Control Valve Maintenance Approaches

The regular check of management valve merchandise is incredibly vital. At identical time, the upkeep is additionally undoubtedly necessary to stay the correct performance of merchandise. There are 3 basic maintenance approaches for the optimization of management valves.The first technique is that the reactive maintenance. Reactive maintenance permits refined deficiencies to travel unnoticed and untreated, just because there's no clear indication of a retardant. Even important valves could be neglected till they leak badly or fail to stroke. In some cases, feedback from production helps maintenance react before serious issues develop, however valves could be removed unnecessarily on the suspicion of malfunction. giant valves or those welded in-line will need each day or longer for removal, disassembly, inspection, and reinstallation. that's to mention, time and resources may well be wasted while not solving the matter if the symptoms are literally caused by another a part of the system.The second approach is that the predictive maintenance. Even for routine maintenance procedures on a sway valve, the upkeep person ought to even have thorough understanding of the development and operation of the valve. while not this data, the equipment may well be broken or the upkeep person may well be injured. you ought to listen to the sectional drawing of apparatus that is provided to assist in understanding the operation of the equipment and in identifying elements. Generally, in all major sorts of management valves, the actuator provides force to position a movable valve plug, ball, or disk in relation to a stationary seat ring or sealing surface. The movable half ought to respond freely to changes in actuator force. Failure to require adequate precautions before maintaining a valve might cause personal injury or equipment injury. The third one is that the preventive maintenance. It typically represents a big improvement. However, as a result of maintenance schedules are ready to get very little info on valves that are operating, several plants merely overhaul all management valves on a rotating schedule. Such programs lead to servicing some valves that require no repair or adjustment and leaving others within the system long when they need stopped operating efficiently.

Choice for Solving Control Valve Problems

Good performance of management valves may be a key to optimum method management and to overall plant performance. management valves do have issues that are traced to inadequacy of their style itself, or owing to their misapplication. Those issues may be broadly divided into 2 classes, i.e. design-selection and operations-maintenance.Valve replacement has been the standard approach to addressing valve issues within the 1st class. This generally ends up in the initial valve being inadequate for the actual service, in most cases owing to misapplication. the method of valve replacement is well understood and also the answer is effective see you later because the root reason for issues is addressed. However, when the valves are welded in line, there's substantial installation value related to engineering, scheduling, cutting and re-welding valves, and post-weld inspection. This makes the overall value of solving the initial valve downside way more than the price of the hardware itself. Retrofit may be a excellent selection for solving management valve issues. The retrofit answer may be built specifically to handle the basis reason for issues. it's a low-risk and an economic choice when properly applied, particularly in severe service applications and where giant sizes of valves are concerned. Retrofit of those valves eliminated the initial downside of below capability altogether and also the traditional carry on these valves is currently five hundredth, providing sufficient capability to reply to transients. The reliability of retrofit solutions has been proven by their application in several safety-related applications in nuclear power plants. Retrofitting is an choice that has to be thought of when solving design-selection connected valve issues. they're engineering-intensive and need expertise. When properly applied, they'll eliminate root reason for issues. additionally, they create economic sense. it's little doubt that a properly applied retrofit answer can do several advantages. there'll be lower prices. several of the parts within the installation value, like engineering, cutting pipes, welding, and pressure testing are drastically reduced or maybe eliminated. As a result, the overall value is considerably but that for a brand new valve. Besides, the danger is additionally lower. Since the interior dimensions of the body don't seem to be modified, the danger to the end-user is additionally lower. Moreover, there'll be lower downtime. Since the installation doesn't need cutting of the pipes, re-welding etc., the turnaround time for installation is quicker.

What to think about When getting a Mass Flow Controller

What to think about When getting a Mass Flow Controller A variety of industries need the monitoring of gas management. Those industries, most typically the semiconductor trade, are needed to buy equipment that's used to regulate and monitor the flow of 1 or multiple gases. people or businesses in these industries are seemingly to buy a large kind of merchandise together with a mass flow controller. With an outsized variety of mass flow management product out there there are variety of things that ought to be taken into thought before a product is purchased. one among the foremost vital things that has to be thought of is what the merchandise offers. This info will most simply be determined by researching variety of mass flow controllers. When a product is purchased or being sold it's seemingly that there'll be valuable info given the item. This info ought to be totally scan and examined to confirm that the simplest mass flow controller is purchased. When reading a product guide or an brochure, one factor that ought to be checked out is that the simplicity of the merchandise. several of the people answerable for employing a mass flow controller are seemingly to be experienced and trained within the field; but, that doesn't mean that a simple to use product mustn't be purchased. The brochure may be a good way to work out if a mass flow controller would be simple to use and operate. The speed of a mass flow controller ought to even be examined. A product package or description ought to provided detailed info on how quickly results are shown. This info is very important as a result of it'll not solely save time, however cash yet. Older models are seemingly to possess a slower response time; thus, people yearning for a faster response are inspired to appear at newer mass flow controllers. additionally to hurry and products simplicity, it's conjointly vital to grasp how dependable the merchandise is. This info could also be troublesome to work out through a product manual. to find out the dependability of a product or a manufacture people are inspired to speak to others in similar industries or use the net. this may enable you to induce positive and negative feedback through people who several have previously owned or used a selected mass flow controller. Another factor that ought to be examined before getting a mass controller is that the value of possession. When examining value} several people solely target the acquisition price, however there's additional that's included within the value of possession. it's vital to think about the price of repairs or replacements if they're required. These possession prices might be eliminated if a dependable product is purchased. it's conjointly vital to work out the quantity of power that a mass flow controller can use. Most mass flow controllers can operate on very little power, however that doesn't mean that every one can.Taking all of the higher than mentioned points into thought can facilitate to confirm that a high quality mass controller is purchased. With atiny low quantity of your time and analysis a foul purchase will be prevented.

