The impact of hydraulic systems on the human being and the environment

Some hazards posed by the operation of hydraulic systems, connected with low-frequency vibrations and noise are presented. Special attention is focused on infrasounds. The sources of low-frequency vibrations and noise and the ways of reducing them are indicated. Moreover, this paper deals with the effects of external mechanical vibrations on hydraulic valves. An original solution ensuring the effective reduction of vibrations and noise in a wide frequency range, i.e. a wide-band damper of pressure fluctuations, also performing the function of an acoustic filter, is proposed. The results of preliminary experimental tests of simple vibration insulators are reported. The effectiveness of the damper has been confirmed by the results of laboratory tests and tests carried out on engineering machines working in real conditions.Problems relating to the noise emitted into the environment by machines equipped with hydraulic systems are covered by Polish and EU standards and directives, e.g. PN-ISO 9612:2004, Directive No. 2000/14/EC and Directive No. 98/37/WE

THE IMPACT OF HYDRAULIC SYSTEMS ON THE HUMAN BEING AND THE ENVIRONMENT

Some hazards posed by the operation of hydraulic systems, connected with low-frequency vibrations and noise are presented. Special attention is focused on infrasounds. The sources of low-frequency vibrations and noise and the ways of reducing them are indicated. Moreover, this paper deals with the effects of external mechanical vibrations on hydraulic valves. An original solution ensuring the effective reduction of vibrations and noise in a wide frequency range, i.e. a wide-band damper of pressure fluctuations, also performing the function of an acoustic filter, is proposed. The results of preliminary experimental tests of simple vibration insulators are reported. The effectiveness of the damper has been confirmed by the results of laboratory tests and tests carried out on engineering machines working in real conditions.Problems relating to the noise emitted into the environment by machines equipped with hydraulic systems are covered by Polish and EU standards and directives, e.g. PN-ISO 9612:2004, Directive No. 2000/14/EC and Directive No. 98/37/WE

Reduction of infrasounds in machines with hydrostatic drive

Some hazards posed by the operation of hydraulic systems, connected with low-frequency vibrations and noise are presented. Special attention is focused on infrasounds. The sources of low-frequency vibrations and noise and ways of reducing them are indicated. An original solution ensuring the effective reduction of vibrations and noise in a wide frequency range, i.e., a wide-band damper of pressure fluctuations, also performing the function of an acoustic filter, is proposed. The effectiveness of the damper was confirmed by the results of laboratory tests and tests carried out on engineering machines working in real conditions

Wybrane metody redukcji pulsacji ciśnienia w układach hydraulicznych

W artykule przedstawiono wybrane problemy w eksploatacji układów hydraulicznych i mikrohydraulicznych. Szerzej omówiono zjawisko pulsacji ciśnienia, w szczególności skupiając się na oddziaływaniu zewnętrznych drgań mechanicznych na układ mikrohydrauliczny. Przedstawiono wyniki, które świadczą o powstawaniu składowych widma amplitudowo-częstotliwościowego pulsacji ciśnienia, powodowanych wzbudzaniem się drgań grzybka mikrozaworu przelewowego, którego korpus poddawany był drganiom mechanicznym. Zaproponowano na drodze symulacyjnej możliwości redukcji drgań korpusu mikrozaworu w oparciu o metody wibroizolacji biernej.The article presents elected problems with exploitation hydraulic and microhydraulic systems. There discussed in more detail about phenomenon of pulsation, especially about influence of external effects of mechanical vibration on microhydraulic system. Presented results indicate on formating components of the amplitude-frequency spectrum of pressure pulsation caused by exciting bypass valve poppet's vibration, which body was subjected to mechanical vibration. It was suggested, due to computer simulations based on passive vibroisolation, new possibilities of reducing microvalve's body vibrations

Microhydraulics and hydrotronics development areas of fluid drives

W artykule przedstawiono wybrane przykłady zminiaturyzowanych elementów hydraulicznych. Zaprezentowano wyniki prac własnych dotyczących przepływów w mikroelementach hydraulicznych (mikrozaworze wzniosowym, mikroprzewodzie hydraulicznym) oraz wydzielenia obszaru pracy stabilnej mikrozaworu hydraulicznego. Zwrócono uwagę na hałaśliwość pracy układów mikrohydraulicznych, poddając, jako przykład, analizie mikrozasilacz hydrauliczny.In the paper some selected examples of miniaturized hydraulic components were presented. Some results of tests of flow in hydraulic microcomponents (lift microvalve, hydraulic micropipe) and creating of stable work of hydraulic microvalve were discussed. Special attention was focused on noise problem of microhydraulic systems. This problem was considered in example of microhydraulic power unit

Koncepcja oraz badania wstępne stanowiska badania odporności na drgania mikrozaworów hydraulicznych

