CHAPTER 46

VALVES

2020 ASHRAE Handbook—HVAC Systems and Equipment

ENG. HUSSAIN SHARAHILI

NOTE: All information it has been extracted from 2020 ASHRAE Handbook—HVAC
Systems and Equipment already, and any pictures will be added to this document
will be taken from the internet for better understanding, furthermore any other
information adopted from other standards, must be mentioned the names of
standards here for your reference.

Other Standards for Your Reference:

• American Society of Plumbing Engineers (ASPE), Volume 4 Chapter 3.

ENG. HUSSAIN SHARAHILI

 Table of Contents

1- Definition of Valve……………………………………………………………………………….
2- Functions of Valves……………………………………………………………………………..
3- Types of Valves……………………………………………………………………………………
4- Selection and the conditions that should be following before selecting
valves………………………………………………………………………………………………….
5- Water Hummer ………………………………………………………………………………
6- Cavitation……………………………………………………………………………………….
7- Noise………………………………………………………………………………………………
8- The materials that made of valves…………………………………………………..
9- Style body of valves ………………………………………………………………………..
10- Body Ratings…………………………………………………………………………………….
11- Control Valve Flow Characteristics……………………………………………………
12- Control Valve Sizing………………………………………………………………………….

ENG. HUSSAIN SHARAHILI

What is the valve?
The valve is elements put it on the pipeline for controlling of the fluid properly.

Functions of valves:
There are many different uses of valves such as:
• Starting, stopping, and directing flow.
• Regulating, controlling, or throttling flow.
• Preventing backflow.
• Relieving or regulating pressure.

Types of Valves:
There are many types of valves, and we will be mentioned here generally without
any more details, then we will explain all of them:
• Manual Valves.
• Automatic Valves.
• Balancing Valves.
• Multiple Purpose Valves.
• Safety Devices.
• Pressure Reducing Valves.
• Check Valves.
• Stop-Check Valves.
• Backflow Prevention Devices.

Manual Valves:
Any valve it has controlled by hands it’s called manual valves, and we have 5 types
of manual valves:

• Globe Valve.
• Gate Valva.
• Butterfly Valve.
• Ball Valve.
• Plug Valve.

ENG. HUSSAIN SHARAHILI

Globe Valves:
• Globe valves are used to stop or control the flow of fluids in a pipeline.
• Globe valves are most frequently used in smaller diameter pipes but are
available in sizes up to 12 in.
• They are used for throttling duty where positive shutoff is required.
• Globe valves have a relatively high pressure drop when fully open and
therefore should be used for throttling (flow control) rather than shutoff
(stop flow) applications.
• Three-way globe valves are also selected based on flow pattern (either
mixing or diverting).
• Globe valves for controlling service should be selected by class, and whether
they are of the straight-through or angle type, composition disk, union or
gasketed bonnet, threaded, and solder or grooved ends.

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 Figure 2 Globe valve Figure 3 Globe valve Y- pattern type
Figure 1 Globe valve angle type
straight-through type

Methods of joining for globe valve:

Figure 4 Solder globe valve Figure 5 Flanged globe valve

Figure 3 Threaded globe valve.

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Gate Valves:
• Gate valves are intended to be fully open or completely closed and for
maintenance.
• They are designed to allow or stop flow and should not be used to regulate
or control flow.
• Various wedges for gate valves are available for specific applications.
• When we can’t reach the valve because the location is not suitable in this
case, we must provide chain wheel or hummer blow – operator with valve.

ENG. HUSSAIN SHARAHILI

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Plug Valves:
• A plug valve is a manual flow control device for fluid.
• It operates from fully open to completely shut off within a 90° turn.
• Lubricated plug valves are usually furnished in gas applications.

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Ball Valves:
• A 90° turn of the handle changes operation from fully open to fully closed.
• Ball valves for shutoff service may be fully ported.
• Ball valves for throttling or controlling and/or balancing service should have
a reduced port with a plated ball and valve handle memory stop.
• Ball valves may be of one-, two-, or three-piece body design (Figure 6).

