Inst ToolsInst ToolsInst Tools
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Search
  • Books
  • Software
  • Projects
  • Process
  • Tools
  • Basics
  • Formula
  • Power Plant
  • Root Cause Analysis
  • Electrical Basics
  • Animation
  • Standards
  • 4-20 mA Course
  • Siemens PLC Course
Reading: What is Capillary Tubing? – Advantages and Disadvantages
Share
Font ResizerAa
Inst ToolsInst Tools
Font ResizerAa
  • Courses
  • Design
  • PLC
  • Interview
  • Control System
Search
  • Courses
  • Automation
    • PLC
    • Control System
    • Safety System
    • Communication
    • Fire & Gas System
  • Instrumentation
    • Design
    • Pressure
    • Temperature
    • Flow
    • Level
    • Vibration
    • Analyzer
    • Control Valve
    • Switch
    • Calibration
    • Erection & Commissioning
  • Interview
    • Instrumentation
    • Electrical
    • Electronics
    • Practical
  • Q&A
    • Instrumentation
    • Control System
    • Electrical
    • Electronics
    • Analog Electronics
    • Digital Electronics
    • Power Electronics
    • Microprocessor
  • Request
Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Inst Tools > Blog > Pressure Measurement > What is Capillary Tubing? – Advantages and Disadvantages

What is Capillary Tubing? – Advantages and Disadvantages

Capillary tubing is used to separate the direct connection between the measuring instrument and the process tapping point.

Last updated: October 17, 2023 2:10 pm
R Jagan Mohan Rao
Pressure Measurement
No Comments
Share
6 Min Read
SHARE

A capillary is generally built up from a tube, an armor, and optionally a protective sleeve.

Contents
Capillary Tubing PrincipleImportance of Capillary TubingTube SizeCapillary Tube MaterialPrecautionsProcess Temperature EffectAmbient Temperature EffectMounting EffectAdvantagesDisadvantages of Capillary TubingApplications of Capillary Tubing

Capillary Tubing 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 also serves as the purpose of a cooling element as the distance between the process tapping and the instrument will be more than the direct type installation. Also, there will be no direct contact between the instrument sensor and the process.

What is Capillary Tubing
Image Courtesy: Micro

Importance of Capillary Tubing

A capillary tube is commonly used to connect the diaphragm seal remote with the pressure instrument.

It allows separation between the measuring instrument such as pressure gauge or transmitter with the process connection.

Using a capillary tube on a mechanical gauge normally requires the use of a gauge supporting arrangement and gauge adaptor or some other form of surface mount.

In a temperature measurement, the pneumatic temperature transmitter is connected with a sensor.

The sensor is a bulb filled with either mercury, gas, or vapor.

Through the capillary tube, expanded bulb fill makes the movement of the bellows or a C- type bourdon tube as per the corresponding temperature of the process medium.

The transmitter is located at an accessible place.

Tube Size

1/16 inch to 1/8 inch capillary tubes are used in instrumentation applications.

Capillaries with suitable diameters are used for optimal performance.

Capillary Tube Material

  • Stainless steel,
  • Copper,
  • Inconel,
  • Hastelloy.

Precautions

Precautions when using a capillary tube:

  • Process temperature effect.
  • Ambient temperature effect.
  • Mounting effect.

Process Temperature Effect

Process temperature effect on the diaphragm seal and of the fill fluid in the capillary through heat transfer.

The capillary tube has an excellent function for cooling down of process temperature changes.

But, the warming through of the process media temperature that causes the capillary tube to fill liquid to either expand or contract, the possibility of changing the volume of the fluid.

This is possible in the case of the short length of the capillary, this generates an error in the pressure reading as a function of the change of total volume of the tubing, pressure instrument, and diaphragm seal.

Ambient Temperature Effect

It includes seal temperature effect and ambient temperature effect.

Exposure of an electronic pressure transmitter to excessively high ambient or process temperature can impair the instrument operation, affect its performance or even lead to a partial or total failure of the instrument.

To prevent exposure to excessively high ambient temperatures.

Consider installing the instrument in a safe area from major heat sources.

