Valve Terminology

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z *

AGA: "American Gas Association." This organization has been replaced by CSA who purchased rights to the AGA name and standards.

Ammonia: Commonly found as a gas, terms like liquid ammonia and anhydrous ammonia are also in common use. In systems where ammonia is as a refrigerant (R717), brass or bronze valves should not be used. Carbon Steel valves are more commonly used in ammonia refrigeration systems.

ANSI: "American National Standards Institute" publishes the rules for design of piping system components.

API: "American Petroleum Institute" sets standards for products used in the Petroleum and Refining Industry, as well as serving as the information and public relations arm of the industry.

ASME: American Society of Mechanical Engineers

ASSE: American Society of Sanitary Engineering

ASTM: "American Society for Testing and Materials" is concerned with specifying materials and test procedures for the materials that are used in valves.

Atmospheric Vacuum Breaker (AVB): A backflow prevention device used in plumbing to prevent backflow of non-potable liquids into the potable (drinking water) system. It is usually constructed of brass and resembles a 90 degree elbow with a hood on its top to allow air to enter the water system if a siphon attempts to form. Inside this elbow is a poppet valve that is held "up" by the water pressure found in the system, closing the air entrance to the device. If the pressure in the "upstream side" is reduced to atmospheric pressure or below, the poppet valve drops and allows air to enter the system, breaking the siphon.Wikipedia, the free encyclopedia

Auto-Drain: More appropriately, this option (-41) should be called "Automatic-Venting". For Conbraco's Apollo Ball Valve, this option is limited to availability on bronze valves only. The valve is intended to vent the down stream pressure on a closed valve equipped with this option. It should be used only on either water or compressed non-hazardous gases, such as air or nitrogen. Valves with this option have limited service temperature and pressure ranges of +50F to +250F and 0 psig to 125 psig. These valves are subject to damage from dirt and debris in the piping system making them prone to leaks.

Backflow Prevention Device: A device, a valve, used to protect water supplies from contamination. Many types of backflow devices also have ports so that they can be tested or examined to ensure that they are functioning properly. A check valve is a common form of backflow preventer. Backflow prevention protects the potable water system from minor, moderate, and severe hazards. There are over 10,000 reported cases of backflow contamination each year. Some cases can be fatal. Backflow devices are required by law where needed and must be installed in accordance with plumbing code. A backflow assembly has test cocks and shut-off valves and must be tested each year, if relocated or repaired, and when installed.Wikipedia, the free encyclopedia

Ball Valve: A valve that opens by turning a handle attached to a ball inside the valve. The ball has a hole, or port, through the middle so that when the port is in line with both ends of the valve, flow will occur. When the valve is closed, the hole is perpendicular to the ends of the valve, and flow is blocked. The handle position lets you "see" the valve's position.Wikipedia, the free encyclopedia

Ball Valve: The Ball Valve is similar in concept to the plug valve but uses a rotating ball with a hole through it that allows straight-through flow in the open position and shuts off flow when the ball is rotated 90 degrees to block the flow passage. It is used for on-off and some throttling services.

Black Liquor: Highly alkaline black to dark brown liquid. Thick like molasses. Contains the dreggs of the pulp making process including lime, dirt, gravel, etc. Typically very high solids content and very hot.

Bleach: See sodium hypochlorite. Household bleach has a typical concentration of less than 20%.

Boiler and Pressure Vessel Code: A series of standards produced and distributed by the American Society of Mechanical Engineers (ASME) which defines requirements associated with pressure containing systems.

Boiler Code: See Boiler and Pressure Vessel Code

Bonnet: A bonnet basically acts as a cover on the valve body. It is commonly semi-permanently screwed into the valve body. During manufacture of the valve, the internal parts were put into the body and then the bonnet was attached to hold everything together inside. To access internal parts of a valve, a user would take off the bonnet, usually for maintenance. Many valves do not have bonnets; for example, plug valves usually do not have bonnets.Wikipedia, the free encyclopedia

Butterfly Valve: The Butterfly Valve controls flow by using a circular disc or vane with its pivot axis at right angles to the direction of flow in the pipe. A Butterfly Valve requires a minimum of space and can be used both for on-off and throttling services.

