TILI Automation

The Diaphragm Pressure Gauge uses the elastic deformation of a diaphragm (i.e. membrane) instead of a liquid level to measure the difference between an unknown pressure and a reference pressure. A typical Diaphragm pressure gauge contains a capsule divided by a diaphragm, as shown in the schematic below. One side of the diaphragm is open to the external targeted pressure, PExt, and the other side is connected to a known pressure, PRef,. The pressure difference, PExt – PRef, mechanically deflects the diaphragm.   The membrane deflection can be measured in any number of ways. For example, it can be detected via a mechanically-coupled indicating needle, an attached strain gage, a linear variable differential transformer(LVDT; see the schematic below), or with many other displacement/velocity sensors. Once known, the deflection can be converted to a pressure loading using plate theory. Many pressure sensors depend on the deflection of a diaphragm for measurement. The diaphragm is a fle...

What is Impulse Piping? The impulse piping is the one which connects the process outputs to the transmitter. It must convey the process pressure accurately. If for example, the gas collects in a liquid-filled impulse line, or the drain of a gas-filled impulse line becomes plugged, it will not convey the pressure accurately. Since this will cause errors in measurement output, selecting the proper piping method for the process fluid (gas, liquid or steam) is very important. We discuss below some of the most common routing principles for impulse piping. Differential Pressure Transmitters Hook up In differential pressure transmitters, there is a chance that process fluid (liquid, gas or vapors) may accumulate inside the impulse piping that can cause inaccurate reading of pressures. There are three cases as depicted by the figure. 1. Liquid If the process fluid is liquid, the transmitter should be placed lower than the taps. 2. Gas If the process fluid is gas, the transmitter should be plac...

 A capillary is generally built up from a tube, an armor, and optionally a protective sleeve. Table of contents Principle Importance of Capillary Tubing Tube Size Capillary Tube Material Precautions Process Temperature Effect Ambient Temperature Effect Mounting Effect Advantages Disadvantages Applications Principle The capillary tube is of small internal diameter, an appropriate method for separating a pressure instrument such as a gauge or transmitter from the process tapping/connection. Capillary tubing is used to separate the direct connection between the measuring instrument and the process tapping point. We can install the instrument as per our convenience and easy access for the maintenance. The capillary tubing is filled with some liquid inside it, usually it is glycerine but can be changed as per application need. With help of this, the readings can be taken at a more convenient and accessible location to meet the demand for remote measurement/reading.  Capillary tubes...

 Taking a DP, gauge, or absolute pressure reading from a process involves creating process connections so the pressure can reach the sensor. Impulse Line Frequently this is done via impulse lines. The impulse line carries the process pressure from the tapping point to the transmitter. In some cases, these can be short and very direct, or they may need to be long to allow mounting the transmitter some distance from the process equipment. The transmitter should be installed below the process tapping points to a wall or other rigid mounting using the optional bracket assembly or similar rigid bracket. The transmitter should be piped up in compliance with the pressure transmitter installation guidelines with the process tappings taken to the side of the pipe work. The transmitter should be mounted within two degrees of the horizontal, small variations in mounting attitude will affect the transmitter zero point, however, this may be calibrated out during the initial commissioning proced...

 Long before there were pressure transmitters, there were mechanical pressure gauges. The concept of a curved Bourdon tube dates back to the mid 19th century and there are devices available today little removed from that time. Gauges operate using a delicate mechanism with springs and gears, making them vulnerable to shock and damage. Pressure Gauge Most operators have seen typical failures including broken glass, bent indicator needles, or needles pointing straight down from broken gearing. In many environments, pressure transmitters are considered disposable due to their low cost and frequent failures. Gauge Problems Numerous studies have shown that vibration is the main cause of pressure gauge failure in manufacturing facilities. Vibration has a negative impact on gauge accuracy in two ways. First, it is difficult to read the pointer on a dial when a gauge is vibrating. Second, incremental damage to the pointer mechanism from vibration can eventually move a pointer off zero, pro...

 Displacer Level Transmitter 5-point calibration Question : Determine a basic 5-point (0%, 25%, 50%, 75%, and 100%) calibration table for the displacer level transmitter in this scenario: The cylindrical displacer weighs 15 pounds (dry) and has a diameter of 2 inches. The process liquid is water. The 0% process liquid level (LRV) is even with the bottom of the displacer. Assume an electronic transmitter mechanism with an output range of 4 to 20 mA. Fill the missing fields in the below table. Answer :

 Differential pressure (DP) transmitters are used to measure the interface of two fluids that have different specific gravities (S1 & S2). To make an interface measurement, the overall level must be at or above the low pressure tap at all times. It is important that the level be large enough to create a reasonable DP between the two specific gravity extremes. This measurement can be done with or without remote seals. However, from a maintenance point of view, it may be easier to use a remote seal assembly; keeping the wet leg at a constant height can be difficult in some applications. To determine the calibrated range for the transmitter, four assumptions need to be made: At the lower calibrated value, 4 mA point, the tank is filled with the lighter fluid. At the upper calibrated value, 20 mA point, the tank is filled with the heavier fluid. The taps leading to the transmitter are flooded at all times. The overall level should be equal to or higher than the upper (low pressure)...

