Problems troughs

Maintenance The only moving parts in spiral concentrators are those in the pumps that supply the feed and recirculate intermediate products. However, there are sometimes minor maintenance problems associated with the spiral trough itself. Some ores contain sharp particles of veiy abrasive minerals. The presence of these minerals in some ore causes rapid formation of deep grooves in the surface of cast-iron spirals. Wear grooves can be patched with a variety of plastic and metallic cements. Most spirals presently in service are made of cast iron with molded and vulcanized liners. These liners have successfully solved most wear problems. 

Since the lighter materials do not require stiff belts for tensile strength, there is usually no problem with troughing. 

The use of V-notches in a trough wall for overflow is more sensitive to leveling problems than the other designs, and for the same %- to Me-in. level tolerance produces a more severe non-uniform flow distribution. The quality of distribution from a V-notch is poor compared to the other types of trough distributor, but does have advantages in slurry systems [131]. It should not be used for critical distillation applications, but is good for heat transfer and where solids are in the system. 

Bypassing in a plate-type exchanger is less of a problem and more use is made of the flow separation which occurs over the plate troughs since the reattachment point on the plate gives rise to an area of very high heat transfer. 

A liquid is in steady state flow in an open trough of rectangular cross-section inclined at an angle f) to the horizontal. On what variables would you expect the mass flow per unit time to depend Obtain the dimensionless groups which are applicable to this problem. 

Prom the results presented in this chapter, it has been shown that the first step in the control problem of a CSTR should be the use of an appropriate mathematical model of the reactor. The analysis of the stability condition at the steady states is a previous consideration to obtain a linearised model for control purposes. The analysis of a CSTR linear model is carried out trough a scaling up reactor s volume in order to investigate the difference between the reactor and jacket equilibrium temperatures as the volume of the reactor changes from small to high value. 

The remaining problem of the molecular mechanisms of this action was judged to be related to the conformation of the dicarboxylic acid at the interface. This conformation is usually determined directly with the use of a Langmuir trough (16-18). The disadvantage of such a method for the present problem lies with the restrictions of the environment of the molecule to be Investigated. The basic requirement is that the molecule must be virtually insoluble in the liquid substrate on which the monolayer is supported. For the dicarboxylic acid in question, this meant a pH value as low as 2 and also a high electrolyte content in the aqueous substrate. 

Van Gelder I have a problem with the data you showed. There were genes with 30% peak to trough amplitude by RT-PCR. There is no way that you can distinguish less than a twofold change with any reliability on RT-PCR. 

The Problem A watering trough for cattle is a trapezoidal prism. The trapezoid has a bottom base of 2 feet and an opening, at the top, of 3 feet. The trough is 2 feet deep. If the trough contains 60 cubic feet of water, how long is it ... 

The difficulty in using either of these methods is that the monolayer tends to adhere to the sides of the trough and thus distorts under compression. This problem was indeed recognised by Blodgett [13] who suggested a solution to it, a solution which has been revived recently by Kumehara et al. [63]. In this method the film is confined at one end by a floating barrier which is attached to two waxed silk ribbons which intercept the water surface and form the sides of the enclosed area. These... 

It will be obvious that, when the substrate is much smaller than the trough and the surface viscosity is appreciable, there will exist a complicated flow pattern round the substrate which may cause difficulties. Various ingenious devices designed to overcome this problem have been... 

Simple plants capable of photosynthesis, many microscopic, and causing fouling problems in cooling towers, esp. mats (biomass) in distribution troughs and splash-fill areas. 

In this case the key problem is that financing might be very hard to obtain in trough times, which is the only time commodity chemical companies should consider adding capacity, in theory at least. Conversely, in an upturn, financing is available more easily and there might even be some pressure from capital markets to invest in new capacity - in fact preparing the overcapacity that will cause the next downturn (see also Chapter 6). 

---