Ball Valve How it Works

What is a ball valve ?



A ball valve is a rotational motion (quarter turn),quick rotating valve that uses a ball-shaped disk to stop or start or regulate fluid flow.The function of this type of valves,ball is same as of disk in Globe valve. When the valve handle is turned to open the valve, the spherical ball rotates to a position where the hole through the ball is in-line with the valve body inlet and outlet of flow. When the valve is shut, the ball is rotated so that the hole is perpendicular to the flow openings of the valve body and the flow is stopped.






ball valve animation



ball valve actuators are of the quick-acting type, which require a 90° turn of the valve handle to operate the valve. Some ball valve actuators such as planetary gear-operated, allow the use of a relatively small operating force to operate a fairly large valve.



Some ball type valves have been developed with a spherical surface coated plug that is off to one side in the open position and rotates into the flow passage until disk blocks the flow path completely.




Advantages of ball valves



A ball valve is the least expensive of any valve arrangement


ball valve offers low maintenance costs.


ball valves are compact, require no lubrication, and give tight sealing with low torque.



Disadvantages of ball valves



Ball type valves(especially old designs) have relatively poor throttling characteristics.


In a throttling position, the partially exposed seat of ball valve rapidly erodes because of the impingement of high velocity flow.


ball valve pictures


ball valve



Valve Materials in ball valves



Balls are usually metallic with trim (seats) produced from elastomeric (like rubber) materials. Plastic construction in ball valves is also available.


The resilient seats for ball valves are made from teflon (TFE), filled TFE, Nylon, Buna-N, Neoprene, other combinations of these materials.Because of these elastomeric materials ball valves cannot be traditionally used at elevated temperature and engineer must take care while selecting ball valve for particular application.



ball valve Port Patterns ,Bonnet & Stem Design



ball valves are available in the venturi, reduced, and full port pattern. The full port


pattern has a ball with a bore equal to the inside diameter of the pipe.



The stem and ball connection is explained here.The stem in a ball valve is not fastened to the ball. It normally has a rectangular portion at the ball end which fits into a slot cut into the ball. The enlargement permits rotation of the ball as the stem is turned. A bonnet cap fastens to the body, which holds the stem assembly and ball in place. Adjustment of the bonnet cap permits compression of the packing, which supplies the stem seal. Packing for ball valve stems is usually in the configuration of die-formed packing rings normally of TFE, TFE-filled, or TFE-impregnated material. Some ball valve stems are sealed by means of O-rings rather than packing.








ball valve Positions



Some ball valves are equipped with stops that permit only 90° rotation. Others do not have stops and may be rotated 360°. Whether there is stop available or not, a 90° rotation is all that is required for closing or opening a ball valve.



The handle indicates valve ball position. When the handle lies along the axis of the valve, the valve is open. When the handle lies 90° across the axis of the valve, the valve is closed. Some ball valvestems have a groove cut in the top face of the stem that shows the flowpath through the ball. Observation of the groove position indicates the position of the port through the ball. This feature is particularly advantageous on multiport ball valves.

What is a Gate Valve?

From http://www.higeroindustry.com/

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. They are one of the most common valves used.

Cage control valve leakage treatment

An Overview

    FV-201 anti-surge control valve is concentrated nitric workshop production of a very important field of a regulating valve , if leaking spool valve, process gas in the NO ₂ gas directly into the exhaust through the regulating valve, so that the exhaust gas in NO ₂ gas concentration excessive emissions, reach environmental requirements. In the November 3, 2010, concentrated nitric sudden increase in the concentration of exhaust workshop, rising from about 100ppm to 600ppm or so, after professional and technical staff to discuss, analyze, judge, agreed that the exhaust gas concentration causes the spool valve FV-201 causing a leak. In order to discharge the requirements of environmental protection, it is necessary to FV-201 control valve for maintenance treatment, the regulating valve leakage reached Ⅴ grade level requirements.

