Protection against steam and condensate

Concern about use of steam and hot water condensate for different processes in the oil sector and related heavy industries has brought into consideration questions regarding the level of protection flame-resistant (FR) clothing can provide against these two elements, the need for materials specifically designed to protect against them, and appropriate methods to evaluate materials intended for this application. Currently, workers who handle steam on a routine basis normally wear over-garments that completely cover the body and are made from liquid- and vapour-impermeable materials (Fig. 25.1). These tend to be uncomfortable, may be stiff especially in cold weather, and often interfere with carrying out tasks. Textile materials used in manufacturing FR/steam-protective clothing systems must be evaluated in terms of steam/hot water permeation or penetration as well as heat transfer. Specifications for these clothing systems should be developed to prevent partial or full-thickness burns from heat transfer onto the skin during or after an exposure incident. The development of appropriate test methods and protocols, evaluation of existing protective materials, and establishment of specifications for the design of protective clothing against steam and hot water are urgently needed.

Few studies have been found in the literature that focused on the steam/hot water permeability of thermal protective clothing, its effects on FR properties of fabrics, or consequences for the wearer. Most research on steam effects has focused on firefighters, where the steam is generated through exposure of water to a high-energy heat source, and does not deal with industrial steam under very high pressures. Watkins et al. (1978) reported on their design for firefighting apparel that included an outermost layer that was FR and waterproof, and a liner comprising three fabric layers to protect the firefighter from heat transferred through the outer shell. These researchers hypothesized that, although steam would be able to penetrate the system, it would gradually move through the layers so that the skin would be acclimated rather than causing the pain threshold to be reached. This is unlikely to be the case, however, for steam at pressures found in the oil industry. Watkins (1995, p.16) stated that when condensation occurs, a clothing system for environments where high heat and moisture are present must insulate the wearer from the point at which condensation takes place. She also pointed out that to avoid injury a clothing system is required that can control heat flux or the rate at which vapour reaches the body surface.

Rossi et al. (2004) studied the transfer of steam through various layered textile systems as a function of sample parameters such as thickness and permeability. The influence of different sweating rates on the heat and mass transfer during steam exposure was assessed. To simulate perspiration from the human body, a cylinder releasing defined amounts of moisture was used. They determined that impermeable (waterproof) materials normally offer better protection against hot steam than do semi-permeable ones. The transfer of steam depended on the water vapour permeability of the samples, their thermal insulation and their thickness. Increasing the thickness of the samples with a spacer gave a larger increase in protection for the impermeable samples compared to the semi-permeable materials. Measurements with pre-wetted samples showed a reduction in steam protection while measurements with a sweating cylinder showed a beneficial effect of sweating.

The need for more research regarding steam permeability is evident as several factors relevant to the steam/hot water permeability of FR protective clothing have not been thoroughly addressed. Furthermore, the effects of hot condensate, especially with contaminants, do not appear to have been studied. It seems likely that vapour impermeable clothing will be required under many conditions where steam is involved. Research focusing on garment design parameters is therefore needed to deal with potential conflicts between protection and concerns about comfort and heat stress.

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