Paddle Blank Flange vs. Spectacle Blind Flange: Technical Insights and Industry Applications
In critical piping systems, operators must frequently isolate sections of pipelines for maintenance, inspection, or repair. Two of the most reliable solutions are the paddle blank flange (spade flange) and the spectacle blind flange. While they serve similar functions, each design has its own advantages depending on the system design, space availability, and frequency of operation.
Haihao Group recently supplied a 24-inch Class 600 RF Paddle Blank Flange in ASTM A240 316 stainless steel for a Singapore project, reflecting the growing demand for high-performance pipeline isolation components in the petrochemical and offshore industries.
24-inch Class 600 paddle blank flange in ASTM A240 316 stainless steel
What is a Paddle Blank (Spade Flange)?
A paddle blank flange, also called a spade flange, is a single solid metal plate used to block flow in a pipeline.
- Design: Shaped like a paddle with a handle, inserted between two flanges.
- Function: Provides complete flow isolation.
- Operation: To reconnect the pipeline, the paddle blank is removed and replaced with a paddle spacer (if required).
This simple yet effective solution is especially useful where pipeline isolation is needed less frequently.
What is a Spectacle Blind Flange?
A spectacle blind flange is essentially two paddle blanks joined by a bridge-one solid plate and one open spacer.
- Design: Looks like a pair of glasses (“spectacles”), hence the name.
- Function: One end blocks the flow, the other allows flow when rotated into position.
- Operation: The component stays permanently installed in the system, rotated when flow conditions change.
Spectacle blinds are typically used where regular isolation and reconnection are required, saving time and effort compared to removing and reinstalling paddle blanks.
Haihao Flange Factory Finished Spectacle Blind Flanges
Key Differences: Paddle Blank vs. Spectacle Blind Flange
| Feature | Paddle Blank (Spade Flange) | Spectacle Blind Flange |
|---|---|---|
| Design | Single solid plate with handle | Dual plates (solid + spacer) joined together |
| Installation | Inserted or removed between flanges | Permanently installed, rotated as needed |
| Best Use Case | Infrequent isolation | Frequent isolation |
| Cost | Lower initial cost | Higher initial cost, but more convenient long-term |
| Space Requirement | Less space needed | Requires more space for installation and rotation |
Material Selection for Harsh Environments
Depending on the application, both paddle blanks and spectacle blinds are manufactured from a variety of materials:
- Stainless Steel (ASTM A240 316/316L): Excellent corrosion resistance for petrochemical and marine use.
- Super Duplex Stainless Steel (UNS S32750): High strength and superior resistance to chloride-induced corrosion, ideal for offshore and subsea systems.
- Inconel Alloys (N06625): Exceptional performance in high-temperature and aggressive chemical environments.
- Carbon Steel (ASTM A516 Gr.70, ASTM A350 LF2): Cost-effective choice for general industrial pipelines, with optional epoxy coatings for extra protection.
Industry Applications
Both paddle blanks and spectacle blinds are vital in:
- Petrochemical Plants: For isolating high-pressure process lines during shutdowns.
- Offshore Oil & Gas: Resistant to seawater, ensuring safe isolation in topside and subsea installations.
- Power Generation: Used in steam pipelines and cooling water systems.
- Water Treatment & Marine Systems: Prevent backflow and allow safe inspection in desalination and seawater handling facilities.
Choosing Between Paddle Blank and Spectacle Blind Flanges
The decision depends on frequency of use, available space, and budget:
- Choose paddle blanks for systems where isolation is occasional and cost efficiency is important.
- Choose spectacle blinds for systems requiring frequent changeovers, where operational convenience outweighs initial cost.
Haihao Group provides both solutions, manufactured to ASME B16.48, ISO 27509, and other international standards, with full NACE compliance, PMI testing, and mechanical certification.