Tags: Relief Valve

Relief Header Design

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Relief Header Design

The relief header is a system of piping connecting the outlets of all the relief valves into a common pipe or header that goes to the relief scrubber and then out the vent as shown in Figure 13-11. There are some general rules of thumb useful for sizing relief piping. The goal is to make …

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Relief Valve Vent or Flare Tip

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A pipe that releases gas to disperse into the atmosphere is called a vent. If the gas is burned at the tip, it is called a flare. In its simplest form, a vent or flare tip is a pipe. Sometimes the pipe diameter is reduced for the last 5 ft or so to increase exit …

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Relief Valve Vent Scrubber

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A vent scrubber is a two-phase separator designed to remove the liquid from the relieving fluids before the gas is flared or vented. The liquid is returned to the process. Design of vent scrubbers is covered in two-phase separators. A vent scrubber is sized as a standard two-phase separator with a liquid droplet size in …

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Relief Valve Installation

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Each relief valve should be equipped with inlet piping no smaller than the valve inlet flange size, and inlet piping should be as short as practical. Inlet piping should be designed so that the pressure drop from the source to the relief valve inlet flange will not exceed 3% of the valve set pressure. Pressure …

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Two-Phase Flow Standard Sizes

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Two-Phase Flow Standard Sizes

Two-Phase Flow There are no precise formulas for calculating orifice area for twophase flow. The common convention is to calculate the area required for the gas flow as if there were no liquid present and the area required for the liquid flow as if there were no gas present. The two areas are then added …

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Liquids Flow Rate

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Liquids Flow Rate

Conventional Valve, Balanced-Bellows Valve, or Pilot-Operated Valve The corresponding equations for liquid flow are the following: Note that a preliminary orifice size must be determined in order to calculate Reynolds number. If the viscosity correction is significant, it may be necessary to iterate to get a final size.

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Effects of Back Pressure

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Effects of Back Pressure

Back-pressure can affect either the set pressure or the capacity of a relief valve. The set pressure is the pressure at which the relief valve begins to open. Capacity is the maximum flow rate that the relief valve will relieve. The set pressure for a conventional relief valve increases directly with back-pressure. Conventional valves can …

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Critical Flow

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Critical Flow

The flow of a compressible fluid through an orifice is limited by critical flow. Critical flow is also referred to as choked flow, sonic flow, or Mach 1. It can occur at a restriction in a line such as a relief valve orifice or a choke, where piping goes from a small branch into a …

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