Spinning Pumps

The capacity of spinning pumps is indicated by their volume per revolution, usually in cm values of 0.5-50 cm are common. They are operated at 10-50 rpm. For example, for a low yarn titer the required volume flow could be 50 cm min , which would be delivered by a 2 cm spinning pump running at 25 rpm or a heavy industrial yarn titer could require a 20 cm pump at 30-40 rpm. Note that volume flows are adjusted while mass flows are prescribed. A recalculation is easy when the density of the melt is known, but in practice a mass flow check is always made. 

Melt-spinning pumps can be constmcted from normal steel. Tolerances are not too critical when melt viscosities are sufficiently high. Pumps are cleaned in hot ovens at 500°C. 

---

Spinning basket reactor, 21 352, 353 Spinning-cup atomizers, 23 659 Spinning-cup sulfur burner, 23 660 Spinning machines, 19 749 Spinning processes, hollow-fiber, 16 7-12 Spinning pump, for olefin fiber extrusion, 11 231... 

The war ended, but the flywheels kept spinning, pumping out ammonia for democrats and Nazis alike. The Leuna Works grew... 

There are two principal mechanisms by which INDOR responses can be induced, and, although it is never possible for the operator to be sure that either is exclusively responsible for the response, it is possible so to conduct experiments that one or other is of predominant importance. The sole difference between them involves the power level of the irradiating field at medium power-levels, the so-called spin-tickling mechanism is of predominant importance, whereas at, somewhat lower power-levels, the spin-pumping mechanism is considered to be responsible for the induction of responses. The decision as to which of these two sets of conditions is to be used in a particular experiment is predicated by the following considerations. The effective signal-to-noise ratio of the INDOR... 

Fig. 6.—Diagrammatic Representation of the Spin-pumping Mechanism for an INDOR Experiment. [Throughout, the observing radiofrequency is centered on the X-2 transition. The upper part depicts the irradiation of the A-1 transition, and the lower, that of A-2. The connectivity relationship for the energy levels corresponding to these transitions is given in the center it is clear that transition X-2 has an energy level in common with both the A-1 and the A-2 transitions.]...

It is clear from the preceding discussion that an INDOR spectrum determined by use of power levels that correspond to the spin-pumping mechanism will consist of a series of positive- and negative-going responses. However, regardless of whether the INDOR responses are positive- or negative-going, their frequency corresponds precisely to that of the normal transitions that are spin-coupled to the chosen monitor-point. 

The spin pump (metering pump) delivers the molten polymer to a spin pack, which consists of a top cap and a breaker plate to distribute polymer evenly, then into a filtration media and out of the spinneret. The filtration media contains either different layers of special sand, layers of different size of stainless steel screens, or sintered metals. In addition to removing the foreign particles, gel particles and undesirable conglomerate additives, filtration may also improve the polymer melt homogeneity due to its torturous path and high shear of the filtration media. 

In melt spinning, thermoplastic polymers (i.e. polymers which soften and melt when heated) such as polyamide or polyethylene terephthalate are made molten or liquefied in an extruder and are forced through the spinneret by a spinning pump. The filaments are then soUdilied by air-cooling. 

Figure 38-3. Spinning processes (schematic). (I) Melt spinning, (II) dry spinning, (111) wet spinning P, spin pump A, precipitation bath B, drawing bath.

Courtaulds introduced, specifically for the manufacture of carbon fiber, a Special Acrylic Fiber (SAF), which was made at the Coventry works using the same dope, but spun on production lines with additional filtration and individual dope spinning pumps, enabling precise d tex control for smaller tows. Courtaulds ceased production of their Special Acrylic precursor (SAF) in 1991. 

Cangle filter n. A small filter interposed between the spinning pump and spinning jet to effect final filtration of the spinning solution prior to extrusion. 

Similar measurements were carried out in 0-benzophenone. The authors mention that in general only a few percent of the total intensity is emitted through the vibrationless 0, 0-transition because of coupling of intramolecular vibrational modes to the electronic transition. TTierefore, the nuclear spin pumping rate is very small. 

Melt filtration/melt pipe to the spin pump(s)/spin pump(s) to maintain a constant throughput to the spinneret(s)... 

Note that the mass flow is constant in the process, from spinning pump to winder. No mass is lost, in contrast to dry or wet spinning. For example, at the end of the spin-line the speed is 800 m min , flve times lower than after drawing, but the undrawn yarn still has a flve times higher titer. Also note that the volume flow is not completely constant, because the density increases (by about 20%) when the melt cools down, solidifies, and crystallizes. 

Most textile filament yarns are also direct-spun. The output per bundle is small, and therefore hundreds of spinning positions must be fed from one polymerization unit, making the polymer melt-line system very complicated. Winders make four, six, eight, or even 12 packages simultaneously, and spinnerets and spinning pumps are clustered accordingly. 

---