Selecting the Right Coolant Fluid

Coolants for a range of applications

High Speed (4 Cycle) Reciprocating Engines  

High speed engines contain replaceable cast iron cylinder liners. These liners can experience accelerated corrosion as a result of a process commonly referred to as liner cavitation or liner pitting. This occurs as a result of continuous growth and collapse of bubbles on the wet sleeve liner due to the piston motion within the cylinder. When the bubbles collapse, the large force generated by the collapse stresses the surface of the liner, causing small pits to be drilled into the surface. This can cause significant damage to the liner through repeated wear and stress, and repairs often require considerable downtime as the liner must be removed and the engine relined. If left too long, these pits will turn into holes causing a leak and the engine will shut down. Because of this erosion/corrosion phenomenon, high speed engines have specific needs when it comes to coolant selection.  

Dow’s NORKOOL™ SLH coolant is specifically designed to address liner cavitation. By chemically forming a harder, less permeable surface on the liner, NORKOOL™ SLH can greatly reduce or eliminate liner cavitation. The types of engines where NORKOOL™ SLH is recommended include White Superior, Waukesha, Ingersoll, CAT, Wartsila and MEP Fairbanks Morris engines.  

Slow Speed (2 Cycle) Reciprocating Engines  

While natural gas transmission pipelines most commonly employ high speed engines today, many slow speed engines continue to remain in service. These engines include Cooper, Clark, Worthington, Dresser, and others. These engines are no longer in production but still make up a significant part of transmission horsepower across the United States. While no new installations are occurring, coolant selection continues to be relevant. Because slow speed engines typically do not experience liner cavitation, AMBITROL™ is recommended for use in these types of engines.  

For stations utilizing both slow and high speed engines, maintaining and storing two different coolants can be difficult. NORKOOL™ SLH is recommended as the best coolant for both.

Line Heaters and Indirect Line Heaters

Line heaters present a rather unique chemical challenge for corrosion protection. With no means of circulation other than from convection (fluid movement due to heat), corrosion protection can be difficult. The reduced circulation does not allow most heat transfer fluids to adequately protect metal surfaces. Furthermore, cleaning and replacing the coolant in a line heater is difficult because they are often located in remote areas and can be physically hard to get to. Choosing the best heat transfer fluid for maximum longevity is key. NORKOOL™ SLH is specifically designed to protect metal surfaces in the system at low circulation rates. The inhibitors in NORKOOL™ SLH react with the carbon steel surface of the line heater, forming a strong barrier to reduce corrosion.


Often compressor stations will use an on-site boiler as a heat source for the location to heat buildings and hot water systems. When properly maintained, AMBITROL™ will protect the boiler system from corrosion while maintaining temperatures for as long as fifteen or twenty years without replacement.

Other applications

For other applications requiring glycol-based coolants, please contact your Dow Representative for assistance in selecting the proper coolant. Those applications include:

  • Crude oil heaters
  • LNG vaporizers
  • Natural gas well head heaters
  • High speed stationary engines in chemical plants
  • Air compressors

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