Exercise 1-1. Familiarization with the Training System EXERCISE OBJECTIVES

Transcription

1 Exercise 1-1 Familiarization with the Training System EXERCISE OBJECTIVES To familiarize yourself with the Process Control Training System; To set up and operate a basic flow circuit; To identify the potential hazards associated with chemicals using the information on the chemical bottles; To understand the information provided in the MSDS; To learn and follow all the laboratory safety rules. DISCUSSION To proceed with the ph Process Control exercises, material from the Pressure, Flow, and Level Process Control, Model , is required. Please refer to the Lab-Volt Student Manual entitled Pressure, Flow, and Level Process Control (P/N ), for a complete description of the Process Control Training System components. ph Process Control components Metering Pump The Metering Pump provides either a continuous or pulsed flow of chemical solution into the Column. The Metering Pump shown in Figure 1-4, consists of a miniature gear pump. Figure 1-4. Metering Pump. 1-11

2 : DC line cord : Metering pump : Non-spill coupling : Inlet : Outlet The solution is pumped from the Chemical Tank to the Column through 0.48-mm (0.188-in) tubing. When connected to the Metering Pump Drive, the Metering Pump can provide a maximum flow rate of 1.8 l/min (0.48 gpm). There are two modes of operation for the Metering Pump: the continuous mode or the pulsed mode. The last allows the addition of solution into the Column one drop at a time. Up to three 12-V dc Metering Pumps can be powered using the Metering Pump Drive. Chemical Tank The Chemical Tank consists of a 2-l (0.53 gal) capacity, low-density polyethylene carboys. The Chemical Tank has a small length of tubing terminated with a non-spill coupling. The screw cap is equipped with a check valve letting air into the tank while preventing chemical to flow out. Figure 1-5. Chemical Tank. : Check valve : 2-liter bottle (0.53 gal) : Non-spill coupling 1-12

3 Metering Pump Drive Figure 1-6. Metering Pump Drive. The following is a detailed description of the Metering Pump Drive terminals and adjustments (refer to Figure 1-6): 0-5 V and 4-20 ma INPUTS terminals: receive a voltage or a current signal and send a voltage proportional to this signal to the Metering Pump. The S selector switch must be in position 1 in order to use the input signal to modulate the voltage sent to the Metering Pump. S1, S3, and S5 input selectors: set the source signal used to modulate the speed of the corresponding Metering Pump. When the switch is in position 1, the Metering Pump Drive will adjust the corresponding output voltage sent to the Metering Pump proportionally to the input signal received in. When the switch is in position 2, the corresponding output voltage sent to the Metering Pump will be proportional to the position of the SC1, SC2, or SC3 speed adjustment knobs. SC1, SC2, and SC3 adjustment knobs: used in the manual control mode to set the speed of the Metering Pumps. S2, S4, and S6 mode selectors: allow to set the output signal for operation of the Metering Pumps in continuous or pulsed mode. 1-13

4 Pulse width adjustment knobs: used in the manual control mode to adjust the width of the square wave signal sent to the Metering Pumps. SC1, SC2, and SC3 outputs: provide a voltage proportional to the signal received at the 0-5 V or 4-20 ma INPUT terminals if the corresponding "S" input switch is in position 1. Or provide a voltage proportional to the position of the SC1, SC2, and SC3 adjustment knobs if the corresponding S switch is in position 2. ph Process Control setup Figure 1-7 and 1-8 show a typical ph Process Control setup without any electrical leads, tubing, or hoses. To avoid chemicals to be spilled, the Expanding Work Surface (Large), Model 6302, should be tightly secured on the Work Surface, Model 6301, using the push-lock fasteners. The Expanding Work Surface (Large) should make an angle of 90 with the Work Surface. To avoid liquid coming in contact with the electrical equipment, electrical devices should be placed as far as possible from the Column and the Chemical Tanks. It is strongly recommended that they be placed on the right side of the work surface and behind the Expanding Work Surface (Large) as illustrated in Figure 1-7 and Figure

5 Figure 1-7. Front view of a typical ph Process Control setup. : Chemical Tank : Column : Expanding Work Surface (Large) : Flow Chamber : Work Surface : Metering Pump : Tray : Metering Pump Drive : ph Transmitter : I/O Interface 1-15

