Erecting and Assembling Boilers and Pressure Vessels
Chapter Introduction
This chapter covers the erection, assembly, and installation of boilers and pressure vessels in accordance with the requirements of the Canadian Electrical Code, Part I (CE Code) (for electrical aspects) and the CSA B51 Code (Boiler, Pressure Vessel, and Pressure Piping Code). You must master lifting procedures, alignment, field welding, pressure testing, and required documentation. Exam questions often focus on tolerances, assembly sequences, and the legal responsibilities of the journeyperson boilermaker.
Applicable Standards and Codes
CSA B51-19 — Boiler, Pressure Vessel, and Pressure Piping Code
This standard is the primary reference in Canada for design, fabrication, inspection, and testing. It adopts by reference the ASME Boiler and Pressure Vessel Code (Section I for boilers, Section VIII for vessels) , but adds specific Canadian requirements, including:
Registration of drawings with provincial authorities (although the Red Seal exam is interprovincial, you must know that each province requires plan approval before work begins).
Inspection requirements during fabrication (authorized inspector).
Mandatory pressure tests before commissioning.
CSA B149.1 — Natural Gas and Propane Code
Applies to burners and gas piping connected to boilers. Rule 6.22 specifically addresses burner installation and ventilation requirements.
Canadian Electrical Code, Part I (CE Code)
Applies to electrical connections for electric boilers and controls. Rule 8-200 defines the sizing requirements for supply conductors.
Site Preparation and Equipment Receiving
Receiving Inspection
Before any lifting, you must perform a complete visual inspection of the boiler or vessel upon its arrival at the site. This inspection includes:
17.Conformity verification: compare the nameplate (serial number, design pressure, design temperature) with the approved drawings and the purchase order.
18.Transport damage inspection: look for dents, deformations, cracks in welds, damaged supports, and warped flanges.
19.Internal integrity check: if openings permit, inspect the interior for debris, corrosion, or damage to tubes.
20.Document control: CSA B51 certificate of compliance, factory test reports, material certificates (mill sheets), and certified drawings.
> Important for the exam: If damage is found, you must document it in writing and immediately notify the supervisor and the manufacturer. NEVER attempt to repair structural damage without written authorization from the engineer.
Foundation Preparation
The foundation must be verified before erection. Typical tolerances are:
Parameter
Allowable Tolerance
Foundation levelness
± 3 mm over 3 meters
Horizontal position (axes)
± 6 mm from drawings
Foundation top elevation
± 6 mm
Anchor bolt alignment
± 3 mm between centers
Anchor bolts must be checked for:
Their position (deviation from drawings)
Their plumbness (maximum 1:100)
Their threads (must be clean and clear)
Their protrusion above the foundation (must allow installation of the nut and washer with at least 2 threads visible after tightening)
Lifting and Rigging
Lifting Equipment
The choice of crane depends on the weight, dimensions, and required reach. You must know:
The crane's rated capacity (at the given radius and configuration)
The safety factor: minimum 1.5 for lifting loads with steel slings, 2.0 for synthetic slings
Sling angles: the angle between the sling and the vertical must not exceed 60°. At 60°, the tension in each sling equals the weight of the load (for two symmetrical slings).
Calculating tension in a sling:
T = (Load weight × Safety factor) / (Number of slings × cos(angle from vertical))
Example: 10,000 kg load, 4 slings, 45° angle from vertical, safety factor 1.5.
T = (10,000 × 1.5) / (4 × cos 45°) = 15,000 / (4 × 0.707) = 15,000 / 2.828 = 5,304 kg
Each sling must have a capacity of at least 5,304 kg.
Lifting Points
Lifting lugs are installed at the factory on boilers. If you must install additional lifting points in the field:
They must be designed by an engineer (strength calculation)
They must be welded by a qualified welder according to the approved procedure (WPS)
The weld must be inspected (visually at minimum, by dye penetrant or magnetic particle testing as required)
Lifting Procedure
48.Lift plan: a written lift plan is required for any load over 2,000 kg or when the load must pass over personnel.
49.Test lift: lift the load 150 mm, check balance and stability, then lower.
50.Guidance: use tag lines to control rotation.
51.Communication: only one signaler must direct the crane operator, using standardized signals.
Alignment and Assembly
Aligning Boiler Sections
For large boilers shipped in sections, alignment is critical. Typical tolerances are:
Element
Tolerance
Adjacent plate alignment (maximum offset)
3 mm or 25% of thickness, whichever is less
Nozzle alignment
± 1.5 mm on position
Perpendicularity of drum axis to supports
1 mm per meter
Upper drum levelness
± 3 mm over entire length
Alignment Techniques
Hydraulic jacks: for fine adjustments (precision of ± 0.5 mm)
Come-alongs: for coarse adjustments
Positioning brackets: temporarily welded to plates
Alignment lasers: for aligning nozzles and drums
> Exam trap: Temporary positioning devices (tack welds, brackets) must be removed and the areas ground flush after final assembly. Do not leave them in place.
Assembling Plate Joints
Joints between shell sections are generally:
64.Lap joints: plates overlap. Used for low-pressure vessels.
65.Butt joints with bevel: plates are aligned and welded with a V, U, or double-V preparation. This is the most common type for boilers and pressure vessels.
