The carryover of heavy hydrocarbons into cryogenic heat exchangers, even at low concentrations, represents a significant risk to reliable liquefied natural gas (LNG) production given their propensity to freeze, deposit, and block flow. Calculating blockage risk requires not only freeze-out temperature predictions but also estimates of where solids will form and the associated operational symptoms. We present here a new simulation tool capable of such predictions in industrial cryogenic heat exchangers, which has been tuned to solid formation data available in the literature. Simulation of the LNG plant upset detailed by Ismail and Al Thani (LNG-18, 2016) confirms the location of the initial deposition that occurred upon restart and provides insights into possible remediation strategies that could have helped avoid the subsequent shutdown. The analysis also reveals that predicting water crystallization in cryogenic LNG systems requires a substantial extrapolation of current thermodynamic models, highlighting the need for definitive measurements under such conditions.