6 Figure 1-8. Rear view of a typical ph Process Control setup. : ph Transmitter : I/O Interface : DC Power Supply Figure 1-9 shows a typical ph Process Control setup with tubing and hoses. Always make sure that everything is properly connected before turning on the Pumping Unit. The tubing used to connect the Chemical Tanks to the Column are equipped with quick connect couplings that shut off the liquid flow upon disconnection. Only the female connectors of the hoses on the Pumping Unit, Model 6510, are equipped with check valves that stop the liquid flow upon disconnection. No such valves are installed on the male connectors on the Column, Model Precautions must be taken to make sure the Column and hoses are fully drained before disconnecting the hoses. The port to be used to insert the ph probe is located at the top of the Flow Chamber. To avoid liquid flowing out of the mounting assembly, the ph probe should be properly inserted into the Flow Chamber before using the system. 1-16

7 Figure 1-9. A typical ph Process Control setup with tubing. ph Process Control Consumables Several chemical products are supplied in the ph Process Control Consumables, Model Before using any of the products supplied with the Process Control System, read the Material Safety Data Sheets (MSDS) provided in Appendix L carefully and analyze the labels of each product. 1-17

8 Security issues Labels Bottles of chemical products are strictly labeled. Each label is divided into two sections. The first section has a hatched border and contains the following information: product identifier, hazard symbols, warnings, precautions, first aid procedure, and a statement that an MSDS is available. Figure 1-10 shows the hazard symbols commonly used on hazardous material labels. Figure Hazardous material symbols. 1-18

9 The second section, without a hatched border, contains: icons identifying the required Personal Protective Equipment (PPE), the National Fire Protection Association (NFPA) diamond shaped symbol, a storage color code, and miscellaneous information about the product (name, quantity, chemical formula, concentration, etc). Figure 1-11 shows a typical hazardous material label. Figure Label. Figure 1-12 shows the Exposure Controls / PPE icons commonly used on chemical product labels. For more detailed information about the practices and equipment required when using a given chemical product, refer to its MSDS. 1-19

10 Figure PPE icons. The four-color diamond (square-on-point) shaped symbol has been developed by the National Fire Protection Association to quickly provide information related to hazards of a material. It is divided into four color-coded sections. Three of these sections contain a number from 0 to 4 identifying the degree of hazard, four (4) indicating severe hazard and zero (0) minimal hazard. The fourth section warns against unusual reactivity with water (W) and strong oxidizer substance (OX). 1-20

11 Figure NFPA symbol. HAZARD COLOR HAZARD SEVERITY DESCRIPTION 4 Substance that could cause death or major residual injury even with small exposure. This includes rubber penetrating substance and materials which produce highly toxic/corrosive gases that can be absorbed by skin or through inhalation. Health Blue 3 Substance that could cause serious injury upon brief exposure. This includes highly corrosive material upon contact or material producing highly toxic substances upon combustion. 2 Substance that could cause temporary or residual injury through intense or continued exposure unless the appropriate medical attention is provided. This includes material producing toxic substances upon combustion. 1 Substance that could cause minor irritation or residual injury upon skin contact or inhalation. 0 No or minimal hazard. Table 1-2. NFPA 704 rating system. 1-21

12 HAZARD COLOR HAZARD SEVERITY DESCRIPTION 4 Substance that will vaporize rapidly or completely at normal pressure and temperature and will burn readily. This includes gases or liquids having a flash point below 22.8 C (73 F) and a boiling point below 37.8 C (100 F). Flammability Red 3 Liquids and solids that can be ignited under almost all ambient conditions. This includes liquids having a flash point below 22.8 C (73 F) and a boiling point above 37.8 C (100 F) or liquids having a flash point between 22.8 C (73 F) and 37.8 C (100 F). 2 Substance that will produce flammable vapors if moderately heated or under high ambient temperatures. This includes substances with a flash point between 37.8 C (100 F) and 93.4 C (200 F). 1 Substance that must be considerably preheated before ignition can occur. This includes substances with a flash point above 93.4 C (200 F). 0 Substances that will not burn. 4 Substance that will readily explode at ambient temperatures. This includes substances sensitive to mechanical or localized thermal shock. 3 Substance that could explode at ambient temperature, given a strong initiating source. Reactivity Yellow 2 Normally unstable substance. This includes substances that can undergo violent chemical change and substances that react with water. 1 Normally stable substance that may react lightly with water or at elevated temperatures (or pressures). 0 Normally stable substance. Special White W OX Substance that will react violently with water. Strong oxidizing agent. Table 1-2. NFPA 704 rating system (cont'd). Note: The flash point is the lowest temperature at which the vapors produced by a substance are present in ambient air in sufficient concentration to ignite if an ignition source is present. 1-22

