garioni naval - steam generators

® AVALe a s y l i k e a S u n d a y m o r n i n g …

2technical book

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vaporeGarioni Naval’s technical notebooks have been studied to offer a useful tool for thetechnical offices and for the users of steam, pressurized water and thermal oil.

We obviously do not have the presumption to want to teach how things should bedone. We just want to put at disposal of those people that wish to increase theirknowledge in this sector, or find new information, our experience matured inmany years of study and hard work.

We warmly hope that what is written in these "technical books" will allow everyreader to be able to work with ease and serenity and to avoid, where possible,to fall in errors that others, previously, have unintentionally committed in order toarrive to a certain knowledge level of the Termotecnics sector.This series of notebooks will be published in two editions, one in Italian and theother in English.

We thought, with the purpose to avoid any possible confusion, that it was morepractical and technically more appropriate, not to mix the two languages.

The collection is dedicated to all those people whom have contributed, and thatare still contributing, to GARIONI NAVAL’S development and growth.

If you are interested to receive all the issues, please apply compiling in each partthe enclosed form, by Internet through our web site www.garioninaval.com or bye-mail at [email protected]


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Steam, a traditional but at the same time modern and efficient instrument,is practically irreplaceable regarding petrochemical, chemical, paper,dyeing, pharmaceutical, food, canning, rubber and plastic industries etc.

It is also indispensable in the civil sector for sterilising in hospitals andclinics, it is used as a preference in canteens and laundries and in airconditioning plants (on industrial level, where it is often used for heating).

Again it has a wide and irreplaceable use in generating power usingturbines, pumps and alternators in large heating plants and onboard ships.Wherever there is a need to produce, pump and utilise both thermalenergy and pressure, steam is the ideal solution.

What advantages does it have and which are the reasons for this?Above all, steam can be produced fairly easily and comes from waterwhich, at least in relation to the present or near future global productionneeds of steam, is luckily still available in large quantities and ateconomically advantageous conditions, apart from the fact that in steamplants continuos recycling is applied and recovery can be almost onehundred per cent.

Steam has a very high ponderal heat content which means tubes and userunits having to support a light load, which also means movable equipmentwith excellent exchange coefficient, compact and economic.

Steam circulates naturally without requiring accelerators, temperaturescan be high at quite low pressures which means a relatively safe meansand fairly easy to deal with.

Temperature or pressure regulations can be carried out using simple two-way valves; above all it has the advantage of being extremely “flexible”meaning that it adapts well to later variations and changes, not like otherfluids such as water, superheated water, diathermic oil, etc..

Of course the above mentioned becomes more valid concerning steamplants which have been rationally designed and constructed, above allregarding recovering energy. This automatically leads to the fact that trained technicians with a goodknowledge of the subject should be called in because, although steam isnot so complex as other fluids, a good theoretical preparation andpractical know-how are required.

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gas burners

1 Cutoff cock2 anti-vibration coupling3 gas pressure inlet4 gas filter5 gas pressure regulator6 minimum gas pressure pressure gauge7 class A safety electrovalve8 gas delivery regulator9 air regulation lock10 air ventilator11 safety air pressure gauge12 air pressure inlet13 combustion head14 protection grid

Burners with rated thermal capacity up to 100 kw (860000 kcal/H)





a) supplier charge b) customer charge



GG5


Distance from Ø 1/2” Ø 3/4” Ø 1” Ø 1”1/4 Ø 1”1/2 Ø 2” Ø 2”1/2 Ø 3” Ø 4”meter to boiler 16,6 22,2 27,9 36,6 41,5 53,8 69,6 81,8 104

copper 18x1 copper 22x1 copper 28x1 copper 35x1 copper 42x1

mt Capacity in m3/h(calories burned with P.C.I cal/mc)

2 4 9 16,9 35,5 50 102 203 313 551(32.000) (72.000) (135.000) (284.000) (400.000) (816.000) (1.624.000) (2.504.000) (4.408.000)

4 2,7 6 11,4 24 33,8 69 139 214 390(21.600) (48.000) (91.200) (192.000) (270.000) (552.000) (1.112.000) (1.712.000) (3.120.000)

6 2,1 4,8 9 19 27 54 110 171 318(32.000) (72.000) (72.000) (152.000) (216.000) (432.000) (880.000) (1.368.000) (2.544.000)

8 1,8 3,6 7,7 16 22,8 46,5 94 146 275(14.400) (32.800) (61.600) (128.000) (182.400) (372.000) (752.000) (1.168.000) (2.200.000)

10 1,6 3,6 6,7 14 20 41 82 128 246(12.800) (28.800) (53.600) (112.000) (160.000) (328.000) (656.000) (1.024.000) (1.968.000)

15 1,3 2,8 5,3 11 16 32 65 102 195(10.400) (22.400) (42.400) (88.000) (128.000) (256.000) (520.000) (816.000) (1.560.000)

20 1,1 2,45 4,5 9,6 13,6 27,6 55 86 174(8.800) (19.600) (36.000) (76.800) (108.800) (220.000) (440.000) (688.000) (1.392.000)

25 0,9 2,1 4 8,4 11,9 24 49 76 156(7.200) (16.800) (32.000) (67.200) (95.000) (192.000) (392.000) (608.000) (1.248.000)

30 0,88 1,9 3,6 7,6 10,8 22 44 68 142(7.000) (15.200) (28.800) (60.800) (86.400) (176.000) (352.000) (544.000) (1.136.000)

40 0,74 1,6 3 6,4 9 18 37 58 123(5.900) (12.800) (24.000) (51.000) (72.000) (144.000) (236.000) (368.000) (984.000)

50 0,66 1,4 2,72 5,7 8 16 33 51 110(5.200) (11.200) (21.600) (45.600) (64.000) (128.000) (364.000) (408.000) (880.000)

60 0,59 1,3 2,4 5 7 14 29 46 100(4.700) (10.400) (19.200) (40.000) (56.000) (112.000) (232.000) (368.000) (800.000)

80 0,5 1,1 2 4 6 12 25 39 87(4.000) (8.800) (16.000) (32.000) (48.000) (96.000) (200.000) (312.000) (696.000)

100 0,44 0,98 1,8 3,8 5,4 11 22 34 65(3.500) (7.800) (14.400) (30.400) (43.000) (88.000) (176.000) (272.000) (520.000)

NATURAL GAS PIPES

METHANE GAS delivery in m3/h (density 0.6) for a maximum load loss of 5 mm. Methane 8000 cal/ m3.Calculation of straight sections. Each curve or branch must be calculated as 0.5 m extra.

