Separator Type Base ASME BPVC Code 2021

Separator Type Base ASME BPVC Code 2021 can be vertical, horizontal or spherical. Regardless, each has four sections primary separation, secondary sep

TYPES OF SEPARATORS

Separators can be vertical, horizontal or spherical. Regardless, each has four sections : primary separation, secondary separation, liquid accumulation and mist extraction.
These separators can also be classed as two or three-phase. The mixture of the well stream fluids determines which vessel is installed.

Two-Phase Vertical

A two-phase vertical separator is best suited for well streams with high liquid content and low gas volume. Two-phase vertical separators are typically used when the well stream contains large quantities of mud and sand. The vertical separator is easier to drain and clean which makes it excellent for these applications.

The lower portion of the separator contains liquid and the upper portion is for gas.
The well stream enters the vessel near the mid-point of the side. Baffles change the direction and velocity of flow. As the flow changes direc-tion, it loses speed gases tend to follow the changed direction and move upward. Liquids change direction less freely than gas, and move downward because of gravity. Gases move upward through the mist extractor. Here droplets of liquid are extracted by the rings or mesh pad. Liquid droplets form, become larger and fall back into the accumulation section. Gases leave the separator through the gas outlet.
The liquid collect in the bottom of the vessel. Sand, mud and solid debris settle to the bottom where they periodically must be drained. As the liquid level rises, the liquid-level control valve is opened and liquid leaves the vessel through the liquid outlet.

Two-Phase Horizontal

Vertical Type Separator Fluid Flow - Virda

The horizontal separator is designed for processing well streams with large volumes of gas. The large liquid surface area provides for efficient removal of gas from the liquid. A two-phase horizontal separator contains a primary separation section near the inlet, secondary separation and mist extraction sections in the top portion of the cylinder and a liquid accumulation section in the bottom.

The well stream enters the vessel and strikes a baffle. Forward motion is stopped temporarily with the heavy liquids failing to the bottom of the vessel. Gas and liquid spray continue through straightening vanes. These devices cause oil drops to form and drop into the accumulation section. The baffles also straighten the flow of gas. Gas continues horizontally through the mist extractor. Here the remaining liquid is removed by the mesh pad. Gas leaves the separator through the gas outlet.

Liquids collect in the bottom portion of the cylinder. These liquids are separated from the gas flow by divider plates solid settle to the bottom of the separator. These solids are later removed by washing or flushing through the drain. When the liquid level reaches a design level, the liquid-level controller opens the liquid-level control valve. Liquids leave the vessel through the liquid outlet.

Two-Tube Horizontal

The two-tube horizontal separator contains a top cylinder and lower cylinder which are joined by vertical pipes called downcomers. The upper tube is the gas separation section; the lower tube is the liquid accumulation section. Two-tube separators provide better separation than single tube horizontal separators whenever the well stream has slugs and surges. In addition because of the separate tubes, there is less chance of re-entrainment.

Fluidflow Two Tube Horizontal Separator - Virda

The gas separation section contains the inlet, stream deflector, baffles or straightening vanes and a mist extractor. Also on the top section is a relief valve or rupture disk. The well stream enters the top tube through the inlet. The stream is deflected to change direction and velocity. Liquid falls to the bottom of the top tube. Gas and liquid vapors flow through the straightening vanes with liquid droplets collecting and falling to the bottom of the top tube. The gas passes over a vertical plate and through the mist extractor. Here additional liquid droplets are removed from the gas. The gas leaves the top tube through the gas outlet.

In the bottom tube is a liquid level controller, the liquid outlet and a drain. The vertical pipes or downcomers extend into the bottom tube and below the surface of the liquid in the bottom chamber. Liquid which collects on the bottom of the top tube flows through the downcomers into the bottom tube. Sand and other solids settle to the bottom of the tube. Under control of the liquid-level controller, liquid leaves the bottom tube through the liquid outlet.

The two-tube separator can also be a three-phase separator. Gas leaves from the top tube, oil leaves from the top of the lower tube and water leaves from the bottom of the lower tube.

Spherical

The spherical separator provides good gas separation and liquid handling when space is limited. However, when a well stream can contain excess mud or sand, be subject to surging or foamy components, the spherical separator is not economical. In this design the four separator sections are contained within a sphere. The top part of the sphere contains the three sections for gas-liquid separation. The bottom part is the accumulation liquid section.

Fluidflow Spherical Separator Tyype - Virda

The well stream enters the vessel at the top. Inside the sphere the stream is deflected to the surfaces of the sphere along the walls over a dome covering the mist extractor. As the stream enters the lower portion of the sphere, the gas and liquid vapors begin to rise and pass through the mist extractor. Liquid droplets collect and fall downward. Gas leaves the vessel through a vertical pipe above the mist extractor. Different from other separator designs, the gas outlet is at the bottom.

Liquids accumulate in the bottom of the sphere. Gravity settling causes solids and water to go to the bottom of the vessel. Liquid leaves the vessel near the bottom of the sphere under control of a liquid-level controller.

Three-Phase Vertical

The three-phase vertical separator has similar construction to the two-phase vertical. The major difference is in the liquid accumulation section. For a three-phase separator the top portion of the accumulation section contains oil and the bottom portion collects the water. Both liquid areas have their own liquid-level controllers and liquid-level control valves (dump valves).

The well stream enters the vessel in the upper portion. Stream direction and velocity are changed by baffles. Gas and liquid vapors rise. Baffles or straightening vanes and a mist extractor remove liquid droplets. Gas leaves the separator near the top. Oil and water fall to the accumulation section, where gravity separates the oil from the water. Because the settling time is longer than gas-oil separation, the liquid must remain in this section longer than in two-phase separators. This requires a larger liquid accumulation section.

The oil leaves the vessel through a liquid-level control valve in the oil portion of the accumulation section. Water leaves the separator through a separate liquid-level control valve. Both the oil and water valves have liquid-level controllers. Liquid-level control is critical in three-phase separation. The oil-water interface must be contained within ranges or the oil dump valve will begin to dump water rather than oil. On the other hand a malfunctioning liquid-level controller or valve on the water section could cause both water and oil to be dumped into the waste water.

Other Three-Phase Methods

Three-phase separators may be vertical, horizontal or spherical. In some three-phase separators the liquid level is controlled by either one or two weirs. Weirs are dam-like structures which keep liquids at a given level. In a separator with one weir, the weir maintains the combined liquid level. However, both the water and oil levels have individual liquid-level controllers and valves.