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Category: Hydraulic Manifold

Two Kinds of Hydraulic Manifolds, Part II: Modular Manifolds

In Part I, we discussed the benefits of one of the two major types of hydraulic manifolds — the ‘single-piece’ manfolds, laminar and drilled-block. Today, we’re going to talk about the other major kind of manifold: the ‘modular’ manifold.

Modular manifolds have a single massive advantage over single-piece manifolds: they can be changed on the fly as the job evolves. Sometimes called the ‘erector set approach,’ modular manifolds involves a few to scores of iron, steel, or aluminum blocks, each of which has a single valve or other operator inside. Modular manifold systems can be assembled horizontally or stacked.

Most often, plates are installed between the basic ‘building block’ components to make for regular spacing and to allow for small variations in the location and size of intake and outflow passages.

The method by which the manifold blocks are connected varies by builder. Some use rods that extend through the length of the manifold and are secured on either end with nuts. Others have flanges on every block so they can be bolted together one at a time. Still others have sockets and threaded heads alongside the hydraulic passages inside each block that snap together. No matter how the blocks are connected, every block has an O-ring around every passage entering or exiting it that abuts the O-ring on the adjacent block for the purpose of forming a seal.

Most such blocks also have the necessary electrical connections built into the blocks, connecting the machinery to the appropriate solenoid. Some instead utilize channels that allow for runs of standard electric cable instead.

The limitations of modular manifolds are more dramatic than those of single-block manifolds. Internal pressure, flow rate, and the length of an individual manifold are all much more sensitive in a modular manifold than they are in a single-piece manifold.

Hydraulic manifolds are amazing tools, able to replace as much as 300 lbs of tubing and valves in as little as a single cubic foot of space. Compared to the tubing and valve setup, a manifold can cost two-thirds to half as much to assemble and install, save a mountain of space, and require only a single hydraulic filter to keep the fluid running smoothly. Whether you choose drilled-block, laminar, or modular manifolds, you’re certain to appreciate the advantages.

Two Kinds of Hydraulic Manifolds, Part I: Single-Piece

Hydraulic manifolds come in two basic types: the single-piece design that contains all of the valves and passages needed in a single metal chunk, and the modular design where each block contains exactly one valve and the various passages needed for that one valve to work. Each has their own advantages; in this article, we’ll discuss the benefits of choosing a single-piece hydraulic manifold.

Single Piece Manifolds come in two basic kinds: ‘lamniar’ and ‘drilled-block.’

Laminar Type Manifolds are composed of multiple layers of metal with holes drilled in them such that when the layers are brazed together, they form the necessary passages. As each layer is formed, the necessary mechanics of each valve are put in place. There is no limit to the number of valves — or the size of valves — that can be mounted in a laminar type manifold.

Laminar manifolds can withstand pressures of up to ten thousand psi, and can be custom-designed for any task. Because of the brazed construction and permanently shaped passages, however, it cannot be modified if changes become necessary; it must be replaced entirely. Laminar manifolds are generally more expensive than drilled-block manifolds as well.

Drilled-Block Manifolds are similarly custom-made for specific applications, and also cannot be altered after creation. Most often made from a single slab of iron, steel, or aluminum, a number of straight passages are drilled to create the flow passages and to provide the space necessary to insert the valves and other moving parts. Some such manifolds use threaded passages to screw the machinery into place; others lock the parts into place using plates attached to the manifold’s surface.

Drilled-block manifolds, being single metal pieces, can with stand more pressure than the valves within them are able to — meaning they’re effectively unbreakable, as in almost any case, a hydraulic valve will give out and the fluid will be ejected before the manifold itself cracks. They’re also the least expensive kind of manifold to produce, in general.

Single-piece manifolds in general have the advantages of withstanding greater pressures and being less expensive than modular manifolds. To learn the advantages of modular manifolds, come back next time for Part II.

Keep Your Hydraulic Manifolds Working Longer By Reducing Cavitation

Cavitation is a deeply interesting physical phenomenon that occurs when liquids are subjects to sudden massive changes in speed. For example, if fluid moving under 40 megapascals (MPa) of pressure suddenly hits a hydraulic valve and the pressure drops to 20MPa, the sudden increase in speed (described by Bernoulli’s Theroem) would lead us to the conclusion that a small bubble of nearly empty space — a hard vacuum — would open up within the fluid at the point of pressure drop.

This does in fact happen, and the bubble both forms and then collapses at supersonic speeds, creating a tiny sonic boom within the hydraulic fluid itself. The shockwave of the bubble’s collapse generates enough energy that it can literally tear apart nearby molecules of hydraulic fluid — or, if the bubble collapses near the inner walls of the manifold, it can rend the molecules of the manifold itself, causing “erosion”.

Reducing Cavitation
That’s perhaps a misnomer — there’s no realistic way to reduce cavitation within a given system short of reworking it to avoid sudden pressure changes. But the critical phrase above is “if the bubble collapses near the inner walls of the manifold.” It may not be possible to realistically prevent cavitation bubbles, but it is possible to more carefully control where those bubbles collapse.

The simple rule of thumb is this: increase backpressure by 5% of the total drop in pressure across the valve or metering edge (or whatever else is causing the change in pressure.) In the above example, where pressure drops by 20 MPa, an increase in backpressure of just 1 MPa should force the cavitation bubbles toward the middle of the fluid stream, thus causing them to collapse where they will do as little damage as possible to the hydraulic manifold.

If that doesn’t work, switching from an aluminum manifold to a ductile iron manifold will reduce the rate of “erosion” by 90%. Alternately, if possible, increasing backpressure to 10% of the total pressure drop will have a similar effect, though often switching manifold materials is the easier solution.

