Mermade 30" Round (4-17/32" Hub) Zipper Closure, Cover Only

The Mer-Made 30" Round (4-17/32" Hub) Zipper Closure — Cover Only (cataloged under Part # 775-COVER / VFC-30R-ZIP-417) is the tailored replacement synthetic fabric filter jacket envelope designed to re-cover existing bare circular leaf cores in round-tank commercial vacuum DE filter vaults and cylindrical surge-tank systems (including legacy Swimquip, B/K, and circular Mer-Made filter arrays).

This model is fabricated as a circular disc envelope measuring 30" outside diameter (O.D.) with a pre-cut, reinforced 4-17/32" central hub penetration collar (approx. 115.1 mm) and a heavy-duty, marine-grade perimeter Delrin/nylon zipper closure. It supplies only the tailored filtration cloth, center hub cutouts, perimeter zipper assembly, and paired replacement hub sealing gaskets. It is specified when the internal polypropylene radial drainage grid core and circular outer rim remain structurally sound, but the existing cloth has blinded from mineral scaling, calcified DE, or body oils, or has suffered abrasion tears.

Technical Specifications & Scope of Delivery

Material Properties & Chemical Tolerances

• Chlorine & Saline Resistance: Virgin woven polypropylene fibers resist degradation, rot, and hydrolysis under continuous exposure to elevated free chlorine levels, shock hyperchlorination treatments, and saline electrolytic pool water (2,500 to 5,000+ ppm NaCl).

• Acid Wash Survivability: Withstands routine seasonal chemical descaling baths in dilute muriatic (hydrochloric) or citric acid solutions to dissolve calcified DE crust, calcium carbonate, and iron scale without deteriorating seam threads or zipper tape.

• Pre-Coat Retention & Cake Release: The balanced monofilament weave structure retains standard DE powder and perlite grades without bleed-through during initial pump startup, while facilitating clean cake release during backwashing or manual hose-down.

Physical Dimensions & Weight Estimates

• Individual Cover Net Weight: Approximately 0.80 to 1.10 lbs (0.36 to 0.50 kg).

• Single Boxed Cover Shipping Weight: Approximately 1.70 to 2.50 lbs (0.77 to 1.13 kg) in a compact corrugated carton.

• Master Carton / Multi-Pack (6 to 12 Covers): Approximately 7.0 to 13.5 lbs (3.2 to 6.1 kg).

• Full Bank Overhaul Pack (20 to 30 Covers): Approximately 19.0 to 30.0 lbs (8.6 to 13.6 kg).

Field Re-Covering & Tensioning Steps

1. Strip Old Jacket & Inspect Frame: Remove the spent circular leaf from the center manifold shaft. Unzip the spent jacket around the outer rim and peel the fabric away from the core. Discard old hub gaskets. Pressure-wash the bare radial drainage grid to dislodge calcified DE, and inspect the outer rim and hub edges for burrs, cracks, or sharp edges that could snag the new cover.

2. Position the Replacement Jacket: Unzip the replacement cover fully and slide the bare circular core inside the envelope, guiding the reinforced inner circular cutouts squarely over the 4-17/32" central hub collar on both faces.

3. Align Center Hub Collars: Ensure the reinforced inner borders sit flat against the hub seating faces without puckering, twisting, or encroaching into the gasket sealing grooves.

4. Zip & Tension: Bring the two outer halves of the cover together along the perimeter rim. Smoothly pull the Delrin zipper slider around the circumference, gently stretching the fabric outward toward the edges as you close the seam to ensure uniform radial tension across both disc faces.

5. Secure Zipper Pull: Tuck the zipper pull tab into its integrated protective elastic/fabric pocket flap to prevent snagging on adjacent leaves during operation or stacking.

6. Install Hub Gaskets & Restack: Place fresh hub sealing gaskets or O-rings onto the center hub faces before sliding the re-covered element back onto the collector manifold shaft. Verify proper spacing between adjacent leaves before torquing down the shaft end-compression plate.