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FAQ of Centralized Exhaust Gas Detection (2)

Time：

2022-11-02

FAQ of Centralized Exhaust Gas Detection

11. During the sampling process, the actual flow of the instrument always fluctuates up and down and cannot be stabilized at the set value.

Possible causes: the pressure was not adjusted to zero before sampling, and the flow was always unstable due to the zero drift of the sensor; Multiple samplers are connected to the same plug row and started at the same time, causing voltage instability; Other high-power equipment around the sampler is connected to the same group of power supply, causing impact;

12. After sampling, it is found that the sampling head cannot be removed from the host.

Possible causes: When installing the sampling head, the screw thread port at the connection was not correctly introduced, and forced to rotate or even installed with external tools without proper alignment. The installation of the sampling head is very easy after the correct introduction of the screw port, and it can be operated with bare hands. This situation will also lead to gas leakage in the sampling, and the sampling results will naturally become waste samples.

13. The results of analysis after sampling differ greatly from the actual situation or estimated value.
Fault judgment: the sampling process operation is incorrect.
Possible causes: the sampling head leaks. Check whether all the connecting parts inside the sampling head have sealing silica gel. Shake the sampling head gently to check whether there is a collision sound; The capture plate is not coated with Vaseline or the Vaseline fails to be replaced in time, nor can the annular filter membrane replace Vaseline; The air inlet of the sampling head is deformed or damaged; Sampling heads made of different materials cause static electricity to adsorb the samples; The filter membrane shall be installed reversely, and the soft and fluffy side shall be upward; The edge of the filter membrane is damaged when the filter membrane is taken and discharged, and the broken slag is not collected together during collection; Power failure, shutdown and other abnormal conditions occur during sampling; The actual flow value of the instrument does not meet the requirements of the verification standard; The distribution distance of multiple samplers does not meet the sampling standard, and the distance is too close to interfere with each other.

14. The setting interface can be accessed, but the sampling pump does not work normally after starting sampling.
Fault judgment: the control is damaged and the sampling pump is damaged.
Possible causes: the control unit is damaged, and the resistance during daily sampling is too large, which makes the device be in full load state for a long time, resulting in device burning; The sampling pump is damaged, and the incorrect filter membrane is selected during sampling, which causes excessive resistance and damages the sampling pump blades; If the continuous sampling time is too long, resulting in overheating of the instrument and damage of the sampling pump after fatigue operation, it is not recommended to exceed the time of a single sampling point required in the detection method. If continuous work is required, it is recommended to set the interval sampling on the basis of ensuring the sampling time.

15. After setting the flow rate, start sampling, and the pump can operate normally, but the sound will become louder and louder, and it will soon reach full power shutdown protection.
Fault judgment: the gas circuit is blocked.
Symptom: the gauge pressure is much higher than the normal value.
Possible causes: The cutting plate in the sampling head is installed reversely, and the cutting round hole is directly pressed on the catch plate, causing blockage; The filter membrane is improperly installed, because it is wrinkled, damaged or even blocked due to multiple filter membranes; The installed filter membrane is non glass fiber filter membrane, and the particulate matter sampler cannot carry heavy metal, fluoride and other sampling tasks, because the required quartz, nitric acid fiber, organic filter membrane, etc. will produce higher resistance; Check the protective screen at the air inlet of the instrument at the connection with the sampling head for foreign matter blockage. If there is foreign matter blockage, it will also cause shutdown; The flow parameters in the instrument maintenance interface are changed abnormally; The sampling flow is not normal, and the set value is too high; The pipeline connection inside the sampler falls off, causing uncontrolled flow.

16. The measured results after sampling differ greatly from the actual or estimated conditions.
Fault judgment: the process is wrong.
Possible causes: the absorption bottle does not meet the requirements, especially the glass plate resistance should meet the standard requirements; Whether the absorption solution is installed incorrectly and does not correspond to the target gas; The absorption temperature does not meet the requirements, and the temperature of the absorption solution directly affects the absorption efficiency; Abnormal conditions such as over shutdown protection or power failure occur during sampling.

17. Unqualified materials submitted to the metrological institute for inspection.
Possible causes: the operation process and verification conditions during verification do not meet the requirements of verification regulations; The load mode that conforms to the actual use state is not selected; The internal parts of the instrument are damaged due to over suction, especially the balance of the rotor will be affected once the rotor is inverted; The standard instrument selected by the metrology institute does not meet the requirements of the latest verification regulation; The calculation method of flow is incorrect, especially the current scale of rotor type that is not adjusted represents the actual verified flow. For electronic type, the type of flow displayed shall be confirmed.

18. After the rotor flowmeter regulates the flow, the rotor will drop over time.
Fault judgment: humidity effect.
Possible causes: The desiccant is invalid. Check the color of the desiccant in the drying cylinder. If more than half of the desiccant has changed color, replace it; If the drying cylinder leaks, check the air outlet of the drying cylinder. If it leaks, wet air will be directly inhaled; If the sampling time is too long, the rotameter is only suitable for hourly sampling. If the sampling time is too long, the rotor will drop.

19. After starting the sampling, the sampling pump can run, but it will stop sampling automatically soon, and the interface is in the suspended state.
Fault judgment: the pipeline is blocked.
Characterized phenomenon: the gauge pressure is much higher than the normal value.
Possible causes: the pipeline is bent, including whether the hoses inside and outside the instrument, especially the part connected with the absorption bottle, are squeezed by the protective cover; The pipe connected with the pressure sensor inside the instrument falls off, causing abnormal flow; Excessive dust accumulation at filter screen of drying cylinder or filter element of instrument leads to excessive resistance; In extremely cold areas, the pipeline is blocked due to icing inside; The measured flow is incorrect due to the abnormal flow parameters in the instrument maintenance menu.

20. The sampling flow shows normal, but the absorption solution has no bubbles or few bubbles.
Fault judgment: the system leaks air.
Characterized phenomenon: the gauge pressure value will be far lower than the normal value.
Possible causes: the pipeline falls off, including the internal and external pipelines of the instrument, especially the connection position between the hose and the absorption bottle may be loose or skewed; The drying cylinder leaks, and check whether there is a sealing ring or whether there is residual desiccant residue on the sealing ring; The measured flow is incorrect due to the abnormal flow parameters in the instrument maintenance menu.