Steam Fitting Definitions Unit 4

Front 1

Ambient Temperature

Back 1

The temperature of the air surrounding the equipment

Front 2

Atmosphere

Back 2

A unit approximately equal to the pressure at sea level (14.7 psia)

Front 3

Atmospheric Pressure

Back 3

The pressure exerted upon the earth’s surface by the weight of the extending up into the atmosphere a distance of approximately 50 miles (atmosphere pressure at sea level = 14.7 psia) a) AP- atmospheric pressure b) Barometric pressure at sea level - 29.92” of mercury c) One atmosphere - 14.7 psia

Front 4

Barometer

Back 4

A device used to measure atmospheric pressure (Figure 24); reads in inches pf mercury. a) Mercury barometer b) Aneroid barometer

Front 5

Density

Back 5

The weight of a unit volume of a substance ( for example, the density of water is 62.4 lbs per cu ft

Front 6

Differential pressure

Back 6

The difference in pressure between two points in a system. For example, the difference in pressure between the upstream and downstream taps of an orifice plate; used to measure volume passing through the orifice

Front 7

Differential Temperature

Back 7

The difference in temperature between 2 opposing masses; used to describe the potential that exists for heat transfer.

Front 8

Erosion

Back 8

The wearing away effect on a valve disc plug, seat or any other fitting or apparatus.

Front 9

Head

Back 9

A comparison of a pressure with the height of a column of liquid that would exert an equal pressure.

Front 10

Head pressure

Back 10

The pressure available at the outlet side of a pump or inlet side of a flow conducting system; expressed in feet of head. Feet of head is the height of a column of water that can be supported by a pump against standard atmospheric pressure.

Front 11

Latent Heat

Back 11

Change in heat content of a substance when it’s physical state is changed without a a change in temperature

Front 12

Sensible Heat

Back 12

That heat which, when added or subtracted, results in a change of temperature, but not a change in a state.

Front 13

Specific Heat

Back 13

The heat required to raise a unit of mass of a substance through a degree of temperatur difference. Also, the ratio of the thermal capacity of a substance to that of water at 59˚F (15˚C)

Front 14

Heat Transfer

Back 14

Flow of heat by radiation, convection or conduction. This term is sometimes used to mean rate of heat transfer.

Front 15

Heating Load

Back 15

The amount of energy (in Btuh required for water or space heating

Front 16

Heat Loss

Back 16

The transfer of heat from a contained space to the atmosphere surrounding it. Heat loss is the result of thermal conductivity through walls, windows, roofs and other building envelope components, as well as infiltration losses due to the exchange of inside air with outside air.

Front 17

Hg

Back 17

Mercury

Front 18

Hydronics

Back 18

The science of heating and cooling with liquids

Front 19

Infiltration

Back 19

The exchange of warm air inside building with the cold air outside. Natural infiltration takes place as a result of air leakage through minute openings in walls, windows, doors and ceilings. Controlled infiltration occurs due to the forced exchange of a mechanical system. Infiltration is expressed in air changes per hour or fractions thereof. For natural infiltration in newly constructed homes, ir changes should be calculated at .50 per hour

Front 20

Infiltration Losses

Back 20

The loss of heat energy due to infiltration, which is expressed in Btuh. Infiltration losses are calculated from air changes per hour, differential indoor/outdoor temperature and the heat carrying capability of the lost air

Front 21

Insulation

Back 21

A material with low thermal conductivity. Used to reduce heat losses

Front 22

Inert

Back 22

Not acted upon chemically by the surrounding environments. Nitrogen and carbon dioxide are examples of constituents of natural gases; they dilute the gas and do not burn and thus add no heating value.

Front 23

Estimated Design Load

Back 23

The sum of the useful heat transfer, plus the heat transfer from or to the connected piping, plus heat transfer occurring in any auxiliary apparatus connected to the system. (Btu per hour or equivalent direct radiation).

Front 24

Estimated Maximum

Back 24

The calculated heat transfer that the system will be called upon to provide.

Front 25

Negative pressure

Back 25

A pressure less than atmospheric pressure

Front 26

non-combustible

Back 26

Generally, a substance or gas that will not burn

Front 27

Oxygen

Back 27

A gas occurring in the atmosphere, of which it forms about 21% by volume. Oxygen is chemically very active and is necessary for combustion. The combination of the oxygen with other substances generally produces heat.

Front 28

Pressure

Back 28

Force per unit area.

Front 29

Pressure differential

Back 29

The difference in pressure between the supply main and the return main measured across a trap.

Front 30

Pressure Loss

Back 30

The loss of fluid pressure between any two points in a flow conducting system, expressed in pounds per square inch (psi). The loss of pressure is caused by friction against the tubing walls and is further influenced by the tubing size, length and texture of the inside wall of the tube. Pressure loss is also influenced by the temperature by the temperature and viscosity of the fluid.

Front 31

psi

Back 31

Pounds per square inch (pressure above atmospheric pressure)

Front 32

psia

Back 32

Pounds per square inch absolute (the sum of gauge pressure and atmospheric pressure)

Front 33

psig

Back 33

Pounds per square inch gauge (pressure above atmospheric pressure).

Front 34

Specific Gravity (Liquids and solids)

Back 34

The comparisons of the weight of a volume liquid or solid to the weight of an equal volume of pure water.

Front 35

Specific gravity (Gases)

Back 35

The comparisons of the weight of a volume of gas at STP compared to the weight of an equal volume of dry air at STP

Front 36

Stack loss

Back 36

Flue Gas loss; the sensible and latent heat lost up the chimney in the flue gas.

Front 37

Static head

Back 37

The pressure exerted by a vertical column of liquid.

Front 38

Temperature Differential

Back 38

The difference in temperature between 2 opposing masses; used to describe the potential that exists for heat transfer.

Front 39

Vapour Pressure

Back 39

The pressure exerted by a vapour. If a vapour is kept in confinement over its liquid so that the vapour can accumulate above the liquid, the temperature being held constant, the vapour pressure approaches a fixed limit, which is called saturated vapour pressure

Front 40

Velocity

Back 40

The speed of fluid at a specific flow, expressed in feet per second FPS

Front 41

Velocity of flow

Back 41

The rate of movement of a liquid or gas passing a given point in a unit time, such as feet per second.

Front 42

wiredrawing

Back 42

The knifelike cuts or cutting away effect on a valve, disc, plug or seat.

Front 43

Zone

Back 43

An area or portion of a heating system served by one or more loops and individually controlled (manually or automatically).