bcp system for the anl-fnal scspf

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A description of the original controls system for theBCP system is covered in [10]. The modifications andimprovements to the original control system have beenimplemented and are presented in this paper.The BCP System for the ILC S0/S1 processing programwill be primarily used to remove the contaminants on theoutside cavity surfaces to prevent fouling of the interiorsurfaces during the hydrogen degasification bake cycle.Until large grain and single-crystal cavity productionmatures, the relevancy of processing the inside surfaces offine-grain ILC cavities for vertical performance testing atvery high fields (>25MV/m) is limited due to the BCPquench field limit well below that of EP. However, BCPprocessing on large-grain and single crystal cavities hasshown great promise as a replacement for EP [11]. TheBCP System will play a significant role in provingwhether multi-cell large-grain or single crystal cavityprocessing can eliminate EP from the processing sequence.For the near future, the role of the BCP System will be toprovide external surface polishing of S0/S1 cavities andinternal polishing on other 1.3 GHz cavities not in theS0/S1 program.IndustrializationOne of the BCP System’s fundamental design preceptswas to build a tool with features attractive to industry.High volume cavity surface processing will need toolsthat are safe and easy to use with robust design whichallow quick change between operations. The BCP Systemdesign accomplished these goals by focusing on operatortooling and controls system. These features are easilyduplicated in any BCP System constructed in the future.The BCP System design is modular in that many shapesand sizes of cavities can be processed without makingmodifications to the BCP System itself as long as theprocessed surfaces are within the capacity of the system.Each cavity type requires its own tooling (jackets, holdingfixtures, etc.), but the connections to the BCP System andthe method in which the process takes place are the same.SafetyProcesses that use concentrated HF require extremeuser caution and tight procedure control. At ANL, aformal safety program at the SCPF has been implementedthat dictates proper HF handling techniques, appropriatepersonal protective equipment, and emergency responseprocedures. Any operation utilizing HF or otherconcentrated acids must obey the approved SCPFumbrella safety documents. In addition to the umbrellasafety documents, setup, operation, and shutdownprocedures are all controlled via checklist. This checklistensures all proper precautions specific to the proceduresare taken.The BCP System was designed to limit the BCP (HF)handling and contact opportunity to an absolute minimum.At no time does an operator physically manipulate theBCP other than when rolling BCP supply drums enclosedin secondary overpack containers. During routineoperation, the only opportunity for contact is duringfitting disconnection after a procedure. All fluid (BCP,Figure 2: BCP System flow schematic. Operator GUI screen capture.safety and implementing uncomplicated flow mechanics,cooling water, dilute waste) manipulation is performed by
programmable logic controller (PLC) controlled flowmechanics. Should leaks in the plumbing occur, all likelyareas reside within secondary containment.Operator exposure to dilute waste is also extremelylimited. All dilute waste generated during a procedure isneutralized and pumped to a drain by an automatedneutralization system. Operator involvement in aprocedure is limited to connecting the cavity to the BCPSystem, stinging BCP drums, and running the procedureremotely from a control center located outside thechemistry room.Process ControlThe fluid flow mechanics are required to handle BCP,ultra pure water for rinsing and cooling, and dilute wastesimultaneously. Expecting an operator to manipulatethese fluids with numerous valve openings and closingsand pump activation and deactivation while monitoringseveral sensors is unreasonable in a process that issensitive to so many variables. Therefore, a PLC andsoftware interface with a PC was chosen to perform theseoperations. An operator is expected to key into theinterface the procedure to be performed, move theprocesses from one step to the next, and verify that thecontrol system is responding to all sensors as needed.DESIGN DETAILSBCP and Neutralization SystemsThe fluid mechanics are divided into separatesubsystems for BCP and cooling water flow. The BCPSystem flow schematic is shown in Figure 2 with thecooling water loop shown on the right and the BCP loopon the left. The separate loops do not share like plumbingwhich prevents inadvertent mixing of acid and water. Thesubsystems meet at the cavity/jacket but are separated bythe resonator wall. The cavity is enclosed in an etchingjacket and connected to five separate lines: BCP supplyand return, cooling water supply and return, and coolingwater overflow.The water cooling loop receives water from a gravityfeed tank which is automatically pre-filled before aprocedure begins. The cooling loop includes plumbingand pumps between a heat exchanger and the etchingjacket. The water flows on the opposite side of the etchprocess thereby removing the reaction heat. The reactionheat carried away by the water is removed from thecooling loop in a plate and frame heat exchanger. Anexternal chiller supplies the heat exchanger with 6C to10C chilled water. This double heat exchangearrangement prevents acid from escaping the chemistryroom to the primary chiller in the event of a leak betweenthe etching jacket and cavity.BCP is supplied to the process via direct pumping froma pre-cooled drum. The BCP flows from the supply drumthrough the cavity and back to the drum. At theconclusion of the etching process, the BCP in the cavityand system plumbing flows into an acid dump tank whichresides below the process. The acid is immediatelypumped into the process supply drum. Once the cavity isfree of BCP, ultrapure water (UPW) from the gravity feedtank flushes through the system thereby rinsing the cavityand all lines that carry acid. The dilute waste generateddumps into a dilute waste tank next to the acid dump tank.The rinse cycles continue until the dilute waste reaches apH of 4 or higher as measured by a pH sensor located inthe dilute waste tank. All of the dilute waste is pumpedfrom the tank to the automated neutralization system.The neutralization system contains a 95 gallon storagetank, 10 gpm recirculation pump, and metering pump thatdoses liquid NaOH into the tank. Redundant pH sensorsin line with the recirculation pump communicate with thePLC which ‘tells’ the metering pump to dose caustic intothe tank until the pH of the dilute waste is above 5 – alevel safe to dump into the ANL sewage system. Noconcentrated acid is neutralized.All materials used to construct the BCP andneutralization systems are approved for HF handling.PVDF, Teflon, fluorinated Viton, and PFA are commonmaterials suitable for HF. Where possible, bead andcrevice free PVDF tube welding was employed tominimize the number of fittings. All valves and pumpsare certified for HF as well as other acids.The BCP System is shown in three photos in Figure 3as installed. The left photo is the neutralization systemand its secondary containment. The center photo showsthe BCP system and PVC test vessel. The right photoshows local ventilation hoods installed to capture processfumes released at the BCP supply drum that residesbeneath the hood openings.Figure 3: Neutralization system, BCP System, andventilation ductwork.Ventilation SystemRemoving process fumes (NO x , HF vapor) is critical tosafe operation. The ventilation system was designed tocapture fumes at the source, or potential source in the caseof leaks. All plumbing and vessels are located in a largeframe covered by a Lexan skin. The Lexan skin forms afume hood with the draft created by a large suctionmanifold located at the top surface of the frame. TheBCP System plumbing was enclosed in a fume hood notto capture process fumes but to gather fumes frompossible leaks. Should a leak occur, an operator cansafely neutralize it without the risk of fume exposure.
Page 1: BCP SYSTEM FOR THE ANL-FNAL SCPF*A.
Page 5: commissioned. The control system an

bcp system for the anl-fnal scspf

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