Discover the IHRDC Energy Glossary_beta

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O

OA

A designation for a self-cooled power transformer; abbreviation for "oil to air."

OA/FA

A designation for a self-cooled/forced air-cooled power transformer; abbreviation for "oil to air/forced air."

OD

Outside diameter; the length of a straight line that passes from one side on the outside surface of a pipe, through the center of the pipe to the other side of the outside surface of the pipe

OJT Checklist

A document that identifies the on-the-job training (OJT) steps that a trainee must follow to accomplish a performance objective.

The Offshore Petroleum Industry Training Organization is an industry-owned skills body for the energy industry, offering a range of services and products to meet international skills needs and support workforce development.

OR Gate

A digital logic gate that produces a HIGH output (1) if one or more of its inputs are HIGH (1). If neither input is HIGH, the output is LOW (0).

OSHA

Occupational Safety and Health Administration.

Object Library

The icons that graphical software tools made available for building programs

Objectivity

Objectivity is the quality, or character, of being objective: lack of favoritism toward one side or another.

Observation [evidence]

Employees are directly observed doing their jobs.

Obtuse angle

Any angle between 90 and 180

Occupational exposure

As it applies to bloodborne pathogens, reasonably anticipated skin, eye, mucous membrane or parenteral (such as piercing of the skin) contact with blood or other potentially infectious materials that may result from the performance of an employee's duties.

Octal Numbering System

The numbering system based on powers of eight.

Octane

A number or rating that measures a fuel's anti-knock properties. Also, a paraffin hydrocarbon that is a liquid at atmospheric conditions.

Octane Giveaway

Deliberately blending a product to obtain an octane number that is above spec.

Octane Number

A measure of the antiknock properties of a gasoline.

Octane Pool

The octane numbers and the quantities of all of the gasoline blend components available within a refinery.

Octane rating

A general indication of a gasoline's quality; a measure of how resistant a gasoline is to engine knock.

Off-delay Time Delay Relay

A time delay relay in which the delay starts when the coil is de-energized, or turned off

Offline

A state in which a PC or programming terminal is used to display, create, or edit a PLC program stored in its own memory. Also, a field communicator or laptop function that enables configuration data to be uploaded from and downloaded to smart field devices or a DCS.

Offset

The error remaining after proportional control has stabilized a process variable following an upset; the difference between the final steady-state condition and the original set point value.

Offset Fitting

A type of fitting that is used to change the level of a conduit run

Offset Well Location

A potential drill location adjacent to an existing well.

Offset voltage

A voltage that is introduced at the input of an op amp in order to produce an output of exactly zero volts.

Ohm

The unit of measurement of electrical resistance. One ohm is defined as the resistance that allows one ampere of current flow in a circuit with a source voltage of one volt. The Greek letter omega (Ω) is typically used as an abbreviation.

Ohm's Law

The definite relationship between voltage, current, and resistance in an electrical circuit, stating that current equals voltage divided by resistance (I = E/R). Electric current is directly proportional to voltage and inversely proportional to resistance.

Oil Allowable

The regulated volume of oil which can be produced over a designated period of time.

Oil Base Drilling Mud

An oil base drilling mud is an invert-emulsion mud, or an emulsion whose continuous phase is oil.

Oil Base Mud

An invert-emulsion drilling mud whose continuous phase is oil.

Oil Fluorescence

Fluorescence that derives largely from the aromatic hydrocarbon fraction of oil. The emission is strongly influenced by the chemical composition (e.g., fluorophore and quencher concentrations) and physical characteristics (e.g., viscosity and optical density) of the oil.

Oil Sands or Tar Sands

Sandstone deposits that are highly saturated with natural bitumen.

Oil Shales

Shale, siltstone, and marl deposits that are highly saturated with kerogen.

Oil sands

Geologic formation comprised predominantly of sand grains and bitumen, a highly viscous form of crude oil.

Oil-Wet

The preference of a solid surface to be in contact with an oil phase rather than a water or gas phase. Wettability is the tendency of one fluid to spread on, or adhere to, a solid surface in the presence of other immiscible fluids.

Olefin

A hydrocarbon with carbon atoms connected in a straight chain, two of which are linked by a double bond. A high-octane, unstable component of the light ends produced in a cat cracking unit that is reacted with isobutane in the alkylation process.

Olefins

Highly reactive, unsaturated hydrocarbons that can be used in alkylation units to produce high-octane gasoline and as petro-chemical feedstocks.

On-delay Time Delay Relay

A time delay relay in which the delay starts when the coil is energized, or turned on

On-the-job training (OJT)

Formal, structured training for acquiring the skills and knowledge to perform a job that takes place in the actual work environment.

On/Off Control

A control algorithm that causes an output signal to be either on or off

Once-through Boiler

A boiler in which water goes through only once without recirculating.

