Archive for November, 2012

Conventional Relief Valves Working Principle

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Conventional Relief Valves Working Principle

The figure above shows a cross section of a conventional relief valve. Conventional relief valves can be used if the header back pressure is low. The conventional relief valves are commonly used on onshore facility where relief valves are fitted with individual tail pipes. On offshore facility, the valves are used mainly as small threaded …

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Critical Flow

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Critical Flow

The critical flow which also referred to as sonic flow, choked flow, or Mach 1 is the limitation point of a compressible fluid flow through an orifice. The critical flow can occur on a relief valve orifice or a choke. A choke is a condition where piping goes from a small branch into a larger …

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Back Pressure Effects on Relief Valves

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Back Pressure Effects on Relief Valves

The back pressure at production train can affect the relief valve’s capacity or the relief valve’s set pressure. The capacity of a relief valve is the maximum flow rate while the set pressure is the cranking pressure of the relief valve. On conventional relief valve, the set pressure increases directly with back-pressure. The pressure set …

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Balanced Bellows Relief Valves

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Balanced Bellows Relief Valves

Balanced type relief valves consist of spring-loaded valves which contain a bellows arrangement to keep back-pressure from affecting the set point. The picture above shows a balanced bellows relief valve diagram. The bonnet is vented to atmosphere and a bellows is installed so that the back-pressure acts both downward and upward on the same area …

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Heat Exchanger Types

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Heat Exchanger Types

The figure above shows different arrangements of the shells, tubes and baffles in heat exchangers according to TEMA standard classifications. The first letter of the standards designates the heat exchanger front end while the second letter designates the shell type or the heat exchanger middle section and the third letter designates the heat exchanger rear …

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Separation Retention Time

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An amount of time is needed to assure that the liquid and gas reach equilibrium at separator. The time is defined as “retention time” or the average time a molecule of liquid is retained in the vessel assuming plug flow. The retention time is the volume of the liquid storage in the vessel divided by …

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Vessel and Piping Relief Requirements

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A pressure vessel may fail because of more than one condition different scenarios. A low pressure separator vessel may be subject to blocked discharge, gas blowbyfrom the high pressure separator, and fire but only one of these failures is assumed to happen at any time. Each pertinent relieving rate must be calculated and the larges …

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