DESIGN IV MACHINERY SYSTEM

DEPARTMENT OF MARINE ENGINEERING

Calculation and Specification of

Compressed Air System
Doc.No. 09 - 42 20 DN002 - CA

Prepared by Approved by
Rev. Date Remark A.A.B. Dinariyana D. P., S.T.,
Sean Chen Gyarino
MES., Ph.D.
 DESIGN IV MACHINERY SYSTEM
DEPARTMENT OF MARINE ENGINEERING

ATTACHMENT

Calculation and Specification of

Compressed Air System
Attachment of Doc.No. 09 - 42 20 DN002 - CA
 Doc. No. 09 - 42 20 DN002 - CA
Calculation and Specification of
Compressed Air System Rev. No. 0
Page

I. INTRODUCTION
In Wartsila 26 Project Guide, the compressed air system is explained by this
statement :

Compressed air is used to start engines and to provide actuating energy for safety
and control devices. The use of starting air for other purposes is limited by the
classification regulations. To ensure the functionality of the components in the
compressed air system, the compressed air has to be free from solid particles and
oil.

II. OBJECTIVES
The objective of this chapter are :
a) Knowing the components and function of the Compressed Air System
b) Knowing the specification of pumps ad equipment used.

III. REFERENCES
a) ClassNK Part D, Chapter 13, Piping System
b) Project Guide Wartsila 26

IV. LIST OF ABBREVIATIONS

No Abbreviations Explanation
1 kPa Kilo Pascal
2 t Time
3 mm Milimeter
4 h Hour
5 kW Kilowatt
6 RPM Radian per Minute
7 v Velocity
8 Q Capacity
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Compressed Air System Rev. No. 0
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V. SYSTEM DESCRIPTION

Compressed air is used to start engines and to provide actuating energy for safety
and control devices. The use of starting air for other purposes is limited by the
classification regulations.
To ensure the functionality of the components in the compressed air system, the
compressed air has to be free from solid particles and oil.
The design of the starting air system is partly determined by classification
regulations. Most classification societies require that the total capacity is divided
into two equally sized starting air receivers and starting air compressors. The
requirements concerning multiple engine installations can be subject to special
consideration by the classification society.

a.    Starting air compressor unit (3N02)

At least two starting air compressors must be installed. It is recommended that the
compressors are capable of filling the starting air vessel from minimum (1.8 MPa)
to maximum pressure in 15...30 minutes. For exact determination of the minimum
capacity, the rules of the classification societies must be followed.
b.    Starting air vessel (3T01)
The starting air vessels should be dimensioned for a nominal pressure of 3 MPa. The
number and the capacity of the air vessels for propulsion engines depend on the
requirements of the classification societies and the type of installation. It is recommended to
use a minimum air pressure of 1.8 MPa, when calculating the required volume of the
vessels. The starting air vessels are to be equipped with at least a manual valve for
condensate drain. If the air vessels are mounted horizontally, there must be an inclination of
3...5° towards the drain valve to ensure efficient draining.
c.    Non Return valve, straight, screw down
NRV used at high pressure and direction of flow in one direction.
d.    Globe Valve
Function : Globe Valve are used to open and close the flow at relatively high
pressures due to be passed by the high-pressure air.
e.    Safety Valve
Function : Safety Valve are used maintain the pressure at the nominal and as
safety device if the air receiver over pressure.
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f.     Air filter, starting air inlet (3F02)
Condense formation after the water separator (between starting air compressor
and starting air vessels) create and loosen abrasive rust from the piping, fittings
and receivers. Therefore it is recommended to install a filter before the starting air
inlet on the engine to prevent particles to enter the starting air equipment.
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VI. DESIGN REQUIREMENTS
Key
No Reference Parameter Design
Equipment
Air compressors are to be so arranged that entry of
oil into inlet air may be minimized as practicable.
Each air compressor is to be provided with a relief
valve to prevent the pressure from rising more than
Class NK Part
10％ above its maximum working pressure in
D Chapter
cylinders.
13.13.1
Arrangment Where water jackets of air coolers might be subject
of Air to dangerous excessive pressure due to leakage of
Compresse compressed air into them, suitable pressure relief
1 r and arrangement is to be provided for the water jackets.
Pressure Where the main propulsion machinery is designed
Relief for starting by compressed air, two or more starting
System air compressors are to be provided and arranged so
Class NK Part as to be able to charge each air reservoir.
D Chapter The total capacity of air compessor is to be
13.13.3 sufficient to supply air in the air reservoirs from
atmospheric pressure to the pressure requires for
the consecutive starts prescribed in 2.5.3-2 within
one hour
Starting air pipes from the air reservoirs to the main
propulsion machinery or auxiliary engines are to be
entirely separate from the compressor discharge
system prescribed in -2.
The prime movers driving the emergency air
Emergency
Class NK Part compessor are to be capable of starting without
Air
2 D Chapter compressed air.
Compresso The capacity of the emergency air compressor is to
13.13.4
rs be sufficient to start the prime movers of the air
compressor prescribed in 13.13.3. For this
purpose, a small air reservoir for emergency air
compressor may be provided.
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Drainage system is to be provided to compressed
air piping containing drain inside the pipes.
All discharging pipes to starting air reservoirs are to
Class NK Part be led directly from starting air compressors.
3 Piping D Chapter Starting air pipes from the air reservoirs to the main
13.13.5 propulsion machinery or auxillary engines are to be
entirely separate from the compressore discharge
system.

