Stopping a pneumatic cylinder in emergency situations or during regular operations is essential to machine safety. Although there are many ways to solve this challenging application, stopping the flow of compressed air using an air circuit combined with a mechanical locking cylinder gives the most enhanced level of safety.
The energy in compressed air can be controlled and directed by solenoid valves to produce cylinder motion, but it can also be harnessed to abruptly stop cylinder motion.
The common way to stop cylinder motion is to direct the compressed air through a three-position, spring return, centre closed solenoid valve to trap the pressurised air on both sides of a cylinder in an e-stop situation. When electrical power is interrupted purposefully (e-stop), or accidentally, the spring return function will position the valve back to the centre, trapping the pressurised air and thus halting all motion.
Although stopping a cylinder with a pneumatic circuit can be highly effective, this method alone is not recommended for maintaining the cylinder in its stopped position, especially when it is bearing a heavy vertical load.
The primary reasons for not solely relying on a three-position, centre closed valve for holding cylinder position include:
• Risk of air leaking from the seals of the valve’s outlet ports.
• Risk of air leaking from the seals of the valve’s spools.
• Risk of the spring force not holding the valve in the centre closed position.
• Risk of cylinder drift caused by the area differential on the piston extend side vs. the retract side.
• Risk of air leaks from the overall system (fittings, tubing etc.)
All of these risks can be mitigated by adding a mechanical rod lock to the cylinder.
Locking cylinders come in two types: locking type or end lock of the rod at extension or retraction; and a braking type or fine lock, where the piston rod can stop and maintain a position at mid stroke. Both types of locking mechanisms can be activated by either applying or removing pressurised air from the braking unit.
Some common applications for locking or braking cylinders are:
• Press, clamping or holding a cylinder position for welding, drilling, etc.
• Stopping a cylinder to maintain a safety zone during repairs.
• Holding a static load.
• Drop prevention.
• Emergency stop.
Note: Installing a pressure regulator and flow controls to balance the air pressure for the circuit to adjust for piston area differential is also recommended when using an end lock or fine lock cylinder.
Driving heavy equipment industry
Motion Control & Drives
Cimolai Technology, a leader in the design, production and installation of lifting and handling equipment, has adopted the Siemens Xcelerator portfolio of industry software. This move aims to deliver innovative, reliable and custom-made solutions to meet the most demanding technical specifications across sectors such as shipyards, infrastructure and heavy industry.
Read more...AG Lubricants partners with
Motion Control & Drives
AG Lubricants has partnered with a major player in the South African steel industry to supply high-performance Mobil lubricants, Quaker Houghton industrial fluids and value-added technical services.
Read more...Smart features increase crane safety
Motion Control & Drives
The newly launched Konecranes S series hoist offers a large bouquet of smart features which not only increase lifting device safety but also deliver a higher level of operator protection.
Read more...Compact, powerful hexapod for high-precision applications
Motion Control & Drives
With the HEX150-125HL, Aerotech is launching the latest generation of its hexapod technology. The compact six-axis positioner combines precise movements with high load capacity and simple integration.
Read more...Hexagon Electrical services electric motor sector
Motion Control & Drives
Hexagon Electrical has expanded its manufacturing and service capabilities to meet the growing demand for customised, high-performance specialised electric motors in heavy engineering, and hazardous industrial and mining applications.
Read more...NORD modular drives for frequently changing motor speeds Bearing Man Group t/a BMG
Motion Control & Drives
BMG has made a substantial investment over the years to ensure assembly, stockholdings and technical support for the Nord range are in line with stringent international quality, safety and environmental standards.
Read more...Medium voltage drive for enhanced energy efficiency and process optimisation Schneider Electric South Africa
Motion Control & Drives
Schneider Electric South Africa has unveiled its cutting-edge Altivar Process ATV6100 medium voltage (MV) drive range, designed to enhance energy efficiency and operational reliability across various industries.
Read more...Powerful high-precision hexapod
Motion Control & Drives
With the HEX150-125HL, Aerotech is launching the latest generation of its hexapod technology. The compact six-axis positioner combines precise movements with high load capacity and simple integration.
While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.