W artykule omówiono wymagania stawiane układom mikrohydraulicznym. Wskazano na występujące zakłócenia pracy. Zaprezentowano koncepcję stanowiska badawczego do identyfikacji wpływu zewnętrznych drgań mechanicznych na elementy mikrohydrauliczne. Jako przykładowy element mikrohydrauliczny poddawany drganiom mechanicznym wykorzystano mikrozawór maksymalny.The paper describes the requirements set for microhydraulic units. Disruptions that occur during use were pointed out. This paper shows the concept of test rig designed specifically, to identify an influence of external mechanical vibrations on microhydraulic elements. Microhydraulic pressure relief valve was used as an exemplary element on which external vibrations were applied

The influence of external mechanical vibrations on hydraulic microvalves. Test stand design and preliminary tests

Fluid pressure fluctuations in a microhydraulic system can be caused by fluctuations in the rate of fluid delivery, due to the operational kinematics of the micropump’s displacement elements, as well as by external excitations. This paper presents the requirements for microhydraulic systems and indicates the disturbances that can occur during operation. A test stand was designed to identify the impact of external mechanical vibrations on microhydraulic elements. Test stand was equipped with a measuring system to generate and record vibrations and examine their effect on the operation of microhydraulic components. Set parameters and operating conditions of the system during measurements were given. A relief microvalve was chosen, as a representative microhydraulic component. Based on the measurements, additional component derived from external vibrations was identified in frequency spectrum of pressure pulsations

Pumps capacity fluctuations in systems with hydraulic long line

W artykule przedstawiono sposób obliczania charakterystyk częstotliwościowych w układach z hydrauliczną linią długą. Do obliczeń posłużono się metodą macierzową, w której użyto modelu quasi-ustalonych strat tarcia. Taki sposób opisu traktuje przewód jako tzw. czwórnik hydrauliczny. Układ hydrauliczny z zadanym obciążeniem, wyrażonym w postaci impedancji końcowej, przedstawiany jest w postaci tzw. jednowrotnika, który posłużył do wyznaczania transmitancji operatorowych układu. Na bazie tych transmitancji, przy wymuszeniu harmonicznym można sporządzić wykres modułu transmitancji w funkcji długości przewodu zasilającego przy danej częstotliwości wymuszeń, utożsamianej z podstawową harmoniczną pulsacji wydajności pompy wyporowej. W wyniku symulacji numerycznej uzyskuje się długości przewodu, przy których następuje wzmocnienie amplitud pulsacji ciśnienia, utożsamiane z rezonansem hydraulicznym.In the paper a method of calculation of frequency characteristics of systems with hydraulic long line was presented. For calculations a matrix method with quasi-stationary friction losses model was used. Presented method is based on a hydraulic four-terminal network. Hydraulic system with load is presented by hydraulic one-port component which was useful to determine system operational transmittance. On the basis of these transmittances it’s possible to create a diagram of magnitude of system transmittance in function of supplying pipe length for selected frequency of input function (identified with basic harmonic pulsation capacity of positive displacement pump). On the basis of simulations some pipe’s length are determined corresponding to pressure pulsation amplification (identified with hydraulic resonance)

Low-frequency pressure fluctuation damper based on hydropneumatic spring with constant stiffness

A wide spectrum of pressure fluctuation frequencies occurs in hydraulic systems. Particularly hazardous and difficult to eliminate are pressure fluctuations in the range up to 50 Hz, resulting in the generation of infrasounds by machines equipped with a hydrostatic drive. The best protection against the harmful effect of ultrasounds is to suppress them at the very source, i.e. to eliminate the causes of the generation of this noise. This paper presents a concept of reducing pressure fluctuation in the range of low excitation frequencies by means of a low-frequency damper of special design. The basis for designing pressure fluctuation dampers effective in reducing pressure fluctuation amplitudes in the range of low frequencies (< 50 Hz), which also function as acoustic filters of the generated infrasounds, is provided. The effectiveness of the low-frequency damper in reducing pressure fluctuation amplitudes has been experimentally tested. The damper was found to be most effective when its eigenfrequency coincided with the excitation frequency to be reduced

Test stand for estimation of static and dynamic characteristic of proportional hydraulic valves

W artykule przedstawiono stanowisko do wyznaczania charakterystyk statycznych i dynamicznych zaworów sterowanych w technice proporcjonalnej. Opisano układ sterujący rozdzielaczem proporcjonalnym i wielokanałowy tor sterująco-pomiarowy ze specjalistycznym oprogramowaniem umożliwiającym generowanie dowolnego w czasie przebiegu sygnału sterującego oraz na akwizycję danych pomiarowych. Przedstawiono przykładowe wyniki wyznaczania charakterystyk proporcjonalnego rozdzielacza regulacyjnego najnowszej generacji. Zamieszczono przykład zastosowania uzyskanych wyników pomiarowych do uściślenia modelu matematycznego sterowania rozruchem przekładni hydrostatycznej pod kątem minimalizacji hałasu.In the paper a test stand for determination of static and dynamic proportional valves characteristic was presented. A multichannel test stand was developed and presented in the paper. Moreover control system of proportional directional control valve and multichannel slotted line with special software for generation several control signals were presented too. Moreover some experimental tests results were presented for high-response proportional directional control valve. An example of application obtained results for mathematical model refinement of control of hydrostatic transmission start with minimum noise criterion was presented