If your bag filter is leaking water or air, the issue is typically caused by one of three main problems:

1. Seal failure (most common – over 80%)

2. Filter bag damage

3. Housing or connection damage

The correct troubleshooting approach is:

Depressurize first → Inspect externally → Then check internal components → Fix from simple to complex

This step-by-step guide helps you quickly diagnose and repair the issue safely and efficiently.

1. Safety First: Shutdown and Depressurize (Mandatory)

Before any maintenance:

• Close the inlet and outlet valves

• Cut off media flow

• Open the vent and drain valves to fully release internal pressure

• Confirm zero pressure before opening the lid

• When handling corrosive or toxic media, wear PPE and discharge to a safe area

⚠ Never open a pressurized bag filter.

2. Locate the Leak: External vs Internal

A. Visible External Leakage

Check the following areas first:

1️⃣ Top Cover / Quick-Open Closure

• Water seepage or air leakage around the gasket

• Usually indicates O-ring or gasket failure

2️⃣ Flange or Threaded Connections

• Inlet/outlet ports

• Drain ports

• Pressure gauge or sight glass connections

• May be caused by loose bolts or damaged gaskets

3️⃣ Filter Housing Body

• Moisture marks, bubbles, or visible cracks

• Possible corrosion, welding defects, or pinholes

B. Internal Leakage (Not Immediately Visible)

Look for operational symptoms:

• Sudden drop in differential pressure

• Cloudy filtrate or unfiltered particles downstream

• Dust carryover (for air filtration systems)

• Abnormal discharge from vent

These signs often indicate:

• Broken filter bag

• Improper bag installation

• Seal bypass

3. Component-by-Component Troubleshooting

I. Sealing System Issues (Over 80% of Leaks)

1️⃣ Lid / O-Ring / Gasket Failure

Common Problems

• Aging or hardened rubber

• Cracks or deformation

• Improper installation

• Dirt in sealing groove

• Uneven bolt tightening

Solution

• Clean the sealing groove thoroughly

• Remove burrs or debris

• Replace with correct material:

  • NBR (oil resistant)

  • EPDM (water/chemical resistant)

  • FKM/Viton (high temperature/corrosive)

• Apply light silicone grease (avoid twisting)

• Tighten bolts diagonally and evenly

• Follow manufacturer torque specifications

2️⃣ Filter Bag to Basket / Tube Sheet Seal

Common Problems

• Bag collar not seated properly

• Loose retaining ring

• Incorrect bag size

• Deformed basket

• Burrs cutting into sealing ring

Solution

• Remove and inspect the basket

• Check for deformation or sharp edges

• Insert filter bag vertically

• Ensure collar sits flush against sealing surface

• Lock retaining ring evenly

• Use correct bag dimensions (diameter + length match housing)

II. Filter Bag Damage (Primary Cause of Internal Leakage)

Symptoms

• Sudden pressure drop

• Dirty filtrate

• Dust carryover (air system)

Causes

• Excessive differential pressure (>0.1 MPa)

• Flow shock / water hammer

• Corrosion or chemical incompatibility

• Abrasion from metal basket burrs

• Improper installation

Solution

• Replace damaged filter bag immediately

• Repair small tears only temporarily

• Control operating differential pressure ≤ 0.1 MPa

• Replace clogged bags in time

• Smooth and polish basket edges

• Open inlet valve slowly to avoid shock impact

III. Housing and Connection Damage

1️⃣ Loose Flange or Threaded Joints

Fix

• Tighten bolts evenly in cross pattern

• Replace damaged flange gasket

• Reapply PTFE tape or anaerobic thread sealant

2️⃣ Cracks, Corrosion, Pinholes in Housing

Minor Damage

• Carbon steel: welding repair

• Stainless steel / plastic: epoxy or industrial sealing compound (temporary)

Severe Damage

• Replace cylinder shell or head

• Replace entire bag filter unit if structural integrity is compromised

4. Post-Repair Pressure Test (Essential Step)

After reassembly:

1. Tighten all fasteners properly

2. Slowly increase pressure to 1.25 × rated pressure

3. Hold for 10 minutes

4. Inspect all sealing surfaces carefully

5. Resume normal operation and monitor:

   • Differential pressure

   • Filtrate clarity

   • Air purity (gas systems)

No leakage = system ready for service.

5. Preventive Maintenance to Avoid Recurrence

✔ Replace sealing elements every 3–6 months
✔ Replace filter bags when ΔP reaches 0.05–0.1 MPa
✔ Avoid overpressure and overtemperature
✔ Use compatible materials for chemical media
✔ Install bags correctly and tighten bolts diagonally
✔ Prevent sudden valve opening (avoid hydraulic shock)

Conclusion

When a bag filter leaks water or air, the problem is usually not complicated. In most cases, it is a sealing issue, followed by filter bag damage, and finally housing defects.

By following a structured troubleshooting process:

Depressurize → Inspect external seals → Check internal components → Repair → Pressure test

You can restore the system quickly and ensure long-term stable operation.