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Views: 0 Author: Site Editor Publish Time: 2026-10-28 Origin: Site
Two stainless steel flanges can share the same size, pressure class and raised-face designation. Their gasket-contact surfaces may still have different machining patterns or roughness.
Flange face finish describes that surface condition. For buyers and inspectors, the task is to specify it clearly and verify it correctly. Visible tool marks, a shiny appearance or one roughness reading cannot answer every acceptance question.
Specify the face geometry, machining pattern and roughness as separate requirements.
Record the roughness parameter and units, not just a number.
Match the finish to the governing specification and intended gasket arrangement.
Use the acceptance method required by the applicable standard and purchase order.
Assess scratches, dents and raised metal separately from the general surface texture.
Flange face finish concerns the texture produced on the gasket-contact surface. It differs from the overall face configuration and from accidental damage.
Feature | What it describes | Example of an ordering or inspection question |
|---|---|---|
Face geometry | Shape and dimensions of the sealing interface | Is the specified raised face correctly formed? |
Machining pattern | Direction and arrangement of the tool marks | Is the finish concentric or spiral? |
Roughness | Texture described by a defined parameter and units | What Ra requirement applies? |
Surface condition | Cleanliness and localized imperfections | Is there a scratch, dent or raised burr? |
For a stainless steel flange order, keep these requirements distinct. “RF” identifies a raised-face configuration; it does not complete the finish specification.
Flatness also needs separate consideration. A roughness result does not establish that the whole sealing face has the required form.
A serrated finish contains deliberately machined grooves. Their pattern should be distinguished from irregular marks caused by damage or unstable machining.
Concentric serrations form separate circles around the flange bore. The pattern is centred on the sealing surface.
Confirm the required machining details from the drawing or governing specification. The presence of circular marks alone does not establish their spacing, profile or acceptable roughness.
A spiral finish follows a continuous groove as the cutting tool feeds across the rotating face. It is also described as a phonographic pattern.
Both concentric and spiral patterns can occur in specified flange finishes. Neither pattern is automatically preferable for every gasket and application.
Avoid treating “serrated” as a complete manufacturing instruction. Where groove details matter, include the applicable standard reference or defined drawing requirements.
A smoother surface has less pronounced texture, but appearance is an unreliable specification. A polished-looking face can still have waviness or localized damage.
Do not request a mirror finish simply because it appears cleaner. The appropriate surface depends on the joint requirements and gasket design.
Use the separate guide to flange gasket selection when choosing the gasket arrangement. Once selected, carry its relevant finish requirements into the flange specification.
A requirement such as “finish 125” leaves important questions unanswered. The number needs a parameter, units and an acceptance basis.
Ra describes the arithmetic mean of absolute profile deviations. It is commonly associated with the term arithmetic average roughness.
Rq uses a root-mean-square calculation. Rz describes a peak-and-valley height characteristic whose definition depends on the referenced measurement standard.
These parameters are not interchangeable labels. Do not convert an Ra limit into Rz or RMS using an assumed universal multiplier.
If an old specification mixes “Ra,” “AARH” and “RMS,” resolve the intended requirement before ordering or inspecting.
Roughness values may be expressed in micrometres, written as μm, or microinches, written as μin.
1 μin = 0.0254 μm. For example, 125 μin equals 3.175 μm.
This converts units only. It does not convert one roughness parameter into another. For acceptance, retain the limits and unit system specified by the governing document.
For applicable serrated facings, ASME B16.5 specifies an average-roughness range of 3.2–6.3 μm, stated as 125–250 μin. Other facing categories have different requirements, and agreed alternative finishes may apply.
Do not transfer that range automatically to ring-joint grooves, every gasket design or another flange standard.
Also distinguish a range from a maximum. A requirement with both lower and upper limits is not equivalent to “Ra below 6.3 μm.”
The method used to accept the face should be clear before machining begins. A supplier and buyer can reach different conclusions if they use different assessment methods.
ASME B16.5 specifies visual comparison with Ra reference standards for judging gasket-contact finish, rather than electronic stylus-tracer assessment. Follow that requirement where it governs the order.
Identify the comparison specimens used and ensure they are suitable for the finish being assessed. Keep their identification with the inspection record.
An electronic trace may support additional process control or agreed reporting. Do not treat it as an automatic replacement for the standard’s acceptance method.