Butterfly Valve: A flow control device, typically used to regulate a fluid flowing through a section of pipe. A flat circular plate is positioned in the center of the pipe. The plate has a rod through it connected to a handle on the outside of the valve. Rotating the handle turns the plate either parallel or perpendicular to the flow. The plate is always present within the flow; therefore a pressure drop is always induced in the flow regardless of valve position.Wikipedia, the free encyclopedia

Caustic: Caustic is an entire family of chemicals characterized by the hydroxyl radical. The family includes such common products as Calcium Hydroxide, Potassium Hydroxide (Potash) and Sodium Hydroxide (Caustic Soda). Glass reinforced PTFE should not be used in these services.

CE Mark: This program is linked to the European Pressure Equipment Directive. Through a series of prescribed steps valves are identified, by means of applying the CE logo, as appropriate for import and use in the member countries of the European Union. It is applicable to valves larger than 1". At the time of this writing, only the 87A/88A Series and the Top Entry Valve series are approved to bare the CE mark and only then when produced in carbon or stainless steel.

CGA: Canadian Gas Association. This organization has been replaced by CSA who purchased rights to the CGA name and standards.

Check Valve: A mechanical device, a valve, that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have two openings in the body, one for fluid to enter and the other for fluid to leave. There are various types of check valves used in a wide variety of applications. Check valves are often part of common household items. Although they are available in a wide range of sizes and costs, many check valves are very small, simple, and/or cheap. Check valves work automatically and most are not controlled by a person or any external control; accordingly, most do not have any valve handle or stem. The bodies (external shells) of most check valves are made of plastic or metal.Wikipedia, the free encyclopedia

Class IV Leakage: Class IV leakage rates are based on tests conducted with water or air at pressures up to 60 psig. Hard seated ball valves, such as those with Metal to Metal, PEEK or Graphite are commonly promoted as having at least a Class IV rating. Allowable leakage is expressed as 0.01% of the valves rated flow capacity. For ball valves, we assume this "capacity" to be equal to the valve's Cv. For a 1" full port valve that allowable leakage rate would be 0.68 gallons per minute or 2574 ml per minute.

Class V Leakage: Class V leakage rates are based on tests conducted with water at any agreed pressure up to the valve's maximum rating. Hard seated ball valves, such as those with Metal to Metal, PEEK or Graphite seats may achieve a Class V rating with special preparation, but most commonly are promoted as having a Class IV rating. Assuming a 1" full port valve closed against 100 psig of water pressure, the allowable leakage rate under this classification would be 0.05 ml/minute.

Class VI Leakage: Class VI leakage rates are based on tests conducted with air or nitrogen at no more than 50 psig. Any new "soft seated" ball valve should achieve a Class VI rating. Assuming a 1" full port valve closed against 50 psig of air pressure, the allowable leakage rate under this classification would be 0.15 ml/minute.

CMTR: "Certified Material Test Report" documents the compliance of a material to specific published standards by the original material producer. All MTR's issued by Conbraco for our castings are in fact CMTR's. An MTR for bar stock or forged material issued on the original manufacturer's letterhead is a CMTR's. Should those results be reproduced and distributed on Conbraco letterhead they would be referred to as MTR's.

Control Valves: Valves used within industrial plants and elsewhere to control operating conditions such as temperature, pressure, flow, and liquid level by fully or partially opening or closing in response to signals received from controllers that compare a "set point" to a "process variable" whose value is provided by sensors that monitor changes in such conditions. The opening or closing of control valves is done by means of electric, hydraulic or pneumatic systems.Wikipedia, the free encyclopedia

CSA: Canadian Standards Association. Replaced the former AGA and CGA organizations.

Diaphragm Valve: The Diaphragm Valve effects closure by means of a flexible diaphragm attached to a compressor. When the compressor is lowered by the valve stem onto a weir, the diaphragm seals and cuts off flow. The diaphragm valve handles corrosive, erosive and dirty services. It is an easily maintained valve.

Dielectric Union: Dielectric unions are required in some applications by code. In particular on water heaters, in the transition from black pipe to copper. The basis for their use is to prevent galvanic corrosion of the black iron pipe. Whether or not they are technically necessary depends largely on water chemistry. In applications with dissolved electrolytes their use would be beneficial.

