Can you pump this fluid?

A question that we frequently receive is: “Can Dynex pump my fluid?” The answer depends on a number of factors.

Dynex reviews and applies our product on many fluids across multiple industries. This article will give you some insight into what we look at when evaluating a fluid.

As a baseline, Dynex tests our products in one of these fluids:

  • ISO32 Hydraulic Oil at 110  ͦF
  • McDermid HW443 Water Glycol at 100  ͦF
  • Skydrol – Hyjet IV (Coming soon to Ashland, MA facility)


What are the key factors in reviewing a fluid for any product application?



This is defined as a resistance to flow or essentially drag. The lower the viscosity, the more likely the pump will have internal leakage and reduce its volumetric efficiency. The optimum range we look for on most products is between 20-70 cSt. or Centistokes. This does not apply to our PF1300 and PF4300 product as they are designed to operate on much thinner fluids. The viscosity at 100  ͦF for HW443 is approx. 2.5 cSt.


All pump components which are in contact and under load during operation will experience wear.  The rate of wear and life expectancy of the components is affected by lubrication between those components.  Dynex pumps are unique because they are a single fluid design—the fluid being pumped also provides lubricity between components.  Lubricity is generally related to viscosity, but two fluids with same viscosity might prove to offer different lubricity characteristics. 

Dynex developed a method for evaluating lubricity. With this testing method, we can assign an index number from .5 – 50. The lower the number the better the lubricity is. To do this, we need about 1-2 liters of the fluid for testing.


Temperature can have a major impact on viscosity. Some fluids get exponentially thinner as the temperature increases, while others stabilize at certain temperature points. It is important to take into consideration what the operating temperature of the fluid be.

Material Compatibility

Depending on the fluid, there is a chance that it may have a reaction with the materials that a pump is constructed from. An example is water glycol fluids and their reaction with aluminum and other alloys, as compared to steel and stainless-steel alloys. In addition to the material compatibility of the product, it is important to evaluate the compatibility with any surface treatment, such as paint, that could have a reaction. A classic example of this is Skydrol and its effect on most paints applied to finished products.

Seal Compatibility

In conjunction with material compatibility, is the fluid’s ability to react with the elastomers in the product, such as o-rings, backup rings, and any dynamic seals (shaft seal etc.). Fluid data sheets typically provide information on which elastomer compounds are good, fair, or not recommended.

Load Pressure for Pump

Load Pressure affects not only how components of the pump are stressed, but also affects internal fluid leakage. As load pressure increases so does internal leakage. Viscosity has an impact on this. When reviewing viscosity, it is important to understand what the load pressure at the outlet of the pump will be.  


When evaluating a fluid’s compatibility in an application, we look at the above factors to understand how to make a recommendation. These factors include:

  • Viscosity
  • Lubricity
  • Temperature
  • Material Compatibility
  • Seal Compatibility
  • Load Pressure

In addition to these main areas of focus, you should understand the duty cycle of the application. You should also be aware of any safety or hazardous information that could affect the work environment or any operators. This is usually found on the MSDS associated with each specific fluid.

Understanding these factors and how they will impact the performance of a product are key to answering the question, “Can Dynex pump my fluid?”.

Do you know what it takes to pump the fluid in your application?

Tip Ninja

Applying his legendary skills toward answering tough questions, defeating difficult hydraulic related problems, and sharing his vast knowledge of Dynex hydraulic products with the world.