POWER PLANT ENGINEERING SESSONAL

Experiment No:02 Course No: ME 404

STUDY OF A BOILER

Khaled Mosharraf Mukut Student ID: 1010046

Department of Mechanical Engineering

Section: A

Date of Performance: 6th October, 2015

Date of Submission: 7th October, 2015

Objectives: To study the different accessories and mounting of a boiler

To study the operations of a boiler

To study the boiler capacities

To study the water treatment operations for boiler

Specifications:

Brand Name: Philipp Loos GmbH ( Packaged Boiler)

Model: 12 D-57629 Norken

Producer Country: Germany

Maximum working pressure: 16 Bar

Type of Burner: Dual Fuel Burner (Natural Gas)

Fuel used: Natural Gas

Schematic Diagram of the Boiler :

Figure: Schematic Diagram of the boiler

Boiler Mounting and accessories:

Mountings:

i) Water level indicator

ii) Pressure gauge

iii) Safety valve

iv) Stop valve

v) Feed valve

vi) Blow down valve

vii) Fusible plug

viii) Steam scrubber

ix) Manhole and handhole covers

Accessories:

i) Superheater

ii) Attemperator

iii) Economiser

iv) Air preheater

v) Feed water heater

vi) Feed pump

vii) Injectors

viii) Draught production equipment

Water Flow Circuit:

Water storage tank

Water treatment plant (Geolite

Chember)

Feed water storage plant

Globe valve Feed water pump Pressure gauge

Return and non-return valve

Feed Check valve and water check

valveBoiler

Fuel Flow Circuit:

Boiler Capacity:

1. Tonnage Rating: The Tonnage Rating is widely used as a datum by shell boiler

manufacturers to give a boiler a rating which shows the amount of steam in kg/h. It

is the amount of water evaporated from feed water at 100 C and formed into dry

and saturated steam at 100 C at normal atmospheric pressure. Each kilogram of

steam would then have received 2257 kJ of heat from the boiler.

Shell boilers are often operated with feed water temperatures lower than 100C.

Consequently the boiler is required to supply enthalpy to bring the water up to

boiling point.

2. KW Rating: Some manufacturers will give a boiler rating in kW. This is not an

evaporation rate, and is subject to the same Tonnage Rating.

To establish the actual evaporation by mass, it is first necessary to know the

temperature of the feed water and the pressure of the steam produced, in order

to establish how much energy is added to each kg of water. The following equation

can then be used to calculate the steam output:

(

) = ()

3600

()

Gas (supply line)

Pressure Gauge

Gas On/Off Valve (Ball

Valve)Gas Filter

Throttle ValveGas Control

Valve ( Solenoid valve)

Push Type Pressure

GaugeGas Regulator

Cross Flow Mixing

ChemberBurner

3. Boiler HP Rating: This unit tends to be used only in the USA, Australia, and New

Zealand. A boiler horsepower is not the commonly accepted 550 ft lbf/s and the

generally accepted conversion factor of 746 Watts = 1 horsepower does

not apply.

In New Zealand, boiler horsepower is a function of the heat transfer area in the

boiler, and a boiler horsepower relates to 17 ft of heating surface, as depicted in

Equation: =1

17 ( 2)

In the USA and Australia the readily accepted definition of a boiler horsepower is

the amount of energy required to evaporate 34.5 lb of water at 212F atmospheric

conditions.

Operations of Air and Fuel Flow for firing a boiler:

Blow out of the exhaust gas.

Checking the water level in the boiler and if level is below the safety

level water is refilled.

Air is blown in by starting blower.

Natural Gas acts as fuel passes through pressure gauge, regulator and

solenoid valve and finally enters into the burner.

Air and gas mixes in proportional limit and produce spark in the electric

spark rod.

Pilot flame is established then full combustion starts.

The fire or hot flue gasses from the burner is channeled through tubes

that are surrounded by the fluid to be heated.

Hydraulic Test of Boiler:

The equipment should have been hydrostatically tested to a minimum of 1 times the

design pressure, in the factory, and copies of the Manufacturer's Data report, signed by

the Authorized Inspector witnessing and evidencing the test forwarded to all

jurisdictional bodies as well as to the Client. However, the complete system, along with all

interconnecting piping, should be hydrostatically tested before start-up to comply with

code requirements and to check for leaks that may have occurred during shipping and

handling. This test should be completed under the supervision of and witnessed by an

Authorized Inspector who should represent the State or municipality having jurisdiction

or the insurance company covering the installation. At the option of this inspector, the

hydrostatic test may be at 1 times the design pressure of the equipment, or at a

pressure slightly less than the setting of the lowest safety valve. The latter test will avoid

the necessity of blanking or gagging of safety valves, removing piping and plugging various

pipe openings, removing controls and gage glasses, etc

Thermal Balance:

Qin=mfuel x HHV

= 0.035 x 0.67 x 58000 kj/sec

= 1360.1 kj/sec

Qsteam = msteam x hsteam

=1600

3600 2780.33 [10C superheat at 5 Bar]

=1235.702 kj/sec

Qfeed= mfeed x hfeed

=1600

3600 120

= 53.33 kj/sec

Qexhaust= mexhaust x Cp x Texhaust

= 21 x 0.035 x 0.67 x 1.005 x 162

= 80.176 kj/sec

Efficiency: =(Qsteam)

= 86.93%

Hardness Test: The presence of Calcium and Magnesium salt in water causes hardness.

