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Metal Samples MS2500L Operator's Manual

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MS2500L Transmitter
Operator's Manual
Metal Samples Company
A Division of Alabama Specialty Products, Inc.
152 Metal Samples Rd., Munford, AL 36268 Phone: (256) 358-4202 Fax: (256) 358-4515
E-mail: msc@alspi.com Internet: www.metalsamples.com

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  • Page 1 MS2500L Transmitter Operator’s Manual Metal Samples Company A Division of Alabama Specialty Products, Inc. 152 Metal Samples Rd., Munford, AL 36268 Phone: (256) 358-4202 Fax: (256) 358-4515 E-mail: msc@alspi.com Internet: www.metalsamples.com...

  • Page 3: Table Of Contents

    C. Modes of Operation ....................3 D. Specifications ......................4 E. Summary ........................5 II. Installation Procedures ....................... 6 A. MS2500L Transmitter Mounting .................. 6 B. MS2510 Receiver Installation ..................6 III. Operation ........................7 A. Cycle Time Predetermination ..................7 IV.
  • Page 4 VII. Instrument Testing and Repair ................... 23 A. Recommended Test Equipment ................23 B. Board Removal ..................... 23 C. Electrostatic Shield Removal .................. 23 D. Visual Inspection ....................24 E. Electrical Testing ....................24 VIII. Current Loop Operation and Testing ................28 A.

  • Page 5: Introduction

    I. Introduction A. General Description The MS2500L corrosion rate transmitter is a two-wire, 4-20mA current loop transmitter for corrosion measurements using the three-electrode, linear polarization technique (LPR). Functionally, the MS2500L transmitter operates under the same principles as the automatic LPR instruments offered by Metal Samples with the exception of its low-power current loop operation.

  • Page 6: Principle Of Operation

    FM Approved CSA Approved The MS2500L is equipped with 10 feet of transmitter-to-probe cable and uses the standard five-pin environmental connector found on all of our existing LPR equipment. This light-armor cable passes into the housing through an explosion-proof cable gland.

  • Page 7: Modes Of Operation

    Cycle Time Adjustment The MS2500L uses a digital timing circuit which can be adjusted using three 10-position rotary switches (Figure 2). The first switch represents tens of minutes, the second switch represents minutes, and the third switch represents tenths of minutes. This allows user-selectable time cycles from 00.1 minutes to 99.9 minutes in 00.1 minute increments.

  • Page 8: Specifications

    D. Specifications Model MS2500L - Loop-Powered LPR Transmitter (Ordering # IN2500L) Physical Data Instrument Weight: 5.02 lb. (2.28 Kg) Total Weight w/ Accessories: 7.08 lb. (3.21 Kg) Instrument Dimensions: 5.81"H x 4.5"W x 4.81"D (14.76cm x 11.43cm x 12.22cm) Case Specifications:...
  • Page 9 E. Summary The MS2500L transmitter moves on-line corrosion monitoring into the realm of conventional plant practice by placing the D.C.- powered transmitter close to the corrosion rate probe (the sensor) and using the two-wire signal loop to provide both the power to the transmitter and the proportional signal corresponding to the data.

  • Page 10: Installation Procedures

    MS2510.) Front Panel Two of the three positions on the front panel of the MS2510 are used with the MS2500L. One is the loop current in milliamps and the other (far right) is corrosion rate in mils per year.

  • Page 11: Operation

    1. Connect the instrument cable to the probe. 2. Set the sample time adjust switches on the MS2500L to 999. 3. Set the operation switches to LPR and TRACK mode. 4. Power up the loop and observe the loop current (using a ammeter, recorder, etc). The current reading will change every two seconds.

  • Page 12: Accessories

    (MPY). Located at the back of the receiver are 4-20mA and 10V output terminals for connection of the receiver to a customer-supplied computer, data logger, or recorder; connection terminals for the MS2500L; and an AC power cord connector. General Specifications - MS2510 Display: 3-digit L.E.D.

  • Page 13: Probes And Electrodes

    B. Probes and Electrodes The PAIR probes used in conjunction with Metal Samples corrosion rate instruments are an essential component of a corrosion rate measuring system. For this reason, the composition of the electrodes installed on the probe must be matched as nearly as possible to the composition of the components of the processing system in which the probe and electrodes are installed.

  • Page 14: Electrodes Normally Carried In Stock

    C. Electrodes Normally Carried in Stock EL-600 Lazaran Reference Electrode with one VITON Gasket EL-601 Aluminum, Alloy 6061 (standard) EL-610 Copper (99.0% Pure) EL-611 Brass (85-15) EL-612 Admiralty Metal EL-613 Copper-Nickel EL-614 Aluminum/Bronze (92 Cu-8 Al) EL-615 Copper-Nickel (70-30) EL-620 Cold Rolled Mild Steel (1018) 0.250"...

