A two-piece ceramic ferrule with a bayonet lock between head and stem, for waste heat boiler tubesheets.
Head and stem move on their own,
and a twist keeps the stem where it belongs.
A twist lock ferrule shortens tubesheet installation because the ferrules arrive fired, sized and wrapped, slide into the tubes and lock with a turn: there is no castable to form and cure between them, only a narrow ring at the edge of the tubesheet. In the ProLok design the stem sits deep in the head and engages with a bayonet lock, so it cannot walk out of the tube under vibration. The head can pivot slightly and settles into its own position on a warped tubesheet as the boiler heats up.
In a one-piece ferrule, head and stem meet in one place, and thermal stress concentrates there. Separating the two removes that stress point and lets each part expand on its own.
Sinking the stem deep into the head shortens its free length and lowers the stress on it. It also lets the head pivot slightly around the stem, so it follows a warped or out-of-spec tubesheet instead of fighting it.
Other two-piece designs carry a known risk: stems that work loose and fall out of the tubes in service. ProLok answers it with a bayonet lock cast into head and stem. The lock holds the two parts together and still lets them move against each other. ProLok is patented under US Patent 8,646,515.
Two pieces give the ferrule room to move with the tubesheet; the twist lock makes sure that room never turns into a loose stem.
ProLok is usually combined with the Thermal Management System, a pre-fired tubesheet protection that replaces most of the castable with fiber.
Waste heat boilers after sulfur recovery units, thermal oxidizers and other process units in refining and chemical processing, especially where the tubesheet is large or out of flat, or where the boiler vibrates.
If your boiler runs round ferrules in castable today, the first question is whether hex heads alone solve the problem. That comparison is on the page for round and hex head ferrules. For secondary reformer boilers with alloy tube inserts, a hybrid ferrule with a precast ceramic head is often the better fit.
Blasch developed its first two-piece ferrule in response to requests from operators, then added the twist lock to stop stems from backing out. The ferrules are cast near net shape in Albany, New York, with a wide range of tapered inlet and outlet profiles.
The work at the tubesheet is fitting and turning, not mixing and curing.
Each ferrule arrives fired, sized for its tube and wrapped in the fiber it needs.
A short twist engages the bayonet lock, and the stem can no longer back out.
The ferrules slide into the tubes row by row, with nothing between them and a narrow castable ring only at the edge.
Each head shifts slightly around its stem and settles into its own position as the boiler heats.
Not with the lock engaged. The bayonet lock holds the stem in the head, while head and stem can still move slightly against each other.
Yes. The head pivots around the stem, so each ferrule finds its own seat as the boiler comes up to temperature.
Yes. Blasch sends a sample on request, so your crew can try the twist lock in your own tubes.
Tube outside diameter, wall thickness, pitch, the tolerance of the tube centers, temperatures, gas composition and the tubesheet thickness. No drawing is needed.
Send the tube data and what you see at the tubesheet today. A Blasch engineer checks whether ProLok fits your boiler.
