st26

SprayDec12

Alternatives to the Water Bath, continued checked for pressure, typically using a Teledyne “Tap Tone” a pressurized solution of ethanol and water. Gauges used for gel device. This novel machine measures the force required to slightly products usually last about 60 production shifts. squeeze and momentarily deform the side wall of the can as it Because nitrogen and CAIR closely follow Charles’ Law, the BOV passes between two sensing belts. It is first necessary to standardize pressure increase upon heating to 55°C (130°F) is quite small. the sensing unit by checking a non-pressurized can, followed by For example, a filled BOV dispenser having an initial pressure of a can of known pressure. The tiny deflection distance is about 5.00 bars (72.5 psi-g.) at 21°C (70°F) would only rise to 5.68 bars linear with the internal pressure. Recognizing that there will be (83.3 psi-g.)—or by 10.8 psi. It follows that the dispenser could small differences in metal thickness, exact temper and so forth, be immersed in boiling water without deforming or bursting. In the computerized device can only read pressures within a range the interest of completeness, a recent COSTHA (Council on of ±4% for small aluminum cans, and up to ±10% (or even Safe Transportation of Hazardous Articles, Inc.) petition states ±12%) for large tinplate dispensers. Fillers work to minimize this that some BOVs utilize hydrocarbon propellants to reduce the spread, including keeping a log of previous productions of the magnitude of the pressure drop during use. This would not only same product. However, the accuracy is sufficient for the machine invite permeation problems at the junction of valve and bag, but to reject any gross leakers or ungassed cans, and assure that the would eliminate the beneficial effects of Charles’ Law when BOV slightly higher pressures at 55°C (131°F) will be within legal limits. dispensers are heated. For fillers not having a DOT PHMSA Special Permit for every After hot water bathing and manual testing, the cans are often BOV product to be filled, the production line will have to include a again rinsed with water, blown dry, allowed time to fully dry, and hot water bath. Many models are useful, such as the one produced are then automatically fitted with any of a large array of spray by IWKA Packaging Technologies, where the bath itself is only heads, foam or liquid spouts and covers, before being packaged for about one meter (39") long. Any leakers are marked with an “ink shipment. stick” so they can be readily detected and discarded upon leaving the machine. The hot water in the bath heats the nitrogen of The Regulatory Picture CAIR gases in the exo-space to at least 55°C (131°F), although Some compartmentalized aerosol cans, as well as others, present the product in the bag may only be increased in temperature by possible challenges to the outmoded DOT definition of an aerosol. about 2°C (3.6°F). This is not a problem. Even if the products Several decades ago, the DOT defined an aerosol as a self- were to be heated to 55°C (131°F), expanding the bag very slightly, pressurized packaging system containing a product (liquid, paste the pressure would still be almost the same. Once the cans exit or powder) and a propellant substance. There was no requirement the water bath they are usually checked for both stem height and that the two had to be mixed. At the time, DOT Administrator Ian pressure. To prevent the product from contaminating the Bourdon Roberts stated that the inclusion of a “product” was done to avoid tube of the gauge, the assembly is pre-pressurized to about 0.4 bar the filling of aerosols with pure, highly flammable hydrocarbon (6 psi-g.) above the expected BOV dispenser pressure. Should propellants, such as those used for fueling camp stoves. The any product get into the gauge it can usually be rinsed out using definition differs from those in the U.N. and other multinational organizations, which allow “aerosols” to include pure propellants. It has caused the DOT to process and issue a large number of Special Exemptions, renewable annually and sometimes causing costly delays in company marketing plans. The recent COSTHA BOV valve with petition to the DOT PHMSA requests that they flattened-out bag simply issue an omnibus Special Exemption or else rewrite their troublesome definition of “aerosols,” thus saving the U.S. industry, and themselves, a huge amount of processing and maintenance work. Although the BOVs and other compartmentalized self-pressurized dispensers all contain pure propellants, separate from the product, a strong case can be made that they comply with the DOT PHMSA definition. Ancillary aspects are that the propellants are generally Detail of wrap non-flammable and are never expelled during consumer use. They are also only a very minor portion of the can contents. Firms that specialize in the production of BOV BOV valve with BOV valve products actively support the COSTHA petition, rolled -up bag inflated although it contains a few statements that could be improved. Other industry organizations are actively This BOV with inflated bag only contains compressed air, studying it, including the solicitation of member but in practice it is filled with the product to be dispensed. comments. By inflating with air, and then determining the total bag Special Exemptions have also been solicited and volume by the simple expedient of immersing it in water approved for the use of hot water bath alternatives contained in a graduate (a glass cylinder with volume in the production of BOV dispensers. In practice, the petitioning etchings on one side), one can determine or confirm the 100% filled bag volume. From that, the typical rule is to fill firm submits a substantial report, defining their product, the the bag with product to about 72% of that volume. requested revision, a safety analysis, experimental results, quality assurance limits, scope and party or non-party objective. Since Photos and Graphic by Spray Technology 26 Spray December 2012


SprayDec12
To see the actual publication please follow the link above