Valves are essential components in piping systems, used to control, direct, and regulate the flow of fluids. To work safely and effectively in the piping trades, it is important to understand the basic terminology used to describe valves, their parts, and how they operate. The following section introduces key valve terms and concepts that you will encounter on the job and in technical documentation.

Valve Terminology

It is important to be able to define basic valve terminology. You should be familiar with the following terms:

air valve: A valve used to control the flow of air.

backpressure: The pressure exerted on the downstream side of a valve seat.

ball valve: A quarter-turn valve with a ball-shaped closing element held between two seats.

backwater valve: A check valve designed for use in a sanitary drainage system.

bellows: A sealing device that prevents line media from leaking between the stem and the body.

bidirectional valve: A valve that moves or operates in two opposite directions.

butterfly valve: A quarter-turn valve that has a circular disk as its closing element.

bypass valve: A small-bore valve fitted in parallel with a larger main valve.

cavitation: The noise and damage caused when high-velocity turbulent flow and low pressure occur in a valve forming gas bubbles that collapse rapidly; the gas bubble rapidly turns back into water when the velocity drops and the pressure increases. This results in deterioration of internal valve parts and premature failure.

check valve: A valve designed to allow fluid to flow in one direction only and prevent reverse flow. The valve closes to prevent backflow.

control valve: A valve that regulates the flow or pressure of a fluid. Control valves respond to signals generated by independent devices such as flow meters, temperature gauges, etc. Control valves are typically fitted with actuators and positioners.

cryogenic valve: A valve designed for use at temperatures below –40°C (–40°F).

diaphragm valve: A bidirectional valve operated by applying an external force to a flexible element, or diaphragm (typically an elastomer).

diverter valve: A valve that changes the direction of the flow of medium to two or more outlets/ directions.

double block and bleed: A valve configuration in which positive shut-off is achieved at both the inlet and outlet sides, with a pressure bleed between them.

elastomer: Any material, such as natural or synthetic rubber, that is able to resume its original shape when a deforming force is removed.

galling: A severe form of metal wear caused when sliding surfaces make contact, tearing areas of the metal surface.

lantern ring: A metal ring in a valve that provides for uniform distribution of stem packing pressure over the packing.

positioner: A device used to ensure that the valve is at the correct position of opening as the control signal indicates.

quarter-turn valve: A valve in which the handle and stem move from fully closed to fully open in one-quarter of a 360° turn (90°).

resilient seat: A valve disk or seat that is soft-seated rather than a metal-to-metal hard seat. An example is a Teflon seat.

stuffing box: An enclosure containing packing to prevent leakage around a moving machine part, such as a valve stem.

trunnion: A valve component such a pin or pivot on which something can be rotated, such in a trunnion ball valve, which has additional mechanical anchoring of the ball at the top and the bottom, suitable for larger and higher pressure valves.

valve actuator: A device used to open, close, or control a valve, such as manual handles and electrical, hydraulic, and pneumatic actuators.

valve chatter: The noise created when the water flow causes loose valve components to rattle or chatter in rapid succession.

valve packing: A sealing material, usually graphite, used to seal around a valve stem to prevent leakage of system fluids.

valve stem: The part of a valve that connects the handle or actuator to the internal closing part (such as a disk or gate) and moves to open or close the valve.

wire drawing: The visual effect of erosion of a valve seat or disk. Wire drawing occurs when a valve is not closed perfectly tight.

Valve Materials

The materials used to construct a valve play an important role in its ability to operate in the working environment to which it will be subjected. It may be unsafe to use materials for services beyond their recommended maximum limits.

Valve materials are selected by the following considerations:

• Pressure limitations
• Temperature limitations
• Structural limitations

Valve materials commonly used in industry include the following:

• Bronze
• Iron
• Malleable iron
• Ductile iron
• Steel
• Stainless steel
• Titanium
• Plastics
• Composites

Valve Purpose

The main purpose of a valve is often to turn on (start) or shut off (stop) the flow in a piping system. However, valves can serve many purposes, such as:

• Limiting pressure
• Regulating pressure
• Controlling flow rate
• Turning flow off and on
• Mixing  water of different temperatures
• Limiting maximum temperature
• Preventing reverse direction flow
• Balancing flow across different circuits

Valve Classification

Valves can be classified into two general categories based on the motion of the valve stem/operator:

• Linear movement valves: The stem moves in a straight line. These include gate valves, globe valves, diaphragm valves and pinch valves.
• Rotary movement valves: The stem rotates around an axis at right angles to the direction of flow. These include ball valves and butterfly valves.

