Reaction vessels maintenance - causes of malfunction and approaches

A reaction vessel is common equipment in cement plant and chemical plant. It may be damaged for a variety of reasons during operation, causing production to be stopped. This article will focus on general maintenance methods when the reaction vessel is damaged.

• Shell damage
• Excessive temperature and pressure
• Seal leakage
• Unusual noises in the vessel
• The agitator of glass-lined reactor falling off
• The glass-lined reactor flange leakage
• Glaze problem and tiny holes
• Motor current exceeding the rated value

Causes and approaches of shell damage (corrosion, cracking, and through hole)
1. Radiation from the medium (pitting, intergranular corrosion) - The shell with corrosion-resistant materials needs to be relined or partially welded;
2. Cracking or alkali brittleness due to thermal stress- The stress should be eliminated after welding, and the cracking should be repaired;
3. Getting thinner because of abrasion or uniform corrosion - The body needs to be replaced if its thickness is lower than the allowable thickness.

Causes and approaches
of excessive temperature and pressure
1. The gauge is out of order and the control is not tight - Inspect and repair the automatic control system, and strictly implement the operating procedures;
2. Misuse, an improper ratio of raw materials, a violent chemical reaction - Bleed off pressure according to the operation methods, and regularly and quantitatively feed materials according to the regulations to prevent misuse;
3. A side reaction occurs due to poor heat transfer or mixing performance - Increase the heat transfer area or remove the scale, improve the heat transfer effect, repair the stirrer, and improve the mixing efficiency;
4. The intake pressure is too high due to the malfunction of intake valves - Turn off the main steam valve and repair it.

Causes and approaches of seal leakage
1. Packing
(1) The agitator shaft is worn or corroded, causing a large gap -  Replace or repair the agitator shaft and process it by a lathe to ensure the roughness;
(2) The oil ring is improperly positioned or the oil circuit is blocked so that the oil seal cannot be formed - Adjust the position of the oil ring and clean the oil circuit;
(3) The gland is not compacted, the packing has poor quality or is used too long - Press or replace the packing;
(4) Corroded stuffing box - Repair or replace it.

2. Mechanical seal
(1) The end face of mating and rotating rings deform or are impaired - Replace the friction pair or re-grind;
(2) Large specific pressure of the end face, thermal deformation generated by friction - Adjust the specific pressure to appropriate value, improve the cooling system so heat can be taken away in time;
(3) Incorrect sealing ring materials, insufficient pressing force, or the V-shape sealing ring is installed reversely - The selection of sealing ring materials, the installation should be reasonable, and there must be sufficient pressing force;
(4) The vertical error between the axis and the end face of the mating ring is too large - Shutdown the machine, re-align the axis, ensure that the perpendicularity error is less than 0.5 mm;
(5) The operating pressure and temperature are unstable, hard particles enter the friction pair - Strictly control the process index, particles and crystals cannot enter the friction pair;
(6) Excessive axial movement - Adjust and overhaul to ensure that the axial movement will not exceed the standard;
(7) Mounted mating, rotating rings leak - Improve the installation process, the interference should be appropriate, or the adhesive should be high-quality and easy to use.

Causes and approaches of unusual noises in the vessel
1. The friction between the agitator and wall, or accessories in the vessel (coiled pipe, thermowell) - Shutdown the machine, inspect, and keep distance between the agitator and the accessories;
2. Loose agitator - Shutdown the machine, inspect, and tighten the screws;
3. Knocking noise of bulged lining and the agitator - Fix the blister or replace the lining;
4. The agitator is bent or the axle bearing is broken - Repair or replace the shaft and bearing.

Causes and approaches of the agitator of glass-lined reactor falling off
1. Corroded and fractured by the medium - Replace the shaft or repair by FRP;
2. The motor rotates in the opposite direction - Shutdown the machine and change the direction.

Causes and approaches of the glass-lined reactor flange leakage
1. The surface of flange is damaged - Repair, coat with anti-corrosive painting or resin;
2. Unreasonable gasket materials, incorrect joint installation - Choose gasket material according to the process requirements, the gasket interfaces should be lapped and the position should be correct;
3. Loose or insufficient clamps - There should be a sufficient number of clamps that are tightened according to the design requirements.

Causes and approaches
of glaze problem and tiny holes
1. There are acidic impurities in the shaft tube or clamps, causing hydrogen embrittlement - Neutralize with sodium carbonate, then rinse the corroded shaft tube, clamps with water, or repair them, if the corrosion is severe, replace them;
2. The layer is not dense, which contains a hidden danger of tiny holes - It is repairable if the situation is not severe, if not, replace it.

Causes and approaches of motor current exceeding the rated value
1. Bearing damage - Replace the bearing;
Low temperature in the vessel and thick materials - Adjust the temperature according to the operating procedures and the viscosity of materials cannot be too high;
3. The speed of the main shaft is relatively fast - Control the speed within a certain range;
4. The diameter of the agitator is too large - Appropriate adjustment.


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