Hydraulic symbols: Part three: Valves

Abstract

Similar to human health, the importance of hydraulics sometimes becomes apparent only in her absence. Images and motives of agricultural workers from the past times and centuries can look attractive only on paintings of arts. In reality, it was a very hard and sometimes quite dangerous job. The introduction of hydraulics in construction of modern farming machines, agriculture is less demanding for all farm workers, but also more efficient, which is of particular importance for providing enough food for the growing world during the 20-th century. Achieving high efficiency, reliability and long service life of these systems requires sophisticated diagnostics and failure repairment, regular maintenance and careful use of each hydraulic system, and this is only possible with a good knowledge of the functional principles of all elements, their connections and the whole system. However, modern hydraulic systems of agricultural machines are often very complicated, and the construction of their components is too complex for detailed graphic representation within the whole corresponding hydraulic installation. Therefore, instead of detailed representation of the components, schematic diagrams are used. This manuscript represents a logical continuation of the first and second parts of the paper, devoted to the general symbols, labels of measuring instruments and indicators (part one), as well as pumps and actuators (part two). The third) part of the paper presents the hydraulic symbols of the system control elements - hydraulic valves. The graphical symbols of these components are defined by ISO standards.

Slično ljudskom zdravlju, značaj hidraulike ponekad postaje vidljiv samo u njenom odsustvu. Slike i motivi radnika u poljoprivredi iz prošlih vremena i vekova mogu izgledati privlačno samo na umetničkim slikama. U stvarnosti, to je bio veoma naporan i ponekad prilično opasan posao. Uvođenje hidraulike u konstrukcije savremenih poljoprivrednih mašina za poljoprivrednu proizvodnju, učinilo je poljoprivredu fizički manje zahtevnom za radnike, ali i efikasnijom, što je od posebne važnosti za obezbeđenje hrane rastuće svetske populacije tokom XX veka. Postizanje visoke efikasnosti, pouzdanosti i dugog radnog veka ovih sistema zahteva naprednu dijagnostika i otklanjanje kvarova, redovno održavanje i pažljivo korišćenje svakog hidrauličkog sistema, a to je moguće samo uz dobro poznavanje funkcionalnih principa svih elemenata, njihovih veza i sistema u celini. Međutim, savremeni hidraulički sistemi poljoprivrednih mašina često su veoma komplikovani, a konstrukcija njihovih komponenata previše kompeksna za detaljno grafičko predstavljanje u sastavu pripadajuće hidrauličke instalacije. Zato, umesto detaljnog predstavljanja komponenata, koriste se odgovarajući šematski dijagrami. Ovaj tekst predstavlja logičan nastavak prvog i drugog dela rada, posvećenih opštim simbolima, oznakama mernih instrumenata i indikatora (prvi deo), kao i pumpama i izvršnim elementima (drugi deo). Treći deo rada prikazuje hidrauličke simbole elemenata za upravljanje - hidrauličke ventile. Grafičke simboličke oznake upravljačkih komponenata su definisane ISO standardima.