Procurement Guide for Figure 8 Blanks (Spectacle Blinds): Specifications, Quality Checks & RFQ Tips

Request the manufacturer's material test certificates (MTC) to confirm chemical and mechanical properties.

RFQ Checklist: What to Send Before Quotation

To get accurate, competitive quotes, include the following in your request for quotation (RFQ):

• Nominal pipe size (NPS) and pressure class (e.g., NPS 6, Class 300)
• Facing type: Raised face (RF), flat face (FF), ring joint (RTJ), etc.
• Material grade: Specify both the blank (blind) and spacer material if different.
• Required certifications: e.g., EN 10204 3.1, NACE MR0175, PMI testing.
• Quantity and packaging requirements (wooden crates, pallets, etc.).
• Delivery schedule and destination (incoterms).

Providing a clear specification sheet avoids back-and-forth and reduces risk of incorrect supply.

Quality Risks and Inspection Documents

Figure 8 blinds must seal when the solid side is installed, so dimensional accuracy and surface finish are critical. Common quality risks include:

• Incorrect thickness: The blind thickness must match the pressure class. Too thin can cause deformation under pressure.
• Gasket face finish: Raised face finish (125–250 μin Ra typical) must be consistent to prevent leaks.
• Misalignment: The two ends (blank and spacer) must align perfectly with the bolt holes of the mating flanges.
• Material substitution: Some manufacturers may use lower-grade material. Always demand MTC and third-party inspection if possible.

Inspection documents to request:

• Material Test Reports (MTR)
• Dimensional inspection report (with actual measurements)
• Visual inspection report (surface defects, cracks, etc.)
• Non-destructive testing reports (ultrasonic, dye penetrant if required)
• Hardness test report (for alloy steels)
• Pressure test certificate (if hydrostatic testing is specified)

A reputable supplier will provide these documents without hesitation.

Manufacturing Process Overview

Understanding the production steps helps you evaluate supplier capability. While the process varies by manufacturer, typical steps include:

1. Material preparation – Plate cutting to rough shape.
2. Forging or machining – For high-pressure classes, forging is preferred over plate cutting for better grain structure.
3. Heat treatment (if required for alloy steels) – Normalizing, quenching, and tempering to achieve mechanical properties.
4. Machining – Final dimensions, facing, and drilling of bolt holes.
5. Surface treatment – Anti-corrosion coating (e.g., oiling, painting) as per customer spec.
6. Inspection and testing – Dimensional, NDT, pressure tests.
7. Marking – Permanent stamping with size, material, pressure class, and heat number.
8. Packaging – Secure packing for export.

When auditing a supplier, check that they have CNC machining centers, heat treatment furnaces, and in-house NDT capabilities. Third-party certification (e.g., ISO 9001) is a good baseline.

Conclusion

Figure 8 blinds are simple yet mission-critical components. Spending time on proper specification and supplier qualification pays off in reduced downtime and safer operations. Always confirm the applicable standard (ASME B16.48), review material certificates, and include a detailed RFQ checklist.

For reliable figure 8 blinds with full traceability and third-party inspection options, contact Hebei Haihao Group. They offer a wide range of sizes and materials, ensuring compliance with ASME and other international standards. Submit your RFQ today for a prompt quotation.