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copper copper copper copper copper copper12x10 14x12 16x14 18x16 22x20 28x25

Delivery in M3/h(calories burned with P.C.I cal/mc)

5 0,6 1,25 2,2 2,8 4,1 8,4(4.800) (10.000) (17.600) (22.400) (32.800) (67.200)

10 0,41 0,85 1,5 1,9 2,5 5,4(3.280) (6.800) (12.000) (15.200) (20.000) (43.200)

COPPER TUBES

Pressure drops calculation for bignatural gas pipeline

Where:

∆P= Pressure drop in mm.H2OL = pipe length in mQ = gas capacity in Nmc/hD = internal pipe diameter in mm.

Example

Methane line L=100 m, required capacity 6.000.000 Kcal/h

Piping DN 150 Gas capacity 750 Nmc/h

∆P= 1,2 x (750)2 x 100 = 63 mm.c.a.(160,3)5

Example:

Natural gas piping 200 m far from the beginning to the burner.Gas capacity : 750 Nmc/h Gas pressure at the gas train1.500 mm H2O. Admitted gas pressure drop at the end of

piping not more than 150 mm H2O.

D5 = 1,2 x Q2 x L D5 = 1,2 x (750)2 x 200 = 900.000150 ∆P

From the table we find the D5 value closer to the calculated one , thatis 1.058.443 Corresponding to a 6 “ pipe.

∆P = 1,2 x Q2 x LD5

Diameter D5 values

DN25 1” 169

DN32 1” 1/4 656

DN40 1” 1/2 1.386

DN50 2” 4.181

DN65 2” 1/2 15.414

DN80 3” 34.439

DN100 4” 146.253

DN125 5” 408.394

DN150 6” 1.058.443

DN200 8” 3.997.331

DN250 10” 12.298.388

Virtuallength inmeters

GG7

Example: Line pressure: 1.5 ate Tube length: 60 m Calories required: 220,000 Kcal/hThe choice falls on a 3/4” iron or 22 x 1 copper tube

1 lt GPL = 0.5 Kg 1 Kg GPL = 2 lt 1 lt GPL = 2 Kg Kcal/Kg = ~ 11.0001 lt GPL = 0.25 m3 1 Kg GPL = 0.5 m3 1 lt GPL = 4 lt Kcal/m3 = ~ 22.000

Kcal/lt = ~ 5.500

LPG PIPE’S DIMENSIONINGPressure 300 mm H2O

Example: Line pressure: 300 mm H2O. Tube length: 60 m Calories required: 220,000 Kcal/hThe choice falls on a 2 ” iron or 54 x 1.5 copper tube

1 lt GPL = 0.5 Kg 1 Kg GPL = 2 lt 1 lt GPL = 2 Kg Kcal/Kg = ~ 11.0001 lt GPL = 0.25 m3 1 Kg GPL = 0.5 m3 1 lt GPL = 4 lt Kcal/m3 = ~ 22.000

Kcal/lt = ~ 5.500

Initial pressure 1,5 ate 37.1


Kg / h Lt / h Nmc /h55 110 27,5

38,5 77 19,231,8 63,6 15,927,3 54,6 13,624,2 48,4 12,122,2 44,4 11,119,2 38,4 9,617,2 34,4 8,615,8 31,6 7,913,7 27,4 6,812,1 24,2 6

5101520253040506080100

605.000422.000349.000299.000266.000244.000211.000189.000173.000150.000133.000

902.000726.000633.000572.000517.000448.000396.000363.000314.000275.000

1.100.000979.000902.000781.000693.000633.000550.000486.000

Kg / h Lt / h Nmc / h

82 164 4166 132 33

57,7 115 28,851,8 103 2647 94 23,5

40,8 81 20,436,2 72 1833,1 66 16,528,8 57 14,325,7 50 12,5

Distancein M

Efficiency

kcal

Efficiency

kcal

Efficiency

kcal

Iron Ø _ “Copper18 x 11

Iron Ø _ 1”Copper 28 x 1,5

Iron Ø _ “Copper 22 x 1

Capacity CapacityKg / h Lt / h Nmc / h

100 200 5089 178 44,582 164 4171 142 35,563 126 31,5

57,7 115 28,850 100 25

44,2 88,4 22

Capacity

Distancein

M

6 1,5 33.000 3,2 70.400 6,1 134.000 12 264.000 19 418.000 35 770.000

8 1,3 28.000 2,8 61.600 5,2 114.000 10,6 233.000 16,4 360.000 30 660.000

10 1,1 24.000 2,6 57.000 4,7 103.000 9,5 209.000 14,5 319.000 27 594.000

15 0,9 19.800 2,0 44.000 3,8 83.000 7,6 167.000 11,5 253.000 21,5 473.000

20 0,78 17.000 1,7 37.400 3,2 70.000 5,7 140.000 9,8 215.000 18,4 404.000

25 0,69 15.000 1,5 33.000 2,9 63.000 5,4 125.000 8,7 191.000 16,1 354.000

30 0,62 13.600 1,4 30.800 2,6 57.000 5,1 112.000 8 176.000 14,7 323.000

40 0,55 12.000 1,2 26.400 2,2 48.000 4,5 99.000 6,8 149.000 12,5 275.000

50 0,46 10.000 1,0 22.000 2 44.000 3,8 83.000 6,1 134.000 11,1 244.000

60 1,8 39.000 3,5 77.000 5,5 121.000 10 220.000

80 1,5 33.000 3 66.000 4,6 101.000 8,6 189.000

Iron Ø _ “copper14 x 1

Iron Ø _ “copper18 x 1

Iron Ø 1”copper 22 x 1

Iron Ø 1”_copper 35 x 1,5

Iron Ø 1”_copper 42 x 1,5

Iron Ø 2”copper 54 x 1,5

CapacityNmc/h Kcal

CapacityNmc/h Kcal

CapacityNmc/h Kcal

CapacityNmc/h KcalCapacity

Nmc/h KcalCapacityNmc/h Kcal

LIQUID PROPANE GAS TUBES

How they are classified• Forced draft• Induced draft• Balanced draft• Draft with pressurized boiler

