Safety shut-off valves for the oil and petrochemical industries
September 2003
Valves, Actuators & Pump Control
Training & Education
The Maxon Corporation of the USA is a primary supplier of safety shut-off valves to the combustion industry. Known internationally for their reliability, longevity and compliance with international safety codes, they are often a first choice for engineers designing combustion pipetrains, whether the fuel is gas or oil.
Working on the principle that a constant electrical signal is required to keep them open (or closed, in the case of a normally closed valve), they are suitable for critical applications where interlocks are required to be healthy before the valve can be opened and remain open. Should this interlock be lost at any time during the process, the valve will immediately slam shut, thus isolating the upstream source from the downstream plant. This fail-safe action also takes care of cable-breaks.
The South American petrochemical industry has become an active user of the full range of Maxon Safety Shut-off valves. These valves are also used for the manual or motorised opening or closing of pipelines carrying gases or liquids, commonly used in industrial processes. Motorised automatic valve actuators are used where remote access or unmanned applications are needed. Manual reset actuators require operating personnel to be physically present to actuate the valve from its at-rest position.
All Maxon valves feature one-piece cast-iron or cast steel bodies with micro-lapped seats and discs. Straight through flow path minimises pressure drop through full open swinging gate or rising stem (guillotine action) bodies.
The rising stem principle of operation is well known in the industry and is used extensively in normally closed and normally open gas valves. The swinging gate valve has been specifically developed for oil applications. A hard-faced, micro-lapped seat nut is threaded into the one-piece valve body. The free-floating, hard faced, spring loaded circular disc swings across the seat. Line pressure assists in sealing the disc to the downstream seat. Frequent use and cycling actually helps to keep the valve clean. The disc rotates slightly on every cycle, providing a fresh, clean surface area for sealing off the flow lines.
Maxon is represented solely in South Africa by The Combustion Group in Sebenza. Its engineers are available for application advice and the Maxon test centre is on hand for unusual or difficult applications.
For more information contact The Combustion Group, 011 452 5060, [email protected], www.combustion.co.za
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