Surface Cleaning Procedure

Once machined, all the copper and teflon pieces will undergo a surface cleaning procedure that will guarantee the required low level of surface radioactive contamination for those parts that directly face the detectors. 

A final point to remember is that after the proper (i.e., the one fitting the conditions and requirements of a given surface) cleaning procedure has been completed, care must be taken to ensure that the surface will not be recontaminated during subsequent storage. 

Cleaning of product contact surfaces (cleaning procedure/sampling plan/analytical method) limits practical, achievable, and verifiable. 

G. Gould and E. A. Irene, The influence of silicon surface cleaning procedures on silicon oxidation, J. Electrochem. Soc. 134, 1031, 1987. 

Another explanation for the initial period of no wear is that the polyimide and ball surfaces were contaminated by a film. This film caused low friction and surface stresses below that required for immediate wear particle generation. The initial period is the time during which the film is worn away resulting in an increase in adhesion, increase in surface stress, and subsequent wear particle formation. Obviously, both fatigue and contaminant film removal could be operative during the initiation period. Experiments with carefully controlled environments and surface cleaning procedures would be necessary to discriminate between these two explanations. 

However, extensive potential cycling, which is a widely used in electrode-surface cleaning procedure, sinters the nanoscale electrocatalyst. Although the sample in Fig. 4(c) started with the same as-received electrocatalyst as that shown in Fig. 4(b), the dispersion estimated from the corresponding Pt NMR spectrum is only about 27% [30], far lower than the 50% obtained from Fig. 4(b). This dispersion... 

Ip et al. [30] could obtain a minimum specific contact resistance of 6 x 10 Q cm for Ti/Al/Pt/Au contacts on undoped (n = 10 cm ) bulk ZnO. The contacts did not show ohmic behavior in the as-deposited state and reached their minimum resistance after 250 °C annealing. This value was essentially independent of the surface cleaning procedure employed, including sequential solvent cleaning or H2 plasma... 

A particularly insidious failure mechanism that is commonly found in carbon-steel tubing is under-deposit corrosion. In many cases, corrosion products fomi a scab that can mask the presence of the pitting, making it difficult to quantitatively assess using conventional NDT methods. However, by combining proper cleaning procedures with laser-based inspection methods, the internal surface of the tubing can be accurately characterized and the presence of under-deposit corrosion can be confirmed and quantified. 

Thermoplastics. There are five elastomeric membranes that are thermoplastic. Two materials, chlorinated polyethylene (CPE) and polyisobutylene (PIB), are relatively obscure. Thermoplastic materials can be either heat-fused or solvent-welded. In contrast to Hypalon and uncured EPDM, this abiHty to fuse the membranes together remains throughout the life of the material. However, cleaning of the membrane surface after exposure to weather is required. Correct cleaning procedures for specific membranes are available from the individual manufacturer. 

Sanitization is a cleaning procedure that reduces microbial contaminants on certain surfaces to safe or relatively safe levels, as defined by the EPA or pubHc health authorities. The article is usually cleaned with hot water and various germicidal detergents. Sanitization can be safe for a product in contact with intact skin or for food utensils, but it is not considered safe for articles to be inserted in the human body. Effective sanitization is a requirement in the processing of reusable medical suppHes before packaging and sterilization. It is also a requirement in the maintenance of utensils and containers used for food preparation. 

The I I cleaning procedures as a whole, compared with household laundering, are characterized by huge variations in the composition of the soils, types of surface to which they adhere, cleaning time available, etc. The optimum choice of enzyme type and dosage level normally has to be established through a cooperation between the customer (end user), manufacturer of the detergent, and enzyme producer. 

Pretreatment For most membrane applications, particularly for RO and NF, pretreatment of the feed is essential. If pretreatment is inadequate, success will be transient. For most applications, pretreatment is location specific. Well water is easier to treat than surface water and that is particularly true for sea wells. A reducing (anaerobic) environment is preferred. If heavy metals are present in the feed even in small amounts, they may catalyze membrane degradation. If surface sources are treated, chlorination followed by thorough dechlorination is required for high-performance membranes [Riley in Baker et al., op. cit., p. 5-29]. It is normal to adjust pH and add antisealants to prevent deposition of carbonates and siillates on the membrane. Iron can be a major problem, and equipment selection to avoid iron contamination is required. Freshly precipitated iron oxide fouls membranes and reqiiires an expensive cleaning procedure to remove. Humic acid is another foulant, and if it is present, conventional flocculation and filtration are normally used to remove it. The same treatment is appropriate for other colloidal materials. Ultrafiltration or microfiltration are excellent pretreatments, but in general they are... 

Even with adequate cleaning procedures it is still necessary to ensure that the inhibitor reaches all parts of the metal surfaces. Care should be taken, particularly when first filling, a system, that all dead ends, pockets, crevice regions, etc., are contacted by the inhibited fluid. This will be encouraged in many systems by movement of the fluid in service but in nominally static systems it will be desirable to establish a flow regime at intervals to provide renewed supply of inhibitor. 

Inadequate acid cleaning procedures also may introduce traces of copper into the boiler (typically originally present as copper-containing deposits), which can plate out onto clean metal surfaces and cause localized, anodic area pitting corrosion. 

Cleaning procedures include an internal washdown with a 0.5 to 2% soda ash solution, using a high-pressure jet. All wash water must be drained and deposits removed from the boiler. Usually, all external surfaces of the boiler are cleaned as well, in addition to the flue gas side of the economizer, air heater, and ID fans. 

Figure 5.39a shows the residual O Is spectrum obtained in ultra-high-vacuum after repeated cleaning cycle at 350-400°C. It is clear that there is a significant amount of residual O on the Pt surface which cannot be removed with conventional cleaning procedures. This by itself suffices to prove the presence of the omnipresent backspillover-formed effective double layer on the vacuum exposed Pt surface. 

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