Acid Hood Operations - The University of Texas at Dallas
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1. Norm 36 049 Normality of H2 SO 4 solution Units are in mass equivalents per Liter DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 18 of 25 Step 3 Calculate the amount of Na OH required to neutralize a given amount of Sulfuric acic The law of neutralization claims that the number of gm equivalent weights of base neutralize same number of gram equivalents of acid Stated in different form the Neutralization rule claims H SO 4 2Na OH gt Na SO 4 2H0 Norm V gt Norm V Claim Norm is the Normality of the acid Therefore to calculate the volume of sodium hydroxide required to neutralize say lt liters of sulfuric acid V5 AL Norm V4 V Claim equation rearranged Norm V 7 54 L ANSWER The volume of sodium hydroxide required to neutralize 4 Liters of sulfuric acid is 7 54 Liters takng into account the solution concentrations specified DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 19 of 25 Appendix B Neutralization Staff Procedure Arnold Duenes Purpose This appendix is intended to explain to Clean Room Staff how to run a neutralization operation on Leatherwood Plastic s General 4 ft Acid Bench 189 NOTES e Execution of this procedure is limited to trained Clean Room Staff Only e Proper Personal Protective Equipment is requires when operating bench or during maintenance e The name of this h2. 2006 AUTHOR Roger Robbins Arnold Duenes Page 21 of 25 li Highlighted in red when closed b Actual and set point pH are displayed next to the neutralization tank symbol i The top pH reading is the actual pH li SP Set Point pH reading should be 6 0 a programmable parameter c There are 3 other pneumatic operated valves in the diagram i V1 2 recirculation valve stirs contents of tank li V1 3 waste drain valve valve opens when pumping to drain ii V1 5 DI Water fill valve d There are two pumps in the diagram i Recirculation pump next to neutralization tank li Caustic Supply pump next to caustic reservoir e The Neutralization tank icon displays a real time liquid level i Note these tank level parameters 1 The sink valve closes when a 90 tank level is reached 2 At5 or less the hood will switch from drain to Dl Water fill 3 DI Water will fill tank to 35 full programmable parameter f The caustic reservoir icon will always show green full unless it is empty i There is only one float sensor at the bottom of the caustic reservoir li Wear appropriate PPE when refilling the 2 gal caustic reservoir with 50 concentrated NaOH Splash back is common because of the viscosity of the solution 1 Wear acid gloves apron and face shield 4 During normal operation users are trained to be aware of the tank level especially when it is very close to 90 In such a case it is best to flow DI Water from the gooseneck
3. ide icietiacio ia iaicda 15 PRICING Ai s 17 Neutralization Chemistry Theory ccccccccssscccsseccceeeeeceeseecseececseuseeseaeeessuseessaaeees 17 APDONOIX B orema semmec das lidades 20 Neutralization Stal Procede arsane owen aia deci anh 20 O oe taba tedeatet a tty Os hake caren nt ehdncmaR ean oe ciate aha tuaticdaasielnsautunenmion 20 NOTE S perc ee ie ee aa eee 20 Neutralization IMFOGUCHION aiii 20 Neutralization Procedure iii 20 DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 2 of 25 Neutralization ParaMeters c ccccccccececcececceccccececcececeacecceceacaceacstecueneauscesuscesuenesneas 23 Process Monitor SEIU D inci 24 CAUSTIC PAO Se Us 24 DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 3 of 25 Acid Hood Operations Roger Robbins 2 14 2006 Arnold Duenes C Mydocuments CleanRoomGeneral Equpment Hoods Acid AcidHoodOperation doc Introduction This document describes the Clean Room s new 4 foot Acid Hood from Leatherwood Plastics Inc of Lewisville Texas This hood is intended to be our general purpose acid hood for a single user at a time We fondly call it the Acid Hood but it actually has a real name HAQ1 Description The acid hood is constructed of a chemical and fire resistant white plastic PVCC with a 3 by 2 5 foot perforated work surface Included at the work deck level is a De lonized water
4. time is allowed Never place a chemical container on the floor Acid Hood glassware is stored on the cart to the left of the hood Always remember to turn off the hotplate when you are finished Dispose of your acids in the sink while running a moderate amount of DI water with the acid o Rinse your acid containers thoroughly with DI water o Wet wipe and dry off the work surface so the following person will not be harmed by liquid acid spills e When you are finished clean up your work area and return all the tools and PPE you have been using to their proper place especially papers and rags DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 16 of 25 Appendix A Neutralization Chemistry Theory Acid Base Neutralization Reactions 1 11 201 RR How much 50 Sodium Hydroxide solution is needed to neutralize n liters of 96 Sulfuric Acid Solution Step 1 Calculate the gram equivalent weights of the reactants The gram equivalent wt of lt element is the gram atomic weight divided by the oxidation number of the reacting element in the compound of interest Given gm Oo 7 PNaOH 1 53 50 NaOH by wt Solution Densities m from bottle m O PE9SOA4 1 84 96 Ho SO a by wt Atomic Mases Na OH Na 23gm O 16gm H 1gm Gm Eq Wt of Na OH Na O H 40gm Equiv Wt of Sulfuric Acid H gt SO a H 1gm S 32gm O 16gm GmEqWt of H SO 4 SAAS 972m Equiv Wt o
