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S H O R T C O M M U N I C A T IO N

Anne-Virginie Desruelle Bruno Schmid

The steam laboratory of the Institut de Medecine Navale du Service de

Santedes Armees: a set of tools in the service of the French Navy

Accepted: 9 January 2004 / Published online: 17 June 2004 Springer-Verlag 2004

Abstract Accidental exposure to hot water steam is apotential risk in the French Navy, and particularly onnuclear submarines or ships. Direct human exposure tothis extreme environment during an accident leads to

death in a short time. In order to protect the crewmembers of the French Navy, a laboratory was createdat the Institut de Me decine Navale du Service de Santedes Arme es (IMNSSA). A set of tools was developed tostudy the effects of exposure to hot water steam atmo-spheres on human physiology and on the protectivecapacities of textile fabrics and equipment. A testingdevice allows the quantification of the protectivecapacities of fabrics under steam stresses. A thermalmanikin and a steam climatic chamber allow the eval-uation of the protective capacities of equipment. Thetests on fabrics and on garments were in good agree-ment. Water vapour impermeable fabrics and garments

provide greater protection in steamy conditions. More-over, the thicker the sample or garment, the higher theprotection it gives. Care should be taken to verify thatfabrics keep their thermal characteristics under steamstress. These characteristics, measured under standardcomfortable conditions, are not always indicative ofthe protective abilities of the fabrics under steamyconditions.

Keywords Manikin Testing device Hot water steam Protective equipment

Introduction

Direct exposure to superheated water steam jets or tohot saturated environments is a potential work hazardfor some navy staff, nuclear industry employees, and

firefighters. Despite the potential risk, no job legislationon human exposure to hot water steam exists (Etienneet al. 1999). Only a few old scientific references havedealt with the effects of steam exposure on animals

(Aviado and Schmidt 1952; Moritz et al. 1945). Thesestudies have shown that pulmonary damage appearedmore quickly and was more pronounced with a hotsaturated air jet compared to a dry jet. Although sev-eral studies have been made on burns or scalds on theskin due to conductive or convective exposures (Branset al. 1994; Bull 1963; Lawrence and Bull 1976; Rippleet al. 1990; Siekmann 1989, 1990), we were unable tofind any studies dealing with hot water steam injuriesand skin damage. Different biological risks appearduring accidental exposure to superheated water steam(Montmayeur et al. 1999). One of the main risks isthermal. Condensation of water occurs on the skin,

clothing, and in the airways and provides very highlevels of heat energy to the surface on which it occurs.In this context, the delay before injury to the skindepends on the ability of the wearers garment to slowdown or stop heat transfer to the skin. Classically,clothing and textiles are defined by their thermaland evaporative resistances (McCullough et al. 1985,1989). These characteristics are measured by testingdevices under standard protocols. However, understeam jet conditions, it is doubtful whether thesecharacteristics, adapted to moderate environments,keep their significance for the comparison of clothingor textiles.

To aid the protection of the crew members of theFrench Navy, a steam laboratory was created at theInstitut de Me decine Navale du Service de Sante desArme es (IMNSSA). A set of tools was developed in thelaboratory including a testing device which can generatesteam jets or a steam atmosphere, a thermal coppermanikin, and a climatic steam chamber. The testingdevice allows the quantification of the protectivecapacities of fabrics under steam stresses, while thethermal manikin and the climatic chamber allow theevaluation of the protective capacities of equipment.

A.-V. Desruelle (&) B. SchmidInstitut de Me decine Navale du Service de Sante des Arme es,BP 610, 83800 Toulon Naval, FranceE-mail: [email protected]

Eur J Appl Physiol (2004) 92: 630635DOI 10.1007/s00421-004-1123-4


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Materials and methods

The testing device

The testing device can be used in two configurations: asteam jet or a steam atmosphere. It is composed of asteam generator (Sano Clav Wolf, Bioblock Scientific,France) which has a maximal internal temperature of