  • Page 15: Probe Placement

    D. Probe Placement Proper probe location is the first and one of the most important considerations in obtaining pertinent data with the corrosion rate instrument. Any system can be expected to have corrosion occurring at several rates as a function of location within the system. The different rates may be due to changes of temperature, changes in velocity, impingement effects, differences of metallurgy, variations in character of fluid stream, etc.

  • Page 16: Pair Tm Probe Assembly

    3. Direct fluid impingement on the probe’s electrodes (at a very high velocity of about 10-feet-per- second or so), should be avoided as this usually results in abnormally high corrosion rates aggra- vated by erosion. 4. The probe should not be installed in a position where solids are likely to collect. Solids can build up on the probe base and electrically short out the electrodes.
  • Page 17 The electrodes should not be handled with bare sweaty or oily hands. If possible, pick up the electrodes with a paper towel or clean cloth and thread onto each of the three mounting pins. The electrodes should be firmly hand tightened in place sufficiently to deform the gasket. A one inch piece of plastic tubing slipped over an electrode is an effective means of tightening it on the probe without soil or damage.

  • Page 18: Circuit Description

    V. Circuit Description A. Introduction The MS2500L is a Linear Polarization Resistance (LPR) type corrosion monitoring instrument that translates corrosion rates obtained from polarization techniques into a 4-20ma current which is then transmitted through a two-wire twisted cable. This instrument also incorporates the ability to monitor and transmit the Corrosion Potential, obtained from LPR probes using a reference electrode.

  • Page 19: Lpr Measurement Technique

    5. The polarization current is relaxed for the same duration after which, the process can then be repeated. The MS2500L instrument incorporates the circuitry necessary to perform the above steps as well as the ability to monitor and transmit the potential difference between the reference and test electrodes.

  • Page 20: Basic Structure

    C. Basic Structure The circuitry for the MS2500L is contained on two circuit cards. The A1 Board contains circuitry for: Corrosion potential measurement. • Corrosion potential null and hold. • 10 millivolt probe polarization and reference. • Polarization current control, measurement and conversion.

  • Page 21: Circuit Description

    D. Circuit Description The following circuit description describes the behavior of the circuitry in the LPR mode with the output mode set to SAMPLE. This is the most common mode of operation for this type of instrument. Differ- ences in operation modes are described in following sections. Power Supplies The power supply circuitry is contained on the A2 Board.
  • Page 22 count down, a pulse is generated to reload the counters and to initiate either a polarization cycle or a relaxation cycle, (initially a polarization cycle), depending upon the previous state. Pulses from Q14 output of U12 are generated upon 1/10 minute intervals, (0.166 Hz), which are divided down from the 2730 Hz signal developed by the U16 clock oscillator.
  • Page 23 Polarization Current Control and Measurement The circuitry for the polarization current control and measurement resides on the A1 Board and consists A 10 millivolt polarization reference made up from the reference portion of AR3. • Current drive and scaling amplifier using the power amp portion of AR3. •...

  • Page 24: Operation Modes

    Current Loop Control The circuitry for the current loop control is contained on the A2 Board and consists of: • The current loop sense and balancing amplifier; AR5-B. • The current loop control transistor; Q1. • The current loop sense network; R23, R24, R25, and R41. The output of the current loop must be maintained at the desired signal level regardless of the amount of current drawn in order to power the circuitry.

  • Page 25: Calibration Procedure

    VI. Calibration Procedure A. Disassembly After unscrewing enclosure cover and disconnecting J5 connector, remove interconnected boards A1 and A2 from bracket. Remove shield by removing nuts and washers from switches SW1 and SW2 and screws Z5 and Z6. Replace both screws. B.

  • Page 26: Zeroing Adjustments

    E. Zeroing Adjustments Connect shorting plug to J1. Set switch SW1 to the Offset + position and SW2 to the Track position. Using the second DVM, connect the positive lead to pin 6 on AR2 and the negative lead to wire on shorting plug.

  • Page 27: Instrument Testing And Repair

    Note: Unless suitable environment and expertise is available for the testing and repair of sensitive electronics, it is recommended that component level testing and replacement for this instrument be performed only by Metal Samples. Caution: When instrument is operated in hazardous areas all power to the instrument must be removed before opening cover.

