Is there a problem with the design of the ammonia condenser?

This post was last edited by ZLF60137 on 2009-8-12 07:47.
Shell side: Medium – water; Design pressure: 1.0 MPa (the design pressure should be 0.5 MPa; a higher value is unnecessary). Design temperature: 50°C. Material: 16MnR; Thickness: 6 mm; Corrosion allowance: 1 mm.
Tube side: Medium – liquid ammonia; Design pressure: 2.1 MPa; Design temperature: 100°C (the design temperature should be 150°C). Material: 20R; Thickness: 10 mm; Corrosion allowance: 2 mm.
Heat exchange tubes: Specifications φ19x1.2 (it should be above 1.8, taking into account corrosion of carbon steel)； If it’s stainless steel, around 1.2) x8000; Material: 10#

The wall thickness of the tubes is too small, and the heat exchange tubes are connected to the tube sheet using a strength welding plus expansion fitting connection method.

Which specific part is leaking? Is it a leak at the pipe end, or a corrosion leak in the shell side near the tube sheet?

It has penetrated inside the heat exchange tubes, causing ammonia to leak from the shell side to the tube side; no leaks were found at the connections between the tube sheet and the heat exchange tubes.

It could also be a material issue; even if the wall thickness is not up to standard, leakage would not occur so quickly.

We have many liquid ammonia evaporators, whose operational properties are the exact opposite of those of your condensers, but their structure should be similar. In the past, we used 10# and 20# materials for our heat exchange tubes, and tube corrosion and leakage often occurred (usually within no more than 3 years). Later, we switched to 1Cr18Ni9Ti (or similar materials), and throughout the lifespan of the equipment, no such problems of tube corrosion, perforation, or leakage occurred. The shell side is designed with due consideration for the expansion differences between the shell and the tube side; strength welding is sufficient for joining the tubes to the tube sheet

Has the heat exchange tube been corroded, causing a leak? Also, is there any problem with the material?

This post was last edited by daqing01 on 2009-8-16 21:46. The wall thickness of the pipe is a bit thin, but the corrosion caused by liquid ammonia should not be very severe. A 2mm thick tube will work fine for 5 years. Corrosion shouldn’t be the main cause; if it were, it wouldn’t just be one pipe leaking. The operating conditions are the same in all cases, so if there is a leak, it would be on a large scale. It is also possible that the quality of tube manufacturing varies. I think the main reason is that the water flow rate in the tube side is unstable or insufficient; moreover, when the system is started up, stopped, or in standby mode, the valves at the inlet and outlet of the tube side are not closed properly, resulting in water not being completely flushed out. The valves for the liquid ammonia in the shell side are also not tight, which causes the liquid ammonia entering the shell side to vaporize and absorb heat, thereby freezing the pipes. You can use an instrument to inspect the inside of the pipe, and by that you can determine the condition of the leak in the pipe. That device is similar to an endoscope; one end is used to insert into the tube, it has a small light at its front, and it is connected to a monitor outside, allowing for a clear view of the interior of the tube.