Discover the IHRDC Energy Glossary_beta

R chart

A control chart used to plot the range of measurements in a sample group.

raceway

Any designed structure that cables and conductors follow.

raceway diagram

A drawing that shows the raceway layout in a specific plant or building.

RACI chart

racking out

The act of physically disconnecting and removing a circuit breaker from a switchgear assembly to eliminate an electrical energy source.

radial

Relating to a line or direction, perpendicular to the shaft or axis of rotation.

radial bearing

A bearing that prevents shaft movement in any direction outward from the centerline of the shaft.

radial blade fan

A type of centrifugal fan in which the blades are flat and mounted radially to a hub so that air is pushed straight out from the hub.

radial flow

Radial flow is the flow into the wellbore during a well test from a reservoir having no apparent outer boundary limit affecting the fluid flow during the test period, the direction of flow being perpendicular to the axis of the well.

radial impeller

An impeller that produces flow that is basically perpendicular to the shaft of a mixer.

radial thrust

A force exerted perpendicular to the centerline, or axis, of a shaft.

radially split pump

A pump with a casino that is split perpendicular to, or around, the axis of the pump's shaft. Sometimes caused a "barrel' pump or a -cartridge' pump.

radiant section

The tubes in a furnace that are in direct line of sight with the burner flame.

radiation

A mode of heat transfer in which heat is transferred through electromagnetic waves (infrared rays).

radiator

On a power transformer, typically an arrangement of tubes mounted externally on the transformer enclosure through which oil flows and through which heat is dissipated.

radio repeater

A radio repeater is a combination of a radio receiver and a radio transmitter that receives a signal and retransmits it, so that two-way radio signals can cover longer distances.

radioactive density analyzer

An analyzer that measures density without making direct contact with a process liquid.

radioactive, radioactivity, radioactive decay

The process by which a nucleus of an unstable atom loses energy by emitting ionizing radiation, including alpha particles, beta particles, gamma rays, and conversion electrons. A material that spontaneously emits such radiation is considered radioactive.

radioisotope

A radioactive material that will produce a constant amount of nuclear radiation.

radius

The distance from the center point of a circle to any point on its circumference; half the diameter.

rag

The sludge-like, oily water mixture that collects at the water/oil interface in a desalter.

rail

The vertical lines on the left and right sides of a ladder diagram that connect the rungs.

raised face flanges

A flange designed so that the mating surface of the flanges extend out farther than the surface that contains the bolt holes.

raised-face flange

A flange with a raised area around the center upon which a gasket is usually compressed.

RAM

Random Access Memory, the storage area in a computer that contains active operating and program instructions.

ramp

A controller enhancement that enables a process variable to be taken from a start point to a final set point in a series of controlled steps. The ramp function is typically used during startups to minimize thermal stress.

ramp rate

The change in temperature per unit of time during boiler warmup and shutdown.

ramp-and-soak control

A type of process control characterized by periods during which a process is stabilized before continuing to be ramped toward a setpoint.

ramping down

The process of gradually reducing temperature and pressure during boiler shutdown.

random decision forests (RDF)

Random Decision Forests are an ensemble learning method for classification, regression and other tasks that operates by constructing a multitude of decision trees at training time. For classification tasks, the output of the random forest is the class selected by most trees. For regression tasks, the mean or average prediction of the individual trees is returned. RDFs correct for decision trees' habit of overfitting to their training set.

range

Range The low and high limits of a scale.

range control

A control on a test instrument that is used to determine the range of values that the instrument will measure.

rappers

Hammer-like devices that strike the plates of an electrostatic precipitator and dislodge particulates.

rarefaction

Rarefaction is the reduction of an item's density, the opposite of compression.

ratchet stop micrometer

An outside micrometer equipped with a ratchet stop to stop adjustment of the tool when the right amount of pressure is exerted.

rate

In process control, the tuning parameter that applies derivative (PID) control, modifying the controller output according to the rate of change of the error or process variable. In mathematics, a comparison of two quantities through division.

rate of solution

The speed with which a solute dissolves in a solvent.

rated capacity (lifting capacity)

The amount of weight for a specific load center and maximum lift height that a forklift can safely lift and carry.

ratio control

A control system designed to keep one or more dependent variables at a percentage of an independent variable.

ratio curve on pulsed neutron log

The ratio curve shown on pulsed neutron log displays is the ratio of the count rates of the near to the far detector.

rattail joint

A type of splice that is sometimes used in a junction box and for connecting branch circuits. Also called a rattail splice.

raw natural gas

Natural gas as it is produced from the reservoir.

