A separator is a vessel where hydrocarbon fluids are allowed to separate into a gas phase and a liquid phase. 2-phase separators may be horizontal or vertical. Crude hydrocarbons can contain paraffins and other sticky materials. Density of the material can vary with supply. Pressure and temperature will vary widely depending on fluid source and its location in the process. Depending on well pad geology, some crude hydrocarbons also contain sand and sediment. Over time this can build up in the base of the separator to reduce capacity. Extreme build up may lead to blocked inlets or sediment being drawn down lines and into pumps.