MSS SP-97 ASTM B564 UNS N06625 Weldolet | Alloy 625 Branch Outlet Fitting
MSS SP-97 ASTM B564 UNS N06625 Weldolets are integrally reinforced forged branch outlet fittings used in offshore, seawater, chemical-processing and other demanding piping systems. Alloy 625 combines high nickel and chromium contents with molybdenum and niobium to provide high mechanical strength together with excellent resistance to pitting, crevice corrosion and chloride-induced attack.
We manufacture and supply UNS N06625 Weldolets, Sockolets, Threadolets and other forged branch outlet fittings in custom run and branch sizes, with EN 10204 3.1 certification and project-specific inspection when required.
MSS SP-97 N06625 Weldolet Quick Specification
| Item | Specification |
|---|---|
| Material | UNS N06625 |
| Common Designation | Alloy 625 |
| EN / W.Nr. | 2.4856 |
| Material Family | Nickel-Chromium-Molybdenum-Niobium Alloy |
| Material Standard | ASTM B564 / ASME SB-564 |
| Outlet Standard | MSS SP-97 |
| Main Product | Weldolet |
| Other Types | Sockolet / Threadolet / Other branch outlet fittings |
| Connection | Butt Weld / Socket Weld / Threaded |
| Branch Bore | Matched to specified branch pipe schedule |
| Certification | EN 10204 3.1 / 3.2 when specified |
What Is an MSS SP-97 Weldolet?
A Weldolet is an integrally reinforced forged branch outlet fitting with a butt-weld branch end.
It is welded directly onto the run pipe to create a branch connection while providing reinforcement around the branch opening.
The design provides:
- Smooth stress transfer
- Integral branch reinforcement
- Compact piping layout
- Reduced local stress concentration
- Strong connection between run and branch piping
- Suitability for pressure piping systems
MSS SP-97 covers integrally reinforced forged branch outlet fittings with butt-weld, socket-weld and threaded branch ends.
Weldolet vs Sockolet vs Threadolet
The main outlet types differ by the branch connection method.
| Type | Branch Connection | Typical Use |
|---|---|---|
| Weldolet | Butt Weld | Process and pressure piping |
| Sockolet | Socket Weld | Small-bore welded branches |
| Threadolet | Threaded | Small-bore threaded branches |
Weldolet
A Weldolet uses a butt-weld connection between the outlet and branch pipe.
It is commonly used where welded piping continuity and high mechanical integrity are required.
Sockolet
A Sockolet uses a socket-weld connection and is generally used for smaller branch sizes.
Threadolet
A Threadolet uses an internal threaded connection and is selected where a threaded branch connection is required.
Other branch outlet configurations can also be supplied according to piping layout and project requirements.
What Is ASTM B564 UNS N06625?
ASTM B564 UNS N06625 is a nickel-chromium-molybdenum-niobium forging alloy used for corrosion-resistant forged pressure components.
The alloy is characterized by:
- High nickel content
- High molybdenum content
- Niobium strengthening
- High mechanical strength
- Strong chloride resistance
- Excellent pitting and crevice-corrosion resistance
UNS N06625 is particularly suited to offshore, marine and severe process environments where both corrosion resistance and mechanical strength are important.
ASTM B564 N06625 Grade 1 vs Grade 2
ASTM B564 N06625 can be supplied in different heat-treated conditions.
| Item | Grade 1 | Grade 2 |
|---|---|---|
| Heat Treatment | Annealed | Solution Annealed |
| Typical Positioning | General corrosion-resistant service | Elevated-temperature service |
| Creep / Rupture Consideration | Normal service | More important |
| Approx. Temperature Reference | Up to about 593°C | Above about 593°C when required |
The ordered material grade should be clearly stated in the purchase specification.
Material temperature capability should not be confused with the allowable design temperature of the complete piping system.
UNS N06625 Chemical Composition
| Element | UNS N06625 |
|---|---|
| Nickel, Ni | 58.0% min |
| Chromium, Cr | 20.0–23.0% |
| Molybdenum, Mo | 8.0–10.0% |
| Niobium + Tantalum, Nb + Ta | 3.15–4.15% |
| Iron, Fe | 5.0% max |
| Carbon, C | 0.10% max |
| Manganese, Mn | 0.50% max |
| Silicon, Si | 0.50% max |
| Phosphorus, P | 0.015% max |
| Sulfur, S | 0.015% max |
| Cobalt, Co | 1.00% max |
| Aluminum, Al | 0.40% max |
| Titanium, Ti | 0.40% max |
The Ni-Cr-Mo-Nb system is responsible for the high strength and localized corrosion resistance of N06625.
Actual heat chemistry is reported on the Material Test Certificate.
Mechanical Properties
Mechanical properties depend on the ASTM B564 grade, heat-treatment condition, forging size and final processing condition.
Important acceptance properties can include:
- Tensile strength
- Yield strength
- Elongation
- Reduction of area
- Hardness where specified
The ordered ASTM B564 grade and project requirements should determine the applicable minimum values.
Actual mechanical test results are reported on the supplied MTC.
Corrosion Resistance of Alloy 625 Weldolets
UNS N06625 is widely used where conventional stainless steels may not provide sufficient resistance to aggressive chloride environments.
Pitting Resistance
The high molybdenum content provides strong resistance to localized pitting corrosion.