5. 3 Photohelic Exhaust pressure gauge left and alarm horn right Exhaust The photohelic pressure gauge Figure 3 measures the exhaust pressure in the exhaust line above the hood and if the pressure falls out of the acceptable range it will trigger the alarm horn Figure 3 which will then complain very loudly and light up the red alarm light on the control panel to light up Figure 2 If this happens quickly bring your work to a safe conclusion and discontinue the use of the hood Also immediately notify clean room staff There may be a general loss of exhaust requiring clean room evacuation Follow staff direction By the way the exhaust alarm cannot be silenced except by shutting off the main power to the hood Do not attempt to change the photohelic pressure gauge set points DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 6 of 25 Machine Start Stop The Green HOOD START button on the control panel turns on the electricity to the hood functions The Red MACHINE STOP button turns off most of the electricity to the hood The hood is generally left ON all the time This control is used when service or problem diagnostic is required EMO Button The EMergency Off button is used if the hood is having an electrical problem that portends of immediate emergency If there is smoke coming from the insides or the hotplate is seriously overheating etc Please don t hesitate to u
6. Acid Hood Operations Roger Robbins 2 14 2006 Arnold Duenes The University of Texas at Dallas ERIK JONSSON SCHOOL OF ENGINEERING DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 1 of 25 Acid Hood Operations Roger Robbins 2 14 2006 Arnold Duenes Table of Contents Acid Rood Operations ide 4 TOG GC UOM Nao oia 4 SS CUO UIO Ns ds 4 Feature Detall oranana a olanetadena teats auteamtona tee tinetants ecatariedeaaiadss 5 A as eee enone aren Mere NERO MORE er Dain Dee mn PON OER SMO ONE MT a Some Re eee eee ee 5 BY Ue KAR E EE PTE A Stach ase nine E E E EEEE earnats T S TETA 5 gt A N E ee ee eae 6 Machine Sat is ey Seo 7 EMO BUOM gee ent peo eT e ed tado pedos 7 Audio Enunco Maite ste esses acto eee een a eo nes Beg teeter eet as 7 TOUGH SCRE CM aininn EE 7 Process Ir Call CS rre 8 FIO MONA ac dr ts aetna te 8 A O A ct ninth etna ad ate 8 Acad Neutralizaco n Tankian 9 N Gun and DI Water Spray ccccccooccnnccccccnnccnoncnnnononcnnnononcnnnononcnnnnnonnnnnnnnnnnnnnnonens 9 AE AAC IC AU uscar E O 9 Operating SOWA Etuien a ice 10 OVON OW ae E a E 10 E a E A 10 Timer Opera ON sar la A A 11 Neutralization SY St lei da dees aus 11 Netitralliza ton CMOIMISUY rn ii 13 Ghemical DETNINONS tutti ie 13 A A O terete hav oh A 13 Gram Equivalent Well dos 13 NOM iaa 14 DEN Mitin ani iB vids 14 Concentrato Meana dada cda 14 Chemical Cal CulanonS astas a 14 FIUIES 201 Opera Mai a
7. LITR ZA TICO i TANK 15 GALLON Figure B2 Select the Neutralization Process 2 Inthe top center of the Neutralization Process Screen a rectangular tab should be highlighted in red and read STOP NEUTRALIZATION This confirms that the Neutralization is ENABLED a Ifthe tab is highlighted in green and reads ENABLE NEUTRALIZATION you will need to depress the tab to enable the neutralization process i If this is the case you will need to determine why neutralization was disabled in the first place 1 Under normal conditions users are not allowed to disable neutralization 2 It is possible that neutralization was intentionally disabled by Clean Room staff as a result of a tool issue problem There should be a sign if this has occurred li Actuation of the machine EMO shutdown button will automatically disable neutralization b When neutralization is first enabled the recirculation pump will turn on for 5 minutes This is a default action to stir the solution to obtain a proper pH reading The time is programmable 3 Familiarize yourself with the plumbing diagram as displayed on the screen in Figure B3 A EATHERWOOD LOGGED IN DI WATER a O u i STE RECIRC WH WA 3 2 pH a SP 6 0 pH FILL SP 35 CAUSTIC NEUTRALIZATION RESERVOIR TANK 15 GALLON Figure B3 Neutralization Process Screen a The sink drain valve is V1 1 i Highlighted in green when opened DOCUMENT TITLE Acid Hood Operations 6 2