The degree of hardness is directly proportional to the quality of these salts present in

water.

The hardness test is required because in general supply water might be acid (in general

acidic). This is not good for the boiler since scale might be formed due to repeated

operation. So treatment is required to make it slightly basic. This can be done either by

titration or by using a PH meter. We have used a PH for the purpose. The PH of the supplied

water is found to be 5.7.

Boiler

Qin=1360.1

kj/sec

Qfeed=

53.33 kj/sec Qsteam= 1235.702

kj/sec

Qexhaust= 80.176

kj/sec

Unaccounted=

3.752 kj/sec

Discussion:

(i) The water treatment system is disconnected when the experiment

was done. We should not do this. Because the acidity in the water

may result in the formation of scales over long term usage. This

significantly reduces the heat transfer coefficient of the boiler

heating surface. So, the geolite cylinder should be connected with

the water flow system.

(ii) Each and every mountings comes in a pair. This is because

mountings are used for the safety purpose. So two of them is

used in case one of them fails.

(iii) The boiler is run at 5 bar pressure which is very low compared

to the rated pressure. This is done to increase the longitivity

of the boiler.

Assignment: Short notes on different boiler and accessories

Mountings:

i) Pressure Gauge:

Figure: Pressure Gauge

A pressure gauge is used to measure the pressure of the steam inside the steam boiler. It

is fixed in front of the steam boiler. The pressure gauges generally used are of Bourden

type.A Bourden pressure gauge, in its simplest form, consists of an elliptical elastic tube

bent into an arc of a circle.This bent up tube is called Bourdens tube.

ii) Pressure Governor and Water Level Regulator:

Thermal energy is transported

to the water inside the boiler body by

means of heating. The water grows

warm and vaporizes, the steam pressure

in the boiler rises. As soon as the

working pressure is attained, the

pressure governors cut of heating.

There upon, when pressure drops for

approx.7% in consequences of the

extraction of steam, the pressure

governor will connect up the furnace

again.

iii) Safety Valve:

These are the devices attached to the

steam chest for preventing explosions

due to excessive internal pressure of

steam.A steam boiler is,usually, provided

with two safety valves.These are

directly placed on the boiler.The

function of a safety valve is to blow off

the steam when the pressure of steam

inside the boiler exceeds the working

pressure.

iv) Water Level Indicator:

Figure: Water Level Indicator

It is an important fitting, which indicates the water level inside the boiler to an observer.

It is a safety device,upon which the correct working of the boiler depends. This fitting

may be seen in front of the boiler, and are generally low in number.

v) Feed Check Valve:

It is a non-return valve, fitted to a screwed spindle to

regulate the lift. Its function is to regulate the supply

of water, which is pumped into the boiler, by the feed

pump. This valve must have its spindle lifted before the

pump is started. It is fitted to the shell slightly below

the normal water level of the boiler.

vi) Blow Off Cock:

This mounting is used for 2 purposes:

a) To empty the boiler whenever required

b) To discharge the mud, scale or sediments which are

accumulated at the bottom of the boiler

vii) Feed Pump:

The feed pump is one of the most important

accessories for a boiler unit. Its function is to take

the feed water from the reservoir and to force it into

the boiler against the steam pressure. The feed pumps

used in this boiler are multistaged centrifugal pump

capable of create high pressure flow to the boiler.

Accessories:

i) Superheater:

A superheater is an important device of a steam

generating unit. Its purpose is to increase the

temperature of saturated steam without raising its

pressure. It is generally an integral part of a boiler, and

is placed in the path of hot flue gases from the furnace.

The heat, given up by these flue gases, is used in

superheating the steam. Such superheaters, which are

installed within the boiler, are known as integral

superheaters.

ii) Economizer: An economizer is a device used to heat feed water by utilizing the

heat in the exhaust flue gases before leaving through the chimney. As the name

indicates, the economizer improves the economy of the steam boiler. It is a

surface heat exchanger where water flows through the cast iron pipes or steel

tubes and flue gases pass around them. There are two general types of

economizer namely (i) independent type and (ii) integral type.

Other Accessories & Mountings:

Flame Sight Hole Burner Gas Pressure Gauge

Control Panel Controller Relay