1. Marine-Grade Stainless Steel Selection
We offer our scupper plugs in the following material grades to match every marine environment:

• AISI 316L (1.4404): The standard for seawater-resistant stainless steel. The molybdenum content provides outstanding resistance to pitting and crevice corrosion in chloride-rich seawater, making it ideal for all saltwater deck drains, bilge connections, and exposed weather deck applications. It is non-magnetic and easily passivates to maintain a bright, clean surface.

• Duplex Stainless Steel (UNS S32205 / 1.4462): For demanding environments requiring both superior corrosion resistance and high mechanical strength. Duplex grades are specified for sub-zero temperature service, high-velocity drainage, and applications where the plug may be subject to impact or vibration. Its high yield strength allows for lighter designs without compromising safety.

• Super Duplex / 6Mo Grades: Available for extreme chemical environments, sour gas exposure, or high-temperature wash systems where standard stainless steel would be challenged.
  All plugs are supplied in the passivated condition to optimize corrosion resistance and are fully traceable to the originating mill.

2. Design and Construction Features

• Threaded Plug with Captive Washer: The most common design is a male-threaded plug with a square, hex, or wing head for easy hand-tightening. Threads are precision-machined to BSP (parallel or tapered), NPT, or metric standards, ensuring a perfect match with the scupper body. A captive flat sealing washer in EPDM (for seawater and freshwater), NBR (for oil and fuel), or PTFE (for chemicals and high temperatures) is recessed under the head to form a reliable, replaceable watertight seal.

• Tapered Friction Plug: A smooth, precision-ground taper designed to be driven into a plain-bore scupper sleeve with a few light mallet taps. The all-stainless construction eliminates the risk of galvanic corrosion in the taper seat and provides an instant, reliable seal for emergency or temporary use.

• Integral Chain and Retaining Fitting: Every plug is supplied with a stainless steel (AISI 316L) link chain and a deck attachment padeye or shackle. The chain is securely welded or pinned to the plug body, ensuring the plug is always ready at hand and cannot be lost overboard.

• Optional T-Bar or Wrench-Operated Head: For larger diameters or where higher sealing torque is required, a T-bar or hex-head plug can be provided, allowing use of a standard wrench.

3. Key Technical Benefits

• Absolute Corrosion Immunity: Stainless steel, particularly 316L and duplex, does not suffer from dezincification, rust, or intergranular corrosion in marine atmospheres. The plug remains functional and visually clean for the life of the vessel, even on exposed foredecks and helicopter decks.

• Hygienic and Easy to Clean: The smooth, non-porous surface is easily sanitized and does not harbor bacteria, making it the required choice for potable water drains, galley scuppers, and hospital areas on cruise and naval vessels.

• High Temperature and Chemical Resistance: Combined with PTFE or FKM sealing washers, stainless plugs can seal drains handling hot condensate, aggressive chemical spillages, and washdown at temperatures that would soften or damage plastic or rubber-bodied plugs.

• Superior Mechanical Strength: The high tensile and yield strength of stainless steel means the threads will not strip, the head will not round off, and the body will not deform even under heavy use with wrenches or repeated mallet blows.

• Non-Sparking and Fire-Safe: Austenitic stainless steels are non-sparking on impact and retain their structural integrity far better than aluminum or plastic in a fire, contributing to vessel safety in hazardous zones.

4. Typical Marine Applications

• Weather Deck Scuppers: Primary drainage control on exposed main decks, poop decks, and forecastle decks, where continuous salt spray demands maximum corrosion resistance.

• Cargo Tank Decks on Chemical and Product Carriers: Resistant to acidic, alkaline, and solvent cargo residues washed down through deck drains.

• Passenger Vessel Sanitary Areas: Washbasins, showers, galley sinks, and pool deck drains, where hygiene and polished appearance are paramount.

• Potable Water and Demineralized Water Tank Drains: Stainless steel eliminates the risk of metal ion contamination.

• Helicopter Deck and Offshore Installation Drains: Withstands jet fuel spillage and fire exposure requirements.

• Emergency Damage Control: Tapered stainless steel plugs in damage control kits for immediate, reliable sealing of broken pipes, small hull penetrations, or severed scupper lines, in any service fluid.

• High-Pressure Washdown and CIP Systems: Withstands the thermal and chemical stress of Clean-in-Place cycles on food-grade and pharmaceutical vessels.

5. Quality Assurance, Testing, and Certification

• Material Certification: Full EN 10204 Type 3.1 material certificates are provided as standard for all stainless steel components, confirming the exact alloy composition (including Cr, Ni, Mo, and N for duplex grades), mechanical properties, and corrosion test results (pitting resistance equivalent number PREN). Traceability is maintained from the steel mill to the finished plug.

• Dimensional and Functional Inspection: Every plug is checked for correct thread form, taper dimensions, and surface finish. Chain assemblies are proof-loaded to a factor of safety compatible with maritime lifting and securing gear standards.

• Leak Testing: On request, plugs can be hydrostatically or pneumatically tested to demonstrate seal integrity at specified working pressures, with test certificates supplied.

• Permanent Marking: Each plug is laser-marked or dot-peen marked with the material grade (e.g., “316L”), the nominal size, and the manufacturer’s mark for lifetime identification.

• Classification Society Acceptance: While not typically subject to individual type approval, our stainless steel scupper plugs are manufactured from materials and to workmanship standards fully accepted by all major IACS classification societies (ABS, DNV, LR, BV, CCS, NK, KR, RINA, etc.). Certificates of Conformity, material test reports, and functional test certificates can be supplied to support your vessel’s survey.