Once-through System

A type of circulating water system in which the water from a large source, such as a lake, flows through the system one time and is returned to the source

One-Slot Addressing

An I/O addressing scheme where each slot in the I/O rack is defined as a 16-bit group

One-hole Panelboard Connector

A mechanical connector that is designed for terminating a circuit at a panelboard or breaker box

One-time Fuse

A fuse that is discarded after it has blown

Online

The state in which the PC or other programming terminal is used to display, create or edit a PLC program while the program resides in the PLCs memory

Online Programming

The process of modifying a PLC program while the processor is in the "Run" mode

Opacity

A measure of the lack of penetration of light through a substance.

Opacity Meter

An instrument that measures the concentration of suspended particles in a gas

Open

A break that stops current flow in an electrical circuit; a circuit in which resistance is so great that there is no current flow.

Open Circuit

A break in an electrical conductor or a circuit with resistance so great that there is no current flow. Can occur when fault current is not high enough to trip circuit breakers or blow fuses.

Open Heater

A heater in which condensate or feedwater is mixed together with steam

Open Hole

Open hole is the uncased portion of a well.

Open Impeller

An impeller whose vanes are not enclosed by shrouds

Open Software

Software that is designed to run on standard computer platforms independently of proprietary equipment. Some open software can share information with other open programs

Open System (Network)

A system that is not proprietary, but rather uses a standard made available to many vendors. Some examples are PROFIBUS and TCP/IP.

Open loop gain

The designed gain of an op amp; the gain listed on op amp data sheets.

Open radial fan

A type of radial blade fan in which the blades are not enclosed; used for extremely abrasive service and for material handling.

Open season

The process whereby the developer of a greenfield UGS facility or the owner/operator of an existing UGS facility solicits the interest of customers regarding a commitment to and pricing of various gas storage services

Open-loop transresistance

In a transimpedance or current feedback amplifier, it is the ratio of change in dc output voltage to the change in dc current at the inverting input.

Open-loop voltage gain

The ratio of change in output voltage to the change in voltage across the input terminals. Usually the dc value and a graph showing the frequency dependence are shown in the data sheet.

Opening Gauge

Measurement of oil level in lease tank prior to a transfer or run. May be called top gauge.

Operating Coil

The conducting coil of a magnetic contactor or relay that becomes an electromagnet when current flows through it, working to close contacts.

Operating radius

The horizontal distance from the centerline of a crane's rotation to the center of the vertical hoist line or load block, measured with the load freely suspended

Operating temperature

Temperature over which the op-amp may be operated. Some of the other parameters may change with temperature, leading to degraded operation at temperature extremes.

Operational amplifier

A high-gain, DC amplifier that can be configured to perform many functions. Commonly called an op amp.

Operator

The entity responsible for managing operations in a field or undeveloped acreage position.

Operator Interface

The equipment a machine or process operator uses to monitor and control the machine or process

Opposed blade damper

A type of damper that operates with alternate blades turning in opposite directions.

Optical Analyzers

Analyzers that determine properties of materials by measuring the interactivity of electromagnetic radiation with matter

Organic Material

Material composed of carbon based molecules

Organic Solids

Solids composed of living or formerly living matter, such as fish and plant material.

Organic chemistry

The branch of chemistry dealing with compounds that contain carbon.

Organic peroxide

An organic compound that contains the bivalent -O-O- structure and which may be considered to be a structural derivative of hydrogen peroxide where one or both of the hydrogen atoms has been replaced by an organic radical.

Orientation Data

Orientation data shows where the dipmeter tool is located downhole with respect to vertical and geographic coordinates.

Orifice Fitting

A device designed to hold an orifice plate in a meter tube.

Orifice Flow Constant (C')

Pronounced C-Prime. Part of the flow rate formulas. Consists of eleven factors which affect orifice flow rates.

Orifice Meter

An instrument used to measure the flow of fluids in a pipe.

Orifice Plate

A flat metal plate with a carefully machined circular, square-edged or beveled-edge hole, inserted in a pipeline to create a differential pressure that can be measured and converted to an indication of flow. Can also be used for pulsation control or pressure drops to create a sidestream.

Origin of Installation

A reference to the main service drop bringing power into a plant

Original drawings

Drawings created by a drafting person based on notes and sketches provided by the architect or engineer who designed the project

Orthographic projection

A type of drawing, sometimes called a Multiview projection, in which different views of the same object are shown

Oscillator

A device or circuit that converts a constant power into a fluctuating current or signal.

Oscilloscope

A device for viewing oscillations by displaying them on a screen.

Other potentially infectious materials

(1) The following human body fluids: semen, vaginal secretions, cerebrospinal fluid, synovial fluid, pleural fluid, pericardial fluid, peritoneal fluid, amniotic fluid, saliva in dental procedures, any body fluid that is visibly contaminated with blood, and all body fluids in situations where it is difficult or impossible to differentiate between body fluids; (2) Any unfixed tissue or organ (other than intact skin) from a human (living or dead); and (3) HIV-containing cell or tissue cultures, organ cultures, and HIV- or HBV-containing culture medium or other solutions; and blood, organs, or other tissues from experimental animals infected with HIV or HBV.

