MyCleanDiesel Webinar: Why do Carboxylates Plug My Filter?

Watch the webinar

Donaldson Filtration Solutions | August 3, 2016

Overview of carboxylates and why modern engines can no longer tolerate them, why it is impossible to prevent them from forming, discussion of filtration solutions

  • 3 problems causing filter plugging: biodiesel blends forming glycerin solids; additive blending issues such as cold flow improver misuse; carboxylates
  • Carboxylates – exact form and reactions are still being learned; basic understanding is diesel deposits – sodium soaps
  • Carboxylates have been problem for years, but have become more so since introduction of modern HPCR engines
  • Tolerances in older injector units ranged from 6-7 microns, which mean that typical 7-10 micron filtration typically found on diesel engines provided adequate protection, but 97% of particulate debris was smaller than 7 microns and not causing damage to fuel system or plugging fuel filter; small portion of 1-3 micron particulate were caught by filter or left deposits on engines, but not sufficient to cause immediate issues
  • HPCR injectors, have 2-3 micron open tolerances (to go along with higher pressure injection systems) and very sensitive to 2-3 micron particulates; new engine fuel systems have filters that needs to keep all 2-3 micron particulates and larger out of fuel systems; 2-3 microns is size of carboxylates; same fuel that contributed to beginning of deposit in old engine will rapidly plug filter in new system;
  • Most issues with filter plugging are because of engine requirements for extremely clean fuel; “fuel manufacturers and suppliers continue to do a professional job with delivering a quality product, it’s just that the rules of the game have changed. Fuel that is 100% adequate for an old system may plug filters on a new system 500-1000x faster than expected”
  • Carboxylate Chemistry – salt or ester of carboxylic acid (organic group); compound is more stable if it can take an electron from something else in the fuel – typically alkaline metals (sodium, potassium, tank bottom water); highly fuel and soluble materials (once they are formed, they will not re-dissolve into the fuel)
  • Most common cause of carboxylate formation is from reaction from common corrosion inhibitor chemistry and sodium ions found in a high PH condition; can occur in fuel manufacturer, before transport, or possibly in tanks with high PH conditions in tank bottom water
  • Another formation is caused by reaction of common corrosion inhibitor and portion of some premium cold flow improver (added at terminal or closer to dispension site)
  • So small they don’t settle to tank bottoms and get filtered out; old filters allowed them to pass through, which is why they would cause deposits on injectors over time; now the particles get hung up in the high efficiency filters and cause premature plugging
  • They are generated in very specific conditions (corrosion inhibitor, sodium, and high PH conditions) – this form is typically formed before fuel is delivered to terminal; fuels will likely meet all applicable standards and considered fit for purpose – difficult to prevent delivery of fuel with carboxylate issue in the fuel
  • Ingredients contributing to formation are ubiquitous – cannot prevent them from forming and being delivered, but can prevent them from getting into fuel tank and equipment by filtering fuel at tanks before it is put into equipment, when using cold flow improver, use detergent

Read more on other literature review summary.