Instrumentation and process control Pressure spring thermometer DIPIKSHA PATEL 130280105010

Introduction The accurate measurement of temperature is vital across abroad spectrum of human activities, Including industrial processes (e.g. making steel) Manufacturing; Monitoring (in food transport and storage), Health and safety. In fact, in almost every sector, temperature is one of the key parameters to be measured

The means of accurately measuring temperatures has long fascinated people. One of the differences between temperature and other physical concepts, such as mass or length, is that it is subjective. Different people will have different perceptions of what is hot and what is cold. To make objective measurements, we must use thermometer in which some physical property of a substance changes with temperature in a reliable and reproducible way.

Pressure Thermometer Liquid Pressure Thermometers. Vapour Pressure Thermometers.

1.Liquid Pressure Thermometers.

Vapour Pressure Thermometers.

CONSTRUCTION The bulb is composed of a cylindrical piece of metal tubing closed at one end with the capillary and extension neck inserted at other end. the size of the bulb varies continuously depending upon type of filling medium ,the temp span of instrument and the length of capillary tubing with which it is used . A thermal wall may be used with thermometer bulb in application where temp of fluid under pressure is to be measured, where extra strength is required. The mechanical fit between thermometer bulb and thermal well is made as reasonably close as possible.

CONSTRUTION Capillary connects the thermometer bulb to the receiving element. the distance between bulb and instrument is generally restricted to 200 ft or less because of the high costs of system and greater length of capillary. For protection against damage or corrosion capillary is enclosed in armour tubing. The armor may be spiral-wound bronze, or stainless steel.

WORKING The cross section of the tube is elliptical. When pressure is applied to the inside of the tube ,the cross section deflects towards a more circular form, and this causes the tube to straighten ,thus moving the tip of the tube along an arc. The industrial pressure thermometer is either an indicating or recording instrument it may indicate the temperature by means of pointer sweeping over a circular dial,or it may record the temperature on a chart of circular form.

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