Lord Fin Tube--Titanium Tube Sheet and Low Finned Tube
Technical Tender Announcement: Manufacturing of a New Tube Bundle for Oil & Gas Heat Exchanger
This document details the comprehensive requirements for the design, fabrication, testing, and supply of a replacement tube bundle destined for a critical heat exchanger within the oil and gas sector. The project demands adherence to the highest industry standards to guarantee performance, corrosion resistance, and durability in challenging operational environments.
Titanium Tube Sheet in Heat Exchangers
What is the primary role of a tube sheet in a shell and tube heat exchanger? It acts as the foundational component, securely holding the ends of the tubes in place and creating a pressure boundary between the tube side and shell side fluids. The material selection for this part is critical for long-term reliability.
Key Specifications for Titanium Tube Sheets (per Tender)
| Parameter | Specification | Rationale for Specification |
|---|---|---|
| Material Standard | ASTM B265 / SB 338 Grade 2 | This grade offers an optimal balance of strength, weldability, and exceptional corrosion resistance, crucial for sour service. |
| Thickness | 70 mm (±0.5 mm) | Provides necessary structural integrity for high-pressure differentials and tube rolling/expanding operations. |
| Surface Finish (Ra) | ≤ 3.2 µm | A smooth finish ensures effective gasket sealing, preventing inter-pass leakage which is vital for exchanger efficiency. |
| Flatness Tolerance | ≤ 0.1 mm/m² | Prevents stress concentrations during assembly and ensures uniform tube loading, extending bundle life. |
How does titanium compare to alternatives like carbon steel or stainless steel for tube sheets in this application? Titanium provides superior resistance to chloride-induced stress corrosion cracking (SCC) and hydrogen sulfide (H₂S) attack, common in oil and gas streams. This significantly reduces maintenance downtime and lifecycle costs.
Low Finned Tube Technology
When should a procurement specialist consider Low Finned Tubes over smooth tubes? The decision hinges on the need for enhanced heat transfer efficiency within a fixed footprint. Low finned tubes increase the external surface area, which is particularly beneficial when the shell-side fluid has a lower heat transfer coefficient.
Which manufacturing processes are involved in producing low finned tubes? High-quality low finned tubes are typically created through an integral finning process, such as cold rolling or extrusion, which forms the fins from the base tube material. This ensures excellent thermal contact and mechanical integrity between the fin and the tube wall.
Procurement Insight: When evaluating low finned tube suppliers, request details on their fin formation method and quality control for fin height and thickness consistency. Inconsistent fins can lead to uneven flow distribution and reduced performance.
The tender specifies seamless titanium (SB 338 Grade 2) for the low finned tubes. Seamless construction is often preferred for high-pressure duties as it eliminates the longitudinal weld, a potential point of weakness under cyclic loading.
Detailed Scope of Work & Component Analysis
The complete tube bundle assembly consists of several key components, each with precise requirements.
2.1 Tube Sheets (Titanium Grade 2)
Material: ASTM B265 Grade 2 Titanium.
- Why is Titanium Grade 2 specified? It is the most widely used commercially pure titanium grade, known for excellent formability, corrosion resistance, and suitability for welding.
- Dimensions:
- Thickness: 70 mm (±0.5 mm tolerance)
- Diameter: 915 mm (Qty: 1) & 810 mm (Qty: 1)
- Machining Requirements: Precision hole drilling is critical for tube fit. Final hole pattern, ligament width, and hole finish will be per the approved machining drawings.
2.2 Low-Finned Tubes (Seamless Titanium)
Material: SB 338 Grade 2 Seamless Titanium.
- Why are low-finned tubes specified for this application? To maximize heat transfer in a condenser or cooler where the shell-side fluid is the limiting factor. The fins increase turbulence and surface area.
- Dimensions:
- OD: 19.05 mm (±0.1 mm)
- Wall Thickness: 2.3 mm (Minimum)
- Length: 6,750 mm (±5 mm)
- Quantity: 750 pieces.
- Fin Specifications:
- Fins per Meter: 1,024
- Fin Height: 1.5 mm (±0.05 mm)
- Fin Thickness: 0.27 mm (±0.02 mm)
- Unfinned Ends: 80 mm at both ends for expansion/welding into tube sheets.
2.3 – 2.6 Bundle Internals
Support Plates, Baffle Plates (29 Nos., segmental cut), Support Rods, and Sealing Strips are all fabricated from Titanium Grade 2. Their primary functions are to provide structural support, direct shell-side flow for optimal heat transfer, and prevent fluid bypass, respectively. Dimensional accuracy is paramount for proper assembly.
Manufacturing and Quality Assurance Protocol
What quality documentation should a purchaser expect? Full traceability via Mill Test Certificates (MTC) for all titanium raw materials, validating chemical composition and mechanical properties against ASTM/SB standards.
| Process Stage | Key Activities | Relevant Standards / Notes |
|---|---|---|
| Material Certification | Review of MTCs, material identification tracking. | ASTM B265, SB 338. Verify heat numbers. |
| Fabrication | CNC drilling of tube sheets, precision fin rolling of tubes, GTAW (TIG) welding. | Weld Procedure (WPS) & Performance Qualification (WPQR) records required. |
| Non-Destructive Testing (NDT) | UT for tube sheets, Eddy Current Testing (ECT) for tubes, DPI for welds. | ASME BPVC Section V. ECT detects surface/sub-surface flaws in finned sections. |
| Final Inspection | Dimensional check, hydrostatic test, bundle assembly verification. | Per approved drawings and TEMA standards. Third-party inspection may be invoked. |
Delivery and Packaging Requirements
Packaging must prevent damage and corrosion during transit. Tube sheets and plates require wooden crates with protective VCI (Vapor Corrosion Inhibitor) coating. Individual low finned tubes should be sleeved in protective plastic and bundled securely to prevent bending or fin damage. All shipping must comply with international freight standards, with INCOTERMS to be specified in the final purchase order.