Oil and Gas: Terms & Glossary (6)

Malleable iron	Cast iron that has been heat-treated to improve its tensile strength.
Mandrel	A long, pointed shaft used to pierce molten steel billets to form seamless pipe.
Manhole	Similar to large nozzles that allow workers entry points into a vessel. Generally 18" ID.
Manhole hinge	A hinge that creates a pivot point allowing the blind flange attached to the manhole to be easily removed for worker entrance.
Manifold	A main pipe way having numerous branch connections.
Manway	See manhole.
Match line	Lines used to divide the plot plan into small drawing areas.
Material takeoff	The gathering of descriptions, quantities, and prices for various components of the piping system, that is, pipe, flanges, fittings, valves, bolts, gaskets, etc.
Meter run	A clear run of pipe having a set of orifice flanges that is used to measure flow rate through the pipe.
Naphtha	Colorless flammable by-product of crude petroleum used in the manufacture of gasoline.
Nipple	A short length of pipe used to connect screwed or socket-weld fittings to one another.
Nozzle	The connecting point of the piping configuration to the vessel or equipment. Nozzles are provided in locations where a commodity is either introduced or removed from a vessel or piece of equipment.
Nozzle arrangement	The positioning of nozzles on a piece of piping equipment.
Nozzle orientation	Plan drawing depicting the location of nozzles around the perimeter of a vessel using angular measurements from 0°.
Octagon	An eight-sided concrete foundation placed below vertical vessels that distribute the vessel's load over a broader area.
O-lets	Any of several fittings used to make branch connections for welded, screwed, or socket-weld pipe.
Operator	Device used to activate valving.
Orifice flange	Flange with a hole drilled into the flange face perpendicular to the pipe that permits testing equipment to be inserted.
Orifice flange union	Pair of orifice flanges, orifice plate, bolts, nuts, jackscrews, and gaskets. Primary components of a meter run.
Orifice Plate	Metal plate with a hole of Predetermined size sandwiched between orifice flanges.
O.W.S (Oily Water Sewer)	An underground piping system used to collect and transfer contaminated discharge to a treatment facility.

Fundamentals of Oil & Gas Accounting, 5th Edition