Edge preparation (bevel) must follow the qualified welding procedure (WPS). Typical dimensions for a single V-bevel are:
Included angle: 60° ± 5°
Root face: 1.5 to 2.5 mm
Root gap: 2 to 4 mm
Field Welding
Welder Qualification
Each welder must be qualified according to CSA W47.1 (certification of welding companies) and CSA W47.2 (welder qualification). Qualifications are specific to:
Welding position (flat, horizontal, vertical, overhead)
Process (SMAW, GTAW, FCAW, SAW)
Base material (carbon steel, alloy steel, stainless steel)
Material thickness
Joint type
Welding Procedure Specification (WPS)
The WPS must be approved and available on site. It specifies:
The typical preheat temperature for carbon steel is 100 °C to 150 °C. It must be verified with an infrared thermometer or temperature indicating crayons at a maximum distance of 75 mm from the joint.
Vessels subject to severe service conditions (fatigue, creep)
PWHT involves heating the vessel to a temperature of 595 °C to 675 °C for carbon steel, holding this temperature for one hour per 25 mm of thickness (minimum 1 hour), then cooling slowly.
Pressure Testing
Types of Tests
Test Type
Pressure
Fluid
Application
Hydrostatic test
1.3 × design pressure (minimum)
Water
All vessels
Pneumatic test
1.1 × design pressure
Air or inert gas
Only if hydrostatic testing is impossible
Leak test
Service pressure
Air or gas
Joints and flanges only
Hydrostatic Test — Procedure
103.Filling: completely fill the vessel with water, purging all air through top vents.
104.Pressure increase: increase pressure gradually in increments of 25% of the test pressure, with stops for inspection.
105.Hold: maintain the test pressure for at least 30 minutes (or longer per specifications).
106.Inspection: at test pressure, inspect all welds, flanges, and joints for leaks.
107.Depressurization: release pressure slowly.
Hydrostatic test pressure:
P_test = 1.3 × P_design × (S_test / S_design)
Where S_test is the allowable stress at test temperature and S_design is the allowable stress at design temperature. To simplify, if the test temperature is lower than the design temperature, S_test > S_design, so the test pressure may be higher than 1.3 × P_design.
> Exam trap: The test pressure must never exceed 1.5 × P_design, even if the calculation gives a higher value, unless written authorization from the engineer is obtained.
Test Water Temperature
Test water must be at a minimum temperature of 16 °C (or 10 °C above the material's ductile-to-brittle transition temperature, whichever is higher). This is crucial to avoid brittle fracture.
Pneumatic Test — Precautions
Pneumatic testing is dangerous because the stored energy is much greater than with water. Precautions include:
Delineated safety zone (security perimeter)
Non-essential personnel evacuated
Remote inspection (mirrors, cameras)
Pressure increase in increments of 10% with stability verification
Installing Supports and Anchors
Types of Supports
Type
Description
Application
Skirt support
Cylindrical support welded to the vessel bottom
Vertical vessels
Saddles
Saddle-shaped supports
Horizontal vessels
Leg supports
Welded or bolted legs
Small vessels
Lug supports
Lateral supports
Vessels mounted on structures
Saddle Installation Rules
For a horizontal vessel on two saddles:
The fixed saddle (anchored) must be placed on the side of fixed connections (rigid piping side)
The sliding saddle (on slide plates) must allow for thermal expansion
Number of saddles: 2 maximum for most vessels. A third saddle creates hyperstaticity that can cause excessive stresses.
Thermal Expansion
The thermal expansion of carbon steel is approximately 12 × 10⁻⁶ mm/mm/°C. For a 10-meter boiler heated from 20 °C to 200 °C:
ΔL = 12 × 10⁻⁶ × 10,000 mm × 180 °C = 21.6 mm
This expansion must be absorbed by:
Sliding supports (slide plates)
Expansion joints in piping
Expansion loops
Piping Connections
Pressure Piping Requirements
Piping connected to boilers and vessels must comply with CSA B51 and ASME B31.1 (Power Piping) for boilers, or ASME B31.3 (Process Piping) for vessels.
Flanges and Gaskets
Flanges are classified by pressure rating (class):
Flange Class
Maximum Pressure at 38 °C (bar)
150
19.6
300
51.1
600
102.1
900
153.3
1500
255.3
2500
425.5
Flange bolt tightening must be done in a cross (star) pattern, in successive passes:
142.First pass: tighten to 30% of final torque
143.Second pass: tighten to 60%
144.Third pass: tighten to 100%
145.Fourth pass: verify all bolts at final torque
Gasket Countermeasures
Flange faces must be clean and free of scratches
The gasket must be centered and of the correct size
Never reuse a metallic or spiral-wound gasket
Rubber or PTFE gaskets may be reused if undamaged (but this is not recommended)
Documentation and Traceability
Documents Required on Site
Document
Content
Certified drawings
Drawings approved by the competent authority
CSA B51 certificate
Manufacturer's certificate of compliance
Factory test reports
Pressure tests, non-destructive testing
WPS and PQR
Welding procedures and qualification records
Welder certificates
Welder qualifications on site
Weld log
Location and identification of each weld
Inspection reports
Inspections performed during erection
Weld Log
Each field weld must be identified by a unique number, marked (stamped or tagged), and recorded in the log with:
