(161e) Silencing Hammering in a Flooded Condenser

Flooded condensers are, and are likely to remain, the prime tower pressure control methods for total condensers generating liquid product only. The principles of these methods had been described in the literature more than 60 years ago, yet these methods continue to rank among the most troublesome distillation controls. Good understanding of the principles and learning from experiencesis the key for avoiding potential traps and improving operation for the industry. This paper describes a recent experience of solving a problem that until now has been unknown and poorly understood in the industry.

 

In its first year in operation, a naphtha splitter experienced intermittent hammering in the line from the tower overhead condenser to the reflux drum. The problem occurred at cold condenser outlet temperatures. In some of the hammering episodes the hammering was severe, opening a flange and causing damage to a valve and a thermocouple.

 

A task force composed of HollyFrontier and Fluor personnel was formed to investigate the hammering incidents. Our task force identified the large open slots at the top of the reflux drum stand pipe as a likely root cause. We also identified total closure of the tower overhead pressure control valve as another potential source of hammering.

 

Based on this review, we blanked the slots near the top of the stand pipe and added a DCS clamp on the overhead pressure control valve that does not allow the valve to close to less than 20%. HollyFrontier also emphasized in their operator training the importance of keeping tight control of the condenser outlet temperature at 180 F. The column was returned to service in March 2015, with no further hammering to date, and experiencing smoother operation.

 

This paper describes our investigation and our solution.