Technical knowledge
MSS SP-25 marking: the cheapest traceability you will ever buy
What MSS SP-25 requires to be marked on flanges and fittings, why the heat number matters for lifecycle traceability, and how to specify marking so it survives painting, insulation and service.
What must appear on the component
- Manufacturer name or registered trademark.
- Material designation. The ASTM or ASME specification and grade, for example ASTM B564 N06625.
- Pressure class or rating. For example 300, or the rating designation required by the applicable standard.
- Size. Nominal pipe size and, where applicable, the bore or series designation.
- Heat number or heat code. The link back to the certificate.
- Conformance markings such as the applicable standard designation, where required by the product standard.
Marking methods and when each is appropriate
| Method | Best for | Cautions |
|---|---|---|
| Hard steel stamp | Carbon steel and thicker sections | Stress raiser; avoid on thin or highly stressed areas |
| Low stress dot stamp | Alloy components where cracking risk matters | Preferred for stainless and nickel alloys |
| Electrochemical etch | Smooth machined surfaces | Must be chloride free and neutralised |
| Vibratory etch | Finished surfaces, small components | Legibility depends on surface finish |
| Stencil or tag | Supplementary identification | Not a substitute for permanent marking |
Making sure the marking survives
Mark on the outside diameter or the rim where it will not be removed by machining, and avoid the sealing face and the weld end bevel. Where the component will be painted, insulated or buried, add a supplementary tag and record the heat number in the as built documentation. Low stress stamps and chloride free etching fluids are preferred for stainless and nickel alloys to avoid initiating corrosion or cracking at the mark.
Questions about this topic
Is the heat number required by MSS SP-25?
The standard requires identification that permits traceability to the material, which in practice means a heat number or a heat code that links to the certificate. State on the order that the heat number must appear on every component.
Can I stamp stainless and nickel alloy flanges?
Use low stress dot stamping or electrochemical etching rather than sharp impact stamps. Sharp stamps create local stress and can initiate cracking or corrosion in the mark.
What if the marking is removed during machining?
Plan the marking location so it is outside the machined envelope, and transfer the heat number to a supplementary tag or documentation before further processing. Traceability must never be broken by a machining operation.
Questions about our products
What products does Hangbo Alloy supply?
Four product families, all available in nickel-based alloys, titanium, duplex and special stainless steel: flanges, butt weld pipe fittings, elbows, and seamless tube and pipe. Flanges cover weld neck, long weld neck, slip-on, blind, socket weld, threaded and lap joint patterns. Fittings and elbows cover concentric and eccentric reducers, equal and reducing tees, caps, stub ends, and 45°, 90° and 180° returns in both long and short radius, plus 3D and 5D bends for piggable lines. Seamless tube and pipe is supplied cold drawn or hot finished from 6 mm to 630 mm outside diameter.
Which alloy grades are available for these products?
More than 90 grades are published in our grade library. The most requested are Inconel 625, 718, 600 and X-750, Hastelloy C-276, C-22 and B-2, Monel 400 and K-500, Incoloy 800H, 825 and 925, duplex 2205 and super duplex 2507, 316L, 904L and 254SMO stainless steel, and titanium Grade 2 and Grade 5. Nickel-based grades can also be supplied with VIM plus ESR double melting where cleanliness or fatigue life is critical.
What sizes, wall thicknesses and pressure classes can you supply?
Flanges run from NPS ½ to NPS 24 to ASME B16.5 and from NPS 26 to NPS 60 to ASME B16.47 Series A or B, in pressure classes 150 through 2500. Butt weld fittings and elbows run from NPS ½ to NPS 48 (DN 15 to DN 1200) in wall thickness Schedule 5S through XXS. Seamless tube and pipe covers 6 mm to 630 mm outside diameter, in random lengths of about 5 to 7 metres or fixed lengths up to 12 metres. Non-standard and intermediate sizes are quoted on request.
Which material and dimensional standards do you work to?
Forged flanges to ASTM B564, B381 and A182 with dimensions to ASME B16.5 and ASME B16.47. Butt weld fittings and elbows to ASTM B366 and A403 with dimensions to ASME B16.9 and MSS SP-43. Seamless tube and pipe to ASTM B444, B423, B622, B163, B167, B861, A312, A213 and A790. Marking follows MSS SP-25 and the applicable product standard. If your project is governed by EN, DIN, JIS or a company specification, send the document and we will confirm equivalence before quoting.
Is there a minimum order quantity?
There is no minimum for standard sizes and grades held in stock, and prototypes, spares and small trial batches are accepted. Made-to-order melts and special forgings carry a minimum weight that depends on the alloy and the route, typically from about 500 kg for special grades.
What inspection and certification is issued with the goods?
Every shipment carries an EN 10204 3.1 mill test certificate quoting the actual chemical and mechanical results for the specific heat lot, together with dimensional records and heat treatment data where applicable. Testing is carried out in house by optical emission spectrometry, tensile, impact and hardness testing, plus ultrasonic and eddy current examination, with hydrostatic pressure and intergranular corrosion testing to ASTM G28 or A262 Practice E where the specification requires it. Third party inspection by SGS or another recognised agency can be arranged, and their report is issued alongside the shipment.
What are typical lead times?
Standard stock items ship within days. Common production grades such as Inconel 625 or duplex 2205 are typically a few weeks. Special chemistries, larger forgings and items that require third party inspection take longer and are quoted individually against the requirement.
How are the products packed for export?
Flanges and fittings receive a rust preventive coating, are individually wrapped and are packed in plywood cases secured with steel banding. Tube ends are capped and bundles are strapped. Packing lists quote heat numbers so every case can be cross-checked against the mill certificate on arrival. We quote EXW, FOB, CFR, CIF and DAP, and mixed-alloy orders can be consolidated into one shipment with a single documentation package.
How do I request a quotation or a sample?
Send the grade or UNS number, the dimensions including schedule or wall thickness, the governing material and dimensional standards, quantity, any heat treatment or NDT scope and the certificate type you need; a drawing is ideal for special flanges and fittings. Email [email protected] or message us on WhatsApp +86 15618279078 and we normally issue a formal quotation within 24 hours on working days. Samples and previous test reports can be arranged before the first order.
Talk to an engineer
Share your duty conditions and we will shortlist candidate alloys within one working day.