J.M. Ingram

Cleaning metal components after the Montreal Protocol : Introductory review

Until recently, the manufacturing and finishing industries have placed heavy reliance on the use of pure methyl chloroform or chlorofluorocarbon solvents to achieve acceptable levels of cleaning or precleaning of metal components. Much effort has been devoted since the signing of the Montreal Protocol to finding replacement cleaning agents for these and other banned or controlled substances and it is now clear that a variety of different cleaning processes must be developed. In the long term it is likely that the vast majority of industrial cleaning will be carried out in aqueous solutions making it necessary to investigate the special problems involved in cleaning difficult components. A review, which summarises the issues and current problems being encountered in the search for replacement cleaning processes, is presented. Also considered are the relevant techniques and experimental procedures which can be used to investigate surface cleanliness and related phenomena.

Fundamental study of generation of interfacial temperatures with metal surfaces and coatings under conditions of sliding friction and mechanical impact

Abstract The measurement of surface temperatures generated by sliding friction is discussed and experiments are carried out using dynamic thermocouples to determine surface temperatures arising from sliding friction and mechanical impact. Experimental results over a very wide range of loading and velocity conditions show an appreciable degree of similarity with calculated values using the equations given in part one of this study. Impacts with a 7·3 kg projectile with nickel and nickel coated test heads onto an angled steel anvil, have shown that very high transient surface temperatures can be reached. At velocities above 5 m s−1, surface temperatures in excess of 1000°C are obtained within a contact duration of less than 2 ms. The lower temperatures recorded in the case of impacts involving nickel plated steel test heads correspond to the temperature difference across the thickness of the coating rather than to the difference in surface temperature and the cold junction.

Fundamental study of generation of interfacial temperatures with metal surfaces and coatings under conditions of sliding friction and mechanical impact Part 1 - Thermal analysis and theoretical evaluation of surface temperature

Abstract A study has been carried out to evaluate the surface temperatures reached on sliding metallic surfaces over a wide range of conditions. This is of interest for a number of reasons, including determining the conditions of mechanical sliding friction which might be associated with failure or loss of adhesion of a coating intended to prevent galling or seizure and establishing the likelihood of igniting any pyrophoric substances present on the surface. In Part 1 of the study, the uncertainties involved in determining the surface temperature are considered and a thermal analysis performed to illustrate how variations in the properties of the contacting surfaces, together with the loading and sliding conditions influence the surface temperature. A numerical analysis of the heat transferred into the bulk of the metal indicates that in many cases the generated temperature increase will significantly decay over a comparable depth to that of an engineering metal coating.

Aqueous-based Cleaning of Components Intended for Service in Oxygen Enriched Atmospheres—Introduction and Review

SUMMARY An introduction is given to the relevant issues concerning the cleaning of oxygen service equipment and a review of the formulation and performance of current aqueous-based cleaning processes is reported

Replacing TCA and CFC-113 with HFE and HFC based azeotropes and n-propyl bromide based solvents for wipe cleaning metal components: Source evaporation rates and models

SUMMARYIn replacing traditionally used solvents for external wipe cleaning applications with newer and more environmentally friendly solvent systems, account has to be taken of their volatility since this has a great bearing on the cost of the cleaning process as well as on occupational health hazards to operatives. To determine the concentrations of solvent vapour which will be produced in the workspace and to make sure that these do not exceed occupational exposure limits, it is necessary to know not only the workspace ventilation conditions but also the source evaporation rate of the solvent used. A study carried out to compare the evaporation rates of the traditional solvents under varying conditions to those of the proposed replacement substances is reported and a detailed discussion given of the usefulness of evaporation models to predict emission rates.

On the Performance and Mechanism of Ultrasonically Cleaning Metal Components with Environmentally Acceptable Organic Solvents

SUMMARYExperimental results are presented which allow comparison between the cleaning performance of recently available environmentally friendly solvents and traditionally used solvents. Particular emphasis is given to considering the removal of different kinds of grease contamination from components with blind holes or crevices. The fundamental principles underlying the process of removal of organic contamination from metal surfaces with organic solvents are discussed and a simple mechanism postulated to explain the gradual decrease in the decontamination rate that occurs as the cleaning process progresses. It is considered most likely that the primary role of ultrasonification in the cleaning of metals is to promote detachment of contaminant from the surface rather than enhanced transport of dissolved material away from the surface/solvent interface.

A study of the dispersion of solvent vapour in the workspace during wipe cleaning of metal components with organic solvents - A Monte Carlo uncertainty analysis

A Monte Carlo simulation using a diffusion based exposure assessment model was employed to aid forecasting of solvent vapour concentrations in the workspace during wipe cleaning of metal component. Range values for the important variables were chosen so as to be appropriate for wipe cleaning with either highly volatile solvents such as Vertrel-MCA or HFE71DE or with less volatile solvents such as n-propylbromide (nPBr). Emphasis is put on confirming that the range values of variables and the distributions taken are applicable to the workplace environment so that the simulation values obtained are reasonable estimates of the true vapour concentrations. The results obtained using Monte Carlo forecasts are considered most useful when taken in conjunction with the relevant occupational exposure limits for the solvents in question

Optimising the selection of metal cleaning processes or cleaning agents using desirability functions

SUMMARY It is suggested that the use of desirability functions offers a formalised and consistent means of taking into account both judgemental and numerical factors in the selection of the best process or agent for a particular application. An illustration of the use of desirability functions is given in the selection of a solvent cleaning process for decontaminating components intended for service in oxygen-enriched atmospheres. Final selection is made using a criteria matrix of factor/response desirabilities.

Development of Aqueous-based Cleaning Procedures for Decontaminating Metal Components intended for Service in Oxygen Enriched Atmospheres

SUMMARY Experimental results are presented which allow evaluation of a number of aqueous based cleaning agents for decontaminating metal components intended for use in oxygen enriched atmospheres. The development of a process sequence for removing contamination from difficult areas of metal components such as those containing blind holes, crevices or internal passageways is reported. From the results of the study it is considered essential with aqueous-based cleaning solutions to ensure that fresh streams of solution are repeatedly introduced into the cavities. Ultrasonic cleaning action alone is unable to decontaminate blind holes and recesses within a practicable time scale. An effective way of achieving the cleanliness required for oxygen service components, is to use ultrasonification to enhance general surface cleaning together with a short duration high velocity spray to decontaminate blind holes or cavities.