"We have four portable filter carts that are used to regularly filter the four different lubricants in our plant (each is a different viscosity grade). Although each cart is properly labeled and a different color, we are still having cross-contamination problems. Any suggestions?"
When used properly, filter carts can be vital to the reliability of a process. Although filter carts are often used for any fluid needing filtration regardless of chemical make-up and viscosity grade, this is a practice that should be avoided. These carts are rarely flushed out adequately between uses.
The best place to combat misuse of your filter carts is to start with the design. When possible, specify that a manual filter bypass valve is plumbed into the circuit. This will allow you to bypass the filters when you are only transferring used oil and do not need to filter.
Also, specify that the hoses have quick-connects as opposed to simple drum wands. Drum wands are difficult to keep from getting contaminated. Their use requires the system to be opened to the operating environment, possibly allowing contamination to enter the system unrestricted.
Using quick-connects on the filter cart and on the system to be filtered eliminates the need to open the system for filtration or topping up. To ensure the filter carts are used only for the oils they were specified for, you need to take all guesswork out of the equation. One simple way to do this is to install different types of quick-connects on all four of your filter carts. Place the matching ends of the quick-connect on the appropriate equipment where they will be used. Using quick-connects of different types and sizes makes it impossible to connect the filter cart to the wrong equipment and lubricant.