NATURAL DRAFT STACKS

In the combustion process the fuel must be fed with asuitable quantity of air. In the old generators the airentered the combustion chamber drawn in by thevacuum created. In order to create this vacuum thecombustion products leaving the boiler must exit intothe atmosphere at a height higher than the boiler itselfthrough a passage called a stack. In this way thestatic pressure in the combustion chamber is equal tothe weight of the atmospheric column present at themouth of the stack (p.s.a.) minus the weight of thecolumn of hot gas contained in the stack (p.s.f) andtherefore less than the one present at the boiler airinlet resulting only from the weight of cold air (p.s.a.).This difference in pressure defined as draft is thetransfer of an external gaseous mass towards theboiler, to the combustion chamber and evacuationstack. This process is known as NATURAL DRAFT.Draft will increase in proportion to the height of thestack and the difference in temperature between thefumes and the air feed.Good efficiency of the system depends on:- high stacks with perfect insulation.- boiler combustion chamber perfectly sealed withoutinfiltration from outside.- high temperature of gases expelled from the stack.The use of re-generators and heat exchangers lowersthe final temperature of hot gases, increases the lossof air load and makes the natural draft effect difficultif not impossible.

FORCED DRAFT STACKS

The use of a fan which pushes the air and combustiongases forward is forced draft.

Forced draftThis is achieved by installing a ventilator at the bottom ofthe stack which extracts the fumes from the boiler andforces them up the stack. The ventilator must haveparticular characteristics as the impeller must supporthigh temperatures and resist corrosion due to acid

GG8


stacks

GG9


components which form according to the type of fuel(sulfur dioxide). A shut-off placed at the bottom of thestack and in the ventilator intake helps to regulate roughlythe delivery of gas. The efficiency of this system ishindered if the combustion chamber is not perfectlysealed towards the external.

Induced draft

This is achieved by installing a fan externally to the stackwhich aspirates a part of the fumes expelled by the boilerand then forces them up the stack itself using anaccelerator which could be an injector.

The part of the fumes blown into the stack by the fanforces the remaining column of hot gasses towards theexit of the stack at high speed while at the same time avacuum is created in the section aspired by the fan thuscreating a forced draft in the combustion chamber.

The efficiency of this system is impaired if the combustionchamber is not perfectly sealed towards the external.

Balanced or compensated draft

This is achieved by using two fans; one which forces thefuel air in the boiler, the other which aspirates thecombustion products and forces them up the stack.

The fan which emits the fuel air into the boiler is called thepusher fan whereas the one that forces the combustionproducts is the suction fan.

In order to achieve a good combustion process the boilermakers adjust the fan head so as to create a slightvacuum in the combustion chamber (5 – 10 mm H2o) thatis the suction fan has a higher head than the pusher fan.

Pressurized boiler draftIt can be said that in recent years the introduction ofpressurized combustion boilers has eliminated themajority of boilers using the systems described above. In fact in order to eliminate all the drawbacks caused bya very precarious draft a pressurized combustion boilerwas designed which incorporates the pusher fan whichimparts the necessary head or pressure on the fuel airaspirated from outside in order to overcome all the loadlosses of the air-fumes-stack circuit.

Advantages: Limited size of boiler, less absorbed electricpower, lower running and maintenance costs.

GGG

GG10



CHOOSING THE SIZE OF THE STACK

Stack draft

This is the possibility the fumes stack has of eliminating allthe combustion products of a boiler without formingcounter pressures. Remember the stacks must be:

• completely airtight with smooth internal surfaces.• appropriately insulated to avoid fumes cooling too much.• the connection between the boiler and the stack must beas short as possible, avoiding bends and long horizontalsections.

T = draft of the stack in mm column of waterh = working height of stack (net of bends and sub

horizontal sections)s.a.w. = specific air weights.f.w. = specific fumes weight corresponds to theaverage temperature taken inside the stack.

Specific weight of air s.a.w. (at a pressure of 760 mmHg)

Specific weight of fumes (at a pressure of 760 mmHg)

Example: external temperature: 5°C; fumes temperature: 180 °C; working height of stack: 10 m

T = 10 x (1.27 – 0.81) = 10 x 0.46 = 4.6 mm

CHOOSING THE SIZE OF STACKS FOR SOLID AND

LIQUID FUELS(antismog law dated 13 July 1966)

Boilers under vacuum with natural draft stack

S = Net surface of fumes stack (cm2)Q = Calories burned by boilerK = Coefficient: for solid fuel = 0.03

for liquid fuel H = Working height of stack. (not to

be confused with height of construction H of stack).

- The resulting sections must be increased by:

50% where lignite is used25% where long - flaming steam coal is used10% for every 500 m above sea level.

- The use of prefabricated elements with commercial crosssections higher than 30% or lower by as much as 10% of thevalue resulting from the calculation formula can be adopted.- The minimum cross section must in no case be less than220 cm2.

- In the case of stacks with cross sections which are notcircular, the ratio between the sides must not be higherthan 1.5.- Triangular shaped cross sections are not admitted.

The workable height h of the stack is calculated from theheight of the construction H less:

0.5 m for each change of direction (C)1 m for each meter in length of the sub horizontal

conduit (L)1 m for each millimeter of load loss of the boiler (p)

As a rule it can be accepted that the load losses on thefumes side for boilers under vacuum are:

2 mm for boilers up to 160,000 Kcal/h3 mm for boilers up to 320,000 Kcal/h4 mm for higher capacity boilers

T = h x (p.s.a - p.s.f.)

