How to troubleshoot abnormal pressure in solvent recovery system? Direct answer: First classify - if the vacuum degree cannot be improved, check the pump and seal; System positive pressure is too high or cannot be lowered, check for blockage and valve status; The pressure fluctuation is irregular, mostly due to process load or instrument problems. The safety valve does not operate normally, and its value lies in the jump when overpressure occurs. Therefore, the investigation is focused on the set value and lead seal state, not using it as a regulating valve. Classifying and positioning before starting is much more efficient than dismantling the entire system one by one. This article explains the classification phenomena, troubleshooting sequence, and key points for instrument verification.
The first type is the inability to increase the vacuum level: the pump is running, the inlet vacuum gauge reading is low or climbing slowly, and the system's recovery capacity is reduced. The second type is positive pressure anomaly: high pressure in the tower or buffer tank, intermittent exhaust sound near the safety valve, and high system resistance displayed on the differential pressure gauge. The third type is fluctuation: the pressure fluctuates significantly with the load or periodic action, which is common in adsorption switching or intermittent feeding conditions. If the fluctuation exceeds the design range, it should be checked. The disposal entry points for the three types of phenomena are completely different. First, classify them according to the table, and then decide whether to check the pump, blockage or load in the next step.
Before and after pressing the vacuum side pump, check whether the inlet valve is fully open, whether the inlet filter is blocked, and whether the working liquid level and temperature are normal. These three are daily level issues with the highest proportion; Upon further inspection of the pump itself, it was found that the clearance was worn, the sealing components were aged, and the blades of the rotary or water ring pump were in good condition. If the clearance exceeded the tolerance, the pumping capacity would decrease by one level; Seal the final inspection, flange, valve stem, and sight glass are high-risk areas for leakage, and locate them using soap solution method or portable detector. After repair, retest the vacuum degree and confirm the restoration by comparing it with the nameplate curve. Do not repeatedly disassemble and install the pump to find the cause. Check the inlet and sealing sides thoroughly before starting the pump.
If the positive pressure is too high, check for blockage first: scaling on the heat exchange surface, rising pressure difference in the adsorption bed, liquid accumulation at the low point of the pipeline, and insufficient valve opening will all cause the system resistance to increase and pressure to shift back. Check the pressure measurement section by section along the process, and the location of the sudden change in pressure difference is the blockage point. The problem of liquid accumulation occurs frequently after parking and low temperatures. The low point condensate drain valve is discharged according to regulations, and the heat tracing system is confirmed before winter. The valve status is checked separately: the check valve is stuck, the regulating valve is drifting, and the isolation valve is leaking, all of which are manifested as abnormal pressure. These problems are hidden and should be tested according to the maintenance cycle.
The management scope of safety valves is verification and recording: sending them for calibration on a periodic basis, ensuring that the lead seal is intact, and the set value ledger is consistent with the on-site identification; If it is found that there is abnormal movement or return after jumping, it must be rechecked after replacement. Daily inspection only focuses on appearance and lead sealing, do not adjust pressure online. Instrument verification is a prerequisite for troubleshooting: pressure gauges that have exceeded their calibration period and transmitters with zero drift can cause errors in judgment from the source; Compare the key measurement points with two tables or with a portable table to confirm the reliability of the readings before discussing system issues. The investigation conclusion should be recorded: phenomena, measurement point data, disposal actions, retest results, and archived in equipment archives.
| Exception Type | Priority Doubt | Investigation methods | Common root causes |
|---|---|---|---|
| The vacuum level cannot be increased | Pump and inlet side | Measure the inlet vacuum and check the filter | Filter blockage and pump wear |
| The vacuum level cannot be increased | Seal air leakage | Soap solution or detector | Flange valve stem sight glass |
| Positive pressure is too high | System resistance | Section-by-section pressure measurement | Scaling effusion bed plugging |
| Positive pressure is too high | Valve status | Action test | stuck drift internal leakage |
| Pressure fluctuation | Load and switching | Control process cycle | Intermittent feed switching |
| Reading in doubt | Instrument failure | double table comparison | Overtime zero drift |
Check again after take-off: take-off may change the state of the sealing surface and spring, and install it back without check, which is equivalent to handing over the overpressure protection to a valve with unknown state; On the premise that the lead seal is in good condition, it will be sent to school periodically, and it will not be adjusted online.
Check the inlet side and seal: filter blockage, insufficient opening of inlet valve and abnormal temperature of working fluid are the most common three items; The sealing leakage point will form a bypass after the pump. During re-measurement after maintenance, check the pressure step by step, and do not dismantle the pump repeatedly.
Look at the amplitude and consequences: the periodic fluctuation in the design interval is normal and can be explained with the process action; If it exceeds the interval or is accompanied by abnormal vibration, check it according to the blockage or valve problem. The fluctuation itself is often the precursor of blockage.
This article by LuoyangWohong PetrochemicalEquipment Co., Ltd. arranges that the company provides design, manufacturing and operation and maintenance services for condensation recovery, membrane separation recovery and complete solvent recovery devices for chemical and pharmaceutical enterprises. If you need process evaluation or scheme configuration, please contact and exchange.
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