In wet desulfurization system, how to deal with the leakage of flue gas channel expansion joint is the most common thorny problem encountered by operation and maintenance personnel. Water seepage from the skin of non-metallic expansion joints, leakage from the weld of metal expansion joints, dripping from the flange bolts... These water leakage phenomena not only cause acid corrosion and pungent smell on the ground, but also accelerate the corrosion of equipment, forcing the unit to reduce load or even shut down in severe cases. This article will systematically explain how to deal with water leakage of flue gas channel expansion joint from leakage cause diagnosis, emergency leakage plugging, radical repair to preventive measures, and provide a complete solution for on-site technicians.
First, diagnose first: find the cause of water leakage before starting
Before dealing with flue gas channel expansion joint leakage, it is necessary to accurately judge the location, type and root cause of the leak. Different types of water leaks are dealt with in very different ways.
1. Identification of water leak location
| Location of water leak | Typical phenomenon | Common causes |
|---|---|---|
| Water seepage on skin surface | Moist plaque, slow drip | Grooved water penetrating fabric layer |
| Dripping water at pressure plate bolts | Water droplets at the root of the bolt | Bolt loosening or corrosion fracture |
| Skin breakage spray | Obvious break, water leakage under pressure | Mechanical damage or high temperature breakdown |
| Flange face leakage | Water marks on flange joint | Aging gasket, insufficient bolt preload |
| Metal weld leakage | Water droplets at the weld | Stress corrosion cracking or weld defects |
| Drain hole blocked overflow | No water flowing out of the drain pipe and water accumulation in the frame | Dust clogging dust net |
2. Water leak severity classification
Before making a decision on how to deal with the leakage of the flue gas channel expansion joint, judge the urgency:
| grade | Phenomenon | Urgency | Recommendation Processing Method |
|---|---|---|---|
| Level 1 | Slight water percolation, no significant drip | Plannable processing | Fix during scheduled downtime |
| Secondary | Obvious dripping, acid on the ground | Higher | Temporary plugging + planned shutdown for repair |
| three-level | Jet-like water leakage, system parameter fluctuation | Emergency | Immediate shutdown processing |
2. Emergency treatment: temporary leak plugging without stopping the machine
In an emergency situation where immediate shutdown is not possible, the following emergency plan can be used to deal with flue gas passage expansion joint leakage.
Material Preparation
- High temperature resistant leak plugging glue stick (instantaneous curing type, temperature resistance ≥200℃)
- Stainless steel belt or throat hoop
- Acid-resistant rubber sheet (thickness 3-5mm)
- High temperature sealant (silicone type)
Operation Procedures
- Quick Surface Cleanup: Use a wire brush to remove floating dust and rust around leakage points
- Glue stick sealing: After kneading and softening the leakage-plugging glue stick, press it firmly at the leakage point to form a covering layer
- Rubber pad covering: Cover acid-resistant rubber sheet outside the cement to expand the sealing range
- Clamp fastening: Clamp the rubber plate to the expansion joint with stainless steel belt or throat hoop
- Inspection effect: Observe whether the water leakage stops or significantly reduces
Precautions
- Only suitable for low pressure (≤5kPa) small leakage
- Temporary measures are valid for 1-4 weeks
- Must be permanently repaired at the latest scheduled downtime
- Pay attention to anti-scalding and anti-acid during operation
3. Radical repair: permanent solution
Scheme 1: Treatment of water accumulation in groove of non-metallic expansion joint
The water seepage of the skin of the non-metallic expansion joint is rooted in the water accumulation of the annular groove formed between the pressure plate and the skin when the skin is installed. Prolonged soaking in acid water leads to penetration of fabric layers. This is the most common scenario in how to deal with water leakage of flue gas channel expansion joint.
Radical Cure-Groove Filling Technique:
- Shutdown cleaning: After the system shuts down and cools down, remove the pressure plate bolts and remove the old skin
- Frame cleaning: remove the floating dust and corrosion of the frame, and check the corrosion
- Underlayer anti-corrosion: Apply highly elastic tung oil gel or epoxy anti-corrosion coating to the bottom of the groove
- Fill the sealing layer: fill in closed-cell foamed butyl rubber (compression ratio 7:1), compact in layers, and fill the grooves
- Surface sealing: The groove is completely smoothed with high elastic sealant, with a thickness of about 5mm
- Install new skin: Lay new skin, install pressure plates, tighten bolts in stages
- Curing and curing: It can be put into operation after standing for 24 hours
Key advantage: After filling the grooves, acid water cannot accumulate, fundamentally eliminating the penetration route.
