User information
Why hydraulics ?
Hydraulics is the kind of power transmission which allows the
greatest density of forces. There is no other kind of power
transmission that will transmit comparable high forces with
the same construction size.
Hydraulic tools
Hydraulic tools are a special type of powered tools, which can
be used for general assembly and repair jobs with preferably
high force in lowest space. Simple application, clearness of
the programme in line with robustness, short deliveries and
universal operation possibilities have made hydraulic components
indispensable tools also for elaborate applications, e.g. mounting
of machines, where hydraulic cylinders, hand and motor pumps
exert special functions: e.g. installation in machines, where
hydraulic cylinders, manual and motor pumps perform special
functions, mounting to appliances and tools for spanning, installing,
pressing, border crimping, cutting, riveting, extraction of
tubes etc. as well as assembly of frame presses and lifting
devices.
How to reach high forces in hydraulics?
Linear conversion of pressure force
The above formula shows that pressure forces can be converted
linearly.
Example: A 10 ton cylinder presses at:
700 bar - 100 kN = 10 t
350 bar - 50 kN = 5 t
100 bar - 14 kN = 1.4 t
1 bar - 0.14 kN = 0.014 t
Basic terms in hydraulics
Pressure
is the system pressure generated by the pump, which, however,
can also be produced from an external power source, which acts
on the hydraulic cylinder.
Force
is always the pressure transferred by the hydraulic cylinder
(only with counterpressure).
Stroke
is the travel distance to be achieved by the force (noload stroke,
loaded stroke, return stroke).
Piston travel speed
Is the time, in which the piston of the hydraulic cylinder is
to pass a certain travel distance (stroke) (no-load stroke +
loaded stroke, return stroke).
Hydraulic cylinders
are available in most different designs, however, with only
two basic function principles:
Hydraulic hand pumps
The
function of a hydraulic hand pump is to convey hydraulic oil
(no-load stroke) and to generate pressure, which will be converted
by the hydraulic cylinder into force (loaded stroke). Hydraulic
hand pumps are independent from energy and can be used in everyday
applications. They are easily portable and render an extremely
high power generation in connection with a corresponding hydraulic
cylinder.
Hand pumps
require certain manpower and are often replaced by motor pumps
in case of permanent duty and high oil quantities respectively.
Hand pumps are distinguished by:
1. oil displacement volume (1st stage /2nd stage)
2. the function of the hydraulic cylinder: single-acting /double-acting
Motor pumps
transmit an oil flow as soon as the pump unit is driven by the
electric motor. Contrary to hand pumps, the oil flow is also
available when the hydraulic cylinder is not activated (e.g.
during work breaks).
Hydraulic valves
Valves are used in hydraulics to control the oil flow (generated
by either hand or motor pump) in terms of direction, pressure
and oil volume.
Directional valves
are required to control the direction of the oil flow and thus
the work motions of the connected hydraulic cylinder (advance
– stop – retract).
Depending on the type of pump and cylinder, 2-, 3- or 4-way
valves may be employed:
3/3-way valves for single-acting cylinders
4/3-way valves for double-acting cylinders
Controls are available with either manual or electromagnetic
valves (the latter with remote cable control).
Pressure valves
are employed to limit the system pressure in a hydraulic system
or within a part of the oil circuit. Pressure valves or pressure
relief valves are also installed as safety devices in order
to avoid excessive increase of the system pressure beyond a
given value.
Shut-off and throttle valves
are used to easily shut-off hydraulic lines by hand. On account
of their sensible control mode, these valves can also be applied
to throttle an oil flow and thus to control the piston advance
at both lifting or lowering of the load.
Safety-check valves
are used for those applications where pressure drops must be
avoided.
Pressure switch
can be set to any pressure value in order to switch on/off parts
of the hydraulic circuit.
For your safety
Hydraulic units are extremely robust and durable. Nevertheless
you should observe the following hints for your own safety and
to increase the life expectance of the product:
- Never exceed the max. pressure (capacity) of the hydraulic
units.
- Avoid eccentric loading of the piston.
- The load must always be positioned centric and parallel on
the piston. Avoid point loading.
- Never pass under a raised load, if this is not supported additionally.
- Hydraulic units must be kept clear of heat (e.g. during welding).
- Protect hydraulic hoses against damages and too strong kinks.
Hydraulic hoses should lie freely in a wide curve. Avoid tensile
load.
Eccentric loading
In order
to obtain long life endurance, hydraulic cylinders series YS,
YLS, YFS, YCS, YCH, YH, and YPL are manufactured from chromium-molybdenum
steel, the cylinder housings and piston rods are hardened and
tempered and provided with bronze guides.
Generally,
hydraulic cylinders should not be loaded eccentrically, as this
can lead to reduced lifetime. In practice a lateral loading
cannot be fully avoided. In this case the maximum system pressure
and the stroke of the cylinder should only be used by 50 %.
Ensure that the load always rests on the total area of the steel
saddle and the piston respectively. Also ensure that the entire
bottom area of the hydraulic cylinder always stands on a level,
sustainable ground surface. This applies especially to flat
cylinders!
