Patent Application
20050127096
The transportation, storage, and use of hazardous chemicals presents a significant management challenge. Hazardous chemicals are designated HAZMAT by the U.S. Dept. of Transportation and are subject to strict regulation as to labeling and containment. For example, hydrogen peroxide in industrial concentrations of 35%, 50%, and 70% ship under UN2014 (oxidizer), caustic soda under UN1760 (corrosive), strong acids such as phosphoric under UN1805 (corrosive), and alcohol such as isopropyl under UN1219 (flammable). The safe use of these chemicals is of paramount importance, as a significant number of accidents occur as a result of misuse, spills, failed and improperly designed dispensing equipment.
Many of the advances in dispensing technology have taken place in the field of oil and gasoline. The rupture of underground gas storage tanks and inadvertent spills and leaks has led to incidents of substantial environmental pollution. Resultant clean up costs and regulatory fines have created a strong incentive for design of safety equipment that prevents or at least contains leaks. U.S. Pat. No. 5,527,130 discloses an underground piping system which contains leaks in an underground enclosure and communicates to a surface dispenser via double piping that maintains an interstitial space between pipes. U.S. Pat. No. 5,040,408 discloses a secondary containment system in which a primary line may be completely installed and integrity tested before the secondary piping is installed. Telescoped piping also permits bending without leaking at seams. The prior use of double walled vessels for containment of a primary containment breach is known (See U.S. Pat. No. 4,568,925). The situation where two incompatible chemicals are used together in a common application has also been addressed. U.S. Pat. No. 6,463,611 discloses the sequential pumping of separate chemicals through a common manifold, with an intervening rinse of the manifold between pump actions.
In many instances, business firms have shunned hazardous chemicals in favor of chemical alternatives deemed safer to handle and use. In the meat packing field, for example, in which peroxide bleach is required to whiten offal products, many plants discontinued use of liquid hydrogen peroxide and substituted sodium percarbonate. Principal concerns were burns, eye injuries, spills resulting in fires, burned clothing, and other hazards. Caustic soda or strong acid based liquid products also pose a concern, so that firms substitute products in solid form. While chemicals in solid form such as sodium percarbonate or caustic soda may have some perceived safety advantages, they actually involve more direct handling than liquid versions, and are approximately twice as expensive than the liquid chemicals from which they are derived. For example, sodium percarbonate is a chemical complex formed by spraying hydrogen peroxide onto a soda ash substrate and then drying. The product upon re-hydration simply liberates hydrogen peroxide into solution. Caustic soda beads are derived from a 50% sodium hydroxide stream from a chlor-alkali plant through a series of expensive processing steps. These additional costs are incurred because of safety concerns.
There exists a substantial need in many industries to provide a dispensing system for hazardous chemicals such as hydrogen peroxide and other oxidizers, strong acids and bases, and flammable products, that is safe, and can secure the delivery of these substances to the point of use, free of leaks, adverse contact with the environment, and persons having responsibility for their use.
The present invention operates under a novel theory of hazard, namely, engineering a chemical dispensing device directly taking into account, in a quantitative aspect, the risk factors associated with design defects in conventional systems that lead to accidents and other mishaps, that have been substantiated historically. The basic premise of this theory is to safely convey a liquid hazardous chemical from a source to its point of intended use, utilizing a dispensing system having minimal risk of failure, default, or endangerment to the environment or individuals having responsibility for handling or using the chemical.
It is preferable that the dispensing system of the present invention be dedicated to each hazardous chemical being dispensed and that no system physically incorporate dispensing means for more than one chemical in the same enclosure, even if two or more chemicals are not chemically incompatible. Thus, the dispensing system herein may dispense chemicals from a chemical source to more than one point of use, but the identity of the chemical should be the same for each dispensing apparatus.
According to the present invention, an apparatus for safe dispensing of a hazardous chemical or chemicals provides an enclosure formed upon substantially six sides including an opening on one side and having closed top and bottom surfaces, and a back plate mounted therein preferably on the back side. There is an L-shaped base plate having a vertical mounting lip placed within the enclosure and secured by fastening means to form upper and lower cavities in the enclosure. The horizontal base plate is attached to the back plate only by the fastening means through the mounting lip, and is not sealed at the edges. The base plate horizontal surface may be dimensionally smaller than the enclosure to provide additional liquid communication between the upper and lower cavities.
One or a plurality of stackable pumps materially compatible to the enclosure are mounted on the base plate. This pump or pumps are disposed between a materially compatible chemical inlet tube and chemical outlet tube. The inlet and outlet tubes pass through the side or sides of the enclosure to each pump and are secured to the sides by bulk head fittings. The tubes are bent in a somewhat S-shaped pattern and rotated in an angularity to permit axial alignment of input and output tubes to each pump. The tubes are connected on the pump end by materially compatible compression type fittings.
At the bottom of the enclosure and directly beneath the base plate, chemical collecting means sealable to the vertical sides of the enclosure is provided to prevent liquid reflux to the upper cavity of the enclosure. The collecting means channels liquid through a connection to one or a plurality of drain means in the bottom surface of the enclosure. The apparatus may also be provided with flushing means comprising a tubular loop connecting a source of decontaminating fluid to the chemical inlet tube, and further having a drain connected to the chemical outlet tube, and a valve controlling ingress of decontaminating fluid.