To ensure the functionality of the components in

Compresse
Wartsilla 26 the compressed air system, the compressed air has
4 d Air
Project Guide to be free from solid particles and oil.
System

The engine is started with a pneumatic starting

motor operating at a nomnal preasure of 3 MPa (30
bar).
Internal Each HP fuel pump is provided with a pneumatic
Compresse Wartsilla 26 stop cyclinder which pushes the fuel injection
5
d Air Project Guide pumps to zero - delivery when activated. The stop
System selenoid valve which admits air to the pneumatic
stop cylinders will be activated by the engine safety
system, also in case of an overspeed or an
emergency stop command.
The design of the starting air system is partly
determined by classification regulations. Most
classification societies require that the total
capacity is divided into two equally sized starting air
receivers and starting air compressors. The
External requirements concerning multiple engine
Compresse Wartsilla 26 installations can be subject to special consideration
6
d Air Project Guide by the classification society.
System The starting air pipes should always be slightly
inclined and equipped with manual or automatic
draining at the lowest points.
Instrument air to safety and control devices must
be treated in an air dryer.
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At least two starting air compressors must be
installed. It is recommended that the compressors
are capable of filling the starting air vessel from
Starting Air
Wartsilla 26 minimum (1.8 MPa) to maximum pressure in
7 Compresso
Project Guide 15...30 minutes.For exact determination of the
r
minimum capacity,the rules of the classification
societies must be followed.

The starting air vessels should be dimensioned for

a nominal pressure of 3 MPa.
It is recommended to use a minimum air pressure
of 1.8 MPa, when calculating the required volume
of the vessels.
Starting Air The starting air vessels are to be equipped with at
Wartsilla 26 least a manual valve for condensate drain. If the air
8 Compresso
Project Guide vessels are mounted horizontally, there must be an
r
inclination of 3...5° towards the drain valve to
ensure efficient draining.
The required total starting air vessel volume can be
calculated using the formula: 𝑝 × 𝑉 ×𝑛
𝑉 =
𝑝 − 𝑝
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VII. SUMMARY OF CALCULATION

a. Pipe For Compress Air System

This system are designed to use JIS 3454, Carbon Steel Pipe :
NPS = 40A
Inside diameter (dm) = 49.6 mm 1.95 inch
thickness = 3.7 mm 0.15 inch
Outside diameter = 42.7 mm 1.68 inch

b. Air Receiver
BRAND = Mellcon SL 3
Volume = 500 liter
Height = 1550 mm
Diameter = 600 mm
Max Pressure = 30 bar

b. Compressor Selection
BRAND = Hatlapa RPM = 1150
Type = L9 Frequency = 50 Hz
Capacity = 6.6 m3/h Phase = 3
Power = = 1.7 kW Voltage = 380 V