  • Page 28: Visual Inspection

    D. Visual Inspection Carefully separate the boards and inspect the two circuit boards for: • Signs of overheating or overheated components. • Short circuits caused by foreign debris. • Broken or cracked solder traces. • Corrosion on connector surfaces. • General corrosion attack to boards or components in general. •...
  • Page 29 1. The unit gives incorrect readings (Error > ±0.1 mA). 2. The unit is erratic or has intermittent operation (Readings fluctuate). 3. The unit draws excessive current (30mA or more). Isolate the problem to the faulty board by substituting a spare working board and retesting the instru- ment following the above procedures.
  • Page 30 If not, then the component must be located by substitution or the board replaced. If the cause of the problem cannot be resolved, send unit back to Metal Samples for repair. Use form in the Appendix E of this manual.
  • Page 31 Recalibration Once the instrument has been repaired, it should be recalibrated as described by the Calibration Proce- dure in Section VI. Replacement After repairing or replacing boards, interconnect the two boards making sure that the connectors on each board (probe and loop current) are at the same end and that no pins are bent while inserting. Replace the shield after removing nuts and washers from switches.

  • Page 32: Current Loop Operation And Testing

    Set the DVM to read DC voltage in millivolts. Test the Offset Corrosion Potential across the Reference and Test electrodes (pins A and B on the probe connector). For the MS2500L to operate correctly in the LPR mode, this offset potential can be no greater than + 200 millivolts and no less than -200 millivolts.

  • Page 33: Current Loop Isolation Testing

    D. Current Loop Isolation Testing Disconnect the current loop connections from the MS2500L instrument. Using a clamp or alligator type connectors, connect one end of the 1K ohm resistor to the probe body. Connect the positive side of the current loop to the other end of the 1K ohm resistor. With the current loop powered up, read the voltage drop across the 1K ohm resistor in both AC and DC modes on DVM.

  • Page 34: Appendix A: Drawings

    Appendix A: Drawings 1. Assembly Drawings A1 Board Overlays A2 Board Overlays Cable Assembly 2. Installation Drawings Physical Dimensions and Mounting Details Field Wiring...

  • Page 40: Appendix B: Parts List

    Appendix B: Parts List B.1 MS2500L...

  • Page 41: Appendix C: Effects Of Process Variables

    Appendix C: Effects of Process Variables 1. Temperature As a general rule, increasing temperature increases corrosion rates. This is due to a combination of factors: first, the common effect of temperature on the reaction kinetics themselves and second, the higher diffusion rate of many corrosive by-products at increased temperatures. This latter action delivers these by-products to the surface more efficiently.

  • Page 42: Suspended Solids

    5. Suspended Solids An increase in suspended solids levels will accelerate corrosion rates. These solids include any inorganic or organic contaminants present in the water. Examples of these contaminants include clay, sand, silt or biomass. Some specific contaminants can interfere with the Linear Polarization corrosion rate measurement, among these are iron sulfide, and hydrocarbons.
  • Page 43 Figure 6. Typical Behavior of Corrosion Rate as a Function of Process Variables...

  • Page 44: Electrode Potentials

    6. Electrode Potentials Corrosion reactions are a combination of oxidation and reduction reactions. Oxidation is the electrochemical process by which an element or species loses electrons and increases its valence state. A metal transforming to a metal ion with the simultaneous loss of an electron is an example.
  • Page 45 Oxidation Reduction Potentials The table below is a listing of some useful oxidation-reduction potentials. These values represent the thermodynamic tendency for the indicated reaction to occur on a relative basis. All potential values are compared to an arbitrary value of 0.00 volts which is assigned to the hydrogen oxidation reaction. The more negative a value, the more likely the reaction will proceed in the direction shown in table.

  • Page 46: Common Corrosive Agents

    Galvanic Series The table below is a simple version of the galvanic series of alloys in seawater. Because electrode (oxidation-reduction) potentials only apply to pure elements and true compounds, another system was developed to compare the relative reactivity of alloys in an environment. This series has the added advantage of allowing you to predict the galvanic behavior of certain alloy pairs in an environment.

  • Page 47: Appendix D: Warranty Information

    Appendix D: Warranty Information Metal Samples warrants that any part of the MS2500L and accessories which proves to be defective in material or workmanship within one year of the date of original shipment to Purchaser will be repaired or replaced, at Metal Samples’ option, free of charge. This warranty does not cover (1) probe assem- blies, (2) items expendable in nature, or (3) items subject to damage from normal wear, misuse or abuse, or failure to follow use and care instructions.

  • Page 48: Appendix E: Maintenance And Repair Instructions

    Appendix E: Maintenance and Repair Instructions This form may be photocopied for use when returning instruments to Metal Samples for repair. Please fill in all known information. Enclose a copy of the filled in form with the instrument. 1. Check one: Repair this instrument under warranty.

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