National Industrial Chemicals Notification and Assessment Scheme

14.1.5Safe work practices

adherence to the manufacturer’s instructions of starting up, operating and closing down of vapour degreasing tanks;

holding workload in the degreasing zone for some time before drawing out to allow adequate draining/drying time;

loading the parts to be degreased into the basket at an angle to facilitate draining of the solvent. Improper loading of parts can lead to trapping of solvent in the parts with evaporation into the atmosphere.

regular checks of the sump temperature indicator to determine changing of solvent.

Other safe work practices that may be followed to reduce solvent loss are:

avoid overloading of the tank. A general recommendation is that workloads not exceed more than 50% of the total interface area;

baskets, racks or hangers used to hold the metal parts for degreasing should not be made of porous materials as they will absorb trichloroethylene and remove it from the degreaser;

if sprays are used to assist in cleaning, spraying should be done below the vapour layer; spraying at a downward angle also helps to reduce emissions;

slow speed for entry and exit of workloads. Increasing the speed of entry of workload displaces the solvent out of the tank while rapid extraction of parts leads to solvent vapour being pulled out of the tank;

solvent soaked rags and swabs should be disposed of in closed metal bins;

topping up of the tank with the solvent should not be done when the degreaser is hot. Trichloroethylene should be pumped in at a low level with the cooling water system and the rim ventilation operational. Adding solvent from the top while the plant is hot can lead to high worker exposure. Regular checks should be made of the solvent levels;

placement of vapour degreaser tanks away from sources of direct draughts such as open windows or doorways or a fan as this is likely to lift vapour over the freeboard of the tank into the surrounding work areas;

installation of the tank in a well ventilated area so that any vapour that may be dragged out with the work will be quickly removed;

location of the tank away from naked flames and welding operations as trichloroethylene decomposes at high temperatures to phosgene, hydrochloric acid and chlorine.

The Australian Standard AS 2865 (1995) “Safe working in a confined space” (Standards Australia, 1995) should be strictly adhered to for entry into and work in a confined space.

Regular and frequent cleaning of degreasers avoids the baking of contamination on to internal walls. AS 2661 (Standards Association of Australia, 1983)includes the safe work practices to be adopted during maintenance and cleaning of a vapour degreasing plant.

14.1.6Personal protective equipment

Dermal exposure may be prevented by use of protective gloves. It is important to select gloves that are resistant to the chemical exposed. Information provided for assessment indicates that gloves are generally provided at most workplaces. However, most of the workplaces did not specify the type of gloves used. Types of gloves specified by some end users were nitrile, rubber and viton gloves.

Recommendations on types of glove to use with particular chemicals are provided by many glove manufacturers, and a number of books and databases. Recommendations are usually based on tests of degradation, that is, changes in physical properties of gloves following contact with the chemical such as swelling or hardening, and permeation, that is, the movement of the chemical through the material at a molecular level. Two common measures of permeation are breakthrough time and permeation rate. It should be noted that test results from gloves made of the same generic material can differ due to differences in manufacture, and so test data relating to specific glove brands may be preferable to test data relating only to material type.

Recommendations based on these types of tests should provide a starting point only for the selection of gloves, and in choosing gloves, regard should always be had for the particular work activities for which the glove is to be used. The glove with the highest breakthrough time and lowest permeation rate may not always be necessary. Factors that need to be considered in conjunction with test data include:

duration, frequency and degree of chemical exposure;

the degree of physical stresses that will be applied;

the temperature of the chemical (heat may change the permeation rate of the chemical through the glove);

in the case of formulations, the degree of protection that the glove provides for other ingredients, and possible synergistic effects;

the likelihood of the glove coming into contact with water or other chemicals that may effect the glove’s performance against the chemical for which it is recommended.

No work processes involving long periods of immersion of hands in trichloroethylene were identified, however some work processes presented the possibility of intermittent or occasional contact with liquid trichloroethylene (hot and/or cold) or trichloroethylene products. This information suggests that gloves with ratings that indicate protection against intermittent exposure, as opposed to total immersion, may be acceptable in most workplaces.

A comparison of the ratings provided by some primary sources for gloves made from various types of material as summarised in table 32 shows a general agreement on materials that are not recommended, or considered to provide poor protection against trichloroethylene. However, there is greater variability about the types of gloves which are recommended. Materials recommended by one or more sources include PE/EVAL, PE/EVAL/PE, Silvershield, chlorobutyl, chloroprene rubber, and teflon. The materials not recommended include butyl, chlorinated polyethylene (CPE), neoprene, polyethylene (PE), and nitrile/PVC. Materials over which there are different recommendations are: natural rubber, PVC and nitrile, which are recommended in the Australian Standard but not recommended by other sources; and PVA and viton, which are rated as poor by the ACGIH, but recommended by other sources. It can be seen that materials unanimously not recommended by sources included some materials that were recommended by some MSDS, i.e neoprene and polyethylene. PVC, nitrile and natural rubber were also recommended on some MSDS, although the majority of the sources recommended that they not be used.

A survey of six retail outlets for protective gloves in Sydney and Melbourne found that PVA gloves were the glove usually recommended for protection against trichloroethylene. Prices quoted for one brand varied from $37 to $44. Two outlets mentioned that PVA breaks down easily in the presence of water. Viton gloves were recommended by one outlet, with price quoted at $314 per pair. One outlet recommended PVC gloves for jobs involving low level of exposure, quoting a price of $2 a pair. This survey highlights the practical aspect of choosing gloves, and the role of manufacturers and suppliers in making available appropriate gloves and information.

For formulated products gloves should be selected on the basis of the component with the shortest breakthrough time.

Protective gloves are to be used when contact of skin with trichloroethylene is likely, such as during loading and unloading of work parts from the vapour degreaser, during cold cleaning, clean up of spills or during other work processes when splashes are likely.

Covering of arms and legs is useful during handling trichloroethylene and overalls or long sleeved shirts and trousers may be used.

Respiratory protection is not required in most situations. However a face mask with organic vapour cartridge should be worn when exposures are likely to be high, such as during clean up of large spills.

The NICNAS industry survey indicated that if entry into a degreasing tank was necessitated for cleaning, workers were provided with self-contained breathing apparatus.