Control Valve application

VALVE Body-Bonnet Design

2007-09-30T06:00:00.001-07:00

Gate valves are normally available in five different body/bonnet joint designs. They are: screwed, union, bolted-bonnet, welded-bonnet & pressure-seal.

* The screwed joint is the simplest design. However it is only used for inexpensive bronze valves that rarely if ever require disassembled.
* The union joint is also primarily used on bronze valves, but the union design allows for easier disassembly for repair and maintenance.
* The bolted-bonnet joint is the most popular joint and it is used on the vast majority of gate valves in industrial use today. Unlike threaded and union bonnet valves, the bolted-bonnet connection requires a gasket to seal the joint between the body and bonnet. On lower pressure valves, sheet gasket materials are used. ANSI Class 150 steel valves usually employ a corrugated soft iron or graphite/corrugated soft iron gasket. Valves of class 300 and higher employ either a spiral-wound or ring joint type gasket.
* The pressure-seal joint is energized by the fluid pressure in the valve body acting upon a wedge shaped, soft iron or graphite gasket wedged between the body and bonnet. On a pressure-seal valve, the higher the body cavity pressure, the greater the force on the gasket. Pressure-seal bonnets are used extensively for high-pressure high-temperature applications, such as the power industry. Pressure-seal valves are much lighter than their corresponding bolted bonnet designs. Due to the pressure energization of the seal ring, they are normally not used in pressure classes below ANSI class 600.
* Welded bonnets are a very popular body-bonnet joint for compact steel valves in sizes ½” through 2” and pressure classes 800 through 2500, where disassembly is not required. The higher pressure welded-bonnet type valves rely on threads to handle the force generated by the body cavity pressure, while a small peripheral weld bevel actually contains the pressure. Like pressure-seal valves, welded-bonnet valves are much lighter than their bolted-bonnet counterparts.

Disc Design VALVE disc or gate

2007-09-30T05:59:00.003-07:00

Gate valves can have one of two different disc designs: parallel or tapered type. Both operate on the principle of a closure element (disc or gate) sliding into a slot in the pipeline and closing off the fluid path. The tapered disc of the “wedge gate” valve is machined to match a pair of body seats set at the same angle, usually about 10o. If machined correctly, as the tapered disc engages the seats, it locks firmly into place, stopping the flow.

Three types of wedge gates are available: solid disc, one piece flexible type, and two piece split design.

* The solid wedge has been around the longest and at one time virtually all wedge gates were the solid type. The drawback to a solid design is that it does not have any flexibility and if there is any valve body/seat distortion due to extreme temperature fluctuations or pipe stresses, the solid disc can become jammed in the seats. The solid disc is still standard on bronze, cast iron, water service and compact carbon steel valves (API 602 type). Today, solid discs are usually only available as special order items on large diameter gate valves.
* The flexible wedge type is just that- flexible. By the addition of a groove or slot around its periphery, the flexible disc can adapt to temperature changes and adverse piping stresses without binding. The flexible design also is a little easier to manufacture, in that minor imperfections in the seating surface angles can be compensated for by the disc’s flexibility. The “flex-wedge” design is by far the most common type seen on commodity gate valves used in industrial applications.
* The split wedge type consists of a two-piece design with mating surfaces on the back side of each disc half. These mating surfaces allow the downward stem thrust to be uniformly transferred to the disc faces and onto the seats. This flexible design also provides protection against jamming due to thermal expansion. A disadvantage to the split design is that in “dirty” services, residue or debris can cake in between the disc halves, causing the valve to improperly seat or even jam. Split wedge designs are commonly found on stainless steel and high alloy valves, as well as many small bronze valves.

Wedge gates are guided by grooves or ribs cast or welded into the body of the valve. These wedge guides keep the disc in alignment as it opens or closes and also keeps the disc from sliding against the downstream seat during opening and closing.

The second disc design is the parallel type. Unlike the wedge type gate valve, which relies on the stem thrust to “wedge” the disc into the seats to seal, the parallel seat valve needs some assistance to seal properly. The sealing assistance is usually in the form of a spring loaded or mechanically activated spreading action between the two disc halves as the valve closes fully. On most parallel seat designs the friction and sealing force is relieved as the gate disengages from the seats.

The most common use for parallel disc valves today is in the pipeline industry, where elastomer seat seals and ambient operating temperatures make valve virtually leak proof. Parallel gates are also used in some high pressure, high temperature steam applications, to help reduce the possibility of locking the disc in the closed position due to a radical change in temperature.

Regardless of disc design or type, the gate valve closure element must come in perfect contact with seats in the valve body. The body seats may be welded, screwed, pressed or swaged in, or be integral with the valve body. Most industrial steel gate valves utilize seat rings that are welded into the valve body. For most of the 20th century the norm was screwed in seat rings in steel valves. However, advances in welding and valve repair techniques made the screwed-in rings obsolete. Seat rings and valve discs are also often overlaid with corrosion or abrasion resistant alloys to increase their service life.

VALVE Body-Bonnet Design TRIM

2007-09-30T05:59:00.001-07:00

The word “trim” is often overheard when valve professionals are talking about industrial gate valves. Trim has nothing to do with how slim and fit a valve is, rather it refers to the internal components of a valve that are exposed to great stress or subject to a harsh combination of erosion and corrosion. In a gate valve the trim components are the stem, disc seating area, body seats and backseat, if applicable. Common utility bronze or brass valves usually have trim parts of the same material as the body and bonnet. Cast and ductile iron valves have either all iron trim components or occasionally bronze trim. The term for an iron valve with bronze trim is “iron body, bronze mounted” or IBBM for short.
Because of their weldability, steel valves can be furnished with a number of different trims. Stellite, Hastelloy, 316ss, 347ss, Monel, and Alloy 20 are some of the materials regularly used for gate valve trim.

During most of the 19th century, valves were predominantly supplied with screwed end connections, even in sizes as large as 12” NPT. Since that time the flanged end connection has become the most popular. Other end connection types in use today include screwed, ring-type-joint (RTJ), Victaulic, Greyloc and water works “mechanical joint”.

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2 Responses to “VALVE Body-Bonnet Design TRIM”

1. aliaswn Says:
September 10th, 2007 at 11:01 pm

Valve assembly comprising a valve base, a valve bonnet attached thereto, a rotatable valve stem extending coaxially through the valve bonnet, a rotatable valve handle attached to the valve stem and having a plane of rotation which is generally perpendicular to the axis of the valve stem, and an indicator tab attached to the valve base or the valve bonnet and extending outward from the valve body or valve bonnet in a direction generally parallel to the plane of rotation of the valve handle. The rotatable valve handle can be disposed in at least a first position and a second position, wherein the rotatable handle when disposed in the first position renders the indicator tab invisible when viewed in a direction generally perpendicular to the plane of rotation of the valve handle, and wherein the rotatable handle when disposed in the second position renders the indicator tab visible when viewed in a direction generally perpendicular to the plane of rotation of the valve handle.
2. aliaswn Says:
September 10th, 2007 at 11:02 pm

There is a wide range of safety valves available to meet the many different applications and performance criteria demanded by different industries. Furthermore, national standards define many varying types of safety valve.

