In previous articles, we discussed the heart of the manifold system – spool valves (from NG6 all the way to the gigantic NG32) and connection plates, which eliminate hose tangles. But what if, in addition to simply "pushing" oil, you need to precisely adjust the cylinder speed or protect a heavy load from uncontrolled descent?
In a traditional system, you would have to cut hoses and insert external valves on T-fittings. In a CETOP system, you do it completely differently – you build a tower.
Meet sandwich (modular) valves. Discover why engineers call them "hydraulic Lego bricks" and how they can revolutionize the construction of your machines.
1. What is a sandwich valve and how does a "hydraulic sandwich" work?
A sandwich valve looks like a steel or aluminum block with through holes, whose shape perfectly matches the valve base (e.g., in NG6 or NG10 standard).
Its genius lies in its mounting method. No hoses are connected to it! This valve lays flat between the connection plate and the main valve, and then the entire "sandwich" is bolted together with four longer screws. Oil flows from the plate, through the sandwich valve, to the valve (and back) solely through internal channels.
In this way, you can stack several valves one on top of another in one block station, creating an advanced control system within a few centimeters.
2. Three most important types of sandwich valves
Depending on the function your machine needs, you can insert the appropriate module into your tower. The most popular ones are:
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Twin pilot-operated check valves: An absolute must-have in machines that lift heavy loads (e.g., crane outriggers, presses). The valve "locks" the oil in the cylinder. Thanks to this, even if the supply hose breaks or you turn off the pump, the cylinder will not drop an inch.
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Throttling and check valves (Restrictors): Used to regulate speed. If your cylinder extends too aggressively, a restrictor allows you to smoothly "throttle" the flow on channel A or B. They have convenient knobs, allowing you to adjust the machine's operating speed with pharmaceutical precision.
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Relief and reducing valves: Imagine you have a system operating at 200 bar, but one delicate cylinder in the system cannot exceed 100 bar. You insert a sandwich-type reducing valve into its section, which lowers the pressure only for that specific station. The rest of the machine operates at full power!
3. Why switch from external valves to sandwich valves?
The use of the CETOP modular system brings numerous benefits for designers and maintenance departments:
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Elimination of leaks: Each external pipe valve means at least two additional fittings and threads. In a sandwich system, you eliminate potential points of failure. Sealing is achieved using O-rings compressed between the plates.
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Space saving: The machine becomes incredibly compact. All hydraulic "logic" is contained in one aesthetic control block, rather than hanging on hoses scattered across the entire frame.
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Instant modification: Does the machine need a new function (e.g., speed control)? Simply unscrew the valve, add a sandwich restrictor, use 4 cm longer screws, and you're done! Modification time: 5 minutes.
Summary
Sandwich valves are the ultimate proof that the plate system is the most well-thought-out system in the history of power hydraulics. It allows for the construction of clean, leak-free, and fault-tolerant systems that can be expanded like building blocks.
If you are designing a new control block or want to modernize an old machine, at BRhydraulic you will find a full range of sandwich valves in all sizes: from the agile NG6 (CETOP 03), to the powerful NG25 (CETOP 08). Contact us – we will help you arrange the perfect hydraulic sandwich!
