Reduced torques

FIGURE 12.10 Reduced torque versus strain following flow reversal for hard sphere suspension of various concentrations. Polystyrene spheres 45 pm in diameter in silicone oil. Taken from Gadala-Maria and Acrivos [34]. 

At six minutes the polymer flux had essentially regained the selected mastication temperature, 200°C, but notice that during this interval mastication reduced torque precipitously to the low level of 320 meter-grams. After a total mastication time of 10 minutes the polymer melt torque level fell a bit further to 250 meter-grams and declined little more during the full 20 minute term of the experiment. 

For calculation of the segments a FEA-analysis was conducted. For the loads a axial pressure of Ap=80 bar and a torque gradient of AMt =130 Nm per segment was assumed. These values should be lower in reality, because of the supporting effect of the suction side (the pressure difference is getting smaller) and the reduced torque caused by ceramic segments. Values of the real process were not well known at this point, so the calculations are showing a worst case scenario. 

Internal melt lubrication Metal stearates fatty amides, ester, acids, or alcohols polymeric agents Increased output Reduced melt viscosity and temperature Process energy savings and reduced torque Improved mold-filling Part-surface contamination possible (and reduced printability) Lower physical properties (or higher, depending on the processing aid)... 

Twin screw extruders producing profiles will often use starve feeders to reduce torque requirements. However, a better approach, when feasible, is... 

In addition to fusion, standard specifies several additional useful procedures such as thermal stability test (time from maximum torque due to fusion to the sudden torque increase caused by the thermal degradation), color-hold stability test (time to equivalent color change), and shear stability test (the data are plotted as torque vs. rpm and sensitivity is determined from the peak value as the highest rpm which does not reduce torque). ... 

Several materials were blended with PVC and properties of blends were compared with effect of plasticization by DOP. These included nitrile rubber, NBR, poly(ethylene-co-vinyl acetate), EVA, and poly(ethylene-co-vutyl aciylate-aciylate), Ac. Increase in plasticizer concentration (DOP) normally reduces torque and final melt temperature of blend but this is not the case when NBR replaces plasticizer. EVA behaves in a similar... 

Figure 2.22 When an otherwise free-running nut is tightened down, part of the tension induced in the bolt shank is lost due to the crushing of the high-spots on the engaged threads. Thus, on removal, a reduced torque is required. This is approximately 90 per cent of the application torque and is lost over 60° of rotation at the most.

Most extruded materials are fairly low in lipid content due to several problems inherent to extrusion. Lipid content greater than 5-6% affects extruder performance by reducing torque and subsequently, product expansion. Lipids literally grease the internal parts of the extruder, increasing slippage. Extrusion can enhance yields of oil from oilseeds by cooking and disrupting cell walls. 

Assessment of the plasticizer to improve processability (lowering processing temperature or reducing torque). 

The processing aid polymer can significantly enhance product quality and processability, not only by eliminating surface defects, but also by reducing torque and power requirements as well as die plate pressure [26,33]. 

As the harder stocks are generally more scorchy , because they increase in temperature more rapidly when being mixed, lower speeds are used. To get increased torque at lower speeds very often a DC motor which is slant rated using field weakening is specified. What this means is that it is possible to specify a DC electric motor so that it develops its full horsepower at 80% full speed as well as at full speed, e.g. 100 hp at 1200 rpm and 100 hp at 1500 rpm. This means that the torque up to 1200 rpm is constant, and it is reduced between 1200 and 1500 rpm. The slant rated or field weakened specification is ideal for a mixer drive, so as to have high torque at low speeds and reduced torque at high speeds. 

Maehs, J., Renne, S., Logan, B. Diaz, N. 2010. Proven Methods and Techniques to Reduce Torque and Drag in the Pre-Planning and Drilling Execution of Oil and Gas Wells. Paper SPE 128329 paesented at the I ADC/ SPE Drilling Conference and Exhibition, New Orleans, Louisiana, 2-A February. 

Effect of secondary flow (Taylor vortices) on reduced torque in a Couette viscometer. From Denn and Roisum (1969). Note that A and B are constants. 

Reduced torque versus time after steady shear of a 1 Pa s Newtonian oil at 10s" with a 25 mm diameter, 0.1 rad cone, (a) Strong spring response of a torsion bar transducer with a spring constant, AT = 10 N ln/rad and 250 rad/s resonant frequency, simulated using eq. 8.2.1. (b) Force rebalance transducer with resonant frequency of 960 rad/s. From Mackay et al. (1992). 

Lubricants and plate finishes on fasteners can help reduce torque required and improve corrosion resistance. 

Ionic Nature Anionic/nonlonic Uses Detergent for mud drilling emulsifier for oil penetrant Features Aids penetration by reducing torque and minimizing bit-balling Properties Liq. 

---