Blow air pressure

Incomplete blow Extrusion rate too high Blow-up air pressure Blow-up time too short Parison is cut at pinch-off Reduce screw speed Increase blow air pressure Reduce mold closing speed... 

Poor detail definition Blow air pressure too low Poor mold venting Cold mold Increase blow air pressure and blow time Improve venting Increase mold temperature... 

Mold shrinkage is dependent on many factors, such as resin density, stock temperature, mold temperature, part thickness, and blowing air pressure. Typical polyethylene blow molding shrinkage is as follows ... 

Blow air pressure has an effect on the quality of the container. PET should be blown with a minimum of 300 psi. Due to container design it may be necessary to use 550-600 psi blow air. The air must be oil free. 

Inspection of electrical wiring if there is any (such as for space heaters, cold or hot air blowing, enclosure pressurizing or any other protective circuit)... 

Blowing air through the hot, crude, liquid metal oxidizes traces of metals such as Fe, Cu, Zn and Pb which form an easily removable scum. Further purification is by distillation under reduced pressure. About 4000 tonnes of mercury are used annually but only half is from primary, mine production the other half being secondary production and sales from stockpiles. The main primary producer is now Spain, but several other countries, including the former Soviet Union, China and Algeria, have capacity for production. 

In coastal areas, temperature differences between the land and the water produce air pressure variations, creating sea and lake breezes that are superimposed on the normal winds. These winds vai"y diurnally and as a function of cloudiness. During the daytime, winds blow from the cool sea toward the warm land, while at night the land becomes cooler than the sea surface, and the winds blow from land to sea. 

An alternative method of protection is the use of a smaller relief valve in conjunction with an automatic isolating valve, which shuts off the air supply to the equipment if the pressure rises more than 20 per cent above the blow-off pressure of the relief valve. If this method is used it is essential to ensure that sudden cessation of air supply to the equipment cannot cause a hazard. 

There are two points of the cycle at which velocity decreases very rapidly from a high value to zero. To give a.familiar analogy, the van der Pol oscillator for this value of y. behaves not as a decent oscillator but rather as a pneumatic hammer, which idles for some time while the air pressure builds up, delivers a hammer blow, losing its kinetic energy, and then begins a similar half-cycle. 

Figure 18.11 contains a sketch of an extrusion blow-molding scheme. Here a heat-softened hollow plastic tube, or parison, is forced against the walls of the mold by air pressure. The sequence of material introduction into the mold and subsequent rejection of the material from the mold is generally rapid and automated. Approximately 1 million tons of thermoplastics are produced by this technique annually. 

Taking as constant the air pressure blowing the sand, the grain-size and volume of sand, and also the registered depths of indentation and the radius of curvature of the bottom, we proceeded to determine the new value of Mackensen s abrasiveness, being the corrected indentation depth. The true volume of the hole was checked for depth measurement h < 3 mm,... 

Most LLDPE produced worldwide is made into thin film, either melt blown or cast from the melt. Blown film is produced by extrusion of LLDPE melt through a circular die with a large diameter, up to 100-120 cm. and a narrow gap, usually less than 1 mm. The tube of molten polymer expands from internal air pressure and forms a bubble of a larger diameter, Typically, the blow-up ratio, the ratio of the final film tube diameter to the circular-die diameter, is between 1.5 1 and 4 1. LLDPE cast film is manufactured by depositing potymer melt on a rotating heated... 

---