Spray Bar End Cap and Drain Plug

Function

During spraying the end cap holds manifold pressure, typically 2–4 bar (29–58 psi). At the end of a session, the drain plug is removed to allow residual bitumen in the bar to return to tank before the machine cools. A blocked or missing drain plug traps hot bitumen in the bar; on cooling it skins and carbonises, clogging nozzles and requiring time-consuming chemical or thermal cleaning the following morning. A cracked or weeping end cap is also a safety hazard given the temperature of the material inside.

Construction & quality

Body: carbon steel or 316L stainless steel (to application environment). External surface: high-build epoxy or bitumen-resistant paint system. Drain plug: hex-head carbon steel or stainless with PTFE-thread-seal or bonded nitrile washer seat. Thread form: BSP throughout. Body rated working pressure PN10. Optional integral ball-valve drain point is available for zero-spill drain on circuits where gravity drainage is not practical. Thread engagement length is sufficient to resist the bar vibration loads without requiring thread adhesive on routine service replacements.

When to replace

• Bitumen seep or weep around the cap-to-bar joint under spray pressure
• Drain plug thread stripped or cross-threaded — plug falls loose under vibration
• End cap body shows cracks, pitting or severe corrosion on external inspection
• Bitumen stain marks around the base of the cap after overnight cooling
• Drain plug seized and cannot be removed for bar flushing at end of shift