8. f Sulfuric Acid Step 2 Calculate the Normality of each solution The normality is the number of gram equivalents per liter a chemical concentration unit Na OH a Calculate the number of grams of Na OH in one liter of solution from the density and concentration percentage 3 gm PNaOH 1 53x 10 L Solution Density Since the concentration is only 50 Na OH the number of gms of Na OH in one liter is PNaoH 0 5 1L 765 gm Mass of sodium hydroxide in 1 Liter DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 17 of 25 Now to find the number of equiv wts of Na OH in one liter the Normality of the solution we divide the above number of gms in one liter by the equiv wt PNaOH 05 gm equiv wt in 1 L Norm _ Na 0 H Normy 19 125 Normality of Na OH solution Units are in mass equivalents per Liter H2 SO 4 a Calculate the number of grams of b SO 4 in one liter of solution from the density and concentration percentage gm 3 PH2s04 1 84 10 7 Solution Density Since the concentration is only 96 H SO x4 the number of gms of SO in one liter is Pos04 0 96 1L 1 766x 10 gm Mass of Sulfuric Acid in 1 Liter b Now to find the number of equiv wts of 4S0 in one liter the Normality of the solution we divide the above number of gms in one liter by the equiv wt 2PH2804 0 96 _ gm equiv wt in 1 L Norm AS ESO 2 H S 4 0 98gm
9. faucet reach 90 full then wait for neutralization to complete normally it takes about 20 minutes for the tank contents to be neutralized and pumped to acid drain This practice is intended to prevent noxious levels of acid waste to collect in the sink while neutralization is taking place a Summary i If tank level is 87 90 full flow DI Water into the sink from sprayer or gooseneck to achieve 90 full and start of Neutralization process Wait for process to complete 20 min ii At 90 full the sink valve will close and neutralization will take place if needed if contents are already neutralized they will be pumped to drain when the 3 min stabilization time expires iii Inform potential users that the hood is unavailable when the sink valves close they will know not to use hood iv Visually check the level of caustic in the under deck reservoir Add NaOH if necessary Figure B4 DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 22 of 25 Figure B4 Under Deck caustic tank left and neutralization tank Right The caustic tank will slide out enough to fill through the lift off lid at the front top Neutralization Parameters 1 Normally the hood is set to level 1 access OPERATOR LOGGED IN 2 To access the menus where all programmable parameters are found you must log in to level 5 access LEATHERWOOD LOGGED IN a To accomplish this you must first log out b Log in using the tool s
10. ges reserved for staff If you need a parameter changed please see the staff person in charge of the hood Push the thin top rectangle button that says Login if you have to login Figure 8 shows a screen with that button reading Log Out since the hood is already logged in The resulting screen will look like that in Figure 9 Press the central button entitled Log In Please This brings up the keypad screen shown in Figure 10 Figure 9 Log in Screen Figure 10 Log In Keypad Note the Return key in the lower right corner Since the operator password is UTD simply enter those letters and press the Return key in the lower right corner of the keypad This will enable the hood software and bring up the Main screen as shown in Figure 8 DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 10 of 25 Timer Operation The two buttons on the Main screen important to hood operators are the ones entitled Cycle Timers and Neutralization Process Pressing the Cycle Timers button produces a new screen as in Figure 11 and shows the timer indicators Figure 11 Cycle Timer screen Enter time by pressing the appropriate numeral block until the desired number appears The clocks are started from the front panel on the front surface under the work area When you have the time set press Main and the system will return to the Main screen for additional actio
11. he set point of 6 0 the caustic pump is shut down and the tank pump then pumps the now neutralized fluid from the tank into the building Acid drain When the tank is empty it fills with DI water to 35 of its capacity so that any new concentrated acid poured down the sink will mix with neutral water and become dilute so that any future reaction will be slow and not so hot In any case the operator needs to know when the neutralization tank fills to or above 90 because the sink drain valve closes at this point The neutralization process by the way takes about 20 minutes in this hood DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 12 of 25 Neutralization Chemistry This section will be a short exposition of simple neutralization chemistry The purpose is to understand how the acids are neutralized and how much Sodium Hydroxide NaOH is required to neutralize a given quantity of acid This is somewhat complicated because in this general purpose hood we will be neutralizing a number of different acids with different initial concentrations The amount of base NaOH is our choice required to neutralize the acid depends on what type of acid and how concentrated it is compared to the base concentration The concept of neutralization states that the base has to supply OH ions to the solution in such numbers as to match the number of H ions that the acid has added to the solution This means that we need to kn
