Precast ferrule systems that protect the tubesheet without a castable slab in front of it.
The ceramic ferrule protects the tubesheet.
The way the ferrules are joined decides how long it lasts.
For a waste heat boiler tubesheet, the most reliable ceramic ferrule is usually a precast system with no castable between the ferrules: one-piece hex head ferrules that close into a continuous face at operating temperature, or two-piece ProLok ferrules where the tubesheet is warped or the boiler vibrates. Round ferrules set in castable cost less as parts, but they bring back the large castable slab that cracks. Gas temperature, inlet profile and the outage time you have decide between the two.
In a castable system, one layer does two jobs. It holds the ferrules in place and it insulates the tubesheet. Large areas of castable go through high thermal and mechanical stress at every heat-up and cool-down, and they crack. Each crack is a short way for the process gas to reach the steel.
Blasch ferrule systems split the two jobs. The precast ferrules carry the structural load, and fiber insulation does the insulating. With the Thermal Management System, a pre-fired tubesheet protection used with ProLok ferrules, fiber fills the space behind the heads and gives more insulating value than castable in a thinner layer.
With precast ferrules, damage stays where it starts: one cracked ferrule is one tube to fix, not a slab of castable to break out.
Each option keeps castable out of the space between the ferrules. The difference lies in how head and stem are made and held.
Head and stem in one casting. The hex heads close into a gas-tight face at temperature, sealed by a fiber gasket in a groove.
Head and stem cast separately and locked with a twist. The head can tilt slightly to sit flat on a warped tubesheet.
Pre-fired tubesheet protection that puts fiber insulation behind ProLok heads in place of castable.
No forming, no curing of a full castable layer, and no special tools at the tubesheet.
Each ferrule arrives sized for its tube and wrapped in the fiber insulation it needs.
The ferrules slide into the tubes row by row, starting at the bottom of the tubesheet.
A narrow ring of castable fills the gap between the outer ferrules and the boiler wall, and nothing goes between the ferrules.
At operating temperature the heads grow toward each other and close the face.
The profile of the ferrule inlet and outlet changes the pressure drop through every tube. A published laboratory study compared profiles with air at room temperature. The results are relative, not operating values, but the ranking is clear.
| Ferrule profile | Total pressure drop, ferrule plus tube |
|---|---|
| Tapered inlet, chamfered outlet | lowest, the reference |
| Chamfered inlet and outlet | about 10% higher |
| Sharp edged inlet and outlet | more than 35% higher |
The same study put a price on it: in a boiler with 500 tubes at a gas velocity of 172.5 ft/s and power at $0.05 per kWh, 20% more pressure drop at the ferrules costs about 43 kW, or roughly $18,800 per year.
Turbulence behind the ferrule exit can concentrate heat on the first inches of the tube. In 2005, a US refiner and Blasch developed a patented ferrule design that lowers this peak heat flux, and in 2017 the refiner reported longer boiler tube life from it at the Brimstone Vail conference. The background is in the paper on ferrule and tube design against film boiling.
Blasch ferrules are cast in high alumina compositions, up to 99% alumina, and fired under controlled conditions in the plant. Their properties do not depend on weather, field curing or the skill of the installer. More on alumina ceramics.
Mortar between ferrules is crushed when the heads expand and falls out after repeated cycles, which leaves a direct path to the tubesheet. Blasch ferrules are designed to close at operating temperature without it.
Waste heat boilers in sulfur recovery, sulfuric acid, thermal oxidizers, steam methane reforming, secondary reforming, FCC and titanium dioxide plants, mostly in refining and chemical processing.
Yes. A sample ProLok ferrule is available on request, so your crew can check the fit and the lock in your tubes.
No. Tube outside diameter, wall thickness, pitch, operating temperature and gas composition are enough to design the ferrules.
Send the tube size, the pitch and the gas temperature. A Blasch engineer proposes a ferrule system and the inlet profile for your boiler.
