1.1 main content:
This maintenance work instruction book specifies the specific technical requirements, safety precautions and implementation steps of the maintenance, repair and commissioning of the temperature measuring thermal resistance.
1.2 Scope of application:
This maintenance work instruction is applicable to all instrument personnel in the instrumentation section of the electric instrument workshop.
1.3 The basic principle of thermal resistance temperature measurement
The principle of thermistor temperature measurement is based on the fact that the resistance value of the metal conductor increases as the temperature increases.
1.4 Thermal resistance structure
The thermal resistance is composed of a temperature sensing element, a lead wire, an insulating tube, a protective tube, and a junction box.
1.5 Industrial thermal resistance temperature measurement uses the purpose of three-wire system:
The purpose is to reduce the influence of the resistance of the connecting wire between the thermal resistance and the measuring instrument, and the measurement error caused by the change of the wire resistance with the change of the ambient temperature.
1.6 Characteristics of thermal resistance: It is the most commonly used temperature measuring component in the medium and low temperature zone.
(1) Small volume, no internal void, small thermal inertia, and small measurement lag.
(2) Good mechanical properties, vibration resistance and impact resistance. (3), can be bent and easy to install. (4) Long service life.
2, maintenance purposes
In order to enable the RTD temperature measuring element to truly and accurately reflect the actual temperature of the substance to be measured, it is ensured that the components of the RTD are intact.
3. Preparation before maintenance:
(1) Division of personnel:
1. Person in charge of maintenance: According to the fault phenomenon of the instrument components, determine the maintenance project, be responsible for the quality of the repair, confirm whether the quality of the spare parts to be replaced is qualified, whether the specifications, length and material are consistent with the original thermal resistance components, and ensure the repair or replacement. The thermal resistance is in good condition, the components are complete, and the temperature is displayed accurately; the quality and quantity of the inspection work are guaranteed.
2. Person in charge of safety: responsible for safety monitoring during maintenance, whether the safety measures are in place, whether they are perfect, whether the protective equipment is fully prepared, whether the wearing is standardized, and reminding the person in charge of maintenance to pay attention to the maintenance; to ensure that safety protection measures are in place, Ensure that the maintenance work is completed safely and smoothly.
(2) Working hours:
(3) inspection tools: 12-inch live mouth, pliers, screwdriver, tape, fine sandpaper.
(4) repair spare parts: thermal resistance, metal winding mat.
(5) the handling of the ticket: need to go through the maintenance notice, maintenance task book, process delivery order (according to the actual situation),
When you are ascending, you need to apply for a high-level operation permit.
4. Requirements during the overhaul process:
(1) First, the spare parts required for maintenance shall be implemented. The spare parts shall be consistent with the specifications, model, material and length of the replaced or repaired thermal resistance.
(2) Tools that are ready to use, the tools must be appropriate, intact, and complete.
(3) The relevant ticket is fully processed and can be constructed after being approved by the dispatcher, operator and relevant personnel.
(4) When repairing the thermal resistance, it must be confirmed whether it has a regulating valve and interlocking and alarm device. If the interlocking alarm is required, the interlocking should be removed in advance and the operator should be reminded to confirm, and the operator should be required to strengthen the monitoring; for example, the automatic control device with regulating valve The operator is required to bring the regulating valve to the manual state and the operator is on site for monitoring.
(5) Before disassembling or repairing the RTD bushing, it must be confirmed that the process is qualified and the operator is on site.
(6) When replacing or repairing the RTD bushing, the body must avoid the RTD mounting port and stand at the upwind direction.
(7) When replacing the RTD bushing, the operator is required to discharge the medium and pressure in the pipeline. After inspection and confirmation, the person in charge of maintenance shall be disassembled, wear safety protective equipment, and take safety protection measures.
(8) When replacing the thermal resistance sleeve, replace the winding mat with the winding mat. Make sure that the material is correct and the sealing surface is positive.
(9) When replacing the thermal resistance core or checking the wiring, pay attention to the inspection that the casing should be clean, free from rust and dirt, and the casing is free of leakage; note that the replacement thermal resistance core should be consistent with the original core length and will be hot. The resistor core is fixed, the wiring is fastened, and there is no burr at the wiring.
(10) When disconnecting the signal line, it should be noted that the signal line should not be short-circuited or grounded. The three signal lines should be wrapped with tape, and the shielding layer should also be checked to prevent grounding.
(11) Seal the inlet of the RTD junction box with explosion-proof mud and make waterproof measures.
(12) When checking the thermal resistance fault, check and measure the integrity of the signal line, confirm whether the signal line has intermediate connectors, whether there is contact failure, oxidation, looseness, etc., confirm the normal condition of the module channel,
5, maintenance quality requirements:
The repair or replacement of the thermal resistance bushing (core) should be standardized and firm, the joints of the components and the wiring are fastened, the sealing surface of the winding pad is pressed, the material is correct, the temperature is displayed accurately, and the waterproof measures are taken.
6, after the maintenance requirements:
(1) After the completion of the maintenance task, the site will be cleaned up in time, so that the net site of the work is cleared.
(2) After the completion of the inspection, after the observation temperature is accurate and normal, the operator is required to promptly put in the interlocking alarm device that was removed during the inspection, and the regulating valve is put into the normal use state in time.
7, inspection and maintenance
(1) Check the appearance of the thermal resistance during the daily inspection: whether the junction box and the protection tube are in good condition and whether the waterproof measures are perfect.
(2) Whether the connection of each signal line is loose or worn, and there is no grounding phenomenon due to excessive burr.
(3) Whether the signal threading pipe and the explosion-proof pipe of each signal line are intact, whether the fixing is firm, and whether the connection is intact.
(4) There is no leakage at the joint between the thermal resistance protection sleeve and the process pipe.
(5) When parking, the corrosion and scouring of the thermal resistance protection tube should be checked in time and replaced seriously.
(6) After each rain, check whether there is water in the cable trench and drain the water in time.
8. Common fault phenomena and treatment methods:
9. Safety precautions
(1) It is necessary to obtain the approval of the craftsman in advance for the maintenance work that may cause the process parameters to fluctuate or the interlocking alarm device and the regulating valve.
(2) Select the material of the temperature measuring sleeve and the sealing gasket according to the process medium.
(3) Attention should be paid to the phenomenon that the instrument wiring can not be short-circuited or grounded during maintenance, and the shielding of the computer cable should not be grounded.
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