12. is achieved b Caustic Pump Cycle after Reaching Stage 1 Set point is currently set at 2 sec ON and 15 sec OFF After the 2 min stabilization time expires the caustic pump will use these ON OFF times to cycle pump Sodium Hydroxide until the desired pH value is achieved i e a pH of 6 0 3 Stage 3 a oH Stabilize Time After Reaching pH Set point Prior To Waste Dump is currently set at 3 min O sec This means that once a pH of 6 0 or above is achieved the system will wait for this amount of time and then pump to drain the tank b Other parameters in this menu i Recirculation Pump the caustic pump uses these parameters when neutralization is enabled The current parameters are 5 min ON 25 min OFF li pH values actual and set point are displayed in this menu DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 25 of 25
13. lp immediately contact with this much HF could be life threatening If you get a lot of HF acid on your body your buddy must call 911 to get paramedic help and be checked out by a doctor quickly More information on this situation is contained in the Clean Room Safety Handbook Tube of Calcium Gluconate Gel HF Antidote DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 9 of 25 Operating Software Overview The active hood functions are controlled by a microprocessor whose interface with the operator is the aforementioned touch screen on the control panel The control processor is concerned with two significant hood functions 1 Neutralization of the collected acid in the catch tank under the work surface and 2 general security timer temperature alarm data presentation These functions will be discussed in detail below Login From the Main screen on the touch screen there will be a soft button at the very top center of the screen entitled Log in as shown in Figure 7 The login level enables various portions of the controller capability to the operator Normally the hood will be logged in under the operator level The password for this level is currently set at UTD This level enables complete availability of all features of the hood in normal operation Figure 8 Main Screed with initial l option buttons Higher levels of the login tree enable operating parameter chan
14. manufacturer serial number i For security this number is intentionally not included in this document li Your training will include this number If only you could remember it 3 Looking at the main Menu the tab menus labeled Process Monitor Setup and Tool Setup Parameters are where all neutralization parameter are found Figure B5 Highest level Login Screen LEATHERWOOD LOGGED IN DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 23 of 25 Process Monitor Setup The process monitor option contains three set up parameters 1 pH Minimum target 2 Neutralize nn Tank Level and 3 Water Fill to kk Figure B6 shows this screen Ol WATER SUPPLY CAUSTIC NE IZATION RESERVOIR GALLON Figure B6 Neutralization Process Setup screen showing full screen Left and Pop Up window for entering data Right 1 Process Setup a pH Minimum Target i Select the numeric box by touching it This will bring up a pop up window enabling you to enter the minimum pH value that must be achieved at the conclusion of the neutralization process This number is currently set at 6 0 b Close sink valve nn Tank Level i Selecting this box will bring up the same keypad pop up window where you can enter the level at which the sink valve will close This number is currently set at 90 c Water Fill to kk Tank Level i Selecting this box will also bring up that familiar pop up numeric keypad all
15. n The timers are started and stopped from the front panel below the work surface as indicated in Figure 1 This screen also shows the liquid in beaker thermocouple thermometer temperature Neutralization System The screen view most useful for standard operations is the Neutralization screen This is a somewhat complicated depiction of the hood s drain plumbing and neutralization pumping and valving system Figure 12 shows this screen DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 11 of 25 occep in NEUTRALIZATION PROCESS J pr wa DI WATER SUPPLY WATER FILL V1 5 WATER FILL SP 35 MAIN NEUTRALIZATION RESERVOIR TANK 15 GALLON Figure 12 Neutralization process screen showing the hood s drain plumbing and valving configuration along with the neutralization tank and pumping plumbing The reason that this screen is informative is that when the Neutralization Tank is filled to about 90 of capacity with fluid the software closes the Sink valve and therefore the hood operator cannot drain any more fluid into the tank After the valve closes the Neutralization process starts This involves recirculating the fluid in the Neutralization Tank to stir the mixture and then pulsing the Caustic Reservoir pump to neutralize the acid in the tank by small spurts of caustic The pH of the tank fluid is constantly measured and when the neutralization process brings the pH above t
