Why heat exchanger specs call for ASTM B338 GR1
Shell and tube heat exchangers have specific demands. Tubes must resist corrosion on both sides. They must roll into tube sheets without cracking. They must handle thermal cycling. They must last 20+ years with minimal maintenance.
ASTM B338 GR1 titanium tube meets all of these. The low oxygen content (0.18% max) gives high ductility for rolling and U-bending. The corrosion resistance handles seawater, brackish water, and aggressive chemicals.
For full technical specifications of ASTM B338 GR1 titanium tube, including size ranges and mechanical properties for heat exchanger service, see the product page here.
Tube dimensions for heat exchanger service
Heat exchanger tubes follow standard dimensional ranges. ASTM B338 GR1 is available in:
| Parameter | Typical range |
|---|---|
| Outside diameter | 12 mm to 50 mm (most common: 19 mm, 25.4 mm) |
| Wall thickness | 0.7 mm to 2.5 mm (most common: 1.24 mm, 1.65 mm) |
| Length | 3,000 mm to 15,000 mm straight |
| U-bend radii | 1.5x OD to 5x OD |
For high-pressure feedwater heaters, specify thicker walls (2.0 mm and above). For seawater condensers, thinner walls (1.0–1.2 mm) are common because corrosion allowance is not needed.
Seamless or welded for heat exchanger use
This question comes up on every project.
For most shell and tube heat exchangers, welded and drawn tubes work. Operating pressure is typically 150–300 psi. GR1 welded tubes handle this range without issue.
Specify seamless when:
Design pressure exceeds 500 psi
Tube wall is under 1.2 mm and will be rolled
U-bend radius is under 2.5x OD
Project specification explicitly requires seamless
For standard condensers and coolers, welded tubes save 30–50% with no performance difference.
More details in the seamless vs welded guide here.
Tube sheet rolling requirements
Rolling (expanding) titanium tubes into tube sheets requires attention to interference fit.
Recommended interference for GR1 tubes:
0.05 mm to 0.10 mm for standard service
0.10 mm to 0.15 mm for high-temperature or thermal cycling service
Do not use elastomeric gaskets between tube and tube sheet. These create crevices that trap process fluid. In warm chloride service, crevice corrosion starts at the gasket. Metal-to-metal rolling is the standard method.
For thin wall tubes (under 1.2 mm), seamless rolls more evenly than welded. The weld seam on welded tubes creates a slightly stiffer spot. With thin walls, this can cause uneven expansion.
U-bend specifications for heat exchangers
Floating head heat exchangers use U-bend tubes. GR1 is well suited for U-bends because of its high ductility.
Minimum bend radius for GR1 without annealing:
1.5x OD for seamless
2.5x OD for welded and drawn
When ordering U-bends, provide:
Tube OD and wall thickness
Centerline bend radius
Leg lengths (both sides)
Orientation of the bend plane
Flow velocity limits in heat exchanger service
Flow velocity affects both erosion and corrosion.
Minimum velocity: 1.5 m/s (5 ft/s) for seawater service. Below this, biofouling accumulates and crevice corrosion risk increases.
Maximum velocity: 5 m/s (16 ft/s) for clean fluids. Higher velocities can cause erosion at tube inlets, especially if sand or solids are present.
For water with suspended solids, reduce maximum velocity to 3 m/s. Use inlet end erosion protection (ferrules or tube end inserts) if solids are unavoidable.
Temperature limits for heat exchanger service
GR1 is suitable for continuous heat exchanger service from 0°C to 80°C (32°F to 176°F) in most fluids.
Above 80°C, two risks increase:
Crevice corrosion in chloride service
Creep strength reduction (irrelevant for pressure containment but relevant for tube sheet joint integrity)
For service above 80°C with chlorides, specify GR7 or GR12. These grades contain palladium or molybdenum and resist crevice corrosion up to 200°C.