Double Check Valve or Double Check Valve Assembly (DCVA): A backflow prevention device designed to protect water supplies from contamination. It consists of two check valves assembled in series usually with a ball or gate valve installed at each end for isolation and testing. Often, test cocks (very small ball valves) are in place to attach test equipment for evaluating whether the double check assembly is still functional. The double check valve assembly is suitable for prevention of back pressure and back siphonage, but is not suitable for high hazard applications. It is commonly used on lawn irrigation and fire sprinkler systems.Wikipedia, the free encyclopedia

Electronic Data Interchange (EDI): A set of standards for structuring information to be electronically exchanged between and within businesses, organizations, government entities and other groups. The standards describe structures that emulate documents, for example purchase orders to automate purchasing. The term EDI is also used to refer to the implementation and operation of systems and processes for creating, transmitting, and receiving EDI documents.Wikipedia, the free encyclopedia

Fire Safe: See fire tested. By itself the term has no agreed meaning. Should be accompanied by reference to a specific standard.

Fire Tested: The term should be used with reference to a specific standard. Several series of Apollo ball valves are available as fire tested to API 607, 4th edition. This is always an optional feature.

Floating Ball: Conbraco manufactures only "floating ball" ball valves. The term "floating ball" comes from the feature that the ball is suspended in the assembly by the valve seats. There are no other supporting structures, like trunnions. The ball literally "floats" between the valve seats. Floating ball valves are intended to seal on the down stream seat.

Freon & reg;: The word Freon® is a registered trade mark of DuPont. A family of refrigerants characterized by their fluorine content. Commonly referred to as R12, R22, R134a, etc. There are now "Freons" that are blends of the basic gases.

Fuel Gas: Any one of many hydrocarbon based gases used for fuel. These include refined or purified grades like methane, propane and butane, but may be mixtures like LP or Natural Gas.

Gate Valve: The Gate Valve is a general service valve used primarily for on-off, non-throttling service. The valve is closed by a flat face, vertical disc or gate that slides down through the valve to block the flow.

Globe Valve: The Globe Valve effects closure by a plug with a flat or convex bottom lowered onto a matching horizontal seat located in the center of the valve. Raising the plug opens the valve to let flow through. The Globe Valve is used for on-off service and handles clean service throttling applications.

Green Liquor: An alkaline liquid, greenish in color containing a significant amount of solids, particularly lime or calcium carbonate and is generally hot.

Grounding: Grounding implies a requirement for electrical continuity between the various components of a valve. Conbraco offers two types of grounding; option codes -02 and -60. (See Options explained under tab labeled "M, N, O, P".)

Guide MHKZ: See "MHKZ".

Guide YRBX: See "YRBX".

Guide YRPV: See "YRPV".

Guide YSDT: See "YSDT".

Hard Seat: Applicable to more than just ball valve seats, this general term is used to describe devices with rigid sealing elements, such as "metal to metal", PEEK, Carbon Graphite or Ceramic.

Hydronics: The name for the use of water as the heat-transfer medium in heating and cooling systems.Wikipedia, the free encyclopedia

Hypo: Slang term for sodium hypochlorite.

Leakage Classification: There are 6 leakage classes defined in ANSI/FCI 70-2, "Control Valve Seat Leakage". Although this standard was written for control valves, it is commonly miss-applied to ball valves. Control valves, as defined by this standard, have actuators that can adjust the loads on the valve seats to effect shut-off. Ball valves are on-off devices not intended for control or throttling applications and seat tightness cannot be effected by the actuation device. Because each classification is based on a different test method direct comparison is difficult, but suffice it to say the Class VI is the most stringent of the requirements. See each rating, Class IV, Class V or Class VI for more details.

Lime: Also known as Calcium Carbonate. A white powder which may be in lump form. Commonly used in the processing of pulp in the paper making process.

Liquor: A family of terms commonly used in the Pulp and Paper industry. Includes Black Liquor, Green Liquor and White liquor. See each term individually for further explanation.

