Chemical delivery system with spill containment door

Information

  • Patent Grant
  • 6276404
  • Patent Number
    6,276,404
  • Date Filed
    Thursday, September 14, 2000
    24 years ago
  • Date Issued
    Tuesday, August 21, 2001
    23 years ago
Abstract
A high purity chemical storage and delivery system and process with secondary containment, comprising; a cabinet for containing a canister of high purity chemical, a manifold in the cabinet for fluid connection between the canister and the cabinet for controllably dispensing high purity chemical; a control unit for controlling the dispensing of high purity chemical from the canister and the cabinet for a downstream use, a closeable opening in the cabinet for allowing loading and unloading of the canister from the cabinet, at least one door for closing the opening, a liquid tight secondary containment door in the opening for closing off a portion of the opening such that the secondary containment door is sized so that the portion is sufficient to define a volume in conjunction with the cabinet to contain the entire high purity chemical liquid contents of the canister.
Description




CROSS-REFERENCE TO RELATED APPLICATIONS




Not applicable.




STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT




Not applicable.




BACKGROUND OF THE INVENTION




The present invention is directed to the field of high purity chemical storage and dispensing for the electronics fabrication industry.




In the fabrication of electronic components, it is frequently required to have various high purity chemicals in liquid or two phase liquid/vapor state contained in canisters of various sizes for supply to the fabrication processes or for cleaning.




It has become the industry norm to contain these canisters of high purity chemical in cabinets typically made of metal and having various automated features such as dispense, level signals and changeout signals for when a canister is empty or near empty.




Since many of the high purity chemicals are toxic, caustic or environmentally controlled, it is important to contain the chemicals in the cabinet to avoid inadvertent vapor discharge or liquid discharge. Historically, inadvertent vapor discharge has been addressed by having the cabinet vented to a house or factory-wide abatement system. However, a risk also prevails for liquid discharge from a failing canister or the connections between the canister and the downstream manifold in the cabinet.




Various trays or dollys with marginal lips or sidewalls are known in the industry to contain modest liquid leaks, such as the advertisement of Victor Associates, Inc. showing a side view of a wheeled polypropylene container with a reservoir for containing 20 gallons of liquid. Secondary containment around the reservoir is mentioned.




Various carts with spill containment are illustrated in the advertisement from Terra Universal, Inc. showing Chem Carts A. through F.




The advertisement of Schumacher for the TransFill II-LRM indicates that 110% spill containment is achieved. This spill containment is achieved by use of a fixed cabinet integral spill pan.




An advertisement by Schumacher for the TransFill II-TFL uses a caster mounted tray with short sidewalls to provide partial secondary containment.




U.S. Pat. No. 5,950,693 shows a cabinet with a transportation cart, FIG. 3, #300, holding a container of chemical. The cart is used to hold a majority of any spill, col. 6, line 50.




The industry has long sought a safe and effective way to store canisters of high purity chemical for dispensing in electronic industry fabrication, as well as other industries. Various partial secondary containments have been used to contain partial spills. Various carts and trays are known for such use. More significant containment has been taught, but it usually requires an inability to access or service the failing container or requires greater height than the typical industry standard cabinet requires. With expensive electronic fabrication floor space at a premium, the industry has long sought an economical space conserving way to contain potentially significant chemical spills from containers while still being able to access the failing container without further spilling leaked liquid chemical and without changing the “footprint” of the cabinet storing the container in the fab.




The present invention addresses the above recited shortcomings of the prior art and succeeds in providing complete secondary containment without increased cabinet height and without elaborate additional carts or trays, as will be set forth in greater detail below.