ENG. HUSSAIN SHARAHILI

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Butterfly Valves:
• Only a 90° turn of the valve disk is required to change from the full-open to
the closed position.
• Butterfly valves may be manually operated with hand quadrants (levers) or
gear wheel operators, which are commonly used on larger valves.
• Butterfly valve bodies may be wafer style or lugged style.
• Butterfly valves may be provided with an extended shaft for automatic
operation by an actuator.
• Special attention should be paid to manufacturers’ recommendations for
sizing an actuator to handle the torque requirements.

ENG. HUSSAIN SHARAHILI

 • Butterfly valve characteristics include simple and compact design, a low
corresponding pressure drop, and fast operation. Quick operation makes
them suitable for automated control, and the low-pressure drop is suitable
for high flow.
• Butterfly valve sizing for on/ off applications should be limited to pipe sizing
velocities given in Chapter 22 of the 2017 ASHRAE Handbook—
Fundamentals.
• Butterfly valve for throttling control applications, the valve coefficient sizing
presented in the section on Automatic Valves must be followed.

Figure 6 Butterfly Valve with extended shaft and electric actuator

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Figure 8 Wafer Style
Figure 7 Butterfly valve with Figure 9 Lug Style
gear wheel

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Automatic Valves:
Automatic valves are commonly considered as control valves and consist of two
things: a valve body and an actuator.

The valve body and actuator may be designed so that the actuator is removable
and/or replaceable, or the actuator may be an integral part of the valve body.

This section covers the most common types of valve actuators and control valves
with the following classifications:
• Two-way globe valve bodies (single- and double-seated).
• Three-way globe valve bodies (mixing and diverting).
• Ball valves (two- and three-way).
• Butterfly valves (two- and three-way).
Actuators:
The valve actuator converts the controller’s output, such as an electric or
pneumatic signal, into the rotary or linear action required by the valve (stem),
which changes the control variable (flow).
Sizes of Actuators:
Selection of the actuator takes into account the design requirement for the control
signal, fail-safe operation, ambient conditions, and required close-off pressure
rating of the valve assembly.

ENG. HUSSAIN SHARAHILI

Types of Actuators:
The most common types of actuators used on automatic valve applications are
solenoid, thermostatic radiator, pneumatic, electric gear train motor, electronic,
and electrohydraulic.

Solenoids:
• Solenoid valves are used to control the flow of hot or chilled water and
steam and range in size from 1/8 to 2 in. pipe size.

Thermostatic Radiator Valves:

Thermostatic radiator valves are self-powered and do not require external energy
source radiator valves are available for a variety of installation requirements with
remote-mounted sensors or integral-mounted sensor and remote or integral set
point adjustment (Figure 11).

ENG. HUSSAIN SHARAHILI

Two-Way Valves:
• In a two-way automatic valve, the fluid enters the inlet port and exits the
outlet port either at full or reduced volume, depending on the position of
the stem and the disk in the valve.
• Two-way globe valves may be single- or double-seated.
• In the single-seated globe valve, one seat and one plug-disk close against
the stream. The style of the plug-disk varies depending on the requirements
of the designer and the application. For body comparison, see Figure 9 in
Chapter 7 of the 2017 ASHRAE Handbook— Fundamentals.
• In the double-seated globe valve is a special application of the two-way valve
with two seats, plugs, and disks, and is generally applied where the close-
off pressure is too high for the single-seated valve.

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Three-Way Valves:
• Three-way valves either mix or divert streams of fluid. Figure 12 shows some
common applications for three-way valves. Figure 8 in Chapter 7 of the 2017
ASHRAE Handbook—Fundamentals shows typical cross sections of three-
way mixing and diverting globe valves.
• In some limited applications, such as a cooling tower control, a diverting or
bypass valve must be used in place of a mixing valve.
• In most cases, a mixing valve can perform the same function as a diverting or
bypass valve if the companion actuator has a very high spring rate.
• Otherwise, water hammer or noise may occur when operating near the seat.

