Phosphate ester is synthetic oil that is often used in EHC systems. Filtration is a major requirement in EHC systems because the phosphate esters break down in the presence of water and forms phosphoric acid. The acid that is created is corrosive to many of the components found in the applications. A typical filtration system in EHC systems will contain filters to remove acid, particulates, and a system to reduce the moisture content. Adsorptive type cartridges hold (adsorb) the acids within the crystalline structure of the mineral. There are three types of adsorptive filter cartridges to adsorb the acids in these systems. They are briefly described below:

Adsorptive Filters

Fullers Earth (Clay)
Fullers Earth is a naturally occurring mineral that has strong attraction to adsorb acid. The acid is chemically trapped between the molecular layers of the clay mineral. Fullers Earth is good for mineral acids, but is much better at adsorbing organic polar acids. Fullers Earth has been known to form silica gels that can precipitate into the oil. Although this gel can be removed by particulate filtration, many facilities have switched to Activated Alumina because of its superior acid removal and the fact that Activated Alumina does not have gel precipitate characteristics.

Activated Alumina
Activated Alumina is also a naturally occurring mineral that is processed from bauxite. It has been activated by heat to remove two molecules of water from its crystalline structure. When acid is present, the activated sites react with the phosphate acid and remove it from the ester oil phase. If large quantities of water are present, the activated sites of the Activated Alumina will attract this water and use up its capacity to remove acid. SelexSorb has been developed to over this problem.

SelexSorb
SelexSorb Is Activated Alumina that has been modified. This Alumina can selectively adsorb or react with the acid instead of water. It is effective at removing the phosphoric acid in the presence of large amounts of water without degradation from the water.

Particulate Filters
In EHC systems, particulate is a major concern, as this also reduced the reliability of the equipment. Particulate removing filters are generally manufactured with a resin-impregnated paper that is pleated to maximize surface area and maximize life. They are resistant to moisture and are designed to remove rust, scale and dirt by mechanical means. We offer particulate elements in many sizes that range from ½ micron Beta = 200 to 25 micron Beta = 20. This range will meet the requirement of most applications. In an EHC system, the particulate filter is typically located won stream of the adsorptive filter cartridge. This is to insure that any clay or Alumina dust will be trapped and removed if it escapes from the adsorptive cartridge. These cartridges can be used in most vessels that are already installed if we know the vessel or element part number.

Filter Vessels
We offer single element or multi-element filter vessels in a wide range of sizes, pressure ratings, materials and arrangement that will meet most applications. They can be supplied to meet ASME code or non-code (manufactured to ASME code specifications), and can be equipped with a large amount of options.

Water Removal
While adsorptive filtration is the common method for acid control, water removal or control will eliminate or minimize the formation of acid. Large amounts of water (concentrations greater than 440-PPM or .04%) should not be allowed to accumulate in EHC systems. We manufacturer EHC oil processing equipment to keep the water under control. WE manufacture moisture removal systems that operate at 300, 600, 1200 and 1800 GPH. These systems utilize the process of vacuum distillation to remove water. Vacuum distillation combined with our design makes it possible to achieve dryness levels well below 200-PPM total water. This is a critical level that will maximize the life of the oil (and therefore the components) in EHC systems. In addition, these systems are customized to be compatible with EHC oils. All yellow metals (copper and brass) have been removed, as they are a catalyst in the production of the phosphoric acid when water is present in the oil. The vacuum distillation systems are also equipped with viton gaskets and seals and are painted with urethane paint.