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Dynamic sealing
Durco has designed its innovative Marathon plug valve to reduce emissions from chemical processes to the lowest practicable levels, facilitating user compliance with the US 1990 Clean Air Amendment Act and similar BC legislation as well as maintaining long term, leakage free integrity even on high cycle on/off or throttling duties.
Built for reliability in arduous service on hazardous, toxic, and corrosive applications, the Marathon valve carries a three year guarantee on the stem seal and is available in sizes from 15 mm to 200 mm.
Design features include a hastalloy, bellows type diaphragm welded to the thrust collar. This provides an additional atmospheric seal between the top cap and thrust collar and ensures that if, due to wear, damage or permeation, media passes through the primary seal and reverse lip diaphragm secondary seal, risk of leakage to atmosphere is minimised.
The possibility of leakage around the stem is reduced by the incorporation of a 55 bar Viton dynamic rotary O-ring seal between the thrust collar and the stem. Further security is provided by a second O-ring mounted outboard. This has the dual function of preventing damage to seal surfaces caused by contaminants such as water, dirt, metal shavings etc., entering the seal area as well as, under extreme conditions, acting as a back up to the other three seals.The O-rings are reinforced by PTFE back up
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