LP Gas: LP Gas is a fuel gas formed by the mixture of liquefied petroleum gases, commonly propane and butane. LP gas is produced and frequently stored at reduced temperatures. Depending where a valve is installed in an LP gas system option -14 "Vented Ball" may be required. This is particularly important on valves which can undergo significant temperature changes. Some LP gas applications will require UL or CSA listed valves of which Conbraco offers several.

MHKZ: Guide (Category Code) MHKZ. The basic standard used to investigate products in this category is UL842, "Valves for Flammable Fluids". Manually operated valves are intended specifically for use with gas- or oil burning equipment. Metering Valves are primarily for use in the burner fuel supply line to manually regulate the flow of fuel to the burner. Shut-Off Valves are for use in the burner supply line to manually shut off the flow of fuel to the burner.

MSDS Sheet: "Material Safety Data Sheet" is a document used to communicate hazards associated with a substance. Conbraco's products meet the requirements under the definition of an "Article" and are considered exempt from the Hazard Communication Standard 29 CFR 1910.1200. OSHA defines an "Article" as a manufactured item: (1) which is formed to a specific shape or design during manufacture (2) which has end use function(s) dependent in whole or in part upon its shape or design during end use; and (3) which does not release, or otherwise result in exposure to, a hazardous chemical under normal conditions of use.

MSS: "Manufacturers Standardization Society of the Valve and Fitting Industry" is an organization of manufacturers that publish specifications where no other specification exists.

MTR: "Material Test Report" documents the compliance of a material to specific published standards. All MTR's issued by Conbraco for our castings are in fact CMTR's. MTR's issued for bar stock or forged material on the original manufacturer's letterhead are CMTR's. Should those results be reproduced and distributed on Conbraco letterhead they would be referred to as MTR's. (See also CMTR.)

NACE: "National Association of Corrosion Engineers" writes standards and recommended practices in regard to the use of materials and the condition of those materials for Oil Field and other applications.

Natural Gas: Natural Gas is a fuel gas formed from refined naturally occurring hydrocarbon gases, primarily Methane. Depending where a valve is installed in a gas system option -14 "Vented Ball" may be required. This is particularly important on valves which can undergo significant temperature changes. Some Natural Gas applications will require UL or CSA listed valves of which Conbraco offers several.

Needle Valve: The Needle Valve is a volume control valve that restricts flow in small lines. The fluid going through the valve turns 90 degrees and passes through an orifice that is the seat for a rod with a cone-shaped tip. The size of the orifice is changed by positioning the cone in relation to the seat.

NXT: This is Dupont's trade name for their "Super-PTFE". Conbraco offers a similar material in our -80 option.

Option -01: Standard trim. For Apollo ball valves this includes reinforced PTFE seats and seals and a lever handle.

Option -02: Grounded (Stem Only). When "factory standard" grounding is specified, this is the option selected. This option is effective when there is a concern regarding static electricity discard when contact is made with the valve handle. This is generally imposed with the general environmental conditions may contain explosive or flammable vapors or gases, such as might be found in a chemical refinery.

Option -03: 1-1/4" stem extension. This option elevates the handle approximately 1-1/4" above its original position to typically allow clearance for insulating the pipe and valve.

Option -04: 2-1/4" stem extension. This option elevates the handle approximately 2-1/4" above its original position to typically allow clearance for insulating the pipe and valve.

Option -20: Slot venting is standard on carbon and stainless steel balls and optional on brass or bronze balls. It particularly critical to employ slot vented balls in steam applications. In a steam application, water condenses in the body cavity of a closed valve. Once open, and steam is flowing, the temperature of the valve raises quickly causing the water trapped in the area between the ball and the body to flash to steam. Without slot venting the sudden rise in pressure due to the rapid rise in temperature may cause extrusion-like damage to the seats or seals of the valve leading to premature failure.

Option -41: More appropriately this option should be called "Automatic-Venting" in lieu of "Auto-Drain". For Conbraco's Apollo Ball Valve, this option is limited to availability on bronze valves only. The valve is intended to vent the down stream pressure on a closed valve equipped with this option. It should be used only on either water or non-hazardous gases, such as air or nitrogen. Valves with this option have limited service temperature and pressure ranges of +50F to +250F and 0 psig to 125 psig respectively.