Pressure regulator

Pressure regulator
From Wikipedia, the free encyclopedia

A pressure regulator could be a valve that automatically cuts off the flow of a liquid or gas at an explicit pressure. Regulators are used to permit high-pressure fluid offer lines or tanks to be reduced to safe and/or usable pressures for numerous applications.
Gas pressure regulators are used to control the gas pressure and don't seem to be applicable for measuring flow rates. Flowmeters, Rotometers or Mass Flow Controllers ought to be used to accurately regulate gas flow rates.

Operation

A pressure regulator's primary operate is to match the flow of gas through the regulator to the demand for gas placed upon the system. If the load flow decreases, then the regulator flow should decrease additionally. If the load flow will increase, then the regulator flow should increase so as to stay the controlled pressure from decreasing as a result of a shortage of gas within the pressure system.
A pressure regulator includes a limiting part, a loading part, and a measuring element:
The limiting part could be a variety of valve. It will be a globe valve, butterfly valve, poppet valve, or the other variety of valve that's capable of operating as a variable restriction to the flow.
The loading part applies the required force to the limiting part. It will be any range of things like a weight, a spring, a piston actuator, or a lot of commonly the diaphragm actuator together with a spring.
When the actuator is forced against an enlargement disk, the force is distributed among the pressure walls. this enables the gas to flow at the right rate and to not be regularly vaporized and diluted.
The measuring part determines when the inlet flow is equal to the outlet flow. The diaphragm is commonly used as a measuring part as a result of it may also function a mix part.
In the pictured single-stage regulator, a diaphragm is employed with a poppet valve to control pressure. As pressure within the higher chamber will increase, the diaphragm is pushed upward, inflicting the poppet to cut back flow, bringing the pressure go into reverse. By adjusting the highest screw, the downward pressure on the diaphragm will be increased, requiring a lot of pressure within the higher chamber to keep up equilibrium. during this manner, the outlet pressure of the regulator is controlled.

Mechanism of the pressure control valve

PRESSURE REGULATOR VALVES MAINTAIN DOWNSTREAM AND UPSTREAM PRESSURE

here are 2 kinds of pressure regulator valves, the one that maintain downstream pressure and therefore the alternative one that maintain upstream pressure. The pressure regulator valves typically utilized in the method application that doesn’t want an correct pressure management (fluctuation or offset up to twenty is acceptable). So, really how this pressure regulator valve operate to keep up downstream or upstream pressure?

Pressure regulator valves maintain downstream pressure
The most used pressure regulator valves are the valves that maintain its downstream pressure. This valve may be a normally open valve. Here is that the step by step operating principle of this valve.
Valve didn’t operate; the valve is on the Normally Open position.
The system begin to operate; the fluid flow comes in through the valve and engineered a pressure within the downstream of the valve.
Since the downstream pressure keep rises, it goes to push the diaphragm of the valve through the feedback line. When the diaphragm pushed out, the stem that holds the plug additionally goes up (start to close).
When the downstream pressure of the valve reaches higher than the set pressure, it pushes the diaphragm to its most enlargement and caused the plug to maneuver up and shut the valves.
Once the downstream pressure goes down, the diaphragms can|will} lesser push out therefore the plug slowly move down and therefore the valve will open.
Above mechanism (from purpose no. 2) is repeated once more and thus on.

Pressure regulator valves maintain upstream pressure
The other style of pressure regulator valve is that the one that maintain upstream pressure. The operating principle of this valve is same with the valves that maintain downstream pressure except the plug and therefore the flow in that place inversely. Here is that the step by step operating principle of this valve.
Valve didn’t operate; the valve is on the Normally shut position.
The system begin to operate; the fluid flow didn’t have the valve (Normally shut valve) and engineered an upstream pressure of the valve.
Since the upstream pressure keep rises, it goes to push the diaphragm of the valve through the feedback line.
When the upstream pressure of the valve reaches higher than the set pressure, it pushes the diaphragm to its most enlargement and caused the plug to maneuver up and open the valves.
Once the upstream pressure goes down, the diaphragm will lesser push out therefore the plug slowly move down and shut the valve.
Above mechanism (from purpose no. 2) is repeated once more and thus on.

