TILI Automation

 In this topic, we will discuss the purpose of 100% and 30% valves. Why are both these valves required in power plants? Before starting with the discussion will see some basic aspects What is a Control Valve? A control valve is installed in a pipeline to regulate the flow rate of the fluid (Liquid, Gas, or Steam) as a response to the controller output (manipulated variable). The controller can adjust the valve opening or closing at any stage between 0% to 100%. The control valve in a pipeline does the following tasks. Stopping and starting of flow Reduce and raise the flow rate Controls the flow direction What is Non-Return Valve (NRV)? This is a one-way valve that allows the fluid to flow in one direction only. As its name implies, non-return means there is only one-directional flow. This device ensures there is no backflow of fluid in the pipeline. These valves are generally used in pump discharges and steam water pipelines. The direction symbol provided on the valve shows the di...

 Explain why the direction of flow shown in the below image goes from left to right. What would happen if we sent fluid flow through this control valve in reverse direction i.e. from right to left instead? Fluid Flow Reversed through Control Valve If we were to use this valve “backwards,” the pressure drop across the plug would tend to “slam” it closed whenever it approached the closed position. In other words, the process fluid’s differential pressure drop would make it very difficult to maintain any plug position near full-closed. This is actually an example of a mechanical feedback system. As the valve closes, the pressure drop across it (in most processes) usually rises because other pressure losses in the piping system decrease with decreased flow, leaving the valve to drop all the fluid pressure. Since plug position has an effect on pressure drop, and pressure drop exerts a mechanical force on the plug, there is a system of feedback at work here. In the proper flow direction, the feedba...

 Magnetostrictive Level Transmitter is a two wire loop powered instrument which transmits an analog 4-20mA loop current in proportion to the measured liquid level in the tank. This type of level transmitter uses a special type of sensor probe with a magnetic float to sense the level. The float is selected such that it’s specific gravity is lighter than the liquid whose level is to be measured, so that it always floats on the liquid. Magnetostrictive Instrument Image Courtesy: ekotech This sensor probe with magnetic float is inserted into a tank or briddle where the liquid level to be measured. The float raises or falls as per the liquid level in the tank. This level transmitter operation is based on the principle of magnetostrictive technology. The transmitter generates a high-current pulse and transmitted down to the sensor probe, this is called as wave guide. This wave guide produces a circular magnetic field around the sensor probe (wire). The float also carries a permanent magn...

 Load cells are special force transducers used for measuring weight or force in various applications. These are integral to weighing systems in various industries, including aerospace, marine, automotive. The reason being they produce highly accurate load measurement data. That is why it is essential to inspect and calibrate them routinely. Weighing scale calibration services ensure accurate load cell readings and help identify operational issues so that negative consequences can be prevented. How to Calibrate Load Cells Why You Should Calibrate Load Cells Load cells show signs of wear and tear over a period of years. Frequency of use, environmental causes such as temperature, and aging are some of the contributing factors to the deterioration of load cells. Faulty cables and instruments, particle accumulation and matter buildup, mechanical defects, incorrect installation, and the influence of electricity can also lead to inefficiency. That is why routine calibrations should be per...

 Types of Contact Vibration Measurement Path Measurement Potentiometer Type LVDT Type Speed Measurement Electrodynamics Seismometer Acceleration measurement Piezoelectric sensor Piezo-resistive sensor Resistive sensor Inductive sensor Path Measurement Potentiometric Transmitter The potentiometric transmitter is a one-dimensional position sensor. It is based on the potentiometer, an adjustable potential divider. A voltage is applied to a resistive track. A wiper runs along this resistive track and thus divides the resistor in two parts, as shown in figure (resistor R1 and R2). At different positions of the wiper, specific resulting voltages can be measured, due to the change in resistance. The wiper moves because it is attached to the motion of the vibrating object. The frequency ranges from 5 Hz to 2 kHz, which corresponds to a possible maximum acceleration of 20 g. Potentiometric transmitters can achieve measuring strokes from 1 mm up to 2 m with an infinite resolution. The operat...