Table 1: Identifying the Valve Type by the Motion of the Actuator

Valve Movement	Linear Motion		Rotary Motion
Operating motion of the closing device	In a straight line		Rotating about an axis at right angles to the direction of flow
Direction of flow in the seating area	At right angles to the operating motion	Longitudinal to the operating motion	Through the disk	Around the disk
Basic types	Gate valve	Globe valve	Ball valve	Butterfly valve
Schematic

Valve Selection

When selecting a valve for a specific job, you will need to match the valve specifications to the job specifications. This is important to ensure dependable, long-term performance.

Before selecting a valve, consider the following factors:

• Operation cycle (number of times the valve will have to open and close)
• Specific purpose of the valve (to stop, regulate, divert, or relieve pressure)
• Pressure loss through the valve (pressure loss must be within system requirements)
• Expected flow volume of the system (must allow sufficient flow for system)
• Working and maximum pressures of the system (the valve characteristics should not be lower than those of the system)
• Working and maximum temperatures of the system (the valve characteristics should be the same or higher)
• Characteristics of the fluid being handled (for example, viscosity, volatility, corrosiveness)
• Presence of debris in the fluid (the valve’s capability to handle solids)
• Maintenance schedule (need for frequent maintenance may be a concern)
• Installation costs, maintenance costs and initial cost
• Exposure to the surrounding environmental conditions (for example, heat, freezing, physical damage and corrosive atmospheric conditions)
• Clearances for operation and maintenance
• Other specific job-related specifications and conditions, including any code requirements

Valve Specifications

Valves should be clearly marked with the manufacturer’s name and the size of the valve. Valves may also be marked with other information, such as the temperature and pressure ratings. Often letter codes are used to indicate the valve’s appropriate uses. Detailed service ratings are usually found in the manufacturer’s published specifications.

• G: gas service
• L: liquid service
• O: oil service
• S: steam service
• W: water service

The ability to read and interpret valve markings and specifications is key to installing the correct valve. Each manufacturer may have a different system of valve markings, which is explained in that manufacturer’s product literature. Following are examples of valve markings found on Crane valves.

 

Table 2: First Example of Letter Codes

2	pipe size in inches
Crane	manufacturer
125	basic steam working pressure
6	pipe size in inches
Crane	manufacturer
Steel	carbon cast steel valve
150	basic steam working pressure

 

Table 3: Second Example of Letter Codes

6	pipe size in inches
Crane	manufacturer
Forged Steel	carbon cast steel valve
150	basic steam working pressure
6	pipe size in inches
Forged Steel	carbon cast steel valve
150 WOG	working pressure water, oil or gas

Examples of Valve Specifications

On most jobs, you will install valves that have already been selected by the design engineer. On some jobs, however, you will need to select the correct valve yourself, using the manufacturer’s written specifications. You therefore must be able to read and interpret specifications such as those shown in the following tables. Note that these example tables are general in nature and are for the purpose of illustration. Always refer to the manufacturer’s specifications.

