Requirements for Air Conditioning &
Ventilation
Part 1
HM Surface Ships and Royal Fleet
Auxiliaries
Issue 2 Publication Date 8 September 2000
Revision Note
This Issue of this Standard has been prepared to incorporate changes to text and presentation.
The technical content has been updated in line with current practice.
Historical Record
Def Stan 02-102 (Part 1)/Issue 1
1 April 2000
REQUIREMENTS FOR AIR–CONDITIONING AND VENTILATION
PART 1 ISSUE 2 MARCH 2000
HM SURFACE SHIPS AND ROYAL FLEET AUXILIARIES
This Naval Engineering Standard
is authorized for use in MOD contracts
by the Defence Procurement Agency
and the Defence Logistics Organization
Published by:
Sea Technology Group,
Defence Procurement Agency,
STGSA,
Ash 0, #95,
MOD Abbey Wood,
Bristol BS34 8JH
SCOPE
1. This Naval Engineering Standard (NES) is applicable to all HM Surface Ships and Royal Fleet Auxiliaries (RFA). It defines the requirements for providing ventilation, airconditioning and equipment cooling in surface ships, the standards to which the various systems associated with these functions are to be designed, manufactured and installed.
2. The requirements for airconditioning, ventilating, purging and air purification in HM Submarines are covered by NES 102 Part 2.
FOREWORD
Sponsorship
1. This Naval Engineering Standard (NES) is sponsored by the Defence Logistics Organisation, Ministry of Defence (MOD).
2. The complete NES 102 comprises:
Requirements for Air-Conditioning and Ventilation
Part 1: HM Surface Ships and Royal Fleet Auxiliaries Part 2: HM Submarines
3. Any user of this NES either within MOD or in industry may propose an amendment to it. Proposals for amendments that are not directly applicable to a particular contract are to be made to the publishing authority identified on Page (i), and those directly applicable to a particular contract are to be dealt with using contract procedures.
4. If it is found to be unsuitable for any particular requirement MOD is to be informed in writing of the circumstances.
5. No alteration is to be made to this NES except by the issue of an authorized amendment. 6. Unless otherwise stated, reference in this NES to approval, approved, authorized and similar
terms, means by the MOD in writing.
7. Any significant amendments that may be made to this NES at a later date will be indicated by a vertical sideline. Deletions will be indicated by 000 appearing at the end of the line interval.
8. This NES has been reissued because of technical update
Conditions of Release
General
9. This Naval Engineering Standard (NES) has been devised solely for the use of the MOD, and its contractors in the execution of contracts for the MOD. To the extent permitted by law, the MOD hereby excludes all liability whatsoever and howsoever arising (including but without limitation, liability resulting from negligence) for any loss or damage however caused when the NES is used for any other purpose.
10. This document is Crown Copyright and the information herein may be subject to Crown or third party rights. It is not to be released, reproduced or published without written permission of the MOD
11. The Crown reserves the right to amend or modify the contents of this NES without consulting or informing any holder.
MOD Tender or Contract Process
12. This NES is the property of the Crown. Unless otherwise authorized in writing by the MOD must be returned on completion of the contract, or submission of the tender, in connection with which it is issued.
13. When this NES is used in connection with a MOD tender or contract, the user is to ensure that he is in possession of the appropriate version of each document, including related documents, relevant to each particular tender or contract. Enquiries in this connection may be made to the authority named in the tender or contract.
14. When NES are incorporated into MOD contracts, users are responsible for their correct application and for complying with contractual and other statutory requirements. Compliance with an NES does not of itself confer immunity from legal obligations.
15. The Category of this NES has been determined using the following criteria: a. Category 1. If not applied may have a Critical affect on the following:
Safety of the vessel, its complement or third parties.
Operational performance of the vessel, its systems or equipment.
b. Category 2. If not applied may have a Significant affect on the following: Safety of the vessel, its complement or third parties.
Operational performance of the vessel, its systems or equipment. Through life costs and support.
c. Category 3. If not applied may have a Minor affect on the following: MOD best practice and fleet commonality.
Corporate experience and knowledge. Current support practice.
Related Documents
16. In the tender and procurement processes the related documents listed in each section and Annex A can be obtained as follows:
a. British Standards British Standards Institution, 389 Chiswick High Road, London, W4 4AL
b. Defence Standards Directorate of Standardization, Stan 1, Kentigern House, 65 Brown Street, Glasgow, G2 8EX.
c. Naval Engineering Standards CSE3a, CSE Llangennech, Llanelli, Dyfed, SA14 8YP.
d. Other documents Tender or Contract Sponsor to advise. 17. All applications to the MOD for related documents are to quote the relevant MOD Invitation
to Tender or Contract number and date, together with the sponsoring Directorate and the Tender or Contract Sponsor.
18. Prime Contractors are responsible for supplying their subcontractors with relevant documentation, including specifications, standards and drawings.
Health and Safety
Warning
19. This NES may call for the use of processes, substances and/or procedures that are injurious to health if adequate precautions are not taken. It refers only to technical suitability and in no way absolves either the supplier or the user from statutory obligations relating to health and safety at any stage of manufacture or use. Where attention is drawn to hazards, those quoted may not necessarily be exhaustive.
20. This NES has been written and is to be used taking into account the policy stipulated in JSP 430: MOD Ship Safety Management System Handbook.
Additional Information
CONTENTS
Page No
TITLE PAGE
. . .
(i)
SCOPE
. . .
(iii)
FOREWORD
. . .
(v)
Sponsorship
. . .
(v)
Conditions of Release
. . .
(v)
Related Documents
. . .
(vi)
Health and Safety
. . .
(vi)
CONTENTS
. . .
(vii)
SECTION
1.
GENERAL INFORMATION
. . .
1.1
1.1
Climatic Conditions
. . .
1.1
1.2
Design Conditions
. . .
1.1
1.3
Ship Subdivision
. . .
1.2
1.4
Operational States
. . .
1.2
SECTION
2.
DESIGN REQUIREMENTS/CRITERIA
. . .
2.1
2.1
General Requirements
. . .
2.1
2.2
Environment Conditions
. . .
2.1
Figure 2.1
Basic Air-Conditioning System
. . .
2.2
Figure 2.2
Typical Air-Conditioning Cycle
. . .
2.3
2.3
Air-conditioning and Ventilation Systems
. . .
2.4
2.4
Machinery Spaces
. . .
2.5
2.5
Smoke Clearance
. . .