BRIEF SUMMARY OF THE INVENTION




The present invention is a high purity chemical storage and delivery system with secondary containment, comprising; a cabinet for containing a canister of high purity chemical, a manifold in the cabinet for fluid connection between the canister and the cabinet for controllably dispensing high purity chemical; a control unit for controlling the dispensing of high purity chemical from the canister and the cabinet for a downstream use, a closeable opening in the cabinet for allowing loading and unloading of the canister from the cabinet, at least one door for closing the opening, a liquid tight secondary containment door in the opening for closing off a portion of the opening such that the secondary containment door is sized so that said portion is sufficient to define a volume in conjunction with the cabinet to contain the entire high purity chemical liquid contents of the canister.




The present invention is also a process for containing the entire contents of a high purity chemical canister in a cabinet, comprising; providing a cabinet for containing a high purity chemical canister with an opening for a canister, providing a canister containing a high purity chemical at least partially in a liquid physical state, providing a liquid tight secondary containment door in the opening for closing off a portion of the opening such that the secondary containment door is sized so that the portion is sufficient to define a volume in conjunction with the cabinet to contain the entire high purity chemical liquid contents of the canister, and in the event of liquid high purity chemical leaking from the canister when in the cabinet, retaining leaking liquid high purity chemical in the cabinet by liquid tight engagement of the secondary containment door to the cabinet.











BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS





FIG. 1

is a prespective view of a preferred embodiment of the present invention.











DETAILED DESCRIPTION OF THE INVENTION




The present invention is an apparatus or system for storing high purity chemicals such as tetraethylorthosilicate (TEOS), alkyl silanes, dichloroethylene, trimethylborate (TMB), trimethylphosphite (TMPI), boron-phosphorus-silicon glass (BPSG) and others used by the electronic fabrication industry.




The present invention provides secondary spill containment for liquid contained in a canister stored in a cabinet designed for storage and automatic or manual dispensing of chemical contained in the canister for use at an electronic fabrication factory or other chemical raw material consuming operation.




Preferably, the present invention provides secondary spill containment for the entire liquid content of a canister. More preferably, the present invention provides a safety margin for containment in excess of the content of a chemical containing canister. This could be 110% by volume containment of the liquid content of such a canister.




Additionally, the present invention provides a design so that in the event of a chemical spill of liquid from the canister, an operator could open the cabinet to assess the extent of the spill condition without leaking chemical and the operator could service the canister or access the spilled chemical for potential recovery or removal.




It is important in any secondary containment device to provide a mechanism which does not interfere with the normal changeout of a chemical canister, in light of the fact that typically canister changeout occurs frequently or systematically, and the need for secondary containment of spilled liquid chemical is an isolated, accidental occurrence.




The present invention provides a hinged door which closes off the lower portion of a high purity chemical storage and dispense cabinet in a liquid-tight sealing condition. This liquid tight secondary containment door is in addition to the normal door or doors which provide access to the interior of the cabinet where the canister is normally stored during operation.




The secondary containment door has a gasket which seals liquid tight with the frame of the front of the cabinet. The sealing engagement is achieved by the use of a locking device to hold the secondary containment door in the liquid tight sealed condition. The gasket can be any of the typical gasket materials which are compatible with the chemical being stored and can include; Teflon® products, polyvinyl chloride materials, various polybutylene rubbers, Kalrez® materials, Chemraz® materials, Viton® materials, EPDM® materials, Neoprene® material, Aflas® materials, silicone rubber and similar elastomers. The locking mechanism can be any of a number of latch mechanisms, including; a running bolt, a spring biased latch, etc.




The secondary containment door is preferably contained inside the normal door or doors of the cabinet. The secondary containment door is preferably hinged to one side of the front frame of the cabinet by one or more hinges, but it is also conceivable to hinge the door by what is known as a continuous “piano” hinge or fastening by other mechanisms such as a slotted track or bolt and nut fastening.




The secondary containment door is typically made from carbon steel which can be painted in a durable chemical resistant coating or paint. Alternatively, the door could be made of out any material capable of meeting local fire codes, such as a one hour fire rating, or the door could be 316 stainless steel.




The present invention will now be described with reference to a preferred embodiment illustrated in FIG.