The ASME standard I and ASME standard VIII for boiler and pressure vessel applications and the ASME / ANSI PTC 25.3 standard for safety valves and relief valves provide the following definition. These standards set performance characteristics as well as defining the different types of safety valves that are used:

* ASME I valve - A safety relief valve conforming to the requirements of Section I of the ASME pressure vessel code for boiler applications which will open within 3% overpressure and close within 4%. It will usually feature two blowdown rings, and is identified by a National Board ‘V’ stamp.
* ASME VIII valve - A safety relief valve conforming to the requirements of Section VIII of the ASME pressure vessel code for pressure vessel applications which will open within 10% overpressure and close within 7%. Identified by a National Board ‘UV’ stamp.
* Low lift safety valve - The actual position of the disc determines the discharge area of the valve.
* Full lift safety valve - The discharge area is not determined by the position of the disc.
* Full bore safety valve - A safety valve having no protrusions in the bore, and wherein the valve lifts to an extent sufficient for the minimum area at any section, at or below the seat, to become the controlling orifice.
* Conventional safety relief valve - The spring housing is vented to the discharge side, hence operational characteristics are directly affected by changes in the backpressure to the valve.
* Balanced safety relief valve - A balanced valve incorporates a means of minimising the effect of backpressure on the operational characteristics of the valve.
* Pilot operated pressure relief valve - The major relieving device is combined with, and is controlled by, a self-actuated auxiliary pressure relief device.
* Power-actuated safety relief valve - A pressure relief valve in which the major pressure relieving device is combined with, and controlled by, a device requiring an external source of energy.

The following types of safety valve are defined in the DIN 3320 standard, which relates to safety valves sold in Germany and other parts of Europe:

* Standard safety valve - A valve which, following opening, reaches the degree of lift necessary for the mass flowrate to be discharged within a pressure rise of not more than 10%. (The valve is characterised by a pop type action and is sometimes known as high lift).
* Full lift (Vollhub) safety valve - A safety valve which, after commencement of lift, opens rapidly within a 5% pressure rise up to the full lift as limited by the design. The amount of lift up to the rapid opening (proportional range) shall not be more than 20%.
* Direct loaded safety valve - A safety valve in which the opening force underneath the valve disc is opposed by a closing force such as a spring or a weight.
* Proportional safety valve - A safety valve which opens more or less steadily in relation to the increase in pressure. Sudden opening within a 10% lift range will not occur without pressure increase. Following opening within a pressure of not more than 10%, these safety valves achieve the lift necessary for the mass flow to be discharged.
* Diaphragm safety valve - A direct loaded safety valve wherein linear moving and rotating elements and springs are protected against the effects of the fluid by a diaphragm.
* Bellows safety valve - A direct loaded safety valve wherein sliding and (partially or fully) rotating elements and springs are protected against the effects of the fluids by a bellows. The bellows may be of such a design that it compensates for influences of backpressure.
* Controlled safety valve - Consists of a main valve and a control device. It also includes direct acting safety valves with supplementary loading in which, until the set pressure is reached, an additional force increases the closing force.

The British Standard BS 6759 lists the following types of safety valve:

* Direct loaded - A safety valve in which the loading due to the fluid pressure underneath the valve disc is opposed only by direct mechanical loading such as a weight, a lever and weight, or a spring.
* Conventional safety valve - A safety valve of the direct loaded type, the set pressure of which will be affected by changes in the superimposed backpressure.
* Assisted safety valve - A direct loaded safety valve which, by means of a powered assistance mechanism, is lifted at a pressure below the unassisted set pressure and will, even in the event of failure of the assistance mechanism, comply with all the relevant requirements for safety valves.
* Pilot operated (indirect loaded) safety valve - The operation is initiated and controlled by the fluid discharged from a pilot valve, which is itself a direct loaded safety valve.
* Balanced bellows safety valve - A valve incorporating a bellows which has an effective area equal to that of the valve seat, to eliminate the effect of backpressure on the set pressure of the valve, and which effectively prevents the discharging fluid entering the bonnet space.
* Balanced bellows safety valve with auxiliary piston - A balanced bellows valve incorporating an auxiliary piston, having an effective area equal to the valve seat, which becomes effective in the event of bellows failure.
* Balanced piston safety valve - A valve incorporating a piston which has an area equal to that of the valve seat, to eliminate the effect of backpressure on the set pressure of the valve.
* Bellows seal safety valve - A valve incorporating a bellows, which prevents discharging fluid from entering the bonnet space.

In addition, the BS 759 standard pertaining to safety fittings for application to boilers, defines full lift, high lift and lift safety valves:

* Lift safety valve (ordinary class) - The valve member lifts automatically a distance of at least 1/24th of the bore of the seating member, with an overpressure not exceeding 10% of the set pressure.
* High lift safety valve - Valve member lifts automatically a distance of at least 1/12th of the bore of the seating member, with an overpressure not exceeding 10% of the set pressure.
* Full lift safety valve - Valve member lifts automatically to give a discharge area between 100% and 80% of the minimum area, at an overpressure not exceeding 5% of the set pressure.

The following table summarises the performance of different types of safety valve set out by the various standards.

Trim TYPES VALVE

2007-09-30T05:58:00.003-07:00

High Flow Plug and Cage Trim

The Plug and Cage trim design gives the maximum flow capacity for a cage trim choke valve. This trim type is proven for effectiveness in high flow liquid and dual phase flow.

In the closed position, the plug makes contact with a prepared shoulder in the cage to facilitate positive shut off.

This robust trim is most often furnished with linear characteristic in surface hardened stainless steel or tungsten carbide for erosive service.

External Sleeve Trim

The External Sleeve type trim uses a flow sleeve moving over the outside of a ported cage to control flow. A metal-to-metal seat design on the outside of the flow sleeve and out of the high velocity flow assures positive shut off and an extended seat life.

High erosion resistance of this trim design leads to its use in severe service that may include high pressure drops and fluids with entrained solids, such as formations sands. This trim is furnished in tungsten carbide with an equal percentage characteristic.

ED Labyrinth Trim

The ED “Energy Dissipating” disk stack is a severe service trim solution to reduce noise, prevent cavitation and with the correct material selection, resist erosion.

The disk stack consists of a multiple set of tortuous paths in parallel to each other. Several mechanisms are utilized in the design to assist with the conversion of energy into heat without problems of cavitation in liquids and the problems of high noise levels with gasses caused by high velocities.

The ED trim is typically used in high pressure drop valves in water injection and gas production/blowdown.