2.5
2.6
Chilled Water Systems
. . .
2.6
2.7
Local Exhaust Ventilation Systems
. . .
2.7
SECTION
3.
DESIGN PROCEDURE
. . .
3.1
3.1
Concept Studies
. . .
3.1
3.2
Feasibility
. . .
3.1
3.3
Design Leading to Contract Definition
. . .
3.4
3.4
Detailed Design
. . .
3.4
SECTION
4.
DESIGN DATA
. . .
4.1
4.1
Environmental Design Conditions
. . .
4.1
4.2
Cooling and Heating Assumptions
. . .
4.2
4.3
Total Heat Transfer Coefficient ‘k’
. . .
4.3
4.4
Relative Humidity
. . .
4.4
4.5
Air Distribution Systems
. . .
4.4
4.5.1
Design Margin
. . .
4.4
4.5.2
Air Velocities
. . .
4.4
4.5.3
Fresh/Filtered Air Requirements
. . .
4.5
4.6
Pressurization
. . .
4.6
4.6.1
Citadel and Zones
. . .
4.6
4.6.2
Machinery Spaces
. . .
4.6
4.7
Heating Systems
. . .
4.6
4.8
Chilled Water Systems
. . .
4.7
4.8.1
Design Margins
. . .
4.7
4.9
Chilled Water Temperatures
. . .
4.7
4.10
Velocities and Pipe Size
. . .
4.8
SECTION
5.
AIR DISTRIBUTION SYSTEMS
. . .
5.1
5.1
Design Objective
. . .
5.1
5.2
General Requirements
. . .
5.1
5.3
Air-conditioning Arrangements
. . .
5.2
5.4
Central ATU
. . .
5.3
5.5
Compartment ATU
. . .
5.3
5.6
ATU Controls
. . .
5.4
5.7
Special Requirements
. . .
5.4
5.7.1
Operational Spaces
. . .
5.4
5.7.2
Accommodation and Recreation Spaces
. . .
5.4
5.8
Medical Spaces
. . .
5.5
5.8.1
Sick Bays
. . .
5.5
5.9
Configuration No 1 (Full fresh air cooling)
. . .
5.6
5.10
Configuration No 2 (Semi-recirculation)
. . .
5.6
5.10.1
Dental Surgery
. . .
5.7
5.11
Bathrooms and WC
. . .
5.7
5.11.1
General Requirements
. . .
5.7
5.11.2
WC and Urinals
. . .
5.8
5.11.3
Bathrooms
. . .
5.9
5.12
Galleys and Associated Spaces
. . .
5.10
5.12.1
Galley, Servery and Scullery
. . .
5.10
5.12.2
Pantries and Pantry/Serveries
. . .
5.11
5.12.3
Miscellaneous
. . .
5.11
5.13
Laundries and Associated Spaces
. . .
5.12
5.14
Drying Rooms
. . .
5.12
5.15
Workshops
. . .
5.13
5.16
Sewage Treatment Spaces
. . .
5.14
5.17
Storerooms
. . .
5.14
5.18
Conversion Machinery Rooms
. . .
5.14
5.19
Magazines
. . .
5.15
5.20
Compartments Containing Dangerous or Noxious Gases
. .
5.17
5.20.1
General Requirements
. . .
5.17
5.21
Refrigeration Machinery Compartments, Refrigeration
Machinery and Bottle Stowages for Heavier than Air Gases
5.18
5.22
Battery Charging Rooms and Spaces Containing
Battery Charging Facilities
. . .
5.18
Page No
5.24
Hydrogen and Acetylene Storage Compartments
. . .
5.19
5.25
Compartments Containing Petroleum, Oils, Lubricants, etc. 5.20
5.26
HP Air Compressors
. . .
5.21
5.27
Incinerator Compartments
. . .
5.21
5.28
Hangars
. . .
5.21
5.29
Vehicle Decks
. . .
5.22
5.30
Electrical Switchboard Rooms
. . .
5.23
5.31
Emergency Generator Compartment
. . .
5.23
5.32
Steering Gear (Secondary Steering Position)
. . .
5.23
5.33
Dry Provision Room
. . .
5.23
5.34
Air Balance Diagrams
. . .
5.23
SECTION
6.
COOLING SYSTEMS
. . .
6.1
6.1
General
. . .
6.1
6.2
Statement of Style
. . .
6.1
6.3
Design Principles
. . .
6.1
Figure 6.1
Combined Essential and Non EssentialServices
Chilled Water System
. . .
6.3
Figure 6.2
Discrete Essential Services Chilled Water System
. . .
6.4
6.4
System Arrangement and Components
. . .
6.5
6.5
CW/Air Heat Exchangers (Coolers)
. . .
6.6
6.6
Materials
. . .
6.7
6.7
Cleanliness
. . .
6.7
6.8
Water Quality
. . .
6.8
6.9
Compartment Cooling
. . .
6.9
6.10
Air Treatment Units
. . .
6.9
6.11
CW Unit Coolers
. . .
6.9
6.12
Free Standing Air-conditioning Units
. . .
6.10
6.13
Equipment Cooling
. . .
6.10
6.14
Demarcation
. . .
6.11
6.15
Dehumidifiers and Condensation Control
. . .
6.11
6.16
Insulation
. . .
6.11
6.17
System Reliability
. . .
6.11
SECTION
7.
HEATING SYSTEMS
. . .
7.1
7.1
General Requirements
. . .
7.1
7.2
Air-conditioned Compartments
. . .
7.1
7.3
Hazardous Compartments Within the NBC Citadel
. . .
7.2
7.4
Fresh Air
. . .
7.2
7.5
Compartments Outside the NBC Citadel
(Ex Machinery Spaces)
. . .
7.2
7.6
Classification of Heaters
. . .
7.2
7.6.1
Supplementary/Boost Heaters
. . .
7.3
7.6.2
Reheaters
. . .
7.3
7.7
Heater Controls
. . .
7.3
7.8
Electric Heater Controls
. . .
7.4
7.9
Hot Water Heater Controls
. . .
7.4
7.10
Trunk Mounted Heaters
. . .
7.5
7.10.1
Electric Heaters
. . .
7.5
7.10.2
Hot Water Heaters
. . .
7.5
7.11
Space Heating
. . .
7.5
7.11.1
Types of Space Heaters
. . .
7.6
7.12
Hot Water Systems
. . .
7.6
7.13
Heater Markings
. . .
7.7
7.14
Humidifiers
. . .
7.7
SECTION
8.
