Wednesday, August 8, 2012

Hoses, Strainers, Sight Glasses and Expansion Bellows


Hose – Flexible pipe, normally small dia. maximum 4 to 6“ f generally 1-2“ f used when connecting points are not fixed / frequent removal is required, fixed fittings for mobility / carrying of equipment, etc. 

Standard for coupling is essential for every fixing / removal. Vibration isolation / expansion due to temperature variation. American standard hose coupling screw threads.


Types of Hoses

1. Garden hose

2. Chemical

3. Fire hose

4. Other hoses

garden chemical fire hoses

Available for a wide range of applications to suit.

Temperature- Up to 150 to 180 0c normally.

1. Pressure- Hydraulic hoses for very high pressure. 
2. Chemical resistance- Rubber /PVC/Neoprene/ Teflon, etc. 
3. Service condition (external)- corrosive/oily/dusty

corrugated interlocked hoses

Hoses as Per Type of Construction

1) Corrugated
2) Interlocked

Fixing of Connecting Ends to Hoses

1) By brazing or welding for metal hoses 
2) Push fit for rubber hoses 
3) By clamps, on fire hoses

Life of the Hose

1) Light duty – 1 –3 yrs. 
2) Medium duty – up to 5 yrs. 
3) Heavy duty – up to 8-10 yrs.


Types- duty wise

1) To filter, any dust/dirt/rust from converging fluid 
2) Use of perforated sheet, screens to filter out unwanted contaminants. 
3) Use bottle plate, change in flow of direction to prepared liquid/gases fluids from each other.


• In pump section to remove solids going into pump. 
• In air lines to remove moisture/oil from air. 
• In steam lines to prepare moisture from steam. 
• In gas lines to remove dust/rust from gases. 
• In air lines to remove dust, not from oil.


1) Y-type 
2) Basket type 
3) Duplex/triplex

Selection of Strainer On

1) Particle size 
2) Degree of removal 
3) Quantity of contamination 
4) Characteristics of contamination

a) Filter controls are the disposable type, strainers are normally reusable 
b) In filters media is a must, not so in strainers. 
c) Typical particle distribution in an industrial atmosphere.

Per cent by volume Particle Size
28 10-30
52 5-10
11 3-5
6 1-3
2 1-11/2
1 0-11/2
This table helps to decide suction strainers for air-compressors.

Strainer Requirements

1) Air lines 
2) Work lines 
3) Oil lines 
4) Gas Air lines 
5) Steam lines

Sight Glass

Used to determine flow continuity in pipeline.

1) Used normally for low pressure applications. 
2) Helps to detect air bubbles/discontinued flow level of contaminants/colour 
change of fluids. 
3) Double glass type with lighting arrangements for every variety. 
4) Bypass line provided to remove/clean light glass, when circuit is in 
operation condition.

Expansion Bellow- Rubber/Metallic


1) To absorb expansion due to change in temperature. 
2) To absorb mis-adjustment between equipment/connecting piping. 
3) For vibration isolation. 
4) To avoid stresses in piping.

Material of Construction

Depends upon the operating process, temperature, type of liquid, expansion/contraction cycle.

Rubber- used normally for low temperature/ low pr application.

Metal –used normally for high temperature / high pr application, for higher cycle of reversal of pr and temperature gradient.

Rubber- up to 25 psig,1500C. Used in condenser watts piping in steam power plant.

Expansion joint (metallic) for steam line.

Components of a Metal Bellow

1. Expansion bellow 
2. End flanges 
3. Internal sleeve 
4. Chemical roads 
5. Limit stops

Coefficient of Linear Expansion

Brass 0.104 Carbon 0.030
Bronze 0.100 Concrete 0.030
Iron 0.069 Glass 0.040
Wood 0.027 Marble 0.020

Consideration for use of expansion joints

1. Select joints for maximum temperature range 

2. Provide guides for limiting movement 

3. Movements to occur at expansion joints 

4. Mount expansion joint near and anchor to avoid sagging of pipe due to expansion joint weight

space for expansions joints types

5. Provide for corrosion protection, since corrugated character of expansion joints makes claming difficult.
6. If expansion joints are covered by insulation provide flexibility in insulation, and provision for clear movements.

Get Notified for new Tutorials:
*Check your email to confirm your subscription*


  1. What do you mean, when wrote "high pr application"

  2. Apologies for using short forms... I meant to write "high pressure application". This should help.

  3. Awesome post! Of course, a bellows maintain their high strength capability and custom design with varying thicknesses when compared with hoses.



© 2011 PIPING GUIDE - Designed by Ankit | ToS | Privacy Policy | Sitemap

About Us | Contact Us | Write For Us