SOSHH® SF-VacuScale™ PTFE | High-Performance Chemical-Resistant Weighing Bellows for Loss-in-Weight Feeders

The Engineering Challenge: Vacuum vs. Micro-Weighing Precision

In industrial powder dosing and loss-in-weight (LIW) feeding systems, traditional silicone or low-grade TPU connectors introduce significant mechanical stress—known as the "spring effect." When operating under high negative pressure (up to -40Kpa), thin connectors collapse and block material flow, while thick rigid sleeves transfer vibrations directly to the load cells, causing severe sensor drift and batch inaccuracies.

The SOSHH® SF-VacuScale™ PTFE Series solves this paradox by combining ultra-flexible 100% PTFE corrugated bellows with an integrated stainless steel skeleton, providing zero force transmission to sensitive scales while effortlessly resisting high vacuum.

System Integration & Vibration Isolation

Technical Mechanics:

As illustrated above, the SF-VacuScale™ bellows acts as a completely neutral mechanical bridge between upstream equipment and downstream weighing hoppers. By absorbing vertical and lateral oscillations, it isolates sensitive load cells from plant vibrations, guaranteeing stable tare weight readings and precise micro-batching (< 5kg).

Key Technical Advantages & Quality Standards

• 100% Multi-Pass Sintered PTFE Fabric: Manufactured via 3–6 cycles of thin-dip sintering at 360°C–380°C. Unlike cheap single-pass coated fabrics, our PTFE deeply permeates the E-glass fiber matrix to form an unbreakable "anchored structure" that withstands hundreds of thousands of flex cycles without delamination or cracking.
• Zero Spring Effect: Provides exceptional axial softness. Eliminates vertical forces and side-loading interference on loss-in-weight feeders.
• Extreme Non-Stick Surface: Friction coefficient is extremely low. Prevents sticky powders like TiO2, carbon black, and resins from building up on the inner wall, eliminating cross-contamination and tare weight drift.
• ATEX Anti-Static / Conductive Option: Available with conductive/dissipative PTFE fabric to safely ground static charges in explosive powder environments (e.g., lithium battery materials, toners).
• Tool-Free Snap-Fit Installation: Features a 100% flush inner bore with no hose clamps, internal steps, or crevices where powder can lodge.

Crucial Installation Standards

To ensure optimal weighing accuracy and long service life, spigots must be installed according to strict engineering tolerances:

1. Exact 80mm Installation Gap (IG): Spigots must be welded with an exact 80mm (3 5/32") gap. This prevents the bellows from being pre-stretched or compressed, maintaining neutral elastic behavior.
2. Strict Vertical Alignment: Spigots must be vertically concentric. Any angular misalignment creates unwanted lateral forces on the load cell.
3. Welding Spacer Requirement: Always use an 80mm rigid spacer during site welding to maintain precise gap geometry and account for thermal shrinkage.

Standard Size & Dimension Chart

• Wall Thickness (T): 1.0 mm default for compact sizes; 2.0 mm default for standard structural spigots.
• Inner Diameter (d): Regulated precisely as D - 4 mm for a perfectly flush inner surface.
• Height Options (h): 50 mm (Compact) / 90 mm (Extended, for tail cutting/welding adjustments).

(Note: Custom non-standard outer diameters, matching flanges, and free STEP/DXF 3D CAD model verification are available upon request.)

Procurement Bidding & Quality Verification Criteria

When issuing tenders or selecting suppliers for high-value processing lines, specify these non-negotiable parameters to avoid low-quality counterfeits:

• Base Fabric Standard: E-glass weave with thorough desiliconization and silane coupling agent primer.
• PTFE Content Index: Total weight PTFE content ≥ 58%; Areal density: 380 ~ 480 g/m².
• Manufacturing Process: Multi-pass dip-sintering only (3–6 passes). Strictly reject single-pass spraying, glue-laminated film (delaminates rapidly), or low-alkali glass fabric.
• Thermal & Chemical Limits: Continuous operating temperature -60°C to 220°C. Resistant to concentrated acids, alkalis, and organic solvent vapors.

Industry Applications

• Lithium Battery Manufacturing: Anode/cathode powders (LFP, NCM, lithium salts) operating at elevated temperatures (120°C ~ 180°C).
• Fine Chemicals & Pigments: Titanium Dioxide (TiO2), carbon black, resin powders, and solvent vapors.
• Pharmaceutical & Food Additives: Active Pharmaceutical Ingredients (APIs) requiring FDA/EC 1935 compliant, clean-in-place PTFE solutions.

Frequently Asked Questions

Q: How does the SOSHH® SF-VacuScale PTFE eliminate the "spring effect" in loss-in-weight feeders?

A: By utilizing an optimized corrugated bellows shape made from ultra-thin 0.5mm/1.0mm PTFE fabric, the connector exhibits near-zero axial stiffness. This isolates vibration without transferring vertical tension or shear forces to the load cells beneath the feeder.

Q: Why is multi-pass sintered PTFE required instead of single-pass coated fabric?

A: Single-pass coatings only deposit a thin layer of PTFE on the surface, which cracks and delaminates after a few hundred flex cycles. SOSHH’s multi-pass impregnation (3–6 passes) forces PTFE deep into the yarn gaps, creating an anchored, wear-resistant structure designed for long-term continuous deformation.

Q: Can this connector be used in ATEX explosive dust environments?

A: Yes. SOSHH provides conductive/anti-static PTFE versions engineered specifically to dissipate static charges in hazardous dust environments like carbon black, toner, or lithium battery powder handling lines.

Q: What is the exact installation gap requirement for SOSHH weighing bellows?

A: The installation gap between the upper and lower spigots must be set precisely to 80 mm (3 5/32") using a rigid spacer before welding to maintain consistent weighing accuracy and prevent premature material fatigue.