Lubricating Control Valve Packing

2007-09-30T05:58:00.001-07:00

A lubricator or lubricator/isolating valve is required for semi-metallic packing and is recommended for graphite asbestos and TFE-impregnated asbestos packing. The lubricator or lubricator/isolating valve combination should be installed on the side of the valve bonnet, replacing the pipe plug used with packing types not requiring lubrication. Use Dow Corning X-2 lubricant or equivalent for standard service up to 450°F(232°C) and Hooker chemical Corporation Fluorolube Lubricant or equivalent for chemical service up to 300°F (149°C). With lubricator, isolating valve, and pipe nipple (if used) completely filled with lubricant and installed on bonnet, open isolating valve (if used) and rotate lubricator bolt a full turn clockwise to force lubricant into the packing box. Close the isolating valve after each lubrication.

Replacing Threaded Seat Rings CONTROL VALVE

2007-09-30T05:57:00.001-07:00

Replacing Threaded Seat Rings CONTROL VALVE

Many conventional sliding-stem control valves use threaded-in seat rings. Severe service conditions can cause damage to the seating surface of the seat ring(s) so that the valve does not shut off satisfactorily. In that event, replacement of the seat ring(s) will be necessary.
Before trying to remove the seat ring(s), check to see if the ring has been tack-welded to the valve body. If so, cut away the weld and apply penetrating oil to the seat ring threads before trying to remove the ring. The following procedure for seat ring removal assumes that a seat ring puller, such as that shown in figure 5-4, is being used . If a puller is not available, a lathe or boring mill may be used to remove the ring(s).

1. Place the proper size seat lug bar across the seat rings so that the bar contacts the seat lugs as shown.

2. Insert drive wrench and place enough spacer rings over the wrench so that the hold-down clamp will rest about 1/4-inch above the body flange.

Slip hold-down clamp onto drive wrench and secure the clamp to the body with two cap screws (or hex nuts for steel bodies) from the bonnet. Do not tighten cap screws or nuts.

3. Use turning bar to unscrew the seat ring. Struck seat rings may require additional force on the turning bar. Slip a 3- to 5-foot length of pipe over one end of the turning bar with a heavy hammer to break the ring loose. In addition, a large pipe wrench can be used on the drive wrench near the hold-down clamp.

4. After the seat ring is loose, alternately unscrew the flange bolts (or nuts) on the hold-down clamp and continue to unscrew seat ring.

5. Before installing new ring(s), thoroughly clean threads in the body port(s). Apply pipe compound to the threads of the new seat ring(s).

Note

On double-port bodies, one of the seat rings is smaller than the other. On direct-acting valves (push-down-to-close action), install the smaller ring in the body port farther from the bonnet before installing the larger ring. On reverse-acting valves (push-down-to-open action), install the smaller ring in the body port closer to the bonnet before installing the larger ring.

Screw the ring(s) in to the body. Use the seat ring puller, lathe, or boring mill to tighten seat rings in the body. Remove all excess pipe compound after tightening. The seat ring can be spot welded in place to ensure that it does not loosen.

6. Reassemble the valve.

Replacing Stem Packing CONTROL VALVE

2007-09-30T05:56:00.000-07:00

Replacing Stem Packing CONTROL VALVE

Bonnet packing, which provides the pressure seal around the steam of a globe-style valve body, may need to be replaced if leakage develops around the stem, or inspection. Before starting to remove packing nuts, make sure there is no pressure in the valve body.
If the packing is of the split ring variety, it can be removed (with considerable difficulty) without removing the actuator by digging it out of the packing box with a narrow, sharp tool. This is not recommended, because the wall of the packing box or the stem could easily be scratched, thereby causing leakage when the new packing was installed.
Don’t try to blow out the old packing rings by applying pressure to the lubricator hole in the bonnet. This can be dangerous and frequently doesn’t work very well anyway. (Many packing arrangements have about half of the rings below the lubricator opening.)

The approved method is to :

1. Separate the valve stem and actuator stem connection.

2. Remove the actuator from the valve body.

3. Remove the bonnet and pull out the valve plug and stem.

4. Insert a rod (preferably slightly larger than the stem) through the bottom of the packing box and push or drive the old packing box and push or drive the old packing out the top of the bonnet. ( Don’t use the valve plug stem because the threads could be damaged in the process.)

5. Clean the packing box. Inspect the stem for scratches or imperfections that could damage new packing.

6. Check the valve plug, seat ring, and trim parts as appropriate.

7. Re-assemble the valve body and put the bonnet in position.

8. Tighten body/bonnet bolting in sequence similar to that described for flanges on page 100.

9. Slide new packing parts over the stem in proper sequence, being careful that the stem threads do not damaged the packing rings

10. Install the packing follower, flange, and packing nuts.

11. For spring-loaded TFE V-ring packing, tighten the packing nuts as far as they will go. For other varieties, tighten in services only enough to prevent leakage.

12. Replace and tighten the actuator on to the body. Position and tighten the stem connector to provide desired valve plug travel.

CONTROL VALVE Maintenance INTRODUCTION

2007-09-30T05:55:00.000-07:00

CONTROL VALVE Maintenance INTRODUCTION

In order to perform even routine maintenance procedures on a control valve, it is important that the maintenance man have a thorough understanding of the fundamental construction and operation of the valve. Without this knowledge, the equipment could be damaged inadvertently, or could cause injury to the maintenance man and others in the area. Most valve manufacturers in their detailed instruction and operation manuals. Usually, a sectional drawing of the equipment is also furnished to help in understanding the operation of the equipment as well as to provide identification of component parts.

In all major types of control valves, the actuator provides force to position a movable valve plug, disc, or ball in relation to a stationary seat ring or sealing surface. The moveable member should respond freely to changes in actuator loading pressure. If proper operation is not being received, service is indicated. Before any maintenance procedures are started, be sure that all line pressure is shut off and released from the valve body and also that would damage the equipment or injure personnel.

Often corporate maintenance policy or existing codes require preventive maintenance on a regular schedule. Usually such programs include inspection for damaged of all major valve components and replacement of all gaskets, O-ring seals, diaphragms, and other elastomer parts. Following is a series of commonly performed maintenance procedures and some general instructions for performing each procedure instructions are normally furnished with control valve equipment and should be carefully followed.

* Replacing Actuator Diaphragm
* Replacing Stem Packing
* Replacing Threaded Seat Rings
* Grinding Metal Seats
* Lubricating Control Valve Packing

Replacing Actuator Diaphragm ^
After isolating the valve from all pressure, relieve all spring, if possible. (On some spring and diaphragm actuators for use on rotary-shaft valve bodies. spring compression is not externally adjustable. Initial spring compression is set at the factory and does not need to be released in order to change the diaphragm.) Remove the upper diaphragm case. On direct-acting actuators, the diaphragm head assembly must be dismantled to change the diaphragm.
Most pneumatic spring-and-diaphragm actuators utilize a molded diaphragm for control valve service. The molded diaphragm facilitates installation, provides a relatively uniform effective area throughout the valve’s travel range, and permits greater travel than could be possible if a flat-sheet diaphragm were used. If a flat-sheet diaphragm is used in an emergency repair situation, it should be replaced with a molded diaphragm as soon as possible.
When re-assembling the diaphragm case, tighten the cap screws around the perimeter of the case firmly and evenly to prevent leakage.

