TILI Automation

 SAMA is an acronym of Scientific Apparatus Makers Association, in some plants, there has been greater adoption of SAMA diagrams which provide more detailed process diagrams which constitute various process symbols. SAMA drawings are sometimes referred to as “control functional diagrams”. SAMA symbols are rarely used on P&IDs. Rather, they are generally used to diagram control systems at a detailed functional level. They provide no information about the device’s location or function, nor about the technology used to implement it. SAMA Diagram Usually, SAMA symbols show the control system without reference to the processing equipment or piping details. Still, for complex control systems, because they can show greater functionality compared with other documentation formats, they are often preferred for presenting control strategy details in some industries. Because of the complexity of their control strategies, SAMA symbols are extensively used in the power generation industry. S...

 Standard control valves can handle a wide range of control applications. The range of standard applications can be defined as being encompassed by atmospheric pressure and 6000 psig (414 bar), 150F (65C), and 450F (232C), flow coefficient Cv values of 1.0 and 25000, and the limits imposed by common industrial standards. Certainly, corrosiveness and viscosity of the fluid, leakage rates, and many other factors demand consideration even for standard applications. Perhaps the need for careful consideration of valve selection becomes more critical for applications outside the standard limits mentioned above. Here we are going to discuss some special applications and control valve modifications useful in controlling them, designs and materials for severe service, and test requirements useful for control valves used in nuclear power plant service. High Capacity Control Valves Generally, globe-style valves larger than 12-inch, ball valves over 24-inch, and high-performance butterfly valv...

 Cavitation is an applied science that has not evolved to the highly refined level that supporting the more traditional control valve sizing calculations. However, there is a great need by users and manufacturers alike for practical information in this area. Cavitation Definition The definition of cavitation is given as a two-stage process associated with the flow of liquids. The first stage involves the formation of vapour cavities or bubbles in the flow stream as a result of the local static pressure in the flow stream dropping below the liquid vapour pressure. The second stage of the process is the subsequent collapse or implosion of the vapour cavities back to the liquid state when the local static pressure again becomes greater than the fluid vapour pressure. Cavitation is a phenomenon that can accompany the flow of liquids through control valves. Failure to account for cavitation can result in potentially costly performance problems. To prevent this situation, it is important...

 The flow test system shall be as shown in following figure. It includes: a) a test specimen; b) a test section; c) upstream and downstream throttling valves; d) a flow measurement device; e) pressure taps and measuring devices (upstream and downstream); f) a temperature sensor; and g) cavitation detection instrumentation shown in figure. Cavitation Test Procedure Step 1: The test specimen can be any valve or test apparatus for which test data are required. Step 2: The test specimen upstream and downstream piping shall conform to the nominal size of the test specimen connection and to the following length requirements. The upstream pressure tap shall be two nominal pipe diameters from the test specimen connection, while the downstream pressure tap shall be six nominal pipe diameters from the test specimen connection. There shall be at least 18 nominal pipe diameters of straight pipe (eight if straightening vanes are used) upstream of the upstream pressure tap, and at least one pipe...

 The SMART transmitter stands for Single Modular Auto-ranging Remote Transducer. It is an intelligent transmitter that has an analog output and simultaneously provides digital communication signal based on HART protocol or FOUNDATION FIELDBUS or PROFIBUS. Table of contents SMART Transmitter Advantages of SMART Transmitters Disadvantages of SMART Transmitters In general, the simplified smart transmitter diagram shown in the below figure. It consists of a sensor or input circuitry, the microprocessor, memory, and a communication block. The word multi-variable transmitter is also used sometimes particularly for a device like a smart flow measuring instrument. This measures absolute pressure, differential pressure, and process temperature. Computes mass flow rate and volumetric flow rate of the process fluid. SMART Transmitter The output from the smart transmitter no longer just the primary process variable, but also includes secondary process variables, sensor health, sensor performan...

 What is Control Valve? Control valves are used to automatically/manually regulate process variables (pressure (Pressure, Flow, Level, Temperature, etc.) in the process area. They are available in various classes as per requirement from PN16 to 1000. The Control Valve is the Final control element that is responsible for controlling the process parameters. Symbol of Control Valve Control Valve Consists of the following elements: 1. Actuator 2. Positioner 3. Valve Body Actuator: The Actuator is the Upper Portion of the Cylinder, which allows the diaphragm to move the valve steam upward and downward. Positioner: The Positioner is nothing but an advanced I to P converter, which converts the 4-20mA signal to Pneumatic 3-15Psi, and allows the stem of the actuator for the movement to and fro. Valve Body: Valve body manufacturing depends on the temperature and pressure in the line. The material of the valve body may be Forged carbon, SS316, SS314, Casting, etc. Master Equipment: Universal ...