Out of Phase

A situation in which the voltages at the top or bottom of the primary and secondary windings on a transformer are of opposite polarity.

Outage

A measurement taken from the surface of a liquid to a reference point at the top of the container. Also, a space for expansion created in a sample cylinder by bleeding displacement fluid, required for safe handling of NGL samples.

Outlet damper

A damper that is located on the outlet side of a fan and used to control the air flow out of the fan.

Outliers

A plotted data point that falls outside of a control limit on a control chart

Outlying Data

Outlying data is data that lies an abnormal distance from other values in a random sample from a population.

Output

Data provided by an EFC or other instrument.

Output Device

A device that acts as a load connected to an output module in a PLC

Output Image Table

Output Image Table The part of data memory in which the current states of the real outputs are stored

Output current

The amount of current that is drawn from the op-amp output. Usually specified as an absolute maximum rating, not for long term operation at the specified level.

Output impedance

The frequency dependent small-signal impedance that is placed in series with an ideal amplifier and the output terminal.

Output resistance

The dc resistance that is placed in series with an ideal amplifier and the output terminal.

Outside micrometer

A micrometer used for measuring outside dimensions; the reading is taken between a fixed anvil and a movable spindle

Oval Gear Meter

A type of flow meter that uses gears to trap and measure specific quantities of liquid

Overall Extended Height

The distance from the floor to the highest point on a forklift when the mast and the forks are fully raised

Overbalance

Overbalance is the amount of pressure (or force per unit area) in the wellbore that exceeds the pressure of fluids in the formation.

Overburden Pressure

Overburden pressure, also termed lithostatic pressure, confining pressure or vertical stress, is the pressure or stress imposed on a layer of soil or rock by the weight of overlying material.

Overcracking

Cracking hydrocarbon chains beyond the desired degree.

Overcurrent Relay

A relay designed to operate when current is higher than desirable in part of a transmission and distribution system.

Overcurrent protection

Protection achieved by de-energizing a circuit whenever the current exceeds a predetermined value, using devices such as fuses, circuit breakers, and magnetic relays.

Overdetermined System

An overdetermined system is the situation when there are more equations than the number of unknowns.

Overfill

The situation created when a storage tank is filled to a specified level that is usually close to the tank's rated capacity.

Overfractionation

A condition that results in the excessive use of steam and other utilities to produce products

Overhead Product

The product that is condensed from the vapor that flows out of the top of a distillation column.

Overhead guard

A forklift component that protects the forklift operator from falling objects.

Overload Device

A device inside a motor controller that senses excessive levels of current and operates to create a break in the motor circuit

Overloading

A condition in which the vapor rising up a column is impeded by the liquid flowing down the column

Overpressure

A condition when fluid pressure in a formation is higher than estimated from the normal hydrostatic fluid gradient for a given depth. Overpressure is a drilling hazard responsible for many well blowouts.

Overpressured Formation

An overpressured formation is when a fluid pressure is higher than estimated from the normal hydrostatic fluid gradient for a given depth.

Override Control

A control function that bypasses normal control algorithms or parameters in order to maintain safe or acceptable system operation when certain conditions occur

Overshoot

The distance that a process variable passes the set point when the control loop responds to error

Overshoot factor

The ratio of the largest deviation of the output voltage from its final steady-state value to the absolute value of the step after a step change at the output.

Overshot

An overshot is a downhole tool used in fishing operations to engage on the outside surface of a wireline tool. A grapple on the overshot grips the fish, allowing application of tensile force and jarring action. If the fish cannot be removed, a release system within the overshot allows the overshot to be disengaged and retrieved.

Overspeed

A mechanical condition that occurs when rotating machinery, such as a turbine, exceeds its designed operating speed.

Overspeed Governor

A protective device that automatically energizes trip circuits to trip the turbine valves and stop steam flow to a turbine during an overspeed condition

Overthrust Block

An overthrust block is pushed by compressional forces over the offsetting beds, often during reverse or thrust faulting episodes.

Overvoltage

Higher than normal voltage.

Overvoltage Reflections

High voltage spikes commonly created as a result of long cabling or short PWM rise times.

Oxidation

The combination of a substance with oxygen to form a new substance; a reaction in which a substance loses electrons.

Oxidation Inhibitor

An additive that helps prevent gum from forming in diesel fuel if the fuel is exposed to oxygen while it is in storage.

Oxidation Reduction Potential

The electrochemical potential that exists in a chemical reaction involving an exchange of ions. Abbreviated as ORP. Also called a redox reaction

Oxidizer

A chemical (other than a blasting agent or explosive) that initiates or promotes combustion in other materials, causing fire either of itself or through the release of oxygen or other gases. It presents a fire and explosion hazard on contact with organic compounds and other oxidizable substances.

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OA