1


.




A cabinet


10


for containing a canister


16


of high purity chemical, such as TEOS, is shown in FIG.


1


. The cabinet has side walls


12


and


14


, a floor


50


, a top


24


and a back wall which is not shown. The cabinet


10


is designed to be relatively gas tight against leaking externally in cooperation with a slightly negative internal pressure, to contain the high purity chemical for environmental and safety reasons, by the cabinet


10


being vented by exhaust duct


56


, preferably to a house abatement system, which are typically provided in factories, such as electronic fabrication factories (fabs). Such abatement systems are typically designed to treat the entire waste and effluent from the chemical processes occurring in a fab.




The cabinet


10


has a opening defined by sidewalls


12


and


14


and top and bottom


24


and


50


, which is closed off by relatively gas tight (against leaking externally) doors


20


and


22


. These doors are preferably hinged to the sidewalls


12


and


14


by hinges, one of which is illustrated as hinge


58


. Each door would have a locking mechanism


60


which engages at least the top


24


of the cabinet, but preferably the top


24


and the bottom


50


by appropriate latching. The locking mechanism is actuated by an appropriate latch, knob or key cylinder on the front exterior of the door


20


, not illustrated.




The canister


16


is mounted on a fork lift accommodating skid


54


, which is facilitated by two hinged ramps


46


and


48


, which facilitate the loading or unloading of the canister


16


in the cabinet


10


.




The canister


16


is hooked up to high purity chemical fluid connection to the cabinet by manifold


66


, partially illustrated and typically comprising an array of piping and valves which provides for the functions of controllable delivery of high purity chemical from the canister


16


to the cabinet


10


and downstream delivery from the cabinet


10


, not illustrated. Pressurizing gas, purge cycles and clean out are also contemplated for the manifold


66


, as typically required in the industry. Additionally, an emergency shut down switch an/or valve


64


is provide so that an operator can shut down the unit in the event of a power outage or upset condition. Switch and/or valve


64


is contemplated for local actuation. Switch and/or valve


64


projects through the door


20


when the latter is closed in a fluid tight sealing manner to facilitate access by an operator without opening the cabinet


10


.




Control of the cabinet


10


, the manifold


66


and the dispensing or shut down of the system is maintained by control unit


18


, which can be a process controller, onboard computer or a basic electronic mechanism controlled by a remote computer or operator. Appropriate controls, switches and keyboard are typically mounted on the face of the control unit


18


, as well as a system status electronic diagram or liquid crystal display, showing current process functioning.




Although high purity chemical content in the canister


16


can be determined by any number of ways typical in the industry, such as internal sensors of floats, capacitance or optical probes, or external sensors, such as ultrasonic sensors, it is preferred to mount the skid


54


and canister


16


on a scale


52


to determine high purity chemical content by weight, typically tared weight.




Spill detection in the cabinet can be electronically monitored and communicated to the control unit


18


or remotely to the operator or a central computer by sensing devices typical to the industry, such as; photo-optic sensors, Brewster angle photo optic sensors or float level sensors.




The spill detection probe is made up of an IR diode/phototransistor pair assembled with a quartz rod.




The components are installed with the optic ends facing the end of a quartz rod. The rod has a flat surface at the end where the optoelectronics are installed.




The other end of the rod is cone shaped. The probe is installed perpendicular to the bottom of the cabinet with the cone end facing down.




When the quartz cone is dry., the IR diode radiates into the quartz rod. Most of the lightwaves bounce off the inner surfaces of the end and travel back up into the quartz rod, exposing the phototransistor to the light.




This turns the phototransistor on, applying power to its emitter. A comparator circuit on the cabinet controller is connected to the phototransistor emitter through the backplane and circular connectors on the bottom of the electronics enclosure.




The output of the comparator circuit changes state when the voltage on the emitter is greater than the reference voltage at the comparator's other input.