Option -60: Grounded (Ball and Stem). This option assures electrical continuity between all components of a valve. The most common application is in gaseous services. Dry gases flowing through a device at high velocities can generate significant static charges. A ball valve ball suspended between PTFE or other polymeric seats is normally isolated from ground. This option assures that the ball and stem both have continuous contact with the valve body. Without this feature the static charge generated on the ball may arc to ground causing an internal explosion.

Option -80: Trade named Multi-Seal, this is Conbraco's offering for what has been referred to as "Super-PTFE". Only available in the flanged valve series at the time of this writing, this material is based on Dyneon's TFM-1600 resin. This material PTFE based containing a PFA modifier for improved properties including increased strength and increased resistance to "pop corning".

Original Equipment Manufacturer (OEM): A term that refers to a situation in which one company purchases a manufactured product from another company and resells the product as its own, usually as a part of a larger product it sells. OEM is the company that originally manufactured the product. The term OEM was coined in the 1950s by IBM. It designated a customer that purchased IBM computers and resold them as part of a larger product. The first OEMs sold oil refineries.Wikipedia, the free encyclopedia

PED: See Pressure Equipment Directive.

Peroxide: Valves intended for Peroxide service must be properly cleaned and vented. Option code -57 is appropriate for most Apollo Ball Valve. For the Top Entry Ball Valve this is option -HH. Carbon steel valves are not generally acceptable in this application. Avoid Multi-fill seats and seals, including packing. Specify -35 trim if at all possible.

PFA: Perfluoroalkoxy. This seat and seal material offers many of the same properties as PTFE, but has the added advantage of being resistant to a phenomena known as "pop corning". PFA is suggested for services containing Styrene, Butadiene and Latex which all have this effect on ordinary PTFE based materials.

Pinch Valve: The Pinch Valve finds wide application on slurries or liquids with large amounts of suspended solids. It seals by means of one or more flexible elements, such as a rubber tube, that can be pinched to shut off flow.

Plug Valve: The Plug Valve is used primarily for on-off service and some throttling services. It controls flow by means of a cylindrical or tapered plug with a hole in the center that lines up with the flow path of the valve to permit flow. A quarter turn in either direction blocks the flow path. Used on wine casks.

Poppet Valve: A valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide. In most applications a pressure differential helps to seal the valve and in some applications also open it.Wikipedia, the free encyclopedia

Pressure Equipment Directive: A legal document defining common requirements for valves and other devices intended for use within member states of the European Union.

Pressure Vessel Code: See Boiler and Pressure Vessel Code.

PTA: Purified Terrathalic Acid. Generally found in a powdered form. Used as a filler and reinforcing material in plastics and other materials.

PTFE: Polytetrafluorethylene. Also know as Teflon® a registered trademark of DuPont. The is the polymer used to produce option -35 seats and seals. It is the base polymer for the other reinforced grades offered by Conbraco as options -01(glass reinforced PTFE) and -56/64/65 (multi-fill PTFE).

Reduced Pressure (RP) backflow prevention device: A device used to protect the potable water supply from contaminated water. An RP valve consists of an automatic pressure relief valve in between two check valves. The pressure relief valve opens to the atmosphere in the event of a reduction in the pressure between the two check valves. The assembly is considered to provide redundant means of protection, through the use of the check valves, which keep water flowing only in one direction, and the relief valve in the event that one or both check valves fail. Reduced pressure backflow preventers can be abbreviated RP RPP and RPZ. RP assemblies protect against back-siphonage and backpressure, and may be used where a potential hazard exists. RP valves can be found in commercial buildings, hospitals, and industrial applications.Wikipedia, the free encyclopedia

Refrigerant: A group of hydrocarbon gases with particularly advantageous thermodynamic properties. Among these are Freon (an entire family of materials in itself) and ammonia. In systems where ammonia is the refrigerant, brass or bronze valves should be used with caution. Carbon Steel valves are more commonly used in ammonia refrigeration systems.