Rayleigh wave

Rayleigh waves are a type of surface acoustic wave that travel on solids. They can be produced in materials in many ways, such as by a localized impact or by piezo-electric transduction, and are frequently used in non-destructive testing for detecting defects. They are part of the seismic waves that are produced on the Earth by earthquakes.

Raynaud's phenomenon

An MSD characterized by numbness and whitening of the fingers due to lack of blood supply, and with pain when subjected to cold temperatures. It is caused by significant exposure to vibration, such as when using heavy power tools.

RC circuit

A circuit incorporating both resistance and capacitance.

RC oscillator

An oscillator that uses resistors and capacitors (connected in series) in its tuned circuit.

re-range

To reset the lower range value and the upper range value of a smart field device, either because of a process alteration or to use the device on another process.

reactance

The vector sum of the inductive reactance and the capacitive reactance in a circuit. In electrical formulas, reactance is typically represented by a capital X.

reactant

A product of one reaction that is suitable and appropriate for use as a feed or charge material for another reaction.

reaction

In turbines, a type of blade that causes the wheel to rotate when high-speed steam forces the blades opposite the flow direction. In process engineering, an operation used to change the form of materials under carefully controlled conditions.

reaction rate

A measure of the amounts of reactants that are converted into products in a given period of time.

reaction section

The section of an alkylation unit in which the process reactions occur and in which the catalyst is separated from the reacted and unreacted hydrocarbons.

reactive power

Power that goes back and forth between a power source and an inductive or capacitive device.

reactivity

The tendency of a substance to undergo a chemical change or reaction, describing how a chemical interacts with other substances or how its characteristics might change under some conditions, potentially involving a release of energy such as an explosion.

reactivity hazard

A material that poses a risk of a violent chemical reaction.

reactor

A vessel or tank used to combine or convert raw materials into products by chemical reactions. In a cat cracker, it is where cracked gas is disengaged from spent catalyst. In protective relaying, a component of a filter circuit that functions like an induction coil, working with capacitors to produce voltage across a voltage coil.

reactor process system

A process system that contains a reactor.

real time

Real time is used to distinguish reporting, depicting, or reacting to events at the same rate and sometimes at the same time as they unfold, rather than compressing a depiction or delaying a report or action.

real time, real-time

Real-time or real time is used to distinguish reporting, depicting, or reacting to events at the same rate and sometimes at the same time as they unfold, rather than compressing a depiction or delaying a report or action.

real-time data

Information concerning the current status of some variable. For example, present temperature, pressure, or speed.

real-time sampling

A sampling mode in which an oscilloscope collects as many samples as it can as a signal occurs.

reaming

Reaming is an additional operation when drilling a borehole that may be done to part or all of the borehole. Reaming is conducted to enlarge the hole to its planned diameter. Several possible reasons account for the diameter of the borehole being smaller than planned, for example, the drill bit could be worn and thus smaller diameter, which results in an under-gauge hole.

reasonable certainty

A high degree of certainty. Much more likely to be achieved than not.

reboiler

A type of shell and tube heat exchanger used to heat and vaporize the bottoms product and lighter products in a distillation column. Also, the vessel that generates steam at the bottom of a stripper to strip acid gases from rich amine solution.

reboiler (reconcentrator)

The vessel where water is boiled out of the glycol.

reboiler still column

A vertically mounted vessel on top of the reboiler where glycol vapors condense and water vapors are released.

receiver

A component in a refrigeration system that stores liquid refrigerant under pressure. In sonic level measurement, the part that receives sound waves after they bounce off the liquid surface and converts sound energy to electrical energy.

receiver array

A receiver array is a group of receivers that are connected together, traditionally by wires, although cableless receivers are now available.

receiver stations

A receiver station is generally considered a shotpoint location to which specific receivers are located.

receiving

The first step of a production process, in which incoming feedstocks and materials are checked and regulated.

reciprocating

A back and forth, straight-line motion; a device that has forward and backward motion.

reciprocating compressor

A device for raising gas pressure using reciprocating motion.

reciprocating pump

A type of positive displacement pump that uses a piston, diaphragm, or other device moving in a back-and-forth motion to move fluid.

reciprocating saw

A relatively heavy-duty, portable power saw that has a blade mounted at the end of the using. The blade cuts with a back-and-forth, horizontal motion.

