Plug-type

Self-contained, independent engine-driven plug-type units used in tmck and tmck/trailers range in capacity from 6 to 12 kW to maintain trailer temperatures of 20°C in 38°C ambients. At trailer temperatures of — 18°C in 38°C ambients, capacities range from 2—6 kW. 

Dezincification Dezincification is corrosion of a brass alloy containing zinc in which the principal product of corrosion is metallic copper. This may occur as plugs rilling pits (plug type) or as continuous layers surrounding an unattacked core of brass (general type). The mechanism may involve overall corrosion of the alloy followed by redeposition of the copper from the corrosion products or selective corrosion of zinc or a high-zinc phase to leave copper residue. This form of corrosion is commonly encountered in brasses that contain more than 15 percent zinc and can be either eliminated or reduced by the addition ox small amounts of arsenic, antimony, or ph osphorus to the alloy. 

Figure 13.5 Plug-type dezincification on the internal surface of a brass condenser tube. Note the extreme porosity of the copper plugs. Tube wall thickness was 0.040 in. (0.10 cm). Compare to Fig. 13.13. (Courtesy of National Association of Corrosion Engineers, Corrosion 89 Paper No. 197 by H. M. Herro.)...

Figure 13.8 A brass tube showing plug-type dezincification. The white patch above the plug on the external surface was caused by dissolved solids, concentrated by evaporation of water leaking through the porous dezincified plug.

Figure 13.9 Stratified copper corrosion product in plug-type dezincification. Denickelification...

Because wastage is usually slight, identification by visual observation alone is difficult microscopic examination is usually required. Layer-type dealloying commonly occurs. Plug-type denickelification attack has never been observed at this laboratory. Surfaces have a reddish color due to the accumulation of denickelified metal. 

Figure 13.10 A hole emanating from the internal surface of a brass condenser tube. The hole was caused by plug-type dezincification (see Fig. 13.11).

Figure 13.10S A transverse cross section through the tube wall in Fig. 13.10A. Note the through-wall plug-type dezincification.

Two sections of utility condenser tubing were received. One of the sections had deep plug-type dezincification on internal surfaces (Fig. 13.5) the other showed only superficial corrosion on internal surfaces (Fig. 13.13). 

Figure 3-23. Plug type unloader. (Courfesy of Dresser-Rand)...

For the twin arrangements, a two-way, six-ported, continuous-flow valve will be required. If it is a tapered plug type, a means of lifting the plug will be required. The purpose of the tapered plug valve is to provide... 

Unbalance, response programs, 372 Uninterruptable power supply (UPS), 311 Universal gas constant, 16 University of Virginia, 389 Unloader plug type, 81 plunger type, 81 port type, 81 valve, 81... 

Inlet valve unloaders are used to deactivate a cylinder end and reduce its capacity to zero. Two of the more common types of unloaders are depressor-type unloaders and plug-type unloaders. Depressor-type unloaders hold the inlet valve open during both the suction and discharge... 

Wedge Disc, Double Disc, or Plug Type... 

In certain alloys and under certain environmental conditions selective removal of one metal (the most electrochemically active) can occur resulting in either localised attack, with the consequent possibility of perforation (plug type), or in a more uniform attack (layer type) that results in a weakening of the strength of the component. Although the selective removal of metals such as Al, Fe, Co, Ni and Cr from their alloys is known, the most prevalent form of de-alloying is the selective removal of zinc from the brasses —a phenomenon that is known as dezincification. 

Fig. 1.60 Dezincification and impingement attack of copper-altoy tubes, (a) Uniform layer dezincification of a brass, (b) banded dezincification of a brass, (e) plug-type dezincification and...

Dezincification is readily apparent, since the yellow colour of the brass is replaced by the characteristic red of copper, which may take the form of small plugs or of layers that in some cases can extend over the whole of the surface (Fig. 1.60). In plug-type dezincification a mechanically weak, porous residue of copper is produced, which may remain in situ or become removed by the pressure of water, leading to a perforation. In the layer type the transformation of the alloy into a mechanically weak layer of copper results in loss of strength, and failure may occur by splitting when the metal is subjected to water pressure or to external stress. 

With a single-phase brass the whole of the metal in the corroded areas is affected. Dezincification may proceed fairly uniformly over the surface, and this layer type takes much longer to cause perforation than the localised plug type that more often occurs . With a two-phase brass the zinc-rich 8 phase is preferentially attacked as shown in Fig. 4.12. Eventually the a phase may be attacked as well. The zinc corrosion products that accompany dezincification may be swept away, or in some conditions may form voluminous deposits on the surface which may lead to blockages, e.g. in fittings. 

Regular washer-type faucets are hard to control for low water flow, such as required by condensers. For these purposes, needle valves are recommended. They give excellent control, and flow rate does not change as long as the pressure remains constant. The inexpensive plug-type valves are rarely adequate for laboratory water service. 

Inexpensive plug-type valves may be use for hook-ups to appliances that have their own gas flow adjustment. For those that do not, needle valves are recommended for precise control. 

The precise and, where needed, short setting of the residence time allows one to process oxidations at the kinetic limits. The residence time distributions are identical within various parallel micro channels in an array, at least in an ideal case. A further aspect relates to the flow profile within one micro channel. So far, work has only been aimed at the interplay between axial and radial dispersion and its consequences on the flow profile, i.e. changing from parabolic to more plug type. This effect waits to be further exploited. 

We have manufactured the graphite electrodes of plug type. An active mass (88wt% graphite, 10wt% carbon black and 2wt% PTFE) was pressed into a polyethylene plug of 11 mm inside diameter. We have studied... 

The other end of the capillary tube carries a plug type connector which allows the crucible holder to be rapidly removed and replaced. The connector is adjustable with a centering device. 

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