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...