The present invention further provides a method for dispensing liquids in which conveyance of the liquids is carried out through materially compatible components, have a flow generative of characteristic vibration from action of a pump or pumps, the energy of vibration being dispersed and dissipated by resonance of the system by materially compatible resonable components.
a and b is a plan view of the base plate.
In conventional dispensing of hazardous chemicals, an apparatus typically includes a pump mounted on a frame or in an enclosure connected to a source of chemical, usually a drum or tote via flexible plastic tubes. Couplings are generally plastic involving attachment of a plastic hose of one type of material joined to a nipple of a second type of plastic and secured by a hose clamp. Alternatively, hard plumbed PVC piping may be employed with standard PVC unions, T fittings, and elbows. The most common type of pump for dispensing liquids ranging in volume from a few ounces to several gallons is a diaphragm or double diaphragm pump. Movement of the internal shuttle causes substantial vibration. Over a period of prolonged use pump vibrations weaken the seals between components causing plastic hoses to loosen and be displaced, and union and couplings to fracture and leak.
Because of the severe consequences to persons and the environment of a system failure involving hazardous chemicals, a new design of equipment was undertaken. FMC Corporation has constructed a proprietary data base categorizing several decades of historical mishaps and accidents involving hydrogen peroxide. For example, fifty percent of all accidents resulted directly from poor maintenance, using the wrong equipment, or using equipment of incompatible materials of construction. Other categories of lesser frequency mishaps include operator error, forklift accidents puncturing drums or totes, and allowing incompatible chemicals to commingle. Most accidents are preventable if equipment has provision for proper conveyance of the chemical, and containment of the chemical in the event of a failure in conveyance.
In accordance with the present invention, in preferred embodiments, all components of the dispensing system are materially compatible. Materially compatible means that all components are made of the same type of material having identical coefficients of thermal expansion, stress absorption, and degree of flexibility. For hazardous chemicals the use of all stainless steel components is preferred, although some types of plastic may be suitable if all the components are molded of the same plastic composition. This includes enclosure, pump bodies, conveyance tubing, couplings, fittings, back plate, base plate, and bulk head fittings. Stainless 316 gauge is preferable to other alloys. All metal-plastic, plastic of one type wedded to another plastic type, and metal of one type wedded to metal of a different type are to be strictly avoided.
In preferred embodiments, all components are mounted rigidly, and no shock absorbent materials are utilized. It is found that attempts to cushion components of the system to absorb vibrations actually tends to localize stress and increase the incidence of failure, whereas rigidity tends to dissipate and distribute the energy of vibration by a resonance effect throughout the entire structure of the dispenser.
Referring to the drawings,
In preferred embodiments, the enclosure contains a base plate 7 which is secured to a back plate (not shown) by a fastener. The fastener is preferably a bolt with a lock washer, but may alternatively be a weld or an adhesive. In the embodiment shown in
In preferred embodiments, the pumps 5a and 5b are disposed between two stainless steel tubes 8a, 9a, and 8b, 9b respectively. Tubes 8a and 8b are chemical inlet conveying tubes and tubes 9a and 9b are chemical outlet tubes for pumps 5a and 5b respectively. The inlet and outlet tubes 8b and 9b, for illustration purposes, are connected to the pumps at the respective inlet orifice (bottom inlet) and outlet orifice (upper outlet) by compression type couplings comprising a body 8e and 9e, a compression inducing nut 8c and 9c for the respective inlet and outlet tubes respectively, and a stationary nut 8d and 9d to provide torque in the coupling. Such couplings are used throughout the dispenser wherein connection between elements of the conveying system is required. The preferred couplings are manufactured by Swagelok Company under U.S. Pat. Nos. 6,279,242 and 6,131,963 herein incorporated by reference, although other similar but less satisfactory couplings are available commercially. The principal advantage of the Swagelok coupler is a double ferrule feature that crimps the tubing metal so that leaks are virtually impossible, under conditions of wear from vibration, at the interface of elements such as tubing to tubing, or tubing to pump connections.
At the end opposite connection of the conveying tubes to the pump, the tubes 8a, 9a, 8b, and 9b pass through the enclosure through orifices (not shown) and are secured to the enclosure side or sides by bulk head fittings. These are preferably of the Swagelok construction and comprise a lock nut 12, a body portion 11, and a retaining or stationary nut 10.
In preferred embodiments, the pumps may be air powered or electrical. Air powered pumps are preferred because most industrial plants have an ample supply of compressed air, and because air actuators are generally more reliable.
In preferred embodiments, at the base of the enclosure in the lower cavity, chemical collecting means 23 having generally sloping sides 19 to a drain means 20 is sealed to the four sides of the enclosure. In the event of a leak in a pump or a coupling, chemical drains around the base plate edges, descends through the sloping collecting means 23 to the drain means 20, thereby providing safe containment of chemical. The chemical collecting means is preferably sealed to the enclosure by welding and application of an epoxy chemically inert sealant. A spray bar 16 is provided in the upper cavity to permit flushing and rinsing of the entire enclosure with a decontaminating fluid such as water or a chemical neutralizing buffer solution.
This Application claims priority to U.S. Provisional Patent Application Ser. No. 60/493,665, filed Aug. 8, 2003.
| Number | Date | Country | |
|---|---|---|---|
| 60493665 | Aug 2003 | US |
