AS 2593-1995

1 - AS 2593-1995 BOILERS-UNATTENDED AND LIMITED ATTENDANCE
4 - PREFACE
5 - CONTENTS
7 - SECTION 1 SCOPE AND GENERAL
7 - 1.1 SCOPE
8 - 1.2 REFERENCED DOCUMENTS
8 - 1.3 DEFINITIONS
8 - 1.3.1 Acceptable, acceptance, accepted
8 - 1.3.2 Authority having jurisdiction
8 - 1.3.3 Bed
8 - 1.3.4 Bed warm-up gas
8 - 1.3.5 Boilers
10 - 1.3.6 Boiler management system
10 - 1.3.7 Accredited boiler attendant
10 - 1.3.8 Chimney
10 - 1.3.9 Complete shutdown
10 - 1.3.10 Double block and vent safety shut-off system
11 - 1.3.11 Energy input management system
11 - 1.3.12 Fail-safe
11 - 1.3.13 Flame detector
11 - 1.3.14 Flame establishment period
11 - 1.3.15 Flame failure
11 - 1.3.16 Flame-proving period
11 - 1.3.17 Flame simulation
11 - 1.3.18 Flame supervision system
11 - 1.3.19 Flue
11 - 1.3.20 Fuel safety shut-off system
11 - 1.3.21 Ignition failure
11 - 1.3.22 Ignition spark period
11 - 1.3.23 Interlock
11 - 1.3.24 Interrupted pilot
11 - 1.3.25 Leakage detection system
11 - 1.3.26 Lockout
11 - 1.3.27 Maintenance contract
12 - 1.3.28 Main fuel
12 - 1.3.29 Maintenance contractor
12 - 1.3.30 Manufacturer
12 - 1.3.31 May
12 - 1.3.32 Overbed flame
12 - 1.3.33 Pilot
12 - 1.3.34 Owner
12 - 1.3.35 Power output
12 - 1.3.36 Proved
12 - 1.3.37 Purging
12 - 1.3.38 Regulatory Authority
12 - 1.3.39 Self-checking system
12 - 1.3.40 Shall
12 - 1.3.41 Should
12 - 1.3.42 Start gas flame
12 - 1.3.43 Supplementary fuel
12 - 1.3.44 Trained person
12 - 1.4 NEW DESIGNS, MATERIALS AND CONSTRUCTION METHODS
13 - SECTION 2 DESIGN AND CONSTRUCTION
13 - 2.1 GENERAL REQUIREMENTS
13 - 2.1.1 Basic design
13 - 2.1.2 Water gauges
13 - 2.1.3 Tube diameter
13 - 2.2 STEAM BOILERS (OTHER THAN ELECTRIC BOILERS)
13 - 2.2.1 General
13 - 2.2.2 Water-tube steam boilers
13 - 2.2.3 Steam boilers other than water-tube or electric boilers
13 - 2.3 HOT WATER BOILERS
13 - 2.3.1 General
14 - 2.3.2 Hot water systems
14 - 2.4 WASTE HEAT BOILERS
14 - 2.5 ELECTRIC BOILERS
14 - 2.6 SUPERHEATERS
15 - SECTION 3 BOILER MANAGEMENT SYSTEM
15 - 3.1 GENERAL
15 - 3.2 FAIL-SAFE TECHNIQUES
15 - 3.3 TEMPERATURE SUITABILITY OF COMPONENTS
15 - 3.4 COMBUSTION MANAGEMENT
15 - 3.4.1 General
15 - 3.4.2 Power-operated valves
16 - 3.4.3 Flame detectors
16 - 3.5 WATER MANAGEMENT SYSTEMS
16 - 3.5.1 For steam boilers other than coil-type forced circulation boilers and electric boilers
17 - 3.5.2 Water management systems for coil-type forced circulation boilers
18 - 3.5.3 Water management systems for hot-water boilers
18 - 3.5.4 Water management systems for waste heat boilers
18 - 3.5.5 Water management systems for electric boilers
20 - 3.6 ELECTRICAL POWER ISOLATION
20 - 3.7 POWER FAILURE PROTECTION
20 - 3.7.1 Design and construction
20 - 3.7.2 Hazard of overheating
20 - 3.8 CONTROL EQUIPMENT
21 - 3.9 ALARMS
21 - 3.10 VISUAL DISPLAY
21 - 3.10.1 General
21 - 3.10.2 Fuel-fired boilers
21 - 3.10.3 Water level security
22 - 3.11 COMBUSTION EQUIPMENT FOR FUEL-FIRED BOILERS
22 - 3.11.1 General
22 - 3.11.2 Alternative firing of main fuels
22 - 3.11.3 Alternative firing of main fuels, fluidized bed combustion boilers
22 - 3.11.4 Supplementary fuel firing
23 - 3.11.5 Combustion characteristics
23 - 3.11.6 Secure mounting
24 - 3.11.7 Adverse conditions
24 - 3.11.8 Visual flame-checking provisions
24 - 3.12 MULTIPLE-BURNER INSTALLATIONS
24 - 3.13 AIR SUPPLY AND CONTROL SYSTEM
24 - 3.13.1 General
24 - 3.13.2 Air inlets
24 - 3.13.3 Proportioning
24 - 3.14 IGNITION SYSTEM
24 - 3.14.1 Start flame or pilot ignition
24 - 3.14.2 Ignition electrodes
24 - 3.14.3 High tension components
24 - 3.14.4 Location and fixing
25 - 3.14.5 Start gas rate