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2007-03-16T06:49:00.002-07:00

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Equal percentage valves MATERIALS AND METHODS

2007-03-16T06:49:00.001-07:00

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VALVE TERMINOLOGY

2006-04-10T19:47:00.002-07:00

Valve Flow Coefficient (Cv) - The number of US gallons per minute of 60°F water that will flow through a valve with a one pound per square inch pressure drop

Rated Cv - The value of Cv at the valve full-open position

Rated Travel - The linear movement of the valve plug from the closed position to the valve full - open position

Leakage - The quantity of fluid passing through an assembled valve when the valve is in the closed position

On-Off Service - When the valve is used to start / stop the flow by being cycled to the full open or to full closed position

Modulating Service - When the valve is being used to throttle or regulate the flow by varying the opening between open and closed positions

Maximum shut-off Pressure - The pressure of the fluid flowing into the valve against which the valve will have to close

Service Temperature - The maximum and minimum temperature of the media

Supply Pressure - The plant air supply pressure available to operate a pneumatic actuator

Stem Torque - The force required at the valve stem to open or close the valve against system pressure and service conditions

Capactiy - Rate of flow through the valve under stated conditions

Fail - close - The condition wherein the valve port remains closed should the actuating power fail

Fail - open - The condition wherein the valve port remains open should the actuating power fail

Fail - last - The condition wherein the valve port remains in the last position should the actuating power fail

Valve body

2006-04-10T19:47:00.001-07:00

Valve body - A housing for internal parts having inlet and outlet flow connections

Bonnet - The part of the body assembly which serves as a means for mounting the actuator

Cage - A hollow cylindrical trim element that is a guide to align the movement of a valve plug with a seat ring.

Seat - The portion of the valve body where the valve plug contacts for closure.

Valve Plug - A movable part which provides a variable restriction in a port.

Valve Plug Stem - A rod extending through the bonnet assembly to position the valve plug.

Trim - The internal parts of the valve which are in contact with the controlled fluid

Port - A fixed opening inside the diameter of the seat ring through which the fluid passes

Packing Box - The part of the bonnet assembly used to seal against leakage around the valve plug stem

Actuator

2006-04-10T19:47:00.000-07:00

Actuator - An air operated mechanical device used to open and close or modulate a valve. The actuator is designed to convert air pressure into mechanical force sufficient to operate the valve.

Diaphragm - A flexible pressure responsive element which transmits the force to the actuator stem

Actuator stem - The extension of the diaphragm plate or piston for connection to the valve plug stem

Actuator spring - The spring enclosed in the yoke is to move the actuator stem in a direction opposite to that created by the diaphragm pressure

Piston - A movable pressure responsive element which transmits force to the operating fluid

Yoke - The structure by which the diaphragm case is supported rigidly on the bonnet.

Travel Indicator - A pointer to indicate the travel of the valve plug.

Travel indicator scale - A graduated scale attached to the yoke for indication of the travel.

Gate valves

2006-04-10T19:46:00.001-07:00

Gate valves (also known as knife valves or slide valves) are linear motion valves in which a flat closure element slides into the flow stream to provide shut-off. Gate valves and knife valves are designed to minimize pressure drop across the valve in the fully opened position and stop the flow of fluid completely. The direction of fluid flow does not change, and the diameter through which the process fluid passes is essentially equal to that of the pipe. Hence, they tend to have minimal pressure drop when opened fully.

Gate valves and knife valves are advantageous in applications involving slurries, as their “gates” can cut right through the slurry. They are also used in applications that involve viscous liquids such as heavy oils, light grease, varnish, molasses, honey, cream and other non-flammable viscous liquids. They are available in large sizes to better handle thick flow. However, gate valves do have low-pressure limitations, and are not optimal in applications that require cleanliness or sanitary conditions. They are excellent for use anywhere a shutoff valve is needed. They can also be used where throttling capabilities are desired, although this is not generally recommended as erosion of the seat and disc occurs due to the vibrations of the disk in throttling applications.

Gate valves are usually divided into two types: parallel and wedge-shaped. The parallel gate valve uses a flat disc gate between two parallel seats, upstream and downstream. Knife valves are of this type, but with a sharp edge on the bottom of the gate to shear entrained solids or separate slurries.

Controlling device - Knife vane
Minimum resistance to flow
Easy maintenance
Quick and easy to operate
Utilites (water & waster-water)
Slurry applications
Multiproduct lines

Globe valves

2006-04-10T19:46:00.000-07:00

Globe valves are linear motion valves with rounded bodies, from which their name is derived. They are widely used in industry to regulate fluid flow in both on/off and throttling service. Globe valves consist of the following moving parts – the disk, the valve stem, and the handwheel. The stem connects the handwheel and the disk. It is threaded and fits into the threads in the valve bonnet. The location of the valve disk in relation to the valve seat allows or restricts flow. The direction of fluid flow through the valve changes several times, which increases the pressure drop across the valve. In most cases, globe valves are installed with the stem vertical and the higher-pressure fluid stream connected to the pipe side above the disk, which helps to maintain a tight seal when the valve is fully closed.

When globe valves are open, the fluid flows through the space between the edge of the disk and the seat. These valves are commonly used as a fully open or fully closed on/off valves, but they may be used for throttling as long as fine adjustments are not required.

These linear motion valves can be used in a variety of applications as long as the pressure and temperature limits are not exceeded, and the process does not require special materials to combat corrosion. Globe valves are generally available in a variety of metal and alloy constructions, as well as plastics, to cover this wide range of industrial applications. Proper material compatibility requires knowledge of the type, concentration and temperature of the media being handled. It may be necessary to consult the manufacturer of the valve for specific properties of the materials used in the valve.

Globe valves provide the following advantages: they offer precise throttling and control and have high-pressure limits. Conversely, they offer a low coefficient of flow and are not good selections in applications that require cleanliness or sterility.

Globe valves are available in three main body types (although custom designs are available as well): angle design, Y-design and multi-piece design. Angle valves are designed so that the inlet and outlet are perpendicular, for transferring flow from vertical to horizontal. Y-design valves derive linear action from the incline between the axis of the inlet and outlet ports. The bodies of multi-piece design valves are bolted together. The inlet and outlet are not of single piece construction

Controlling device - plug
High accuracy control with wide range of controllability
Petrochemical & chemical
applications Refineries & Gas plants
Power plants
Fisher, Masoneillan, CCI

Butterfly valves

2006-04-10T19:45:00.000-07:00

Butterfly valves control flow through a circular disc or vane by turning the valve's pivot axis at right angles to the direction of flow in the pipe. They are normally used as throttling valves to control flow.