When liquid is present at the quartz cone tip, the index of refraction of the quartz changes, allowing most of the infrared light to pass through the end out of the rod. The transistor consequently turns off, and no potential is applied to the input to the comparator circuit. The comparator has front-end pull-down resistors, which give rise to a zero voltage input.




The secondary containment door


26


comprises a single hinged door which spans the entire lower portion of the opening of the cabinet


10


from one side


14


to the other side


12


. Although it is possible to have two interacting doors, the single door is easier to make liquid tight.




The secondary containment door


26


is hinged to side


14


by hinges


28


and


30


, although it is contemplated that the door


26


could be connected to the cabinet by a “piano” hinge or other openable mechanisms. The non-hinged end of the door


26


is fitted with two latches


40


and


42


which operate as a fastener, which engages the side


12


of the cabinet. Latches


40


and


42


are simultaneously actuated by actuation axle


38


which also engages operator handle


62


.




The secondary containment door


26


has a sealing edge


44


, which can be a gasket of a silicon rubber material which deforms against cabinet edges


32


,


34


and


36


to form a liquid tight sealing surface.




The secondary containment door is preferably sized to have a height such that when engaged against the side walls


12


and


14


and floor


50


, it defines a volume in the base of the cabinet


10


of sufficient size to contain the entire liquid content of the stored canister


16


, and preferably in excess of such content so as to provide a margin of safety. Preferably, the door


26


is sized to contain 110% by volume of the rated capacity of the largest canister


16


the cabinet


10


is designed to accommodate.




The canister


16


is typically


316


stainless steel or other corrosion resistant metal. The canister could be aluminum, glass, or a Teflon coated container of any construction, including plastic.




The cabinet


10


including sidewalls


12


and


14


, top and bottom


24


and


50


, doors


20


and


22


and secondary containment door


26


are typically coated carbon steel sheet material, but they could be plastic or


316


stainless steel or aluminum.




The system operates by loading a canister


16


into the cabinet


10


typically by a powered or hand held forklift or pallet jack engaged in the skid


54


. The ramps


46


and


48


facilitate a forklift loading the canister


16


mounted skid


54


into the cabinet


10


. The ramps


46


and


48


are then raised or pivoted up in a closed position. Secondary containment door


26


is closed and latched or locked. The cabinet doors


20


and


22


are also closed and latched or locked after connecting the canister


16


for fluid flow to the manifold


66


which provides pressurizing gas, bubbling or vacuum dispensing of the high purity chemical from the canister


16


through the manifold


66


to a downstream fab use, as dictated by the control unit


18


. In an upset condition, canister


16


may leak all or a part of its liquid high purity chemical content into the base of the cabinet


10


, but this liquid will be contained by the secondary containment door


26


which is in liquid tight sealing condition with the front frame of the cabinet


10


opening. This allows only the surfaces of the secondary containment door


26


to be engineered to a tight dimension to create the liquid tight seal and only the gasket


44


of the door


26


to be designed for liquid contact. The doors


20


and


22


can be less rigorously designed and their sealing engagement need only be designed for fluid engagement and material compatibility. By use of the secondary containment door


26


which only seals a part of the opening of the cabinet


10


, an operator is able to open doors


20


and


22


to inspect the condition of the interior of the cabinet and any upset condition and potentially service the canister


16


or cabinet


10


without fear of spilling leaked liquid chemical out onto the fab floor. By using a latched and hinged secondary containment door, the cabinet allows an operator to readily load and unload the cabinet to changeout canisters without compromising the secondary containment feature. Ease of operation and protection from liquid spills are addressed by the present invention to overcome the problems in prior art storage and dispensing systems.




The present invention has been set forth with regard to one preferred embodiment, but the full scope of the present invention should be ascertained from the claims which follow.