Scheme 2: Water leakage treatment of pressure plate bolts
Problem performance: dripping water at the root of the bolt, mostly due to loose or corrosion fracture of the bolt.
Processing steps:
- Use electric wrench to tighten all bolts in diagonal order, torque 50-80N·m
- If the bolts are severely corroded, replace them with 304 or 316L stainless steel bolts one by one
- Apply high temperature resistant sealant to bolt head to enhance sealing
- Tightening once in 1 month and once in 3 months after commissioning
Option 3: Skin damage repair
Applicable conditions: the damaged area is ≤0.5m², and the skin is not aged in a large area.
Processing steps:
- Cut the damaged area into a regular rectangular opening
- Polish the frame around the repair area to reveal the metallic sheen
- Cut skin patch of the same material (size 50mm larger than opening)
- Apply fluororubber glue and press the repair piece tightly
- Fixed with strips and bolts with spacing between bolts ≤100mm
Scheme 4: Treatment of water leakage in metal expansion joint weld
Processing steps:
- Sand the weld area to remove rust and old solder
- Adopt argon arc welding repair welding, low current, fast welding
- Sand the weld to smooth
- Perform penetration testing to confirm no defects
- Pickling passivation treatment
Note: The corrugated pipe with multiple cracks or repeated cracks should be replaced as a whole and should not be repaired repeatedly.
4. Upgrade scheme: solve the problem from the root cause
If there is repeated water leakage in the same location, it means that the original structure and materials cannot adapt to the current working conditions, and the upgrading scheme should be considered.
1. Material upgrade
| Raw material | Upgrade Material | Expected effect |
|---|---|---|
| Plain silicone rubber skin | Fluorine rubber (FKM) skin | Acid-resistant life increased from 1 year to 3-5 years |
| Carbon steel frame + plain paint | Carbon steel + glass flake coating (≥2mm) | Frame corrosion protection life extended to more than 5 years |
| 304 stainless steel bolt | 316L stainless steel bolts | Cl⁻corrosion resistance, preventing breakage |
| 316L Metal Expansion Joint | Pure titanium TA2 expansion joint | Achieving "zero corrosion, zero leakage" |
2. Structural Optimization
- Add drainage holes: DN25-DN65 drainage holes are installed at the lowest point of the horizontal expansion joint frame, and dust-proof nets are installed
- Install flow guide tube to prevent smoke from directly washing the skin or bellows
- Improve heat preservation: reduce local condensation and dew condensation in flue
5. Preventive measures: Prevent water leakage from happening again
After completing the leakage treatment of the expansion joint of the flue gas channel, the following measures can effectively prevent the recurrence of the problem:
1. Daily inspection
- Check the appearance of the expansion joint every week for water seepage and bulge
- Observe whether the drainage hole is unobstructed and whether the color of the discharged liquid is normal
- Check for loose bolts
2. Regular maintenance
- Full tightening of platen bolts quarterly
- Clean drain holes monthly to prevent clogging
- Inspect frame anti-corrosion coatings semi-annually
3. Operation Control
- Control the temperature increase/decrease rate of start-stop machine ≤3℃/min
- Avoid flue gas temperature below acid dew point for a long time
- Purge flue with nitrogen in time after shutdown
Summary of Processing Process
How to deal with the leakage of flue gas expansion joint can be summarized as a four-step method of "diagnosis → emergency → radical cure → prevention":
| procedure | Core Mission | Key takeaways |
|---|---|---|
| Diagnosis | Determine the location and cause of the leak | Skin seepage? Bolt dripping? Leaky weld? |
| Emergency | Temporary leak plugging without shutting down | Plugging glue stick + clamp, valid for 1-4 weeks |
| radical cure | Permanent repair | Groove filling, skin replacement, repair welding, material upgrade |
| preventing | Prevent recurrence | Regular tightening, smooth drainage, operation control |
sum up
How to deal with water leakage of flue gas channel expansion joint needs to take targeted measures according to the type and severity of water leakage:
- Minor water seepage: cure by groove filling technique during planned shutdown
- Dripping bolts: Tighten or replace stainless steel bolts, and tighten them multiple times after commissioning
- Damaged skin: partial repair or overall replacement of skin
- Weld leakage: repair welding + penetration detection, multiple cracks should be replaced as a whole
- Repeated water leakage: Consider material upgrades (fluororubber skin, titanium expansion joints) and structural optimizations (drainage holes, deflectors)
The fundamental solution to the water leakage problem lies in "anti-drainage combination"-preventing water accumulation through groove filling and structural optimization, discharging the condensate in time through the drainage hole, and selecting corrosion-resistant fluororubber skin or titanium material. One regulated radical repair can ensure that the expansion joint is leak-free for 3-5 years.