Table 4: Valve Test Pressure Specification

Test Pressures
Body	1.5 MPa (15 kg/cm2) (217.6 psi)	2.4 MPa (24 kg/cm2) (348 psi)
Seat & back seat	1.0 MPa (10 kg/cm2) (145 psi)	1.6 MPa (16 kg/cm2) (232 psi)

Table 5: Valve Materials

Part No.	Name of Part	Material
1.	Body	Bronze
2.	Wedge	Bronze
3.	Stem	High tensile brass
4.	Bonnet	Bronze
5.	Stuffing box	Bronze
6.	Gland packing	Asbestos/Teflon
7.	Gland	Bronze
8.	Gland nut	Bronze
9.	Handwheel	Cast iron
10.	Washer	Mild steel
11.	Screw	Mild steel

Table 6: Valve Dimensions

Nominal Size		Length (mm)	Height (mm)	Width (mm)	Flange Diameter (mm)	Flange Thickness (mm)
Inches	mm
0.5″	15	72	102	58	95	6
[latex]\frac{3}{4} \text{"}[/latex]	20	76	115	58	105	6
1″	25	90	129	67	115	8
1.25	32	100	140	73	140	8
1.5″	40	110	162	85	150	9
2″	50	120	188	110	165	11
2.5″	65	140	220	110	185	13
3″	80	150	249	133	200	13
4″	100	190	292	173	220	16

Valve Actuator

A valve actuator is a device used to open, close or control a valve.

The types of valve actuators include the following:

• Handwheel: used to open or close a valve by turning it by hand (manually). No power is required.
• Pneumatic (air-operated) diaphragm: uses compressed air to move the valve open or closed. Air pressure pushes on a flexible diaphragm.
• Electric motor: uses electricity to turn the valve open or closed. It is often used when the valve needs to be controlled from a distance (remote control).
• Electric solenoid: uses electricity to create a magnetic force that moves the valve (electromagnetic force). It is usually used for quick on-off control.
• Hydraulic (piston-operated): uses pressurized oil or fluid to push a piston that moves the valve. It is used when a lot of force is needed.

 

Pneumatically actuated globe valves are widely used for control purposes in many industries, although quarter-turn types such as (modified) ball and butterfly valves may also be used.

 

 

Bypass Valves

Bypass valves are usually identified as valves placed on a piping arrangement called a bypass.

 

A bypass valve can control the fluid flow when the main valve is shut down for maintenance. The bypass valve may be used around equipment or pressure-reducing valves. The bypass can act as a quick fill in some cases or to divert flow, such as in a water treatment system. The type of valve used in the bypass depends on whether it will be used to open, close or adjust the flow. A globe valve bypass valve would provide some flow control. A gate valve or ball valve bypass valve would serve to stop flow rather than regulate the flow.

 

Stop and Waste Valves and Drain Valves

Stop and waste valves are specialty valves that serve as on and off shutoffs. They have a drain cap on the upstream side of the shut-off. Stop and drain valves allow the system to be drained for winterizing or repairs. Both types of valve are available with several different connection types (Figure 59).

Diaphragm Valve

Diaphragm valves are used for corrosive and abrasive applications with 100% leak-tight operation. The valve stem and components are separated from the fluid by the diaphragm.

Diaphragm valves may be used for slurries (where other valve designs might clog) and in hygienic applications.

 

Pinch Valve

Pinch valves are suited for applications in which slurries or liquids contain large amounts of suspended solids. Pinch valves seal by pinching a flexible element such as a rubber tube.

Multiport Valves

Three-Port Mixing and Diverting Valves

Three-port valves can be used for either mixing or diverting service, depending upon the piping arrangement. Valves similar to these types of valves are used on hydronic heating systems and domestic hot water systems.

Mixing valves and diverting valves can be easily distinguished visually by inspecting the piping arrangement:

• The mixing valve has two inlets and one outlet.
• The diverting valve has one inlet and two outlets

 

There are three basic types of three-port valve:

• Piston valve type
• Globe, plug type
• Rotating shoe type

Hot Water Temperature Control Valves

Thermostatic mixing valves maintain and limit mixed hot water to a desired, selectable temperature. Hot water temperature control valves are used in commercial, residential, and institutional applications to reduce the temperature of the hot water supply, thereby minimizing the risk of thermal shock and scalding to those using the water.

 

Double Block and Bleed Valves

Double block and bleed valves have evolved to replace the process of bolting together individual valves to provide dual isolation. The block and bleed valve manifold is used to isolate or block the flow of fluid in the system. A block and bleed valve would be used to stop the flow of fluids to some component. Fluid would be vented from that component’s side of the manifold to allow maintenance.