ENG. HUSSAIN SHARAHILI

Ball valves (two- and three-way):
• Ball valves coupled with electronic direct-coupled actuators are common in
HVAC control applications because it is easy to match the movement of the
90° actuator travel to the quarter-turn movement of the ball valve.

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Butterfly valves (two- and three-way):
• Butterfly valves are used in two-position and modulating applications.
• Advantages of butterfly valves are their ability to provide a bubble tight
close off against higher pressures, their lighter weight, and compact size.
• Butterfly valves are manufactured as two-way valves. In some applications
where there is a need for a three-way valve application, two butterfly valves
are connected to a piping tee and cross-linked to operate as either three-
way mixing or three-way bypass valves (Figure 14).
• When sizing a butterfly valve for a modulating application, use the Cv rating
at 60° or 70° rotation; for two-position (on/off) applications, use the 90° Cv
rating. It is also important to follow the manufacturer’s guideline for the
butterfly valve rating for maximum fluid velocity, because exceeding this
figure can shorten the valve’s life expectancy.

ENG. HUSSAIN SHARAHILI

Pressure-Independent Control Valves:
• Pressure-independent control valves (PICVs; Figure 15) are control valves
coupled with an internal method of differential pressure regulation to
eliminate variances of flow caused by differential pressure fluctuations
across the valve assembly.

ENG. HUSSAIN SHARAHILI

Special-Purpose Valves:
• One type of four-way valve is used to allow separate circulation in the boiler
loop and a heated zone.
• Another type of four-way valve body is used as a changeover refrigeration
valve in heat pump systems to reverse the evaporator to a condenser
function.
• Six-way valves are commonly used with four-pipe chilled-beam systems
having two coil connections (supply and return), which limits output to the
chilled beam to either heating, cooling, or neither.
• Float valves are used to supply water to a tank or reservoir or serve as a
boiler feed valve to maintain an operating water level at the float level
location (Figure 13).

Figure 10 This Figure 13

Figure 11 Six Way Valves

Figure 12 Four Way Valves

ENG. HUSSAIN SHARAHILI

Foot Valves:
The basic function of a foot valve is to prevent water from flowing back down the
pipe. It can also be described as a foot valve that would only allow the pump to pull
water up but does not allow the water to flow back down.

Foot valves are used to prevent the backward flow of water through the pipe
when the water pump is turned off then the water still inside of the pipe.

Automatic Air Vent Valve:

An automatic valve for the removal of air from fluid transport lines. All air that
enters the valve body is discharged.

Needle valves:
Needle valves are commonly used to control flow and protect delicate gauges from
damage caused by sudden pressure surges of liquids and gases. They're ideal for
systems using lighter and less viscous materials with low flow rates.

ENG. HUSSAIN SHARAHILI

BALANCING VALVES:
• Balancing valves are placed in the distribution system to adjust water flow
to a terminal, branch, zone, riser, or main.
• The valve should be located on the leaving side of the hydronic branch.
• Flow Balance Valve Location: Supply or Return Side of the Coil.
• Balancing valves should be placed on the return side of coils whenever
possible. Why? Because this location helps reduce air and noise problems
within the system.

Two approaches are available for balancing hydronic systems:

1- A manual valve with integral pressure taps and a calibrated port, which
allows field proportional balancing to the design flow conditions.
2- Automatic flow-limiting valve selected to limit the circuit’s maximum flow
to the design flow.
Pictures on a manual balancing valve:

ENG. HUSSAIN SHARAHILI

Automatic Flow-Limiting Valves:
• A differential pressure-actuated flow control valve, also called an automatic
flow-limiting valve (Figure 21), regulates the flow of fluid to a preset value
when the differential pressure across it is varied. This regulation prevents
an overflow condition in the circuit where it is installed, even when other
system components are changing (modulating valves, pump staging, etc.).
• A typical performance curve for the valve is shown in Figure 22.
• The flow rate for the valve is set.
• The flow curve is divided into three ranges of differential pressure: the start-
up range, the control range, and the above-control range.