13 A storage color code is also present on the label. Table 1-3 briefly describes each color code. COLOR CODE Red Yellow Blue White Grey DESCRIPTION The product is flammable and/or combustible and it should be stored separately. The product is strongly reactive and/or a strong oxidizing agent and it should be stored away from products with a red storage code. The product presents important health hazards and it should be stored in a secure area. The product is corrosive and it should be stored away from products with a red, yellow, or blue storage code. The product presents no storage hazard. The general procedure used to store chemical products should be used. Table 1-3. Storage color code description. The Material Safety Data Sheet (MSDS) Manufacturers must provide an MSDS for all chemical substances they produce. The MSDS is divided into 16 sections, each of them providing essential information on the substance. Section 1 Product and Company Information: Clearly identifies the product and the manufacturer. An emergency phone number should be present in this section. Section 2 Composition/Information on Ingredient: Lists the hazardous ingredients present in the product. The CAS registry number of each hazardous ingredient should be present along with its concentration. Other information may be present such as chemical formulas and miscellaneous identification numbers. Note: CAS is an acronym for Chemical Abstracts Service, a division of the American Chemical Society. The CAS registry contains over 27 million entries, and thousands of substances are added weekly. Section 3 Hazards Identification: Lists the potential health effects, their symptoms, the degree of severity of the effects in case of exposure, the potential routes of entry into the body, and the target organs. This section is usually written in a straightforward style making it easy to find the required information quickly in case of emergency. Section 4 First Aid Measures: Gives easy-to-understand first aid procedures to be followed for each route of entry (eyes, skin, inhalation, ingestion). Additional notes to a physician may be presented in this section to help treatment in case of overexposure. Section 5 Fire Fighting Measures: Provides essential information about the flammability and explosive properties of the substance. Fire-fighting instructions are also provided in this section. Section 6 Accidental Release Measures: Describes action to be taken in case of accidental leak or spill. 1-23

14 Section 7 Handling and Storage: Discusses the general precautions to safely handle and store the product. Section 8 Exposure Controls / PPE: Provides the applicable control measures for the product and the personal protective equipment required to minimize risk of overexposure. Section 9 Physical/Chemical Properties: Lists the physical and chemical properties of the substance. Appearance, odor, physical state, ph, vapor pressure and reference temperature, vapor density, boiling point, freezing/melting point, specific gravity or density, evaporation rate, partition coefficient, odor threshold, viscosity, and solubility in water. Section 10 Stability and Reactivity: Indicates the stability of the substance and the conditions to be avoided to prevent dangerous changes in the substance stability. If the product can react violently in the presence of other chemicals, it should be mentioned in this section. Section 11 Toxicological Information: Provides the background toxicological information about the product and its compounds. Section 12 Ecological Information: Discusses the environmental impact the substance may have if released into the environment. Section 13 Disposal Considerations: Describes how to safely dispose of the substance. Section 14 Transport Information: Gives the basic shipping information such as if a specific transportation label is needed. Section 15 Regulatory Information: Provides miscellaneous information on the regulation under which the product falls. Section 16 Other Information: Provides additional information. Essential information to look for on labels and in MSDS The label and MSDS of chemical substances contain a lot of information. It is essential to be able to synthesize the information and keep in mind the essential points when using a hazardous substance. 1-24

