BS 855:1990

Committees responsible
Foreword
Specification
Section one. General
1.1 Scope
1.2 Definitions
1.3 Performance
1.4 Design pressures and flow temperatures
Section two. Materials and design stresses
2.1 Materials
2.2 Design stress
Section three. Design
3.1 General
3.2 Cylindrical shells subject to internal pressure
3.3 Dished and flanged ends
3.4 Standpipes and branches
3.5 Manhole and sighthole openings
3.6 Stays, stiffeners and supported surfaces
3.7 Tubes and tube plates
3.8 Cylindrical furnaces and combustion chambers
      subject to external pressure
3.9 Fireboxes
Section four. Manufacturer and workmanship
4.1 Pressure parts
4.2 Welding
4.3 Dampers, doors and observation ports
4.4 Ashpits
4.5 Inspection and cleaning holes
4.6 Provisions for mountings, appliances and
      connections
4.7 Assembly of boiler
Section five. Mountings and fittings
5.1 Safety valves
5.2 Vent pipes
5.3 Emptying valves or cocks
5.4 Pressure gauges
5.5 Temperature gauges
5.6 Inspector's test gauge connection
5.7 Water-level gauges
5.8 Water-level alarms, fuel cut-outs and fusible
      plugs
5.9 Connection pipes for water-level fittings
5.10 Feed-water valves
5.11 Blowdown
5.12 Stop valves
Section six. Combustion equipment
6.1 General
6.2 Solid fuel firing
6.3 Liquid fuel firing
6.4 Gas firing
Section seven. Automatic controls and electrical
installation
7.1 Automatic controls for steam and hot water boilers
Section eight. Inspection and marking
8.1 Inspection
8.2 Hydraulic test
8.3 Marking
Appendices
A. Installation provisions
B. Electrical installation
C. Categories of boilers
D. Information to be supplied by the manufacturer
E. Information to be supplied by the purchaser
Tables
1. Design pressures, flow temperatures and outputs
2. Design stress f
3. Minimum thickness of shells subject to internal
      pressure
4. Values of z for welded longitudinal seams
5. Tapped opening: minimum thickness of plate
6. Values of constant K5
7. Weld attachments
8. Number of bar stays in vertical boilers
9. Minimum thickness of plain tubes subject to
      internal or external pressure
10. Minimum thickness of cylindrical shells subject
      to external pressure
11. Dimensions of manholes and inspection holes
12. Tapping sizes for safety valves
13. Sizes of safety valves (open vented systems only)
14. Tapping sizes for vent pipes
15. Minimum open vent pipe sizes
Figures
1. Maximum diameter of unreinforced openings
2. Compensation of welded branches or standpipes
3. Compensated set-through branches
4. Typical method of attachment of ash drop-out tube
5. Fillet-welded studded connections
6. Typical methods of welding manhole frame and
      compensating plates
7. Typical dished ends
8. Shape factor
9. Opening in ends
10. Limits of reinforcement
11. Flanges
12. Angle rings
13. Set-trough branches up to 150 mm o.d. branch
14. Set-in branches: full penetration connections
15. Set-through branches
16. Typical screwed connections
17. Welding details for compensated openings in flat
      end plates
18. Typical arrangement of end plates on single
      furnace economic boilers
19. Access openings for wet-back boilers
20. Attachment of unflanged flat end plates to
      cylindrical shells
21. Attachment of dished or flat flanged end plates
      to cylindrical shells and furnaces
22. Typical arrangement of end plates on multitubular
      boilers
23. Bar stays
24. Attachment of longitudinal bar stays
25. Plate stays
26. Plus-welded firebox or water-leg stays
27. Detail of mild steel anchor stays
28. Attachment of dished or flat flanged end plates
      to cylindrical shells
29. Attachment of flanged end plates to shell: ends
      thicker than shell
30. Attachment of flanged flat end plates to shell:
      shell thicker than ends
31. Attachment of end plates to reversal chamber of
      firebox wrapper plates
32. Typical details for all-welded gusset stays
33. Attachment between flat plates
34. Attachment of stay tubes to tube plates
35. Effective length L between centres of substantial
      support for fireboxes of vertical boilers
36. Stiffener for horizontal furnaces
37. Typical plate preparation for butt-welded
      longitudinal and circumferential seams
38. Attachment of plain tubes to tube plates
39. Fusion-welded oval manhole frames
40. Detail of furnace joints
41. Attachment of fireboxes to shells
42. Firehole mouthpieces and access openings
43. Welding of fluepipes
44. Fusion welds of cross tubes
45. Typical methods of fitting welded girders to
      welded combustion chambers and fireboxes
46. Butt-welded studded connections
47. Diagrammatic arrangement of water level and high
      steam pressure automatic controls and cut-outs for
      boilers fired with oil or gas complying with
      section six
48. Diagrammatic arrangement of water level and high
      steam pressure automatic controls and cuts-out
      for boilers fired with solid fuel complying with
      section six
49. Heating system categories

Requirements for the design and construction including materials, workmanship, inspection, testing and marking of boilers for use with solid, gaseous and liquid fuels.

1.1.1 This British Standard specifies requirements for the design and construction including materials, workmanship, inspection, testing and marking of welded steel boilers for central heating and indirect hot water supply for which the classification of design pressures, flow temperatures and outputs are given in table 1.

1.1.2 This standard applies to boilers for hot water or low pressure steam (see table 1), with rated heat output between 44 kW and 3 MW and for use with one or more of the following fuels:

1. smokeless solid fuels, e.g. furnace coke, low temperature coke or anthracite;
2. bituminous coal fired by means of mechanical stokers;
3. gaseous fuels of the 2nd and 3rd families (see BS 4947);

and for rated heat output between 300 kW and 3 MW when used with liquid fuels of the classes specified in BS 2869.

This standard also applies to hot water boilers pressurized by steam.

NOTE. The titles of the publications referred to in this standard are listed on page 89.