Butterfly valves are quick opening valves that consist of a metal circular disc or vane with its pivot axes at right angles to the direction of flow in the pipe, which when rotated on a shaft, seals against seats in the valve body. They are normally used as throttling valves to control flow. Butterfly valves control the flow of gas or liquid by means of a disk, which turns on a diametrical axis inside a pipe or by two semicircular plates hinged on a common spindle, which permits flow in only one direction. These valves offer a rotary stem movement of 90 degrees or less, in a compact design. Unlike ball valves, butterfly valves do not have any pockets in which fluids may become trapped when the valve is closed.

Butterfly valves are available in several body styles and seal types. The flange type or lug style can be held between flanges of any type. Wafer valves are installed between two flanges using bolts or nuts and studs, while lug style valves have metal inserts installed in the valve's bolt holes and the valve is installed between two flanges using a separate set of bolts for each flange. If the wafer style is used, avoid placing it between either slip-on or screwed flange types. Some wafer body styles will not form a proper seal. The wafer style is used more commonly and is cheaper than the lug style.

Butterfly valves offer a number of advantages when used for the proper application. They may be used in a wide variety of chemical services, they are available with small dimensions allowing for use in areas where space is limited, and they allow a high coefficient of flow. Conversely, the design of butterfly valve creates the disadvantage of not being easy to clean, and therefore should be avoided in situations that call for sterile, medical or food processing applications. Additionally, some styles may have difficulty dispensing slurries.

Butterfly valves control flow through a circular disc or vane by turning the valve's pivot axis at right angles to the direction of flow in the pipe.

Butterfly valves offer a number of advantages when used for the proper application. They may be used in a wide variety of chemical services, they are available with small dimensions allowing for use in areas where space is limited, and they allow a high coefficient of flow. Conversely, the design of butterfly valve creates the disadvantage of not being easy to clean, and therefore should be avoided in situations that call for sterile, medical or food processing applications. Additionally, some styles may have difficulty dispensing slurries. Specific application butterfly valves include air butterfly valves, sanitary butterfly valves, center line butterfly valves, butterfly control valves, and electric butterfly valves.

Butterfly valves manufacturers use many material constructions, which can be implemented depending upon the application and the flow media. These types include stainless steel butterfly valves, PVC butterfly valves, plastic butterfly valves and ceramic butterfly valves.

Controlling device - vane

Low cost & light weight
Throttling & isolation applications
Utilities (Water Supply)
Chemical Processing
Power Generation
Manufacture Keystone, Tomoe, Cooper

Valve Type

2006-03-31T09:22:00.000-08:00

Ball Valve
Needle Valve
Gauge Valve
Stainless Steel Ball Valve
Manifold Valve
Double Block and Bleed Valve
Check Valve
Process Gauge
Pressure Gauge
High Pressure Gauge
Low Pressure Gauge
Fisher Rosemount
Fisher Control Valves
Rosemount Transmitter
Pressure Regulators
Air Pressure Regulators
Volume Boosters
Pressure gauge actuators
Oliver Valves
Dwyer Instruments
Dwyer Magnehelic Pressure Gauge
McDaniel Pressure Gauge
Apollo ball valves, ball check valve, watts ball valve, Apollo ball valve, pvc ball valves, ball stop & waste valves, ¼ ball valves, watts ball valves, wkm ball valves, celcon ball valve, high pressure ball valve, keystone butterfly valve, high performance butterfly valves, high pressure butterfly valves, high pressure valve, high pressure solenoid valves, high pressure relief valves, high pressure pnumatic valves, high pressure gas valves, check valves, silent check valve, automotive check valve, Mueller check valve, electric valve actuators, electro-hydraulic valve actuators, needle valves

Pneumatic Valve

2006-03-31T09:07:00.000-08:00

2 Ways , 3 Ways , 5 Ways Direct Acting or Internal Pilot Solenoid Valves
Explosion or Non- Explosion Proof Protection & Body Material
From Brass, Bronze , Stainless Steel , Light Alloy & Others.
Connection Sizes Ranges from 1/8 inches - 1 inches NPT or inches gas.
Thermostatic Valves - Self Actuating , Internal Sensing Design
Pneumatically or Electrically operated 3 way temperature control valves
Temperature sensing valves
Bearing temperature sensing valves
High temperature sensing valves
Exhaust temperature sensing valves
Differential pressure sensors
Pressure Sensing Valves Air intake shut off valves
Engine over speed sensors
Pressure / temperature switches
Pneumatic control valves, Indicators & Accessories
Electronic Controls & Systems
Instrumentation & control panels
Gas Valves
Pressure Switches
Sensors
Pressure Gauges
Transducers, Transmitters, & Indicators
Pressure Switches
Diaphragm Seals
Bimetal Thermometers & Thermowells
Manifold Valves
Needle Valves
Solenoid Valves
Sanitary Pressure Measurement
Custom Force Measurement
BALL VALVES AND NEEDLE VALVES
HYDRAULIC INTERFACE VALVES
THREE(3) POSITION--BLOCK CENTER VALVES
BUTTON OPERATED VALVES
PALM BUTTON VALVES
PILOT OPERATED VALVES
MANUAL SHUTOFF VALVES
MAIN SUPPLY RESET AIR LATCH PILOT VALVES
MAIN SUPPLY RESET VALVES WITH REMOTE PILOT
SOLENOID OPERATED VALVES
Regulator
Volume Boosters
Transducers
Air Cylinders
Manual Ball Valve
Electric Actuators
Pneumatic Actuators

Valve Overhaul or Valve Job

2006-03-31T09:04:00.000-08:00

A Doctor Valve valve overhaul (aka "valve job") is a procedure that restores the fit of the valves to "like new," or often "better than new" condition.

It begins with a play test of the horn (when playable) so that I have a baseline for that particular horn. During this process, I make notes about any playing anomalies and well as the overall characteristics of the sound and blowing feel.

Next, the horn is disassembled, measured. and visually inspected. Some instruments will require a chem-clean, which will be done at this point. The casings are lightly honed to check for any serious washouts or other problems. The valves and casing are then precisely measured to determine the necessary amount of plating build-up.

Next, the valves are trued and sized on the hone in preparation for plating. The valve ports are then precisely shielded, so that the windways in the valves retain their exact original size.

After another cleaning, the valves are carefully packed, and sent to Anderson's. There they are built up with hard nickel plating.

Upon return from the platers, the valves are honed to a size slightly above the casing dimension, then the casings are carefully honed to the point where the valves have the exact proper fit.

Each valve is then expertly hand lapped into its respective casing. The finished piston surface to casing wall fit yields a tolerance of approximately .0005" (half a thousandth of an inch.)

The horn and parts are then ultrasonically cleaned, and the instrument is reassembled with new valve pads and felts, valve springs, and waterkey corks.

It is then tested to assure proper playing function and playing characteristics. Any final tweaks are made and the instrument is then given a complete polish job using 3M Tarni-shield polish. The finished horn is now ready for return shipping or customer pick-up.