15 Table 1-4 lists the primary concerns you should have before using a chemical product. QUESTION TO ANSWER BEFORE USING A CHEMICAL PRODUCT What are the hazards associated with this product? What are the PPE required to manipulate this product? What is the first aid procedure in case of exposure? WHERE AN ANSWER COULD BE FOUND Label: In the section within the hatched border. Label: The NFPA symbol. MSDS: section 3 - Hazards identification. Label: PPE icons in the left section of the label. MSDS: section 8 - Exposure Controls / PPE. Label: In the section within the hatched border. MSDS: section 4 - First Aid Measure. Is the product flammable or explosive? Label: In the section within the hatched border. Label: The NFPA symbol. MSDS: section 5 - Fire Fighting Measures Could the product react violently in some conditions? Label: In the section within the hatched border. Label: The NFPA symbol. MSDS: section 10 - Stability and Reactivity. Table 1-4. Questions to answer before using a chemical product. Basic laboratory safety rules Whenever working with hazardous substances, whether it is in a laboratory or in an industrial environment, the basic safety rules presented below must be followed: The appropriate PPE (chemical splash goggles, gloves, laboratory coat, etc.) should be worn at all times. Do not eat, drink, smoke, apply cosmetics, or do anything that can get your eyes or mouth in contact with hazardous material. Never drink out of the laboratory glassware. Even when it has been thoroughly washed, glassware can retain toxic chemicals. Make sure to know the location of emergency equipment and how to use it. Eyewash, safety shower, first aid kit, and firefighting equipment should be available in your laboratory. Report immediately any incidents or defective material to your instructor. Remove all PPE before leaving the laboratory. Do not wear gloves while typing on the computer. Avoid distracting other students. 1-25

16 Wash your hands frequently. Especially when leaving the laboratory or before eating. When an exercise is completed, wash the glassware and return all components to their storage location. When working with a particular chemical, make sure to know the emergency procedure. Have the MSDS and an emergency phone number at hand. Label all your solutions to avoid mix up. Never pour water into acid. Always pour acid into water. Never mix a concentrated acid with a concentrated base. The resulting reaction could be violent. Never inhale or directly smell chemicals. Whenever you are manipulating hazardous material, keep in mind the axiom: "Better safe than sorry." Procedure summary In this exercise, you will be introduced to the basic laboratory safety rules that must be followed when manipulating chemicals. You will also familiarize yourself with the components of the Process Control Training System that are used for the measurement and control of ph. EQUIPMENT REQUIRED Refer to the Equipment Utilization Chart in Appendix A of the manual to obtain the list of equipment required to perform this exercise. PROCEDURE Safety considerations WARNING! Chemical product(s) used in this exercise may present health hazards. Carefully read the label(s) and MSDS before use. Wear the appropriate PPE. G 1. The first concern when working with chemical products is safety. Get the chemical products provided with the Process Control Training System from your storage location and place them on the Work Surface. Table 1-5 lists the chemical products you should have. 1-26

17 CHEMICAL PRODUCT Acetic Acid 5% (Vinegar) Buffer Solution ph 4.0 Buffer Solution ph 7.0 Buffer Solution ph 10.0 Hydrochloric Acid Solution 1.0 N Phenol Red Aqueous solution 0.05% Phosphoric Acid 1.0 N Solution Potassium Chloride Solution Sodium bicarbonate (Baking Soda) Sodium Hydroxide Standard Solution 1.0 N Table 1-5. Chemical products from the ph Process Control Consumables. G 2. Carefully read the label and MSDS of each product. Note: Acetic acid and sodium bicarbonate have no MSDS since they are household products. G 3. What is PPE? G 4. Should PPE be used when manipulating the products listed in Table 1-5? If yes, which type of PPE should be used? G 5. Which of the products among those listed in Table 1-5 are corrosive? G 6. What should you do if a corrosive product comes in contact with your eyes or skin? 1-27

18 G 7. Wearing prescription glasses offers sufficient eye protection when working with chemical products. G True G False G 8. Which product listed in Table 1-5 can be ignited under ambient conditions? ph Process Control Accessories G 9. Familiarization with the ph Process Control Accessories is essential to successfully complete the exercises of the Process Control Training System. Figure 1-14 shows some of the accessories provided with the trainer. Figure ph Process Control Accessories. 1-28

