Product category:
Hydraulic Components
News Release from: Integrated Hydraulics | Subject: PFR24A
Edited by the Engineeringtalk Editorial
Team on 25 October 2005
Valve promises pressure compensated flow
control
A new proportional flow control valve gives engineers reliable, accurate and affordable pressure compensated proportional flow control.
A new proportional flow control valve that gives engineers reliable, accurate and affordable pressure compensated proportional flow control has been introduced by Integrated Hydraulics This new small, simple, valve complements the company's proportional pressure compensated flow control circuits and other proportional and manually operated cartridges
It is designed to give pressure compensated flow control for flows up to 28 litre/min, working at 210bar.
The valve makes innovative use of flow forces within the spool to achieve a fine level of pressure compensation in a very simple and cost effective cartridge.
The new PFR24A proportional flow control valve has a simple two-port spool-type design and makes use of tried and tested components and technology.
With no current applied, the spool blocks the ring of holes in the nose of the cartridge, preventing flow to the outlet port.
As the current increases the increasing solenoid force acts on the spool to open it against the force of the spring, progressively uncovering the radial holes and permitting flow through the valve.
If downstream pressure should fall, the flow rate would increase, but, due to some clever detail design, the increase in flow reduces the pressure behind the spool.
The resulting pressure imbalance on either end of the spool creates a force that is added to the force of the spring, against which the solenoid is acting.
This change in forces causes the spool to shift, restricting the flow path through the radial holes, thus maintaining near constant flow for any given input signal.
Varying the current will alter the force applied to the spool and hence the flow through the valve.
These valves compensate in both directions and are ideal for use as bleed off valves in systems using a fixed pump, providing proportional flow control at working pressure instead of full system pressure.
The valve has an hysteresis of better than 4% with PWM at a cycle rate of 200-400Hz and 6% without PWM.
It benefits from having no dynamic seals, which reduces hysteresis and prolongs service life.
Response time is 300ms and internal leakage 200ml/min.
For systems requiring lower leakage, Integrated Hydraulics has developed a proportional poppet type flow control valve that gives an internal leakage of just 0.7ml/min.
The armature is oil immersed and the coil/stem sealed to avoid atmospheric corrosion.
Installation and commissioning costs are minimised as a manual override is provided to help setup (and to operate the valve in the event of power failure).
Also, an innovative feature is the addition of an air bleed valve on the solenoid tube of the cartridge which greatly assists in the initial commissioning of the system.
Air trapped in the tube can cause instability and a reduction in the performance of proportional valves.
The coil is interchangeable with those used on Integrated Hydraulics S5 Series valves, reducing spares inventory and it uses one of their standard cavities so no new tooling is required both of which reduce the overall cost of using the product.
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