A special note about NY Bachs and instruments of "extreme age" or with severely damaged valves: In some of these cases, it is necessary to do a two-step valve build-up process. This entails more work, and two trips to the platers. I only do this when the required build-up is too great to do in a single nickel plating step. NY Bach valves were chrome plated at the factory, and in order to achieve good results, this chrome has to be completely removed from the outer valve surfaces prior to the build-up. On some NY horns, I have been able to do the valves with a one-step plating build-up (the usual method). On the other hand, some of these instruments do require a two-step plating process, because once the chrome is removed, the valves require a bigger build than is advisable in just nickel. In these cases, the valves get a first round build in copper, are re-honed and trued, re-shielded, and then sent to Anderson's a second time for the final nickel plating.

Optimum Port Matching Valve Alignment

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An Optimum Port Matching Valve Alignment is a procedure that optimizes the valve port and casing port match-up, which improves the evenness of response of the instrument.

My basic approach to this is to NOT modify the existing metal parts. Most of the time, this is possible; sometimes it is not.

First, the trumpet is playtested, and the existing alignment is inspected. Following this inspection, custom pads are cut, installed, and adjusted with shims to optimize the alignments of the ports in the valves with the ports in the casing. I use a variety of composition (non-felt) pads which are NOT weather sensitive and maintain correct alignment for a very long time.

On many instruments, because of the way the casings and valves were drilled during manufacture, perfect alignment of all the holes is not possible. In these cases, the optimum port alignment is chosen based on my understanding of the instrument as a trumpet player and my knowledge of the physics of air flow through the instrument.

If requested, your previous pads can be bagged and tagged with specific locations indicated so that you could easily reverse the procedure, and return to your original setup.

Instrument Overhaul

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The instrument overhaul service is an extensive rebuilding and refinishing service for your instrument. It begins with a play test of the horn (when playable) so that I have a baseline for that particular horn. During this I make notes about any playing anomalies and well as the overall characteristics of the sound and blowing feel.

I then disassemble the instrument and give it an initial ultrasonic cleaning. All parts are carefully inspected for cracks, rot, and other problems that might require part replacement or patching. Depending on the findings of my inspection, I often confer with the client at this point, to determine exactly what path they wish to follow.

Sometimes it is decided that the original pieces be retained and perhaps patched over, rather than risk altering the playing characteristics with replacement parts. This is because even "identical" parts can vary slightly and can sometimes play and feel slightly different. Alternately, it may be decided to replace parts so that the instrument will look as close to new as possible when completed. If this is the case, any new parts are measured and tweaked as necessary to match up as closely as possible to the parts being replaced. This is very important because minor differences can make big playing differences, especially if you have played a horn for thirty years or so, and know the horn's characteristics totally.

If the instrument was lacquered, the lacquer (or what is left of it) will be removed. Many older instruments were finished with the old nitrocellulose lacquer; most modern instruments have a baked-on epoxy lacquer. A short discussion with my take on lacquer and lacquered instruments can be found here.

The next step is removal of the bell and leadpipe from the body of the instrument. All old solder is removed from the parts and horn body. All pieces are chemically cleaned to remove the lime scale and other crud from the inside surfaces.

If the valves are also being overhauled, the valves are prepped and sent for plating at this time. The bell and leadpipe are straightened, minor dents are removed (major dent removal is extra), and surface pitting is carefully removed, as much as safely possible. Some pitting may remain if I feel that removing all of it would make areas of the horn overly thin.

If the horn is getting any new tubes, they are now made and mounted. The body, bell and leadpipe are buffed as separate pieces ensuring total and even clean-up of the surfaces.

Now the pieces of the horn are ready for reassembly. The braces are carefully adjusted to reduce tension to a minimum. This can yield significant gains in the way an instrument plays particularly in the evenness of response throughout the entire range of the instrument.

The parts are then expertly resoldered together, and the horn and parts finished buffed. Everything then gets ultrasonically cleaned to remove all buffing residue. The parts (valve slides and valve caps) are then put back on the horn and the instrument is shipped to Anderson's for plating.

When the instrument returns from plating, the valve overhaul is completed, or the valves are expertly hand lapped in the casing to smooth the plating that deposits onto the inside casing surface. The horn and parts are then ultrasonically cleaned again and the horn reassembled with new pads, felts, valve springs, and waterkey springs and corks.

It is then tested to assure proper playing function and playing characteristics of the "new" horn are compared to the notes made prior to the overhaul. Any final tweaks are made and the instrument is then given a complete polish job using 3M Tarni-shield polish. The finished horn is now ready for return shipping or customer pick-up.

My standard trumpet overhaul charge is $635, and covers the work required on instruments in average condition, refinished in silver plate or lacquer. A trumpet overhaul with gold plating is available, and costs $1045.00.

Additional work, such as major dent removal, severe pitting removal, patching, or making replacement parts, is billed at my shop rate of $75/hr.

Instrument Replate

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The instrument replating service is sometimes an option for refinishing your instrument. It is much less involved than an overhaul and is most often used on instruments that are in very good to excellent condition.

It begins with a play test so that I have a baseline for that particular horn. The horn is then disassembled and ultrasonically cleaned.

If the instrument was lacquered, the lacquer (or what is left of it) will then be removed. Many older instruments were finished with the old nitrocellulose lacquer; most modern instruments have a baked-on epoxy lacquer. A short discussion with my take on lacquer and lacquered instruments can be found here.

If the valves are being overhauled, then the valves are prepped and sent for plating at this time. After disassembly, (and chem-cleaning, if necessary) minor surface problems are addressed and the body of the horn and the parts are carefully buffed. Everything then gets ultrasonically cleaned again to remove all buffing residue.

The slides and valve caps are then put back on the horn and the instrument is shipped to Anderson's for plating. When the instrument returns from plating, the valve overhaul is completed or the valves are expertly hand lapped in the casing to smooth the plating that deposits onto the inside casing surface.

The horn and parts are then ultrasonically cleaned again, and the horn is reassembled with new pads, felts, and corks. It is then tested to assure proper playing function.

Finally, it is then given a complete polish job using 3M Tarni-shield polish. The instrument is then ready for return shipping or customer pick-up.

Here are some examples of where the re-plate service is an appropriate choice.

A new or nearly new silver plated horn that the owner wants gold plated.
A straight, undamaged instrument, perhaps with a few minor dents or other small surface imperfections where the plating is beginning to wear through but the surface has not pitted extensively.
A new or like new lacquered instrument that the owner wants silver or gold plated (lacquer removal is not included and can be performed for a reasonable extra charge.)
Another circumstance where this service could be used is on a fragile thin instrument that is in good shape, or had any problems addressed separately, that would benefit from having a bit more metal put on for durability and for increased mass.

There are many reasons why this might not be the best choice for some instruments, so I must personally inspect the instrument before deciding that this would be an appropriate refinishing option.

