Instrumentation, Process Control, and Electrical Safety Flashcards

66 vocabulary flashcards covering process control principles, P&ID standards, safety systems, hazardous classifications, electrical safety, and Ohm's Law.

Process Control

A system that combines measuring and controlling instruments into an arrangement capable of automatic remote action.

Repeatability

The degree to which an element provides the same result with successive occurrences of the same condition.

ON/OFF Control

The simplest and most common basic control strategy.

Final Element

A device that receives a control signal and regulates the amount of material or energy in a process.

Hysteresis

A property of physical systems that do not react immediately to the forces applied to them or do not return completely to their original state.

Proportional Control

A control strategy that uses the difference between the setpoint and the process variable.

Setpoint

The desired value at which the process should be controlled.

Static Characteristics

Characteristics of an element that describe the operation of the element at steady-state conditions when the process is not changing.

Closed Loop

A control system that provides feedback to the controller on the state of the process variable.

Process

The transformation of raw materials into end products.

Continuous Process

A process characterized by continuous material flow with no defined end, such as oil refining.

Batch Process

A process characterized by defined start and end points that produce discrete quantities.

Open-Loop Control

A control strategy in which the control action is taken regardless of the current process conditions.

Basic Closed-Loop System Components

A system made up of three main elements: a measurement device, controller, and actuator.

Controller Main Function

To compare the measured process value with the setpoint and calculate an output.

Actuator

A final control device, such as a control valve, that responds to a signal to regulate flow or energy.

PID Control

The most common process control strategy described in the material.

Cascade Control Secondary Loop

A control loop designed to react faster to disturbances before the primary variable is significantly affected.

Piping and Instrumentation Diagram (P&ID)

A schematic diagram showing the relationship between instruments, controllers, piping, and system equipment.

P&ID Tag Letter 'I'

The letter used for electrical current in an instrument tag balloon.

P&ID Tag Letter 'W'

The letter used for water flow in an instrument tag balloon.

ISA

The organization that has developed a comprehensive standard for instrumentation symbols.

P&ID Letters 'TV'

Letters on a P&ID representing 'temperature valve'.

P&ID Controller Symbol 'TIC'

Letters on a P&ID controller symbol standing for 'temperature indicating controller'.

P&ID Tag Letter 'A'

A letter used as a modifier representing an alarm in an instrument tag balloon.

Balloon (P&ID)

A circular symbol on a P&ID used to identify the purpose of an instrument or device.

P&ID Letters 'TSH'

Letters on a P&ID representing 'temperature switch high'.

Pneumatic-System P&ID Starting Point

The air compressor, which is the recommended starting component when reading a pneumatic-system P&ID.

P&ID Legend

The reference section used to identify the specific meaning of symbols on a P&ID.

Accumulator

A tank or storage device for air or fluids in a pneumatic or fluid system.

Rupture Disc

A safety device used to prevent damage in pipelines and pressure vessels due to excessive pressure.

Tank Car/Truck Safety Relief Valves

Valves approved for chemical transportation applications where standard safety valves are not approved.

Fuel Safety Shutoff Valve

A special spring-actuated valve used to stop the fuel flow to a burner system.

Blowdown Ring

A component on a safety relief valve, sometimes called a huddling chamber, used to adjust the valve opening speed.

Combustible Gas Detector

A hazardous atmosphere detector used to measure low concentrations of combustible gases and vapors in the atmosphere.

Runaway Chemical Reaction

An uncontrollable reaction that can occur due to loss of cooling or a reaction rate exceeding cooling capacity.

ASME International

The body that establishes codes to which safety valves, relief valves, and safety relief valves must conform.

Flame Detector

A device that provides a usable signal to a burner control system by detecting the presence of a flame.

Boiler Safety Valve Capacity

The amount of steam, measured in lb/hr, that a boiler safety valve is capable of venting at its rated pressure.

Intrinsic Safety

A protection technique designed to prevent fires or explosions by restricting electrical energy that could create sparks or heat.

Risk Assessment

A process performed in a hazardous environment to identify hazards so that risks can be properly mitigated.

ATEX and NEC (NFPA 70)

The two main hazardous-area classification systems described in the material.

Class I Hazardous Environment

A hazardous area classification associated primarily with flammable gases and vapors.

Class II Hazardous Environment

A hazardous area classification associated primarily with combustible dusts.

Combustible Dust Example

Flour, cited as an example of a combustible dust in process environments.

Intrinsically Safe Barrier

A special circuit device that provides isolation or limits voltage and current to hazardous-area sensor circuits.

Optic Isolator

A component commonly containing a light-emitting diode and a light-sensitive transistor.

Pressurized Electrical Panel

An enclosure pressurized with compressed air to create positive pressure and reduce the likelihood of dust entering.

Keyed Bypass Switch

A switch used in a pressurized intrinsically safe enclosure to keep power on temporarily during maintenance or troubleshooting.

Check-Weigher Load Cell

The component in a check-weigher system whose voltage and current are limited by an intrinsically safe barrier.

Electricity

The flow of electrons through a conductor or circuit.

Proton

A subatomic particle that carries a positive charge.

OSHA Electrical Safety Strategy

De-energization, mandated by OSHA above all other strategies to minimize risk of injury from electrical hazards.

Current

The amount of electricity flowing in a conductor.

Ladder Placement Rule

For a $12\text{ ft}$ tall building, placing the ladder base $3\text{ ft}$ away from the building side (4:1 height-to-base ratio).

Conductor Valence Electrons

Atoms with valence electron counts of 1 to 3 electrons, typical of conductor materials.

Magnetism (Current Generation)

The method commonly used to produce electrical current in a generator or alternator.

OSHA High Voltage Threat Threshold

$50\text{ volts}$, the voltage level at which OSHA establishes energized parts pose a threat to people.

Equipment Grounding Conductor

A conductor providing a low-impedance path for fault current to return to service and facilitate overcurrent protection operation.

Class B Fires

Fires involving fuels such as grease, combustible liquids, or gases.

Ventricular Fibrillation Threshold

$75\text{ milliamperes}$, the current level at which the heart runs the risk of going into ventricular fibrillation.

Ohm's Law Resistance Calculation

For a $240\text{-V}$ circuit with $20\text{ A}$ of current flow, the connected resistance is $R = \frac{240\text{ V}}{20\text{ A}} = 12\text{ ohms}$.

Ohm's Law Voltage Calculation

For an apparent resistance of $15\text{ Ohms}$ and $8\text{ A}$ of current, the connected voltage is $E = 8\text{ A} \times 15\text{ Ohms} = 120\text{ volts}$.

Short Circuit

A closed circuit allowing current to bypass the load, resulting in very low resistance (ohms) and an extremely high amount of current (amperes).

Voltage

The pressure or driving force (electromotive force / potential difference) that pushes and pulls electrons through a circuit.

Applied Voltage Calculation

For a total resistance of $25\text{ ohms}$ and $4\text{ amperes}$ of current, the required voltage is $E = 4\text{ A} \times 25\text{ ohms} = 100\text{ V}$.