Monoblock valves are simpler than sectional valves and monoblock valves can work under higher pressure. The body type of the valve permits higher pressure because of robust, covered structure. Sealing of monoblock valve are better than sectional valves so applications which uses higher pressure than 350 bar prefer monoblock valves. Burst pressure of the monoblock valves are around 700 – 900 bar so it can work safely under 350-400 bar. Mostly monoblock valves do not have auxiliary valves such as anti-shock or anti cavitation valves.
Sectional valves stated in other words sectional directional control valves are highly flexible and have various auxiliary valves such as anti-shock, anti-cavitation, electro hydraulic pilot operated unloader, hydraulic pilot unloader etc. Generally sectional valves have check valve for each work section are from 1 to 12 sections with open center, closed center hydraulic circuits. Various sections used together such as series, parallel or tandem circuit valve. Also sectional valves may have intermediate pump and tank sections.
Between two sections it is possible to add pressure or flow compensator. As described above Sectional valves have various options when compared to monoblock valves. However there are some disadvantages of the sectional valves is lower working pressure when compared to monoblock valves. Sectional valves maximum working pressure should be 320 bar. Total sizes of the sectional valves are not as compact as monoblock valves, some space limited applications do not prefer big valves as sectional valves.
One of the other main points which have big effect on quality of directional control valve is internal cleanliness of the valve body. After casting process the directional control valve body should be cleaned with special treatments against slag dirt and sand core dirt. Remnants inside the hydraulic valve is not only because of casting but also is because of chips after machining. These remnants have huge effect on performance of spool valves. Contamination level of directional control valve which works under pressure lower than 140 bar is 20/18/15 and filtration level is 20 micron, however contamination level of directional control valve which works under pressure higher than 200 bar is 18/16/13 and filtration level is 5 micron. If contamination and filtration standards are not applied, dirt damages all system components and spool valve.
DIRECTIONAL CONTROL VALVES
Directional control valves are used in various hydraulic projects. Almost in every project there is at least one directional control valve in the system. Due to high volume of consumption there are many companies around the world who produces s. How you should choose the right spool valve and what should be specifications of the spool valve. Typically hydraulic valves are made of cast iron. Sand cores are used inside the cast iron hydraulic valve to create cavity for internal rooms and oil drain.