TL;DR
A blocked or low-flow spray nozzle in secondary cooling causes a local hot zone in the strand that can lead to internal cracks. Verify flow in each cooling zone and replace blocked nozzles before the next cast.
What you might see
- spray nozzle blocked in one cooling zone
- strand surface temperature deviation alarm
- downstream surface crack formation on the billet
- coolant flow sensor showing below-design flow
Likely causes
Spray nozzle orifice blocked with scale or debris from the cooling water
Cooling water pressure below the minimum required for atomization
Scale buildup in the spray water header restricting zone supply flow
Nozzle anti-frost heater failed in cold-climate installations allowing nozzle freezing
Required tools
- Nozzle inspection kit
- Replacement nozzles matched to zone specification
- Filter element replacement
- LOTO kit
Safety first
- High-pressure hot water spray in the secondary cooling zone. Lock out before entering.
- Residual hot strand in the strand guide retains extreme heat after a caster stop. Allow cooling or use full PPE.
Procedure
- 1
Read the secondary cooling water flow for each zone from the caster control system. Identify zones reading below the design flow.[1]
- 2
Stop the caster and lock out the strand guide drives before entering the secondary cooling zone.
Warning: The secondary cooling zone contains residual hot strand and high-pressure water spray. Do not enter without lockout and PPE for hot water splash. - 3
Inspect the spray nozzles in the low-flow zone. Remove each nozzle and flush with clean water to check for blockage.[1]
- 4
Replace any nozzle that does not clear after flushing.
- 5
Check the cooling water filter or strainer at the zone header. Replace the filter element if blocked.
- 6
After nozzle replacement, verify the zone flow rate is restored to design before restarting the caster.
Sources
SMS Concast SMS Concast CONROLL Continuous Caster general technical documentation, SMS Concast
General continuous casting secondary cooling system maintenance procedures (general)
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