Valves Resist wear and tear
The Inflatek Valve from MacTenn is a new concept in valve design which offers remarkable reliability and wear resistance
The Inflatek Valve is a valve concept which has been proven to demonstrate remarkable characteristics of reliability and wear resistance operating with abrasive bulk materials and pressure differentials.
The valve was developed in the 70s and registered at the United States patent office. It incorporates a unique seat sealing method. The valve seat is a flexible and inflatable heavy membrane which is designed to entrap particles at the seat, to prevent their movement under the influence of a pressure differential, and therefore overcome the main cause of wear in valves handling bulk materials or dirty gases containing particulate.
Although the valve introduces a relatively new concept in seat sealing technique, it has been widely applied in many industries. The manufacturer claims 20,000 installations throughout the world since its introduction to North-America in 1978 in diverse applications such as controlling filling of pressure vessels with hot bottom ash at 650°C and supporting a pressure differential of 6 bar, to controlling filling of a pressure/vacuum chamber with magnesium powder.
Many applications of the Inflatek Valve are in retrofit situations where conventional valves have failed to provide reliable operation in pressure differential applications. This is typical of situations in which closing member design or seat design allows particulate movement across the seat face to cause accelerated wear. This is a situation common to conventional valves applied beyond their application ability normally for reasons of first cost economy.
Valve design objectives
The valve was designed to achieve two main objectives: • To provide minimal or no seat wear when handling abrasive bulk materials, and a closing action to support a pressure differential. • To provide a closing and sealing action in one motion through a static or moving column of bulk materials.
Subsequent development of the valve allowed additional objectives to be achieved which were:
• Achieve the above objectives when operating in applications at a constant temperature of 350°C.
• Achieve the above objectives when operating with both pressure and vacuum differentials in the same operating cycle. • Provide a snap-open characteristic to the closing member of the valve for high gas pressure exhaust applications • Flow regulation with auto-positioning capability in addition to flow stop requirements.
Additional design objectives relating to valve performance and practical considerations were incorporated:
www.solidsandbulk.co.uk Fig. 1 November 2010 • Solids & Bulk Handling 41
• Unrestricted flow through the valve when in the open position.
• Easy inspection and maintenance.
• Open choice of valve operators for any valve application. • Wide range of construction materials for media compatibility. • Wide range of seal membrane materials for media compatibility. • Very low maintenance costs. The main components of the valve, i.e., dome casting, top plate, do not require replacement or repair for several years. The inflatable seal is often only replaced once per year, or every two years, and is a low cost item.
During its first few years of introduction, the Inflatek Valve was exclusively applied to high pressure pneumatic conveying systems in which the majority of materials handled were abrasive, such as coke breeze, lump coal or sand, and in which pressure differentials were up to 7 bar. Recently the valve began to see application opportunities within the general valve market where the evident superior ability of the sealing technique became noticed.
General applications in the chemical processing industry have subsequently caused the latter design objectives to be adopted with consequent strengthening of application capability.
Valve design
The valve design is a masterpiece of simplicity. The closing member is a segment of a sphere (dome) with extended arms mounted to shafts (see Fig. 1). The shaft is driven 90° by an actuator which allows the crank-mounted dome to rotate entirely away from the inlet port of the valve body. Passage through the valve is therefore totally unobstructed.
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