PURPOSE OF MAINTENANCE

TYPES OF FAILURE

Types of failure that inability to meet the specified performance standard

a physical condition which indicates that the failure process has started

Failure is not apparent until the function is attempted

TYPES OF MAINTENANCE

repairs are made after the equipment is failed and can not perform its normal function anymore

Type of maintenance that uses stitch-in-time procedure and incorporates

Prevention is better than cure

machinery conditions are periodically monitored and this enables the maintenance crews to take timely actions, such as machine adjustment, repair or overhaul

It converts one standardized transmission signal to another form of signal

converts a reading from a sensor or transducer into a standard signal and transmits that signal to a monitor or controller

signals produced by changing the air pressure in a signal pipe in proportion to the measured change in a process variable. The common industry standard pneumatic signal range is 3–15 psig

The most common standard electrical signal is the 4–20 mA current signal

discrete levels or values that are combined in specific ways to represent process variables and also carry other information, such as diagnostic information

device that receives data from a measurement instrument, compares that data to a programmed setpoint, and, if necessary, signals a control element to take corrective action.

test during which known values of measurand are applied to the transducer and corresponding output readings are recorded under specified conditions

the region between the limits within which a quantity is measured, received or transmitted, expressed by stating the lower and upper range values.

lower end of the range

difference between the upper and lower range values

Capability of the instrument

ratio of the error to the full scale output or the ratio of the error to the output, expressed in percent span or percent reading, respectively

Permissible deviation from a specified value; may be expressed in measurement units, percent of span, or percent of reading

the property of a result of a measurement whereby it can be related to appropriate standards, generally national or international standards, through an unbroken chain of comparisons

composed of any combination of sensor (s), logic solver (s), and final elements(s). designed to prevent or mitigate hazardous events by taking a process to a safe state when predetermined conditions are violated.

safety function with a specified (SIL) that is implemented by the SIS to achieve or maintain a safe state

measure of safety system performance, in terms of probability of failure on demand (PFD

force divided by the area over which that force is applied

anything that changes or tends to change the state of rest or motion of a body

the number of unit squares equal to the surface of an object

pressure due to the weight of the atmosphere above the point where it is measured

Actual height of a column of liquid. A container or vessel can be any shape, but head is only determined by the height of the liquid.

The pressure due to the head of a liquid column. Frequently, this is referred to as pressure head.

pressure applied to a confined static fluid is transmitted with equal intensity throughout the fluid

WHICH IS NOT COMMON PRESSURE SCALES

Difference in pressure between two measurement points in a process

Pressure measured with a perfect vacuum as the zero point of the scale

Pressure less than atmospheric pressure measured with atmospheric pressure as the zero point of the scale.

Pressure measured with atmospheric pressure as the zero point of the scale

Device for measuring pressure with a liquid-filled tube.

A manometer with a reservoir serving as one end and the measuring column at an angle to the horizontal to reduce the vertical height

Clear tube bent into the shape of an elongated letter U

A manometer with a vertical glass tube connected to a metal well, with the measuring liquid in the well at the same level as the zero point on the tube scale

Manometer used to measure atmospheric pressure

Mechanical pressure sensor consisting of a thin, flexible disc that flexes in response to a change in pressure

A mechanical pressure sensor consisting of a hollow tube formed into a helical, spiral, or C shape.

A mechanical pressure sensor consisting of a one-piece, collapsible, seamless metallic unit with deep folds formed from thin-wall tubing with an enclosed spring to provide stability, or with an assembled unit of welded sections

device that converts input energy into output electrical energy.

Pressure transducer with a power supply and a device that conditions and converts the transducer output into a standard analog or digital output.

A diaphragm pressure sensor with a strain gauge as the electrical output element. Resistance pressure transducers are the most widely used electrical pressure transducers.

diaphragm pressure sensor with a capacitor as the electrical element.

Diaphragm pressure sensor combined with a crystalline material that is sensitive to mechanical stress in the form of pressure.

METHODS OF PRESSURE MEASUREMENT

READING MENISCUS: If the meniscus is _ , use the _ of the meniscus as the reading

READING MENISCUS: If the meniscus is _ , use the _ of the meniscus as the reading

PRESSURE SWITCH COMPONENTS

impulse line filled with noncondensing gas, used in level measurement applications

impulse line filled with fluid that is compatible with the pressure-measuring device.

hydraulic pressure-calibrating device that includes a manually operated screw press, a weight platform supported by a piston, a set of weights, and a fitting to connect the tester to a gauge

surge tank that may be installed in a wet leg to prevent volume changes from forcing the fluid into the process as well as protecting the sensing element from high temperatures as with steam applications.

forms a water seal, or trap, between the sensor and the process, thus preventing high-temperature steam from entering the gauge

can be added to inlet lines to limit pulsations and surges

an instrument that is used to indicate temperature.

Lowest temperature possible, where there is no molecular movement and the energy is at a minimum.

Movement of thermal energy from one place to another.

Heat transfer that occurs when molecules in a material are heated and the heat is passed from molecule to molecule through the material.

Heat transfer by the movement of gas or liquid from one place to another caused by a pressure difference

Heat transfer by electromagnetic waves emitted by a higher-temperature object and absorbed by a lower-temperature object

thin glass reservoir that holds the liquid.

made of annealed glass. The type of glass used is chosen based on the temperature range of the device so as to minimize the effects of expansion and contraction of the tube.

contains an ice point reference that can be used for calibration purposes if this temperature is not included within the range of the main scale.

Its purpose is to shorten the total stem length needed to reach the main scale. 

provided at the end of Liquid-in-glass thermometers, and is used to prevent the buildup of pressure if the temperature of the liquid rises past the top of the scale.

An electrical thermometer consisting of two dissimilar metal wires joined at one end and a voltmeter to measure the voltage at the other end of the two wires

exposed to the process where the temperature measurement is desired.

Controlling or accurately measuring the temperature at _ is essential for accurate temperature measurement with a thermocouple.

Controlling or accurately measuring the temperature at _ is essential for accurate temperature measurement with a thermocouple.

An electrical thermometer consisting of a high-precision resistor with resistance that varies with temperature, a voltage or current source, and a measuring circuit

A temperature-sensitive resistor consisting of solid-state semiconductors made from sintered metal oxides and lead wires, hermetically sealed in glass.

closed tube used to protect a temperature instrument from process conditions and to allow instrument maintenance to be performed without draining the process fluid.