How do you know if it worked? Listen carefully at the point of pressure change. White noise coming from within the system is the sound of cavitation bubbles collapsing; if the noise is reduced or gone, your attempt was successful.

How to Buy an Industrial Hydraulic Power Unit

Hydraulic power units (HPUs) are everywhere — many jackhammers, most auto lifts that mechanics walk under, many fishing boats’ net-haulers, almost every big yellow machine you see at a construction site all use hydraulic power units. Obviously they come in quite a variety — how do you know you’re getting the right one for your needs?

At it’s simplest, when you need a single HPU to power a single tool, the answer is usually written right on (or in the instruction booklet of) the tool in question. You need an HPU that provides at least enough actual hydraulic fluid to power the tool (for handheld tools, a half-gallon is usually all you need, but for industrial applications, a 250 gallon tank isn’t unheard of.) It also needs to supply adequate pressure to get the job done — your typical hydraulic jackhammer, for example, won’t function at less than 1300 psi.

But the simplest is hardly adequate to most industrial applications. If you’re, say, a machine shop, and you need a single hydraulic power unit that can provide hydraulic power to a dozen different metal grinders, pipe benders, sheet stampers, and so forth, you’ve got a lot more to worry about than just matching one machine’s numbers to another’s.

Fortunately, it’s still not all that difficult — many providers have or can custom-build a hydraulic manifold that can ensure that, as long as your HPU is capable of producing adequate flow and pressure to handle all of the jobs you want to simultaneously accomplish, each tool gets the right amount of fluid at the right pressure. Such a manifold will have pressure-reducing valves and both automatic and controllable switches that will ensure no machine gets too much pressure or fluid for it’s own operation, but all machines get enough of each.

Those aren’t the only details — there are other considerations that range from the possible need to move your HPU to different areas at different times, or matching the power consumption of your HPU to the type of power provided by your shop’s outlets — but those should mostly be intuitive for your typical shop manager.

Hydraulic Cylinders: The Might Behind America’s Construction Crews

Hydraulic cylinders are used in large- and small-scale industry, from hand-held manual tools to massive construction vehicles and robots. A hydraulic cylinder provides the force that moves hydraulic fluid through its pipes, valves, and manifolds, where on the other end, it eventually reaches another cylinder that translates the movement of the hydraulic fluid into the movement of machinery. Hydraulic cylinders can be found in cars, cranes, oil rigs, bulldozers, draw bridges, and even in professional-grade long-reach pruning shears.

The primary components of a hydraulic cylinder are the cylinder, the piston head, and the piston rod. Mechanically, they work together much like a syringe — the piston rod pushes the piston head, which forms an airtight seal with the cylinder. The piston head forces the hydraulic fluid through the hole at the end of the cylinder. Because fluid cannot be compressed, and the entire sequence of pipes, valves, and manifolds is already full of fluid, any motion by the cylinder on one of the hydraulic series affects the cylinder on the opposite side without any delay.

Generally, the piston arm is powered by an electric motor, though there are plenty of exceptions. The outside of the cylinder and the piston arm are often painted with chrome for aesthetic purposes, but the inside of the cylinder and the piston head are under constant stress (as the hydraulic fluid pushes out equally on all surfaces of it’s container), so painting them would be counterproductive.

Cylinders come in several varieties. There are hundreds of different bores of cylinder available. They come in single-stage and double-stage (depending on whether you expect the force to some exclusively from one side or you need both sides to be able to move the other.) Cylinders are generally attached to reservoirs that contain additional hydraulic fluid and filters that keep the fluid free of impurities.

Quite often, a single powerful cylinder is used to power a variety of different motions within the same machine. In that case, a hydraulic manifold that can ‘switch’ one cylinder between several different endpoints is put into play. For any machine that only needs to make one motion at a time, a single hydraulic cylinder operating on a manifold makes for a lower cost of ownership over time.

Save Space and Time With a Hydraulic Manifold

Hydraulic manifolds are powerful and compact valve assemblies that do for hydraulics very much what integrated circuits do for computers: they create a system where a relatively simple set of hydraulic inputs can be used to create a startling array of hydraulic outputs. The end result is a single smallish chunk of machinery that replaces hundreds of feet of tubing, hose, fittings, and line-mounted valves. While hydraulics still use liquid rather than electrons – and thus a hydraulic manifold will never reach the staggeringly small size of a modern integrated circuit – they do squeeze a huge amount of functionality into a very small space.

That’s not the only advantage to a hydraulic manifold, however: there’s also the issue of leakage. That aforementioned hundreds of feet of tubing, valves, hose, and fittings means scores of individual parts each one of which can go wrong and cause a leak (which is a death sentence for a hydraulic machine). Hydraulic manifolds are prebuilt out of as few parts as possible for the various valves to do their jobs, and that means significantly less opportunity for leaking (and correspondingly less need to spend time and labor on fixing the leaks.)

Hydraulic manifolds also require less assembly, which means easier maintenance and troubleshooting, which again saves money on the project’s bottom line. With so many components built into or mounted upon a single common manifold, the need for a tech to climb all over Kingdom Come to find the leaky piece is dramatically reduced. Should the hydraulic manifold itself fail, there are dozens of identical units – swapping one out is the job of less than an hour, and that’s in poor circumstances. Furthermore, oftentimes the faulty manifold can be repaired on the spot and kept en situ as a swap-in replacement should something happen to the manifold that was just installed.

Modern hydraulic manifolds also provide advanced capabilities like load sensing, which allows the manifold itself to detect how much pressure is needed to lift a certain load and provide exactly as much as is needed, conserving hydraulic power to direct elsewhere for other jobs. Some such manifolds even have a hydraulic filter built into them so as to further reduce technician’s walking time. When everything is in one place, you waste a lot less time getting from wherever you are to where the problem is.