The mixture of oil and gas enters inlet (A) where it is given a swirling motion by a spiral inlet baffle in the separator space or chamber (B). At this point there are two forces tending to separate the oil from the gas.
The first is the effect of gravity; the second is whirling action, which causes the heavy oil particles to collect on the walls of the separator.
The gas, which still contains some oil in the form of small drops and spray, rises through chamber (B). As the gas enters the swirl cylinder (C), it moves faster and is again caused to whirl so that the oil is forced against the side of the deflector cone (E). This oil drains down through tubes (F) to the bottom of the separator. After passing through the swirl cylinder, the only oil remaining in the gas is in a very few quantity. This quantity is further taken out of the gas by the scrubber dome (G) the gas then passes through the chamber (H) and then leaves a separator through the gas outlet (I).
Oil leaves the separator at the oil outlet (J). The oil level is regulated by a float (L) and control valve, so that liquid covers the drain tubes (F) and the outlet (J). The separator can be cleaned through drain connection (K) in order to remove sand, mud or other materials.
This kind of separator is normally referred to as vertical-type separators of horizontal-type are also common; and although of different design, they have the same uses as a vertical separator.
Horizontal separators may be of single-tubes or double tube design. The oil and gas mixture enters at (A) and hits the angle baffle (B) where the direction of the flow is changed. Here the heavier liquids fall to the bottom of the tank while the gas and spray rise. This wet gas passes into a chamber (C) where small drops gather into larger drops and fall into liquid at the bottom of the tank.
The gas then goes through a final element where the last liquid particles of smallest size are removed from the gas by a mist extractor (E) generally similar to the scrubber dome described in the vertical separator. The gas then goes through the top portion of the tank and into the gas outlet (F). The liquid from which the gas has been removed moves along the bottoms of the tank past the plates (D) to the oil outlet (H). The plates act as baffles to keep waves from forming in the liquids.
Horizontal separators of two-tube design are often used. The unit is made of two horizontal tubes mounted one above the other. The tubes are joined by flow channels near the ends of the tubes. The mixed stream of oil and gas enters at one end of the upper tube. The liquids fall through the first connecting flow pipe into the liquid reservoir, which occupies the lower portion of the bottom tube.
The wet gas flows through the upper tube. Along this path of flow the liquids fall out because of their weight and the scrubbing action of a series of “Honeycombed” mist extractors. These liquids fall first to the bottom of the upper tube and then drain through the connecting flow pipes to the liquid reservoir in the lower tube. Gas which comes out of the oil in the lower tube rises through the connecting flow channel to the upper chamber where it joins dry-gas stream leaving the separator at the gas outlet. Oil is discharged through a connection mounted in the lower part of the bottom tube. Separators remove entrained liquid from the gas. Wet gas contains no entrained liquid, but it is usually saturated with water. Dry gas has had a portion of this water vapor removed.