16. nk is full the neutralized solution is pumped into the building acid drain There are two pumps involved with this system 1 a recirculating pump used to stir the fluid Figure 7 Catch tank Right and Caustic in the tank and 2 a caustic pump to Reservoir Left under the hood deliver the Sodium Hydroxide Both of these pumps are diaphragm pumps that make a noticeable clacking sound from behind the hood this is normal N Gun and DI Water Spray The hood has the standard Nitrogen blow off gun and DI water spray hose to facilitate drying and water rinsing of substrates Note that the DI water hose is made of coaxial Teflon tubing and is somewhat stiff to stretch and it will spring back with considerable force if it slips out of your hands be careful and get a good grip Figure 1 shows the recessed location of both these hood tools HF Acid Antidote There should always be a supply of Hydrofluoric Acid HF antidote in plastic tubes in the back of the hood work surface If you accidentally get HF on your skin wash it off with DI water for about 10 minutes and then apply the antidote creme by rubbing it into the skin for about 5 minutes This Calcium Gluconate antidote will react with the HF to create benign Calcium Fluoride salt thus capturing the F ions that can do serious damage to the body If a large spill gets on you then remove clothing and do a 15 minute shower in the emergency shower at the entrance to the room Call for he
17. ntrol Panel ETT Hotplate Touch Screen ees O re Si Sew Acid Sink DI Water Gun Exhaust Pressure 2s a N2 Gun Gauge Process Timers Start 8 Stop Buttons Figure 1 Illustration of 4 ft Acid Hood features Feature Details Control Panel The control panel is shown in Figure 2 with labels This panel is composed of two segments 1 a section of actuator buttons and indicator lights and 2 a touch screen linked to a microprocessor for controlling the operation of the hood These will be described in detail in the following sections DI Water The hood has a recirculating de ionized water plumbing system to prevent stagnant water from growing microorganisms and contaminating the purity of the water There is a monitor readout of this condition at the top of the control panel that displays the resistivity of the water in meg ohms The nominal value of good DI water is 18 1 meg ohms or better If you notice that the value has slipped below the 17 meg ohm level please notify the clean room staff and if this would impact your work discontinue processing your work in this hood DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 5 of 25 DI Water Condition Meter Meg Ohms Loss of Exhaust Indicator Light Hood Start Button Audio Alarm Enunciator Emergency OFF Button Alarm Silence Button Hood Power off Button Figure 2 Hood Control Panel details Figure
18. ood is HAQ1 means Hood Acid 1 e The Neutralization Process must be ENABLED on the touch screen Neutralization Introduction This acid hood HA01 has an onboard acid neutralization system located under the work deck Acid waste dumped in the DI Water Acid sink will drain into a 15 gallon neutralization tank and when the tank level reaches 90 full 13 5 gal the pneumatic valve below the sink will close If the neutralization process is ENABLED and the liquid in the neutralization tank has a pH lower than 6 0 a 50 solution of NaOH Sodium Hydroxide will be pumped into the tank from a smaller 2 gallon caustic reservoir until the OH is equal to or greater than 6 0 At this point the liquid in the neutralization tank will be recirculated stirred for a programmed specific time period and then pumped to the building acid drain When the tank level drops to 5 or less the drain cycle will cease and new DI water will fill the tank to 35 5 25 gal recirculate for 3 minutes and then the DI Water Acid sink valve will open At this point the hood can be used again Neutralization Procedure 1 Once logged in from the main menu you can access the neutralization menu by selecting NEUTRALIZATION PROCESS Figure B1 Login Figure B1 Sequence of screens to enable login Select Neutralization Resulting the screen DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 20 of 25 E