reclosing relay

A relay designed to reclose a circuit breaker after it has been tripped.

recommissioning a tank

The process of putting an out-of-service storage tank back online.

recommissioning checklist

A checklist of inspections or other procedures that are performed during a recommissioning operation.

recompletion

The process of entering an existing wellbore and performing work designed to establish production from a new zone.

recordable cases

As related to health, safety and environment (HSE), recordable cases include occupational death, nonfatal occupational illness and those nonfatal occupational injuries which involve one or more of the following: loss of consciousness, restriction of work or motion, transfer to another job or medical treatment (other than first aid).

recorder

A device or instrument that indicates the value of one or more process variables at the time of reading and provides a record of the values over a period of time.

recorder controller

A process control instrument that performs a recording function and a controlling function.

recording psychrometer

An analyzer that is used for continuous humidity measurements.

recovery efficiency

Recovery efficiency is a numeric expression, expressed as a percentage, of that portion of the in place hydrocarbon quantities of petroleum estimated to be recoverable.

recovery factor

The recovery factor is the hydrocarbon recovery per unit volume of an oil or gas field, usually expressed in barrels per acre-foot, or cubic feet per acre-foot.

recovery tank

A tank used to store off-spec materials, by-products from processes, and wastes from which valuable products or components can be recovered; also called a slop tank.

rectangle

A four-sided shape with four 90 angles.

rectification

The process of changing AC voltage to pulsating DC voltage.

rectifier

An electronic device or circuit that allows alternating current to flow in only one direction, thereby changing AC to pulsating DC voltage.

rectifier bridge

The part of a variable speed drive (typically a DC drive) that changes applied AC into DC.

recurved spit

A recurved spit is a spit whose outer end is turned landward by current deflection, by the opposing action of two or more currents, or by wave refraction.

recycle valve

A valve which allows compressed gas to recycle from the discharge line back into the suction line of the cylinder.

red beds

Sedimentary rocks (typically sandstone, siltstone, and shale) that are predominantly red in color due to the presence of ferric oxides, which typically occur as a coating on the grains of sediments.

redox reaction

A reaction that involves a transfer of electrons from one atom, molecule, or ion to another.

reduced voltage start motor controller

A motor controller that reduces the amount of power supplied to a motor during start up to limit high inrush current and reduce start up torque.

reducing connector

A crimp-on connector that is used to splice together two wires of different sizes.

reduction

In chemistry, a reaction in which a substance gains electrons. In catalysis, a stage of catalyst regeneration in which oxygen is removed from the catalyst surface.

reed switch

A device used to close and open an electrical circuit; consists of a pair of contacts, each mounted on a flexible metal strip, that are closed or opened by the introduction of a magnetic field around the switch.

reed valve

A suction or discharge valve that uses reeds (or strips) which lift and seat by differential pressure to control gas flow. This valve is used for low pressure compression requirements.

reef talus

Reef talus is massive, inclined strata composed of reef detritus deposited along the seaward margin of an organic reef.

reefs

A reef is a rock, sandbar, or other feature lying beneath the surface of the water, often 80 meters or less beneath low water.

reeve

To pass, or thread, rope around the sheaves in a block.

reference fuels

Fuels that have undergone multiple lab tests and have a guaranteed octane number.

reference junction

A point on the non-inverting input terminal of an op amp circuit at which the voltage is said to be the reference voltage for the op amp's summing junction.

reference voltage

The voltage in a comparator that the input signal is compared to; often zero volts.

refinery

A group of plants or units that work together to produce a variety of products.

reflux

Condensed overhead product that is pumped back into the top of a distillation column to control temperatures. Also, the process of condensing vapor to liquid so it falls downward in a still column while allowing lighter vapor to continue rising. Generally, a process where a fluid is removed from a vessel, condensed, and returned to enhance the process.

reflux coil

Coil located in the top of still column to aid in condensation of glycol vapor.

reflux liquid

A cooler liquid that is circulated through coils in the reboiler still column to condense glycol vapors.

reflux rate

The rate at which reflux is pumped back into a distillation column.

reflux ratio

The ratio between the amount of overhead product returned to a distillation column as reflux and the amount sent to storage.

reformate

A high-octane, high-quality gasoline feed produced from a charge material by a catalytic reforming process, sent to the gasoline blending area.

reforming

A chemical modification that converts a charge material into a higher-octane product called reformate.

refractory

Heat-resistant material used to line a furnace shell.