Safety Relief Valve (SRV): A valve mechanism for the automatic release of a gas from a boiler, pressure vessel, or other system when the pressure or temperature exceeds preset limits. They are often called by more specific names such as pressure relief valve, T&P valves, or temperature and pressure relief valves.Wikipedia, the free encyclopedia

Self-Relieving Seats: Defined by API 6D as seats that automatically reduce the pressure in a closed valve's body cavity to atmospheric pressures if the trapped pressure exceeds 133% of the valves nominal rating. Trunnion mounted ball valves are capable of relieving trapped body cavity pressure to a safe predetermined level, but not necessarily atmospheric pressure. The concept of self-relieving seats in soft seated floating ball valves is largely a myth and none of the competitive valves tested have come close to meeting API 6D's definition. Apollo's ball valve seats are not promoted as "self-relieving".

Sodium Hypochlorite: In a dilute form, this is the technical name for household bleach.

Soft Seat: Applicable to more than just ball valve seats, this general term is used to describe devices with either elastomeric (rubber) or resilient polymer (flexible plastic) sealing elements. For Apollo, soft seats are made from either PTFE, RPTFE, TFM, UHMWPE, Nylon or Acetal (Delrin).

Solvent: A volatile hydrocarbon. Generally flammable to explosive. Frequently requires consideration of "fire tested" valves. Usually requires vented valves.

Teflon®: A registered trademark of DuPont. The word can only be used when specifically licensed to do so by DuPont and only in strict reference to materials produced by DuPont. Not to be used as a generic name for PTFE or materials containing PTFE.

Thermostatic Mixing Valve (TMV): A valve that blends hot water (stored at temperatures high enough to kill bacteria) with cold water to ensure constant, safe outlet temperatures preventing scalding. The storage of water at high temperature removes one possible breeding ground for Legionella; the use of a thermostat rather than a static mixing valve provides increased safety against scalding, and increased user comfort because the hot-water temperature remains constant. Many TMVs use a wax thermostat for regulation. They also shut-off rapidly in the event of a hot or cold supply failure to prevent scalding or thermal shock. It is increasingly common practice around the world to regulate the storage water temperature to above 60C, and to circulate or distribute water at a temperature less than 50C. Water above these temperatures can cause life threatening scald injuries. Many countries, states, or municipalities now require that the temperature of all bath water in new build and extensively refurbished domestic properties be controlled to a maximum of 48C. Installing Thermostatic Mixing Valves (TMVs) can ensure that water is delivered at the required temperature thereby reducing the risk of scalding accidents; it also makes the hot water supply last longer than one that is maintained at a lower temperature.Wikipedia, the free encyclopedia

Three-way valves: A valve with three ports / openings. 3-way valves are commonly made such that flow coming in at one port can be directed to either the second port in one position or the third port in another position or in an intermediate position so all flow is stopped. Often such 3-way valves are ball or rotor valves. Many faucets are made so that incoming cold and hot water can be regulated in varying degrees to give out coming water at a desired temperature.Wikipedia, the free encyclopedia

Tickle: Slang term for Titanium Tetrachloride, chemical symbol TiCl3.

Trim: The definition varies by manufacturer. Some manufacturers refer to "trim" as the stem and ball or closure member. Some use the term in reference to soft goods, such as seats, seals and gaskets. MSS defines trim as the "functional parts of a valve that are exposed to the line fluid", which would encompass both of the above interpretations

Trunnion Mounted: As opposed to a "Float Ball", the ball on a "trunnion" or "trunnion mounted" valve is supported by bearings within the valve body and the valve seats are typically loaded against the ball. Trunnion mounted valves have a few unique capabilities; the valve seals on the upstream seat, the seats tend to be somewhat self-relieving and the valve is generally capable of double block and bleed, two characteristics not normally found in floating ball valves.

Two-way valves: A valve with two ports / openings. Operating positions for such valves can be either shut (closed) so that no flow at all goes through, fully open for maximum flow or sometimes partially open to any degree in between. Many valves are not designed to precisely control intermediate degree of flow; such valves are considered to be either open or shut, with maybe qualitative descriptions in between. Some valves are specially designed to regulate varying amounts of flow. Such valves have been called by various names like regulating, throttling, metering, or needle valves. For example, needle valves have elongated conically-tapered discs and matching seats for fine flow control. For some valves, there may be a mechanism to indicate how much the valve is open, but in many cases other indications of flow rate are used, such as separate flow meters.Wikipedia, the free encyclopedia

UL: Underwriters Laboratories

UL Guide: These are more properly called category codes. See also "YSDT", "YRPV", "YRBX", and "MHKZ".