MACHINERY SPACES
. . .
8.1
8.1
System Design
. . .
8.1
8.1.1
Cruise State/Open Ship Condition
. . .
8.1
8.1.2
Action State/Closed Down Condition
. . .
8.1
8.2
Cooling
. . .
8.1
8.3
Pressurization
. . .
8.2
8.4
Air Systems
. . .
8.2
8.5
General
. . .
8.3
8.6
Heating
. . .
8.3
8.7
Machinery Space Ventilation Trials
. . .
8.4
SECTION
9.
NBCD & FIRE FIGHTING ARRANGEMENTS
. . .
9.1
9.1
NBCD Subdivision (See NES 118)
. . .
9.1
9.2
Fire Fighting Subdivision (See NES 119)
. . .
9.1
9.3
Citadel Pressurization
. . .
9.1
9.4
Intake of Ambient Air
. . .
9.2
9.4.1
Calculated Uncontrolled Leakages
. . .
9.2
9.4.2
Known Controlled Leakages
. . .
9.3
9.4.3
Control Of CO2
. . .
9.3
9.5
Air Filtration Units and NBC Filters
. . .
9.3
9.5.1
Centralised AFU
. . .
9.4
9.5.2
Specialised AFU
. . .
9.5
9.6
Purging
. . .
9.5
9.7
Air Locks (Citadel Exits)
. . .
9.5
9.8
Cleansing Station (Contamination Control Area)
. . .
9.6
9.9
Fire Fighting and Fire Precautions
. . .
9.6
9.10
Smoke Clearance/Containment - Policy (Surface Ships)
. . .
9.7
9.11
Crash Stopping of Fans
. . .
9.9
9.12
High Risk Areas
. . .
9.10
9.12.1
Galleys (Also See Section 5)
. . .
9.10
Page No
9.14
Fire Flaps
. . .
9.11
Figure 9.1
Typical Fire Flap
. . .
9.12
Figure 9.2
Typical Flameproof Gauze
. . .
9.13
9.15
NBCD Ventilation Board
. . .
9.14
9.16
Fire Precautions in Royal Fleet Auxiliary Vessels
. . .
9.14
SECTION
10.
FANS
. . .
10.1
10.1
Fan Selection
. . .
10.1
10.2
Materials
. . .
10.1
10.3
Construction
. . .
10.1
Figure 10.1
Application of Constant Orifice Line to
Design Margins
. . .
10.2
10.4
Motors
. . .
10.3
10.5
Availability, Reliability and Maintainability (ARM)
. . .
10.3
10.6
Noise
. . .
10.3
10.7
Shock
. . .
10.3
10.8
Vibration (Self Generated)
. . .
10.3
10.9
Vibration (Externally Generated)
. . .
10.3
10.10
Fan Testing
. . .
10.3
10.11
Mounting and Siting of Fans
. . .
10.4
10.12
Special Fans
. . .
10.5
10.13
Fan Markings
. . .
10.5
SECTION
11.
TRUNKING AND FITTING
. . .
11.1
11.1
General
. . .
11.1
11.2
Non-Watertight, Non-Gastight Trunks
. . .
11.1
11.3
Textile Ventilation Trunking
. . .
11.2
11.3.1
Advantages
. . .
11.3
11.3.2
Disadvantages
. . .
11.4
11.4
Gastight and Structural Trunks and Trunks
Subjected to Rough Usage or High Fire Risk
Including Smoke Removal Systems
. . .
11.4
11.5
Watertight Trunks
. . .
11.5
11.5.1
Trunk Installation.
. . .
11.5
11.6
Vulnerability
. . .
11.6
Figure 11.1
Typical Hanger Supports
. . .
11.7
11.7
Trunking - Associated Fittings
. . .
11.8
11.8
Weather Terminals
. . .
11.8
11.9
Supply Outlets
. . .
11.8
11.10
Exhaust/Recirculation Intakes
. . .
11.9
11.11
Miscellaneous Fittings
. . .
11.9
11.12
Insulation
. . .
11.10
Figure 11.2
Typical Hose Conection for Ventilation Trunks
. . .
11.11
SECTION
12.
FILTRATION
. . .
12.1
12.1
General
. . .
12.1
Figure 12.1
Typical Dust Filter Mounted in a Trunk
. . .
12.3
Figure 12.2
Typical Dust Filter for Openings in Exhaust
and Recirculation Trunks
. . .
12.4
12.3
Odour Filters
. . .
12.5
12.4
Tobacco Smoke Filters
. . .
12.5
12.5
Grease Filters
. . .
12.5
Figure 12.3
Typical Tobacco Smoke Filter
. . .
12.6
12.6
Fresh Water Filters
. . .
12.7
12.7
Standard NBC Filters
. . .
12.7
SECTION
13.
VENTILATION NOISE
. . .
13.1
13.1
General
. . .
13.1
13.2
Siting and Mounting of Fans
. . .
13.1
13.3
Trunking and Fittings
. . .
13.2
13.4
System Sound Analysis
. . .
13.2
13.5
Tests and Trials
. . .
13.3
SECTION
14.
DESIGN FOR MAINTENANCE AND
SHIP HUSBANDRY
. . .
14.1
14.1
General
. . .
14.1
14.2
Fittings
. . .
14.2
14.3
Drainage
. . .
14.3
14.4
Filters
. . .
14.3
14.5
Water Systems
. . .
14.3
SECTION
15.
INSPECTIONS, TESTS AND TRIALS
. . .
15.1
15.1
General Comments
. . .
15.1
15.2
Factory Testing
. . .
15.1
15.2.1
Type Tests
. . .
15.1
15.3
Production Tests
. . .
15.2
15.4
Progress Inspections
. . .
15.3
15.5
NBC Filtration, Inspection and Testing
. . .
15.3
15.6
Final Inspection
. . .
15.3
15.7
Testing and Balancing
. . .
15.3
15.7.1
Air Systems
. . .
15.3
15.8
Air Test Reports
. . .
15.4
15.9
Water Systems
. . .
15.5
15.10
Zonal Pressures Tests
. . .
15.7
15.11
Habitability Trials
. . .
15.7
15.12
Performance Trials
. . .
15.8
15.13
Airborne Noise Trials/Surveys
. . .
15.9
15.14
Instruments
. . .
15.10
ANNEX
A.
RELATED DOCUMENTS
. . .
A.1
ANNEX
B.
ABBREVIATIONS AND DEFINITIONS
. . .
B.1
1.
