Piping to and from the mud gas separator shall interfere as little as possible with the working of the mud gas separator. The following constraints should be observed:
- The use of valves, pipe expansions or contractions within ten pipe diameters of the inlet nozzle should be avoided because of their tendency to generate relatively small liquid droplets. If a valve in the feed line near to the separator cannot be avoided, it should be of the gate or ball type, fully open in normal operation. High pressure drops which cause flashing and atomisation shall be avoided in the feed pipe. If a pressure-reducing valve in the feed pipe cannot be avoided, it should be located as far upstream of the vessel as practicable.
- The use of bends within ten pipe diameters of the inlet nozzle should be avoided because they will generate gas flow maldistribution in the mud gas separator.
If bends cannot be avoided within ten pipe diameters of the inlet nozzle, the following rules should be followed:
- For knock-out drums, wiremesh and vane-type demisters and for any other type of demister in which a tangential inlet is NOT used, a bend in the feed pipe is only permitted if this is in the vertical plane through the axis of the feed nozzle. If this results in a riser system just upstream of the vessel, slugging may occur in case of a high feed flow parameter. The vessel should be able to handle this.
- For cyclones, a bend in the feed pipe is only permitted if this is in a horizontal plane and the curvature is in the same direction as the cyclone vortex.
- If desired, a pipe reducer may be used in the vapour line leading from the separator, but it should be situated no closer than twice the outlet nozzle diameter from the top of the vessel.
- Piping layout and location/design of any reducer shall be such that no pockets exist where liquids can accumulate and increase the risk of slug flow.
If the above conditions cannot be satisfied, liquid removal will be less efficient.
The observations listed above are illustrated in Figure 1.