ENG. HUSSAIN SHARAHILI

Balancing Valve Selection:
• Balancing valves should be selected with 0.45 to 1 psi pressure drop at the
branch design flow when fully open.
• Too small pressure drops affect the accuracy of the flow measurements,
causing inadequate balancing.
• Too-high pressure drops reduce the control valve’s authority, affecting the
controlled variable (e.g., room temperature) stability, and produce
unnecessary friction losses.
• See Chapter 39 of the 2019 ASHRAE Handbook—HVAC Applications for
balancing details.

MULTIPLE-PURPOSE VALVES:
• Multiple-purpose valves are made in straight pattern or angle pattern.
• The valves can provide shutoff for servicing or can be partially closed for
balancing.
• Pressure gage connections to read the pressure drop across the valve can be
used with the manufacturer’s calibration chart or meter to estimate the flow.
• Means are provided to return the valve to its as-balanced position after
shutoff for servicing.
• The valve also acts as a check valve to prevent backflow when parallel
pumps are used and one of the pumps is cycled off.
• Figure 23 shows a straight pattern multiple-purpose valve designed to be
installed 5 to 10 pipe diameters from the pump discharge of a hydronic
system.
• Figure 24 shows an angle pattern multiple-purpose valve installed 5 to 10
pipe diameters downstream of the pump discharge with a common gage
and a push button trumpet valve manifold to measure the differential
pressure across the strainer, pump, or multiple-purpose valve. From this,
the flow can be estimated.
• The differential pressure across the pump suction strainer can also be
estimated to determine whether the strainer needs servicing.

ENG. HUSSAIN SHARAHILI

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SAFETY Devices:
• The terms safety valve, relief valve, and safety relief valve are sometimes
used interchangeably, although the devices generally provide a similar
function (safety).
• They have important differences in their modes of operation and
application in HVAC systems.

• Safety valves open rapidly (pop-action). They are used for gases and vapors (e.g.,
compressed air and steam).
• Relief valves open or close gradually in proportion to excessive pressure. They are used
for liquids (e.g., unheated water).
• Safety relief valves perform a dual function: they open rapidly (pop-action) for gases and
vapors and gradually for liquids. Typical HVAC application is for heating water.
• Temperature-actuated pressure relief valves (or temperature and pressure safety relief
valves) are activated by excessive temperature or pressure. They are commonly used for
potable hot water.
• Application of these safety devices must comply with building codes and the
ASME Boiler and Pressure Vessel Code.
• Safety valve construction, capacities, limitations, operation, and repair are
covered by the ASME Boiler and Pressure Vessel Code.
• For pressures above 15 psig, refer to Section I. Section IV covers steam
boilers for pressures less than 15 psig. Unfired pressure vessels (such as
heat exchange process equipment or pressure-reducing valves) are covered
by Section VIII.
• The capacity of a safety valve is affected by the equipment on which it is
installed and the applicable code.
• Valves are chosen based on accumulation, which is the pressure increase
above the maximum allowable working pressure of the vessel during valve
discharge.
• Section I valves are based on 3% accumulation.
• Accumulation may be as high as 33.3% for Section IV valves and 10% for
Section VIII.
• To properly size a safety valve, the required capacity and set pressure must
be known.
• On a pressure-reducing valve station, the safety valve must have sufficient
capacity to prevent an unsafe pressure rise if the reducing valve fails in the
open position.

ENG. HUSSAIN SHARAHILI

 • The safety valve set pressure should be high enough to allow the valve to
remain closed during normal operation yet allow it to open and reseat
tightly when cycling.
• A minimum differential of 5 psi or 10% of inlet pressure (whichever is greater)
is recommended.