refrigerant

A fluid used in a refrigeration system to transport heat, which boils at relatively low temperatures and liquefies under pressure higher than atmospheric.

refrigerated tank

A tank that has been modified to contain materials at low temperatures.

refrigeration

A process of cooling by transferring heat out of a substance or area. In gas processing, a method for chilling a natural gas stream to remove NGLs.

refrigeration system

A system that controls air temperature in a conditioned area.

regenerable fixed-bed system

A carbon adsorption system that allows one carbon bed to be desorbed while a second carbon bed removes contaminants from a gas stream.

regenerate

To separate the acid gases from the amine solution.

regenerating section

In an amine treatment unit, the section in which the H₂S is stripped from the amine so that the amine may be used again. In a mercaptan extraction system, the section in which mercaptans are converted to disulfides and then separated from the caustic so that the caustic may be used again.

regeneration

The process of purifying and reusing glycol (after it has absorbed water and hydrocarbons) or amine solution (after it has absorbed acid gases).

regenerative process

Process of purifying the glycol after it has absorbed water and hydrocarbons.

regenerator

The vessel in a cat cracking unit in which coke deposits are burned off of spent catalyst so that the catalyst can be reused.

regolith

Regolith is a blanket of unconsolidated, loose, heterogeneous superficial deposits that cover solid rock. It includes dust, broken rocks, and other related materials.

regressing

Regression occurs when the sea level drops and the shoreline moves away from land, exposing areas of the seafloor that were previously submerged.

regressive

Regression is a geological process where, due to a falling sea level, the shoreline moves seaward causing the water to move away from the land, exposing previously submerged areas to weathering. Transgression is the opposite process where, due to a rising sea level, the shoreline moves landward, often flooding low-lying areas.

regular lay

A form of wire rope construction in which the strands of the rope spiral in one direction while the wires that make up the strands are wound in the opposite direction.

regulation

In drives, how closely speed matches the set speed, a function of how well feedback modifies a command signal. In power supplies, how well a constant voltage is maintained to a load regardless of changes in source voltage or load resistance.

regulator

In oxy-fuel welding, the component attached to a cylinder valve that reduces high cylinder pressures to working pressures and maintains steady gas flow. In electronics, a circuit that maintains a constant voltage to a load regardless of changes in source voltage or load resistance.

regulators

On a gas-sealed power transformer, devices that control the flow of gas from a gas cylinder to the transformer enclosure. The regulators also reduce the high pressure in the cylinder to a safer, lower pressure in the transformer enclosure.

reheat steam system

A system that increases the energy of steam exhausted from the HP section of the turbine before it enters the IP section.

reheat stop valve

A valve that stops the flow of steam to the IP section of the turbine in case of turbine overspeed. Controlled by the turbine control system.

reheater

A boiler component that adds heat to steam after it has moved through a portion of the turbine. The reheated steam then flows through the remainder of the turbine.

Reid vapor pressure (RVP) analyzer

An analyzer that may be used to measure vapor pressure during an inline blending process.

relative dielectric permittivity

Relative dielectric permittivity is the degree to which a medium resists the flow of electric charge divided by the degree to which free space resists such charge. The degree, or dielectric permittivity, is defined as the ratio of the electric displacement to the electric field strength. The term is also known as the relative dielectric constant.

relative humidity

The amount of water vapor in air compared to the amount of water vapor that the air could hold at a given temperature and pressure.

relative permeability

A dimensionless measure of the effective permeability of a phase in multiphase flow through porous media. It is the ratio of the effective permeability of that phase at a particular saturation to the absolute permeability at total saturation.

relaxation, nuclear magnetic relaxation

Relaxation is the processes by which an excited magnetic state returns to its equilibrium distribution. Nuclear magnetic resonance relaxation measurement can be used for spectral assignment and the study of quadrupolar and paramagnetic interactions, and exchange dynamics.

relay

A device that responds to changes in current or voltage in a circuit to operate contacts in the same circuit or in a different circuit.

relief device

Any device that is used either to vent off vapors that cause excess pressure, or to admit air or a gas into an area to prevent pulling a vacuum.

relief valve

A valve that opens (slowly or proportionally) to relieve excess pressure in a system and then closes automatically. Used to protect equipment from overpressure and often installed near the discharge of positive displacement pumps. Also known as pressure-relief valve, safety valve, or pop valve.

