A short video on the cast in bayonet lock that joins head and stem of a two piece ProLok ferrule.
Two pieces, one turn.
The stem locks into the head and stays where it was set.
The ProLok video shows the twist and lock feature of Blasch ProLok two piece ferrules: a bayonet cast into the ceramic joins the stem to the head with a turn. Because the stem sits deep in the head and is locked there, it cannot walk out of the boiler tube under vibration, while the fiber seal between head and tubesheet stays in place.
The camera follows one ferrule from two parts to one. The stem slides into the head, a short turn engages the bayonet, and the assembly is ready to go into the tube. The lock is part of the casting, so there is no pin, clip or adhesive to fail at temperature.
In a waste heat boiler, ferrules protect the tube inlets and the tubesheet from the hot process gas. A two piece design separates the head, which forms the hot face, from the stem, which shields the tube. Without a lock, vibration in the boiler can push stems out of position over a campaign and open a path for hot gas to the tube.
A ferrule that stays exactly where the installer put it is the reason the tubesheet behind it never sees the gas it was built to keep out.
If you have found stems pushed out of their tubes at inspection, or loose ferrules after a campaign with vibration, the twist and lock answers that specific failure. For boilers without vibration problems, a one piece hex head ferrule may be the simpler choice.
The full design is on the page for ProLok twist lock ferrules. The other designs are compared under round and hex head ferrules, and the ceramic ferrule installation video shows how a tubesheet is fitted from bottom to top.
It stops the stem from walking out of the tube under vibration, so the head and the fiber seal stay where they were installed.
No. The bayonet is cast into the ceramic of head and stem. There is no separate fastener in the hot zone.
Yes. The head can tilt slightly and finds its own seat as the boiler heats up.
Send the tube outside diameter, pitch and tubesheet thickness. A Blasch engineer works out the ferrule from those dimensions.