When installing a safety valve, consider the following:

• Install the valve vertically with the drain holes open or piped to drain.
• The seat can be distorted if the valve is overtight, or the weight of the
discharge piping is carried by the valve body. A drip-pan elbow on the
discharge of the safety valve prevents the weight of the discharge
piping from resting on the valve (Figure 25).
• Use a moderate amount of pipe thread lubricant (first two to three
threads) on male threads only.
• Install clean flange connections with new gaskets, properly aligned
and parallel, and bolted with even torque to prevent distortion.
• Wire cable or chain pulls attached to the test levers should allow for a
vertical pull, and their weight should not be carried by the valve.
Testing of safety valves varies between facilities depending on operating
conditions:
• Under normal conditions, safety valves with a working pressure under 400
psig should be tested manually once per month and pressure-tested once
each year.
• For higher pressures, the test frequency should be based on operating
experience.
• When steam safety valves require repair, adjustment, or set pressure
change, the manufacturer or approved stations holding the ASME V, UV,
and/or VR stamps must perform the work. Only the manufacturer is
allowed to repair Section IV valves.

Figure 13 Pressure and Temperature

Relief Valves

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PRESSURE-REDUCING VALVES:
• A Pressure Reducing Valve (PRV) is an Automatic Control Valve designed to
reduce a higher unregulated inlet pressure to a constant, reduced
downstream (outlet) pressure regardless of variations in demand and/or
upstream (inlet) water pressure.
• The amount of pressure drops below the set pressure that causes the valve
to react to a load change is called droop.
• To properly size these valves, only the mass flow of steam, the inlet
pressure, and the required outlet pressure must be known.
• Valve line size can be determined by consulting manufacturers’ capacity
charts.
• Because of their construction, simplicity, accuracy, and ease of installation
and maintenance, these valves have been specified for most steam-
reducing stations.

ENG. HUSSAIN SHARAHILI

Makeup Water Valves:
• A pressure-reducing valve is normally provided on a hydronic heating or
cooling system to automatically fill the system with domestic or city water
to maintain a minimum system pressure.
• This valve may be referred to as a fill valve, PRV fill valve, or automatic PRV
makeup water valve, and is usually located at or near the system expansion
tank.
• Local plumbing codes may require a backflow prevention device where the
city water connects to the building hydronic system (see the section on
Backflow Prevention Devices).

Figure 16 PRV Valve Figure 15 PRV Valve Figure 14 PRV Valve

ENG. HUSSAIN SHARAHILI

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CHECK VALVES:
• Check valves prevent reversal of flow, controlling the direction of flow rather
than stopping or starting flow.
• Some basic types include Lift check, swing check, ball check, wafer check,
silent check, and stop-check valves.
• Most check valves are available in screwed and flanged body styles.

ENG. HUSSAIN SHARAHILI

Swing check valves:
• Have hinge-mounted disks that open and close with flow (Figure 28).
• The seats are generally made of metal, whereas the disks may be of metallic
or nonmetallic composition materials.
• Nonmetallic disks are recommended for fluids containing dirt particles or
where tighter shutoff is required.
• The Y-pattern check valve has an access opening to allow cleaning and
regrinding in place.
• Pressure drop through swing check valves is lower than that through lift
check valves because of the straight-through design.

ENG. HUSSAIN SHARAHILI

Lift Check Valves:
• have a body similar in design to a globe or angle valve body with a similar
disk seating.
• The guided valve disk is forced open by the flow and closes when the flow
reverses. Because of the body design, the pressure drop is higher than that
of a swing check valve.
• Lift check valves are recommended for gas or compressed air or in fluid
systems not having critical pressure drops.

Figure 17 Lift Check Angle Valve

Ball Check Valves:
• Are similar to lift checks, except that they use a ball rather than a disk to
accomplish closure.
• Some ball checks are specifically designed for horizontal flow or vertical up
flow installation.

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Wafer Check Valves:
• Are designed to fit between pipe flanges similar to butterfly valves and are
used in larger piping (4 in. diameter and larger).
• Wafer check valves have two basic designs: (1) dual spring-loaded flapper,
which operates on a hinged center post, and (2) single flapper, which is
similar to the swing check valve.

Figure 18 Dual Spring Wafer Check Valve Figure 19 Single flapper Wafer Check
Valve
Silent or spring-loaded check valves:
• This valve greatly reduces water hammer, which may occur with slow-closing
check valves like the swing check.
• Silent check valves are recommended for use in pump discharge lines.