 DP Transmitters with remote seals allow the transmitter to be removed from direct contact with the process fluid. Remote seals are useful when: 1. The process temperature is outside of the normal operating limits of the transmitter and cannot be brought into those limits with impulse piping. 2. The process is corrosive and requires frequent transmitter replacement. 3. The process requires unusual materials of construction. 4. The process contains numerous solids or is viscous; either condition could plug the impulse piping. 5. The application requires the use of sanitary connections. 6. There exists a need for easy cleaning of the process from the connections to avoid contamination between batches. 7. There exists a need to replace wet legs to reduce maintenance on applications where the wet leg is not stable or often needs to be refilled. Seals function as an extension of the transmitter. The basic measurement of level follows the same principle as pressure transmitters without s...

 To assure the safety and profitability of processes, it is essential to be equipped with instruments providing reliable and precise measurements of level. At the basics of level measurement, it is simply about determining the position of a surface inside a tank, reactor or other vessel. More precisely, level measurement is the determination of the linear vertical distance between a reference point (usually the base of a holding container) and the surface of either a liquid, the top of a solid, or the interface of two liquids. Precise control of the level of liquid in a tank, reactor, or other vessel is important in many process applications. Level measurement is often used for inventory management. To provide good control, accurate measurement is essential and several devices and systems are available for measuring product level. Each is designed to provide accurate level measurement, although measurement precision and principles of operation vary among devices. All level measurem...

An ultrasonic level transmitter is mounted on the top of the tank and transmits an ultrasonic pulse down into the tank. This pulse, travelling at the speed of sound, is reflected back to the transmitter from the liquid surface. The transmitter measures the time delay between the transmitted and received echo signal and the on-board microprocessor calculates the distance to the liquid surface using the formula. Distance = ( Speed of sound in air x time delay) / 2 Once the transmitter is programmed with the bottom reference of the application – usually the bottom of the tank – the liquid level is calculated by the microprocessor.The basic equation for calculating the tank level is Level = Tank Height – Distance   Basic Concept and Elements of the Ultrasonic Level Measurement Minimum measuring distance (Xm): (also known as the “Dead Band”) is a feature common to all ultrasonic level meters. This is a short range in front of the sensor within which the ultrasonic device can not measure...

  Introduction DPharp transmitters with advanced software functionality eliminate this time consuming task. With maintenance shops getting smaller, finding equipment that allows us to do more with less becomes a priority.Level transmitter configuration can be very time consuming. Calculations required to determine proper range values for traditional transmitters can become complex due to the physical layout of an application. Application Using typical smart or conventional products all of the following must be considered: The specific gravity of the process; Precise location of 0% and 100%; Specific gravity of the capillary fill fluid or sealing liquid (for impulse tubing); Vertical height of capillary or impulse piping; Exact orientation of the transmitter to the vessel; Vertical distance between the flanges. Depending on the application, the vessel may be open (referencing atmosphere), or closed (under some blanket pressure). Elevation is typically used when the vessel is closed....

Magnetic Level Gauge Inside the indicator tube is a lightweight magnetized indicator or series of metallic flags. The indicator is magnetically coupled to the float and moves up and down with the liquid level. The indicator allows the operator to read the level from more than 100 feet away. The only moving parts are the float and the indicator. Theory : Magnetic level gauges work on the principle of communicating vessels, therefore the level in the measuring chamber will be the same as the level in the vessel. The measuring chamber is fitted with a float, which has a magnet inside. The float with magnet will float on the medium and the magnet in the float will turn the flaps of the indicating rail. The float in the measuring tube is standard not pressurized and has no magnetic or mechanical guidance. This construction makes the float less dangerous than a float which is standard pressurized. When necessary Hadro can produce a pressurized float. With the below mentioned process conditio...

 Definition of Level Indicator Level indicators are devices used in the measurement of level of fluids at various industrial applications. These devices are used to determine the level of liquid in tanks, drums. pressure vessels etc.. There are many level indicators to suit the needs of different applications. Normally, fluids are used in many forms in highly commercial industries. Without proper devices it will be very difficult to find the quantity and level of fluid stored. Also, in certain situations where the nature of fluid is dangerous or the place in which the liquid is stored is of such a nature that it is manually impossible to find the level, then the level indicators are of utmost importance. Depending on the type of application used, the type of level indicator should be selected. For example, in the process industry, tubular level indicators are used for better visual liquid level indication. If it is for non-contact type level measurement, then radar type indicators ...