19 Making a dilute acetic acid solution Note: Use the Physical Constants table of Appendix C to answer the following question. G 10. What is the molarity of the acetic acid solution provided with the training system, assuming that its concentration in acetic acid is 5% (v/v)? G 11. Using the 100-ml graduated cylinder, measure 184 ml of Acetic Acid 5% (vinegar). Make sure to place the graduated cylinder on a horizontal surface. If necessary, use a funnel to pour Acetic Acid 5% into the graduated cylinder. Always read the liquid level at the bottom of the meniscus as illustrated in Figure 1-15 (First measure 100-ml, place it in a beaker, then measure another 84-ml). Note: The meniscus is the curved surface formed at the top of a column of liquid. In the case of aqueous solutions, the meniscus is concave. The formation of a meniscus is the consequence of the polar nature of water molecules, which means that the electric charge of a water molecule is not uniformly distributed (i.e., the molecule has positively and negatively charged ends). Polar molecules attract each other. Since molecules forming glass and plastic are polar too, water is attracted by the sides of the container. 1-29

20 Figure Measure the level of liquid at the bottom of the meniscus. G 12. Half fill the volumetric flask with water. G 13. Pour the 184 ml of acetic acid into the volumetric flask. G 14. Add water into the volumetric flask until it almost reaches the etched mark on the neck. Use a pipette to add water until the bottom of the meniscus reaches the mark. The flask is now filled with 2000 ml of dilute acetic acid solution. G 15. Use the following equation to calculate the concentration of the dilute acetic acid solution in the flask: where C i is the concentration of the initial solution in mol/l V i is the volume of the initial solution C f is the concentration of the final solution in mol/l is the volume of the dilute solution V f The concentration of the dilute acetic acid solution is: mol/l. 1-30

21 G 16. Safely discard the dilute acetic acid solution. The Metering Pump Drive G 17. Examine the Metering Pump Drive, Model This device is used to control the Metering Pumps, Model The pumps are used to add reactants to the Column, permitting the adjustment of the ph of the solution. Control knobs on the Metering Pump Drive can be used to manually control the speed of each Metering Pump. The pumps can also be controlled with the Process Control and Simulation Software (LVPROSIM), Model 3674, when the Metering Pump Drive is connected to a computer via the I/O Interface, Model The Metering Pump Drive front panel is divided into three sections, each of these controls one Metering Pump. Draw below the I.S.A. instrumentation symbol representing one of these sections, as silkscreened on the Metering Pump Drive. CAUTION! Do not let the Metering Pumps run dry. Failure to prevent this might damage the pumps. G 18. Two control modes are available on the Metering Pump Drive: continuous and pulsed. Which of them is more suitable for titration? Why? The ph probe and the ph Transmitter G 19. Examine the ph probe and the ph Transmitter. These devices are intended to be used conjointly to measure the ph of the solution flowing through Flow Chamber. When connected to the ph PROBE input of the ph Transmitter, the ph probe provides the transmitter with an electrical signal proportional to the ph of the measured solution. The transmitter converts this signal into a voltage and a current of normalized range that are available at the transmitter 0-5 V and 4-20 ma OUTPUTS. The transmitter also has a calibrated output, labeled "CAL.", that provides a fixed voltage of 1 V per sensed ph unit above

22 G 20. Power up the ph Transmitter. To do so, connect the POWER INPUT terminals of the transmitter to the 24-V DC Power Supply. G 21. Connect the ph probe to the ph PROBE input of the ph Transmitter. G 22. On the ph Transmitter, set the INPUT SELECTOR switch at ph PROBE and connect a dc voltmeter to the CAL. output of the ph Transmitter. G 23. Take the ph probe out of the Flow Chamber used for storage, and immerse its tip in a beaker full of water. G 24. According to the voltmeter reading, what is the ph of the water? G 25. Pour about 30 ml of Buffer Solution ph 10.0 in a 100-ml beaker and immerse the tip of the ph probe in the solution. The buffer solution should have a ph value of Is this your observation? G Yes G No ph Process Control setup G 26. Use Figure 1-7 to 1-9 and connection diagram B-1 of Appendix B to build a typical ph Process Control setup. Filling the Column with water CAUTION! To avoid water and chemical spills all over the Process Control Training System, make sure the ph probe is properly inserted into the port at the top of the Flow Chamber before starting the Pumping Unit. G 27. Once the equipment is set up as required, fill the Pumping Unit with approximately 12 liters (3.2 gallons) of water. Fill the two Chemical Tanks with water. CAUTION! Always make sure the reservoir of the Pumping Unit is filled with the proper amount of water (12 l/3.2 gal US) before turning on the Pumping Unit. Failure to do so might cause the pump to run dry, causing the pump seal to overheat and wear out prematurely. 1-32