GENERAL INFORMATION
Related Documents: NES 809 Part 1; see also Annex A.
1.1
Climatic Conditions
a. For design purposes hot weather and cold weather climates throughout the world are each divided into the following conditions, viz:
(1) Hot Weather (a) Tropical;
(b) Temperate Summer. (2) Cold Weather
(a) Temperate Winter; (b) Subarctic;
(c) Arctic.
1.2
Design Conditions
a. The limiting climatic conditions to be applied to any ship design will be specified in the Staff Requirements (Sea) (SR(S)) for that particular class of vessel and thus, in consequence of this NES, the internal ship conditions will also be defined.
b. The SR(S) will also indicate where the actual design may, if at all, deviate from the standards and policies herein and, where appropriate, it will specify the modified standards that are to be achieved.
c. Unless specifically modified by the SR(S) it is essential that all the margins stated in this NES are applied fully throughout the design. Initial allowances consumed by growth during the design stages need to be compensated for, to ensure sufficient margins are present in the final design to allow for through life growth and degradation of the various systems. The chilled water margins are also required as airconditioning machinery cannot be run under overload conditions. If an attempt is made to do so the plant may trip out, resulting in a significant reduction in the ship's operational efficiency. Allowances for erosion of growth margins will be discussed and identified at the outset of the design calculations.
d. HM Surface ships that are to be commercially registered, e.g. Royal Fleet Auxiliaries (RFA) are, where possible, to comply with Department of the Environment, Transport and the Regions (DETR) regulations that govern firefighting and safety aspects. Where DETR and MOD standards are at variance and both sets of regulations can be accommodated then the more stringent are to be applied. As it is imperative that Nuclear Biological and Chemical Defence (NBCD) integrity and the operational efficiency are not jeopardised in any circumstances any DETR rules or regulations which place the vessel at risk shall not be applied and the relevant exception to or exemption from these rules should be sought from the regulatory body and entered in the commercial registration documents. Full compliance with DETR regulations will be impossible as they have no category suitable for HM Surface Ships and would normally register the vessel in the closest appropriate commercial classification. In these circumstances discussions should take place at the outset of the design where differences or conflicts will be clearly identified and reconciled by all concerned parties.
e. In all surface ship designs, unless stated otherwise in the SR(S), it is important to achieve a reduced Radar Cross Section (RCS). The recommendations of NES 809 Part 1 are to be addressed in the design of all external features, and in particular the creation of orthogonal dihedrals and trihedrals with cosited features is to be avoided.
1.3
Ship Subdivision
a. For each new class of surface ship the MOD will produce a ship subdivision policy paper in the early stages of, or prior to, Feasibility Design that will comprehensively state the rules governing the subdivision of that particular class of vessel.
b. Surface ships can be divided as:
(1) Watertight decks and bulkheads; (2) NBCD citadels and subcitadels;
(3) Autonomous fire/smoke zones and ventilation subzones within the autonomous zones.
c. The design of the ventilation and airconditioning arrangements are to be compatible with each of these subdivisions and the ducted systems are to be autonomous within individual fire zones. In the action state when all subdivision boundaries are secured the free flow of recirculated air from compartment back to fan is not to be obstructed.
1.4
Operational States
a. Two operational states have to be catered for, viz: (1) Cruise state or `open ship' condition;
(2) Action state or `closed down' condition.
b. Within the NBCD citadel, the change from cruise to action state is to be effected by implementing air lock, cleansing station and zonal disciplines and redirecting all incoming fresh air through NBCD filters. Ventilation and airconditioning systems are not to be reconfigured to enable this to be achieved.
c. For those compartments outside the NBCD citadel and classed as contaminated if used, every effort is to be made for these spaces to be supplied with air from the citadel with natural or fan exhaust to atmosphere. Only when these spaces entail excessive amounts of conditioned air should mechanical fan supply and exhaust systems be considered. In the machinery spaces, it is to be achieved by reconfiguring the ventilation systems into recirculation systems, closing external openings, supplying chilled water to machinery space coolers and initiating dedicated filtration units.
d. Once `closed down' it is to be possible to maintain that condition indefinitely without discomfort to personnel or loss of operational efficiency, unless the SR(S) for the vessel stipulates a specific time scale.
2.
DESIGN REQUIREMENTS/CRITERIA
Related Documents: Health and Safety at Work Act, COSHH Regulations; see also
Annex A.
2.1
General Requirements
a. This section deals with the requirements governing the overall design of ventilation and airconditioning arrangements that are to be fitted in Royal Navy (RN) vessels. It defines the current policy that is to be applied and describes the style of various associated systems. It is the Designers responsibility to incorporate these requirements.
b. Airconditioning, that is the control of temperature, humidity, air purity and air movement within a space or group of spaces, is a prime requirement in all RN vessels. It is an essential element in ensuring that the ship's staff continue to operate at high levels of effectiveness and efficiency for long periods and the environment for weapons and other essential equipments is, and always remains, satisfactory for reliable operation. This environmental control has to be achieved throughout the full spectrum of ambient conditions for which the ship is to be designed.
c. All compartments within a ship are to be classified by the designer as either essential or nonessential to the operational efficiency of the vessel and these classifications made known in the airconditioning design.
d. For essential compartments the airconditioning is to be based upon the `Group System' where a mixture of fresh and recirculated air is delivered to an Air Treatment Unit (ATU) where it is filtered, cooled or heated, and distributed to a selected group of essential compartments (A `group' can be one or several compartments). In certain circumstances the cooled air may need to be reheated locally before being delivered to particular spaces to obtain the necessary humidity control, but the use of this technique is to be kept to a minimum (See Figures 2.1 and 2.2).
e. For nonessential compartments the airconditioning is to be based either upon the `Group System' as described above, except that the relevant ATU is to only supply nonessential spaces, or, if more appropriate, on the use of Unit Coolers.
2.2
Environment Conditions
a. The design of the airconditioning systems is to cater for the extreme ambient temperatures stated in the SR(S) and the corresponding internal temperatures given in Section 4. The final design of the installed systems is to include sufficient flexibility and controllability to allow comfortable internal environments to be selected and maintained throughout the full range of conditions bounded by these extremes. This flexibility is especially important in spaces where the internal conditions can vary significantly and speedily due to movement of personnel or change of equipment status and should be achieved by the use of sensors situated in appropriate locations.
