Nozzle leakage

The split apparent in Fig. 11.9 was located along the top of the tube facing the steam inlet nozzle. This is one of several tubes in this area having similar longitudinal splits. Leakage of river water from these tubes resulted in feedwater contamination, which turned out to be a major factor in tube failures in the boiler. 

The temperature is approximately 20°F below the 265°F temperature limit. The sections differ by less than 1 F. This is probably just luck because that good a balance is not really necessary. Also, it should be noted that to maintain simplicity the additional factors were ignored, such as the 10°F temperature pickup in the return stream due to internal wall heat transfer. Also, nozzle pressure drops for the exit and return were not used. Balance piston leakage was not used as it was in Example 5-3. When all the factors are used, the pressures for each section would undoubtedly need additional adjustment as would the efficiency. However, for the actual compression process, the values are quite realistic, and for doing an estimate, this simpler approach may be quite adequate,... 

There are several types of nozzle. The simplest is an open nozzle as shown in Fig. 4.34(a). This is used whenever possible because pressure drops can be minimised and there are no hold up points where the melt can stagnate and decompose. However, if the melt viscosity is low then leakage will occur from this type of nozzle particularly if the barrel/nozzle assembly retracts from the mould each cycle. The solution is to use a shut-off nozzle of which there are many types. Fig. 4.34(b) shows a nozzle which is shut off by external means. Fig. 4.34(c) shows a nozzle with a spring loaded needle valve which opens when the melt pressure exceeds a certain value or alternatively when the nozzle is pressed up against the mould. Most of the shut-off nozzles have the disadvantage that they restrict the flow of the material and provide undersirable stagnation sites. For this reason they should not be used with heat sensitive materials such as PVC. 

The absolute, barometric pressure is not normally required in ventilation measurements. The air density determination is based on barometric pressure, but other applications are sufficiently rare. On the other hand, the measurement of pressure difference is a frequent requirement, as so many other quantities are based on pressure difference. In mass flow or volume flow measurement using orifice, nozzle, and venturi, the measured quantity is the pressure difference. Also, velocity measurement with the Pitot-static tube is basically a pressure difference measurement. Other applications for pressure difference measurement are the determination of the performance of fans and air and gas supply and e. -haust devices, the measurement of ductwork tightness or building envelope leakage rate, as well as different types of ventilation control applications. 

Smoke generator A device that electri cally heats oil-producing smoke. The smoke is liberated from a nozzle by either thermal forces or by means of a fan and used to observe airflow patterns within a space or to observe leakage from ductwork, etc. 

The use of multinozzle injection machines. In general, this type of machine has a horizontal reciprocating screw that feeds four injection nozzles each connected to a single cavity mold thus minimizing waste. However, one concern with this approach is the need to have the mold accurately lined up (the top and bottom surfaces of the mold will be in the vertical plane) to eliminate compound leakage at the nozzle/mold interface. 

Examination for obvious physical damage, corrosion, leakage, or clogged nozzle... 

DLeakage - The only place liquid should come out is the nozzle. You can sea) up the loading port after filling, but any other leakage is totally unacceptable. 

Another occurrence is the leakage of product through the roof drains on external floating-roof tanks and out at the roof drain discharge nozzle. These spills are sometimes caused by equipment failures but also result from operator error or lack of training. Because it is easier to leave secondary-containment valves and roof drain valves open so that they do not need to be opened in periods of rainfall, the effectiveness of this equipment is reduced. This may be classified as operator error. A comprehensive tank management program addresses these kinds of problems. 

The reason illustrates the true nature of the shell-and-tube heat exchanger. It is a compromise between an ideal heat-transfer configuration and practical mechanical limitations. In this case, the difficulty is preventing leakage around the longitudinal baffle. Such leaks permit the shell-side fluid to short-circuit the tube bundle that is, a percentage of the inlet flow, may flow directly to the outlet nozzle. In extremely serious cases, I have seen the bell head (shown in Fig. 19.8) 100°F colder than the shell-side outlet temperature. 

The inside of the nozzle must have a very smooth finish. This improves the flow through the nozzle and prevents particles from getting trapped in some cavities. In such events, the particles would be ejected during opening of the valve and could be trapped between the nozzle and the disc, causing leakage. 

Especially on sulphur recovery units and heavy crude oil service, there could be excessive seat leakage of 316 SST trims caused by sulphide corrosion/pitting. In this case retrofit the valve with, for instance, an Inconel 718 nozzle and disc insert (with high nickel content). In any case, make sure that a proper material selection for the service is used. 

G) The bonnet shown here confines the tube-side fluid exiting from the first-pass tubes and turns it around into the second-pass tubes. The bonnet and the channel are basically interchangeable—a channel (with no pass divider) could have been used here instead of the bonnet, or a bonnet with welded-on nozzles could have been used instead of the channel at the inlet/exit end. The channel/channel cover combination is more expensive and more prone to leakage, but allows tube inspection, etc., without disturbing the piping connections. 

Nozzles, flanges and valves. These components must be free of signs of corrosion and leakage. All flange bolts should be installed and be of the correct diameter and length. 

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