19. ow what the reaction equation looks like and what the oxidation number is for the reactants In fact we need to recall a number of chemical definitions to be able to calculate the volumes of the constituents involved in the neutralization Chemical Definitions Mole One Mole of a substance is its collective molecular weight expressed in grams formula weight EX H250 2x1 1x32 4x16 gt 98gm Red numbers are atomic masses and multipliers are the number of times the atom appears in the molecule Gram Equivalent Weight One gram equivalent weight E of a substance is its gram atomic weight divided by its oxidation number EX HSO 2x1 1x32 4x16 2 gt E 49gm eq Red numbers are atomic masses multipliers are the number of times the atom appears in the molecule and the Blue 2 is the oxidation number of the sulfate ion SO in the sulfuric acid molecule reacting with NaOH DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 13 of 25 Normality In order to calculate the quantities involved in a chemical solution reaction we need some measure of the concentration of the chemical in its solvent water The most convenient expression of this for calculating neutralization reactions is the Normality value Normality N is defined as the number of gram equivalent weights of a substance per liter of solution N gram equivalent weights liters of solution gt N E V Note
20. owing you to enter the fill level of the tank after the drain cycle This number is currently set at 35 This level insures that the pH sensor is continuously wetted Caustic Pump Setup This setup procedure is hidden behind the TOOL SETUP PARAMETERS button on the main screen of Figure B5 After pressing this button a screen will popup showing the thermocouple calibration setup Pressing the NEXT button will then bring up the CAUSTIC PUMP SETUP screen There are several sections of this screen called Stages that describe parameters in sequence in the neutralization process DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 24 of 25 Figure B7 Caustic Pump Setup Screen displays by touching the NEXT button from the Left screen that popped up when you hit the TOOL SETUP PARAMETERS button on the MAIN screen Figure B5 1 Stage 1 a Caustic Pump RUN Constantly Below n n pH This means that the caustic pump will supply Sodium Hydroxide continuously if the actual pH of the tank contents is less than n n Currently this number is set at 1 0 2 Stage 2 a The button labeled pH Stabilize Time After Reaching Stage 1 Prior to pH Set point allows a time input that sets the amount of time that the system will wait after reaching a pH of n n 1 0 before it moves on to stage 3 If in this wait time the pH falls below n n 1 0 it will again pump Sodium Hydroxide continuously until n n 1 0 or higher
21. s in Red Nominally this calculator is designed to tell how much sodium hydroxide is required to neutralize a given volume of acid Thus just fill in the volume of the acid and the chart will fill in the required sodium hydroxide volume in red Units are Liters 1 Gal 3 7854 Liters 1 Liter 0 264 Gal Liq Wt NaOH Vol PAS Oxidation Formula Volume Density Concen L req for Reactants Sumber Wt o gm mL a Normality o wH 153 19 125 a mo eee a ETE HPO 3 os 1 17 85 4 284694 231292517 CHCOOH 1 60 1 1048 98 17 117333 0 89502397 Double click in the chart Excel will open and allow input and auto calculation Rules of Operation For safety sake we have generated a set of rules to apply to operators of this hood They are listed below e When first approaching the hood to start work please notice the conditions in the hood and note any situational dangers Either correct them or notify Clean Room Staff e Work with a BUDDY e Stay in the Clean Room when heating stuff on the Hot Plate e Wear appropriate Personal Protective Equipment o Double gloves standard CR gloves with acid gloves over them o Safety glasses o Acid apron o Face shield o Solid top shoes e Fill out chemical use form o Name Buddy Name o Date o Phone number o Chemicals in use DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 15 of 25 Only one experiment at a
22. se this button If you have had to push the EMO button please notify Clean Room Staff immediately Audio Enunciator The audio enunciator is a piezoelectric beeper that announces either a non emergency fault or the completion of a timed event There is a convenient yellow alarm silencer button which you can use to cause immediate cessation of the annoying beeps However please make sure that the cause of this alarm is corrected before leaving the hood Notify Clean Room staff if necessary Touch Screen OPERATOR LOGGED IM The Touch Screen is the user interface for the microprocessor controller for the hood This controller has a password and multiple display screens for ron le Ji monitoring and controlling the hood This Pa i is where the acid dump catch tank is monitored and dilution and neutralization parameters are set This will be discussed in the control section later in the document SINK sil DI WATER ail US TI NEUTRALIZATION Ae TANK 15 GALLON Figure 4 Touch Screen DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 7 of 25 Process Features Hotplate The hotplate shown in Figure 5 is a simple manual stirring hotplate with local controls located under the removable panel just in front of the hotplate There is a protective skirt around the hotplate heating surface to protect the hotplate from accidental spills into the sunken hotplate recess The local con