Two-Way Valve (Control valve System)

Two-Way Valve

Parker Brass Two-Way Ball Valve with PCTFE Seat, 1/4" NPT Female

Principles of Two-Way, Three-Way Valve.
The entrance and exit one way in which a valve to control the flow or not flow. Or flow in small amounts. Actuator The system is based on the increasing and decreasing pressure.

The valves are dim. Or open the flow of water. As required by Aqua. The temperature itself.

In a Two-Way will notice that. Power cycled near Pump it must carry a lot of pressure. Thus, the selection of Two-Way must take into account the Close Off Pressure by

Therefore, when using Two-Way is often used in conjunction with other automated systems such as BAS, CHILLER MANAGER order to be able to use the device in the system.

Three-Way Valve

Moeller Fuel Tank Three-Way Valve (3/8", Brass)

Principles of Three-Way Valve.

3 Way Mixing Valve with inlet 2 and the combined solution is one of the 3 Way Mixing Valve for use in the Process of production may be working in the water with a temperature difference between two points, to mix or Mix out to be. temperature output as required. However, as we used in the HVAC 3 Way Mixing Valve does not mix the water from the second point, but the Mixing Valve The water from the Line Supply will be split into two and the one to be passed to the Coil to cool in the volume. more or less according to the Actuator is then forwarded to the inlet valve of the A section, the remaining water is sent to the inlet valve to the B to collect the 3 Way Valve passed to Return Line to PORT C. 3 Way Mixing Valve is installed in the HVAC system to be installed on the Return.

Because of that task. As a result, this system does not have a change of Pressure The need for automatic control device to save power too much. 

Control Circuit

Advantages of 2 Way Valve is a valve is cheap. The installation was. I have to just 2 points.
Disadvantages of 2 Way Valve is opened or closed. Or even to dim the flow rate will affect the Unit Valve side always.
The disadvantage is that it is the Close Off Pressure, which is the value that represents the ability to block, the water flow from the exit to close that can block Pressure between the two sides up to a couple of Psi in the case. Proportional 2 Way Valve Control Valve Authority be given to the poor.


The advantages of 3 Way Valve is a high balance. Because the water that each Unit will have a constant flow rate. Only the internal management of the Unit will allow water to flow into the Coil.
More or less depending on the system 3 Way Valve and Actuator with 3 Way Valve Flowrate in a system that is unable to do more systems.
So much energy. And would require additional equipment and piping in the Line By Pass.

12v DC 4mm 1/4" Normally Closed Stainless Steel Viton 2-Way Solenoid Valve

Prince LS-3010-2 Directional Control Valve, Logsplitter, 2 Ways, Spring Center to Neutral, Cast Iron, 2750 psi, Lever Handle, 25 gpm, In/Out: 3/4 NPTF, Work: 3/4 NPTF

110 VAC Normally Closed 2-Way Solenoid Valve 3/8" NPT Brass Body NBR Seals

Parker Brass Two-Way Ball Valve with PCTFE Seat, 1/8" NPT Female

Industrial Grade 1PZA1 Three Way Ball Valve, 1/2 In NPT, Brass

1/2" 3 Way S.S. Ball Valves W/ Mounting Pad - L Port ISO 9001, NPT Threaded

Iwata Airbrush Accessories - 3-Way Valve Assembly

Control Value (Control valve)