 

This configuration is often required to isolate high-pressure sections of a system to facilitate safe maintenance, etc.

 

Post Indicator Valves

A post indicator valve is little more than a gate valve, usually installed underground, that has an indicating post attached to the valve riser above ground to show whether the valve is open or closed. The valve is often used for underground fire protection lines.

Pressure Relief Valves

The pressure relief valve (PRV) is a type of safety valve used to control or limit the pressure in a piping system or components. The PRV opens when the pressure in the system reaches the relief valve pressure set point. The pressure relief set point is usually set below the maximum design limits of the piping system components or pressure vessel. PRVs can be preset by the factory for a specific purpose or they can be adjustable. Adjustable PRVs should be set at least 25% higher than system pressure but below the maximum pressure limit of the system components.

Regulations require PRVs on specific piping systems and pressure vessels. PRVs are typically required on domestic and commercial hot water storage heaters, heat exchangers, hydronic heating systems, compressed air systems, and other pressure vessels where safety pressure relief is required.

Spring Relief Valve

The most common type of relief valve is the spring relief valve, also called a pop safety valve, because it opens and closes suddenly. Spring relief valves use the tension of a spring to withstand internal pressure in a pipe. A sudden increase in pressure will force the spring open, and pressure will vent. As the pressure level drops, the spring forces the valve closed.

 

Thermal Expansion Relief Valve

Thermal expansion relief valves are used to relieve excessive pressure caused by thermal expansion of water. Thermal expansion relief valves are used when hot water storage heaters are installed, especially when the water service has a check valve or backflow preventer installed.

Temperature and Pressure Relief Valves (TPRV/T&P)

Combined temperature and pressure relief valves (TPRV/T&P) provide fully automatic protection against both excessive temperature and pressure in an emergency condition. They are required on all hot water storage type heaters and are set to relieve at 1034 kPa (150 psi) and 99°C (210°F).

 

Vacuum Relief Valves

Vacuum relief valves allow air to enter the system to prevent negative pressure (lower than atmospheric) from developing in the tank. Vacuum conditions could siphon the water from the system, causing the tank or water heater to collapse or equipment to burn out.

Vacuum relief valves are found on the cold water inlet lines of domestic hot water supply tanks and heaters.

Applications of vacuum relief valves:

• Domestic water heaters and supply tanks
• Tabletop heaters
• Jacketed steam kettles
• Unit heaters
• Low-pressure steam systems
• Steam coil heaters

Note: A vacuum relief valve is not a backflow preventer.

A vacuum relief valve should be installed on the following:

• Domestic hot water heaters
• Supply tanks
• Unit heaters
• Steam kettles
• Other equipment where a vacuum could cause damage

Pressure Reducing Valves/Regulators

Water pressure reducing valves are used in commercial, industrial and residential applications to reduce incoming water pressure for protection of plumbing system components and to reduce water consumption. Water supply utilities use pumps and pumping stations to increase pressure in water mains to sufficient levels to supply water for firefighting, to overcome loss of pressure in the upper floors of high-rise buildings and to supply water towers and supply tanks. Pressure in water supply mains can exceed 1380 kPa (200 psi).

Most plumbing codes require water pressure reducing valves on domestic systems where the municipal water main’s pressure exceeds 551 kPa (80 psi). Higher pressures could rupture pipes, damage fixtures, and cause personal injury. Pressure-reducing valves can greatly reduce the effects of water hammer. They are available within specified pressure ranges and are adjustable within the specified ranges.

Two types of water pressure reducing valves are:

• Direct acting
• Pilot operated

Direct acting and pilot operated pressure reducing valves both use globe or angle-pattern bodies. Valves used on smaller piping diameter units are usually cast from brass; larger piping diameter units are made from ductile iron.

 

 

 

Direct acting pressure relief valves consist of globe-type bodies with a spring-loaded, heat-resistant diaphragm connected to the outlet of the valve that acts upon a spring. This spring holds a preset tension on the valve seat installed with a pressure equalizing mechanism for precise water-pressure control.