RETURN A SUPPLY TRUNK THERMOSTAT BOUNDARY GAINS - (SH) EQUIPMENT (SH+LH, IF ANY PERSONNEL (SH+LH)
HOT MACHINERY SPACE ETC.
C
RECIRCULATED AIR ROUTE (MAY BE TRUNKED) EVAPORATOR CONDENSER COMPRESSOR C.W. PUMP REFRIGERANT CIRCUIT HEAT EXCHANGER
CHILLED WATER PLANT FRESH FILTERED
AIR DIRECT FROM AFU SH+LH
ELECTRIC PRE-HEATER CHILLED WATER SYSTEM
ELECTRIC RE-HEATER
CONNECTION BOX
AIR TREATMENT UNIT
MOISTURE ELIMINATOR FILTER B BYPASS FAN A1
SURPLUS AIR DISCHARGED OVERBOARD VIA HAZARDOUS COMPARTMENT EXHAUST SOLAR RADIATION
FLOW
NOTE A, A1, B, C and D REFERTO
POINTS SHOWN IN FIGURE 2.2
NOTE
SH - Sensible Heat LH - Latent Heat AFU - Air Filtration Unit
CONDENSER COOLING WATER D
C 5 10 15 20 25 0 40 30 20 10 RELATIVE HUMIDITY 50 70 60 90 100% 90%
DRY BULB TEMPERATURE deg C
MOISTURE CONTENT g/Kg 12.5 10 15 17.5 22.5 25 27.5 20 D A B A1 Air-Conditioning CYCLE 80 NOTE For information on A, A1, B, C and D See Figure 2.1
2.3
Air-conditioning and Ventilation Systems
a. In all ships, where required, the complete airconditioning and ventilation design for compartments and spaces necessary for the functionality of the vessel in a `closed down' ship, is to be based upon the Total Atmospheric Control System (TACS) concept which has been developed to achieve the minimum practicable changeover time from `open ship' to `closed ship' condition and to enable continuous operations to be conducted in a Nuclear, Bacteriological and Chemical Warfare (NBCW) threat situation. This concept requires all fresh air entering the NBCD citadel to be directed through NBC filtration units when in the closed down condition but in the `open ship' condition these filters are to be bypassed. Compartments not necessary for the functionality of the vessel during NBC transits should not ideally be located within the citadel but due to the logistics of the ship they may well be and in these instances would be airconditioned or ventilated as required. In such cases the airconditioning/ventilation is normally to be by independent systems taking their required fresh air quantities from weather (not via Air Filtration Units AFU) and they would be secured in a `closed down' situation, however in isolated cases these spaces can be served by an adjacent TACS airconditioning system.
b. All compartments and spaces within the citadel are to be airconditioned or ventilated as above with the exception of those compartments classed as hazardous, i.e. compartments within the citadel which contain materials that may generate dangerous or toxic fumes and gases and those where such fumes and gases are produced by processes and functions carried out in the compartment. These spaces are to be airconditioned/ventilated to conditions specified in Section 5 Clause 5.20.
c. Special attention is to be paid to those compartments within the citadel that are a source of unpleasant smells or noxious gases, e.g. bathrooms, WC, laundries, galleys, etc. In these types of compartment sufficient air is to be circulated to ensure that odours are removed via a recirculation system employing odour filters. For specific requirements for these compartments See Section 5. d. The design of the air systems is to take account of and be compatible with the
shipsubdivision policy for each particular ship design. The air systems are to be completely autonomous within the fire/smoke zones, and under no circumstances is ducting to breach zone boundaries. It is essential that air balance diagrams for each fire zone are prepared and maintained throughout the design to ensure that differential pressures across zonal boundaries are maintained within the limits specified in Section 9.
e. In both the `closed down' and `open ship' conditions the fresh air intake into the citadel is to be via the AFU fans (See Figure 2.1). The fresh air quantity is to be sufficient to compensate for known controlled losses and calculated uncontrolled leakages, whilst maintaining an acceptable citadel over pressure and providing oxygen to revitalise compartment air by ensuring that CO2 content levels are kept below the maximum permissible levels. The fresh air required for oxygen replenishment is to be trunked direct to individual ATU where it is treated and distributed as necessary. The remaining fresh air is to be used to provide an over pressure in essential compartments (See Section 9) or is to be trunked from the AFU fan directly to or in the vicinity of any compartment, Air Lock or Cleansing Station deemed necessary for maintaining the integrity of the citadel.
2.4
Machinery Spaces
a. Machinery spaces are to be considered as outside of the NBCD citadel and in the `open' condition are to be ventilated by mechanical supply and mechanical exhaust systems. The flow of air is to be such that in specified summer conditions the compartment temperature will be maintained within stated limits when all normally running equipments are operating. In cold weather conditions the air flow is to be capable of being significantly reduced and sufficient electric heating provided to maintain temperatures which facilitate the ease of starting up of machinery (normally 10°C) in the `dead ship' condition.
b. The system design is to provide, where required, for the reconfiguration of the ventilation systems so that, in the `closed down' condition it will be possible to recirculate the compartment air through chilled water coolers and isolate the machinery spaces from the external ambient air. In this state a positive pressure (normally 3 millibars above ambient air pressure) is to be created and maintained in the machinery spaces by introducing a quantity of fresh air through dedicated NBC filtration units. These filtration units are to be nonoperational in the `open ship' condition and the quantity of fresh air required is to be calculated by the summation of any known controlled losses and the calculated uncontrolled leakages based on a loss of 0.5air changes per hour on the gross volume of the machinery spaces inclusive of casings if open to the machinery space.
c. The chilled water coolers in machinery spaces are to be operational in the `closed down' state and capable of being supplied from a standby nonessential chilled water plant. Sufficient heat is to be extracted to allow the ship to be fully operational for the total `closed down' period and at the extreme ambient temperatures specified in the SR(S), without these spaces becoming contaminated. Machinery space `closed down' cooling requirements are to be taken into account when allocating the number and capacity of the airconditioning chilled water refrigeration plants.
2.5
Smoke Clearance
a. Where a ship design includes damage fire and smoke zones, a dedicated trunked smoke clearance system is to be provided in each zone. These systems are to be arranged such that, within each zone, individual decks may be cleared of smoke and allow sufficient replacement air, without other unaffected decks being contaminated.
b. Dedicated smoke clearance systems are not required in machinery spaces which contain exhaust fans as these fans will be utilised for smoke clearance.
operational efficiency of the vessel in a fire situation, such compartments are to be capable of being maintained at a positive pressure relative to the surrounding passageways and lobbies.
