Application
Valve and Airlock Selection for Building Materials Plants
Answer in brief
In a cement or lime plant the valve is a wear part, and the only question is how long it lasts and how quickly it can be changed.
Fine mineral powders open rotor clearances steadily, and the first symptom is not a leak you can hear but a conveying line that no longer reaches its rate.
- Specify wear protection and the inspection interval together.
- Measure leakage over time, not once at commissioning.
- Keep spares for the parts that are known to wear.
Reviewed October 21, 2026 · Updated October 21, 2026
The problem
Cement, lime, gypsum and fly ash are fine and abrasive, and they erode rotor tips, housings and valve seats at a predictable rate.
As the clearance opens, conveying gas leaks back through the valve, the pickup point starves and the whole line loses capacity.
Desired outcome
A valve whose wear rate is known, whose leakage stays within the conveying design for a defined period, and which can be restored without cutting the line apart.
Process approach
Hardened or lined rotors, replaceable wear plates and adjustable tip clearances extend the useful life considerably over a standard cast valve.
Where the material is hot, as with cement leaving a mill, thermal expansion has to be in the clearance calculation or the rotor will rub.
Slide gates under silos see the full material column and need a blade design that is not forced to cut through a settled bed.
- Wear-resistant surfaces at the tips and in the housing bore.
- Clearance checks as a scheduled task rather than a reaction to a problem.
- Access and lifting provision, since these valves are heavy.
Selection factors
- Particle size and hardness of the actual product, including recycled or alternative materials.
- Operating temperature, especially downstream of a mill or calciner.
- Permitted leakage for the conveying system and how performance will be monitored.
- Access for inspection and rotor replacement.
- Whether the valve must hold a pressure boundary or only pass material.
Common failure modes
- Clearance opening until the conveying line loses capacity
- Rotor rubbing after thermal expansion in hot service
- Gate blade jamming in a settled material column
- Wear parts not available when the line stops
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