ASTM A234 WP5 Pipe Fittings – Technical Specifications
1. Material Overview
ASTM A234 WP5 specifies 5Cr-0.5Mo alloy steel pipe fittings for high-temperature service in:
– Power generation (up to 650°C/1200°F)
– Petrochemical processing
– Refinery applications
– High-pressure steam systems
2. Key Characteristics
– **Superior creep resistance** vs. lower Cr-Mo grades
– **Enhanced sulfidation resistance**
– **Excellent oxidation resistance**
– **Good hydrogen attack resistance**
3. Chemical Composition (%)
| Element | Composition Range |
|———|——————-|
| Carbon (C) | 0.15 max |
| Manganese (Mn) | 0.30-0.60 |
| Phosphorus (P) | 0.03 max |
| Sulfur (S) | 0.03 max |
| Silicon (Si) | 0.50 max |
| Chromium (Cr) | 4.00-6.00 |
| Molybdenum (Mo) | 0.44-0.65 |
4. Mechanical Properties
| Property | Requirements |
|———-|————–|
| Tensile Strength | 415-585 MPa (60,000-85,000 psi) |
| Yield Strength | 205 MPa min (30,000 psi min) |
| Elongation | 20% min |
| Hardness | ≤197 HB |
5. Temperature Capabilities
– **Maximum Temperature**: 650°C (1200°F)
– **Minimum Temperature**: -29°C (-20°F) with impact testing
– **Optimum Service Range**: 400-600°C (750-1110°F)
6. Manufacturing Standards
– **Base Standard**: ASTM A234
– **Dimensional Standards**:
– ASME B16.9 (Butt-welding fittings)
– ASME B16.28 (Short radius elbows)
– **Heat Treatment**: Full anneal or normalize + temper
7. Available Fitting Types
1. **Elbows** (45°/90°/180°; SR/LR)
2. **Tees** (equal/reducing)
3. **Reducers** (concentric/eccentric)
4. **Caps**
5. **Stub Ends**
6. **Crosses**
8. Heat Treatment Requirements
– **Normalizing**: 900-950°C (1650-1750°F)
– **Tempering**: 650-750°C (1200-1380°F)
– **PWHT**: Mandatory (705-760°C / 1300-1400°F)
9. Welding Considerations
– **Preheat**: 200-300°C (400-600°F)
– **Interpass Temp**: ≤300°C (≤600°F)
– **Filler Metals**:
– SMAW: E502-XX or E505-XX
– GTAW/GMAW: ER502/ER505
– **PWHT**: Required for all welds
10. Quality Control
– **Mandatory Tests**:
– Hydrostatic (1.5x design pressure)
– Tensile testing
– Hardness testing
– **Optional Tests**:
– Charpy V-notch impact
– PMI verification
– Radiographic testing
11. Corrosion Resistance
– **Oxidation**: Excellent up to 650°C
– **Sulfidation**: Superior to lower alloy steels
– **Hydrogen Attack**: Good resistance at moderate temps
12. Applications
– Power Plants:
– High-pressure steam lines
– Superheater piping
– Boiler components
– **Refineries**:
– Hydroprocessing units
– Catalytic reformers
– Coker units
– **Petrochemical**:
– Ethylene cracking
– High-temp reactors
13. Comparison with Similar Grades
| Grade | Cr% | Mo% | Key Difference |
|——-|—–|—–|—————-|
| WP11 | 1.25 | 0.5 | Lower Cr content |
| WP22 | 2.25 | 1.0 | Different Cr-Mo ratio |
| WP9 | 9.0 | 1.0 | Higher alloy content |
14. Purchasing Specifications
When ordering, specify:
– ASTM A234 WP5
– Fitting type and size
– Schedule/wall thickness
– Heat treatment condition
– End preparation
– Testing requirements
– Certification (MTR to EN 10204 3.1/3.2)
15. Maintenance Requirements
– **Inspection Frequency**:
– Quarterly for critical service
– Annually for standard service
– **Key Checks**:
– Ultrasonic thickness
– Dye penetrant inspection
– Creep damage assessment
– Replacement Criteria:
– 15% wall thinning
– Visible creep voids
– Cracks in weld HAZ
WP5 fittings require strict temperature control during welding and heat treatment. Always follow ASME B31.3 for installation guidelines in process piping systems.