relinquishment

At the beginning of the Exploration Period, a Contractor usually has a large “block” or area to explore; however, as each exploration phase concludes, a portion—often around 20% of the area—must be relinquished or returned to the government for potential issuance to another company.

remote control

A type of device that allows a welder to control the operation of a welding machine while welding.

remote I/O

An Allen-Bradley network for connecting PLC-5 processors, remote I/0 chassis, PCs, and HMIS together.

remote I/O network

Allen-Bradley's proprietary network for connecting I/O racks and high-end HMIs together.

remote rack or chassis

A rack of I/O modules in a PLC system that is connected to the local rack containing the processor module. There may be several such racks in a system.

remote racks

The logical racks in a PLC system chassis that do not have the PLC processor in them.

remote set point (RSP)

The set point provided to a controller from another part of a loop; often the set point provided by the primary loop in a cascade system.

renewable-link fuse

A fuse that can be used again after its blown fuse link is replaced with a new one.

repeatability

A characteristic required of a flow meter in which volume measured must be within 0.05% for five of six consecutive trips.

repetition

An ergonomic risk factor that involves performing the same motions over and over again with little variation. Repetition can gradually wear on muscles and tendons, even if the force required is low, because of inadequate time for them to recover.

reproductive toxins

Chemicals that affect the reproductive capabilities, including chromosomal damage (mutations) and effects on fetuses (teratogenesis).

rerun column

A type of acid regenerator that uses a stream of hot isobutane to strip out HF acid from contaminants.

rescue service

The personnel designated to rescue employees from permit spaces.

reserves

Estimated remaining quantities of oil, gas, and related substances anticipated to be commercially and economically producible by application of development projects to known accumulations from a given point forward, justified for development. There must exist, or be reasonable expectation of, the legal right to produce, installed means of delivery, and all required permits and financing.

reservoir

A subsurface body of porous and permeable rock containing an individual and separate natural accumulation of moveable petroleum, confined by impermeable rocks or water barriers and characterized by a single pressure system.

reservoir characterization

The process of building a model of a reservoir that incorporates all characteristics pertinent to its ability to store and produce hydrocarbons. These models are used to simulate fluid behavior under different conditions and find optimal production techniques to maximize recovery. Some data is derived from cuttings, core analyses, and other geologic studies.

reservoir compaction

Compaction that occurs as hydrocarbons are produced from a reservoir and pore pressures decline, causing effective stresses to increase.

reservoir depletion

Reservoir depletion is the decline in the hydrocarbons within a reservoir. Oil depletion is the decline in oil production of a well, or oil field.

reservoir depletion, depleted reservoir

A depleted reservoir can be defined as a reservoir that has produced oil or gas.

reservoir modeling

The construction of a computer model of a petroleum reservoir for the purposes of improving the estimation of reserves and making decisions regarding the development of the field. Reservoir models typically fall into two categories: a) geological models are created by geoscientists and aim to provide a static description of the reservoir, prior to production. b) reservoir simulation models are created by reservoir engineers and use finite difference or streamline methods to simulate the flow of fluids within the reservoir over its production lifetime.

reservoir surveillance

Reservoir surveillance, starting with the data acquisition from the wells and the production network, is to obtain data for evaluating well and reservoir performance, reserves evaluation and finally, the foundation development, on which development options are optimally selected and decisions are made.

reservoir trap

A reservoir trap consists of an impervious stratum that overlies the top and side of the reservoir rock, thereby prohibiting hydrocarbons from escaping upward and laterally.

reset

The tuning parameter that applies integral (PID) control, modifying the controller output according to the time integral of the error.

reset contacts

Contacts in a reclosing relay that turn the motor off with the relay in the "start" position.

reset windup

The increasing reset correction that builds up before a process variable responds.

residual

In statistics, the difference between the observed value and the mean value that a model predicts. In refining, leftover material that collects in the bottom of an atmospheric distillation tower.

residual chlorine

The amount of chlorine left over in water after micro-organisms have been killed.

residual energy

Hazardous energy that is present in equipment even when no source of power is connected.

residual fuel

A heavy fuel made of residuals, or tower bottoms; used for firing boilers or furnaces. Also called bunker oil or #6 fuel oil.

residual oil saturation

The fraction of pore volume occupied by oil at the end of oil displacement using a specific fluid (ROS). It signifies the ultimate recovery under a given displacement process and represents the end point of relative permeability curves. It is the saturation achieved after an infinite number of pore volumes of displacing fluid have flowed through the rock. Depends on flow rate, permeability, capillary end effects, test methodology, and the test laboratory.