Air temperature -5 0 5 10 15 20 25 30°C

p.s.a. (Kg/m3) 1,317 1,293 1,27 1,247 1,226 1,205 1,185 1,165

Exhaust gas 160 180 200 220 240 260 280 300temperature °C

p.s.f. (Kg/m3) 0,848 0,81 0,776 0,774 0,715 0,688 0,664 0,64

S = Qh

GG11


Heght h of stack calculation: h = H – (c x 0.5 + L + P)

Example: 300,000 Kcal boiler (p= 3 mm)Height of construction H = 15 mN° 2 curves (c)Horizontal section: 2 m (L)Fuel: DieselK = 0.024

h = H – (c x 0.5 + L + p)h = 15 – (2 x 0.5 + 2 + 3)h = 15 – (1 + 2 + 3 ) h = 15 – 6 h = 9 m

S = K x Qh

S = 0.024 x 300,000 = 2400 cm29

That is a stack is needed with a net crosssection of : 49x49 cmThe market measurement closest to this is: 50x 50 cmThis example reaffirms the difference betweenheight of construction H (15) and calculatedusable height h (9 m), still a source ofmisunderstanding in the choice of stacks.

Pressurized fuel boilersPressurizing of the burner removes theproblem of load loss on the boiler fumesside (p) therefore height h in calculatingthe stack is:h = H – (c x 0.5 + L)

The K coefficient drops to: 0.008

The cross section of the stacks is: S = 0.008 x Q

9

Example: for the same boiler as before with the samesystem we will have:

h = 15 - (2x0,5+2) h = 15 - (1+2) h = 12 m

S = 0,008 x 300.000 = 693 cm3 (market size12 30x25 cm)

LIQUID FUELTABLE FOR CROSS SECTIONS OF STACKS CONNECTED TO BOILERS

UNDER ASPIRATIONS

GGG

Chimney h igh ca lcu la ted in m Boiler burncapacitySection

LIQUID FUELTABLE FOR CROSS SECTIONS OF STACKS CONNECTED TO PRESSURIZED BOILERS

GG12


Example: Pressurized boiler. Calories burned: 325,000/hStack calculated h height : 7 mThe result is a stack with internal dimensions 30 x 40 cm

Chimney high calculated in m Boiler burncapacity

Section

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For higher consumption a circular cross section must beused:-3.5 cm2 per ogni 1,000 Kcal/h per H < 10 m-2.5 cm2 per ogni 1,000 Kcal/h per H compreso fra 10 e 20 m-2 cm2 per ogni 1,000 Kcal/h per H >20 m

The cross section of a rectangular stack must be at leastthe same as the cross section of the correspondingcylindrical pipe increased by 10%.

GASEOUS FUELS

TABLE FOR CROSS SECTIONS OF STACKS CONNECTED TO PRESSURIZED BOILERS

w w w . g a r i o n i n a v a l . c o m

11 95 10513 123 13514 154 16917 226 24920 314 34524 452 49728 616 67832 804 88436 1.018 1.12040 1.257 1.38344 1.520 1.67248 1.809 1.99052 2.124 2.33656 2.463 2.70960 2.827 3.10964 3.217 3.53968 3.632 3.99572 4.071 4.47876 4.536 4.99080 5.026 5.529

30.000 30.000 40.00040.000 40.000 60.00050.000 60.000 80.00070.000 105.000 125.000

100.000 155.000 180.000140.000 200.000 239.000176.000 245.000 308.000228.000 320.000 402.000283.000 407.000 509.000358.000 503.000 628.000435.000 708.000 760.000512.000 724.000 904.000607.000 849.000 1.062.000704.000 985.000 1.231.000808.000 1.131.000 1.413.000920.000 1.287.000 1.608.000

1.039.000 1.453.000 1.816.0001.164.000 1.628.000 2.035.0001.297.000 1.814.000 2.268.0001.437.000 2.010.000 3.013.000

CHIMNEY HIGH CALCULATED

H < 10 m 10m< H <20m H> 20 m

THERMAL CAPACITYKcal/h

Cylindrical sectionRectangular

or squaresections

Internal diameter

cm

Internal section

cm2

Internal section

cm2

Up to: Up to: Up to:

GG14


Rapid calculation of dimensions of manifolds

D (cm) = Total surface of the outlet pipes +50%0.785

Example: Input: N° 1 3” tubeOutput: N° 1 1/2“ tube

N° 1 2” tubeN° 1 3” tube

sum the sections of the output tubes

1 1/2” = 14.2 cm2

2” = 22.8 cm2

3” = 52.4 cm2

89.4 cm2

Increased by 50% 44.7Total 134.1 cm2

The diameter chosen is the same as or slightly greater thanthe one corresponding to the external dia. in the table.In our case a 5” dia. manifold is chosen with an externaldiameter of 139.7 mm.

Boilers installed in parallel

VR= check valve

Each boiler has to be provided with a steam outlet valve.When two or more boilers have to deliver steam to thesame line, each of one has to be able to workindependently from the others and concerning thedelivery, and concerning the feeding.

If the boiler’s rated pressure are different one to the other,than it is necessary to install safety valves trimmed at thelower pressure. For instance, if two boilers are tested at10 one and at 12 the second, both safety valves have tobe trimmed at 10 bar.

It is also strongly suggested ,above all for boilersproducing more than 1000 kg/h of steam, to install checkvalves on the outlet lines after the steam outlet valve.

Rapid calculation of dimensions of manifolds

D (cm) = 134,1 = 13 cm (130 mm)0.785

Ø pipe DN Ø external mm

Ø internal mm

Sez. area interna cmq

GG15


All boiler’s room have to be realised with:

1. Doors operable from inside to outside

2. To be used only for the boiler’s management. This means that no one but the boiler’s responsible canenter the boiler room. One display panel indicating this rule has to be fitted onthe outside boiler’s room wall.

