A
hydraulic
manifold,
sometimes called a hydraulic valve block, is a machine component which
regulates the fluid flow between the actuators, pumps and other components
within a hydraulic system. In terms of functionality, it is similar to a
switchboard of an electric circuit as it allows the operator to control the
movements of fluid between different parts of a hydraulic machinery. For
instance, in a machine such as a backhoe loader, the manifold turns on, turns
off and diverts the flow of the fluid towards the telescopic arms of the both
the front and backbuckets. In this case, the hydraulic manifold is attached to
the levers present in the operator's cabin of the machine, and the operator
uses it to get the desired movements. A manifold is created by attaching
several assorted hydraulic values to one another. The different combinations of
the states of these values is responsible for the sophisticated control
behaviour of a manifold. The flow of the pressurized oil is controlled by
valves located inside the manifold and is then passed via the hoses to a work
device, like a hydraulic motor. Apart from providing a neat logical layout, the
consolidation of components inside a hydraulic valve block reduces the number
of fittings, assembly time and avoids sudden pressure drops and leak points.
Some engineers consider manifolds as black boxes that may not be of much help
while troubleshooting. However, if the system is well-designed by placing the
test points in key places, identifying the problem which causes a malfunction
is not that difficult. By connecting a transducer to a test point, the data can
be linked to the machine's PLC and may be displayed on the Human Machine
Interface (HMI). Major applications that use manifolds include heavy
construction machinery, machine tools, value operations, material handling and
production equipment, marine machinery, food processing, and off-highway
machinery.
Types Of Hydraulic Manifolds: There are two basic
types of hydraulic manifolds or hydraulic valve blocks. The first type comes in
a mono-block design which holds the values and passages of the entire system.
The second type is a modular block design that supports only 1 or 2 valves and
has special interconnecting passages for the values. In real world scenarios, a
modular block unit will be connected to a series of similar units to create a
much bigger system.
A)
Mono-Block Design: The mono-block manifolds are further subdivided into laminar
and drilled metal blocks. Laminar manifolds are generally made from steel with
passages created by milling through multiple metal layers. These metal plates
are stacked one above the other with fluid paths between them. Finally,
solid-metal pieces are added, and the entire stack is brazed into a single
unit. Now, these manifolds are capable of tolerating high pressures of up to
10,000 psi. The internal passages may be created in any required shape, so
almost any flow-rate can be maintained with negligible drop in pressure. In a
laminar manifold, all connections including the values can be placed anywhere
you need, depending on your application. However, due to their brazed
construction and their permanently-shaped flow passages, this type of manifolds
are not easily modifiable if any circuit changes are required in future.
Drilled metal blocks are created from bars or plates made of aluminium, ductile
iron and steel. It is quite obvious from their name that they are formed by
drilling metal blocks in order to create flow passages and circuit paths. You
may place the valves anywhere you please, however the drilled passages should
always be straight. Other types of drilled-block manifolds accommodate
cartridge valves into the cavities drilled deep into the surface of the
manifold. In such a case, several interconnecting flow-passages start from the
valve cavities and run into the manifold. Some cartridge valves comprise of
threaded bodies which hold them in place within threaded cavities while others
slip inside smooth cavities in which they're held by plates.
B)
Modular Block Design: The modular manifold systems can easily be modified or
attached to other existing manifolds. They're typically made of steel, aluminum
and ductile iron and are available in both standard and custom designs. The
ends of these manifold blocks are sealed with "end pates" which can
be drilled further for tank or pump connections. In addition, the spacer,
interconnecting and divider plates are installed within the basic building
blocks. Spacer plates can increase the dimensions of the basic blocks so that
an over-sized valve can be inserted. The interconnecting plates divert the flow
of the fluid from one passage to another between the blocks. They also serve in
stopping the flow between two blocks by stopping a passage. The divider plates
facilitate or block the flow by plugging. The top portion of a basic modular manifold block is drilled and ported
to accommodate subplate-mounted valves. Also, blocks with multiple ports are
available for every type of sub-plate and valve. Each type is uniquely
identified by the valve it can accept. Few mounted systems accept both
cartridge valves and sub-plate mounted valves. Whenever you specify a manifold
system, the interchangeability of blocks, subplates and valves should be
considered carefully. The electrical connections to manifolds are created using
wires that run directly from the power source to the respective solenoid. Many
manifold systems have inbuilt electrical channels or troughs for interior
arrangement of electric cables. Since there is a diverse range of
configurations available for manifold design, multiple software packages have
been created to help the engineers in designing a manifold system. With
advancements in the design software and the CNC technology, the manufacturing
cost of custom mono-block or modular manifolds, even in less number, is quite
reasonable.
Things
To Keep In Ming When Choosing A Manifold: 1. What fluid is used?
2. Seal materials 3. Duty cycle 4. Electrical connections and voltage 5.
Maximum and working pressure 6. Material and finish 7. Operating temperature
and environmental factors 8. Flow conditions such as pump, return and
accumulator 9, The location, size and type of the ports 10. Type of/Number of
valves 11. Mounting
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