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STOP-CHECK VALVES:
• Stop-check valves can operate as both a check valve and a stop valve.
• Stop-check valves are used for shutoff service on multiple steam boiler
installations, in accordance with the ASME Boiler and Pressure Vessel Code,
to prevent backflow of steam or condensate from an operating boiler to a
shutdown boiler.
• They are mandatory in some jurisdictions. Local codes should be consulted.

BACKFLOW PREVENTION DEVICES:

• Backflow prevention devices prevent reverse flow of the supply in a water
system.
• A vacuum breaker prevents back siphonage in a non-pressure system,
whereas a backflow preventer prevents backflow in a pressurized system
(Figure 29).

Backflow Prevention Devices Selection:

Vacuum breakers and backflow preventers should be selected based on the local
plumbing codes, the water supply impurities involved, and the type of cross-
connection.

1- Impurities are classified as:

• contaminants (substances that could create a health hazard if
introduced into potable water).
• Pollutants (substances that could create objectionable conditions but
not a health hazard).

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 2- Cross-connections are classified as:
• Non pressure or pressure connections.
• In a non-pressure cross-connection, a potable-water pipe
connects or extends below the overflow or rim of a receptacle at
atmospheric pressure. When this type of connection is not
protected by a minimum air gap, it should be protected by an
appropriate vacuum breaker or an appropriate backflow
preventer.
• In a pressure cross-connection, a potable-water pipe is connected
to a closed vessel or a piping system that is above atmospheric
pressure and contains a nonportable fluid. This connection should
be protected by an appropriate backflow preventer only. Note
that a pressure vacuum breaker should not be used alone with a
pressure cross-connection.
• Vacuum breakers should be corrosion resistant.
• Backflow preventers, including accessories, components, and
fittings that are 2 in. and smaller, should be made of bronze with
threaded connections.
• Those larger than 2 in. should be made of bronze, galvanized
iron, or fused epoxy-coated iron inside and out, with flanged
connections.
• All backflow prevention devices should meet applicable
standards of the American National Standards Institute, the
Canadian Standards Association, or the required local
authorities.

Backflow Prevention Devices Installation:

• Vacuum breakers and backflow preventers equipped with
atmospheric vents, or with relief openings, should be installed
and located to prevent any vent or relief opening from being
submerged.
• They should be installed in the position recommended by the
manufacturer.
• Backflow preventers may be double check valve (DCV) or reduced
pressure zone (RPZ) types. Refer to manufacturers’ information
for specific application recommendations and code compliance.

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 Figure 20 Double Check Valve Figure 21 Double Check Valve

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 Figure 24 PRZ Valve

Figure 22 PRZ Valve

Figure 23 PRZ Valve

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Selection and the conditions that should be following before selecting valves:
Each valve style has advantages and disadvantages for the application. The
questions listed in the section on Fundamentals must be evaluated carefully.

Water Hummer:
• When flow stops because of closing the valve quickly and suddenly,
the pressure increase is independent of the working pressure of
the system. For example, if water is flowing at 5 fps and a valve is
instantly closed, the pressure increase is the same whether the
normal pressure is 100 psig or 1000 psig.
• In general, it is important to avoid quickly closing valves in an
• HVAC system to minimize the occurrence of water hammer.

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Cavitation:
• Cavitation occurs when the pressure of a flowing fluid drops below
the vapor pressure of that fluid (Figure 2).
• Cavitation happens in the pump on the suction line aslo.

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Noise:
• Chapter 22 of the 2017 ASHRAE Handbook—Fundamentals
points out that limitations are imposed on pipe size to control the
level of pipe and valve noise, erosion, and water hammer
pressure.
• ISA Standard 75.01 compiles prediction correlations to develop
control valves for reduced noise levels.
The materials that made of valves:

Style body of valves:

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Body Ratings:

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Control Valve Flow Characteristics:

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Control Valve Sizing:

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