    2 valve structure

    Valve FV-201 manufactured by CCI cage cylinder straight travel valve, the medium flow is low prices, in use, because the original balanced valve plug easily damaged O-ring problem, after the factory will balance structure changed to a non-balanced, and by calculating the existing double-acting cylinder diameter and supply pressure used under unbalanced, still meet the conditions regulating valve under pressure in grade Ⅴ leakage class requirements. Regulating valve seal in the form of single-seat metal seal, linear flow characteristics, nominal diameter DN250, CV value of 900, the cage is designed to reduce the fluid noise porous buck. Double-acting cylinder actuator is equipped with a gas tank, make sure the valve in case of interruption of gas supply can also be emergency opening, to prevent compressor surge occurs.

    3 FV-201 control valve leaks and leakage checks

    3.1 leak check

    Produced in the process with the maintenance stop condition, the FV-201 with inlet and outlet valve regulating valve inlet flange removal separate blind blind flange with DN250 good regulator valve inlet, and add 0.30MPa instrument air source, valve seat, valve parts with soapy water leak, leak observed to determine whether the spool wire seal leaks, or leakage at the valve seat gasket.

    Through the inspection, there is no leakage at the valve seat gasket, leak hole in the cage, and are therefore determined to be in the spool seal leakage.

    3.2 Water pressure leak test

    According GB/T17213.4-2005 "Industrial Control Valves inspection and routine testing in Part IV: Inspection and routine testing" standard leak test, control valve inlet valve cavity to be 0.30MPa irrigation water pressure leak test, collected at the outlet valve leakage of water (see Figure 1), the leakage amounted to 2200ml/min, a large amount of the control valve leakage.

Figure 1 just off valve leaks when pressure test

    According GB/T17213.4-2005 "Industrial Control Valves inspection and routine testing in Part IV: Inspection and routine testing" in 7.3.3 leak specifications, calculate FV-201 control valve hydraulic test Ⅴ grade level requirements leak leak volume. Table 1.

Table 1 FV-201 control valve hydraulic test Ⅴ grade level leakage leakage

    Since FV-201 hydraulic test amount of leakage is 2200ml/min, far greater than Grade Ⅴ valve leakage level required amount of leakage 0.225ml/min, so the need for valve leakage for processing.

FQ647F_16C pneumatic coal injection valve DN32 Design

 Valve models should normally be expressed valve type, drive type, connection type, structural features, sealing surface material, body material and nominal pressures and other factors.Standardization of valve type valve design, selection, sales provides a convenient. Today the type of valve and materials more and more, the valve for the model is more complicated. Although the preparation of a unified standard valve type, but can not meet the growing needs of the development of industrial valves. At present, the valve manufacturer generally uniform numbering method, where the method can not be used uniform numbers, each manufacturer according to their needs develop numbering method. FQ647F-16C pneumatic coal injection valve model based on national standards and the development of methodologies Shantou valve plant shown in Figure 1.

Figure 1 valve type arrangement

     

    Two pairs of valve performance requirements

    FQ647F-16C pneumatic coal injection valve DN32 with reference to international advanced design and manufacture of the prototype of the new structure dedicated coal injection valve, is the metallurgical blast furnace pulverized coal injection system on the device-specific accessories. In order to meet different specifications, different kinds of steel, coal injection valve by turning the blast furnace pulverized coal combustion play a role in raising the temperature of the blast furnace, coal injection system must be ready quickly open and close in order to meet the temperature requirements, and its rapid opening , turn-off is controlled by the computer to achieve. Therefore, pulverized coal pneumatic valve must have the following three characteristics:

    (1) The response speed required to complete in 1 ~ 2s open and close operation to meet the requirements of automatic control computer;

    (2) to stabilize the pressure in the pressure pipe and pipe medium coal incidental leakage of harmful gases, so pneumatic coal injection valve does not leak;

    (3) To protect the sealing surface being pulverized coal injection erosion and wear, do not appear sealing surface strain and stuck (rotation is not flexible) phenomenon, so you must use the fully open or fully closed, prohibited by throttling.