 Here we shall learn about Pressure Relief Valve basic terminology and types of PRV used in industrial process control. Pressure Relief Valve

 Since precision pneumatic instruments operate best when their supply air pressure is at a constant pressure, it is necessary to regulate the fluctuating air pressure from the receiver vessel down to a lower, more constant level for the instrument. The device designed to do this is called an air pressure regulator. Air Pressure Regulator A cut-away diagram of an air pressure regulator is shown here: The wedge-shaped plug can move down to open the passageway and allow more of the high-pressure air to enter the chamber below the diaphragm, and can move up to close off the passageway and reduce the flow of incoming air into the diaphragm chamber. The regulation setpoint is adjustable by the position of the threaded rod pressing down on the diaphragm through a spring. Describe how this air pressure regulator functions. Suppose that the outlet air pressure is below setpoint. How does this mechanism respond to bring the outlet pressure back up to where it is supposed to be? If the outlet...

 Here we shall see recommended practices for selection of the control valve for harsh process conditions. Control Valve Recommended Practices   The process design conditions should be as per the ANSI pressure rating and the material of the valve should be selected as per piping specifications for a particular project. The valve end connections and pressure rating should, as a minimum, conform to the piping specification. The valve material shall be suitable for the process conditions. Nickel alloy or stainless steel valve metallurgy should be specified for temperatures below -20 degrees F. High-pressure steam, flashing water applications, and boiler feed water service where differential pressures exceed 200 psi may require harder chrome-molybdenum alloys. Sour service valve materials must meet the requirements of NACE MR0175-90. Corrosive and erosive components even in trace quantities may affect the metallurgical choice of the valve. Trim material can be as per manufacturer s...

 Control Valve Noise The predicted sound pressure level radiated from a control valve is a complex determination, and the allowable noise level in the installed location cannot be stated as one simple number to be specified in all circumstances. This is particularly true where there are other noise sources in close proximity since they have an additive effect. The actual level depends on a number of factors, such as atmospheric discharge, physical location, the proximity of other noise sources and their magnitude, piping system configuration and wall thickness, insulation on piping, presence of reflective sources, etc. Prediction of noise generated by a control valve is an inexact science. Prediction levels for a valve operation at conditions specified on the specification sheet can vary widely using various manufacturers’ methods. To provide a basis for allowable noise level analysis, control valves calculated to generate excessive noise levels should have alternate valves propose...

 There has been so much research going on for controlling the noise generated by control valves but before that one must understand how this noise is generated in the valve. Still, very limited ways are available to control the valve noise. The control valve noise problem may involve any or all of the source-path-receiver elements. Among them, source and path treatment is widely used for valve noise reduction and we will discuss them. Direct Approach (Source Treatment) Reduction of the acoustic energy at the source is the most desirable approach and widely used. Generally, low noise valves or low noise cage trim valves as shown in the below figure consist of multiple small orificial elements. Most quiet valve uses the concept of distributing the acoustic energy into smaller flow paths. The reduction of acoustic energy is accomplished by minimizing the effect of the shock wave and its strength. Redistribution involves shifting of acoustic energy into a high-frequency range. Because ...

 The control valves flow direction based on different factors like delta pressure, cavitation, failure action, and percentage of control valve opening. Control Valve Flow Direction Types of control valve flow direction Flow to Open (FTO) Flow to Close (FTC) Flow to Close (FTC) When the fluid passes on top of the plug, it gives a closing action to the plug. This is called the flow to close (FTC) type flow direction. The effects of cavitation are less and it requires more breakaway torque to open and less torque for closing the valve. This is mainly used for low-pressure applications. Flow to close FTC) is used in anti-cavitation trim with rotary valves are the special applications. Flow to Open (FTO) When the fluid flows pass through and faces the plug directly, it gives an opening act to the plug. This is called a flow to open (FTO) type of flow direction. As the flow is upward direction on the plug, it requires higher closing torque and less opening torque and is mainly used for h...

 Pneumatic piping employed in plants is used to convey air for two basic reasons: (1) that of supplying Energy for the operation of instruments and other devices, and (2) that of transmission of Information between instruments. Integrity of the piping system is essential to avoid loss of the pneumatic supply and degradation of the transmitted signals. Supply air is usually delivered to the control center from external sources at pressures typically between 60 and 150 psi gage (400–1000 kPa). It should be clean, dry, and suitable for the application and environment. A sufficient flow of supply air should be available to meet the control center requirements for transient as well as steady state conditions. Displacement of oxygen in the control center or control room, resulting from the use of bleed type instruments when gases other than air are used, should be considered. Pressure Reducing Station A pressure reducing station (sometimes termed as “air set”) reduces and regulates the s...