23 Note: For more details on the operation of the Pumping Unit, refer to unit 1 of the Lab-Volt Student Manual entitled Pressure, Flow, and Level Process Control (P/N ). G 28. Turn on the Pumping Unit by setting its POWER switch at I. G 29. On the Pumping Unit, adjust valves HV1 to HV3 as follows: close HV1 completely (turn handle fully clockwise); close HV2 completely (turn handle fully clockwise); set HV3 for directing the full reservoir flow to the pump inlet (turn handle fully clockwise). G 30. Connect the Set Point Device to the Pumping Unit as shown in the connection diagram B-1 of Appendix B. Adjust the pump speed to 60-70% of its maximum by setting the Set Point Device output between 3.00 V and 3.50 V. Note: Use a voltmeter to adjust the Set Point Device output using the adjustment knob. G 31. Allow the level of water to rise in the Column until it reaches 38 cm (15 in). CAUTION! Be careful, the water level in the Column can rise quite rapidly. If you are not familiar with the Pumping Unit, set the pump speed lower. Placing the system in recirculating mode G 32. Once the proper water level is reached, rapidly adjust HV3 to stop the water flow from the reservoir and direct the full return flow to the pump inlet (turn the handle fully counterclockwise). G 33. On the Pumping Unit, open HV2 and let the water level in the Column decrease to 15 cm (6 in). As soon as the water reaches the proper level, close HV2. G 34. The Column is now in recirculating mode. Water is pumped to the Pumping Unit outlet, passes through the Flow Chamber, goes into the Column, and flows out of the Column through one of the bottom outlets to be directed to the pump inlet again. G 35. Make sure the two Chemical Tanks are filled with water. 1-33

24 G 36. Turn on the Metering Pump Drive. G 37. Set input selectors S1 and S3 at position 2. This allows manual control of the speed of the Metering Pumps. G 38. Set switches S2 and S4 to the continuous mode. G 39. Use the SC1 and SC2 speed adjustment knobs to adjust the speed of the Metering Pumps until a thin flow of water comes out of each inlet at the top of the Column. G 40. Set switches S2 and S4 to the pulsed mode and try various pulse widths. G 41. Try to set the pulse width so that water falls into the Column one drop at a time. G 42. In the pulsed mode, the frequency can be adjusted using the SC1 and SC2 speed adjustment knobs. G 43. Stop the Metering Pumps and turn off the Metering Pump Drive. G 44. Stop the variable-speed drive of the Pumping Unit by setting the Set Point Device output to 0.00 V. G 45. Open valve HV1 of the Pumping Unit completely and let the water in the Column drain back to the reservoir. G 46. Turn off the Pumping Unit and the 24-V DC Power Supply by setting their POWER switch at O. G 47. Disconnect the hoses of the Pumping Unit from the system and safely dispose of the solution in the reservoir. CAUTION! Before disposing of the reservoir contents, always neutralize the solution to avoid acid or alkaline products from being released into the environment. After neutralization, only water and salts should remain in the reservoir. Refer to the neutralization procedure in Appendix I for details. 1-34

25 G 48. Disconnect the system. Return all leads, hoses, and components to their storage location. CAUTION! Water may remain in the hoses and components. Be careful not to allow water to enter the electrical components and their terminals upon disconnection of the hoses. G 49. Thoroughly wash the glassware. G 50. Store the ph probe in the flow chamber filled with storage solution. Refer to Appendix K for details. G 51. Wipe up any water from the floor and the Process Control Training System. G 52. Remove and dispose of your protection gloves before leaving the classroom. Carefully wash your hands. CONCLUSION In this exercise, you familiarized yourself with the components of the Process Control Training System that are used to measure and control ph. You learned how to operate a basic flow circuit. You also learned to identify the hazards associated with chemicals and how to avoid accidents by following the basic laboratory safety rules. REVIEW QUESTIONS 1. What does ph measure? 2. Explain the difference between an acid and a base. 3. Should you add 10 ml of water to a 500-ml beaker full of concentrated sulfuric acid? 1-35

26 4. At neutrality, is the concentration of H 3 O + is equal to zero? Mathematically prove your answer. 5. How much Hydrochloric Acid Solution 1.0 N and how much water is required to make 2000 ml of Hydrochloric Acid Solution with a concentration of 0.08 mol/l? 1-36