Hot oil filtration is a necessity. Thermal cracking and oxidation lead to the degradation of heated oil which results in the collection of sludge and coke. These substances which collect in pump seals and internals, values, etc., cause equipment problems and eventually break down the system. Continuous contaminant, if kept uncontrolled without hot oil filtration, can affect the heating surfaces of your system and thus reduce heat transfer efficiency. There is also a cost factor involved with rapid hot oil breakdown. Hot oil has to be replaced more frequently. Seals, valves, rotors and mag-drive canisters get affected and have to be replaced. Increased maintenance and repair time which would mean higher labor working hours.
Increasing the fluid life with an in-line filtration system
Many system problems cause the oil to degrade prematurely. By installing a side stream or an in-line filtration system, you can increase the fluid life. In-line filters should be used only with positive displacement pumps (gear) not a centrifugal pump. In critical applications such as high-temperature electric systems, a second filter in parallel duplex can be installed. Side stream configuration is recommended for systems with centrifugal pumps. The optimal flow rate through a side stream filter is 10% of full system flow. Minimum recommended flow rate is 3%.
Typical filters embody a canister, which is a metal housing with a fiberglass element labeled as filter or cartridge. Cartridges come in sizes ranging from 5 to 100 microns. For more severely contaminated hot oil systems you can start with a 100-micron cartridge and over time work down to a 5 to 10-micron cartridge.
The inlet of the filter is installed close to the discharge side of the pump. The heat transfer fluid is then diverted to the filter by drawing off the existing pipe, for maximum performance of 10% of the stream. The fluid is cleaned through the filter and then piped back in downstream or to the suction side of the existing pump. Positive shut-off ball valves should be installed on both sides of the filter to allow for cleaning without shutting down the entire system.
Advantages of Filtration
- Filtration removes particulates that can vitiate the oil
- Viscosity of fluid is maintained longer by reducing sludge build-up
- The thermal efficiency of the system lasts longer and you can save on energy costs.
- Prolongs oil life
- Reduced maintenance costs by protecting pumps and valves from contaminates
Many reputed companies provide filtration systems that are incredibly effective for cleaning and maintaining the efficiency of heat transfer fluids, thermal or hot oils. Built for in-system filtration their patented filter housings use proprietary filter elements to enhance optimum cleaning of the oil at elevated temperatures since they can withstand system temperatures of up to 750°F (399°C). The filter elements have an excellent dirt-holding capacity, are economical and disposable. The Sentinel series offers a complete stand-alone system that will re-circulate a portion of the fluid through the filter unit and discharge the clean fluid downstream into the main piping at a pressure higher than the system.