2.6
Chilled Water Systems
a. Chilled Water (CW) systems are to provide the means for transferring heat from the heat exchangers, situated throughout the vessel, to Chilled Water Plants (CWP) and hence overboard via condenser cooling water.
b. Two categories of CW systems are to be included in any ship design, namely: (1) Essential systems supplying essential heat exchangers that cool essential
compartments and equipments. These systems are to be constrained within NBCD/smoke zones and several of this type will be included in each ship design;
(2) Nonessential systems supplying nonessential ATU and unit coolers that cool nonessential spaces. This will be a ship wide system and each ship will only contain one of this type.
c. Connections are to be provided between the nonessential system and each essential system to enable the essential heat exchangers to be continuously supplied, when necessary, at the expense of the nonessential.
d. Adequate margins are to be applied to allow for through life growth and system degradation when selecting CWP and calculating pipe sizes.
e. The nonessential system is to be provided with a standby CWP so that all systems will be able to operate continuously during periods of routine maintenance or single plant breakdown. The standby CWP is not to be considered as a growth margin.
f. In any ship design the preferred arrangement is for all essential systems to be served by identical CWP, a single plant supplying each system, and for all CWP serving the nonessential system to be identical.
g. The nonessential CWP are to be capable of cooling the machinery spaces in the `closed down' condition.
h. Rapid refill arrangements as well as normal toppingup facilities are to be provided.
i. The design of the system and its associated equipment is to ensure that the Relative Humidity (RH) levels in individual compartments are maintained between specific upper and lower limits but in exceptional circumstances, in difficult spaces, the use of approved humidifiers and dehumidifiers is acceptable.
j. In particular compartments where heavy condensation is liable to occur special attention is to be given during the design stage to removing moisture from the circulating air and to the use of thermal insulation to eliminate potential problems.
2.7
Local Exhaust Ventilation Systems
a. Those systems defined under the Health and Safety at Work Act (HSWA), Control of Substances Hazardous to Health (COSHH) Regulations 1992 as Local Exhaust Ventilation (LEV) Systems are to be provided, these are to include fixed monitoring instrumentation to allow for through life ventilation system flow monitoring.
b. Each designated LEV system is to have: (1) The test point(s) marked;
(2) The required test date annotated on a plate and fixed adjacent to the test point;
3.
DESIGN PROCEDURE
Related Documents: BS 1553 and NES 707 Parts 1 & 2; see also Annex A.
a. The design of the airconditioning and ventilation systems is to follow and reflect the total ship design. When considering the various types of studies undertaken it is to be understood that a ship design is a dynamic entity where decisions taken in one area, will often have repercussions in many other areas and airconditioning and ventilation estimates, calculations, drawings, etc., will need to be continually reassessed and updated.
b. Within the field of airconditioning and ventilation the total design process can be divided as follows:
(1) Concept studies; (2) Feasibility studies;
(3) Design leading to Contract Definition; (4) Detailed design.
3.1
Concept Studies
a. These are studies to formulate new design philosophy, policies and criteria and to assess the impact of any proposed changes in future ship design. They are usually undertaken by the MOD with assistance from selected contractors, and are not necessarily associated with a particular ship design.
3.2
Feasibility
a. These are studies to combine the existing philosophy, policies and criteria with a developing ship design, for a specific role, and are normally carried out by a shipbuilder and his prime contractor, with assistance from MOD sponsors. b. For feasibility studies to commence, the following information is required:
(1) Design conditions; (2) Ship subdivision policy;
(3) Compartment details (size, manning, function, wild heat, etc.); (4) Weapons fit and direct cooling loads.
c. This information is to be available from MOD sources when the SR(S) is approved. When this is not the case the best possible estimates and assessments are to be made to allow the design of the airconditioning and ventilation systems to be progressed as soon as possible and updated when absolute details are obtained by the shipbuilder.
d. During this stage of the design the following information is to be submitted to the MOD for records and, where necessary, comments:
(1) Design philosophy table giving details of Heating Ventilation and AirConditioning (HVAC) requirements for all compartments on the vessel. This table should include the compartment name, location, specified summer and winter conditions to be maintained, exhaust requirements, noise target and manning levels, equipment wild heat emissions and any additional remarks pertinent to the design of the HVAC system;
etc., and programmes for testing new equipments and fittings that required `approval to fit';
(3) Classification of compartments as essential, nonessential and hazardous, and identification of those outside citadel boundaries; (4) Calculations of heat gains and losses for every compartment, workshop
and store, etc.;
(5) Grouping of compartments to show the number of essential and nonessential heat exchangers/ATU, the number of hazardous systems and the number of ventilation systems required in each NBCD/fire zone; (6) Selection of type, size and numbers of CWP for essential and
nonessential CW systems;
(7) Calculations of air quantities and CW flows required for all systems; (8) Size, type and numbers of fans, air/water and water/water heat
exchangers, heaters, humidifiers and other equipments;
(9) Fresh air requirements in individual zones, machinery spaces and the number of AFU required;
(10) Identification of compartments to be pressurized by a direct supply of fresh air to prevent infiltration of smoke;
(11) Identification of ventilation and smoke clearance systems; (12) Calculation of trunk and pipe sizes;
(13) Calculation of `induct' and `breakout' noise levels in manned compartments and assessment of all the acoustic insulation requirements;
(14) Calculation of space relative humidities and identification of humidification requirements;
(15) Statement of electrical requirements, including crash stopping of fans; (16) Table of weights.
e. During this design stage, to augment the calculation sheets and equipment lists indicated above, the following drawings are to be prepared, continually updated as necessary and submitted to the MOD immediately prior to the hand over of the vessel so that calculations and drawings reflect the completed HVAC systems.
(1) Scaled single line `Air Systems General Arrangement' drawings on deck plans showing:
(a) All air systems, i.e. essential, nonessential, hazardous, fresh, smoke clearance, natural and mechanical ventilation;
(b) Position of ATU and other air/water and water/water heat exchangers;
(c) Position of AFU;
(d) Zonal boundaries and watertight subdivision;
(e) Siting of fans, heaters, filters, moisture eliminators, valves and other fittings;
(f) Type, size and number of terminals fitted in each space; (g) Sizes of trunks;
(h) Extent of watertight and gastight trunking; (i) Citadel boundary.
