier