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8/3/2019 Steam Traps SIP

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STEAM SYSTEM

&

STEAM TRAPS

BY: Muhammad Akbar Rao


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Contents

Introduction

FFC Steam Network

Steam traps

Classification Selection

Monitoring

Problems associated with traps

Monitoring system

Exercises


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INTRODUC

TION


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Introduction

Steam is water in vapor phase.

It is one of the oldest industrial tools

It allows the energy of fuel burned in a boiler

to be carried to some other point where it

can provide mechanical energy through an

engine or, more commonly, to provide heat.


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HEAT

Temp

Water

Steam

Ice

Latent heat

Boiling ofWater


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Steam Terminology

Sensible heat

Heat that produces temperature rise

Latent heat

The heat that produces phase change

Saturated steam

The dry steam at its boiling pointcorresponding to pressure.

Superheated steam

The steam heated above the saturationtemperature at a particular pressure


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Steam Heat Content


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Steam Terminology

Flash steam

Steam that results when saturated water or

condensate is discharged to a low pressure

Enthalpy

Total energy due to pressure and temperature

of a liquid or vapor.

Superheat Heat added to dry saturated steam


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Flash Steam Calculation


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Flash Steam Curve


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PV Diagram

P

V


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Pressure Temperature Diagram


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Factors Affecting Steam System

Water Hammer

Condensate moving along steam form solid slug

moving at steam velocity result in water hammer

which can cause damage to piping.

Air

Before start-up boi ler and piping are full of air,

therefore it must be removed during startup. Steam

air mixture has less temperature than steam alone at

a specific pressure.

Gases

Oxygen and CO2 are responsible for corrosion.


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Water Hammer


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Condensate Drainage


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Condensate Drainage


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Steam Line Branches


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Steam Line Reduction


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Steam Tables

Listing of heat content of steam in KJ/Kg

and its volume in m3/kg at various

pressures and temperatures. The

properties of saturated steam are mostfrequently summarized.


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Saturated Steam

Specific enthalpy

Specific

volume

steamWater Evaporation Steam

Pressure Temp (hf) (hfg) (hg)

bar kPa C kJ/kg kJ/kg kJ/kg m3/kg

absolute

0.30 30.0 69.10 289.23 2336.1 2625.3 5.229

0.50 50.0 81.33 340.49 2305.4 2645.9 3.240

0.75 75.0 91.78 384.39 2278.6 2663 2.217

0.95 95.0 98.20 411.43 2261.8 2673.2 1.777

1.00 100.0 99.63 417.51 2257.9 2675.4 1.694

1.013 101.3 100.00 419.06 2257.0 2676.0 1.673

gauge

0 0 100.00 419.06 2257.0 2676.0 1.673

0.10 10.0 102.66 430.2 2250.2 2680.2 1.533

0.20 20.0 105.10 440.8 2243.4 2684.2 1.414

0.30 30.0 107.39 450.4 2237.2 2687.6 1.312

0.40 40.0 109.55 459.7 2231.3 2691.0 1.225

0.50 50.0 111.61 468.3 2225.6 2693.9 1.149

0.60 60.0 113.56 476.4 2220.4 2696.8 1.088

0.70 70.0 115.40 484.1 2215.4 2699.5 1.024

0.80 80.0 117.14 491.6 2210.5 2702.1 0.971

0.90 90.0 118.80 498.9 2205.6 2704.5 0.923

1.00 100.0 120.42 505.6 2201.1 2706.7 0.881

1.10 110.0 121.96 512.2 2197.0 2709.2 0.841


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Pressure

lbs. / sq. in. Sat.

Temp

t

Total Temperature--Degrees Fahrenheit ( t)

Abs.

P'

Gauge

P350 400 500 600 700 800 900 1000 1100 1300 1500

15.0 0.3 213.03V

hg

31.939

1216.2

33.963

1239.9

37.985

1287.3

41.986

1335.2

45.978

1383.8

49.964

1433.2

53.946

1483.4

57.926

1534.5

61.905

1586.5

69.858

1693.2

77.807

1803.4

20.0 5.3 227.96 Vhg

23.9001215.4

25.4281239.2

28.4571286.9

31.4661334.9

34.4651383.5

37.4581432.9

40.4471483.2

43.4351534.3

46.4201586.3

52.3881693.1

58.3521803.3

30.0 15.3 250.34V

hg

15.859

1213.6

16.892

1237.8

18.929

1286.0

20.945

1334.2

22.951

1383.0

24.952

1432.5

26.949

1482.8

28.943

1534.0

30.936

1586.1

34.918

1692.9

38.896

1803.2

40.0 25.3 267.25V

hg

11.838

1211.7

12.624

1236.4

14.165

1285.015.685

1333.617.195

1382.5

18.699

1432.1

20.199

1482.5

21.697

1533.7

23.194

1585.8

26.183

1692.7

29.168

1803.0

50.0 35.3 281.02V

hg

9.424

1209.910.062

1234.911.306

1284.1

12.529

1332.913.741

1382.014.947

1431.7

16.150

1482.2

17.350

1533.4

18.549

1585.620.942

1692.5

23.332

1802.9

60.0 45.3 292.71V

hg

7.815

120

8.0

8.354

1233.5

9.400

1283.2

10.425

1332.3

11.438

1381.5

12.446

1431.3

13.450

1481.8

14.452

1533.2

15.452

1585.3

17.448

169

2.4

19.441

180

2.8

70.0 55.3 302.93V

hg

6.664

1206.0

7.133

1232.0

8.039

1282.2

8.922

1331.6

9.793

1381.0

10.659

1430.9

11.522

1481.5

12.382

1532.9

13.240

1585.1

14.952

1692.2

16.661

1802.6

80.0 65.3 312.04V

hg

5.801

1204.0

6.218

1230.5

7.018

1281.3

7.794

1330.9

8.560

1380.5

9.319

1430.5

10.075

1481.1

10.829

1532.6

11.581

1584.9

13.081

1692.0

14.577

1802.5

90.0 75.3 320.28V

hg

5.1281202.0

5.5051228.9

6.2231280.3

6.9171330.2

7.600

1380.08.2771430.1

8.950

1480.8

9.6211532.3

10.290

1584.611.6251691.8

12.956

1802.4

100.0 85.3 327.82V

hg

4.590

1199.9

4.935

1227.4

5.588

1279.3

6.216

1329.6

6.833

1379.5

7.443

1429.7

8.050

1480.4

8.655

1532.0

9.258

1584.4

10.460

1691.6

11.659

1802.2

120.0 105.3 341.27 Vhg

3.78151195.6

4.07861224.1

4.63411277.4

5.16371328.2

5.68131378.4

6.19281428.8

6.70061479.8

7.20601531.4

7.70961583.9

8.71301691.3

9.71301802.0

140.0 125.3 353.04V

hg

3.4661

1220.8

3.9526

1275.3

4.4119

1326.8

4.8588

1377.4

5.2995

1428.0

5.7364

1479.1

6.1709

1530.8

6.6036

1583.4

7.4652

1690.9

8.3233

1801.7

160.0 145.3 363.55V

hg

3.0060

1217.4

3.4413

1273.3

3.8480

1325.4

4.2420

1376.4

4.6295

1427.2

5.0132

1478.4

5.3945

1530.3

5.7741

1582.9

6.5293

1690.5

7.2811

1801.4

180.0 165.3 373.08V

hg

2.6474

1213.8

3.0433

1271.2

3.4093

1324.0

3.7621

1375.3

4.1084

1426.3

4.4508

1477.7

4.7907

1529.7

5.1289

1582.4

5.8014

1690.2

6.4704

1801.2

200.0 185.3 381.80V

h

2.3598

1210.1

2.7247

1269.03.0583

1322.63.3783

1374.3

3.6915

1425.5

4.0008

1477.04.3077

1529.1

4.6128

1581.95.2191

1689.8

5.8219

1800.9

Superheated Steam


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Advantages of steam

Requires smaller pipes to transfer specific

amount of heat.

It is lighter, so steam lines are lighter in weight

Flows in response to pressure drop and requiresno pumping

Heat transfer coefficients are high

Steam fills any space at uniform temperature for

even heating

Load can be varied easily within defined limits;

no need of variable pumps and valves.


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Steam VS other Heating MediumsSTEAM HTHW HT OIL

Heat Content High Hl=2100Kj/kg Moderate Poor Sp heat 0.4 ~0.7

Cost Cheap but WT cost Cheap Expensive

H.T. Co-eff Good Moderate Relatively poor

Pressure Reqd High press for high temp High press for hi temp No Press for hi temp

Circ. Pump Not required Required Required

Pipe size Small Large Large

Load Control Easy Difficult Difficult

Traps Required Not Required Not Required

Condensate Yes No No

Flashing Yes No No

Blowdown loss Yes No No

Corrosion Yes Moderate No

Fire risk No No Yes

Flexibility Yes Less No


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FFCSTEAM NETWORK

Varieties of steam

-LS (Low pressure steam) 3.8 kg/cm

2

150

oC.

-MS (Medium pressure steam) 24 kg/cm2 240oC.

-HS (High pressure steam) 39 kg/cm2 390oC.

-KS (Very high pressure steam) 104 kg/cm2 510oC.


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4 . 2 K g/ cm2g 1 9 7 C

0.0

0.0


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Steam Traps

Basics of steam traps.

Significance of steam traps To remove

- Condensate

- Air

- Non Condensable gases


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TECHNIQUES FOR STEAM SYSTEM IMPROVEMENT

Techniques to minimize the load on steam traps

Improve BFW quality (Avoid Priming)

Avoid high load on boiler

Improve insulation of steam lines.

Reducelength of steam

lines

Audits of steam network


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BFW and STEAM

distribution system

Pre-heatingDe-aerator

V-201

B-605B-601/602

KS header

HS header

LS header

Hydrazine


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CLASSIFICATION OF STEAM TRAPS

Thermostatic

- Principle of working

- Heat transfer coefficient difference b/w steam &

condensate.

Mechanical

- Principle of working.

- Internal arrangement.

Thermodynamic

- Working on the difference is change of state.


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THERMOSTATIC TRAPS

Rapid response on change in temp.

Remove air/ non condensable.

Their coaching leg should be at least 3 ft long for better response.

Types of Thermostatic Traps:

1- Liquid expansion.

2- Bellows traps.

3- Bimetallic traps.


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LIQUID EXPANSION

This is one of the simplest thermostatic trap. An oil filled element

expands / contracts for opening / closing of valve.

1- Diagram

2- Graph


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Response Changes with Change in pressure as temp. varies with pressure


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Typical balanced pressure capsule

arrangement


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ADV

ANTAGES- Rugged.

- Good air handling capability.

- Withstand water hammer.

-C

an be mounted on any position.

ADVANTAGES- Dirt particles can prevent tight close.

- Requires substantial sub cooling.

- Slow response to changing condensate loads.

- Only works at temperature.


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BELLOWS TRAPS

Their valve actuator is a capsule or bellow filled with

vaporizing liquids which has boiling point somewhat lower

than water.

Diagram

Graph


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BELLOWS TRAPS


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ADVANTAGES

- Excellent Air handling capacity.

- Energy efficient.

- Condensate discharge temperature follows the saturation

curve.

- Various condensate discharge temperature.

- Can be mounted in several positions.

- Simple construction.

- small size and wt.

DISADVANTAGES- Delicate bellows.

- Not suited for high pressure.


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BIMETALLICThese traps utilize the sensible heat in the condensate in

conjunction with line pressure to open and close a valve.

- Diagram

- Graphs


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Simple bimetallic traps


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MULTI STRIPS BIMETALLIC STRIPS


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ADVANTAGES- Rugged.

- Energy efficient.

- Withstand water hammer.

- Capable of discharging temp. adjustment.

- Simple construction.- Can be mounted on several position.

DISADVANTAGES- Dirt particles can prevent tight valve closing.

- Balance may effected due to back pressure.- Relatively slow response to changing condensate loads.

- Bimetallic elements corrosion problem.


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Disc Spring Thermostatic


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MECHANICAL TRAPSMain Features:

- Mechanical traps are phase detectors.

- These are independent of temp and pressure.

- These are extremely energy efficient.

BALL FLOAT TRAPS:

These traps are widely used on the plants. The opening and

closing of the valve is caused by changes of the condensate

level with in the traps shell.


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SIMPLE FLOAT TRAP


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Float Traps


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ADVANTAGES- Unaffected by sudden or wide pressure changes.

- Responds very quickly to condensate load changes.

- Continuous discharge.

- Condensate discharge temp. Closely follow saturation

curve.

- Simple construction.

DISADVANTAGES- Relatively large and heavy.

- Float easily damaged by water hammer.

- Can be mounted only in one position.- Requires auxiliary air vent which is an additional source

of

failure.


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INVERTED BUCKETAs the name implies the working portion consists of an

inverted bucket attached through a lever to a valve. An

essential part of the trap is the small air vent hole in the top of

the bucket.

-Step-1

-Step-2

-Step-3

-Step-4


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COMPLETE CYCLE OF INVERTED BUCKET TRAP


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Inverted Bucket Trap


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ADVANTAGES- Simple construction.

- Rugged.

- Condensate discharge temp. Closely follow the saturation

curve.

- Fast response the change condensate loads.

DISADVANTAGES- Marginal air handling during startup.

- Can lose prime and is not self priming.

- Can be mounted only us a single position.

OPEN BUCKET TRAPThis is also member of Mechanical traps but it is being used rarely.


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Open Bucket


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THERMODYNAMIC TRAPSMain Features:

- These traps are phase detectors.

- They can differentiate b/w liquids and gases.

- They can not differentiate b/w stream and air or other

non-condensable gases.Types of Thermodynamic Traps:

1.Disc traps

2.Piston Traps

3.Lever Traps

4.Impulse

5.Labyrinth

6.Orifice Traps


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DISC TRAPS:

This is the commonest type of trap relying on the fact thathot condensate released in pressure will produce flash

steam. The trap is supremely simple.

Cause i Condensate Removal Phase:

Disc A is raised from the seat C by incoming pressure,allowing air and condensate to pass radially outwards under

the disc before discharging through outlet B.

Cause ii:

Cause iii:

Cause iv:


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DISC TRAPS


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DISC TRAPS


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Advantages:

- Simple construction.- Small size and

- Can be mounted in any position.

- Rugged.

- Withstand water hammer

Disadvantages:

Marginal air handling capability

Condensate discharge temp. cannot be adjusted

Excessive back pressure in return systems can prevent trap from

closing High discharge noise level.


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IMPLUSE TRAPCONSTRUCTION

It consists of a hollow piston A with a piston disc B working

inside a tapered position C which acts as a guide.

WORKING

At start up the main valve rests on the seat D leaving a

passage of flow through the clearance b/w piston and cylinder

and the hole E at the top of the piston.

Increasing flow of air and condensate will act on the piston

disc B and lift the main valve off its seat to give increased flow.

Some condensate will also flow through the gap b/w piston

and disc through E and away to the trap outlet.

As the condensate approaches steam temperature some of it

flashes to steam as it passes through the gap. Although it is

bled away through hole E it does create an intermediate

pressure over the piston, which effectively positions the main

valve to meet the load.


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IMPULSE TRAP DIAGRAM


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ADVANTAGES- Can handle substantial condensate capacity as compared

to their size.

- Suitable for high pressure applications.

- Good air venturing capabilities.

- Small, compact, easy to install.

DISADVANTAGES- Cannot give a dead shut off and will blow steam on very

low load.

- Easily affected by dirt and plug small clearance b/w piston

and cylinder and of course the control orifice.- Trap will not work against a back pressure which exceeds

40 % of the inlet pressure.


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LABYRINTH TRAPSThis is normal types steam trap. It consists of a series of

baffles which can be adjusted by means of a hand wheel.

Hot condensate passes through the baffles and trapbody is subjected to a drop in pressure and some of it

flashes to steam. A series of baffles slows down the

flow of condensate and prevents the escape oflive steam.


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ADVANTAGES

- Can handle condensate is large capacity as compared to

its size.

- No mechanical failure since there are no moving parts.

DISADVANTAGES- Manual adjustment is required with the variation in either

steam pressure or condensate load of the adjustment is

not done, stream wastage or waterlogging of the steam

space will occur.

Summary of Traps Characteristics


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Summary of Traps CharacteristicsF&T Bucket Disc Bellows Capsule Bimet-

thermo

Bimet

T/T

Discharge modul Cyclic Cyclic Cycl/mod Cyclic Cycl/mod Modul

Air Vent Good Poor Fair Exce lnt Excelnt Excelnt Excelnt

Dirt Handling Good Good Good Fair Fair Good Good

Superheat Poor Poor Excel

nt Good/fair Good Good Good

W/Hammer Poor Poor Excelnt Good/fair G/fair Excelnt Excelnt

Response Exclnt Good Good Good/fair G/fair G/fair G/fair

Fail mode Close Open/

Close

Open Open/

Closed

Open/

Closed

open open

Freezing Yes Yes No No No No No

Position

sensitive

Yes Yes No No No No No

Back PsiSensitive

No No Yes No No No No


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SELECTION OF STEAM TRAPS

Sensitivity to back pressure.

Sensitivity to dirt.

Air venting capability.

Venting non condensable at steam temp.

Responsiveness to changing loads.

Resistance to shocks, vibrations and water.


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SELECTION OF STEAM TRAPS

Predominant failure modes.

Installation versatility.

Resistance to corrosion.

Energy Consumption of steam traps.

Condensate sub cooling.

Ease of maintenance.

Plant standards.


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CHECKING OF STEAM TRAPSThere are following techniques to check the performance.

1- Traps discharging to atmosphere.

2- Test vent.

3- Sight glasses.

4- Temperature difference.

5- Sound.

6- Electronic.


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