Knife gate valves ensure trouble free control
May 2003
Valves, Actuators & Pump Control
Selecting the correct valve for control applications normally poses many challenges to control engineers. In applications where fluid media with a significant solid content is difficult to control with conventional valve designs - operational problems, maintenance and service life require thorough consideration.
Helping to ensure that technologically advanced, quality products are available to meet the demands of control engineers is the Control Division of DLM. "We identified that the southern African market was in need of a cost effective knife gate valve that would provide years of trouble-free and maintenance-free operation even under the most severe service applications", says DLM's Control Division director Marc von Ruben. "Worldwide research into available products lead us to Vaas Industries, an organisation with capability to design, manufacture and test one of the widest ranges of knife gate valves internationally.
"Vaas knife gate valves were developed to cater to specific services where conventional valve designs proved to be inadequate. For instance, fluid media with significant solid content is generally difficult to handle with conventional valve designs such as gate, globe, ball, plug or butterfly valves. We therefore decided to enhance our extensive product range by the addition of this excellent valve."
Vaas knife gate valves from DLM
Vaas knife gate valves are designed to ensure minimum contact between moving parts of the valve. The gate is held between strong layers of gland packing and does not contact the body until it actually seats. The seating is accomplished with a non-sliding motion of the gate towards the body (seat) aided by jams located in the body. Avoiding sliding contact between gate and body permits this valve to handle abrasive particles present in the media more effectively than conventional designs.
The knife gate valve is a unidirectional low-pressure valve ranging in size from 50 mm to 1200 mm with pressure ratings up to 1 MPa (10 bar). Modifications that offer bi-directional shut-off are also available.
The bevelled bottom edge of the gate (from which it derives the 'knife' in its name) allows positive closure of the gate even when solid particles have settled at the bottom of the body. Deflection cones are used to avoid direct impingement of abrasive media on the seat surfaces, which themselves are hardened by either stelliting the seat/gate or nitride coating the entire body and gate.
The purge connection feature allows suitable fluids at pressures higher than line pressure to clean seating surfaces (body purges) and packing area (chest purges), minimising abrasive wear and tear during valve opening and closure.
Knife gate valves are normally round-port designs, however, square and rectangular port variants are also available which are typically used in hopper isolation applications. This is the only valve design that tolerates differential thermal expansion of its parts without affecting its functionality, thus making the Vaas knife valve an ideal choice for high temperature media.
Another variation is the v-orifice design that offers a compromise between controllability and capability to handle media containing solids such as sludges or slurries. Vaas knife gate valve design variations include two-lug, full lug wafer and flanged designs; metal-to-metal and resilient seat options; v-orifice, square and rectangular port designs; options such as purges and deflection cone; choice of manual, pneumatic, electric and hydraulic actuators. With the correct selection and installation process, the Vaas knife gate valves will provide long service life and maintenance-free operation even in the most difficult service situations.
For more information contact Marc von Ruben, DLM, 011 457 0500, [email protected], www.dlm.co.za
Further reading:
High-flow solenoid valve
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson has introduced the new ASCO Series 327C solenoid valve, which features a direct-acting, high-flow design that provides superior flow-to-power ratio. It permits high flows at minimum power levels, making it ideal for use in power plants, refineries, and chemical processing facilities.
Read more...
Proportional cartridge valve series is the fastest in its class
Valves, Actuators & Pump Control
Parker Hannifin is introducing the enhanced version of the proportional cartridge throttle valve series, TFP. The new pilot valve further reduces the step response times by up to 30%, making the TFP the fastest valve in its class.
Read more...
Proportional cartridge valve series is the fastest in its class
Valves, Actuators & Pump Control
Parker Hannifin is introducing the enhanced version of the proportional cartridge throttle valve series, TFP. The new pilot valve further reduces the step response times by up to 30%, making the TFP the fastest valve in its class.
Read more...
Inspection system for leak detection in valves in hazardous areas
Extech Safety Systems
Valves, Actuators & Pump Control
Leaking valves in industrial plants not only lead to loss, safety risks and possible contamination and pollution, but also result in high economic costs. Therefore, valves in hazardous areas require regular proper inspection and preventive maintenance to ensure their functionality.
Read more...
Control head for automation of hygienic process valves
Burkert South Africa
Valves, Actuators & Pump Control
Burkert’s Type 8681 control head is optimised for decentralised automation of hygienic process valves. Thanks to its universal adapter, it can be combined with all normal commercial butterfly valves, ball valves and single- and double-seated valves.
Read more...
Hydroformed tube valve body
Burkert South Africa
Valves, Actuators & Pump Control
One of the most common necessities for manufacturing pharmaceuticals, cosmetics, food and beverages are diaphragm valves. What used to be a dull two-way race between forged and cast body variants is now being challenged by an exciting, ground-breaking technology. The hydroformed, light-weight diaphragm tube valve body will change the way you think about plant design and operation.
Read more...
Global pumping giant ready to support hydrogen economy
Valves, Actuators & Pump Control
With abundant sunshine and wind, southern Africa is perfectly positioned to become a global powerhouse in green hydrogen production. Two key projects are already in advanced stages of development in Namibia. KSB has identified the vast potential of these types of projects in southern Africa, and through its KSB Pumps and Valves subsidiaries in Namibia and South Africa is investing heavily in bringing the right skills to the region.
Read more...
Compact valve position indicator
Emerson Automation Solutions
Valves, Actuators & Pump Control
Emerson’s new TopWorx DVR Switchbox is an entry-level addition to the DV Series of valve position indicators. It combines a durable resin enclosure, compact size, and a patented cam design that provides a reliable valve position feedback for water and wastewater systems, food and beverage production lines, and industrial utilities.
Read more...
Precision, control and performance in regulators and control valves
Valve & Automation
Valves, Actuators & Pump Control
Cashco has long been a trusted name in industrial control solutions, offering a broad range of regulators and control valves designed to meet the rigorous demands of various industries. There are two key Cashco product lines, its regulators and the Ranger QCT control valve.
Read more...
Advanced solutions for valves
Bearing Man Group t/a BMG
Valves, Actuators & Pump Control
BMG delivers state-of-the-art valve solutions to diverse industries across Africa, in collaboration with InterApp, a global leader in the design and manufacture of high-quality valves.
Read more...
printer friendly version