residual oil/gas saturation

Residual oil/gas saturation is the oil/gas that cannot be mobilized and recovered from a rock.

residuals

In statistical models, a residual is the difference between the observed value and the mean value that the model predicts for that observation.

residue gas

Gas after being processed with the liquids removed.

residuum fraction (also known as residue, or residual)

The fraction containing the heaviest hydrocarbons (over C33) with the highest boiling points (over 800°F).

resin beads

Small, porous, plastic beads used in ion exchangers.

resistance

An electrical property that opposes or restricts the flow of current through a circuit, measured in ohms. In process control, any opposition to flow. In electrical formulas, resistance is typically represented by a capital R.

resistance temperature detector (RTD)

A type of temperature measurement device that measures temperature changes in terms of changes in electrical resistance.

resistance temperature device (RTD)

A variable resister which measures winding temperatures in an electrical motor.

resistivity

An intrinsic property that quantifies how strongly a material opposes the flow of electric current. The inverse of conductivity. Resistivity is a property of the material itself, while resistance also depends on the volume measured. The two are related by a system constant (length divided by area).

resistivity factor, formation resistivity ratio

The resistivity factor, or formation resistivity ratio, is the ratio of the resistivity of the rock saturated with brine (Ro) to the resistivity of the brine (Rw).

resistivity index

The ratio of the true resistivity (Rt) to the resistivity of the same rock filled with water (Ro). It is related to water saturation by the saturation exponent n (I = Sw⁻ⁿ), and is a key component of the Archie equation.

resistivity, electrical resistivity

An intrinsic property that quantifies how strongly a given material opposes the flow of electric current.

resistor

A component specifically designed to increase and/or control the amount of resistance in a circuit, used to reduce current flow.

resolution

The size of the minimum step in input or output voltage or current in an analog I/O module.

resolver

A feedback device typically used with a variable speed controller to monitor the position and speed of a shaft by generating sine waves as the shaft turns.

resources

All quantities of petroleum (recoverable and unrecoverable), naturally occurring, discovered and undiscovered, plus those quantities already produced. Resources include both discovered and undiscovered accumulations.

resources, hydrocarbon resources

Hydrocarbons which may or may not be produced in the future. A resource number may be assigned to an undrilled prospect or unappraised discovery. Appraisal by drilling additional delineation wells will confirm field size and may lead to project sanction, at which point the relevant government body issues a production license enabling development. This is also the point at which reserves can be formally booked.

respirator

Any device designed to protect the user from airborne contamination or to supply the user with a breathable gas in an oxygen-deficient atmosphere.

restore

The process of downloading a project from a PC or an EEPROM to a PLC.

restraint coil

A component that works to keep the contacts of a relay open.

retaining nut

A nut that keeps a part in place.

retention pond

A pond designed to capture contaminated rainwater runoff and keep it from getting into a nearby body of water or soaking into the ground.

retentive time-delay relay

A time-delay relay that retains the accumulated value of the delay when the timer rung goes false. When the rung goes true again, the timer starts timing where it left off. (Normal time-delay relays immediately reset the accumulated value to 0 when the timer rung goes false.)

retrieval system

The equipment (including a retrieval line, chest or full-body harness, wristlets, if appropriate, and a lifting device or anchor) used for non-entry rescue of persons from permit spaces.

return

The instruction that directs PLC program control to return to the original program when a subroutine is terminated.

return activated sludge

Activated sludge that is returned from a clarifier to an aeration basin in a biological treatment system.

return on capital employed (ROCE)

ROCE is a measure of the profitability of a company's capital employed in its business compared with that of its peers. ROCE is calculated as a ratio, with the numerator of net income plus after-tax interest expense and the denominator of average total equity plus total debt. The net income is adjusted for nonoperational or special items impacts.

reverse acting

A type of controller setup in which an increase in the value of the input causes a decrease in the value of the output.

reverse bias

The bias potential that inhibits current flow across a P-N junction: a positive potential applied to the N-type material and a negative potential applied to the P-type material.

reverse biased

The bias potential that inhibits current flow across a P-N junction: a positive potential applied to the N-type material and a negative potential applied to the P-type material.

reverse buckling disc

A pressure relief device that ruptures when the disc is pushed outward by system pressure. Some reverse buckling discs have a knife point to puncture the disc or are scored.