Basic Introduction.
                In many industrial manufacturing processes. The process is often large and complex automated control system was used for the production of a continuous bloom. Performs well. Important one in the system that not only is a device driver or the final drive, which will be discussed in this case, control valve, which is one of many in the group's final drive, because the control valve is a device that is very important. One of the production system. Also known as a top priority there.
Education for understanding will lead to safer use of the system. And practitioners. As well as the production process more efficient and effective as desired. The problem with that fits the era when the power is often scarce and more every day.
Before going into the contents of the Control valve should know and understand the basics about Process Control Terminology in order to be able to understand the next section as well. It said in a brief summary. And goes into detail in the next section again. This case is very similar to the study of mathematics to understand fully before it can be defined in part by an interruption to a minimum.
It is recommended to keep reading until the end, you will be most useful.
Note: final drive = final control element = final element.
1. Process Control Terminology.
1.1 Capacity is the Flow Rate of flow of fluid through the Control Value under certain conditions.
1.2 Controller is a device that acts in the process. By accepting or Input variables to control the variables measured (Controlled Variable or Measured Variable), then processed as a control (Control Regulatory) and then send the Output Signal (The outcome of the process. effect) to the Final Control Element in the Control Value.
1.3 Closed Loop Control of a closed control circuit. The present value of the Status of Final Control Element back compared to the Set Point to determine the status of the target (Set Point) is also a Error or SP-PV of the Controller, it is ordered. Continue until the status of the Final Element required by the Controller Error as it will stop sometimes to the Closed Loop Control Loop the Loop called the special attention that we want to control.
1.4 Control Range is the range of motion of the Stem Value or range of motion of the stem valve sometimes called the valve travel or rated travel.
1.5 Dead Band or Dead Zone.
                    The sensor or control valve does not respond to the changes (input. The BOT conversion) as a result of the nature of the device itself. Occur in both instrument and control valve, but most will apply to each instrument and control system.
                From below, described as follows.
Assume that this system is a function of the air compressor has a set point to start at 7.5 bar, stop at 8.0 bar.
At the start air compressor to compress the air to generate pressures up to 8 bar of pressure switch to tailor the air comp. But because the time lag was found to occur over shoot up a little later on. pressure in the system gradually decreases until it reaches 7.5 bar, where the compressor to start up, but because the pressure switch to use a dead band is quite large (equipment, low quality), making it impossible to respond to the input variable and air compressor will not work as intended because the switch does not change the status. Decreasing the pressure to 7.0bar of the air compressor to start up the dead band can be seen that this happens, we can not control the system as needed.
How is the pressure switch with low dead band to use or install a pressure switch 2 is made to start, stop independently of each other.

dead band of instrument.

The documents for the course introduction to process control training plan. Electricity Generating Authority of Thailand

1.6 Gain is the Output Change / Input Change has 2 types of Static Gain is the OP Change / IP Change during Steady State, sometimes called the Sensitivity of Dynamic Gain an OP Change / IP Change in conditions where the change occurs. as a Function of Input frequency or rate of change in this value is also equipped with a means to extend the input signal is enough. For example, the power amplifier.

1.7 Hysteresis as a result of reversing the dead band is not. A unique feature of the device (instrument), most of the material and the identification feature of the device can not be solved.Imagine a line drawn on paper from left to right. Then drag it back by trying to replace the old line that is not possible. This means that any movement in the world that happens, it can not reverse it completely. According to Rule 2 of the thermodynamics.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.

1.8 Open Loop Control is an open circuit. Without bringing the status of Final Control Element back compared to the Set Point to determine if there is Error or SP-PV occurred such as opening a floodgate is ordered to open the door motor is running. until the end. By monitoring the position of the door where there is no sensor that detects movement in various positions there.

        Working in this manner is not commonly used in automatic and very rarely found in automatic process control.

1.9 Process Variable, including pressure, temperature, flow rate, level, conductivity, p H, vibration etc.

1.10 Process or processing and oil refining process. Production of electricity. The cooling process.

1.11 Relay is a device that acts similar to the Power Amplifier is to amplify the air (pneumatic. signal) to a larger drive for Value Actuator word in this sense is used with a control valve.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.
1.12 Resolution is the resolution of the Display device or the display. Can be expressed in value. This means that with only minor changes. It can be shown that as pressure gauge for pressure measurement with a scale model should assume that a channel of the scale is equal to 0.5 psi, it means that if the pressure changes of less than 0.5 psi, it can not. read correctly. It can be about value. The digital display is a set of numbers such as 2 is x.xx If the change is at 0.00x, it can not display it to appear. The meter will not recognize the change at all. Unlike analog or analog to estimate the change is simply not correct it.

1.13 Response Time or as often referred to as Time Constant.
The time response of the process to change the value of the Sensor input. The Response Time is typically measured in terms of the Time Constant is a value.
             Time Constant Output refers to the value of which changes with time depending on the input and ideas from the Output to Output 63.2% of all the changes.

