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Holmbury Ltd, markets a wide range of hydraulic couplings,
predominantly at sizes from 1/4" to 2". Used primarily to connect
two sections of flexible hydraulic hose, or flexible hose to solid pipe,
they will nevertheless have to meet highly specific yet vastly different
sets of criteria for each application. For example, consider the two
applications below.
Excavators - Construction Industry
The hydraulic couplings used on excavators will need to be
moderately corrosion resistant, since they will operate outdoors in all
weathers. Zinc plated carbon steel construction is the norm. Internally, the
seal materials will need to be suitable for operation on a hydraulic grade
of mineral oil. When the hydraulic couplings are disconnected, there should
be no loss of hydraulic oil to the environment. They should also be robust
enough to survive the rough treatment they are likely to encounter on
construction sites. Finally, and most important of all, hydraulic couplings
on excavators must be able to withstand high pressure pulses. Breaker
attachments on excavators put shock waves into the system that can severely
damage the hydraulic couplings. (For anyone not familiar with the term
'breaker' in the context of an excavator, it is rather like a large
pneumatic drills mounted on the excavator arm, however, it is powered from
the machine's hydraulic circuit not an air compressor).
Pharmaceutical Industries
In complete contrast to excavators, hydraulic couplings
for the pharmaceutical industry will normally have to be made in stainless
steel, either for reasons of hygiene and / or corrosion resistance in
aggressive environments. The internal components and seals may also have to
be selected carefully if the hydraulic couplings are required to transmit a
corrosive fluid. High pressure pulses are rarely an issue and so the
coupling mechanism does not have to be so robust.
Whatever your application, whether it's general
industrial, construction plant, agricultural equipment, sub-sea, renewal
energy, railways, etc., Holmbury will be able to give advice on the best
hydraulic couplings for your requirements.
Hydraulic Couplings - The Basic Types
- Flat Face hydraulic couplings - where possible,
Holmbury recommends that preference be given to products that conform to
ISO 16028.
Advantages: Flat faces are easily wiped clean to help prevent the
ingress of contaminants. Construction is normally more robust to
withstand high pressure pulses.
Disadvantages: Initial cost is higher than non-flat face
hydraulic couplings. However, when the lifetime cost of a machine is
calculated, flat face hydraulic couplings will normally show a saving,
especially when machine downtime and lost production is taken into
account.
- ISO.A hydraulic couplings - a ubiquitous coupling,
produced in vast quantities and available worldwide.
Advantages: Low initial purchase cost. Well proven design with
good track record. Ideal for non-demanding applications.
Disadvantages: a small quantity of fluid is lost on
disconnection. Not designed to resist high pressure pulses.
- Screw Connect Hydraulic Couplings - available in flat
and non-flat face designs.
Advantages: Can provide a more secure coupling than the quick
connect / quick disconnect flat face and ISO.A hydraulic couplings. Can
(in many instances) be connected whilst there is residual pressure in
the hose line. Can resist high pressure pulses.
Disadvantages: Slower to connect and disconnect and will usually need
spanners to nip tight in order to prevent the coupling unscrewing with
machine vibration.
- Other types of hydraulic coupling include ISO.B and
Connect-under-pressure.
For further information on hydraulic couplings call the
Holmbury Technical Department.
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