Barrel length

Example 3. Hydrolysis in an Extruder.69 PET reactive extrusion experiments were carried out on a 25-mm Berstorff ZE25 corotating twin-screw extruder with a barrel length-to-screw ratio of 28 1. The extruder consisted of six barrel sections equipped for heating, cooling, and controlling the temperature of each section of the extruder. Initially reaction extrusion of PET and water was performed with cold water at room temperature injected into the extruder. Typical operating conditions were reaction temperatures of 230-265° C, extruder speeds... 

Compared with shotguns the higher pressure and shorter barrel length tend to cancel each other out and somewhat similar powders may be used. 

Initially it was thought that to achieve the required uniform conditions in the compound before the die area had been reached was simply a matter of extending the barrel length/diameter ratio (L/D) from 4 1 to 10 1 or 12 1. In fact this was not the case and later machines were extended to 15 1 or 20 1. 

The machines are generally short, with an enclosed barrel with an L/D ratio of around 6 1. This barrel length is normally sufficient to create enough pressure for the non-restrictive die heads that... 

The solids conveying device at Dow was built from a standard 63.5 mm diameter extruder. It was built by replacing the standard barrel with a short barrel, providing an L/D ratio of 4.5. The feed hopper casing had an effective barrel length of 1.9 diameters and was water cooled. The feed opening was 1.5 diameters in length ... 

The melt-fed extruder is typically designed with a relatively short barrel length of 6 to 1L/D. Since the resin is molten when it enters the extruder, the motor size is relatively small compared to a plasticating extruder with the same barrel diameter. The extruders are typically starve-fed. That is, the extruder is operating at a screw speed that is higher than required, and thus the rate is not controlled by the screw speed, instead, the rate of the overall process is controlled by the feedstock addition rate to the compounding machine. 

Barrel Diameter mm Barrel Length, L/D Rate, kg/h Motor Size, kW Specific Rate, kg/(hrpm)... 

Gun characteristics viz caliber or bore diameter, shot travel or barrel length, effective chamber capacity and ballistic efficiency of the gun (%). 

They were made in all calibers and all barrel lengths, and formed the basis of all the military models that were to follow. The Brit Army adopted the Webley-Pryse model in 0.442 inch (11.2mm) cal and called it the Webley Mark I. 

In 1899 the cal was changed to 0.455 inch (11.6mm) by which time the marks had reached IV, and this version continued in service until replaced by the 0.38 inch (9.7mm) in 1932, by when it was the Mark VI. The differences between the marks of military revolver were not great, but each one incorporated minor changes, particulary in the methods of manufacture. There were alterations in the barrel length and shape of the butt, and the Mark VI could be fitted with a shoulder stock... 

Although only a limited number of test firings and a single weapon were employed in this study, a much broader effort is currently in progress. The latter study will involve as varibles weapon caliber, barrel length, brand of ammunition, firing and sample collection conditions. Results of this will be reported subsequently. 

Richmond and Smith examined maize grits and showed extremely nonlinear increases of pressure and temperature along the barrel. Within the first two-thirds of the barrel length, the grits are hydrated, mixed and compacted, and pressures remain low. After compaction, pressures and temperature rise rapidly to 100°C and >40 psi and result in a transformation to a starch continuum with embedded granules whieh... 

Same as ARMET II with the addition of protection from 44 magnum fired from 6 -2" barreled S W revolver. (Apparently,th1s barrel length/ammo combo will penetrate ARMET II). 

The limited residence time available for reaction in an extruder is often a disadvantage. Although about 30 min is the maximum, less than 5-min residence time is usually observed in commercial extruders with realistic barrel lengths. Thus, the kinetics of the desired chemical reaction must be such that about 1-5 min would be the sufficient time for complete reaction, although when applicable, catalysis frequently shortens the time required for reaction. 

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