23. sink with a gooseneck faucet an explosion proof hotplate a Dl water spray gun a Nitrogen blow off gun and a flexible thermocouple thermometer for measuring the temperature of liquids on the hotplate The hood is controlled by a solid state controller with a touch screen control panel There are two process timers on the front panel below the work surface Sink timer and Hotplate timer Alarms are handled by the upper portion of the left hand side control panel The Big Red emergency off button is also located prominently on this panel Exhaust is monitored by a Photohelic differential pressure gauge on the left side of the front panel below deck level Under the hood is a chemical tank used to actively neutralize acids from the sink This is an automatic neutralization system that measures the pH of the liquid in the tank and when the level rises to 90 of the tank capacity the system will pump Sodium Hydroxide into the tank to neutralize the acid mix When the pH is stable above 6 0 the system will pump the contents of the tank into the acid drain of the building At the conclusion of this operation the tank refills to 35 of its capacity with DI water to act as a dilution agent for acids poured down the drain thus reducing the localized heating from the heat of mixing Figure 1 illustrates the features discussed in this paragraph DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 4 of 25 Co
24. that since this definition involves the oxidation number of a substance N can vary depending on the exact chemical reaction it is involved in Density This is defined as the simple physical quantity of weight per volume gm ml Concentration Concentration of a chemical in a water solution is expressed as the percentage by mass of a substance per mass of the total solution e 49 HF in water EX 49 by wt of HF in 1000gm solution gt 49x1000gm 490 gm of HF in 1000 gm of solution Chemical Calculations Calculating how much sodium hydroxide one needs to neutralize some amount of acid is explained in detail in Appendix A However to make things a bit easier have included an imbedded EXCEL table with the formulas already included so that you can find the answer to the above question by inputting the starting parameters in a table and puff the answers appear in the last column Table 1 below includes the standard chemicals used in the acid hood and calculates the amount of NaOH required to neutralize the acids If you have a mix of acids then calculate the volume of NaOH required for one acid and add the NaOH amount from the next independent acid reaction DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 14 of 25 Table 1 Acid Neutralization Calculation Chart Sodium Hydroxide Acid Neutralization Calculator 11 17 2006 RAR Calculator instructions Input numbers in Blue Read answer
25. trol knobs set the temperature and control the stirring magnet speed As labeled in Figure 1 the hood has a flexible Thermocouple Thermometer to measure the temperature of liquids ina container sitting on the hot plate The Figure 5 Hotplate showing splash skirt and temperature is indicated on the touch cover for hotplate control knobs screen Sink The DI water is delivered to the sink through a gooseneck faucet that has recirculating DI water all the way to the valve This insures that the water will not have a stagnant line that can grow microorganisms which may contaminate your substrate As subtly mentioned above this sink will accept all waste acid thus removing the dangerous liabilities to health associated with saving individual containers of acids and handling them through a manual waste disposal system When acids are disposed of in this sink a moderate amount of DI water should be used to clear out any puddles of concentrated acid in the drain lines Figure 6 DI water sink accepts waste acids for neutralization DOCUMENT TITLE Acid Hood Operations 6 2 2006 AUTHOR Roger Robbins Arnold Duenes Page 8 of 25 Acid Neutralization Tank When fluids drain out of the sink they drain directly into a catch tank under the hood This tank has an active neutralization system that measures the pH and supplies a 50 concentrated Sodium Hydroxide solution to the tank in a programmed cycle to neutralize the acid When the ta
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