High purity and highly corrosive liquids are often utilized in industries such as semiconductor processing and chemical manufacturing. Due to quality and safety concerns, these liquids generally must be contained in high integrity containers and dispensed using highly reliable dispensing systems.
Conventionally, the containers are drums formed of high purity polyethylene, such as those described in U.S. Pat. No. 6,045,000. Examples of dispensing systems suitable for use with these drums are described in U.S. Pat. Nos. 4,699,298, 5,108,015, 5,957,328, and 5,526,956. The connections, tubing, and fittings for handling these fluids are often formed from inert materials, such as various fluoropolymers. The tubing is commonly formed of Per Fluor Alkoxy (“PFA”), while the fittings and valve components can be formed of components such as PFA, Poly Tetra Fluoro Ethylene (“PTFE”), and other various fluoropolymers.
Conventional drums often include a bung opening and a drum insert connected to an upward and concentric nipple on the bung. A dispense head can be operably coupled with the drum insert and can include a main fluid passageway that connects to and sealingly engages the bung.
In many applications, the fluid that is dispensed from the drum can later be recirculated to the drum. This has been accomplished by using a recirculation passageway in the dispense head. However, these recirculation passageways can be uncontrolled and thus can remain in an open position when the dispense head is not connected to the drum, which can create a potential for spillage.
Also, recirculated fluid can create foam that can cause problems, such as foam entry into the vent lines, potential clogging, contamination of normally dry areas of the dispense head and gas refill line, and difficulty in emptying a drum with low levels of fluid. The foam can be created when fluid is recirculated into the dispense head and further when recirculated fluid is dispensed into the drum.
When using dispense heads to draw high purity, highly corrosive, and highly caustic liquids from drums, it can be important not to connect a dispense head for equipment requiring one type of liquid to a drum containing an incorrect or incompatible different liquid. To inhibit this, coded indexing sections and recesses have been provided in the dispense head and drum insert to enable assembly of the drum insert to the dispense head only when the correct coding exists. However, connecting a coded dispense head to a coded drum insert can require a great amount of force while turning the coding and holding down the dispense head. This process can involve a two-step operation of holding down the dispense head with one hand while rotating the code key with the other.