Response from a graph of the temperature. Normal temperature is 100 oF if the temperature was suddenly changed to a Step Change to 700 oF the response of the device will be gradually increased to 63.2% of the 600 oF (700-100).
                From the graph it is seen that the results of the measurements of the Sensor and pointed to the 63.2% or 479.2 oF (600 * 63.2%), it takes 3 seconds, that is, 1 Time Constant is therefore concluded that 1 time constant is. equal to 3 seconds.
 The other is calculated as follows: Time Constant.
                2 Time Constant (6 seconds).
                     700 o F - 479.2 o F = 220.8 o F.
                     (220.8oF x 0.632) + 479.2 oF = 618.7 oF.
             3 Time Constant (9 seconds).
                 700 oF - 618.7 oF = 81.3 oF.
                (81.3 oF * 0.632) + 618.7 oF = 670.5 oF.
1.14 Shaft Wind-Up is the nature of the movement (rotation) of the strength of the Actuator Shaft on the bottom directly to the rotation. But the end is connected to the Value Plug the motion due to friction and Actuator Seal or packing far more torque to overcome friction until Value Plug the move. This only happens with Rotary Value.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.
1.15 Sensor and Transmitter.
Sensor is a device parameter (Measured Variable) include a temperature sensor, pressure sensor, level sensor and so on.
Transmitter is a device which is used to change the values ​​of the variables measured (Measured Variable) is to get value from the sensor it can then convert to a standard signal (standard signal) make it easier to use with other devices that are manufactured under common standard temperature transmitter, level transmitter Tx and a symbol of transmitter.
Transmitter functions are as follows.
Ø Converse change variables to measure the desired change, such as flow rate and differential pressure.
Ø Amplifier serves to amplify the signal changed to a larger size. To make it easier to transport and to reduce the problem of signal loss or noise interference.
Ø Standard signal of the amplifier must be expanded in scale.
     4-20 mA, 1-5 V, 3-15 psi.
Ø Transmit a signal to the standard. The measured signals can be exported in various formats as follows.
- Electrical Signals into an electrical signal in the form of electricity. Or voltage (4-20 mA, 1-5 V).
- Pneumatic Signals are signs of pressure (3-15 psi).
- Hydraulic Signals is a sign of fluid pressure (3-15 psi).
- Telemetered Signals in the form of radio frequency signals.
1.16 Transducer is an electrical device for the measurement of Sensor and then sends an electrical signal to the control room. The transmitted signal will not be in the form of Standard Signal Transmitter, such as Vibration Transducer, which may be -5 to +5 V or 1 to 10 V was.

1.17 Value Sizing is a small selection of other components of Value types are associated with the system to work properly.
1.18 Set Point is the goal of control, such as Steam Temp. Set Point = 560oC and the control variables we measured, that is, Measured Variable Controlled Variable and generally will be the same. The temperature of the water and Measure Variable Controlled Variable temperature.
In some cases, control the water level in the tank Controlled Variable is the water level in the Measured Variable can be measured in terms of pressure or pressure difference can then convert the pressure into the water or the Flow Rate. is the Measured Variable Differential Pressure.
1.19 Bench Set is a test of the movement of Actuator Spring Range by the wind into the Diaphragm Chamber for Actuator a move that is not connected to the Value Plug a test of the diaphragm that works according to its pressure. scheduled or not. This is a preliminary indication that the diaphragm has a problem like a leak or a tear or other defect to be corrected before there is a problem in actual use.
1.20 Diaphragm Pressure Span is the difference between maximum and minimum values, such as Diaphragm Pressure Range 40 to 400 kPa at the Span is 400 - 40 = 360 kPa.
1.21 Single Acting Actuator is an input of energy Actuator (Pneumatic, Hydraulic) in one direction will cause the spring to move in a direction opposite to the force of the pneumatic or hydraulic.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.
1.22 Double Acting Actuator is to have the input of energy Actuator (Pneumatic, Hydraulic) in the second direction is not spring. Movement in both directions must use the force of Pneumatic or Hydraulic) or the need for external power in both directions.
1.23 Dynamic Unbalance is the presence of the load. One caused by the fluid force acting on the Value Plug in an open Value.

The technical documents, training of Control Valve, Pisanu course Mr. Brown doing the Navy F: I, Division of Training Equipment, Training Department, Electricity Generating Authority of Thailand.
1.24 Fail Closed as the conditions that apply to certain systems where security is a major concern. When no power source (Pneumatic, Hydraulic) Value will be placed in the closed position. Usually closed by spring force.
1.25 Fail Open Fail Closed, but Value is the same as when the Power Source Fail.
1.26 Fail Safe is to determine the position of the Value that will be placed in any position on the Power Source Fail is perhaps the open end (fully open) closed with (fully closed) or open the original (lock up), depending on. Control Regulatory controls or conditions with regard to the safety of the system as a safety valve should be fail safe, it is fully open.
1.27 Flow Characteristic is the relationship between Flow Rate through the Open Value and Percent of Value in mind that there are two general types of 0-100%.
- Inherent Flow Characteristic.
- Installed Flow Characteristic.

- Inherent Flow Characteristic. Is the relationship of the Flow Rate to Value with the movement of Stem Travel, or%, to close the opening of the Value of the closed end to the Rated Flow with a Pressure Drop for drop box service valve at one value (Constant DP Across. Value).

- Installed Flow Characteristic. Is the relationship of the Value Flow Rate to Stem Travel or% off of the Value of the closed end to the Rated Flow with a Pressure Drop for drop box service valve is changed in accordance with the flow and condition of the Process. this value is the actual time used.

1.28 Flow coefficient (Cv) is a constant that depends on the geometrical shape of the object, the fluid flow. This is the Flow Capacity to the Cv is determined at 60oF, Pressure Drop 1 psi Measured Flow Rate of Water-US Gallon / Minute Flow Value for Cv are the specific Value, or a device such as Cv. Orifice plate or the Control Value table Cv Cv values ​​to be computed at a flow rate.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.

