Seals operating range

The following pictures show different arrangements of Environmental Controls. These Controls expand the operational range of the mechanical seal, improving the pump service life. 

Turboexpanders eurrently in operation range in size from about 1 hp to above 10,000 hp. In the small sizes, the problems are miniaturization, Reynolds Number effeets, heat transfer, seal, and meehanieal problems, and often inelude bearing and eritieal speed eoneerns. In intermediate sizes, these problems beeome less signifieant, but bearing rubbing speeds and vibration beeome inereasingly important. 

To obtain satisfactory seal performance, the shaft stiffness shall limit the total deflection imder the most severe dynamic conditions over the allowable operating range of the pump—with maximum diameter impeller(s) and the specified speed and fluid—to 50 pm (0.002 in.) at the primary seal faces. This shaft deflection limit may be achieved... 

While a MSssbauer effect cell with an operating range from 77 to 800 K is routinely used in catalytic studies, temperatures lower than 77 K may not be as commonly encountered. In this case, it may be advantageous to pretreat the sample and then seal it between y-ray transparent disks (e.g., Mylar) in... 

Stable operating range). Some flexibility will always be required in an operating plant to allow for changes in production rate, and to cover start-up and shut-down conditions. The ratio of the highest to the lowest flow rates is often referred to as the turn-down ratio. Bubble-cap plates have a positive liquid seal and can therefore operate efficiently at very low vapour rates. 

Figure 2. (Top) Detail of the MULVFS pump unit and filter-holder assembly. The filter holder consists of three stages. The upper two plates are baffles necessary to prevent particles from being redistributed on the filters during recovery. The next plate supports the 53-gm mesh Nitex prefilter, and the bottom plate supports the pair of 1-pm micro quartz-fiber filters and seals to the pump intake. (Bottom) Pressure vs. flow rate curves for the MULVFS and LVFS pump units. Horizontal bars indicate operating ranges of the two systems during filtration.

The division of the sample on to two identical columns can be realized easily and carried out very reliably, but different retention times need to be considered due to the vacuum impact on the MS side. Since the capacities of the two columns are additive, the quantity of sample injected can be adjusted in order to make use of the operating range of the mass spectrometer. Two standard columns can be installed for most injectors without further adaptation being necessary. In the simplest case, the connection can be made using ferrules with two holes in them. It must be ensured that there is a good seal. A better connection involves an adaptor piece with a separate screw-in joint for each column. With this construction the independent positioning of the columns in the injector is possible. Suitable adaptors can be obtained for all common injectors. 

---