    Three ball design

    3.1 Work

    The ball valve body and the pneumatic device by the two parts. Opening and closing movement by pneumatic actuator - cylinder driven valve stem rotation, so as to drive the ball forward and reverse rotation 90 ° to achieve.

    To open the valve (that is, the sphere diameter flange diameter on the same axis), the compressed air from the actuator of the A-side air intake, push the piston moves backward, the piston rod driven through the turn crank lever rotation, and between the lever and the valve stem cap connected to the use of square, the turn lever is rotated, following the rotation of the stem, but also led to the sphere is rotated clockwise 90 °, so that the valve in the through state, the pressure medium in the pipeline coal through the blast furnace pulverized coal injection valve. When the valve opening, as shown in Figure 2.

Figure 2 valve opening

Figure 3 valve off

    Conversely, to close the valve when the inlet from the B-side, the piston moves forward, driving the ball rotated counterclockwise 90 °, the valve is closed, as shown in Figure 3.

    While the valve is in the fully open or fully closed state, the need to adjust the pneumatic actuator positioning adjustment screws on the two, you can make the ball was fully open or fully closed.

    3.2 Ball Structure Description

    3.2.1 fixed dome structure (shaft-supported)

    To reduce the valve operating torque and enhanced reliability of sealing and avoid compression of the ball is displaced, and the outlet end of the first sealing surface wear, so the ball valve the fixed structure, its structure is shown in Figure 4, which uses The lower shaft of the ball the ball fixed (stem, the sphere and the centerline of the shaft must be on the same axis). Structure in the form of fixed ball valve comes with floating seat, or pressure in the sphere rotates, the valve seat moves, seals are pressed onto the ball, in order to ensure sealing. Usually with the ball of the upper and lower shaft with bronze sleeve bearings or self-lubricating bearings, reduce operating torque.

Figure 4 fixed ball structure

    3.2.2 sealing structure

1 sphere 2 ring 3. Seat 4.O-ring 5 disc spring 6. Adjustable pads 7. Flange

Figure 5 sealing structure

    The sealing structure of the valve shown in Figure 5. Tight seal 2 3 mounted on the seat, the seat 3 in the flange 7 4 sealed by O-rings, seals and 2 by means of disc springs 5 pre-compacted in a sphere, adjust the adjusting shim 6, I can adjust the tight sealing surface than the pressure. To the disc spring seal structure, with a sealing action with automatic compensation. The seal between the gasket and the ball except the pre-compacted by the coned disc spring to ensure sealing, the still rely DWN and seat ring outer diameter D _JH loop area formed by the pressing force of the ball on the medium to achieve the seal, seal Reliability depends largely on the average diameter of the sealing surface D _MP and the valve seat diameter D _JH ratio. If D _JH / DMP value is not large enough, the ball will not be able to ensure a reliable seal; if D _JH / D _MP value is too large, it will cause an overload sealed, leaving the valve switching torque increases, accelerated wear and tear.

http://higeroindustry.com/

What Is A Control Valve?

From  http://www.higeroindustry.com/

Process plants consist of hundreds, or even thousands, of control loops all networked together to produce a product to be offered for sale. Each of these control loops is designed to keep some important process variable such as pressure, flow, level, temperature, etc. within a required operating range to ensure the quality of the end product. Each of these loops receives and internally creates disturbances that detrimentally affect the process variable, and interaction from other loops in the network provides disturbances that influence the process variable.

To reduce the effect of these load disturbances, sensors and transmitters collect information about the process variable and its relationship to some desired set point. A controller then processes this information and decides what must be done to get the process variable back to where it should be after a load disturbance occurs. When all the measuring, comparing, and calculating are done, some type of final control element must implement the strategy selected by the controller. The most common final control element in the process control industries is the control valve. The control valve manipulates a flowing fluid, such as gas, steam, water, or chemical compounds, to compensate for the load disturbance and keep the regulated process variable as close as possible to the desired set point.