1.29 Normally Closed Value is defined as the Fail Closed.

1.30 Normally Open Value is defined as the Fail Open.

1.31 Push Down to Close Construction of Value Actuator is Direct Actuator (direct acting) is when there is pressure at the Diaphragm Chamber will make Value Stem cell into the Value disable this behavior as a Value over, such as Value faucet. rotate the hand lever valve is rotated to move the valve to close.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.

Push Down to Open Construction of Value Actuator Direct Actuator is a part of the Reverse Value Plug it into a pressure inwards on the Diaphragm Chamber will move to the Value Value Stem to Fluid flow through.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.

1.32 Rangeability is the Maximum Range / Minimum Range for 100 / 1 means that the Control Value is the ability to control the flow well even Flow Rate up to 100 times that of the Minimum Controllable Flow Rate is normally controlled Flow Rate 1. m3/hr to 100 m3/hr, but may be used by the Capacity, Pressure Drop Performance remains the same, or, most often used with the Rangeability Instrumentation and Instrument or device is called a squeeze - to span the pressure. transmitter with a rangeability 50 / 1 means that one can calibrate the measurement range 0 -1 bar or 0 - 50 bar or in the case of a compressed span of the error or accuracy, they also must consider that. in a neighborhood that is acceptable or not.

1.33 Rated Flow Coefficient Cv is located in the Value Rated Flow Rate.

1.34 Rated Travel Travel is the movement from the closed position to a position or positions on the highest Rated Full Open Flow Rate requirements.

1.35 Seat Leakage of the leak of Fluid through Value when in the closed position in the state of Temperature and Differential Pressure required in practice is not able to make the valve blocking the flow of 100% will have leakage values ​​that are in charge. acceptable to the table.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.

1.36 Vena Contracta the position of the Maximum Fluid Velocity and Minimum Pressure.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.

1.37 Calibration Curve for the Relationship between Input and Output data.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.

1.38 Calibration Cycle.

Is to record the relationship of the Input and Output from 0 to 100% and from 0% to 100 back to the basics for the analysis of problems in the future. Such as checking the drift occurs.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.

1.39 Hunting is the state of the Oscillation of the control signal to the Final Element can not get to the Set Point in the Control Value Most of Control Signal from the Positioner, which is not stable (unstable signal) can not control the PV was based. they need. These symptoms may be caused by interference. Radio transmission time. Or from devices that generate high-power radio service. This will make the stem valve may be moved at any time. In order to run toward the set point, but it can not be approached. It was moving back and forth all the time. This results in a direct bearing on the mechanical equipment, including packing, positioner mechanism, actuator, etc., that will wear faster than normal as well as the process deviation is the deviation of the production or quality of products as was the case with fuel oil. flow control valve or valves to control flow rate of fuel used in combustion. It makes the combustion temperature is not constant. If steam is produced, it will be the pressure and temperature of the steam has not been affecting the functioning of the device makes the system more difficult as a result.

1.40 Instrument Pressure Output Pressure of the Controller (I / P) to the order of the Action to Control Value.

Show the location of the instrument pressure.

The Control valve handbook, 3rd edition, FISHER Controls international LLC, USA.

1.41 Loading Pressure is the pressure of the Pneumatic Actuator works if no I / P converter for Instrument Pressure Loading Pressure can be used instead.

1.42 Operating Media is a Fluid Flow Rate controlled by the Control Value Max. Flow Rate 100 m3/hr at 100.

1.43 Range is the range of measurement applications or areas such as 3 to 15 psi, -40 oC to 100 oC and so on.

1.44 Span Range is the range of 3 to 15 psi as the Span is 15-3 = 12 psi and so on.

1.45 Repeatibility. The ability of the Instrument, which can be measured the same value or close to the original value under any condition was based on the measurement method, the measurements, the device used to measure (quality), the location of the temple, Condition. (such as temperature, pressure, etc.) is usually measured in a short time he tells the Standard Deviation is a measure of the pressure of the water temperature is 80 oC, Flow Rate 50 m3/hr assumed that the P value was equal to 10.0. later time T, and the bar Flow Rate changes until it returns to 80 oC and 50 m3/hr 10.0 bar P value should be measured by the same means that every time you go through the Process to the measured value. With time, it should be the same.

The Control valve handbook, 3rd edition, FISHER Controls international LLC, USA.

     Not a measure of P = 10.0 bar.

      The second measure is P = 11.5 bar.

      The third measure P = 9.0 bar.

The conditions were at that time (the measurement) is the same as the temperature is 80 oC, Flow Rate 50 m3/hr and is called there. Repeatibility bad.