142C, corresponding to a pressure of 3 bars. Steam isintroduced from a copper tube (11 cm in length and witha 5-mm internal diameter) oriented toward the centre ofthe measuring cell. The textile sample support is com-posed of a PVC double frame in which the sample isinserted. The two sides of the frame present a circularwindow corresponding to the measuring cell diameter.The face exposed to steam is equipped for attachment tothe measuring cell and to make a close contact betweenthe cell and the internal side of the sample (the skincontact face). The measuring cell (Fig. 1) is composed ofa heat flux sensor (Episensor 025, JBMEurope, France)fixed on a hollow cylindrical box in which water circu-

lates at a regulated temperature of 33C. The side of thebox facing the steam source (or the internal side of thesample) is made of an external resin layer (to minimisethe radial heat flux) over an aluminium plate. The heatflux sensor, imbedded in the resin layer, is fixed to thealuminium plate to facilitate the transfer of heat to thewater. The sensor measures the heat flux and also thetemperature of its surface under its external black paintlayer.

In the steam jet configuration, the sample supportand the measuring cell are fixed on a moving base. In thesteam atmosphere configuration, this moving base isreplaced by an isolated box in which the steam atmo-

sphere is created. In this configuration, the steam isinjected by an electrovalve connected to a thermal reg-ulator which keeps the box temperature at 80C. In both

configurations, the measuring cell is connected to a datalogger (DaqBook 216, IOtech, USA) and then to acomputer that allows the observation and archiving ofthe parameters measured (software: Daqview 7.1,IOtech, USA).

The climatic chamber

The climatic chamber (7 m3

) allows the generation of afully saturated atmosphere at 80C. The steam atmo-sphere is created by an air-conditioning (heating systemand humidifier) working in a closed circuit. The steamcan be rapidly evacuated for security reasons. Thethermal conditions inside the chamber are regulated by acomputer. Air and dew point temperatures are measuredand stored on the same computer. The air temperaturecan be regulated between that of the laboratory and90C (1C) and the dew point between those of thelaboratory and 80C (1C).

The copper thermal manikin

The thermal manikin is divided into nine separate seg-ments. The surface of the manikin is made of coppersheets and is regulated by water circulated inside copperpipes distributed on the internal face of the sheets (reg-ulated surface: 1.349 m2). The inside of the manikin isisolated to limit heat storage and natural convection.This manikin presents two distinctive features comparedto the majority of the other thermal manikins. It is aswatertight as possible and is cooled rather than warmedduring the tests. The cooling system is composed of aprimary input which is then divided into three secondaryinputs: one for the top (head, arms, front and rear trunk)

and one for each leg. Water is distributed into the dif-ferent segments, and each segment has a separate wateroutput. The temperature of the primary input is regu-lated between 20.0 and 40.0C (0.2C), and the tem-perature of each segment are measured. The water flowsare measured (McMillan, USA) and regulated at theoutput of each segment between 0.06 and 1.0 l/min(5%). Thus, total and local heat fluxes can be calculatedfrom the temperature and water flows.

Textile evaluation using the testing device

The protocol used was the same for all conditions andcorresponds to a 10-min exposure to steam stress. Threeconditions were tested: J5, J10 and J15, with respectively5, 10 and 15 cm between the steam output of the gen-erator and the external side of the samples. Atmosphericconditions (ATM) served as the control. The referencetests (REF) correspond to direct exposure of the mea-suring cell to the steam stresses [4.312 (0.026), 3.394(0.039), 2.804 (0.033) and 0.702 (0.117) W/cm2 respec-tively for J5, J10, J15 and ATM]. Each test (REF orsamples) was repeated three times.

Fig. 1 The measuring cell, view of the side facing the steam jet orthe internal side of the sample

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The heat flux was measured every second throughoutthe steam exposure. The following variables were cal-culated with the heat flux values: SMF (steam mean flux,W/cm2), corresponding to the average of the heat fluxover the last minute of the exposure for the three tests:AHT (total amount of heat transferred, J/cm2), corre-sponding to the sum of the heat transferred to the cellover the 10-min exposure time; and PR (percent of REF,%), corresponding to the ratio between the SMF of thesample and those of the corresponding REF.