3. All existing rooms above and under the boiler roomcannot be lived permanently by people with theexception for :

a) Boilers with pressure lower than 10 bar, if the watervolume per M” of heated surface do not exceed 50

b) All steam boilers with pressure below 6 bar

c) All steam boiler with a pressure between 6 and 10bar having the pressure multiplied per the water volume< than 30.000

4. A minimum high of 1.8 m have to be free over thehighest part of the boiler

5. All sewing of the boiler have to be easily accessible

6. Steam accumulators have to be installed (if possible)outside the boiler room

boiler room

P ≤ 10ateWater volume

= < 50 litresm2 surface

P = 6-10 bar PxV ≤ 30.000

w w w . g a r i o n i n a v a l . c o m

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1) Minimum boiler’s room dimensions have to be :

a Minimum 1,5 mt on the boiler’s front side, after theburner.

b) Minimum 0,6/0,8 mt. between the boiler and the wallor between boiler and boiler.

c) Minimum 0,8 mt between the boiler’s back side antthe wall.

2) Minimum 1,8 mt from the boiler top side and the roof.

3) All boiler’s blow down have to be connected to thesewer.

4) Safety valve discharge have to be conveyed outside and separately.

5) All chimneys have to be openable for inspection.

6) Fuel tanks bigger than 300 lt. Are not allowed inside theboiler room.

GG17



1) Manometer2) Safety valve3) Level indicator4) Calibration pressure switch5) Stop pressure switch with manual reset6) Level adjuster7) Safety level adjustment with block8) Feed equipment9) Feed group10) Discharge group

1) MANOMETERThe manometer is an instrument for measuring andindicating the relative internal pressure of the boiler.

Each boiler must be equipped with a manometer with Mpascal, Kgcm2 or bar graduated scale and the range must reach a pressure reading not less than1and a quarter times but not higher than doublethe rated pressure or the calibration setting of the safety devices.

In the case of manometers with unified scales accordingto TAB. UNI 4663, the range may be set based on the

settings indicated inthe table.

The rated pressure on themanometers must beprinted in red.a) The manometer shouldbe equipped with as i p h o ncoil tube, where thesteam, on coming intocontact with themanometer sensor willcondense.

b) A 3-way stop cock must be applied equipped with anappendix.c) With a flat disk dia. 40 mm and 4 mm thick. (control check)

2) SAFETY VALVELe valvole di sicurezza si distinguono in 3 categorie:Safety valves fall into 3 categories:a) Qualified valvesare those valves where the assigned value of thedischarge coefficient K, has been controlled under testconditions before representatives of a body.

b) Qualified valves with tested lift upare those valves where theassigned value of thedischarge coefficient K, hasbeen controlled simply bychecking the action of the stopplug.

c) Non qualified or ordinaryvalvesare those which have notundergone testing and forwhich the value of thedischarge coefficient has beenset at 0.05 at random (verypenalizing).

control, calibration, protection,feed and safety equipments

Absolute pressure (kg/cm) Pressure gauge scale (kg/cm)

GG18


Each steam boiler must be equipped with at least 2 safetydisk valves, each of which is able and armed so as todischarge the steam when the maximum workingpressure has been reached.

Pressure calibration of safety valves =rated boiler pressure. (Kg/cm2)

Safety valves discharge capacity =maximum production of steam of the boiler at continualload (Kg/h) divided between the two valves.

Example: Steam boiler. rated pressure: 12Kg/cm2.

steam capacity: 4,000 Kg/h

Two safety valves having the following characteristics should bechosen:- calibration pressure = 12 Kg/cm2

- discharge capacity ≥ 2,000 Kg/h

Safety valves discharge tube installed on steam boilers biggerthan 1000 Kg/h have to be piped outdoor.

Recommendations for realising discharge pipes:

a) We recommend installing the discharge tube with adiameter slightly larger than the diameter of the exitflange of the safety valve.

DE = inlet diameterDU = outlet diameter

b) The discharge tube must be realised so as to avoid theformation of condensation.We strongly advise against using the discharge outletplaced in the valve body as a discharge for condensation

USUAL DIMENSIONS OF SAFETY VALVES USED BY MANUFACTURERS

DE DU

25 4032 5040 6550 8065 10080 125

100 150

DrainageThe shorter

possible

To secure strongly at the wall thedischarging pipes of the safety valves

GG19



c) The discharge tube must be well anchored andsupported so that the forces created by the sudden andviolent discharge of steam do not unload on the safetyvalve. d) If several safety valves are connected to one discharge tube this must have an internal cross section equal to thesum of the exit cross sections of the valves.Example:

Total cross-section of the 2 valves 22.8 + 22.8 = 45.6 cm2.

A 3” tube with an internal cross section of 52.4 cm2

should be used.

Safety valves calculation of delivery ofsaturated water vapour (D.M. 21.05.74)

Q = valve discharge capacity (Kg/h)A = passage area (cm2)0.9 = reduction coefficientK1 = discharge coefficient113.8 = numeric constantC = expansion coefficientP1 = discharge pressure + 10% +1,013 (Kg/cm2)V1 = steam specific volume at P1 (m2/kg)

In the case of ordinary type safety valves 0.9 a K1 =0.05 is assumedIn the case of qualified type valves the value used forthe discharge coefficient is the one calculated duringthe qualification tests by ISPESL which usually varies,depending on the type of valve, from 0.2 to 0.9 (K1).

Example: steam boiler. Find the dimensions of thesafety valve at the capacity of 3000 Kg/h with adischarge pressure of 12 ate.

Q = 3000 Kg/hK1 = 0.66C = 0.639P1 = 14.21 Kg/cm3V1 = 0.141 m3/Kg

The choice falls on a safety valve with a passagecross-section equal to or slightly greater than thevalue found. In the manufacturer’s catalogue therecould be a valve with useful area of 8 cm2, with32 mm dia. passage and DN40 input flangedconnections x DN65 output.

3) LEVEL INDICATOR

Each boiler must have not less than 2 water levelindicator devices, one of which must be made of glass.The other indicator may be made up of 2 test valves. The visible height of the indicator level must nit be lessthan 150 mm, of which not more than 40 mm must bebelow the minimum level of the boiler.There must always be a plate bearing the wording“MINIMUM LEVEL”

4) CALIBRATION PRESSURE SWITCH

Equipment needed to check the boiler pressure andkeep it within the set maximum and minimumpressure limits. This role is achieved using pressureswitches equipped with differentiated calibration ofoperating levels.