In extremities, cool down the instrument vicinity using compressed air or any equivalent mean.

The seal temperature effect relates to the pressure produced on the diaphragm when the temperature changes. The pressure is corresponding to an expansion or contraction of the fill fluid in the capillary.

Mounting Effect

A level difference between the installed pressure instrument and the diaphragm seal creates a pressure indication error.

But, by the method of a known level difference can be compensated for during the calibration of the diaphragm seal assembly.

On differential pressure (DP) applications, the sealing effect is usually compensated by having the same length of capillaries for both LP and HP ports of the instrument.

Advantages

Protecting the instrument from high or low process temperature effects.

Personnel safety due to proper accessibility. 

Disadvantages of Capillary Tubing

Longer capillary lengths affect the accuracy as subjected to ambient temperature effects.

Capillary length to be as short as possible to avoid delay response time.

Applications of Capillary Tubing

  • Distant reading.
  • Capillary is to be used in combination with gauges, diaphragm seals, transmitters, switches.
  • Chromatography.

Read Next:

  • Process Control Loop Testing
  • Question on Remote Seal with Capillary Tubing Transmitter
  • DP Transmitter Interface Level Measurement Principle
  • Calibration for Diaphragm Seal with Capillary
  • How much Pressure will Remote Seal Pressure Transmitter Indicate?
Don't Miss Our Updates
Be the first to get exclusive content straight to your email.
We promise not to spam you. You can unsubscribe at any time.
Invalid email address
You've successfully subscribed !

Continue Reading

Pressure Gauge Calibration Procedure
Pressure Detection Circuit
Pressure Gauges with Bourdon Tube Principle
Pressure Gauge Pulsation Damping
McLeod Gauge Working Principle
Bourdon Tube Pressure Gauge Working Principle Animation
Share This Article
Facebook Whatsapp Whatsapp LinkedIn Copy Link
Share
Leave a Comment

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Stay Connected

128.3kFollowersLike
69.1kFollowersFollow
210kSubscribersSubscribe
38kFollowersFollow

Categories

Explore More

Pressure Gauge with Block and Bleed Valves
How to Measure Pressure in Inches of Water Column
Resistance Type Pressure Transducers Principle
Bellows Pressure Sensors Working Principle Animation
Differential Pressure Switch Calibration Procedure
Bourdon Tube Pressure Gauge Advantages and Disadvantages
Pressure Transmitter Animation
Difference Between Absolute and Gauge Pressure

Keep Learning

Semi Conductor or Piezo Resistive Strain Gauge Principle

Semi Conductor or Piezo Resistive Strain Gauge Principle

Gauge Display Scale

How to Read Gauge Analog Scales

Pressure Transmitter Calibration Procedure

Pressure Transmitter Calibration Procedure

Diaphragm Seal Material Selection

Diaphragm Seal Material Selection

Pressure Transmitter Basics

Pressure Transmitter Applications

DP transmitter with Manifold

Pressure Transmitter Manifolds

How to Connect HART Communicator with DP Transmitter

15 HART Communicator Questions

Identify the Pressure Gauge Error

Identify the Pressure Gauge Error

Learn More

Digital Electronics Multiple Choice Questions

Half Adder and Full Adder Objective Questions

Advances in Control System

Neural Networks

process conditions, Find out the Circuit Components Status

As per Process Conditions, Find out the Circuit Components Status ?

calibrating-and-testing-rtd-sensors

RTD Calibration Procedure

Diagram of Oscillator Circuit

Barkhausen Criterion

Reflex Level Gauge Parts

What is Reflex Level Gauge?

HVAC System Heat Transfer Loops

Heat Transfer Loops in HVAC System

Applications of Robots

Applications of Robots in Various Fields

Menu

  • About
  • Privacy Policy
  • Copyright

Quick Links

  • Learn PLC
  • Helping Hand
  • Part Time Job

YouTube Subscribe

Follow US
All rights reserved. Reproduction in whole or in part without written permission is prohibited.
Welcome Back!

Sign in to your account

Username or Email Address
Password

Lost your password?