Where a drawing or agreed inspection plan requires instrumental measurements, record the selected parameter and measurement standard.
Also identify the instrument, probe, filtering settings, evaluation length and trace direction. These conditions influence how a measured profile is assessed.
The trace normally needs to cross the machining lay rather than follow along it. Use the approved procedure for the actual surface and available measuring area.
Do not compare readings taken under different settings as though they were identical tests. Resolve the method difference first.
Associate the result with the flange identification, drawing revision and inspected face. Record the inspection location and whether the evidence is comparative or instrumental.
A photograph helps document appearance and location. It does not replace the specified roughness assessment.
SDFL’s flange quality inspection includes machining-stage surface-finish checks and final appearance checks. Agree on any additional records required for your order before production.
General texture and isolated imperfections are different inspection questions. A satisfactory comparison or reading does not automatically accept every part of the face.
Check the gasket-contact area for scratches, dents, corrosion pits and raised metal. Describe where each finding lies relative to the bore and sealing band.
Record its direction, dimensions and affected area using the agreed inspection procedure. A mark crossing the sealing band deserves assessment against the applicable criteria.
Do not declare every visible mark unacceptable. Equally, do not dismiss a mark because the surrounding surface meets the roughness requirement.
A fingernail check cannot establish a quantified defect limit. Nor can a close-up photograph reliably reveal depth or remaining flange thickness.
Use the relevant standard’s imperfection criteria and any project-specific requirements. If the finding cannot be assessed with the available evidence, obtain the missing measurements before release.
Keep dimensional form checks separate as well. Surface texture, flatness and a local dent describe different aspects of the component.
Do not remove a scratch through uncontrolled polishing or grinding. That can change the specified texture and local geometry.
Before refacing, establish whether machining can preserve the required thickness, facing dimensions and other applicable features. Define the finished condition and reinspection requirements.
After approved rework, update the inspection record. Acceptance should describe the final surface, rather than rely on results taken before material was removed.
A clear request gives manufacturing and inspection teams the same reference. Avoid relying only on phrases such as “stock finish,” “smooth face” or “standard serrations.”
RFQ or inspection field | What to include |
|---|---|
Component identity | Flange type, material, size, rating and drawing revision |
Governing requirement | Applicable standard, edition and relevant drawing notes |
Contact surface | Facing designation and the area requiring the specified finish |
Texture requirement | Machining pattern and any required groove details |
Roughness requirement | Parameter, units and the applicable limits |
Acceptance method | Required comparison method and any agreed additional measurements |
Surface condition | Applicable imperfection criteria and treatment of nonconforming findings |
Records | Component identification, results, photographs where useful and rework history |
Resolve conflicts before manufacture. If the flange drawing and gasket recommendation require different finishes, clarify the accepted requirement with the responsible parties.
For a custom component, replace an undefined phrase with an agreed technical instruction. Do not let a workshop interpretation become the only record of the intended surface.
Include the final treatment condition where relevant. If cleaning, pickling or another process follows machining, identify when the required finish is to be accepted.
A useful flange face finish specification connects the machining pattern, roughness requirement and acceptance method. Local damage and dimensional form need their own checks.
SDFL manufactures stainless steel flanges with dimensional and surface-finish inspection during production. Providing the drawing, gasket arrangement and inspection requirements helps establish the intended finished condition before machining starts.
Need a defined finish for your stainless steel flange order?
A photograph can show the general machining pattern and visible surface damage. Lighting, scale and camera angle limit its value. Confirm acceptance through the specified assessment method and keep photographs as supporting evidence.
A material certificate addresses the material information within its scope. It does not automatically confirm the final machining texture. Request a component-linked finish inspection record when the order requires that evidence.
Define the acceptance condition before processing. If a later treatment can affect the specified surface, review the final condition against the agreed requirements. Do not assume that a pre-treatment inspection covers every subsequent operation.
Yes. Ra is a numerical profile characteristic, not a complete description of the surface pattern. Two faces can share a similar value while differing in lay, groove arrangement or other features. Keep those requirements separate.
Use the original drawing and service specification where available. An old spare may be worn, damaged or previously refinished. Its current appearance does not necessarily represent the intended manufacturing condition or the correct requirement for a new order.
