Frequently Asked Questions:

  1. What cal-gas do I need?

  2. How often should I calibrate the H2S analyzer?

  3. How often change the samle system filter?

  4. How much is the analyzer venting?

  5. What should the sweep valve be set at?

  6. How long will the tape last?

  7. Does the Bypass time out?

  8. How often does the humidifier need to be filled?

  9. What are the analog output settings?

  10. What is the range of the H2S analyzer?

  11. Display is indicating a sensor fault.

  12. What is the gain of the analyzer supposed to be?

  13. Erratic H2S readings.

  14. The analyzer was flooded, how do I fix it?

  15. Analyzer reading incorrectly.

  1. What cal-gas do I need?

    2. Ideal cal-gas concentration would at the value normaly operating at or alarming at. Alternatively cal-gas to use is 3/4 concentration of the range of the analyzer.

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  2. How often should I calibrate the H2S analyzer?

    3. Calibration checks should be done ever 3 to 6 months. Or as required by site preventive maintenance schedule.

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  3. How often should I change the sample system filter?

    4. The Filter should be changed as required. The frequency is dependant on the liquid content and particulates in the gas. A higher volume of a liquids and particulates will require more frequent changes. Filters should be checked when analyzer is calibrated.

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  4. How much is the analyzer venting?

    5. The standard H2S analyzer vents 4 standard cubic feet per hour.

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  5. What should the sweep valve be set at?

    6. The sweep valve should be just opened slightly until flow can be felt from the tubing. This will reduce lag time and allow liquids to be removed.

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  6. How long will tape the tape last?

    7. The analysis time is dynamic and changes with the concentration of the H2S during the sample.

    Aperture H2S (ppm) Tape Life (Days)*
    None 4.0 ppm 34.7
    1/16th 16.0 ppm 30.4

    *Tape life based on constant concentration sample over a averaged analysis time with a 300 ft tape.

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  7. Does the Bypass time out?

    8. By default the H2S analyzer does NOT time out when placed in bypass. A time out feature is available in the software, as well as Bypass Disable.

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  8. How often does the Humidifier need to be filled.

    9. As long as there is some fluid in the humidifier it will be able to maintain the humidity of the gas. The fluid should be topped up each time the analyzer is calibrated or the tape is changed.

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  9. What are the Analog Output settings?

    10. 4-20mA wiring

    The analog output of the H2S analyzer is a 4-20 mA signal calibrated at factory. The connections requires loop power from the PLC. If loop power is not able to be supplied, a powered AO board addition can be purchased.

    Symptom Solutions
    PLC Indicating 0 mA Wiring to analyzer is incorrect.
    Power to loop is not present. If loop power not supplied then Powered AO board option may be required.
    PLC Indicating ~2 mA Analyzer in Bypass
    PLC Indicating higher or lower signal than analyzer display Scaling of analyzer is different setting on PLC

    Click here for typica Analog Output wiring diagrams

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  10. What is the range of the H2S Analyzer?

    11. Determining the range

    The range of the analyzer is set at the time of purchase. The accuracy and tape life are optimized to the customers request. The optimized range can be determined by the calibration sheet found in the back of the manual.

    The Envent H2S analyzer is capable of indicating 10x the optimized range of H2S concentration. Accuracy of the reading can not be guaranteed when indicating outside the optimized range.

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    Optimizing the range

    Range (ppm) Aperture
    0-10 None
    0-20 * 1/16th
    0-50 1/32nd
    0-100 Consult Envent Eng.
    * If the shut in alarm value is less then 10 ppm no aperture is ideal.

    For dilution analyzer systems the range adjusment depends on the dilution tubing. Please consult Envent about dilution range adjustments

  11. Display is indicating a Sensor Fault

    12. Sensor Fault

    The sensor Fault is a result of the sensor mV level being below 500 mV or above 1200 mV. Most often caused by an incorrect zero being achieved.

    1. Put the Analyzer in Bypass
    2. Turn off sample gas at flowmeter
    3. Press the Menu/Set button until MTR RUN displayed
    4. Press Left or Right on the Display to move the tape to a new white piece of tape
    5. Remove the cover the sensor block. Press the small pushbutton located on the lower left side next to the wire connector. The sensor block will enter a "re-zero" procedure indicated by a red led.
    6. When the "re-zero"procedure is complete the green led should illuminate.
    7. Initiate another motor run
    8. Press the Menu/Set button until zero is displayed. Value should be between 900 & 1100 mV.
    9. Turn on sample gas to flow of two
    10. Take analyzer out of Bypass.

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  12. What is the gain of the analyzer supposed to be?

    13. Aperture Gain*
    None 2.5-3
    1/16th 7.5-8.5
    1/32nd 10-13
    *Gain numbers based on standard H2S analyzers. Numbers do not apply to Total Sulfur and Dilution systems. Please consult factory cal-sheet for calibration numbers.

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  13. Erratic H2s readings

    14. Possible Reasons Solutions
    Trigger slide not seated properly Ensure Trigger slid is seated in the groove of the sample chamber
    Sample vent blocked or insufficient. Vent should be 1/2" tubing on a downward slope. Ending at shepards hook. Possible heat trace required on tubing
    Contaminants in sample system Sample system has been flooded or contaminated. Sample system requires cleaning. Refer to cleaning procedures in manual.

    Venting recommendations

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  14. The analyzer was flooded, how do I fix it?

    15. Cleaning the analyzer

    Once the analyzer has been flooded with contaminants it requires cleaning. Please refer to the Cleaning Procedure

    After the cleaning is complete it is advisable to re-calibrate the analyzer.

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  15. Analyzer reading incorrectly

    16. Symptom Reasons Solution
    Analyzer reading higher H2S than expected Gain too high. Calibrate with cal-standard and adjust gain.
    Vent line blocked Check vent line for moisture build up and possible frozen sections. Review recommending venting.
    Aperture stip become dislodged Reattach aperture strip with RTV 102 silicone
    Analyzer reading lower H2S than expected Gain too low. Calibrate with cal-standard and adjust gain.
    Sample system contaminated Refer to cleaning procedure to remove contaminants.
    Trigger slide not seated properly Ensure trigger slide is firmly seated in groove of chamber block

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