SchuF’s polymer valves were originally designed together with polymer industry pioneers in the early stages of polymer development.
SchuF has developed a great variety of original polymer valves.
The first diverter, multiport and in-line sampling valves came from SchuF as well as the first flush bottom valve and lift plug valve. Additive injection for PET, steam injection, stripper and killer valves for PVC and PP were all developed in SchuF offices.
One of the most commonly used speciality polymers is Polyester. It has taken an ever greater part of the fibre market from the cheaper more basic Nylon, in applications like shirts etc. New applications include Tyre cord for radials, car parts, POY, PET for reusable bottles and film polyester etc.
Process Challenges (Polyester)
Polyester is a polymerized ester. The ester is made in a two stage low pressure application called the Esterification process. DMT (old) or PTA (meanwhile much more common) and Ethylene glycol are the feed stock.
The ester is polymerised in a 3 stage process involving a first and second polymeriser and a finisher. The process takes place under a very low vacuum 10-3 mbar at 270°C. The quality of the product depends, to an extreme degree, on holding the vacuum conditions.
Finishing to spinning
The polymer is now ready, but of course, it must be cleaned, possibly whitened, and split into many lines to reach the chippers or spinning blocks. Here the main challenge to quality is residence time in absolute and relative terms i.e. the total time spent in the pipes and the varying times between the layers of product due to slow spaces and wall adhesion.
Valve Range for Polymer Service
The primary use of SchuF valves is in the control of the feeding of the reactors (Special Angle Control Valves), as well as draining the reactors and vessels, (Ram and Disc Bottom Outlet Valves), as are some pipe Sampling and Feed Valves, Y-Globe, Diverter or Angle Shut-off Valves.
Filters can be switched using diverter, changeover valve or lift plug valves. Each have their own unique advantages and the choice should be made between the customer and SchuF to ensure the optimal choice. Where extruders are in use lift plug or changeover valves can also be used as dump valves.
Features of SchuF polymer valves
SchuF’s strengths are its flexibility of design and construction, its unrivaled experience with the media and the way all its valves can handle vacuum, high pressures and temperatures as well as very high viscosities, while eliminating “dead” and “slow” spaces, avoiding impurities and reducing residence times.
SchuF offers cast valves to optimise polymer flow and forged or welded constructions where material integrity is of maximum importance. In all cases the flow path is optimised by the contour of the valve’s body and moving parts. SchuF can provide valves with and without replaceable seats depending on start-up conditions. SchuF offers the best high pressure sealing by a judicious combination of different grades of stellite and a specially angled seat to achieve a tangential “zero force” seal.
For vacuum tightness, special aluminum grade sealing rings offer leak tightness under 10-6 torr.l.sec-1 and a Helium vacuum test to prove it. We can offer you performance and seat testing under low or high temperatures, and high pressure or vacuum, with Helium, Nitrogen or water … whatever is required.