Claims
  • 1. A high purity chemical storage and delivery system with secondary containment, comprising; a cabinet for containing a canister of high purity chemical, a manifold in said cabinet for fluid connection between said canister and said cabinet for controllably dispensing high purity chemical; a control unit for controlling the dispensing of high purity chemical from said canister and said cabinet for a downstream use, a closeable opening in said cabinet for allowing loading and unloading of said canister from said cabinet, at least one door for closing said opening, a liquid tight secondary containment door in said opening for closing off a portion of said opening such that said secondary containment door is sized so that said portion is sufficient to define a volume in conjunction with said cabinet to contain the high purity chemical liquid contents of said canister.
  • 2. The system of claim 1 wherein said secondary containment door is hingedly connected to said cabinet.
  • 3. The system of claim 1 wherein said secondary containment door has a gasket which sealably engages said cabinet when said secondary containment door is closed.
  • 4. The system of claim 1 wherein said secondary containment door has a fastener for locking said secondary containment door in a closed position in said cabinet.
  • 5. The system of claim 1 wherein said secondary containment door is inside said at least one door.
  • 6. The system of claim 1 wherein said at least one door is a pair of hingedly connected doors which entirely close off said opening in said cabinet.
  • 7. The system of claim 6 wherein said pair of hingedly connected doors have a fluid tight seal with said cabinet.
  • 8. The system of claim 1 wherein said cabinet has a canister connected to said manifold.
  • 9. The system of claim 8 wherein said canister is sized for up to 220 liters of high purity chemical.
  • 10. The system of claim 1 wherein the floor of said cabinet has at least one hinged ramp for loading or unloading said canister in said cabinet.
  • 11. The system of claim 10 wherein there are two hinged ramps.
  • 12. The system of claim 1 wherein said cabinet has a scale mounted in a floor of said cabinet for providing a signal of the canisters content of said high purity chemical to said control unit.
  • 13. The system of claim 1 wherein said cabinet has a fluid exhaust conduit in a top of said cabinet to remove fluid high purity chemical from said cabinet for downstream abatement.
  • 14. The system of claim 1 wherein said cabinet has a shutoff valve to discontinue fluid flow from a canister in said cabinet connected to said manifold.
  • 15. The system of claim 1 wherein said secondary containment door is sized so that said portion is sufficient to define a volume in conjunction with said cabinet to contain 110% by volume of the high purity chemical liquid contents of said canister.
  • 16. A process for containing the entire contents of a high purity chemical canister in a cabinet, comprising; providing a cabinet for containing a high purity chemical canister with an opening for a canister, providing a canister containing a high purity chemical at least partially in a liquid physical state, providing a liquid tight secondary containment door in said opening for closing off a portion of said opening such that said secondary containment door is sized so that said portion is sufficient to define a volume in conjunction with said cabinet to contain the high purity chemical liquid contents of said canister, and upon the leaking of liquid high purity chemical from said canister when in said cabinet, retaining leaking liquid high purity chemical in said cabinet by liquid tight engagement of said secondary containment door to said cabinet.
  • 17. The process of claim 16 wherein said secondary containment door contains 110% by volume of a high purity chemical liquid content of said canister in conjunction with said cabinet.
  • 18. The process of claim 16 wherein a signal is communicated to a control unit on said cabinet in the event liquid high purity leaks from said canister in said cabinet.
  • 19. The process of claim 16 wherein said secondary containment door forms a liquid tight seal with said cabinet using a gasket.
  • 20. The process of claim 16 wherein said secondary containment door lockably closes against said cabinet.
US Referenced Citations (2)
Number Name Date Kind
5950693 Noah et al. Sep 1999
6056024 Noah et al. May 2000
Non-Patent Literature Citations (4)
Entry
Advertisement from Terra Universal, Inc., Chem. Carts A-F.
Advertisement of Schumacher for TransFill™ II-LRM.
Advertisement of Schumacher for TransFill™ II-TFL.
Advertisement of Victor Associates, Inc. of wheeled polypropylene container with reservoir.