VIII. DETAIL OF CALCULATION

See attachment of Doc.No. 09 - 42 20 DN002 - CA
IX. SPESIFICATION OF EQUPMENTS
See attachment of Doc.No. 09 - 42 20 DN002 - CA
X. DRAWING OF SYSTEMS
See attachment of Doc.No. 09 - 42 20 DN002 - CA
 Doc. No. 09 - 42 20 DN002 - CA
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Rev. No. 0
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VIII. DETAIL CALCULATION

a. Principal Dimension of Ship

● Lpp = 112.94 m ● H = 10.82 m
● Lwl = 116.33 m ● Cb = 0.7648
● T = 8.4477 m ● Vs= 12 knot
● B = 20.291 m
b. Calculation Capacity of Starting Air Vessel
The Capacity of Starting Air Vessel is to be calculated according to the following
formula:
𝑃 𝑥𝑉 𝑥𝑛 (Project Guide Wartsila 26, 8-5,
𝑉 =
𝑃 − 𝑃 Page 133)
Where,

● PE = Normal Barometric Pressure (NTP condition) (MPa)

= 0.1 MPa
(Project Guide Wartsila 26)
3
● VE = Air Consumption per starts (Nm )
3
= 1.8 Nm
(Project Guide Wartsila 26)
● n = Required number of starts
= 6 Non - Reversible

● PRmax = Maximum starting air pressure (MPa)

= 3 MPa
(Project Guide Wartsila 26, 8-6, Page 134)
● PRmin = Minimum starting air pressure (MPa)
= 1.8 MPa
(Project Guide Wartsila 26, 8-6, Page 134)

So, Capacity of Starting Air Vessel is:

VR = 0.1 x 1.8 x 6
3-1.8
3 The total vessel volume shall be
= 0.90 m
3
devided into at least two equally
= 0.45 m
sized starting air vessels.
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Calculation and Specification of
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The estimation dimension of starting air vessel based on Wartsila 26 is:

So, based on calculation the sepesification of starting air vessel choosen is:
Starting Air Vessel Dimension
Merk Mellcon SL 3 Height 1550 mm
Type Vertical Diameter 600 mm
Volume 500 Liter
Max Press. 30 Bar
c. Calculation Capacity of Compressor
At least two starting air compressors must be installed. It is recommended that the
compressors are capable of filling the starting air vessel from minimum (1.8 MPa) to
maximum pressure in 15...30 minutes. For exact determination of the minimum
capacity, the rules of the classification societies must be followed.
The formula is:
𝑉
𝑄 =
𝑡
Where,
● V = Volume of Starting Air Vessel
= 0.90 m3
● t = 15 Minutes
= 0.25 Hour
So, The Capacity of Compressor is:
Q = 0.9
0.25
= 3.60 m3
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So, The Specification of Compressor choosen is:

Compressor Spesification Dimension
Merk Hatlapa Length 820 mm
Type L9 Widht 540 mm
3
Capacity 6.6 m /h Height 540 mm
RPM 1150 RPM Weight 120 kg
Power 1.7 kW
d. Calculation Diameter of Pipe
The pipe diameter of compressed air system is based on Project Guide Wartsila
32.The Diameter based on project guide is:
Type of Engine Nominal (Technical Data on Project Guide
8L26 DN40 Wartsila 26, Page 132)

So, The Specification of each pipe based JIS Standard is:

Compressed Air System Pipe
Type JIS G3454
Nominal size 40A
Schedule 40
Outside Diamter 42.7 mm
Thickness 3.7 mm
Inside Diameter 49.6 mm
 Doc. No. 09 - 42 20 DN002 - CA
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Rev. No. 0
Compressed Air System
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4. SPEFICATION OF EQUIPMENT
A. Air Reciever

B. Compressor

C. Compressed Air System by Wartsila 26 Project Guide