 Types of Non – Contact Vibration Measurement Path Measurement Capacitance Eddy Current Hall Effect Optical Speed Measurement Laser-Doppler vibrometer Seismometer Acceleration measurement Path measurement Capacitive Principle The capacitive principle can be applied to non-contact vibration measurement, if the vibrating object or a relevant part of it is useable as a plate of a capacitor. In order to do measurements, a second plate is needed. Now the whole setup works like any common capacitor. The variation of the distance of the two plates is proportional to the capacity. An AC supply is connected to the capacitor. Depending on the distance between the plates, a specific amplitude can be recognized by the sensor which can be used for further processing. The measuring stroke reaches from several μm μm to mm with a resolution of some nm. The band of frequencies lies between 0 and 6 kHz. However this non-contact method is not feasible for application in high quantities and must be ad...

 Mechanical Vibration Switches provide vibration protection for low- to medium-speed machinery. An inertia sensitive mechanism activates a snap-action switch with SPDT output contacts if the vibration exceeds an adjustable setpoint. The mechanical vibration switch contacts can be used to activate an alarm or initiate equipment shutdown as per our requirement. Some optional settings also available like Electrical (remote) reset (right side figure) with start-up time delay and a second set of SPDT output contacts to accommodate DPDT needs (e.g. separate trip and trip light circuits) are available. Mechanical Vibration Switch Mechanical Vibration Switches offer basic protection against gross changes in structural seismic acceleration. The operating mechanism is purely mechanical and consists of a tension spring attached to a pivoting plate on an over-center fulcrum – magnets are not employed. Normally, this plate is in an untripped position (Figure A). However, in the presence of suff...

 Proximity Transducer System provides an output voltage directly proportional to the distance between the probe tip and the observed conductive surface. It is capable of both static (position) and dynamic (vibration) measurements, and is primarily used for vibration and position measurement applications on fluid-film bearing machines, as well as Keyphasor and speed measurement applications.  Proximity Transducer System Proximity Transducer Systems provide an electrical signal that represents the distance between a conductive surface and the probe tip of the system. The Proximitor contains electronics that provide two functions: Generate a radio frequency (RF) signal using an oscillator circuit. Condition the RF signal to extract usable data using a demodulator circuit When conductive material is present in the RF field, Eddy Currents flow in the surface of that material. The penetration depth of the eddy currents depends on the material’s conductivity and permeability. 4140 st...

 A transducer that produces a voltage pulse for each turn of the shaft, called the Keyphasor. This keyphasor signal is used primarily to measure rotating shaft speed and serves as a reference for measuring vibration phase lag angle. It is an essential element in measuring rotor slow roll bow or runout information.The Keyphasor transducer is typically a proximity probe (recommended for permanent installations in which the probe observes a physical gap change event), an optical pickup (used for temporary installations in which the pickup observes a change in reflectivity event) or a magnetic pickup. Keyphasor is a Trademark owned by the Bentley Nevada Company. The system includes a proximity probe, extension cable, and proximitor sensor. Convention recommends that the prime keyphasor event is located on the driving unit. The keyphasor measurement required a coupling keyway or an elongated notch that can provide a once per turn event trigger for the signal pulse. Keyphasor The keyphas...

 This article provides the list of different types of Turbine Protective Devices like turbine over speed trip, low lube oil pressure, axial displacement, turbine temperature and turbine vibrations. Turbine Protective Devices Tripping Device Low Lube Oil Pr. Over Speed Trip Low Vacuum SOV for remote tripping Hi/Lo Extrn. Pr. Casing Expansion Extrn./Exhaust Temp Differential Expansion Generator Protection Axial Displacement Manual/Remote Trip Bearing Vibrations Casing/Rotor Temp. Bearing Temperatures Tripping Device When ever the turbine is to be tripped , the Governing oil pressure is drained by tripping device. Thus pressure in front of stop valve piston disc and control oil pressure falls, resulting in closure of stop valve and control valves. Over Speed Trip The over speed protection is formed by three independent sensors of turbine speed evaluation that act through a selection of the output signal two of three after exceeding a set value of security speed for an immediate impuls...