The Repeatibility. On the other hand, is meaningful. The ability of the Instrument to Measure and Output out by the Input entry is maintained under Operating Condition was in a short time during one such Multimeter Measurement Voltage supply voltage (Ideal Power Supply) is required. measured under the conditions of the original value was measured as 10.0 VDC for 10 times, etc. In a short time.

1.46 Reproducibility. Instrument is capable of measuring the value and the value of Input Output was originally entered. Under Operating Condition, but time is a measurement in the range 1 month 3 months or 1 year, this measure was 100 bar for 3 months, it should be measured at 100 bar with the Operating Condition the Instrument to be. Reproducibility is good too.

1.47 Drift has a similar meaning. Reproducibility. Or may be called as the same words that should not cause any Instrument Drift in a short period of time or for a few months, the Drift has two types.

- Point Drift by the original Operating Condition of the Output is measured as much by the change from the original value at the Input Signal.

- Calibration Drift is the introduction of the new Calibrate Instrument was made by comparing the results obtained with the Calibration Report or Calibration Curve was that there was much difference in any of the Calibrate settings such as

The first was to calibrate.

Input (%).

Output (volt).

0.0.

5.0.

25.0.

10.0.

50.0.

15.0.

75.0.

20.0.

100.0.

25.0.

The new value through the use of a 1-year ago.

Input (%).

Output (volt).

0.0.

4.5.

25.0.

10.4.

50.0.

14.5.

75.0.

19.5.

100.0.

24.3.

Drift of the sample that have occurred about 0.5 in every instance by the Drift of the device to tell the figures are the% Output Span drift = 0.5x100 / 20 = 2.5% of output span.

1.48 Static Error Error is measured at the same conditions. But the difference is negligible.

1.49 True Value (the value that is true, true).

              True Value = Instrument Readout (reading from a meter) - Static Error.

1.50 Sensitivity is the ratio between the Change of Output / Change of Input under Steady State Condition.

1.51 Dynamic Characteristic occurrence of three types.

- Step Change Input changes immediately.

- Linear Change Input value changes in a gradual increase or decrease, also known as the ramp signal.

- Sinusoidal Input value changes in a Sine Wave.

Change the nature of these causes Dynamic Error, Lag, Speed ​​of Response, Fidelity, Etc.

1.52 Dynamic Error Error is caused by the condition of the Dynamic Characteristic and 3.

1.53 Lag or time lag when the input changes the nature of the device. Will not be able to respond immediately to the Time Lag is always

1.54 Speed ​​of Response is the ability of the Instrument in response to changes in the Input Speed ​​is an extremely good that can detect very early changes in the Input.

1.55 Precision Error Error is from the Conformity of a measuring device such as R = 1.592 Mega Ohm Resistor with Error 154 Ohm Multimeter is used to measure and read by anyone. (Assuming that there is no Error that reads values), the value of boost pressure. Read it at about 1.5 Mega Ohm with the actual value is at 1.592 +154 Mega Ohm reading of Scale, called the Precision Error Error is caused by the limits of the measuring Scale Reading.

1.56 Zero Error of Measurement Error in a lower range Input is configured as a% Of Ideal Span.

1.57 Zero Offset is defined as normal, with no Input Indicator Instrument is to be displayed at the center. If the reading is not zero, that is the Zero Offset to adjust or Calibrate the Indicator shows a value center, and to save them if the Zero does not really illustrate clearly the case of the Pressure. Gauge is placed in a normal atmosphere. Pointer Indicator pointer value, or should the value "0".

Mechanical Hystersis 1.58 Backlash is the most happening with Gear, Linkage, Mechanical Transmission Device as well as figure out the gear. When rotated clockwise. The position of the gear position to another. However, when rotated counter-clockwise. Position of the gear transmission is not in its original position. Backlash is a little change should be minimal. However, this does not eliminate it. Due to the limitations of the mechanical parts that need to be involved Clearance. The device is a mechanism or a Non-Rigid Mechanism.

2. Introduction to Control Value.

                 The control system is a device that serves to drive the Final Element of the control signals from the Controller and served in the refinement or Manipulated Variable Process below.

Final Element or final control element is composed of many types of equipment.

- Control Value (Pneumatic / Hydraulic).

- Motor Operated Value.

- Pneumatic / Hydraulic Damper.

- Pump (Metering Pump).

- Pneumatic / Hydraulic Cylinder.

- Shut off Value (pneumatic / Hydraulic).

- Linear Drive Actuator.

- Other Mechanical Devices.

It can be seen that the control valve is part of the final element is an important and best in the world.

2.1 of the Control Value.

Final Element Control Value is one of the main functions is important. Control the rate of fluid flow (fluid flow control) is discussed in a Control System that serves to adjust the Manipulated Variable to get the value of Set Point by checking with the Instrument that monitors a variable or Measured Variable (. Controlled Variable) or PV and then send a signal to the Controller to compare values ​​with the Set Point (SP) If the value of Offset or Error (SP-PV) occurs in the Controller, it will add to the Control Value to adjust. Process until the desired value or Error = 0 to end processes.