For non-chloride service (clean water, steam, hydrocarbons), GR1 can be used up to 150°C without significant corrosion issues.
Common problems with GR1 tubes in heat exchangers
| Problem | Most common cause | Prevention |
|---|---|---|
| Tube sheet leak | Insufficient rolling interference | Specify 0.05–0.10 mm interference |
| Crevice corrosion at tube sheet | Elastomeric gaskets or poor rolling | Metal-to-metal rolling only |
| U-bend cracking | Weld seam on outer radius of tight bend | Use seamless or orient seam to neutral axis |
| Inlet end erosion | Sand or solids in fluid | Add ferrules or reduce velocity |
| Tube vibration damage | Flow-induced vibration at baffles | Check unsupported span length per TEMA |
FAQ
1. What is the most common size for GR1 heat exchanger tubes?
25.4 mm OD x 1.65 mm wall (1.0 inch OD x 0.065 inch wall). This size is stocked by most suppliers. 19 mm OD x 1.24 mm wall is also common.
2. Can GR1 tubes be used in feedwater heaters?
Yes, but check temperature. For feedwater heaters above 80°C, specify GR7 instead of GR1. For nuclear feedwater heaters, seamless is often required.
3. What is the maximum unsupported tube length for GR1?
Refer to TEMA standards. For typical 25.4 mm OD x 1.65 mm wall, maximum unsupported span is approximately 1,500 mm for clean service. Reduce for high flow or vibration risk.
4. How to prevent tube inlet erosion in sandy water?
Install titanium ferrules at tube inlets. Ferrules extend 50–100 mm into the tube and protect the leading edge from sand impact. Specify ferrules on the PO.
5. Can GR1 tubes be used with carbon steel tube sheets?
Yes, but isolate to prevent galvanic corrosion. Use a titanium-faced tube sheet, or apply coating on the carbon steel. Direct titanium-to-carbon steel contact in conductive fluid causes rapid corrosion of the carbon steel.
6. What tube pitch is recommended for GR1 tubes?
Standard TEMA pitch: 1.25x OD for triangular pattern, 1.3x OD for square pattern. For 25.4 mm OD tubes, typical pitch is 32 mm.
7. How to clean GR1 tubes during heat exchanger maintenance?
High-pressure water jetting (5,000–10,000 psi) is effective. Sponge ball cleaning works for condensers. Acid cleaning with inhibited hydrochloric or sulfamic acid is acceptable. Do not use hydrofluoric acid.
8. Can GR1 tubes be re-used after pulling from an old tube sheet?
Not recommended. Rolling work-hardens the tube end. Re-rolling the same tube end often leads to cracking. Replace tubes rather than re-use.
9. What is the typical delivery lead time for GR1 heat exchanger tubes?
Welded tubes in standard sizes: 2–4 weeks. Seamless or non-standard sizes: 6–10 weeks. Large quantities (over 10,000 kg) add 2–4 weeks.
10. Which industries use GR1 heat exchanger tubes most?
Power generation (condensers, feedwater heaters), desalination (evaporators, preheaters), chemical processing (coolers, heaters), marine (engine coolers, hydraulic oil coolers), and HVAC (chillers, condensers).
Our Factory & Equipment
Our facility is equipped with dedicated titanium tube production lines, including cold pilger mills, draw benches, and argon-filled annealing furnaces specifically calibrated for commercially pure titanium. For welded tubes, we use automatic TIG welding stations with online eddy current monitoring to detect weld seam defects in real time. Inspection equipment includes a full-spectrum spectrometer for chemical verification, an ultrasonic flaw detector for seamless tubes, and a hydrostatic pressure tester rated to 10,000 psi. All finished tubes pass through a laser micrometer for OD and wall thickness measurement. Our quality lab maintains independent cross-checks on every heat lot, and all inspection equipment is calibrated annually to NIST-traceable standards. This setup allows us to produce ASTM B338 tubes that consistently meet or exceed the required mechanical and corrosion performance.
