Lug

Marine lug butterfly valves are used in shipboard piping systems where flow isolation is required together with mechanical support through threaded lugs integrated into the valve body. The lug design allows bolting from each flange side independently and is commonly assessed for arrangements where one side of the pipeline may be removed for maintenance, provided the application, pressure rating, and loading direction are permitted by the manufacturer.

This category includes the Alfa Europe S64 butterfly valve, lug type, with bonded liner and face-to-face dimension to EN 558-1 Series 20. The range covers DIN, ANSI, and JIS drilling patterns, with flanged connections suitable for DIN PN6, PN10, PN16, PN25, ANSI B16.5 Class 150, and JIS B2211 5K/10K. Nominal sizes are stated from DN40 to DN1200, with temperature limits from -40 to +250 °C depending on seat material, body material, and actual service conditions.

Available body materials include EN-JS 1030 ductile iron, stainless steel 1.4408, ASTM A216 WCB, and aluminium bronze BS 1400 AB2. For seawater circuits, aluminium bronze is often considered because of its behavior in marine corrosion service, while ferrous body materials require suitable surface protection and confirmation of compatibility with the process medium. The NBR seat should be checked against operating temperature, chemical compatibility, oil content, and potential wear caused by suspended solids.

Valve selection should verify flange class, operating torque, differential pressure, disc clearance, pipe alignment, and access for lever, gearbox, or actuator installation. In throttling duty, disc angle and flow velocity affect noise generation, vibration, liner wear, and shut-off tightness. Maintenance review should also include seat degradation, stem sealing condition, and allowable leakage rate for the intended service.