CONTROL VALVE PRESSURE DROP

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CONTROL VALVE PRESSURE DROP
In most instances, the only variable when calculating the Cv required of the valve is the pressure drop (DP) across the valve. The pressure drop across a valve is always measured with the valve fully open. In HVAC applications the heat exchange coil has typically been selected (or already exists) before the valve is chosen, therefore the GPM and pressure drop of the coil should be known. For optimal control, the pressure drop across the control valve should be equal to, or slightly greater than, the pressure drop of the coil and its fittings. This will ensure that the valve will control the flow through the coil through its entire range of travel. When controlling flow for a non-coil application, the same principle applies as indicated above for coil applications. Whatever the valve is directly controlling should be viewed as a system with a specific opening at the valve. The pressure upstream and downstream of the system determine the amount of flow through the system. Therefore, the ideal pressure drop across the control valve should be equal to, or greater than, the pressure drop of the system that is being controlled.

WATER APPLICATIONS
Two-Position Control
–Ball, globe or butterfly valves can be used for this application.
–The pressure drop across the valve should be low (usually less than 2 PSI) in
its open position.
–Valves for this purpose are typically selected at line size to minimize installation
cost and pressure drop. In some applications, ball and butterfly valves can
be used one size smaller than line size without dropping enough pressure
to affect system performance.
Modulating Control
–The pressure drop across a two-way valve should be equal to, or slightly
greater than, the pressure drop of the coil and its fittings. On a three-way
valve, the pressure drop is based on the drop between the common port of
the valve and the port which you are trying to control (with the port fully
open). A typical coil pressure drop for HVAC applications is usually 3 PSI or
less. This is the reason why a 3-5 PSI pressure drop across the valve has
been used as a rule of thumb

STEAM APPLICATIONS
Steam applications can be divided into two categories depending on the steam pressure present: inlet steam pressures that are less than or equal to 15 PSIG, and those that are greater than 15 PSIG. The standard pressure drop used in the Cv equation for saturated steam is 80% of the inlet gauge pressure for steam less than or equal to 15 PSIG, and 42% of the inlet absolute pressure for steam greater than 15 PSIG. A valve used for modulating control will typically be at least one size smaller than the line size and may be two or more sizes smaller.

Low Pressure Steam (less than or equal to 15 PSIG):
–Two-Position Control: The valve is usually selected as line size.
–Modulating Control: The pressure drop across the valve for proper modulation is
typically 80% of the inlet gauge pressure. Use the steam equation below to
determine the Cv.
Example : A system with a 10 PSIG inlet pressure should have a valve sized with
an 8 PSI drop.
10 PSIG x .8 = 8 PSI

High Pressure Steam (greater than 15 PSIG):
–Two-Position Control: The valve is usually selected to be line size.
–Modulating Control: The pressure drop across the valve for proper modulation is
typically 42% of the inlet absolute pressure (absolute pressure is gauge
pressure plus local atmospheric pressure, 14.7 PSIA at sea level).
Example : A system with a 20 PSIG inlet pressure should have a valve sized with
a 14.6 PSI drop.
(20 PSIG +14.7) x.42 =14.6 PSI

VALVE SIZING
The next step in sizing any valve is to calculate the Cv requirement using the information gathered from the outline on Table A. The Cv can be determined using several methods, but the most accurate method is to use the formulas listed below. The Cv calculated should always determine the valve size selected. Remember that different valve types of the same size (globe, ball or butterfly) will have different Cv ratings. After calculating the Cv with the equation listed below, if the valve size that you initially select is smaller than line size, refer to Tables B to H to determine the valve Cv adjusted for line size.

Water Valves
Cv=Q/√(DP)	Where:	Cv	=the valve sizing coefficient
		Q	=flow in gallons per minute (GPM)
		DP	=pressure drop across the valve (PSI)
Liquids other than Water
Cv=Qx √(Sg/DP)	Where:	Cv	=the valve sizing coefficient
		Q	=flow in gallons per minute (GPM)
		Sg	=specific gravity of the liquid
		DP	=pressure drop across the valve (PSI)
Steam (Saturated)
Cv=Q/(3x √(DPxP₂ )	Where:	Cv	=the valve sizing coefficient
		Q	=Steam flow in pounds per hour (Lbs/Hr)
		DP	=pressure drop across the valve (PSI)
			=.80 (PSIG)of the valve inlet gauge pressure for steam <=15 PSIG
			=.42 (PSIA)of the valve inlet absolute pressure for steam >15 PSIG
		PSIG	=Steam gauge pressure (PSIG)
		PSIA	=Steam absolute pressure (PSIA), equal to PSIG +14.7 (at sea level)
		P₂	=Steam outlet absolute pressure (PSIA)=(Steam inlet gauge pressure +14.7) - DP
Note: It is extremely important to use PSIG for steam inlet 15 PSIG and under and PSIA for steam inlet greater than 15 PSIG.

VALVE SELECTION

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VALVE SELECTION
Once the pressure drop and subsequent Cv requirement is established, the most appropriate and cost effective valve for the application can be determined. Factors that influence the decision are:
–Fluid type (i.e. water, steam, chemicals, etc.)
–Fluid pressure and temperature
–Temperature fluctuation of the fluid (Example: Will the valve control fluid at 180 °F
then 40 °F?)
–Close-off requirements (the torque required at a specific differential pressure to
close the valve)
–Requirements for tight shut-off (allowable leakage rate; no leakage at specified
differential or an acceptable %)
–Ambient conditions (i.e. temperature, humidity, special conditions, indoor or
outdoor applications, etc.)
Valve selection can be divided into the five common HVAC applications:
1)Two-position control of hot or chilled water
2)Two-position control of steam
3)Modulating control of hot or chilled water
4)Modulating control of steam.
5)Two-position or modulating control of water or steam with the valve subjected
to a wide variation of temperature (Example:180°F hot water then 45°F
chilled water)
These five applications will be examined separately and the most cost effective valve solution that provides proper control will be noted.

1) Two-Position Control: Isolation of Hot or Chilled Water
For valve sizes 1/2"to 2", the ball valve is a very cost effective choice. Ball valves provide tight close-off for the rated differential, and in this size range have female NPT threads which make installation easy. The trim materials are stainless steel ball and stem for extended valve life. The ball valve can produce cost savings as high as 50% over a comparable globe valve alternative. For three-way operation, ball valves should only be applied in diverting service to maintain their inherent equal percentage type flow characteristics and extend seal life. For valve sizes 2-1/2"and up, the butterfly valve is the most cost effective solution. Beginning at 2-1/2", material costs and increased actuator torque requirements increase ball valve pricing beyond that of the butterfly valve. Butterfly valves offer excellent temperature isolation between the fluid and actuator, as well as tight shut-off on resilient seated models, when applied for the correct differential pressure. Butterfly valves also provide flexibility, with options for choosing the material for the body, seat and disc to extend the temperature and application range of the product.

