Detcon, Inc. TP-424C Hydrogen Sulfide Sensor Operator’s Installation & Instruction Manual March 18, 2014 • Document #2324 • Version 2.
Table of Contents 3.0 Description 3.1 Principle of Operation 3.2 Constant Temperature Control 3.3 One Man Remote Calibration 3.4 Application and Interference Data 3.5 Specifications 3.6 Installation 3.7 Start Up 3.8 Calibration 3.9 Calibration Frequency 3.10 Heater Voltage Adjustment 3.11 Fault Supervision 3.12 Trouble-shooting 3.13 Parts List 3.14 Warranty 3.15 Service Policy Detcon Model TP-424C Hydrogen Sulfide Sensor PG.
.0 DESCRIPTION Detcon Model TP-424C, hydrogen sulfide sensors are designed to detect and monitor H2S in air over the range of 0-100 ppm. The sensor assembly consists of a solid state semi-conductor sensor in a stainless steel housing, a plug-in control transmitter circuit, a base connector board and an explosion proof enclosure. The sensor assembly is suitable for use in Class I; Div. 1; Groups B, C, D electrically classified areas.
+ SIG SIGNAL FLT VOLT HTR CURRENT FLT HEATER TP-424C PPM H2S 4-20 mADC SPAN COARSE FINE TEMP detcon inc. H OU ST ON X T E A S Base Connector Board The base connector board is mounted in the explosion proof enclosure and includes: the mating connector for the control transmitter, reverse input and secondary transient suppression, input filter, and lugless terminals for all field wiring.
3.1 PRINCIPLE OF OPERATION In operation TP-424C sensors are installed in industrial areas where hydrogen sulfide gas leaks are most likely to occur. Method of detection is by diffusion adsorption. As hydrogen sulfide gas diffuses through the sintered porous filter and contacts the surface of the heated sensor element, the metal oxide sensor film decreases in electrical resistance non-linearly proportional to the concentration of gas.
Ammonia Diesel Fuel Demethyl Sulfide Ethylene Freon 12 Hydrogen Methyl Mercaptan Sulfur Dioxide Toluene Ethanol 500 = 0 5000= 0 4.4 = 0 200 = 0 1000 = 0 1000 = 8 5=8 300 = 0 32 = 0 500 = 2 3.5 SPECIFICATIONS Method of Detection Solid state metal oxide.
16 14 600 900 2000 3000 Note 1: This wiring table is based on stranded tinned copper wire and is designed to serve as a reference only. Note 2: Shielded cable may be required in installations where cable trays or conduit runs include high voltage lines or other sources of induced interference.
Local Electrical Codes Sensor and transmitter assemblies should be installed in accordance with all local electrical codes. Use appropriate conduit seals. Drains & breathers are recommended. The sensor assemblies are designed to meet NEC and CSA requirements for Class I; Div. 1, Groups B, C,D environments. Note: An appropriate conduit seal must be located within 18" of the sensor assembly. Crouse Hinds type EYS2 or EYD2 or equal are suitable for this purpose.
Remote Mounting Applications Some sensor mounting applications require that the gas sensor head be remotely mounted away from the sensor transmitter. This is usually true in instances where the gas sensor head must be mounted in a location that is difficult to access. Such a location creates problems for maintenance and calibration activities.
3.7.1 Initial Operational Tests After a warm up period of approximately 60 minutes, the sensor should be checked to verify proper operation and sensitivity to H2S gas. Caution: Initial test and operational procedures require that the sensor junction box cover be removed and, therefore, negate the electrical classification. De-classify the area before proceeding. Required Materials Digital volt/ohm meter Jeweler’s type screwdriver Test gas: H2S in Air in the range 25 to 50 ppm.
3.8 CALIBRATION Note 1: Detcon solid state MOS hydrogen sulfide sensors give erroneous readings in oxygen depleted environments. Calibration gas mixtures of H2S in air are required. (Do not use span gas cylinders with nitrogen and H2S mixtures.) Material Requirements Detcon P/N 6038 Threaded Calibration Adapter Span Gas: 25 ppm H2S in air at a controlled flow rate between 200 and 500 cc/min.
3.9 CALIBRATION FREQUENCY In most applications, monthly to quarterly calibration intervals will assure reliable detection. However, industrial environments differ. Upon initial installation and commissioning, close frequency tests should be performed weekly to monthly. Less frequent test schedules should be implemented based on analysis of tests prior to adjustment. 3.10 HEATER VOLTAGE ADJUSTMENT Each sensor is pre-calibrated and tested prior to shipment.
setting of 235 mW and is acceptable. If the value was too low you would increase the voltage by turning the potentiometer labeled “TEMP” clockwise, and then recalculate with the new voltage and current readings. If the value was too high, you would decrease the voltage and repeat the process as necessary to reach the desired power setting. 3.11 FAULT SUPERVISION Model TP-424C sensors incorporate fault circuitry which monitors both the heater loop and sensing film loop of the H2S sensor element.
Unstable output/Sudden spiking Unstable power supply, Inadequate grounding, Inadequate RFI protection. 1. Verify Power source. 2. Contact Detcon to optimize shielding and grounding. 3. Add RFI protection accessory. 4. Check area for after gas releases, such as cleaning chemical vapors. Nuisance Alarms 1. Check condulet for accumulated water and abnormal corrosion. 2. If Nuisance alarms happening at night suspect condensation in condulet . 3.
3.14 WARRANTY Detcon, Inc., as manufacturer, warrants each hydrogen sulfide sensor element (P/N 399-800000-000), for a ten year period under the conditions described as follows: The warranty period begins on the date of shipment to the original purchaser, and follows the schedule below. The sensor element is warranted to be free from defects in material and workmanship.
