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Material Specification

Chapter IIIHoses, Strainers, Sight Glasses and ExpansionBellows

Learning objectives

Reading this chapter will enable you to understand:

Types of Hoses Types and criteria for selection of strainers Sight Glass and its use Expansion Bellows Types and parameters to be considered

Contents

3.1 Hose3.2 Types of Hoses

3.3 Hoses as Per Type of Construction3.3.1Fixing of Connecting Ends to Hoses3.3.2Life of the Hose

3.4 Strainers3.4.1 Types3.4.2 Selection of Strainer on3.4.3 Strainer Requirements

3.5 Sight Glass3.6 Expansion Bellow- Rubber/ Metallic3.7 Material of Construction3.8 Components of a Metal Bellow3.9 Coefficient of Linear ExpansionSumming Up

3.1 Hose

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.

(ASA-B33.1.1935)

3.2 Types of Hoses

1. Garden hose2. Chemical3. Fire hose4. Other hoses

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Figure 3.1 title?-fig to be checked

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

Figure 3.2 title?

3.3 Hoses as Per Type of Construction

1) Corrugated2) Interlocked

3.3.1 Fixing of Connecting Ends to Hoses

1) By brazing or welding for metal hoses2) Push fit for rubber hoses

3) By clamps, on fire hoses

Hoses, Strainers, Sight glasses and Expansion Bellows

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Material Specification

3.3.2 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.

3.4 Strainers

Types- duty wise

1) To filter, any dust/ dirt/ rust from converging fluid2) 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.Uses: 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.

3.4.1 Types

1) Y-type2) Basket type3) Duplex/ triplex

3.4.2 Selection of Strainer On

1) Particle size

2) Degree of removal3) Quantity of contamination4) Characteristics of contamination

a) Filter controls are the disposable type, strainers are normally reusabletype.

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 5-1011 3-5 This table helps to decide

6 1-3 suction strainers for air-

2 1-11/ 2 compressors

1 0-1/ 2

3.4.3 Strainer Requirements

1) Air lines2) Work lines

3) Oil lines4) Gas Air lines5) Steam lines

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3.5 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/colourchange of fluids.

3) Double glass type with lighting arrangements for every variety.

4) Bypass line provided to remove/ clean light glass, when circuit is inoperation condition.

3.6 Expansion Bellow- Rubber/Metallic

Uses 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.

3.7 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 powerplant .

Expansion joint (metallic) for steam line.

3.8 Components of a Metal Bellow

1. Expansion bellow2. End flanges3. Internal sleeve4. Chemical roads

5. Limit stops

3.9 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

3.10 Consideration for use of expansion joints

Hoses, Strainers, Sight glasses and Expansion Bellows

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Material Specification

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

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.

Figure 3.3 title?

Summing Up

In this chapter youve learnt about types of hoses and their characteristics,

types of strainers and their characteristics, sight glass and its use and factors

to be considered in the design of expansion bellows.