Heat Exchanger Tube Bundle – Fixed, U-Tube & Floating Head | Custom Replacement

Product Specification

Tube Bundle as the Primary Heat Transfer Assembly

A tube bundle is the core heat transfer assembly of a shell and tube heat exchanger. It consists of tubes, tube sheets, baffles or support plates, tie rods, spacers, and associated components. The bundle separates tube-side fluid from shell-side fluid and provides the heat transfer surface between the two streams.

A tube bundle can be supplied as a replacement bundle, spare bundle, or complete assembly for new heat exchangers. It is designed and manufactured per TEMA Class C, B, or R, ASME Section VIII Division 1 or Division 2, and GB/T 151 for domestic applications.

Tube Bundle Types – Structural Classification

Fixed Tube Sheet Bundle (TEMA L / M / N)

Tubes are fixed at both ends into stationary tube sheets. The tube sheets are welded or bolted to the shell. Thermal expansion is accommodated by an expansion joint on the shell when the temperature differential between tubes and shell exceeds the allowable limit for the material combination.

Typical application: clean shell-side fluids, moderate temperature differential, non-fouling service.

U-Tube Bundle (TEMA U)

Tubes are bent into a U-shape, and both ends are fixed to a single tube sheet. Each tube expands independently, so no shell expansion joint is required for large temperature differentials.

Typical application: high thermal differential, high-pressure gas service, hydrogen service, thermal shock conditions.

Limitation: individual tubes cannot be mechanically cleaned from the inside; chemical cleaning is required.

Floating Head Bundle (TEMA P / S / T / W)

One tube sheet is fixed, and the other is free to move with thermal expansion. The rear head is removable, allowing the bundle to be extracted for mechanical cleaning.

Typical application: severe fouling service, large temperature differential, high shell-side fouling factor.

Core Components – Specifications

Tubes

Tube Sheets

Baffles and Support Plates

Material Selection – Tubes and Tube Sheets

Tube Materials

Tube Sheet Materials

• Carbon steel SA-516 Gr.70 for non-corrosive tube-side fluids

• Stainless clad over carbon steel for corrosive service with high pressure; cladding thickness minimum 3 mm

• Solid stainless 304L / 316L for fully corrosive service

• Duplex or titanium for offshore and seawater service

• Alloy overlay such as Inconel 625 for severe sour or chloride service

Tube-to-Tubesheet Joint Types

Fabrication Process – Key Controls

Tube Sheet Drilling

• Drill bit size controlled to H11 tolerance per ISO 286

• Ligament deviation ≤ ±0.2 mm from drawing

• Hole surface finish Ra ≤ 1.6 μm for expanded joints

• All holes deburred on both faces and cleaned before tube insertion

Tube Expansion

• Hydraulic expansion pressure 160–220 MPa; hold time 5–8 seconds

• Expansion depth minimum 1.5 × tube OD or 2 × tube wall thickness into tube sheet

• Post-expansion gauge check: 100% of tubes accept a gauge ball 0.5 mm smaller than tube ID

• Pull-out test on first article per bundle

Tube-to-Tubesheet Welding

• GTAW process, automatic or manual

• Fillet leg height 1.5–2.0 mm for seal weld

• Full penetration weld root penetration ≥ 0.5 mm into tube wall

• 100% liquid penetrant testing per ASME VIII-1 UW-51

• Weld procedure qualified per ASME Section IX

Post-Weld Heat Treatment

• Required when carbon steel tube sheet thickness exceeds 38 mm

• Required when service contains wet H₂S per NACE MR0175 / ISO 15156

• Typical PWHT cycle: 620°C ± 10°C, hold 1 hour per 25 mm thickness, minimum 1 hour

• Controlled cooling rate ≤ 50°C/hour to 400°C

Inspection and Testing Per Bundle

Dimensional Check

Non-Destructive Examination

• Tube-to-tubesheet welds: 100% liquid penetrant testing per ASME VIII-1 UW-51

• Tube sheet cladding: 100% ultrasonic testing for bond integrity per ASME VIII-1 UW-13

• Tube internal surface: Borescope inspection on random sample; 100% of tubes pass gauge ball

• Finned tubes, if applicable: Visual inspection for loose or missing fins

Pressure Testing

• Hydrostatic test: 1.3 × design pressure per ASME VIII-1 UG-99

• Hold time: minimum 30 minutes

• Acceptance: zero pressure drop and no visible leakage

• Pneumatic leak test if specified: 0.6 MPa air or nitrogen; soap bubble detection

• Leakage rate acceptance: ≤ 1×10⁻⁵ Pa·m³/s per equivalent orifice method

Documentation Per Shipment

• Material test certificates per EN 10204 3.1 or 3.2

• ASME U-stamp data report if applicable

• TEMA datasheet completed per design

• Dimensional inspection report

• Hydrostatic test report with pressure recording chart

• NDE reports for PT, UT, RT, or VT as performed

• Weld procedure specification and procedure qualification record

• Tube bundle as-built drawing

• Tube pull-out test report for first article

• Packing list with bundle shipping dimensions and weight

Selection Checklist – Tube Bundle

1. TEMA type – Fixed tube sheet / U-tube / Floating head

2. Shell inside diameter and tube sheet diameter

3. Tube OD, wall thickness, and length

4. Tube pitch and arrangement – Triangular / Square

5. Tube material and tube sheet material

6. Tube-to-tubesheet joint type – Expanded / Welded / Combined

7. Design pressure for tube side and shell side

8. Design temperature for tube side and shell side

9. Fluid composition for both sides – to verify material compatibility

10. Corrosion allowance for tubes and tube sheet

11. Baffle type and spacing – based on allowable pressure drop and vibration criteria

12. NDE and testing requirements per project specification

13. PWHT requirement based on material and service

14. Quantity – replacement bundle, spare bundle, or new equipment

Design Limitation Statement – Tube Bundle

The tube bundle is subject to the following limitations:

• It must match the shell geometry, tube sheet dimensions, and flange pattern of the existing heat exchanger.

• It is not rated for internal pressure until assembled with the shell, channels, and flanges.

• Tube-side solids content above 2% by weight is not recommended without upstream filtration, due to erosion and tube blockage risk.

• Expanded-only joints are not recommended for thermal cycling above 500 cycles per year or for toxic service.

• U-tube bundles cannot be mechanically cleaned inside the tubes; chemical cleaning is required.

• Fixed tube sheet bundles may require a shell expansion joint when the temperature differential exceeds the allowable limit.

• For vacuum service below 1 kPa absolute, additional stiffening or support may be required per ASME VIII-1 UG-29.

• Hydrotest water for austenitic stainless steel must have chloride content ≤ 50 ppm to prevent stress corrosion cracking.