Many people who talk about control valves or valves are really referring to a control valve assembly. The control valve assembly typically consists of the valve body, the internal trim parts, an actuator to provide the motive power to operate the valve, and a variety of additional valve accessories, which can include positioners, transducers, supply pressure regulators, manual operators, snubbers, or limit switches. Whether it is called a valve, control valve or a control valve assembly is not as important as recognizing that the control valve is a critical part of the control loop. It is not accurate to say that the control valve is the most important part of the loop. It is useful to think of a control loop as an instrumentation chain. Like any other chain, the whole chain is only as good as its weakest link. It is important to ensure that the control valve is not the weakest link. Following are definitions for process control, sliding-stem control valve, rotary-shaft control

Sliding-Stem Control Valve Terminology (Part 1)

Actuator Spring: A spring, or group of springs, enclosed in the yoke or actuator casing that moves the actuator stem in a direction opposite to that created by diaphragm pressure.

Actuator Stem: The part that connects the actuator to the valve stem and transmits motion (force) from the actuator to the valve.

Actuator Stem Extension: An extension of the piston actuator stem to provide a means of transmitting piston motion to the valve positioner

Actuator Stem Force: The net force from an actuator that is available for actual positioning of the valve plug.

Angle Valve: A valve design in which one port is co-linear with the valve stem or actuator, and the other port is at a right angle to the valve stem.

Bellows Seal Bonnet: A bonnet that uses a bellows for sealing against leakage around the closure member stem

Bonnet: The portion of the valve that contains the packing box and stem seal and can guide the stem. It provides the principal opening to the body cavity for assembly of internal parts or it can be an integral part of the valve body. It can also provide for the attachment of the actuator to the valve body. Typical bonnets are bolted, threaded, welded, pressure-seals, or integral with the body. (This term is often used in referring to the bonnet and its included packing parts. More properly, this group of component parts should be called the bonnet assembly.)

Bonnet Assembly: (Commonly Bonnet, more properly Bonnet Assembly): An assembly including the part through which a valve stem moves and a means for sealing against leakage along the stem. It usually provides a means for mounting the actuator and loading the packing assembly.

Bottom Flange: A part that closes a valve body opening opposite the bonnet opening. It can include a guide bushing and/or serve to allow reversal of the valve action.

Bushing: A device that supports and/ or guides moving parts such as valve stems.

Cage: A part of a valve trim that surrounds the closure member and can provide flow characterization and/or a seating surface. It also provides stability, guiding, balance, and alignment, and facilitates assembly of other parts of the valve trim. The walls of the cage contain openings that usually determine the flow characteristic of the control valve.

Closure Member: The movable part of the valve that is positioned in the flow path to modify the rate of flow through the valve.

Closure Member Guide: That portion of a closure member that aligns its movement in either a cage, seat ring, bonnet, bottom flange, or any two of these.

Cylinder: The chamber of a piston actuator in which the piston moves

Cylinder Closure Seal: The sealing element at the connection of the piston actuator cylinder to the yoke.

Diaphragm: A flexible, pressure responsive element that transmits force to the diaphragm plate and actuator stem.

Diaphragm Actuator: A fluid powered device in which the fluid acts upon a flexible component, the diaphragm.

Diaphragm Case: A housing, consisting of top and bottom section, used for supporting a diaphragm and establishing one or two pressure chambers.

Diaphragm Plate: A plate concentric with the diaphragm for transmitting force to the actuator stem.

Direct Actuator: A diaphragm actuator in which the actuator stem extends with increasing diaphragm pressure.

Extension Bonnet: A bonnet with greater dimension between the packing box and bonnet flange for hot or cold service.

Sliding-Stem Control Valve Terminology (Part 2)

Globe Valve: A valve with a linear motion closure member, one or more ports, and a body distinguished by a globular shaped cavity around the port region. Globe valves can be further classified as: two-way single-ported; two-way double-ported; angle-style ; three-way ; unbalanced cage-guided ; and balance cage-guided.

Lower Valve Body: A half housing for internal valve parts having one flow connection. The seat ring is normally clamped between the upper valve body and the lower valve body in split valve constructions.

Offset Valve: A valve construction having inlet and outlet line connections on different planes but 180 degrees opposite each other.

