Abstract: During the operation of the condenser in pressurized tower E334, the upper end pipe plate and heat exchanger pipe nozzle are always corroded first to cause leakage and result in great startup and shutdown losses. Although the condenser can still be used after rush-repair and welding, it will suffer from repeated corrosion and leakage from time to time, and the production has to be interrupted each time an accident is to be handled. The analysis on equipment status showed that the lower end pipe plate and heat exchanger tube were good, so the upper and lower ends were interchanged. Good effect was obtained, the service life of the equipment was extended, and the daily maintenance and update costs were reduced. Of course, to fundamentally solve the corrosion problem of condenser, materials that are more resistant to corrosion in formic acid environment shall be selected, so as to achieve safe, stable, long-term, full-load and optimal operation of the unit. If this modification design is used in a 20 kt/a polyformaldehyde plant, greater economic benefits will be achieved

Key words: pressurized tower condenser, corrosion, modification design