Minor Leakage at Head Plate Gaskets During Start-Up of GPHE with Viton (FKM) Gaskets

Overview

In some gasketed plate heat exchanger (GPHE) applications equipped with Viton (FKM) gaskets, a minor and temporary leakage may be observed at the circular gasket area between the head plate and the first one or two plates during start-up.
This phenomenon is typically transient, occurs only during the initial heating phase, and does not indicate a defect in the gasket material or plate quality. - source: www.hexnovas.com 

Typical Characteristics of the Phenomenon

• Leakage appears only during start-up

• Leakage is usually limited to small droplets or slight seepage

• The location is typically:

  • Head plate

  • First or second plate circular (port) gasket area

• Leakage often stops automatically once operating conditions stabilize

Root Cause Analysis

1. Transient Thermal Expansion Effects

During start-up, the hot medium enters the head plate section first. This causes:

• Rapid thermal expansion of the head plate and the first plates

• Slower temperature rise of the frame, tightening bolts, and tie bars

As a result, the effective gasket compression at the head plate area is temporarily reduced, which may allow minor leakage until thermal equilibrium is reached.

2. Compression Sensitivity of the Head Plate Area

From a structural standpoint:

• The head plate area experiences the lowest and least uniform clamping force

• The first one or two plates are the most sensitive to small changes in compression

Therefore, any short-term loss of effective tightening force will appear first at the head plate gaskets.

3. Material Behavior of Viton (FKM) Gaskets

Viton (FKM) gaskets provide excellent resistance to high temperatures, oils, and aggressive media. However:

• At lower temperatures, FKM exhibits higher hardness and slower elastic recovery

• During rapid temperature changes, FKM gaskets may respond less flexibly than EPDM or NBR

This material behavior can contribute to temporary micro-leakage during start-up, especially in high-temperature or rapid-heating applications.

4. Pressure and Flow Transients During Start-Up

Rapid valve opening or sudden pump start-up can generate:

• Short-term pressure spikes

• Differential pressure fluctuations across the plates

These transient loads may momentarily disturb the gasket sealing line at the most sensitive location — the head plate ports.

Important Clarification

This phenomenon:

• 鉂? Is not caused by gasket damage

• 鉂? Is not caused by plate cracking

• 鉂? Does not indicate internal leakage between media

It is a start-up related sealing behavior and is generally considered a normal operational characteristic under certain conditions.

Recommended Preventive Measures

Controlled Start-Up Procedure

• Gradually increase flow and temperature

• Avoid rapid valve opening or sudden pump start-up

• Allow the unit to warm up progressively

Hot-State Inspection and Adjustment

• After reaching stable operating temperature, inspect the unit

• If necessary, apply minor, uniform tightening, prioritizing the head plate side

• Always remain within the manufacturer’s specified tightening limits

Gasket Material Selection

• For applications with frequent cold start-ups or large temperature gradients:

  • Consider alternative gasket materials if compatible with the media

  • Or select softer or application-optimized FKM grades

Conclusion

Minor leakage at the head plate gasket area during start-up of GPHEs equipped with Viton gaskets is a well-understood and manageable phenomenon.
With proper start-up procedures and correct mechanical adjustment, reliable long-term sealing performance can be fully ensured.