(2) Air balance diagrams for each NBCD/fire zone and machinery space to demonstrate that in `closed down' conditions:
(a) Recirculation routes from airconditioned compartments back to fan intakes are unobstructed by doors, hatches, fire curtains, etc.; (b) Access to and from adjacent zones will not be hampered by
unacceptable differential air pressures;
(c) Hot, oil contaminated air will not migrate from the machinery spaces into the citadel.
(3) Planimetric drawings of each essential and nonessential chilled water system indicating:
(a) All pipe runs, tee junctions, bends, etc.;
(b) All air/water and water/water heat exchangers and the compartments/equipments supplied by each one;
(c) All control panels, filters, flow switches, air vents, sampling points, isolating valves and other fittings inserted in the pipelines;
(d) The CWP and pumps, with cross connections where applicable; (e) Pipe lengths and diameters between junctions for both flow and
return pipes;
(f) Flow of CW in m3/s through each pipe section.
(4) Scaled single line `CW Systems General Arrangement' drawing on deck plans showing:
(a) Pipe routes;
(b) Position of CWP and pumps; (c) Zonal subdivision;
(d) Position and classification of each heat exchanger, i.e. essential, nonessential or stand by.
3.3
Design Leading to Contract Definition
a. During this stage the airconditioning and ventilation systems are to be continually amended and updated to reflect changes made in the overall ship design. In addition the many and varied estimates, used during the feasibility stage, are to be progressively refined and confirmed with the calculations, equipment selections, drawings, etc., produced during that stage, being reassessed as necessary.
b. By the end of this stage the following is to be complete: (1) All basic design data confirmed;
(2) Classification and grouping of compartments agreed;
(3) All calculations of air flows, CW flows, trunk and pipe sizes finalized; (4) Selection of equipments and materials approved and where appropriate
configuration definition packages prepared;
(5) Selection of fittings agreed and where appropriate new types of fittings tested and approved for use;
(6) Upgrading of `Air Systems General Arrangement' drawings to double line convention;
(7) Upgrading of `Chilled Water Systems General Arrangement' drawings to show supply and return leads and siting of all fittings included in the pipework;
(8) CW planimetric, air balance diagrams, upgraded general arrangements, configuration definition packages, etc., are all to be brought to Modification State Zero, i.e. the stage at which the MOD will become the Design Authority (DA) for support;
(9) Electrical requirements finalized;
(10) Statement of Requirements for Total Ship System and Design Critique prepared and agreed.
3.4
Detailed Design
a. Large scale layout drawings of compartments and spaces are to be produced which accurately show the final positions and sizes of all CW and condensate pipes, airconditioning and ventilation trunking, equipments and fittings, electrical leads and controls, etc., that are associated with the airconditioning and ventilation of the vessel. These drawings are also to show the clear access areas that are required to enable items, such as filters and fan motors, to be withdrawn for servicing.
b. Drawings are to be prepared to demonstrate the method of handling heavy equipments, such as fans, heat exchangers and AFU in congested areas to enable repair or replacement of these equipments to be carried out at sea. c. All drawings, equipment lists, data sheets, etc., prepared during the previous
stages are to be amended, as necessary, to reflect the final ship fit.
d. Throughout all stages of the design the symbols and line conventions used when producing the required drawings are to be in accordance with NES 707 Parts 1 & 2 and BS 1553 Parts 1 & 3.
4.
DESIGN DATA
Related Documents: ISO 7547 and NES 111; see also Annex A.
a. The calculation of heating and cooling loads and the sizing of pipes and ducting can be carried out by manual methods or by computer programs. In either case the calculations are to be based upon the design data given in this section and proven established processes such as Building Services Research Industrial Association (BSRIA), Engineering System Design Methods (ESDM), Civil Institute Building Services Engineering (CIBSE) and International Standards Organisation (ISO) 7547, etc.
4.1
Environmental Design Conditions
a. External Temperatures (Hot Climates)
Climate
Dry Bulb
(DB)
C
Wet Bulb
(WB)
C
Surface
Sea Temperature
C
Tropics 35 30 33 Temperate Summer 30 24 29b. External Temperatures (Cold Climates)
Climate
Dry Bulb
(DB)
C
Wet Bulb
(WB)
C
Surface
Sea Temperature
C
Temperate Winter -4 N/A 2
Sub-Arctic -10 N/A –1
Arctic -29 N/A –2
c. Internal Temperatures Airconditioned Spaces (unless otherwise specified in subsequent sections):
(1) Tropics:
(a) All compartments, except galley complex, 23.5°C Effective Temperature (27.0°C DB/19.6°C WB);
(b) Galley complex, 29°C Effective Temperature (34.5°C DB/26°C WB). (2) Temperate Summer:
(a) All spaces except the galley complex, 23.5°C Effective Temperature (27°C DB/19.6°C WB);
(b) Galley complex, 25.5°C Effective Temperature (29.5°C DB/21.5°C WB).
(3) All Cold Climates:
d. Internal Temperatures Ventilated Spaces (unless otherwise specified in subsequent sections):
(1) All Hot Climates:
(a) All spaces, except galleys where the TACS concept is not required, unmanned electrical compartments, main and large auxiliary machinery spaces, compartment temperature above weather ambient temperature;
(b) Galleys, etc., and unmanned electrical compartments, the space temperature restricted to 10°C above weather ambient.
(c) Main and large auxiliary machinery spaces, in `open ship' condition, temperature rise above external ambient restricted to 15°C. (for `closed down' condition, see Section 8).
(2) All Cold Climates:
(a) All spaces, in all operating conditions, 13°C DB minimum.
(b) Main and large auxiliary machinery spaces, in the `deadship' condition, 10°C DB minimum, i.e. alongside with only hotel services running.
4.2
Cooling and Heating Assumptions
a. The cooling and heating loads for each compartment are to be assessed on the basis of the following assumptions:
(1) Cooling conditions:
(a) Solar radiation occurs on exposed surfaces, weatherdecks and both sides of the ship simultaneously except for compartments extending the full width of the vessel when solar radiation is to be assumed on one side only;
(b) No shade is cast by superstructure, funnels, masts, etc.;
(c) Internal wild heat sources are at maximum value, excluding standby equipments;
(d) Maximum number of personnel are in each compartment, considered individually. Number of personnel in dining halls, recreation spaces, ward rooms and ante rooms, etc., are to be the maximum likely to attend film shows and functions, as appropriate; (e) Should the ship be fitted with current inservice equipment then in any compartment the heat gained from the fan and fan motor is equal to 14% x sum of cooling sensible heat gains for that compartment However, should the equipment fitted be to good commercial marine standards then this figure would revert to 7%; (f) Although it is specified in Clause 4.2a(1)(d) above that the maximum number of personnel be allowed for when calculating cooling loads on an individual compartment basis, this would result in an overall cooling capacity for numbers far in excess of the ships complement. Therefore, on completion of cooling calculations, the duplication of manning levels should be determined and the overall cooling capacity reduced accordingly. Allowances for heat gains from personnel are given in Clause 4.3.e.