25 - 3.14.6 Main burner to start at a reduced rate
25 - 3.15 MAIN FUEL FIRING RATE
25 - 3.15.1 Low-fire rate operation
26 - 3.15.2 Low-fire interlock
26 - 3.15.3 Main flame turn down and modulation
26 - 3.15.4 Main flame firing rate
27 - SECTION 4 ADDITIONAL REQUIREMENTS FOR OIL-FIRED, GAS-FIRED AND SOLID-FUEL-IN-SUSPENSION-FIRED BOILERS
27 - 4.1 APPLICATION
27 - 4.2 OPERATIONAL REQUIREMENTS FOR OIL, GAS AND SOLID-FUEL-IN-SUSPENSION MANAGEMENT SYSTEMS
27 - 4.2.1 Pre-start safety interlocks
27 - 4.2.2 Starting and operating sequence
28 - 4.2.3 Fault shutdown condition for other than forced circulation boilers
28 - 4.2.4 Fault shutdown sequence for a forced circulation boiler
29 - 4.2.5 Purging
29 - 4.2.6 Flame simulation
29 - 4.2.7 Fuel admission
29 - 4.2.8 Spark ignition period
29 - 4.2.9 Flame establishment period for spark ignition
30 - 4.2.10 Start-flame proving
30 - 4.2.11 Main flame establishment period for start flame ignition
30 - 4.2.12 Ignition failure
30 - 4.2.13 Flame failure response
30 - 4.2.14 Controlled shutdown
30 - 4.3 SPECIFIC REQUIREMENTS FOR OIL-FIRED BOILERS
30 - 4.3.1 Oil fuel pretreatment
30 - 4.3.2 Gas pilot
30 - 4.3.3 Controls and safety devices
31 - 4.3.4 Fuel bypass valve
31 - 4.3.5 Steam-atomized burners
31 - 4.3.6 Fuel oil installation
31 - 4.4 SPECIFIC REQUIREMENTS FOR GAS-FIRED BOILERS
31 - 4.4.1 General
31 - 4.4.2 Controls and safety devices
32 - 4.4.3 Valve trains
32 - 4.4.4 Double block and vent system
33 - 4.4.5 Premix gas burners
33 - 4.5 SPECIFIC REQUIREMENTS FOR SOLID-FUEL-IN-SUSPENSION-FIRED BOILERS
33 - 4.5.1 General
33 - 4.5.2 Controls and safety devices
34 - 4.5.3 Valve and piping arrangement
34 - 4.5.4 Fuel quality
35 - SECTION 5 ADDITIONAL REQUIREMENTS FOR SOLID-FUEL-FIRED (BED OR GRATE) BOILERS
35 - 5.1 APPLICATION
35 - 5.2 OPERATIONAL REQUIREMENTS FOR SOLID FUEL (BED OR GRATE) MANAGEMENT SYSTEMS
35 - 5.2.1 Pre-start interlocks
35 - 5.2.2 Start-up
35 - 5.2.3 Controlled shutdown
36 - 5.2.4 Fault shutdown
36 - 5.2.5 Purging
36 - 5.3 SPECIFIC REQUIREMENTS FOR SOLID-FUEL-FIRED (BED OR GRATE) BOILERS
36 - 5.3.1 General
36 - 5.3.2 Fuel quality
36 - 5.3.3 Combustion equipment
36 - 5.3.4 Ignition of bed fuel
36 - 5.3.5 Controls and safety devices
36 - 5.3.6 Burn-back protection
37 - 5.3.7 Power failure protection
37 - 5.3.8 Solid fuel and residue handling plant
38 - SECTION 6 INSTALLATION
38 - 6.1 STATUTORY REQUIREMENTS
38 - 6.1.1 Gas installations
38 - 6.1.2 Fuel oil installations
38 - 6.1.3 Solid fuel installations
38 - 6.1.4 Electrical installations
38 - 6.2 HOUSING, ACCESS AND SECURITY
38 - 6.3 FEEDWATER SUPPLY
38 - 6.4 WATER TREATMENT
38 - 6.5 BLOWDOWN
38 - 6.6 FLUES AND CHIMNEYS
39 - SECTION 7 MARKING AND INSTRUCTIONS
39 - 7.1 MARKING
39 - 7.2 ELECTRICAL DATA
39 - 7.3 INSTRUCTIONS
39 - 7.4 LANGUAGE AND UNITS
39 - 7.5 CERTIFICATES
40 - SECTION 8 CHECKING, TESTING AND MAINTENANCE
40 - 8.1 GENERAL
40 - 8.2 ORGANIZATION AND PERSONNEL
40 - 8.3 RESPONSIBILITIES
40 - 8.3.1 Program and procedures
40 - 8.3.2 Daily and weekly checking
40 - 8.3.3 Periodic and yearly testing and maintenance
40 - 8.4 CHECKING AND TESTING
40 - 8.4.1 Limited attendance supervision
41 - 8.4.2 Daily checking
41 - 8.4.3 Weekly checking
41 - 8.4.4 Periodic testing
42 - 8.4.5 Changes to procedures
42 - 8.4.6 Recording
42 - 8.5 MAINTENANCE
42 - 8.5.1 Periodic maintenance
42 - 8.5.2 Yearly maintenance
43 - 8.5.3 Records
43 - 8.6 RETENTION OF RECORDS
43 - 8.7 MAINTENANCE CONTRACT
43 - 8.7.1 General
43 - 8.7.2 Scope of contract
43 - 8.7.3 Termination of contract
44 - APPENDIX A - LIST OF REFERENCED DOCUMENTS
45 - APPENDIX B - GUIDELINES FOR APPROVAL OF ORGANIZATIONS AND PERSONNEL FOR BOILER CONTROL DESIGN, TESTING AND SERVICING