 

Float-Control Valves

Float-control valves are designed to automatically maintain a constant liquid level in a tank or reservoir. Mechanical float valves are used in commercial, industrial and agricultural applications to control high-capacity water flow. Mechanical float valves can be mounted on the tank wall.

Float-control valves can be controlled by ball floats or by remotely mounted sensing devices. A decrease in reservoir level causes the valve to move toward an open position, allowing the reservoir level to increase. An increase in reservoir level causes the valve to move toward a closed position, allowing the reservoir level to decrease.

The two float-control valves you are likely to encounter are the float-control valve in a water closet tank and the float-control valve in a water storage tank of a rural water supply system.

 

 

 

Toilet fill valves and thermal expansion relief valves are triple-function devices that consist of a toilet tank fill valve, an anti-siphon backflow preventer, and a thermal expansion pressure relief valve. This assembly is adjustable to fit all standard toilet tanks and performs the following functions:

• Limits the domestic water system’s pre-set static pressure
• Protects the temperature and pressure relief valve on the water heater
• Reduces the requirement for a thermal expansion tank or an auxiliary relief valve
• Prevents backflow from water closets.

Sliding-Stem Valves

The sliding-stem valve’s body actuates with a linear motion using a manual lever or actuator rather than a handwheel, and there are no stem threads. Sliding-stem valves are available in both gate and globe valve designs. The sliding-stem valve is useful where quick opening and closing are needed.

Most sliding-stem control valves are direct acting, which means the valve opens up wider as the stem is drawn out of the body and closes when the stem is pushed into the body.

 

 

Backflow Preventers

Cross-connection means the contamination of a potable drinking water piping system by a non-potable substance. Preventing contamination of the potable drinking water distribution system is achieved through cross-connection control. A backflow preventer is a valve specially designed, tested and approved to prevent or eliminate cross connections.

A backflow preventer may consist of any or all of the following: shutoff valves, test valves, relief valves, or air inlet valves. A backflow preventer may come as an assembly that has been tested and approved as a single unit. It should not be altered or replaced with field-constructed valves.

Types of backflow preventers include the following:

• Reduced pressure backflow assembly
• Double check valve assembly
• Pressure vacuum breaker assembly

 

 

Backflow Prevention Devices

Backflow prevention devices also prevent or eliminate cross connections of a lower risk level.

 

Valve Components and Materials

Valve Seat Ring

A seat ring is a part of the valve body assembly that provides a seating surface for the closure member. The seat ring provides a stable, uniform and replaceable shutoff surface. The seat rings may be threaded, pressed or machined into the valve body. Seat rings are typically bevelled at the seating surface. This allows the valve disk to be guided during the final stages of closing the valve. Some valve seats can be resurfaced in place with seat resurfacing tools when practical or economically suitable.

 

Types of Seating Materials

The material selected for valve seats and disks depends on the temperature, pressure and type of the fluid being controlled.

Factors to consider when selecting valve seating material include:

• Capability for replacement or resurfacing
• Hardness and resistance to wear, corrosion, erosion, galling, seizing and temperature

Valve seats can be made for relatively low pressure and temperatures and for ordinary fluids. They can be made of the following materials:

• Bronze or bronze-faced seating for bronze valves
• Iron surfaces may have iron or bronze seats
• Non-metallic composition disks such as Teflon

Teflon Polytetrafluoroethylene (PTFE)

PTFE is almost totally insoluble and chemically inert. It has high temperature resistance. Teflon PTFE ball seats require no lubrication because of natural lubricity. Teflon PTFE diaphragms and flange gaskets are used in the most severe chemical resistance applications.

Ethylene Propylene Diene Monomer (EPDM)

EPDM is a synthetic rubber used as the standard seal material for some valves. It has excellent chemical resistance on the great majority of applications, including acids, alkalis and salts at temperatures up to 90°C (194°F). EPDM is weak on organic compounds and cannot be used on oils and fats.

Fluorocarbon Rubber (FKM or FPM) (Viton)

FKM/FPM is more expensive than EPDM, and so is used as an alternate when required. It has excellent resistance to mineral acids, oils and many aliphatic and aromatic hydrocarbons. FKM/ FPM is weak on sodium hydroxide. FKM-C is a special formulation with higher resistance to chlorine services. FKM-F offers better chemical resistance on inorganic acids than standard FKM.

