For many years, process industrial plant designers have relied on pumps with ceramic plain bearings. The reason is obvious, this pump can have a long life, and the need for a small amount of maintenance. However, some liquids, due to their physical properties, do not have a long life in use because the liquid is a non-lubricative liquid. Gather process pumps with carbon or plastic plain bearings proved to be particularly suitable for chemical applications in this area. Magnetically coupled gear pumps are particularly suitable for conveying hot solvents , acids, alkalis, water, aqueous solutions, salt solutions and other non-lubricative liquids. For this reason, this type of pump has long been used successfully in various industrial sectors as a process pump:
For example, it is used as a feed pump for organic compounds in the chemical and process industries. Circulating pumps and discharge pumps are used in separators, reactors and evaporators. Since this pump can be constructed from a variety of materials, it can be used even at temperatures up to 300 ° C and system pressures up to 300 bar. In addition, it can be used as a dosing pump for acids, bases, solvents and other aqueous solutions in laboratories , small units or pilot plants.
Specialty Chemicals or Polymer Chemicals use a gear pump to feed the extruder with various additives.
The pump is used in the pharmaceutical industry to prepare broth. In this application it is even possible to "pump" the pumps "online" with steam after the process.
It is used as a dosing pump for ammonia or urea in direct incineration plants for direct nitrogen removal.
It is used in water treatment to deliver water, caustic soda and chlorine bleach.
The reason for the long service life of such pumps is partly due to the fact that over the years, through the exchange with the chemical industry, suitable materials can be selected for each specific application and on the other hand due to the high degree of precision of the individual structural parts Internal friction is particularly small excellent performance.
In order to reach higher temperatures, pressure differentials and longer lifetimes in the delivery of low viscosity liquids with viscosities between 0.1 mPa s (equivalent to methane) and 0.6 mPa s (corresponding to toluene ), a new DLC slip was developed Bearing. For the past due to corrosion and chemical resistance can employ polytetrafluoroethylene (Teflon) as a sliding bearing material and thus limit the application of the pump in the pressure and temperature, which is of particular interest.
Solid combination
Simply put, a DLC coated shaft on a DLC plain bearing rotates in a hardened stainless steel sleeve. The DLC coating is a carbon layer that is firmly bonded to the support material (stainless steel). The advantages of this structure compared to ceramics can be summarized as follows:
The polished stainless steel surface can be much smoother than the surface of the ceramic, it can significantly reduce the friction in the pump.
The firmly bonded DLC coating does not chemically decompose, does not crack and peel off and has good sliding properties when in contact with a non-lubricative liquid, which ceramic does not.
DLC coating is particularly good at chemical resistance. For pump applications, only the chemical resistance of stainless steel and sealing materials can be matched.
Sudden changes in temperature do not cause damage, which is particularly important for applications at 300 ° C. Ceramics break down when the temperature changes suddenly.
Compared to ceramics, DLC coatings are cheaper because they are coated on standard stainless steel shafts and hardened stainless steel sleeves. Does not require expensive tools and structural changes.
If the hardened layer or material sliding layer is abraded, the bearing gap will be great, anyway, to be a maintenance. Ceramic bearings must also be so.
Just to note is that you must ensure that the maximum precision of the structure of the pump, so that the pump can be stable and well run. Gather pump has two series of sliding bearings, transmission capacity of 0.02 ~ 2000l / h.
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