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The humble plate heat exchanger (PHE) has become an industry standard for efficient thermal management, not only in marine and offshore applications but across wide array of industrial processes. Yet its efficiency and reliability depend on an unsung hero, the gasket. The PHE owes its efficiency and reliability to this unsung hero, the gasket. Select the wrong elastomeric solution and you face premature failure, costly downtime, undesirable cross contamination and ultimately financial penalties. Based on more than 20 years of experience and over 500 retrofit and service projects each year across range of industries SME knows that getting it right, is based on science not an art. This guidance will explore the critical factors required to choose an appropriate long lasting solution.
Understand the Operating Environment: Temperature and Pressure
The first and perhaps the most critical gasket selection factor is thermal and mechanical duty cycle. Because every elastomer has limited “usable” range where time at the high and low end cause age rate to go down, compression set will be experienced with leakage.
Low Temperatures (Below 0°C): Standard Nitrile Butadiene Rubber (NBR) gets extremely brittle, in these temperatures look for Ethylene Propylene Diene Monomer (EPDM) or specialty low temperature grades.
Standard Marine Temperatures (-15°C to 120°C): NBR works well as the common cheap reliable work horse for cooling water and lube oil systems.
High Temperatures (Above 130°C): This is where you’ll find the applications for EPDM (water/steam) or Fluorocarbon (FKM/Viton). Bear in mind, that pressure is inversely proportional to temperature, so when temperature increase, so the max. Working pressure has to decrease. At SME, we verify this with the data from our material range against your relevant pressure spike, to guarantee that there are no pressure issues regarding the necessary compression force.
Chemical Compatibility: The "Media Match" Rule
The application within which fluid flows through your PHE governs the material compatibility you’ll need. As they can cause excessive swelling, hardening or bubbling within gasket material, failure to comply means gasket catastrophe! We categorize fluids broadly into 3 groups, the information provided relating to those fluids that perform well in the below material configurations.
Oils, Hydrocarbons, and Fuels: The go to choice for heavy fuel oil, lube oils, and hydraulic fluids, is NBR, which displays good resilience towards most petroleum based product. For hot oils, and high aromatic type fluids, use FKM.
Water, Steam, and Brine: EPDM is ideal for seawater cooling, freshwater, and steam applications due to its resistance to hot water and steam. However, common mistake is using EPDM in oil applications, the gasket will swell and extrude from the kit and extruded from the plate pack.
Acids and Caustics: Where chemical tankers are being used or scrubbers are in operation the media concentration becomes very important. FKM has wide resistance properties but it may need special compounds of Butyl or HNBR if extremely aggressive chemicals are involved. Our team will always ask for the Material Safety Data Sheet (MSDS) for any chemical media before providing quotation for selection of seal and material.
Evaluate the Mechanical Stress and Compressive Set
While gasket must have something that simply sits, it must retain some “memory” to assure the clamp force fully seals off plate ports against the gaskets. This value is measured by compression set resistance.
Constant Vibration: Continuous vibration takes place in marine vessels. After prolonged compression, the elasticity (or recovery, low compression set) of any gasket is compromised, thereby giving it the tendency to slip, which will create small leaks. While EPDM and NBR will generally perform well over the appropriate temperature range, the nature of the polymer formulation itself is really the key factor.
Plate Design: Different PHE plate designs impose varying shear stresses on the gasket. In our Nantong workshop, we frequently encounter failures where the gasket, though chemically compatible, is too soft for the specific plate geometry, causing extrusion into the flow channels. Gasket hardness (Shore A) is always specified against plate gap and system pressure.
Consider the Service Life and Maintenance Intervals
There's trade-off between the initial investment for gasket and what you gain longterm reliability-wise. Paying significantly more for FKM instead of NBR may be worthwhile if your fluid operates at 150°C and the system requires monthly chemical cleaning, FKM can last five times longer or more.
Warranty and Assurance: Although warranty of 12 full months covers all project work we also inform our clients what their equipment has to do in relation to working hours. In cases where dry dockings are not particularly frequent and the relevant project concerns critical systems, we suggest material upgrade in proportion to the maintenance plan for the vessel.
On-site Reality: Within the brutal marine environment of shipyard, gasket also needs to survive the periodic spraying of cleaning solvents and few bursts with pressure washer. Not only the internal media but the environment as well is taken into consideration in determining its ability to tolerate all external sources which would in due course, be the initiation sites for cracks to start and propagate through the surface.
The Value of Certified Compliance and Genuine Sourcing
Finally, remember traceability, it is vital to supply more than 1,000 vessels each year with our spare parts and we are accredited with ISO 9001, 14001 and 45001. This guarantees our every gasket material is checked against the batch certificate. Substandard imitation gaskets have lower rubber content, higher fillers in the recipe and may give an initially lower price, but it will cost 200% more in operational lost time.
Therefore, we encourage you to take visit out with our technically certified partner who will perform on site measurement of gasket face depth, plate depth and take on rubber hardness measurement. Regardless, be it be in case of fast in-service repair needed at shipyard in the middle of the globe, or scheduled retro in mainland China, the end goal remains the use of correct gasket to ensure your thermal efficiency is not impacted in the long term & your PHE plates' lifetime extended to optimum.