Category: Relief Systems

Flare System Pilots and Ignition

Reliable pilot operation under all wind and weather conditions is essential. Flaring operations are for the most part intermittent and non-scheduled. The flare must be instantly available for full emergency duty to prevent any possibility of a hazardous or environmentally offensive discharge to the atmosphere. Wind-shields and flame-retention devices may be used to ensure continuous […]

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Flare System Types

Flares can be classified as: 1. Pipe Flares — Vertical or horizontal pipes with external ignition pilot. 2. Smokeless Flares — Vertical, single, or multiple burners designed to properly mix adequate oxygen from the air with relieved vapors for complete combustion. 3. Endothermic Flares — Elevated incinerators for low heat content streams. Pipe Flares — […]

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Knockout Drum

Gas streams from reliefs are frequently at or near their dew point, where condensation may occur. A knockout drum is usually provided near the flare base, and serves to recover liquid hydrocarbons, prevent liquid slugs, and remove large (300-600 micron diameter) liquid particles. The knockout drum reduces hazards caused by burning liquid that could escape […]

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Sizing Methods

Line sizing for flare headers and relief lines requires the use of compressible flow equations. Computer programs are available for use in sizing flare headers. A calculation method is outlined below: 1. Start at the flare tip, where the outlet pressure is atmospheric, use design flows and work toward the individual relief valves (pressure drop […]

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Resonant Chatter

Resonant chatter can occur with safety valves when the inlet piping produces excessive pressure losses at the valve inlet and the natural acoustical frequency of the inlet piping approaches the natural mechanical frequency of the valve’s basic moving parts. The higher the set pressure, the larger the valve size, or the greater the inlet pipe […]

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Rapid Cycling

Rapid cycling can occur when the pressure at the valve inlet decreases at the start of relief valve flow because of excessive pressure loss in the piping to the valve. Under these conditions, the valve will cycle at a rapid rate which is referred to as “chattering.” The valve responds to the pressure at its […]

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