Union, Dielectric: Dielectric unions are required in some application by code. In particular on water heaters, in the transition from black pipe to copper. The basis for their use is to prevent galvanic corrosion of the black iron pipe. Whether or not they are technically necessary depends largely on water chemistry. In applications with dissolved electrolytes their use would be beneficial.

Valve: A device that regulates the flow of substances (gases, fluidized solids, slurries, or liquids) by opening, closing, or partially obstructing various passageways. Valves are technically pipe fittings, but usually are discussed separately.Wikipedia, the free encyclopedia

Valve Seat: A valve seat is the interior surface in the body which contacts or could contact the disc to form a seal which should be leak-tight, particularly when the valve is shut (closed). If the disc moves linearly as the valve is controlled, the disc comes into contact with the seat when the valve is shut. When the valve has a rotor, the seat is always in contact with the rotor, but the surface area of contact on the rotor changes as the rotor is turned. If the disc swings on a hinge, as in a swing check valve, it contacts the seat to shut the valve and stop flow. In all the above cases, the seat remains stationary while the disc or rotor moves. The body and the seat could both come in one piece of solid material, or the seat could be a separate piece attached or fixed to the inside of the valve body, depending on the valve design.Wikipedia, the free encyclopedia

Valve Stem: A stem is a rod or similar piece spanning the inside and the outside of the valve, transmitting motion to control the internal disc or rotor from outside the valve. Inside the valve, the rod is joined to or contacts the disc/rotor. Outside the valve the stem is attached to a handle or another controlling device. Between inside and outside, the stem typically goes through a valve bonnet if there is one. In some cases, the stem and the disc can be combined in one piece, or the stem and the handle are combined in one piece.Wikipedia, the free encyclopedia

Venting: Venting is done to prevent the build-up of pressure in the body cavity of a valve. All carbon steel and stainless steel balls are slot vented as standard. Option -20, "Slot Vented ball may be ordered on any brass or bronze valves and option -14, "Side Vented Ball", is available on either brass or stainless balls. (See Options explained under tab labeled "M, N, O, P".)

Wetted Parts: Any component of a device subject to contact with the fluids it contains. For ball valves, the metallic wetted parts are generally assumed to be the body, retainer or bonnet, ball and stem. Seats and seals are also wetted parts.

White Liquor: A golden or light brown liquid. Highly alkaline. Can contain significant solids particularly lime or calcium carbonate.

YRBX: Guide (Category Code) YRBX. The basic standard used to investigate products in this category is UL842, "Valves for Flammable Fluids". These are ball valves designed for use in pipe lines or equipment assemblies for gasoline, kerosene, fuel oil, petroleum dry cleaning solvent, etc. Valves may be of the manual or Self-Closing remote control.

YRPV: Guide (Category Code) YRPV. The basic standard used to investigate products in this category is UL842, "Valves for Flammable Fluids". These are manual gas shut-off valves intended for use in lines conveying fuel gases.

YSDT: Guide (Category Code) YSDT. The basic standard used to investigate gas line service valves is UL125, "Valves for Anhydrous Ammonia and LP-Gas (Other Than Safety Relief)". LP-Gas shut-off valves include Department of Transportation (DOT) shipping container (cylinder) valves, gas line service valves, emergency shut-off valves. These valves are intended to be installed and used in accordance with the Standard of the National Fire Protection Association for the Storage and Handling of Liquefied Petroleum Gases, NFPA 58. They are suitable for use with LP-Gas in either the liquid or gaseous phase at working pressures of at least 250 psi. Those suitable for use at pressures in excess of 250 psi are marked with the maximum pressure. These valves are, suitable for installation where a positive shut-off is required.

Zero Leakage: This term has no verifiable meaning on its own. Most test standards for soft seated valves allow no leakage for the period of the test, commonly called zero leakage. But, the period of these tests is usually measured in seconds, or even occasionally minutes. Zero leakage on its own would imply that a device would never leak.