Repairs
Repair and maintenance should be accomplished by competent people
only. Make sure to use original spare parts only!
Hydraulic
cylinders with Yale ChroMo-Design
Yale hydraulic tools are designed for professional operation.
A tool is only as good as its basic material.
Therefore, our cylinders are manufactured from high quality
chromium-molybdenum steel and are heat treated.
Double bronze bearings
Practice has shown that hydraulic cylinders used as a tool in
workshops or on construction sites are frequently subjected
to eccentric loading. Yale hydraulic cylinders are provided
with double bronze bearings on the plunger, which minimizes
friction between plunger and body during lateral loading.
Hard chromium-plated piston
Offers excellent protection against mechanical damage and corrosion.
Excellent sliding characteristics in conjunction with the upper
bronze bearing in the stop ring.
Metric mounting threads and standard parts
To facilitate the installation of hydraulic cylinders in jigs
and fixtures and auxiliary structures. The metric standard throughout
the entire series simplifies service operations and repairs.
Cylinders carries the full load even under maximum operating
pressure.
Stop ring carries full pressure
As a safety factor the stop ring on all Yale hydraulic cylinders
carries the full load even under maximum operating pressure.
Delivered ready to use
Yale Hydraulic cylinders are delivered ready to use incl. female
coupler half, hardened saddle and mounting threads; larger cylinders
come with carrying handle or transportation lugs. This also
applies to customised combinations which are always supplied
ready assembled.
Hand pumps 700 bar
Build-up and description
of the Yale hand pumps
Hand pumps are the most common power source within the area
of "High Pressure Hydraulic Tools". For this reason
our hand pumps have been carefully designed and equipped with
many details which make the pumps very versatile and handy in
every-day applications.
Relief valve/hand wheel
The fine adjustment relief valve in connection with the large
hand wheel allows by millimeter increments lifting and lowering
even of the highest loads. The fact that sometimes hundreds
of tons are controlled by this hand wheel, underlines the importance
of this detail.
Sturdy "all-metal-design"
The robust pump head and the adsence of any plastic parts result
in long service life and easy maintenance over many years. Plastic
reservoirs filled with oil can represent a fire danger in connection
with welding or similar work.
Carrying handle
A handy carrying handle on all our hand pumps eases the transportation
enormously.
Pressure relief valves
All Yale hand pumps are equipped with two pressure relief valves.
They are easily adjustable from outside in those cases where
pumps must be re-adjusted or a lower operating pressure should
not be exceeded.
Reservoir ventilation
All hand pumps are equipped with a reservoir ventilation plug.
This ensures perfect suction of hydraulic oil and allows you
to use the total oil capacity of the reservoir.
Two-stage output
All Yale hand pumps have two-stage design (except HPS-1/0.7).
This allows an increased speed and efficient working during
unloaded conditions of the hydraulic cylinder. The switch-over
from the low pressure to the high pressure stage is done automatically.
Delivered ready to use
All Yale hand pumps are supplied ready to use incl. hydraulic
oil.
Easy-maintenance-design
There is no need to disassemble the Yale hand pumps in case
of service work. All parts like suction and pressure valves,
seals, packings etc. are accessible from the outside.
All hand pumps have the same design
The same design (build-up) for all Yale hand pumps with the
exception of the reservoirs allows the interchangeability of
all components. Therefore spare part stocks can be kept to an
absolute minimum. Only one spare part kit is necessary to service
all hand pumps.
Excellent suction properties
Yale hand pumps suck and displace 100 % of their volume per
stroke. This results both in a high efficiency as well as a
rapid cylinder movement.
Interchangeability
All Yale hydraulic cylinders, hand pumps and other components
are fully interchangeable and can be combined with all other
700 bar hydraulic lines. All components have the standard oil
port and same coupler parts.
Additional return oil port
All Yale hand pumps are equipped with a return port to the reservoir.
This detail is very advantageous as many hand pumps are integrated
in more complex hydraulic circuits.
Base frame
On request you can get base frames for the most common hand
pumps. These base frames add to the stability and protection
of the hand pumps, in particular when used in the field or on
a construction site.
Pressure gauge
Appropriate pressure gauges with the corresponding adaptors
are shown.
Hand pumps for double-acting cylinders
with relief valve and 4/2-way directional valve
Unlike conventional pumps, all Yale hand pumps of the type HPH
(with 4/2-way directional valve for double-acting cylinders)
include a precision relief valve in addition to the directional
control valve.
Manual directional control valves switch over abruptly, thus
causing undesired pressure surges in the system under load.
The additional relief valve in all HPH-hand pumps allows a precise
lowering of the load without any pressure shocks. All components
have the standard oil port and same coupler parts.
Further advantage of this design:
The pressure gauge shows the pressure as pushing and as pulling
force. The combination of a 4-way directional valve with a sensitive
relief valve allows a controlled pressure relief without pressure
shocks.
