DEHYDRATOR  — Device used to remove moisture JOINING — All the procedures used to connect pipes from  a  refrigerant  system. together. DEW   POINT — Temperature at which vapor (at 100 percent humidity) begins to condense and deposit as a  liquid. DIATOMACEOUS  EARTH  —  A  porous  mineral powder, used as a filtering medium for the removal of suspended  materials. ELBOW  —  A  plumbing  fitting  used  to  change  the direction of a length of pipe at 90° and 45° angles. EVAPORATOR  —  Component  of  a  refrigeration system that permits the absorption of heat from a desired medium or space. EVAPORATION — A process of converting a liquid, by heat, into a vapor or gas. FILTER-DRIER — Device for removing small foreign particles and moisture from refrigerant fluid. FITTINGS  — Devices which when placed in a pipe system make branch connections or changes in a direction of a line. GATE  VALVE  —  A  sluice  with  two  inclined  seats between which the valve wedges down in closing. The passage through the valve is in an uninterrupted line,  and  when  the  valve  is  opened,  the  sluice  is drawn  up  into  a  dome  or  recess,  leaving  an unobstructed passage the full diameter of the pipe. GLOBE VALVE — A valve with a round, ball-like shell that is used for regulating or controlling the flow of gases or steam. GPD — Gallons per day. GPH — Gallons per hour. GPM — Gallons per minute. HEAT — The energy that is measured in British thermal units. HERMETICALLY SEALED — Caused to be airtight. HUMIDITY  — The amount of water vapor in a given volume of air. HYDROLOGIC CYCLE — Process by which water is circulated  from  ocean  to  atmosphere  to  earth’s surface. ID —  Inside  diameter. INFLUENT  —  Water  flow  into  a  sewage  or  water treatment  plant  or  equipment. LATENT HEAT — Amount of heat required to change the state of a substance without a measurable change in temperature. MATERIAL  TAKEOFF  —  The  estimate  of  materials required for a job based on plans and specifications. METERING  DEVICE  —  Valve  or  device  used  to regulate amount and state of refrigerant as it passes through the system. NAVFAC  —  Naval  Facilities  Engineering  Command. NCR — Naval Construction Regiment. NCTC — Naval Construction Training Center. NMCB — Naval  Mobile  Construction  Battalion. OD — Outside diameter. PACKING — Materials used to seal moving machinery joints  against  leakage. P H — A value used to measure the acidity or alkalinity (basic) of a substance. A pH scale is from 0 to 14, with 7.0 as neutral. Below 7.0 on the scale is acid, and above 7.0 on the scale is alkaline or basic. Used in water  treatment  and  purification. PLUG — A plumbing fitting used to close off a fitting or a length of pipe by screwing into the fitting or pipe. PPM — Parts per million. PSI — Pounds per square inch. PSIG — Pounds per square inch gauge. PUMP — A mechanical device which applies a force to move any substance that flows or can be made to flow. RADIATION  — The transfer of heat through space by heat waves. RECEIVER — Device in a refrigeration system to store refrigerant used by the system. REDUCING   VALVE  —  A  spring-loaded  or lever-loaded  valve  similar  to  a  safety  valve,  designed to  maintain  a  lower  end  constant  pressure  beyond  the valve. RELATIVE HUMIDITY — The percentage of water vapor in the air when compared to the amount it does hold as to the amount it could hold. AI-2