2.2 Types of Control Value.

By following the motion of the Drive Shaft.

A. Linear Shaft Value or Sliding Stem Valve Drive Shaft is a movement in a straight line as shown.

The Control valve handbook, third edition, FISHER Controls international LLC, USA.

A great feature. And a Non-Return Valve (Check valve)

Considerations in choosing a valve to return.
Material (material).
           The valves are to be used for a variety of common tasks. To the water. That must withstand high pressure natural gas applications. The high corrosion resistance and chemical And to withstand heat and high pressure steam, etc., so the materials used to make the valve must be selected to suit the material (medium) in the pipeline.

           Of the PTT. The Check Valve Material used in natural gas should be a standard reference Cast Steel or Forged Steel ASTM A 216 Grade WCB standards ASTMA 105 Grade 2.

           In addition, each type of material to withstand the pressure and temperature. (Pressure / temperature rating) are different, which is known to be resistant to a variety of materials with different materials, a Stress. When adding more pressure. Will withstand temperatures down. Or it can withstand higher temperatures when the pressure decreases. We need to bring the pressure and temperature were compared with actual use. pressure / temperature rating of the valves of each type of material so that the material can withstand the pressure and temperature conditions of use.

           Major components of the valve is reversed and the renewal of the valve spring and the spring is a good idea I can not Stress fracture Life cycle has a high resistance to corrosion. And the pressure in the open or under a Range of Pressure drop of the spring stiffness to suit a wide range of applications. The material is Stainless steel springs in general, but if you use a high temperature over 300 should be a spring made from Inconel.

           For selecting the material of the Seal, which determines the rate of leakage (Leakage rate) of the valve is to be divided primarily into two categories: Metal to metal seal and Soft seal by Soft seal the Leakage rate is better than Metal. Zero leakage to metal seal, or a material that is Soft seal must be selected to suit the material. Pressure and temperature inside the pipe. The materials used in the Seal Check Valve is widely used in the work.

           Natural gas and BUNA-N or Nitrile Rubber, synthetic rubber, which is caused by the mixture. acrylonitrile (ACN) with Butadiene leak rate testing (Leakage rate) of the valve and return valve between the product manufacturer to do it. There are several standard benchmark tests, depending on each manufacturer to choose from. The popular standard is the European standard (EN), German Standard (DIN) and American standards (API).

Pressure drop (Pressure drop).
           In the design of piping systems as well. Pressure drop across the pipe should not be more than 0.3 bar, the pipe length 100 meters, Pressure drop caused by friction of the surface of the pipe itself. Pipes, valves and fittings installed at all. Therefore, the valve is back to keep the pressure should not exceed 0.1 bar Pressure drop across the valve, or one of them.


Valves are to be classified into three main types.

1. Valve and back pressure drop across the valve between DISCO and DISCO to be most valuable when compared with the other two types because DISCO has obstructed the flow than others. Thus, it often does not produce an 8-inch valves of this type because it is too high Pressure drop Pressure drop through the valve will be different depending on the stiffness of the spring as well.

2. Valves and back pressure drop across the valve, Swing and Swing back to DISCO is lower than the valve is open and unobstructed flow of less than The opening angle is about 600 -700 but also Pressure drop than the Dual plate.

3. Valves Dual plate similar to a pressure drop across the valve and back Dual plate to a minimum. The valve opening and flow, very little obstacles. The opening angle of about 800 each.

Valve to return to the good quality.

           - Pressure drop is constant and appropriate to the system.

           - Sealed (Tightness of the valve) or Leakage rate is low.

           - Lifetime of the spring (Spring life time) life does not crack.

           - Requires a minimum flow rate (Min flow), to avoid problems Clattering.

           The installation of Check Valve.

           In the case of a Check Valve to prevent back pressure to the gas station. Turbine meter must be installed from a 5D (5 times the pipe diameter) standard AGA7.

           Clattering is a phenomenon that the valve has a flow rate or pressure is not enough to cause the valve to the open position or the position is stable. Often resulting in a short time. At startup or stop the system. The valve will open - the frequency and causes wear and tear. If the valve has been selected the wrong size or type Clattering the time of normal use. The valve due to wear and short-lived than it should be.

           The size of the valve to return (Size) is the size of the valve to return often overlooked by those who use it. Because the majority of the selected pipe size alone. The installation is convenient, but if we take into account the pressure drop across the valve should not exceed 0.1 bar, and to avoid instability problems, the valve opens. Clattering known that the short lifetime of the valve. Selecting a pipe, valve size alone is not sufficient to check the pressure drop and Clattering with

Check Valves- Pair