Q = A x 0,9 x K1 x 113,8 x C x P1V1

A = Q0,9 x K1 x 113,8 x C x P1

V1

A = 3000 = 6,9 cmq0,9 x 0,66 x 113,8 x 0,639 x 14,21

0,141

GG20


R = adjustment knobpressure valueD = adjustment knobdifferential value

Example: boiler with rated pressure of 12 baroperating pressure: 9 barcontrol level of pressure switch : 9 bardifferentiated level set: 1 bar less

This means that when the pressure reaches 9 bar thepressure switch will switch off the burner and will switchit on again when the pressure drops to 8 bar (9-1).As a rule for fuel oil and diesel where certain capacities areexceeded(over 300,000 cal/h) the burner is equipped with2 nozzles (2 phases) where each one guarantees half of thefuel delivery. In this case there will be two pressure switches,set at different pressures and each one connected to onephase of the burner.

PSH= on-off regulation pressure switch

PSL= first step regulation pressure switchPSH= second step regulation pressure switch

5) STOP PRESSURE SWITCH WITH MANUAL RESET

Equipment having a safety role which intervenes in thecase of breakdown of control pressure switch. It is set ata higher pressure than the control pressure switch butlower than the rated pressure of the boiler.

This pressure switch operates by opening the boilerpower electric circuit. A device holds the electric contactpermanently blocked in the open position. The electricpower circuit can only be reset manually by the operatoronce the cause for the breakdown has been removed.

6) LEVEL ADJUSTER (LEVEL GAUGE)

Automatic equipment for maintaining the water level in theboiler within a set range. The regulator controls the start of thefeed pump when the level in the boiler reaches the setminimum and stops it when the maximum level set has beenreached. Float regulating system. Sensor made up of a floatwhich moves with the level of the water in the boiler. The floatis connected to a rod movement which moves mercury filledspheres which open or close the electric contacts.

7) SAFETY LEVEL REGULATOR WITH STOP

Level regulator with electrodes. Equipment which takesadvantage of the electric conductivity of water, made upof three electrodes or sensors. When sensors 1 and 2 areout of the water the feed pump is actuated thus coveringfirst sensor 2 and then sensor 1. At this point the pumpstops. If for some reason the level drops below sensor 3the burner is automatically switched off. In the electricsequence apparatus the stop control is actuated whichwill not allow the burner to start unless it is reset manuallyafter the cause has been removed.

Pressare 12bar

Controlpanel

GG21


8) FEED WATER PUMP (1)

Every steam boiler needs one or two feed water pumps (depending from the regionallaw)

Example Fire tube steam boiler. Rated pressure 8 bar . Maximum steam production 1000 Kg/h.Piping pressure drop 1,3 bar Pump head 0,5 bar

Pump dimensioning: Head = ( 8+1,3+0,5) + 5% = 10,3 bar (103 m.)We may so assume that the head is within 1,25 and 1,3 the rated pressure, while the capacity have to be the 200 % ofthe steam production.

Feed water pump capacity

Maximum boiler’s steam production

Feed water pump capacity in %

Fire tube steam boilers Natural circulation water tube boilers

Fire tube

steam boilers

up to 1 T/h 200% 200%

more than 1 T/h up to 5 T/h 160% 130%



up to 1 T/h 100% 110%

more than 1 T/h 100% 100%Natural circulation water tube boilers

GG22


9) FEED WATER GROUPIt is composed from : pump, check valve and water valve

10) BLOW DOWNIt is used to blow down totally or partially the boiler. It is composed by one special fast blow down valve and from a on-off valve

on-off valvecheck valve

water pump

on-off valvefast blow down valve

GG23


steam usePHYSICAL CHARACTERISTIC OF SATURATED STEAM

Heating systems is using the latent heat, for example:

Usually, in the steam heating process, the most important is the latent heat Comparing the latent heat of the steam at 1 and at 10 bar we have:Latent heat at 1 bar 526 kcal/hLatent heat at 10 bar 478 kcal/hThis means that 1 Kg of steam at 1 ate give 48 Kcal more than the one could give at 10 bar.

Sensibile heatKcal/kgSpecific volumeTemperaturePressure

Sensibile heat 186,8 KCAL/KG +

Heat exchanger

Given478,0 KCAL/KG

Condensate capacity 1000 kg /h

Total heat 186,8 KCAL/KGSensible heat 186,8 KCAL/KG

Condensate, when at atmospheric pressure ( 0 bar) will be at 100°C and willproduce 86;8 Kcal/h as re-steaming

Latent heatKcal/kg

Total heatKcal/kg

Steam production 1000 kg/h 10ate

Latent heat 478 KCAL/KG +Total heat 186,8 KCAL/KG +


GG24

Considering two installations, one at 10 ate, and one at1 ate, both with condensate discharged into atmosphereand not reused

It is clear theta efficiency at 1 ate is 9% higher than at10 ate.

If the same example is recovering and using allcondensate at 100°C with a heat content of 100 kcal.

In this case the higher efficiency is the one of 10ate of 11 %.

Practical examples

Unit heater

Q= WL

Q = steam capacity kg/hW = required heat from the air heaterL = used steam latent heat

Exemple: air heater of the capacity of 25.000 kcal/husing 3 bar steam latent heat is 509kcal/kg

Air heaters

Q= V x ∆t x CsL

Q = steam capacity kg/hV = volume of air to be heated Nm_/h∆t = temperature increase °C (t2 – t1)Cs = air specific heat (0,3 kcal/m_/°CL = steam latent heat kcal/kg

Exemple: air heater with air capacity of 6000 Nmc/h,inlet temperature T1 15°C, outlet temperature T2 65°C.Steam available 5bar (498 kcal/kg)

Q = 6000 x (65 – 15) x 0,3 = 180 kg/h 498

Heat exchangers

If Kcal are already known we will have:

Q = WL

Q = steam capacity kg/hW = heat required by the heat exchanger kcal/hL = latent heat of the used steam

Exemple: heat exchanger of the capacity of 150.000kcal/h using steam at 2 bar (517/kcal/kg)

Q = 150.000 = 290 kg/h of steam at 3 bar517

R = efficiency of the utility = Utilised heat

Total given heat

10 ate Steam R =478

= 72%664

1 ate steam R =526

= 81%646

10 bar steam R =478

= 85%664-100

1 bar steam R =526

= 81%646-100

Condensate

Steam

Steam

Condensate

Condensate

Steam

GG25


When the yield data or calories required are notavailable, but the characteristics of the fluid such as:delivery, temperature at input and in output and kind offluid plus its specific heat, are known or can be had, thefollowing formula can be used:

Q = Cs x F x ∆tL

Q = Steam consumed (Kg/h)Cs = Specific heat of the fluid too be heated

(water = 1. Oil = 0.5)F = Delivery of fluid to be heated (Kg/h)∆t = Increase in temperature of fluid to be heated.