Chlorinated Polyethylene (CPE)

CPE is superior for sodium hypochlorite handling than other elastomers. It resists hypochlorite up to a full strength of 13%.

Nitrile (Acrylonitrile-Butadiene Copolymer, NBR)

Nitrile is also known as Buna-N. It has high chemical resistance to oil and petroleum but is weak on oxidizing media (i.e., acids). Nitrile has excellent abrasion resistance and is less expensive than FKM/FPM.

Basic Stuffing Box Designs

A stuffing box must provide an enclosure—a tight seal around the stem to retain pressure inside the piping system. The packing is placed in the stuffing box around the stem and held in place by a packing gland and/or nuts. The seal must be tight without binding the stem. Packing is subject to wear and must be periodically compressed and eventually replaced.

 

Packing that is too tight can cause the operation of the valve to be stiff. If tightening down on the packing gland nuts does not stop the leakage or causes the valve operation to be stiff, the packing should be replaced.

 

In some larger valves, a lantern ring is inserted between the turns of packing and is placed opposite to a lubrication point where grease can be injected to ease the valve operation.

Valve Stem Packing

Valve packing provides a seal between the system fluids and the valve stem. The selection and installation of valve packing material provides positive and long life. Excessive tightening of a packing nut can apply excessive pressure against a valve stem, making the valve difficult to operate and reducing packing life. Check the manufacturer’s directions for torque values and procedures. If no specific instructions are available, the proper amount of packing torque to apply is that which results in a tight seal with the least amount of friction against the valve stem.

Packing Materials

Packing is made of different types of material depending on the manufacturer’s specification for the valve and the intended service conditions. Examples of packing materials include:

• 

  Graphite l

• Teflon (PTFE)
• Spun synthetic fibre
• Glass fibre optic glaze (GFO fibre)
• Compression-braided packing (see below)
• Combinations of the above

Generic Packing Replacement Procedure

When packing needs to be replaced, avoid adding new packing to old. Remove all old packing and replace with new packing material. Following is the general procedure:

1. Examine the valve.
2. Loosen the packing gland to release any trapped pressure.
3. Remove all old packing and thoroughly clean the shaft/stem and stuffing box area.
4. Examine the shaft/stem for corrosion, nicks, scoring and excessive wear.
5. Examine other components for burrs, cracks and wear that could reduce packing life.
6. Check the stuffing box for excessive clearances and the shaft for straightness.
7. Replace any components found defective.
8. Inspect the old packing as part of failure analysis for clues as to the cause of premature packing failure.

Prepare and Install Braided Packing

Always refer to the packing manufacturer’s instructions. Ensure the equipment and packing are clean before proceeding.

1. Select the specified packing.
2. Examine the packing to be sure it is free from defects.
3. Wind the packing around a properly sized mandrel, or use a calibrated packing ring cutter.
4. Cut the packing ends cleanly, square or diagonal, according to the packing manufacturer’s instructions.
5. Cut one ring at a time, assuring that rings are sized precisely to the shaft or stem.
6. Carefully install the packing rings one at a time. Ensure the cut ends are staggered so no easy pathway may be found.
7. Install the packing nut or packing gland and nuts if used.
8. Torque the packing nuts to the manufacturer’s specifications. If no specifications are available, do not overtighten the nuts.
9. Tighten the nuts evenly to provide easy operation of the valve stem and a tight seal.
10. Test the valve under operating conditions.

Bonnet Characteristics of Gate, Globe and Angle Valves

The bonnet is the portion of the valve that contains the packing box and stems seal, and can guide the stem. It provides the principal opening to the body cavity for assembly of internal parts, or it can be an integral part of the valve body. It can also provide for the attachment of the actuator to the valve body. Typical bonnets are bolted, threaded, welded, pressure-sealed or integral with the body.

