35. HEAT EXCHANGER - A piece of equipment having a tubular piping
arrangement which effects the transfer of heat from a hot to a relatively cool
process stream by conduction through the tube walls.
36. HYDROMETER - A graduated instrument used in determining API or Baume
gravities.
37. IMPELLER - The moving part of a centrifugal pump or compressor which
consists of a set of vanes attached to a central hub.
38. IMPINGEMENT - The contact of flame with the tubes in a furnace, usually
undesirable.
39. FORCED DRAFT - Air supplied to a furnace, cooling tower, or exchanger, by
means of a fan or blower, which force air through the equipment.
40. INDUCED DRAFT - Air supplied to a furnace, cooling tower, or exchanger, by
means of a fan or blower, which pulls air through the equipment.
41. INERT GAS Un reactive; will not support combustion. In refinery use is
generally nitrogen or CO2 (carbon dioxide) (flue gas).
42. INHIBITOR - A chemical additive put in oils to prevent or slow down unwanted
reactions, usually oxidation or gum formation. A chemical added to cooling towers
or process stream to prevent corrosion.
43. INSULATION - A material applied to equipment to prevent the transfer of heat.
44. MERCURY - An element; a silver colored liquid at ordinary temperatures used
extensively in instruments: thermometers - manometers - gauges, etc. It is a great
deal heavier than water, having a specific gravity of 13.5.
45. METER CONSTANT - The numerical constant which must be multiplied by the
number of meter divisions to determine the flow through the meter.
46. MOLECULE - The smallest unit into which a substance can be divided and retain
all of its chemical and physical properties.
47. MOLECULAR WEIGHT - The sum of the atomic weights of the atoms in a
molecule. Example: methane (CH4) (Carbon 12) (Hydrogen 1) = 12 + 4 = 16.
48. ON STREAM - The period of time a refinery processing unit is in actual
production.
49. ORIFICE - A device to restrict the flow through a pipe line.
50. ORIFICE METER - An instrument which measures the flow through a pipe by
means of measuring the difference in pressure on the upstream and downstream
sides of an orifice plate.
51. OUTAGE - The distance from the top of a container to the surface of the liquid in
the container.
52. PISTON - A cylindrical device which reciprocates in a cylinder, causing fluid to
enter and leave the cylinder.
53. PREHEAT - Heat added to a fluid prior to an operation performed on that fluid.
54. PRESSURE DROP - The decrease in pressure, due to friction, which occurs when
a liquid or gas passes through a pipe, vessel, or other piece of equipment.
55. PARTIAL CONDENSER - A condenser (heat exchanger) sometimes located at
the top of the tower that furnishes sufficient cooling to condense a part of the
overhead vapors.
