Filtration Cart Amp Draw Problems Solved

Mark Mcclatchey, Liquidynamics
Tags: contamination control, filter carts

When considering the purchase of fluid filtering systems for lubricants, it is prudent to consider electrical requirements along with filter system specifications vs. requirements. This helps prevent downtime and delays due to limited existing electrical circuit resources. This review discusses areas of concern as well as a unique solution.


Figure 1. High-viscosity Filter Cart

Electrical Considerations
Typical electrical items to consider in order to minimize difficulties in operating a fluid filtering system should include the following:

  • Determine the full load amperage requirement for the new filtration equipment.

  • Identify the electrical outlets that will be used to provide power to the filtering system. Keep in mind that it is best to use the closest available outlet in order to minimize voltage drop due to long extension cords.

  • If an extension cord must be used, use the shortest and heaviest gauge feasible.

  • Determine if the outlet to be used is rated at 15 or 20 amp. The 20 amp outlet can be identified by the fact that the larger of the two vertical slots (neutral) will have a small notch on one side.

  • Check the circuit breaker that feeds the intended outlet to determine its amp rating. These are clearly marked.

  • Determine what other electrical items are being serviced by the designated circuit breaker and what the amp ratings are of these items. Subtract the total of these items from the amp rating of the breaker. This is the amperage that is left to run the new filtration system.

  • If in doubt, have a licensed electrician make the above determination.

Viscosity and desired flow rate are key factors determining motor size and amp load. Often it is necessary to accept a lower flow rate in order to keep motor loads under 15/20 amps. It is commonly accepted that the slower a lubricant passes through a filter, the more efficient the filtering process will be. This, of course must be balanced with quantity of lubricant to be filtered, how many ISO cleanliness codes (or levels) must be dropped (or decreased) to meet the desired cleanliness standards and how much time will be allotted to complete the task.


Figure 2. Control Module

Rule of Thumb
A popular rule of thumb: when filtering a tank or reservoir with a kidney loop filtration system, using filters with beta ratios greater than 200 requires turning the tank volume six to seven times to drop the ISO cleanliness code by one number. Of course this is an approximation, because actual turnover volume required depends on quantity of particulate contamination and how much sediment has accumulated at the bottom of the tank. Using the rule of six to seven turns would mean that if 1,000 gallons of lubricant needed to be brought down two ISO cleanliness levels, using a typical 5 GPM pump and filter system:

1,000 gallons x 7 turns = 7,000 gallons / 5 GPM = 1,400 minutes / 60 minutes = 23 hours per cleanliness level or 46 hours for two cleanliness levels.

Compare this to a 20 GPM system which accomplishes this same task in 5.8 hours per cleanliness level or 11.6 hours for two cleanliness levels. Unfortunately, low flow rate systems are typical in the industry in order to minimize problems with amp draw and nuisance tripping of circuit breakers.

Higher flow rates are desirable not only to shorten filtration times, but are useful to stir up sediment that has accumulated on tank/reservoir bottoms to allow thorough filtration. Otherwise, each time oil is added, sediment is stirred up and introduced into the system. Properly cleaning these tanks is accomplished by using a return probe that extends to the tank bottom, creating turbulent flow, stirring up accumulated sediment, and lifting it into suspension, thus allowing removal by the filter.

Filter Carts
Liquidynamics, Inc. of Wichita, Kansas has introduced a new selection of PureLube Filter and Transfer Carts that allow flow rates up to 20 GPM without the inherent problem of tripping 15/20 amp circuit breakers in 115 VAC circuits. This is accomplished via a patent-pending PowerMaster controller that includes proprietary software to monitor available current and automatically adjusts current usage via motor speed in order to stay below the user-selectable 15 or 20 amp requirement. The PowerMaster will respond to real-time changes in circuit amperage availability.

Therefore, if another device in the circuit requires additional power, the PowerMaster automatically adjusts to this requirement by reducing the speed and thus the amp load of the filter cart. This system also allows the user to manually adjust pump speed in order to "polish" fluid at low flow rates if desired. Filter element life may also be extended by adjusting flow rate to maintain optimum filtration performance. Whereas, fixed flow rate systems obligate one to change filters when maximum differential pressure is exceeded.


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