How to Identify a Differential Leak in a Plate Heat Exchanger

Introduction

Occasionally, a plate heat exchanger (PHE) can fail when a plate develops a small crack or, in some rare instances, when a gasket is dislodged or damaged. When one of these failures causes the two fluids to mix, it’s called a differential leak. This can be particularly damaging in the food, beverage, and chemical industries and can lead to significant downtime. Fortunately, plate heat exchangers are modular, and once the defective plate or gasket is located, it and an adjacent plate simply need to be removed, and the PHE can go back into service, operating at a slightly decreased capacity until you acquire the replacements. So, how do you find the defective plate? We’ve outlined four simple steps below.

Step 1: Drain, Isolate & Dry

The first step is to drain the plate heat exchanger and isolate it from your system. The actual test relies on water, so you’ll have to wait for all the plates to dry. You can disassemble it now to speed up the process, but you’ll have to reassemble it for the next step and then disassemble it again for the step after that.

Step 2: Water Test

Secondly, water should run through only one side of the plate heat exchanger. Subsequently, each plate will have a wet side and a dry side, but the leaky plate and the adjacent plate will be wet on both sides, so they are easily identifiable by touch.

Step 3: Disassemble

Thirdly, the plate heat exchanger must be disassembled according to the manufacturer’s guidelines. For this step, leaving the plates in the frame is best so you can easily go through them individually.

Step 4: Examine

Last, look at each plate individually and note any that are wet on both sides. Once you’ve removed all the wet plates, you can reassemble the PHE and put it back in service at reduced capacity until you have the appropriate replacement parts.