( t 2 – t1) (°C)

L = Latent heat of the steam used (cal/Kg)

Example: Water to be heated Cs = 1. Water delivery = 4,000 l/h. Temperature input water (t1) = 15°CTemperature water in output (t 2) = 60°C. ∆t = t 2 – t1 = 45°CSteam at a pressure of 4 bar is used whose latent heat is503 cal/Kg.

Q = 1 x 4000 x 45 = 357 kg/h 503

Example: Fuel oil Cs = 0.5. Oil delivery: 4,000 Kg/h. Temperature input oil = 45° (t1)Temperature oil in output 90°C (t 2). Dt = t 2 – t1 = 45°CSteam at a pressure of 4 bar is used whose latent heat is503 cal/Kg.

Q = 0,5 x 4000 x 45 = 178 kg/h 503

Calculation coil surface for rapid exchanger

S =Q

K x ∆tm

S = coil surface m2

Q = calories kcal/hK = transmission coefficient kcal/m2/°C∆tm = Average logarithmic difference of temperature

between the two fluids °C

∆tm = A trustworthy rough calculation (without havingto consult the log. Tables) and with steam up to 6 ate is:

t1 – t3 = t5 t2 – t4 = t6

∆tm =t5 + t6

2Example: Calories required: 100,000 cal/h, copper coil, modularadjustment steam available: 3 ate t1 = 143°C.Condense temperature t 2 = 100°CSteam vaporisation heat: 3 ate = 510 Kcal/KgWater temperature t3 = 60°CWater temperature t4 = 70°C

∆tm =(143 – 70) + (100 –80) = 46,5°C

2

S=100.000

= 1,79m2

1200 x 46,5

If the coil is manufactured in a copper pipe Ø 16x1which surface is of 0,05 m_/m linear, we will need(formula Metri = Metres)

Metres =1,79

= 35,8 m0,05

Steam

Condensate

Steam

Condensate

VALUES OF K - Coil’s transmission coefficient

From

Steam

ThroughSteel

Cooper

K900

1200

To

Water

GG26


Surface treatment tanks

Usually the tank heat requirement is calculated then thechoice of size of coil is made. Calculation of heatrequirement with initial heating starting from cold.The heat required is given taking into consideration thefollowing items:

1) Heat needed to raise the temperature of the liquid fromthe starting temperature to working temp. Q1

2) Compensation for heat loss from walls to the environment Q2

3) Compensation for heat loss from surface of the liquid to the environment. Q3

4) Heat absorption of treated materials immersed in the tank. Q4

Raising of temperature of the liquid Q1

Q1=Cs x P x ∆t

H

P = Weight of liquid (Kg or l)Cs = Specific heat of liquid (for water = 1)Q1 = P x Cs x Dt

∆t = Thermal head of liquid between starting and final temperature (°C)

H = Pre-heating time (usually 3 – 4 hours)

Example: 10,200 l water t1 = 10°Ct2 = 60°C Dt = 50°CPreheating time = 3 hours

Q1 =1 x 10200 x 10 170.000 kcal/h

3

Heat loss from walls (Q2)

Example:Hot water contained in the tank = 60°CEnvironment temperature Ta = 10°CLoss of calories = 527 kcal/m2

Vertical wall surfaces in contact with water:2 (3 x 1,7) + 2 (2 x 1,7) = 17 m2 x 527 =8.959 kcal/hBottom surface:2 x 3 = 6 m2 x 527 x 0,65 = 2.055 kcal/h

Q2 = 11.014 kcal/h

Loss of heat from liquid surface (Q2)

Steam

Condensate

Temperature of thesurrounding

environment °C

Water mark superficial temperature

40°C 60°C 80°C 100°C

- 15°C 590 851 1169 15290°C 408 654 944 1280

10°C 294 527 794 110720°C 189 408 654 94440°C / 189 408 654

For horizontal even surfaces dispersingtowards the top, multiply per 1,3.

For horizontal surfaces dispersing towardsthe bottom, multiply per 0,65.

If the surfaces are insulated, the table’sdata must be reduced of 25%.

WATER SURFACE TEMPERATURE IN °C

air sp

eed V

=1m/s

V= 2m/s

V= 3m/s

V= 4m/s

MOVING AIR

Inserire immagine vedi Ita

GG27


Example:With a surface temperature of the uncovered watersurface of 60°C and the surrounding air still we have aloss of 3,000 cal/h/m2.With the same surface temperature but with the airmoving at 4 m/sec (aspiration hood) the loss rises to7500 cal/h/m2.The tank evaporating surface is 6 m_ (3 x 2); with anoverhanging exhauster hood we will have a dispersionof 6 m_ x 7.500 = 45.000 Kcal/h

Therefore Q3 = 6 x 7500 = 45.000 kcal/h

Heat absorbed by the material treated (Q3)

It is usually accepted that the final temperature of thematerial reaches the temperature of the liquid it isimmersed in.Q4 = P x Cs x ∆tP = Weight of material (Kg)Cs = Specific heat of material (kcal/kg/°C)∆t = Increase in temperature of the material

to be heated (°C)

Example:Block of steel weighing 200 Kg, the specific heat of whichis 0.12, to be raised to 10°C. Dt = 50°C

Q4 = 200 x 0,12 x 50 = 1.200 kcal/h

Calculation of the surface of the heating coil Q5

Once the maximum heat required has been set, which inour case is: Q1 + Q2 + Q3 + Q4 = Q5

The coil surface can be calculated using the followingformula:

S=Q5

K ( Ts – TL)

Q5 = Total calories needed (cal/h)

K = Overall heat transmission coefficient between steam – tube wall – heating liquid. (cal/h/m2/°C)

Ts = Average temperature of heating surfaces (°C)TL = Average temperature of heating liquid (°C)S = Coil exchange surface (M2)

PRACTICAL VALUES OF THE K TRANSMISSIONCOEFFICIENT BETWEEN FLUIDS THROUGH METALS

(not countercurrent)

Making reference to the above examples we will have:Q5 = 170.000 + 11.014 + 45.000 + 1.200 =227.214 kcal/h

Considering:average water temperature 60°Csteam temperature at 4 ate = 152°Csteel coil K = 900

S=227.214

2,7m2

900 ( 152 – 60)

Using a steel pipe Ø 1”1/4, with a linear externalsurface of 0,152m_/m, we have to use 2,7/0,152 =18 linear meters to create the coil.