Packing Box (Assembly): The part of the bonnet assembly used to seal against leakage around the closure member stem. Included in the complete packing box assembly are various combinations of some or all of the following component parts: packing, packing follower, packing nut, lantern ring, packing spring, packing flange, packing flange studs or bolts, packing flange nuts, packing ring, packing wiper ring, felt wiper ring, belleville springs, anti-extrusion ring.

Piston: A movable pressure responsive element that transmits force to the piston actuator stem

Piston Type Actuator: A fluid powered device in which the fluid acts upon a movable piston to provide motion to the actuator stem. Piston type actuators are classified as either double-acting, so that full power can be developed in either direction, or as spring-fail so that upon loss of supply power, the actuator moves the valve in the required direction of travel.

Plug: A term frequently used to refer to the closure member.

Port: The flow control orifice of a control valve.

Retaining Ring: A split ring that is used to retain a separable flange on a valve body.

Reverse Actuator: A diaphragm actuator in which the actuator stem retracts with increasing diaphragm pressure. Reverse actuators have a seal bushing installed in the upper end of the yoke to prevent leakage of the diaphragm pressure along the actuator stem.

Rubber Boot: A protective device to prevent entrance of damaging foreign material into the piston actuator seal bushing.

Seal Bushing: Top and bottom bushings that provide a means of sealing the piston actuator cylinder against leakage. Synthetic rubber O-rings are used in the bushings to seal the cylinder, the actuator stem, and the actuator stem extension.

Seat: The area of contact between the closure member and its mating surface that establishes valve shut-off.

Seat Load: The net contact force between the closure member and seat with stated static conditions. In practice, the selection of an actuator for a given control valve will be based on how much force is required to overcome static, stem, and dynamic unbalance with an allowance made for seat load.

Seat Ring: A part of the valve body assembly that provides a seating surface for the closure member and can provide part of the flow control orifice.

Separable Flange: A flange that fits over a valve body flow connection. It is generally held in place by means of a retaining ring.

Spring Adjustor: A fitting, usually threaded on the actuator stem or into the yoke, to adjust the spring compression.

Spring Seat: A plate to hold the spring in position and to provide a flat surface for the spring adjustor to contact.

Static Unbalance: The net force produced on the valve stem by the fluid pressure acting on the closure member and stem with the fluid at rest and with stated pressure conditions.

Stem Connector: The device that connects the actuator stem to the valve stem.

Trim: The internal components of a valve that modulate the flow of the controlled fluid. In a globe valve body, trim would typically include closure member, seat ring, cage, stem, and stem pin.

Trim, Soft-Seated: Valve trim with an elastomeric, plastic or other readily deformable material used either in the closure component or seat ring to provide tight shutoff with minimal actuator forces.

Upper Valve Body: A half housing for internal valve parts and having one flow connection. It usually includes a means for sealing against leakage along the stem and provides a means for mounting the actuator on the split valve body.

Valve Body: The main pressure boundary of the valve that also provides the pipe connecting ends, the fluid flow passageway, and supports the seating surfaces and the valve closure member. Among the most common valve body constructions are:

a) single-ported valve bodies having one port and one valve plug;
b) double-ported valve bodies having two ports and one valve plug;
c) two-way valve bodies having two flow connections, one inlet and one outlet;
d) three-way valve bodies having three flow connections, two of which can be inlets with one outlet (for converging or mixing flows),

or one inlet and two outlets (for diverging or diverting flows). The term valve body, or even just body, frequently is used in referring to the valve body together with its bonnet assembly and included trim parts. More properly, this group of components should be called thevalve body assembly.

Valve Body Assembly (Commonly Valve Body or Valve, more properly Valve Body Assembly): An assembly of a valve, bonnet assembly, bottom flange (if used), and trim elements. The trim includes the closure member, which opens, closes, or partially obstructs one or more ports.

Valve Plug: A term frequently interchanged with plug in reference to the closure member.

Valve Stem: In a linear motion valve, the part that connects the actuator stem with the closure member.

Yoke: The structure that rigidly connects the actuator power unit to the valve.