reverse drilling break

This slowing of drilling progress, while technically also a drilling break, is usually referred to as a "reverse drilling break", or simply "reverse break."

reverse fault, thrust fault

A reverse, or thrust, fault is a geological fault in which the hanging wall has moved upwards relative to the footwall. Reverse faults occur where two blocks of rock are forced together by compression.

reverse flow

See Counterflow.

reverse resistance

Resistance across a reverse-biased P-N junction.

revision block

A portion of a title block that usually contains a general description of each revision, the revision number, and the date of the revision.

revision number

A number on a diagram that indicates the number of times a diagram has been revised.

reworking

Reworking is the mixing of various sediments in a fluvial environment.

rheology

Rheology is a branch of physics that deals with the deformation and flow of matter, especially the non-Newtonian flow of liquids and the plastic flow of solids.

rheostat

A rheostat is an electrical instrument used to control a current by varying the resistance.

ribbon mixer

A mixer that consists of two spiral-shaped impellers, called ribbons, inside a rectangular vessel.

rich amine

An amine solution that has absorbed acid gases (hydrogen sulfide and/or CO2).

rich oil

A special oil used in gas processing when it is saturated with NGLs.

rider

A type of motor-driven pallet jack that has a platform to allow the operator to stand on the jack as it is being used. Also called a walkie/rider.

rig spread cost

The rig spread cost is the total daily operating cost of an operating oil rig.

rig up

To make ready for use. Equipment must be moved onto the rig floor and assembled.

rigging

The planned movement of material, equipment, and loads from one place to another using ropes, chains, hoists, or other types of equipment.

rigging link

A type of rigging connector that typically has two holes.

right angle

A 90 angle.

right cylinder

A cylinder that has generating lines perpendicular to the bases, with its ends closed to form two circular surfaces.

right triangle

A triangle that has a 90 angle.

ring

A type of network topology that resembles a bus network with joined, rather than terminated, ends.

ring gasket

A type of gasket normally used with raised face flanges. A ring gasket covers only the raised portion of the flange, fitting within the ring of bolts/studs.

ring terminal

A crimp-on terminal that has a circular, ring-like tongue.

ring type joint

A joint constructed with a groove machined into the face of each flange that matches the groove in its companion flange. When the flange is tightened, a metal ring is used instead of a gasket to seal the flange. These types of joints are most commonly found in high pressure systems.

ring-joint flange

A flange that has a raised area around the center opening with a flat-bottomed groove machined into the center of the raised area.

ripple marks

Sedimentary structures which indicate agitation by water (either current or waves) or wind.

rise time

The time taken for a pulse or output voltage step to change from 10% to 90% of its maximum or final value. An oscilloscope cannot accurately display pulses with rise times faster than its own.

riser

The area of a cat cracker in which the cracking reaction takes place.

risers

Points on the commutator of a DC motor where the actual connections between the armature windings and the commutator segments are made.

RMS voltage

Root Mean Square voltage; the voltage displayed by an AC voltmeter, a value equal to 0.707 x Emax, where Emax is the maximum value of the AC voltage.

road octane number

The average of the research octane number and the motor octane number [(R + M) ÷ 2]; the octane number given on gasoline pumps.

road-grade asphalts

Asphalts that are suitable for use in paving.

robustness

The measure of a control loop's stability under all operating conditions.

rock

A rock is a naturally occurring solid aggregate of minerals, or mineraloids.

rock formation, formation

Rock formation refers to specific sedimentary strata, or other rock unit, in stratigraphic and petrologic studies.

rock matrix acidizing

Rock matrix acidizing involves injecting acid into the well, penetrating the rock pores at pressures below the fracture pressure. This stimulates the well to improve the hydrocarbon flow.

rock texture

The sizes and shapes of grains, the relationships between neighboring grains, and the orientation of grains within a rock.

rock texture, texture

Rock texture refers to the sizes and shapes of grains, the relationships between neighbouring grains and the orientation of grains within a rock.

roll-off

The roll-off frequency is the frequency above which a filter generates significant attenuation. Empirically this is regarded as the point where the amplitude is reduced by 3 dB, or the power by 6 dB.

rolling contact bearing

A bearing that uses balls or rollers to overcome friction. Can oppose radial or axial thrust, or a combination of the two. Also called an anti-friction bearing.

rollover

Rollover is the cumulative effect of downthrown thickening, slumping and rotation.

rollover anticlines, fault rollovers

Rollover anticlines and fault rollovers form when the hanging wall slumps into the low pressure extensional zone associated with listric normal faulting.

rollovers

Components on each end of a tank truck's spill dam that help prevent the tank from being punctured and valves and vents from being damaged if the truck rolls over.

