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How to increase reliability and pump lifetime in ethylene oxide service

There are several challenges associated working with ethylene oxide (EO) – its flammability, reactivity, explosive vapour decomposability, and toxicity. It is imperative to use equipment, including all of its components and materials, that are compatible with EO. Greg Gedney reports

If you list the most important chemicals used in industrial processes, Ethylene Oxide (EO) is bound to be there.

The colourless gas is an essential chemical building block, after all. It is one of the most valuable and versatile compounds which is primarily used as an essential intermediate in the production of several industrial chemicals. These chemicals provide the raw material for textiles, detergents, antifreeze, solvents, adhesives, and medicinal products. EO is also a sterilant for medical equipment and a fumigant for foods and textiles.

EO is both flammable and highly reactive under ambient conditions. This highly reactive nature is one of the main reasons why EO is such a versatile and important chemical intermediate. The tendency to react readily with other chemicals is also what presents many hazards, such as explosions. Some examples include an EO explosion at a chemical factory in Spain in 2020, which was powerful enough to propel a one-ton steel plate nearly two miles, where it crashed into an apartment building. About a decade ago, a chamber containing 100 pounds of the gas detonated, launching a two-ton metal door 75 feet away which injured four workers at a sterilisation facility in the US.

Beyond EO’s explosive nature, it is also very toxic. Significant exposure can create an increased risk of adverse health effects, including blurred vision, difficulty with breathing, breast cancer, and nervous system conditions.

Safety measures and effective sealing of this valuable but potentially hazardous gas are therefore critical to prevent explosions and avoid leaks.

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 vapour 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 utilise 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-fibre filled PEEK bearings that were swelling in EO media. The excessive swelling of the bearings 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 bearing material to handle the harsh processing conditions of the EO service. We recommended replacing the carbon-filled PEEK bearings with WR600 bearings, a carbon-fibre-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. WR600 is a non-galling/non-seizing composite material, which allows the bearings to be designed with tight clearances, leading to improved efficiency and longer life. As a result of changing the pump bearings 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 utilise 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, optimised for EO applications, could reduce the possibility of equipment failure.

A leading chemical company located in Eastern Germany experienced repeated failure of multiple FFKMs due to EO exposure. This resulted in unplanned maintenance of their screw spindle pumps every few weeks. They contacted Greene Tweed to help increase the MTBF of their pumps from several weeks to several years, while improving safety at all pump installations.

Following a careful evaluation of the application and its operating parameters, we proposed Chemraz 505, an FFKM that provides a wide range of chemical resistance. After successfully trialing Chemraz 505 in an R&D pilot EO service plant, the chemical company specified Chemraz 505 for all screw spindle pumps throughout the plant.

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 505 seals for rotary pumps, chemical plants in EO service can:

Significantly reduce lifecycle costs

Greatly improve MTBF

Increase equipment efficiency

Greg Gedney is Industry Expansion Manager, Greene Tweed.

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