This is the second article in a series on Ethylene Oxide Challenges. Read Part 1 

Companies that manufacture or work with Ethylene Oxide (EO) know that there are several challenges associated with the essential chemical building block – its flammability, reactivity, explosive vapor decomposability, and toxicity. That is why it is imperative to use equipment, including all of its components and materials, that are compatible with EO. 

One such critical piece of equipment is the pump. Specifying the proper materials for pump components, such as bearings and seals, is critical when highly aggressive chemicals such as EO are a factor. Selection of materials that are not compatible with EO can lead to unreliable and unsafe operations.  This could lead to potential loss of production and even worse, lives. 

Eliminate Bearing Swell Issues and Improve Pump Efficiency

Due to the explosive nature and critical safety concerns with EO, several chemical manufacturers utilize custom designed sealless, canned-motor pumps. Chemically aggressive media, such as EO can attack traditional bearing and seal materials. 

That was the case at a major chemical processing plant in Germany that produces EO. The specialty chemicals’ company uses canned motor pumps produced by HERMETIC-Pumpen GmbH, known for their safe and durable pumps under the most extreme applications and in the most hazardous pumped media. These pumps contained carbon-fiber filled PEEK wear rings that were swelling in EO media. The excessive swelling of the wear rings resulted in unreliable pump operation, reducing Mean Time Between Failures (MTBF) to a month and sometimes a week. 

They reached out to Greene Tweed in search of a new wear rings material to handle the harsh processing conditions of the EO service. We recommended replacing the carbon-filled PEEK wear rings with WR®600 bearings, a carbon-fiber-reinforced, PFA-based composite with a maximum continuous service temperature of 500°F (260°C). Its outstanding chemical resistance comes from its constituents, which can withstand virtually all environments, including the strongest acids, bases, halogens, and solvents.  WR®600 is a non-galling/non-seizing composite material, which allows the wear rings to be designed with tight clearances, leading to improved efficiency and longer life.  As a result of changing the pump wear rings to WR600, the chemical plant extended their MTBF from a few weeks to over two years and counting. Encouraged by the results, the chemical plant has specified WR® 600 on all onsite Hermetic pumps in EO service. 

Extend Seal Life

At chemical plants that utilize pumps with mechanical seals, EO is one of the most aggressive chemicals. It can swell most seal materials, causing the seal to fail within a very short time. Selecting a perfluoroelastomer, also known as FFKM, optimized for EO applications, could reduce the possibility of equipment failure. 

Greene Tweed put its high-strength black FFKM, Chemraz® 541, known for its wide range of chemical resistance, to test and reached out to a third party lab investigate its resistance to EO. After exposing samples of Chemraz® 541 o-rings and buttons in liquid EO at a temperature of 27°C and a pressure of 480kPa for a month, the lab determined that the material showed no blistering, cracking, or discoloration and showing little to no change in physical properties as a result of the exposure to EO, showing only slight swelling and softening, decrease in tensile strength, and an increase in ultimate elongation.

The thorough evaluation process confirmed that Chemraz® 541 is ideally suited to meet the rigorous demands of challenging EO applications and processes. Undoubtedly, it is critical for chemical companies working with EO to choose appropriate materials for their applications. By choosing WR®600 bearings for their canned pumps and Chemraz® 541 seals for rotary pumps, chemical plants in EO service can:

Significantly reduce lifecycle costs

• Significantly reduce lifecycle costs
• Greatly improve MTBF
• Increase equipment efficiency