There are many types of valve bonnet. The three most common types are:

• Screwed-in bonnet
• Screwed union ring bonnet
• Bolted bonnet

Screwed-in Bonnet

The screwed-in bonnet is used on bronze gate, globe and angle valves, where frequent dismantling is not needed. The bonnet screws into the valve body, rather than over the matching threads of a valve body. The screwed-in bonnet makes a durable, pressure-tight seal, suited for many services.

 

Screwed Union Ring Bonnet

The union bonnet is ideal for smaller size valves. The union bonnet provides relatively easy access to the valve parts for inspection or maintenance. The union bonnet ring is easily screwed or removed from the valve body, providing a tight seal.

 

Bolted Bonnet

The bolted bonnet is used for larger valves or for higher pressure applications. The bonnet is adaptable to all types of gaskets. Multiple bolting permits equal sealing pressure without using excessive torque.

 

Lip-Seal Bonnet

The lip-seal bonnet and the valve body are screwed together until a firm metal-to-metal contact is made between the machined surfaces of the bonnet and the top of the body. One type of this bonnet is screwed and fillet welded to the valve body. Dismantling is accomplished by grinding off the fillet weld and unscrewing the bonnet. This valve is designed for high pressure and temperature services.

Bellows Seal Bonnet

A bellows seal bonnet is a bonnet that uses a bellows for sealing against leakage around the valve stem.

 

Pressure-Seal Bonnet

The pressure-seal bonnet is a newer style that is effective for sealing high pressures and temperatures. A pressure-seal bonnet utilizes line fluid pressure to seal the joint. As the line pressure increases, the bonnet seal gets tighter. The actual seal is at the contacting area of a wedge-shaped metal ring, making a pressure-tight metal-to-metal joint.

Self-Test D-2.1: Describe Basic Valve Types

Complete Self-Test 2.1 and check your answers.

References

BC Industry Training Authority. (2019). Piping trades apprenticeship program: Use Tools and Equipment—Level 1 harmonized [Binder]. Crown Publications, Queen’s Printer for British Columbia. https://www.crownpub.bc.ca/Product/Details/7960000261_S

• Plumber: Competency D-4 Install Valves
• Steamfitter: Competency D-1 Install Valves
• Sprinkler Fitter: Competency D-4 Install Valves

Media Attributions

All figures are sourced from Industry Training Authority (2019) and/or Camosun College (2019) and are used under the Creative Commons Attribution 4.0 (CC BY 4.0) licence unless otherwise noted. Images copyrighted by the BC Industry Training Authority are licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 (CC BY-NC-SA 4.0) licence.

• Figure 1 High pressure air valve by Peter Southwood on Wikimedia Commons is used under the CC0 1.0 public domain license.
• Figure 2 Ball valve by (Bitjungle/Wikimedia Commons) CC BY-SA 4.0
• Figure 3 Bidirectional tight butterfly valve (Heather Smith/Wikimedia commons)
• Figure 4 Pl control valve (Rafał Rygielski/Wikimedia Commons)
• Figure 5 Diverter valve with PEX connections by (Tomwsulcer/Wikimedia Commons) CC0 1.0
• Figure 6 Valve (NVgt156/Wikimedia Commons) CC BY-SA 4.0
• Figures 7a and 7b are by Audrey Curran/TRU Open Press and are subject to the CC BY-NC-SA license.
• Figures 22 Flanged gate valve, non-rising stem, and Figure 36 Wafer-type butterfly valve, is courtesy of NIBCO INC. Used with permission.
• The following figures are courtesy of Watts and are used with permission:
  • Figures 42 Flanged T pattern iron body swing-check
  • Figure 44 Split disk wafer check valve
  • Figure 48 Flanged silent check valve
  • Figure 54 Cast iron backwater valve
  • Figure 56 Combination ball and relief valves
  • Figure 70 Thermal expansion relief valves
  • Figure 74 Direct acting water pressure regulator with strainer
  • Figure 75 Steam pressure regulator
  • Figure 78 Float valve, float arm and ball float
  • Figure 79 Toilet fill valve and thermal expansion relief valve
  • Figure 82 Reduced pressure backflow assembly