Crevice Corrosion Resistance
UNS N06625 performs well in many crevice-corrosion environments, especially in chloride-containing process systems.
Chloride Resistance
The combination of nickel, chromium and molybdenum provides strong resistance to chloride-induced attack.
Seawater Resistance
Alloy 625 branch fittings are commonly used in seawater and offshore systems because of their strong localized corrosion resistance.
Actual suitability still depends on:
- Temperature
- Chlorination
- Crevice geometry
- Flow conditions
- Contaminants
- Process chemistry
Why Use a Weldolet?
The main advantage of a Weldolet is that reinforcement is integrated into the fitting geometry.
This can provide:
- Reinforcement around the branch opening
- Smooth load transfer
- Compact design
- Reduced fabrication complexity
- Strong branch connection
- Good suitability for high-pressure and severe-service piping
The final branch connection design should follow the applicable piping code, run-pipe dimensions, branch dimensions and project requirements.
Available Sizes and Schedules
Commercial supply can include a wide range of run and branch combinations.
Typical options include:
| Item | Typical Supply |
|---|---|
| Branch Size | 1/2″ and above |
| Run Size | Project-specific |
| Branch Schedule | Sch 10S / 40S / 80S / 160 / XXS where applicable |
| Connection | BW / SW / Threaded |
| Type | Weldolet / Sockolet / Threadolet |
Selected large-size branch outlet fittings can be manufactured to project-specific requirements.
The commercial manufacturing range should not be treated as the dimensional limit of MSS SP-97.
Schedule vs Pressure Class
Weldolets and socket/threaded outlet fittings are not ordered in exactly the same way.
Weldolet
Weldolets are commonly specified by:
Run Size × Branch Size + Branch Pipe Schedule
Example:
MSS SP-97 ASTM B564 UNS N06625 Weldolet, 12″ × 4″, Sch 40S
Sockolet / Threadolet
Sockolets and Threadolets may be specified using the applicable pressure class or branch connection designation.
The required class, bore and connection details should follow the purchase specification.
Alloy 625 vs Alloy 825 Branch Fittings
| Item | N06625 / Alloy 625 | N08825 / Alloy 825 |
|---|---|---|
| Base System | Ni-Cr-Mo-Nb | Ni-Fe-Cr-Mo-Cu |
| Ni | 58% min | 38–46% |
| Mo | 8–10% | 2.5–3.5% |
| Nb + Ta | 3.15–4.15% | No major addition |
| Cu | Low | 1.5–3.0% |
| Strength | Higher | Moderate |
| Main Positioning | Severe chloride / offshore | Acid / chloride-SCC service |
Neither material is universally superior.
Selection should be based on corrosion environment, strength requirement, temperature and project specification.
Applications
ASTM B564 N06625 Weldolets and branch outlet fittings are commonly used in:
- Offshore piping
- Seawater systems
- Subsea equipment
- Marine piping
- Chemical-processing plants
- High-pressure process systems
- Heat exchangers
- Pump piping
- Valve connections
- Scrubber systems
- Corrosion-resistant branch connections
UNS N06625 is especially suitable where branch fittings must combine high strength with high localized corrosion resistance.
Inspection & Certification
MSS SP-97 ASTM B564 N06625 outlet fittings can be supplied with:
- EN 10204 Type 3.1 MTC
- EN 10204 Type 3.2 when specified
- Heat chemical analysis
- Mechanical test results
- Heat-treatment records
- PMI
- Dimensional inspection
- Visual examination
- Bevel inspection
- Bore inspection
- Surface examination
- PT when specified
- UT when required
- Third-party inspection
- Full heat-number traceability
Inspection requirements can be tailored according to the material standard, branch-fitting standard and project ITP.
Related UNS N06625 Products
UNS N06625 piping systems often require multiple components manufactured from the same corrosion-resistant nickel alloy.
Related products include:
| Product | Typical Specification |
|---|---|
| Forged Flange | ASTM B564 UNS N06625 |
| Weldolet / Branch Outlet | ASTM B564 UNS N06625 / MSS SP-97 |
| Butt-Weld Fittings | ASTM B366 UNS N06625 |
| Pipe / Tube | ASTM B444 UNS N06625 |
| Plate / Sheet | ASTM B443 UNS N06625 |
| Round Bar | ASTM B446 UNS N06625 |
| Stud Bolt / Hex Bolt | UNS N06625 fasteners from applicable B446 bar material |
These products can be supplied together for offshore, seawater, chemical-processing and corrosion-resistant piping projects.
MSS SP-97 ASTM B564 N06625 Weldolet Manufacturer
We manufacture and supply MSS SP-97 ASTM B564 UNS N06625 Weldolets, Sockolets, Threadolets and custom forged branch outlet fittings for offshore, seawater, chemical-processing and severe corrosion applications.
Available options include:
Butt Weld / Socket Weld / Threaded Connections, Custom Run and Branch Sizes, Schedule-Matched Bores, PMI, PT, UT, Dimensional Inspection and EN 10204 Certification
For quotation, please specify:
Material + Outlet Type + Run Size + Branch Size + Branch Schedule + Connection + Quantity + Standard + Inspection Requirements
Example:
MSS SP-97 ASTM B564 UNS N06625 Weldolet, 12″ × 4″, Sch 40S Branch, Grade 1, EN 10204 3.1
