Pumps with Magnetic Coupling for Polyurethanes
Fillers in PUR are Making Matters More Critical. KRAL Responds with Innovations. To take advantage of PUR materials, manufacturing conditions need to be optimized. The process of mixing base components and additives is critical for product quality. The contribution made by KRAL pumps with magnetic coupling can be crucial here.
Your Advantages
- Carefree-pump, as discharge, transfer or priming pump.
- Avoid damage of the mechanical seal by fillers.
- No damage of the mechanical seal or O-Ring by urea crystals.
- Media-protecting transport without pulsation.
- No blistering at the finished PUR-products.
- Automated, complete venting of the vertically positioned pump.
Polyol is highly viscous at low temperatures. During a cold start-up, high torque is applied to the rotating parts. The mechanical seal, which comes under an ex- treme load, is particularly affected.
The spring of the mechani- cal seal can slip on the shaft. This can cause the spring to disengage and even break. A spring that is disengaged can damage the rotating face to the point of breaking. A mech- anical seal damaged in this way can cause massive pump leakage.
The only lasting remedy is to do away with the me- chanical seal. KRAL pumps with magnetic coupling re- place the mechanical seal. Where previously the me- chanical seals had to be replaced up to three times a year, we now have a "carefree" situation. You simply install and forget!
Fillers are abrasive. Fillers are increasingly being added to polyurethane. Fillers increase the abra- sive properties of the PUR, for grinding tools and terrace slabs, for example. Other fillers reduce flamma- bility or improve electrical insulation properties. Abrasive fillers wear out the mechanical seal, the spindles and the casing of the pump.
The magnetic coupling replaces the mechanical seal, so it is no longer possible to damage the mechanical seal. The con- cept behind KRAL magnetic coupling pumps enables them, on consultation with KRAL, to be designed for numerous fillers by using hardened spindles and pump casings.
Due to it`s lower price, a gear pump could also be considered.
Beware! The disadvantage with gear pumps is that the liquid is exposed to high shear forces and crushing at the gear wheels as they intermesh. This damages the polymer chains, which is why gear pumps are operated a low speeds.
KRAL screw pumps are gentle on the media they deliver at high speeds. This ensures that the power density is efficiently high.
Constructors of PUR plants can only successfully han- dle time-critical projects if the schedule is well coordinated and agreed in close collaboration with the pump supplier.
KRAL is continually proving to be a highly efficient, flexible and reliable partner. When there are special requirements, KRAL devel- ops customized special solutions together with the customer.
Water and air cause blisters in the end product. Espe- cially with transparent systems, this is immedi- ately obvious and can lead to complaints.
To prevent air being drawn into the PUR processing machine, the machine is set up in a vacuum. KRAL screw pumps are self- priming. Even under these conditions, they have no trouble working at about -0,5 bar. However, a me- chanical seal is not vacuum tight. Air can be drawn in through the unsuitable seal.
The magnetic coupling also provides the remedy here. The sealing element of the magnetic coupling is the containment can. The containment can pro- vides a totally hermetic seal against the vacuum.
Each mechanical seal has a stationary and a rotating sealing face. The sealing faces are lubricated by the pump medium. The liquid is in contact with air at the sealing faces. This can cause problems.
Isocyanate reacts with water and forms urea. The abrasive urea crystals dam- age the surfaces of the mechanical seal, resulting in leakage. The crystals also prevent the axial displace- ment of the sliding ring and damage the O-ring. This also results in leakage. De- pending on the isocyanate, the mechanical seal may have to be replaced several times a year.
As the magnetic coupling is hermetically tight, the polyol and the isocyanate do not come in contact with the outside air.
If the polyol or the isocy- anate can collect some- where in the pump, they may set, which would limit pump functionality.
KRAL screw pumps with magnetic coupling are de- signed in such a way that there are no dead spaces. Liquids cannot stay in one place for a long time. During filling and commis- sioning, the pump is auto- matically self-venting. This means that it can also operate in the vertical po- sition allowing for a more compact PUR processing machine design.
KRAL has a variety of solutions to offer to poly- mer producers, mechanical engineers and component producers:
Magnetically coupled pumps as transfer pumps for the raw materials of PUR.
Pumps with a mechan- ical seal for supplying the raw materials for the production machines from the polyurethane tank depot.
Magnetically coupled pumps and mechanical seal pumps for PUR production machines.
Unloading pumps. Statutory provisions prescribe that unloading must take place from the top. KRAL screw pumps can do this, because they are self-priming.