45 - B1 GENERAL
45 - B2 ORGANIZATION, QUALIFICATIONS AND EXPERIENCE
45 - B3 MINIMUM QUALIFICATIONS FOR PERSONNEL
45 - B3.1 Design agent
46 - B3.2 Installation agent
46 - B3.3 Commissioning agent
47 - B3.4 Servicing
48 - APPENDIX C - TYPE TEST FOR A BOILER SUBJECT TO POWER FAILURE
48 - C1 GENERAL
48 - C2 TYPE TEST
48 - C3 TEST PROCEDURE
48 - C4 ACCEPTANCE CRITERIA
49 - APPENDIX D - TYPICAL OIL OR GAS BURNER FIRING SEQUENCES
50 - APPENDIX E - TYPICAL OIL SUPPLY AND CONTROL SYSTEMS
52 - APPENDIX F - TYPICAL GAS SUPPLY AND CONTROL SYSTEMS

Specifies the limits of boiler attendance categories as given in Amendment No.1 to the 1990 edition, together with the extension of the maximum capacity of small low-hazard boilers to 500 kW. It clearly defines the personnel that are involved in the design, installation, commissioning and maintenance of control systems and boilers. Safety is an overriding factor of this Standard and emphasizes the reliable system of control operations.

This Standard specifies requirements for unattended and limited attendance boilers which are intended to be operated for periods without human supervision. It includes special features within the control, management and supervision systems, associated valves and fittings, housing and installation, as well as requirements and responsibilities for checking, testing and maintenance of these boilers.The limits on the type, design criteria, and usage of unattended and limited attendance boilers to which this Standard is intended to apply are as follows:(a) Boilers for fixed land installations.(b) Boilers having a design pressure as shown in Table 1.1.(c) Boilers having a power output within the capacity specified in Table 1.1 for the boiler type and category. (See Note 1.)(d) Boilers complying with the supervision and maintenance requirements specified in Table 1.1 for the boiler type and category.(e) Boilers for the generation of steam, or other vapour, for which duty the types of boilers permitted are -(i) water-tube type electric type or low hazard type (see Table 1.1) for unattended operation; and(ii) any type of boiler for limited attendance operation (see Table 1.1).(f) Boilers for the heating of water or other liquids at a pressure above that of the atmosphere and to a temperature not less than the normal atmospheric boiling temperature of the liquid, for which duty any type of boiler complying with AS 1228 or AS 1797 is permitted for unattended operation, provided that for other than water-tube and electric type boilers, steam or vapour is not generated in the boiler and the boiler drum or shell is fully flooded.(g) Boilers having any of the following sources of energy input:(i) Gas fuel (mains or other gases).(ii) Oil fuel with a closed flashpoint greater than 23C. (iii) Solid fuels, including solid-fuel-in-suspension.(iv) Waste heat fluids.(v) Electric power.NOTES:1 This Standard may also be applied to boilers outside the limits specified in Items (a) to (g) in Clause 1.1 where equivalent safety and reliability are ensured and the boiler and its installation are acceptable to the regulatory authority. Current requirements of some regulatory authorities may vary from the criteria given in Table 1.1.2 Except for definitions in Clause 1.3, other clauses in the Standard refer to steam and water only. It is intended that the Standard may be applied to other fluids subject to acceptance by and compliance with any additional safety features required by the regulatory authority.

First published as AS 2593-1983.
Second edition 1990.
Third edition 1995.