RON

Research octane number; indicates gasoline performance under mild operating conditions.

root

The quantity that when multiplied by itself a specific number of times equals a given number.

rootlet horizons

A rootlet horizon refers to the layer of soil (within a soil profile) where the majority of plant roots, particularly fine rootlets, are concentrated; commonly this is considered the topsoil layer where roots actively absorb nutrients and water from the soil.

rose diagram

A circular distribution plot of directional data (azimuth frequency), plotting lines at each of the 360 degrees of a compass distribution.

rotameter

A type of flow meter, consisting basically of a tapered tube and a float, that measures and indicates flow rate.

rotary

A circular or turning motion.

rotary air heater

An air heater that operates by rotating heated surfaces through the air being supplied to a boiler.

rotary pump

A type of positive displacement pump containing screws, gears, or similar devices that move fluid with a rotary motion.

rotary sidewall core

A sidewall core sample acquired from the side of the borehole by using a diamond-tipped drill to mechanically cut individual plugs, which are then broken off and pulled from the borehole wall.

rotary sidewall coring

The rotary sidewall coring tool was developed to recover sidewall core samples without the shattering impact of the percussion system. Suitable for hard to friable rock, the rotary sidewall corer uses a diamond-tipped drill to cut individual plugs from the sidewall.

rotary table

The revolving or spinning section of the drill floor that provides power to turn the drill string in a clockwise direction. The rotary motion and power are transmitted through the kelly bushing and kelly to the drill string.

rotating field generator

A type of AC generator in which direct current is fed to the rotor and the output voltage from the generator is taken directly from the stator coils.

rotation

A circular or turning motion.

rotational slides

Rotational slides move along a surface of rupture that is curved and concave.

rotor

The movable or rotating part of a motor, pump, turbine, or AC generator. In a centrifugal pump, it usually includes the impeller, shaft, and all parts between the bearing housings and impeller.

roughneck

A roughneck is a drill floor hand, or member of the drilling crew, who works under the direction of the driller to make or break connections as drill pipe is tripped in or out of the hole.

round the shoulders

Round the shoulders refers to reducing the sharpness of the waveform peaks.

round trip

The process of removing the entire drill string from the borehole (normally to replace a component such as the bit), followed by running it back down to the bottom. In metering, the movement of a displacer completely in one direction and back to the starting point.

route of exposure

The means by which material may gain access into the body, such as breathing, swallowing, or entering through the skin or eyes.

routes of entry

The means by which material may gain access into the body, for example, breathing, swallowing, or entering through the skin or eyes.

royalty

Payment made to the owner of oil or gas rights equal to a percentage of production ("in kind") or equivalent free of all costs.

RS-232

A PC communication standard for connecting two serial devices together.

RS-232 protocol

A standard communications protocol that governs the transmission of data through networks.

RS-485 protocol

A standard communications protocol that governs the transmission of data through networks.

RSLinx

Allen-Bradley's software for communicating between PLCs and PCs.

RSLogix

Allen-Bradley's PLC programming software.

RTD

Resistance Temperature Detector. A type of sensor that uses a resistor whose resistance is directly related to its temperature.

rubber tape

A splicing tape that is used to replace original insulation made of rubber. Also called latex tape.

rugosity, borehole rugosity

The roughness, unevenness, or irregularity of a borehole wall.

run

In electrical work, a continuous installation of conduit from start to termination. In quality control, a pattern of instability on a control chart with a group of data points above or below the centerline. In oil production, the volume of crude oil sold or transferred from a lease tank to pipeline or tank truck.

rundown tank

A tank that receives a product or a blend component from a process unit and provides intermediate storage.

rundown tanks

Storage tanks that receive blend components from process units.

rung

The horizontal lines and the devices connected by them that make up a "row" on a ladder diagram.

runout test

A procedure for determining if a pump shaft is bent or out of round.

rupture disc

A fail-safe pressure relief device made of metal that is designed to burst at a preset pressure, protecting equipment from excessive pressure.

rupture discs

Protective devices that are designed to break when pressure inside the exhaust hood rises above atmospheric pressure.

rupture disk

A disk installed in a flange fitting that ruptures when pressure becomes too great; another type of relief device.