The samples were classified depending on their phys-ical characteristics and capacities to limit or modify heattransfer under steam stress. The different samples testedin this study are presented in Table 1. TC was taken fromthe working suit of the submarine crew members. TLDwas taken from light NBC (nuclear, biological andchemical) clothing for decontamination (P. Boye ).

Equipment evaluation using the manikin

Garments and equipment were exposed to a steam

atmosphere in the steam climatic chamber. The thermalmanikin was fitted with the equipment to be tested andplaced in the centre of the chamber. The climatic con-ditions were an air temperature of 80C, with a stepwiseincrease in humidity up to the maximum allowed by theequipment. Due to the high level of condensation on theregulated surface of the manikin, the chamber was un-able to reach saturation with the manikin inside. Thus,humidity was increased step by step to the maximumpossible for each test. The heat flux value at saturationwas extrapolated using exponential regression. The sameprocedure was applied for the garment tests. For eachstep, the mean temperature of the surface of each

segment of the manikin was regulated at 33C.

Temperature and water flows were measured for eachstep over 7 min. Local and total heat fluxes were thencalculated for each step, and the heat fluxes at saturationwere calculated by extrapolation. The equipment itemswere classified depending on their heat fluxes (global andlocal values).

We present the results for five garments: TLD, TC,TBoy, TVTN and TMat. TLD and TBoy are watervapour impermeable garments. TC, TVTN and TMatare water vapour permeable. TC, TVTN and TLD arethin garments, while TBoy and TMat are thick. TC isthe working suit used by the crew members of Frenchsubmarines. TLD is a light NBC garment for decon-tamination (P. Boye ). The other garments are proto-types. All these garments completely cover the manikinsurface except the head. The comparison between gar-ments was made using the heat fluxes measured on thecovered surface.

Results

Figure 2 shows some typical examples of the heat fluxpatterns during the 10-min exposure to condition J10.During REF tests (curve 1), the heat flux increasedrapidly (in 23 s) to a steam steady state [SMF = 3.394(0.039) W/cm2]. During the TC tests (curve 2), there wasa peak of heat flux at the beginning of the exposure.Thereafter, the heat flux decreased to finally stabilise atthe level maintained until the end of the exposure [SMF1.606 (0.031) W/cm2]. During the TX tests (curve 3), theheat flux rapidly reached a first steam steady state.However, after about 140 s, the flux increased againuntil the end of the exposure. During the TLD tests(curve 4), the heat flux rapidly reached the steam steady

state [SMF=0.808 (0.024) W/cm2].

Table 1 Characteristics of thesamples.TThickness (mm), RTthermal resistance (m2K/W),Re evaporative resistance(m2Pa/W), no measurement

T RT Re Description

TC 0.50 0.0252 4.3 Kermel/viscoseTX 0.40 0.0121 398 Knitted fabric with a laminated external faceTLD 0.25 0.0198 10,000 Non-woven fabric with a laminated external faceP 0.001 Black polyethylene foil3D4 4.00 White polyethylene tridimensional fabric

Fig. 2 Typical patterns of heatflux observed during the 10-min

exposure to steam undercondition J10 (see text)

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Figure 3 shows the impact of two methods ofwaterproofing a textile sample (TC) on the heat fluxpattern achieved under J10 conditions. The water-proofing was achieved either by adding a polyethylene

foil of 10 lm thickness (P) either in front of the TCsample (P+TC) or behind the TC sample (TC+P) or bysoaking the TC sample just before the tests (TCm).When P was placed in front of TC (P+TC), the patternwas typically that of an impermeable fabric. When P wasplaced behind TC (TC+P), the pattern was the same asTC alone, but the peak was significantly decreased and

the SMF was lower. When TC was soaked before thetests (TCm), the peak was also significantly decreasedand the SMF was the same as for TC alone.

Table 2 shows the main results observed under con-

dition J10 when the air layer behind the fabrics (TC andTLD) was artificially increased by adding one (3D4) ortwo layers (3D8) of a 3D polyethylene waffle fabric of4 mm thickness. Increasing the thickness of the air layerbehind the fabrics led to lower SMF, AHT and PR,whatever the permeability of the fabrics. For theimpermeable fabrics, the same thickness of polyethylenewaffle fabric (or a thinner layer) also led to lower SMF,AHT and PR levels.