2) Two-Position Control: Isolation of Low Pressure Steam (less than or equal to 15 PSIG)
On valves 1/2"to 6",the globe valve is the most common type, although a special ball valve assembly designed for steam has better close-off, less pressure drop, and a much higher flow rate than a globe valve of the same size. On 1/2" to 3" applications, ball valves are more cost effective than globe valves, with a much higher body pressure rating. Both the globe valve and our specially designed ball valve offer good temperature isolation between the valve and its actuator. Clark offers a complete line of globe and ball valve assemblies, with options for spring return and non-spring return actuators. On sizes 2-1/2"and up, butterfly valves should also be examined for cost effectiveness. Standard aluminum bronze valves are used for saturated steam applications <10>10 PSIG, but <30>

3) Modulating Control: Hot Water or Chilled Water Two-Way & Three-Way Applications
For valve sizes 1/2"to 3"(Two-Way)and 1/2" to 2" (Three-Way), a ball valve is a very cost effective alternate choice for the standard globe valve, providing very accurate flow control when properly sized for the application. It also offers superior close-off to a globe valve and has an equal percentage flow curve that complements the flow curve of the coil. With a higher flow rate than a globe valve of the same NPT size, a ball valve sized for the same application will usually be smaller. For those people who prefer globe valves, Clark has a wide selection of globe valves to meet most applications.

For three-way diverting applications, the ball valve is an excellent choice. In a new construction or rework situation, a three-way ball valve placed upstream of the coil that diverts flow through the coil or bypasses the coil is a very cost effective alternative to a mixing globe valve placed on the downstream side of the coil. The ball valve will achieve the same results, offering very accurate control at a cost effective price. It also has the advantage of a packing nut that is adjustable for long term wear.

Special Note on Three-Way Ball Valves Piped for Mixing Applications:
When a three-way ball valve is piped as a mixing valve instead of a diverting valve (which it was designed to be) the flow is in the opposite direction of the valve's intended design. When piped this way, the valve will not respond with an equal percentage type curve. The flow curve is highly dependent on the pressure difference of the two flow streams being mixed. Also, the seats on either side of the ball were designed for a diverting flow pattern. If this flow direction is reversed, the seats will wear prematurely. When piped as a mixing valve, the valve may or may not provide good flow control.

Three-way mixing applications are one of the most common reasons for choosing a globe valve.

For valve sizes 2-1/2"and above, the butterfly valve is a good choice if the conditions are correct. For modulating control, the butterfly valve’s Cv at a 70° angle of opening should be used to size the valve properly. Butterfly valves can control flow most effectively when operating between a 20° to 70° angle of opening. As a general rule, therefore, a butterfly valve can be used to replace a globe valve whenever the minimum required Cv for the application exceeds the published flow rate of the butterfly valve with the disc at 20° open. If the minimum Cv required is less than the flow rate published for a 20° open position, a smaller ball or globe valve would have to be used in conjunction with the butterfly valve in order to provide good modulation throughout the complete flow range required of the coil. Example: Many large air handling units have minimum heating and cooling loads that exceed the flow rate of a properly sized butterfly valve at a 20° disc open position. In this application, a butterfly valve could be used effectively to control flow.

Special Note on Ball Valves:
Clark strongly recommends the use of a stainless ball and stem for all modulating ball valves. A chromium plated bronze ball will not withstand the continuous cycling encountered in a modulating service. The chromium plate will flake away in a short period of time, creating a leakage path and will score the seal material. The stainless steel ball has no plating to flake off and, therefore, the initial microscopic layer of Teflon that creeps into the surface pores of the ball remains there as a lubrication layer. Also, the slot on the top of a chrome plated ball (where the stem engages the ball) tends to widen with extensive modulation, allowing play when changing direction of travel (i.e. the actuator will rotate and the ball will not). The stainless ball and stem is much harder and does not widen.

4) Modulating Control: Low Pressure Steam (less than or equal to 15 PSI)
Globe valve sizes 1/2"to 6", or high temperature ball valve sizes 1/2"to 3", can effectively modulate flow. Factors that affect this decision include: the cost effectiveness of each valve assembly, Cv requirements, size constraints, close-off requirements and the temperature of the application. Clark’s high temperature ball valve series with a standard port design should be applied only to low pressure steam applications when modulating the valve. At pressures above 15 PSIG, the ball valve is subject to a wear phenomenon known as wire draw, which erodes the lip of the opening of the ball and ultimately creates excessive valve leakage. For valve sizes 2-1/2"and above, butterfly valves should be considered. If the butterfly valve is being used for modulating control, the same issues apply as those discussed for modulating control of hot or chilled water. For modulating control, the valve should be used between 20° and 70° (disc position). Remember, however, that the standard aluminum bronze disc is recommended only to a temperature of 239°F (10 PSIG saturated steam). The EPDM seat, if used above the recommended temperature limit, will remold itself (permanently warp) and create a leakage path and possibly bind the valve.

5) Two-Position or Modulating Control of High Pressure Steam
Proper valve selection for high pressure steam is dependent upon the individual application. Our technical staff will gladly assist you in selecting the most appropriate and cost-effective valve solution for your application.

Globe Valve Linkages
The globe valve linkage converts the actuator's rotary motion to linear motion, which is necessary for a globe valve. The linkages are available in three types:
1) Zone up to 90 in-lb (depending on actuator's physical dimensions)
2) Low torque up to 200 in-lb
3) Medium torque up to 800 in-lb
The metallic linkage provides outstanding flexibility for custom applications and can be fitted with extra long legs for increased temperature isolation. The collar of the linkage can be custom machined, if necessary, to meet a wide variety of applications.

Clark High/Low Temperature Ball Valve Assemblies
Also in the 1/2"to 3"size, specially designed high/low temperature ball valves are a great alternative. A high/low temperature ball valve assembly includes upgraded trim materials with a stainless steel ball and stem, upgraded seat material, and a high stand-off stem adapter with extra-high brackets to further thermally isolate the actuator in high or low temperature applications.

Butterfly Valve

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Fisher provides butterfly valve solutions for unique applications. Contact your local sales office for more details.

Typical Capabilities

ANSI Class 600 and above with splined shaft
Cryogenic / extension valves (3" to 54" up to Class 900).
Erosive / Corrosive service valves (e.g.: slurry service).
Fire sentry actuator special designs
Geothermal application valves.
High Pressure ANSI Class 150/150 up to 2500.
High pressure (Class 600, 900, 1500) class 5 metal seal designs.
Inlayed T-slots
Large size butterfly valves to 96"
Noise attenuation
Nuclear Service

Restricted or derated trim valves (e.g.: Class 2500 with Class 300 trim, 24" valve with 20" trim ...)
Ring type joints
Special alloys
Spray on coatings
Special face to face
Special flanges (API, DIN, AWWA, butt weld end)
Special mounting of non-Fisher actuators on Fisher valves
Steam/heat traced body and disc
Swing through valves (A11/A41/8560/8532)
Tandem linkage designs.