From the first start-up of olefin alkylation plant, we are faced with very frequent plugging and bursting of fresh H2SO4 dozing lines, which causes severe process upsets. In such circumstances, fresh acid is routed to the contactor vessel through "fresh acid fill" piping (which normally serves only in the start-up phase of process after turnarounds), untill regular H2SO4 dozing lines are isolated ball valve, emptied and replaced (safety and environmental hazard). All acid lines are made of carbon steel.It is 98% acid service. The problem with not having heat tracing becomes obvious when introducing these facts: 1. Since process plant is located in the continental area of Europe (winter temperatures as low as -20C), I am kind of suspicious about total elinination of heat tracing. The fresh acid make-up line is almost 200m long, so just with ordinary insulation,I am not sure if this would be enough to prevent crystalization and plugging of the acid line. 2. Temporary shut-downs of Alkylation unit, when acid is trapped inside piping between pump discharge and the process. Without heat tracing, it would be impossible to prevent crystalization of H2SO4, except during summer conditions when ambient temperatures are high enough. Also, the additional problem with steam tracing is galvanic corrosion .

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