How to Deal With Plate Heat Exchanger Leaks？

Plate heat exchangers (PHEs) are widely used in industry for their stable performance and compact footprint. According to 2025 industry statistics, leakage causes more than 85% of PHE failures. Below is a streamlined guide to the common causes and a five-step repair procedure.

1. Five Most Common Causes of Leakage (by frequency)

1. Gasket failure — Main Reasons

EPDM or FKM gaskets harden, crack and tear under repeated temperature cycling, pressure fluctuations and media corrosion. This accounts for more than 60% of all leaks. Frequent start-stop cycles accelerate gasket creep and can triple the leakage risk.

2. Plate damage

Plates are only 0.5–0.8 mm thick and vulnerable to two types of damage: chloride pitting (seawater, high-salinity media) leading to pinhole perforations, and water hammer (flow velocity spikes above 2 m/s) causing bulging and deformation. Damage usually starts as micro-seepage and can grow tenfold within 24 hours if left untreated.

3. Uneven clamping force

Common errors include non-diagonal bolt tightening (eccentric loading), insufficient torque (inadequate surface pressure) and overpressurization beyond 1.25 times the design pressure — all of which cause local gaping and micro-leakage paths. Units not tightened to the specified torque show a 4.2× higher leakage rate than properly assembled ones.

4. Installation defects

Residue of old gaskets, gaskets folded or not seated fully in the groove, and sand or welding spatter trapped in the gasket channel cause leakage right after commissioning. These are fully preventable faults.

5. Frame deformation

After three or more years of continuous high-temperature operation, the movable pressure plate may warp and the suspension bolt holes can wear, shifting the plate pack by more than 0.5 mm and destroying parallelism. Such deformation usually requires precision instruments to detect.

2. Five-Step Repair Procedure

Step 1. Shutdown and isolation

• Close the high-temperature side valve first, then the low-temperature side.
• Open the vent valve until the pressure gauge reads zero.
• Allow natural cooling to below 50 °C; never apply abrupt cooling.
• Isolate with double valves and hang an "Under Maintenance" tag.

Confirm the system has no pressure, residual heat or flowing media before starting work.

Step 2. Localize the leak

• External leak: clean the plate surface and apply soap solution; the point where bubbles form is the leak location. Use a borescope for hard-to-reach areas.
• Internal leak: monitor low-temperature side outlet conductivity — a rise of more than 15% indicates cross-contamination. Alternatively, run a hydrostatic test at 1.25 times the working pressure for 30 minutes; a pressure drop over 0.05 MPa confirms an internal leak.
• Infrared thermography offers more than 95% localization accuracy.

Step 3. Targeted remediation

• Gaskets: replace the full gasket set; never mix new and old gaskets. Use EPDM for water up to 120 °C, NBR for oil-bearing media, and FKM for high-temperature corrosive media.
• Plates: pits under 1 mm can be sanded with 400-grit paper and sealed temporarily with high-temperature PTFE sealant. Perforations, cracks or bulges deeper than 0.5 mm require plate replacement; the new plate must match the original corrugation angle.
• Bolts: use a calibrated torque wrench and tighten diagonally in three stages — 30% → 70% → 100% of rated torque. Reference values: M16 = 80 N·m, M20 = 160 N·m.
• Frame: if deformation exceeds 0.5 mm/m, contact the manufacturer for professional straightening.

Step 4. Reassembly

• Reinstall plates in the original order, keeping the flow channel arrangement unchanged.
• The movable pressure plate must travel smoothly without binding.
• Final compressed dimension: A ≤ 1.05 × nominal A-measure.
• Record the actual compressed dimension as the maintenance baseline; plate pack parallelism deviation must stay below 0.1 mm.

Step 5. Test before recommissioning

Follow GB/T 29466-2012 (Plate Heat Exchanger Unit):

• Test pressure = 1.25 × design pressure.
• Hold for 30 minutes (60 minutes for critical sections).
• Acceptance: pressure drop ≤ 0.02 MPa, no visible leakage.
• Test medium: clean water with chloride content below 25 mg/L; ambient temperature above 5 °C.

After passing the test, open the low-temperature side slowly, run for 10 minutes, then open the high-temperature side to avoid thermal shock.

3. Preventive Maintenance

• Keep a gasket life record; typical service life is 2–3 years for EPDM and 4–5 years for FKM, and replace gaskets on schedule.
• Install online monitoring of conductivity and temperature for early warning.
• Standardize the five-step procedure as plant SOP; inspect and re-tighten every 8,000 operating hours or once a year.
• Graphene-reinforced gaskets can extend service life by about 40%.

Key principle: replace gaskets on schedule, replace damaged plates without delay, follow the torque specification, and focus on prevention. A disciplined procedure cuts average repair time from 46 hours to under 2 hours and raises equipment availability above 99.5%.