With steam at 4 ate which its latent heat is 503kcal/kg, in order to satisfy these needs, theconsumption will be as follow:

Q=227.214

452 kg/h503

This value refers to a pressure start-up which pre-heating is 3 hours, the maintenance will reduceabout 1/4 of maximum value.

FROM BY AT K

Lead 250

Stainless inox 580

Steam Cast iron Water 780

Iron 900

Copper 1000

GG28


STEAM LINES DIMENSIONING DIAGRAM

Example:Steam pressure 3,5 bar. Capacity 1000 kg/hFixed velocity 25 m/sDiameter pipe : 80 mm

STEAM S

P E ED

m/ s e

c

PIP

E D

IAM

ETER

in

mm

STEA

M CAPA

CITY

Kg

/h

STEAM TEMPERATURE IN °C

RELATIVE STEAM PRESSURE in Kg/cm2

GG29


STEAM LINES DIMENSIONING DIAGRAM

Example:Steam pressure 3,5 bar. Capacity 1000 kg/hDiameter pipe : 80 mmPressure drop: 0,3 bar on length: 100 m

STEA

M C

APA

CIT

Y Kg

/h

INTE

RNA

L PI

PE D

IAM

ETER

in m

m

LOSS

OF

HEA

D IN

KG

/CM

PER

100

MET

ERS

GG30


Steam delivery through holes or nozzles

Example: Steam pipes with 11 bar pressare and hole or nozzle of5 mm diameter. Steam capacity for each hole (nozzle) =80 Kg/h.

STEAM DELIVERY THROUGH HOLES OR NOZZLES (capacity in kg/h)

Example: DN 50 (2”) tube. At a pressure of 4 bar, with speed of 25 min/sec, delivery will be 450 Kg/h

Stea

m c

apac

ity i

n Kg

/h

Steam pressure in bar (Kg/cm2)

FORO ø 12,5 m

GG


breakdowns, steam leaks

boiler bursts

Reference is made to the classical event of a boilerbursting due to excess pressure, breakdowns, defects inconstruction or errors in running (e.g. lack of water)which have caused the formation of areas with lessresistance resulting in the sheet metal bursting and theinstant release of enormous quantities of potential energycontained in the boiler.

With saturated steam each pressure corresponds to acertain temperature of the water. In an open container water usually boils at 100 °Cwhereas in a closed container (boiler) it boils at thetemperature which corresponds to the pressure reached.

At 1 atmosphere water boils at 120°CAt 5 atmospheres water boils at 158 °CAt 10 atmospheres water boils at 183°C

In a boiler which produces steam at 10 ate there is amass of water at a temperature of 183°C.

If for the above reasons a large hole forms in the boiler,the pressure would drop instantly from 10 ate toatmospheric pressure. At the same time the temperature of the water would dropfrom 183°C to 100°C, the boiling temperature of waterat atmospheric pressure.

In this way 183 –100 = 83 calories for each kilogram ofwater held in the boiler would be released; these calorieswould cause part of the water itself to evaporate.

As in order to evaporate one Kg of water at 100°C, 539calories (639-100) are needed, with 83 calories 0.154kilograms (83:539) will evaporate, that is to say about150 Kg of steam for each m3 of water contained in theboiler will be produced.

As a kilogram of steam at atmospheric pressure occupiesthe volume of about 1725 litres, each litre of water (equalto 1 Kg) which evaporates from the boiler on the boilerbursting immediately tends to occupy the volume of 1725litres.

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TELEPHONE FAX

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SPEED m/s

CA

PAC

ITIE

S m

c/h

water

compressed air

steam

thermal oil



GAS BURNERS “ 4

NATURAL GAS PIPES “ 5COPPER TUBES “ 6PRESSURE DROPS CALCULATION FOR BIG NATURAL GAS PIPELINE “ 6LIQUID PROPANE GAS TUBES “ 7LPG PIPE’S DIMENSIONING “ 7

STACKS “ 8HOW THEY ARE CLASSIFIED “ 8NATURAL DRAFT STACKS “ 8FORCED DRAFT STACKS “ 8CHOOSING THE SIZE OF THE STACK “ 10CHOOSING THE SIZE OF THE STACK FOR SOLID AND LIQUID FUELS “ 10LIQUID FUEL - TABLES “ 11/13BOILERS INSTALLED IN PARALLEL “ 14

BOILER ROOM “ 15

CONTROL,CALIBRATION, PROTECTION, FEED AND SAFETY EQUIPMENTS “ 17MANOMETER “ 17SAFEETY VALVE “ 17LEVEL INDICATOR “ 19CALIBRATION PRESSURE SWITCH “ 19STOP PRESSURE SWITCH WITH MANUAL RESET “ 20LEVEL ADJUSTER (LEVEL GAUGE) “ 20SAFETY LEVEL REGULATOR WITH STOP “ 20FEED WATER PUMP “ 21FEED WATER GROUP “ 22BLOW DOWN “ 22

STEAM USE “ 23PHISICAL CHARACTERISTICS OF SATURATED STEAM “ 23PRATICAL EXAMPLES “ 24/27STEAM LINES DIMENSIONING DIAGRAM “ 28/29STEAM DELIVERY THROUGH HOLES OR NOZZLES “ 30

BREAKDOWNS – STEAM LEAKS “ 31

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