Unidirectional rooms

For unidirectional rooms the placement of inlet, source, and person is as important as when using exhaust hoods. For hospital isolation rooms, it is not only the inlet, outlet, and the person who influences the contaminant concentration the design of the room and the handling of the room s door are also important. 

Hot Pressing. Hot pressing may be used either to consoHdate a powder that has poor compactabiHty at room temperature, or to combine compaction and sintering in one operation. The technique is essentially the same as described for unidirectional die compacting. The powder is heated by either heating the entire die assembly in a furnace or by induction heating. In most instances, a protective atmosphere must be suppHed. 

One of the unidirectional flow system modifications is air supply through diffusers located above the occupietl zone. The supply air temperature is lower than the desired room air temperature in the occupied zone, and air velocity is lower compared to a mixing-type air supply, bur higher than for a thennal displacement ventilation. Polluted air of the occupied zone is suppressed by an tiverlying air cushion that displaces the contaminated air toward floor-level exhausts (Fig. ". 12). 

To create unidirectional air flow field over the room area by supply air... 

In general, the compressive strength of a non-reinforced plastic or a mat-based RP laminate is usually greater than its tensile strength. The compressive strength of a unidirectional fiber-reinforced plastic is usually slightly lower than its tensile strength. Room-temperature compressive stress-strain data obtained per ASTM for several plastics are shown in Table 2-5. 

The greatest risk of contamination of a pharmaceutical product comes from its immediate environment. Additional protection from particulate and microbial contamination is therefore essential in both the filling area of the clean room and in the aseptic unit. This can be provided by a protective work station supplied with a unidirectional flow of filtered sterile air. Such a facility is known as a laminar airflow unit in which the displacement of air is either horizontal (i.e. from back to front) or vertical (i.e. from top to bottom) with a minimum homogenous airflow rate of 0.45 ms" at the working position. Thus, airborne contamination is not added to the work space and any generated by manipulations within that area is swept away by the laminar air currents. 

Experimental results are presented that show that high doses of electron radiation combined with thermal cycling can significantly change the mechanical and physical properties of graphite fiber-reinforced polymer-matrix composites. Polymeric materials examined have included 121 °C and 177°C cure epoxies, polyimide, amorphous thermoplastic, and semicrystalline thermoplastics. Composite panels fabricated and tested included four-ply unidirectional, four-ply [0,90, 90,0] and eight-ply quasi-isotropic [0/ 45/90]s. Test specimens with fiber orientations of [10] and [45] were cut from the unidirectional panels to determine shear properties. Mechanical and physical property tests were conducted at cold (-157°C), room (24°C) and elevated (121°C) temperatures. 

Figure 3.1. Diagrammatic illustration of the flow pattern of HEPA-filtered air through a t5 pical clean room. Air is pumped into the room through HEPA filters (see text) located in the ceiling, and exits via extract units, normally located at floor level. Although the air flow is non-unidirectional (i.e. not true laminar flow), it generates a constant downward sweeping motion, which helps remove air-borne particulate matter from the room...

The sterility testing area is located in an area of the microbiology laboratory. The area contains a gowning room and sterility testing room. Each testing room contains a unidirectional flow HEPA hood. 

Perform air velocity check in unidirectional area and nonunidirec-tional area in the following rooms per plant SOP. 

One can conclude that the presence of crystallites prevents the amorphous chains from deforming exclusively due to rotational rearrangements and the deformation is accompanied by volume changes. For undrawn PE and PP with degrees of crystallinity of 60-70%, the Poisson s ratio is approximately 0.35 at room temperature. This value is typical for solids and it corresponds to the increase of the volume during unidirectional stretching. 

A is the area of the clean room of clean air controlled space in m2. In the case of unidirectional perpendicular airflow, the area A may be considered as the cross section of air horizontal to the airflow. 

Careful attention must be given to material flow patterns for clean and dirty equipment to prevent cross contamination. In larger facilities, the equipment wash room may be a separate room proximate to the preparations area with defined flows for materials and personnel. Ideally, materials should move through the facility in a unidirectional fashion, with no cross over of any kind. 

FIGURE 14 Non-unidirectional clean-room with lay-in HEPA filter modules. 

FIGURE 17 Non-unidirectional clean-room with air handler mounted HEPA filters. 

FIGURE 18 Non-unidirectional clean-room with critical area unidirectional flow plenum. 

Fig. 6.5 Cyclic stress-strain behavior observed during the room temperature fatigue of unidirectional SiQ/LAS-II at a maximum stress below the 105 fatigue limit (loading frequency = 10 Hz, crmin/crmax = 0.1). The cyclic stress-strain curves show very limited, if any, hysteresis. Note that the strength and strain capability is retained after cyclic loading below the proportional limit stress. After Prewo.42...

Zawada et al.44 showed that the proportional limit, expressed in strain (0.3%) rather than in stress, was identical for unidirectional and cross-ply laminates of SiCf/1723. Moreover, the fatigue limit of the unidirectional composite, expressed in strain, corresponded well with the measured fatigue strain limit of the cross-ply laminates. This indicates that the fatigue limit of a cross-ply laminate is primarily governed by the 0° plies and that the influence of the 90° plies is minimal (this result is expected to hold only for room temperature fatigue—see Chapter 5 for a discussion of how transverse plies influence cyclic creep behavior). The 90° plies develop transverse cracks early... 

Fig. 6.7 Fatigue life diagram for the tension-tension fatigue of unidirectional SiQ/1723 at room temperature (10 Hz, VmJ max — 0.1). The 106 cycle fatigue limit of 440 MPa is higher than cr. and

Allen and Bowen40 studied the fatigue behaivor of unidirectional Nicalon SiCf/CAS at room temperature by flexural testing at 10 Hz for / -ratios of 0.1 and 0.5. It was found that the specimens tested at R = 0.1 all failed above a certain stress level. For the specimens fatigued at ft = 0.5 there was considerable scatter in the fatigue lifetime. While some specimens failed lifetimes similar to the specimens with R = 0.1, roughly half the specimens did... 

Additional factors which must be taken into account are environmental effects (thermal as well as chemical), effects of defects, statistical variability of the material, long-term behavior, and cyclic versus static loading effects. Assessment of these effects requires the end user to conduct a large series of tests using multiple specimens. A typical series will examine a unidirectional material in tension in the 0, 90, and cross-ply directions 0, 90, and cross-ply in compression and 1-2, 1-3, and 2-3 shear at different temperatures ranging from —54°C to the expected service temperature creep rupture at temperatures up to the expected service temperature and fatigue at room and elevated temperature. This series of tests, shown in Table 12.1, may require over 400 specimens. 

Figure 3. Effect of specimen size on absorbed energy of unidirectional cloth specimen notched flatwise at room temperature...

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