Figure 4 shows the pattern of the heat flux observedwith TX during the three steam jet conditions. After afirst increase at the beginning of the exposure to steam,the heat flux increased again after a delay at steady state.

This delay before the increase and the range of theincrease were dependent on the conditions.Figure 5 shows the local and total ratios between the

mean heat flux of the samples and these of the REF test(PR, %). Generally, the results observed with garmentsand fabrics have the same meaning. The water vapourpermeable garments TC and TVTN allow higher levelsof heat flux and PR, since these two garments are thin.

Fig. 3 Heat flux of samplescomposed of TC during the firstminute of exposure to conditionJ10

Table 2 Main results observed after increasing the thickness of theair layer behind the fabrics under test condition J10. SMF Steammean heat flux (W/cm2), AHTamount of heat transferred to thecell in 10 min (J/cm2), PR percent of the REF heat flux transferred

Sample SMF AHT PR

REF 3.394 (0.039) 2038.2 (26.4) TC 1.606 (0.031) 968.8 (6.2) 46.5 (1.3)TC+3D4 0.591 (0.017) 381.5 (7.1) 17.4 (0.7)TC+3D8 0.388 (0.005) 249.9 (4.3) 11.8 (0.3)TLD 0.808 (0.024) 473.3 (22.0) 23.7 (1.0)TLD+3D4 0.069 (0.001) 41.3 (1.2) 2.0 (0.0)TLD+3D8 0.042 (0.000) 24.6 (0.0) 1.3 (0.0)

Fig. 4 Heat flux observed withTX during the three steam jetconditions

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However Tmat reached approximately the same level ofPR as TLD due to the higher thickness of the fabric,which is composed of different textile layers. The bestprotection was given by Tboy, TLD and Tmat, and theleast by TC. Figure 5 also shows that there is a greaterdifference between the local ratios with permeable gar-ments, especially between the limbs and the other bodysegments.

Discussion

In a general manner, the tests on the fabrics and on thegarments are in good agreement. With the same or alesser thickness, the textile samples impermeable to hotwater steam limited heat transfer due to exposure tosteam more efficiently than the permeable samples. Atthe beginning of the exposure to the steam jet, thepermeable samples showed a peak of heat flux proba-bly due to the complex phenomena of condensation,diffusion and absorption of water inside the sample,which results in the release of high levels of heat(Farnworth 1986; Lotens and Havenith 1994). Water-proofing of the permeable samples led to the loss

of these phenomena, which also explain the resultsobserved with TX, an impermeable sample. In thiscase, after a delay during exposure to the steam jet, thesample seemed to change its characteristics and pro-gressively became permeable. While the denaturationwas not instantaneous, no peak of heat flux wasobserved, rather a regular increase in flux depending onthe rapidity of the denaturation, which in turn wasdependent on the intensity of the steam exposure. Thisdenaturation was reversible for this sample. Hence,maintenance of the characteristics of textile samples

should be evaluated under conditions of steam expo-sure to avoid skin injuries.

Moreover, the thicker the sample, the higher the ther-mal protection it gives. However, a maximal thicknessexists, above which the gain in protection is not sufficientto justify the supplementary increase in thickness.

Similarly, impermeable garments provide more effi-cient protection under steam stress. Furthermore, aloose-fitting cut (with a thick air layer between the gar-ment and the skin) allows an increase in the level ofthermal protection of a thin garment. The ergonomic

consequences of this kind of protection for human tol-erance to work are yet to be evaluated.

In conclusion, in order to evaluate the protectivecapacities of textiles and clothing, the steam laboratorydevelops specific tools and adapts expert appraisal pro-cesses. The laboratory also studies the physiopathologyof steam injuries and trains the crew members likely tobe exposed to steam stresses.

Acknowledgement This study received funding support from De le -gation Ge ne rale de lArmement.

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Fig. 5 Ratio between the heatflux of the garments and thoseof the REF. TAvFront of thetrunk, Tarback, BGand BDleft and right arms, CG and CDleft and right thighs, MGandMD left and right legs, Tot total

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