Often when an internal combustion engine is used on mobile hydraulic equipment a problem occurs where an hydraulic pump is asked to deliver full system pressure while the engine speed is low.
If the engine speed is below the speed range of the pump, then the internal slip may be greater than the discharge and the pump will fail to deliver hydraulic oil. This is not an unusual occurrence and the problem worsens as the pump wears. Because there is no pump output, rapid localised heating occurs within the pump and external temperature safety devices, which are usually located in the reservoir, do not detect this overheating. Pumps subjected to these conditions are soon destroyed.
Sun Hydraulics has come up with a solution to this problem: a valve that 'senses' engine speed and acts as a relief valve on an unloading valve.
In its basic form (see Figure 1) the valve works by responding to differential pressure across a fixed orifice. This pressure differential is proportional to flow, which is in turn related to engine speed.
Figure 1. Low idle valve for pump protection
At low pump flow the unloading valve remains open and hydraulic fluid is returned to the reservoir. With fixed displacement pumps as flow (engine speed) increases the pressure across the orifice increases, until, at a predetermined pressure, the unloading valve closes (stops by-passing) and hydraulic fluid flows to the load. Should speed drop below the setpoint for any reason then the valve will cut out (start by-passing) giving free circulation for the oil and preventing damage to the pump.
The same technique can be used in conjunction with a differential pressure sensing valve for accumulator unloading (see Figure 2).
Figure 2. Low idle valve with differential pressure sensing valve for accumulator unloading
In many cases a cheaper gear or vane pump can be used in place of a piston pump. No matter which pump is chosen this valve will prolong its life. There are four sizes of low idle valve available covering flows from 0 to 280 litres per minute.
This valve with its unique features saves users maintenance costs and enhances the life of hydraulic pumps.
Oil-free beer and wine processing
Pneumatic systems & components Hydraulic systems & components
The food and beverage industry depends on superior quality, 100% oil-free compressed air to eliminate the presence of unwanted oil vapour throughout the production line.
Read more...Extending the life of hydraulic cylinders and hoses
Hydraulic systems & components
Hose saver protection sleeves extend the life of hydraulic and pneumatic hoses by eliminating unnecessary expenses from downtime, oil loss, contamination, and replacement hoses.
Read more...Hydraulic connectors with residual pressure
Editor's Choice Hydraulic systems & components
Hydraulic connections are vital in both outdoor and indoor industrial machinery. However, the hydraulics lines frequently require connecting and disconnecting for maintenance or changeover. The goal is to enable quick, easy swaps to enhance machine flexibility and productivity.
Read more...Sun carries the load Axiom Hydraulics
Hydraulic systems & components
When valuable lives are hoisted in the air, reliable load holding technology is at its utmost importance. That’s why you can count on Sun’s excellent load holding cartridge valves.
Read more...How to protect against water hammer SA Gauge
Editor's Choice Hydraulic systems & components
Water hammer is a high-pressure surge or wave created by the kinetic energy of moving fluid when it is rapidly forced to stop or change direction, altering the liquid’s velocity. The progression of the water hammer shockwave needs to be detained and slowed before reaching the instrument sensor. SA Gauge manufactures several such devices in order to achieve this.
Read more...Axiom ups its game Axiom Hydraulics
Editor's Choice Hydraulic systems & components
In today’s competitive market, manufacturers of hydraulic components are constantly challenged to find better, faster and cheaper ways of producing parts. Axiom Hydraulics has met the challenge, and can now deliver a product with superior performance and significant cost savings for its customers.
Read more...Condition monitoring for critical hydraulic equipment Hydrasales
Hydraulic systems & components
Systems maintenance personnel often classify equipment as critical, based solely on its value. Instead, critical equipment should be determined by its importance to the operation and the objectives of the organisation.
Read more...Hydraulic bolt tensioning Bearing Man Group T/A BMG
Hydraulic systems & components
BMG’s Nord-Lock bolting solutions include Boltight hydraulic bolt tensioning tools, which can be used to tighten bolts simultaneously, ensuring even preload in industrial applications and extreme environments, ...
Read more...How to get the best of both worlds with hydraulics and electric
Editor's Choice Hydraulic systems & components
While battery technologies continue to evolve and overcome challenges that have previously restricted more rapid electrification adoption rates, hybrid electric systems are well positioned as an ideal interim solution.
Read more...Create and recover energy all in one check valve Axiom Hydraulics
Hydraulic systems & components
Energen is a new, high-efficiency check valve from Sun Hydraulics that allows free flow from inlet to outlet, and blocks flow in the opposite direction. Composed of an integrated generator that converts ...
printer friendly version