(2) Heating conditions:
(a) Internal wild heat sources are at minimum value, i.e. maximum value 40%;
(b) No heat gained from personnel;
(c) No heat gained from adjacent compartments where the maintained temperature is non specific;
(d) No heat gained from solar radiation;
(e) Heat gained from fan and fan motor is the same as for cooling conditions;
(f) Heat is lost to adjacent cooler spaces;
(g) Heat is lost through the superstructure to sea and air.
4.3
Total Heat Transfer Coefficient ‘k’
a. Total heat transfer coefficients are to be calculated in accordance with the formula quoted in ISO 7547 (Clause 5.2.4) using the thermal conductivities for common materials as given in Annex B of that standard and/or publications from BSRIA or CIBSE. The Table 2 figures given in the ISO as typical heat transfer coefficients for various types of boundaries are not to be used for RN ships, as insulation materials, thicknesses and standards can vary considerably. For Cold and Cool rooms see NES 111.
b. The wild heat generated by equipments is to be based upon the actual power ratings obtained from the equipment manufacturers. In the early stages of the design such information is not always available and it will be necessary to make the best possible estimates, e.g. ruleofthumb methods such as the values given in the following table for the heat gain from compartment lighting:
Compartment
p
Heat gain from general lighting (W/m
2)
Type
Incandescent
Flourescent
Cabins, etc. 15 8
Mess or dinning rooms 20 10
Gymnasiums, etc. 40 20
c. When calculating the maximum heat load generated by galley equipment the following criteria is to be used:
(1) From the galley equipment's maximum electrical power inputs and employing diversity factors of 0.2 for thermostatically controlled items and 0.5 for manually switched heat controlled items, also assessing the maximum projected usage of equipment, a peak power input figure is arrived at, e.g.
Shallow fryers 15.0 kW input@ 0.2 = 3.0 kW
Deep fryers 30.0 kW input@ 0.2 = 6.0 kW
Hot plate/ovens 50.0 kW input@ 0.5 =25.0 kW
Other items 20.0 kW input@ 0.5 =10.0 kW
Total diversified input =57.0 kW
d. This diversified electrical power input is then to be converted into a heat emission into the galley and this is arrived at by using a further diversity factor of 50%, e.g. total diversified input of 57.0 kW = 57.0 x 50% = 28.5 kW heat emission.
e. The wild heat generated by personnel is to be taken as: Sensible heat = 45 Watts/man;
Latent heat = 135 Watts/man.
f. When separate sleeping and recreational areas are contained within a single mess deck the above allowances are to be increased to 55 Watts and 165 Watts respectively.
4.4
Relative Humidity
a. In airconditioned compartments, in all climatic conditions, the design relative humidity is to always lie between 65% and 30%. In accommodation and manned operational spaces a lower limit of 45% is to be applied and only in very exceptional circumstances is the RH to fall below this figure.
4.5
Air Distribution Systems
4.5.1 Design Margin
a. When selecting fans for airconditioning and ventilation systems the design air volume is to be increased by a 10% margin, calculated on the system constant orifice line (See Section 10). Trunk sizing calculations are then to be carried out using the design air flow and the related total fan pressure as indicated by the constant orifice line.
4.5.2 Air Velocities
a. In airconditioning and ventilation systems serving operational, habitational accommodation, office spaces and other manned working areas the trunked air velocities are generally to observe the following criteria :
Initial design velocity 10 m/s; Maximum permissible velocity 12.5 m/s.
b. In compartments or spaces with low noise target levels every effort should be made to ensure that duct configurations are so designed that velocities are retained at levels which would not result in noise generation.
c. Compartments other than those indicated above where noise target levels are not as restrictive may be served by airconditioning and ventilation systems with higher velocities to facilitate space restrictions.
d. The maximum design air velocities through various types of aperture are to be as follows:
(2) Supply inlets and exhaust outlets with the exception of spray eliminating jalousies 5 m/s calculated on the clear area;
(3) Spray eliminating jalousies 5 m/s calculated on the face area; (4) Slotted trunks, (supply and exhaust):
(a) Vertical velocity through slot 4 m/s; (b) Horizontal velocity through slot 10 m/s.
(5) Punkah louvres, diffusers, linear grilles, etc., discharge velocity 3 m/s; (6) Flame proof gauze 5 m/s calculated on the clear area;
(7) Dust filters 2.5 m/s.
e. The maximum face velocity of air passing through a CW/air heat exchanger without a moisture eliminator fitted is to be restricted to 2.0 m/s. Moisture eliminators should not be fitted unless absolutely necessary, however if one is to be fitted then the face velocity across the heat exchanger can be increased to a maximum of 3.0 m/s.
4.5.3 Fresh/Filtered Air Requirements
a. Within the NBCD citadel the fresh air requirement is to be individually assessed for each NBCD/fire zone and is to be sufficient to:
(1) Overcome the calculated uncontrolled leakage and thereby generate the specified zone pressure. This is to be calculated based on an allowance of 900 m3/hr of filtered fresh air for every 3,400 m3 of citadel volume above the deep water line;
(2) Overcome the known controlled purging exhaust requirements in a `open ship' condition;
(3) Overcome the known controlled purging exhaust requirements in a `closed ship' condition;
(4) Purge Cleansing Stations giving specified number of air changes per hour;
(5) Purge AirLocks giving specified number of air changes per hour; (6) Replenish oxygen levels and thereby keep CO2 content below maximum
permitted levels (See Section 9 Clause 9.4.3);
(7) Overcome the air lost from the citadel other than purging requirements. The amount of filtered fresh air required will therefore be the greater of the sum of 2 + 6 + 7 in an `open ship' condition or the sum of 1 + 3 + 4 + 5 + 6 + 7 in a `closed ship' condition.
Details of the above calculations are also shown in Section 9.
b. In machinery spaces, when required, under `closed down' conditions, sufficient fresh air is to be provided to compensate for known controlled losses and calculated uncontrolled leakages while maintaining a differential pressure of approximately 3 millibars (mbars) relative to the external atmosphere.
