Flow control advances
20 March 2012
Suzanne Gill takes a look at some of the latest technology developments in the area of flow control and, importantly finds out more about the benefits being offered by new valves and actuators being introduced to the market.
A new check valve design incorporates a hydrodynamically optimised valve cone to minimise pressure loss and increase flow by 25%
The prevention of failure-free backflow of media has, traditionally, presented a challenge for check valves in many chemical processing applications as valves in such applications are often subjected to extreme wear because of the mechanical and chemical stresses.
We are told that a new generation of check valves, from GF Piping Systems, part of the Georg Fischer group, will eliminate this problem. Development of the valves focused on how wear and tear of the valves’ moving parts could be minimised, leading the company to redesign the interior of the valve.
Two years before bringing the product to market, GF Piping Systems offered prototypes of the check valves, in a variety of versions, to a customer in the chemical process industry for field-testing in its effluent neutralisation process. The company needed a solution to reduce the amount of wear to its check valves which is caused by mechanical stress because of high flow velocities, water hammer in the pipeline and chemical attack on the valve components.
The resulting valve design incorporated a hydrodynamically optimised valve cone to minimise pressure loss and at the same time increase flow by 25% compared to the previous generation offered by the company. Another effect of the new cone contour is that the valve can be equipped with a return spring and thus implemented in new applications. Equipped with a return spring, the check valve can be installed in nearly any position, horizontal or vertical.
The elastomer seals also contribute to reliability of the valve and an optimised the seal profile is said to guarantee leak-tightness. The profile of the cone surface that comes into contact with the sealing ring is spherical making it completely leakproof if there is a slight deflection of the cone, ultimately protecting the pump from backflow of the process medium.
Closing the control loop
Ball valves are widely used in process applications for their full flow capabilities and because of their ability to be used with high viscosity fluids, and at high temperatures and pressures.
A new ball valve with actuator and positioner combinations, from Bürkert, is said to ‘close the control loop’. The range consists of 2/2 stainless steel ball valves, available manual or complete with quarter turn single or double acting rotary actuators which have optical position indicators, mechanical feedback and pilot valve connections for NAMUR pilot valves, or Bürkert side control positioners.
Commenting on the new 2652 and 2655 units, Neil Saunders, sales manager for Bürkert UK, said: “Our ball valve/actuator/positioner combination provides process users with a compact modular system for fluid control at a competitive cost.”
Complementing units for more precise valve operation is a low-cost IP65/67 rated positioner which can be mounted in various orientations to linear and rotary actuators, according to IEC534-6 and VDI/VDE 3845 (Namur), as well as to Bürkert process valves.
Increased data rates
Modbus looped capabilities have been available on AUMA electric actuators for over five years, but recent advances to the system are said to triple the maximum possible data transfer rate, and significantly reduce the time of actuators in the feedback loop, which helps to improve the systems overall response time.
The latest system comprises a SIMA master station, which helps to integrate actuators into the automation environment, managing the communications for up to 247 actuators. The solution is capable of supporting looped conventional copper cable lengths of up to 290km and uses the Modbus RTU protocol based on RS-485.
Additionally, if the redundant loop is interrupted, data communication to all installed actuators is maintained without any restrictions. An automatic feature for commissioning the new system is able to reduce start-up times and configuration errors.
When the SIMA master station is switched on after completion of the wiring, it can determine the number of actuators connected and automatically assign addresses of the slave actuators and set the desired baud rate. This negates the need for manual setting of the communication parameters at each actuator, offering time-savings during the commissioning phase.
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