TL;DR
A plugged mist eliminator causes liquid carryover and high pressure drop. Trend the differential pressure and plan an inspection or cleaning at the next scheduled outage.
What you might see
- liquid carryover downstream of separator
- differential pressure across mist eliminator rising
- gas flow rate limited by high pressure drop
- liquid droplets observed in downstream piping
Likely causes
Paraffin or asphaltene deposits from crude oil service coating the mesh wires
Corrosion products or scale from the process fluid accumulating in the mesh
High liquid loading event pushing liquid into the mist pad beyond drainage capacity
Mesh damage from a previous slug flow event compressing the pad structure
Required tools
- Differential pressure recorder access
- Gas detector
- PPE: H2S respirator, chemical gloves, face shield
- LOTO kit
- Confined space entry kit
Safety first
- Process separators in oil and gas service contain flammable hydrocarbon gas and liquid under pressure. The full isolation, depressurization, and gas-free procedure is required before any internal access.
- Confined space entry into a separator requires a written permit, atmospheric testing, and a rescue team on standby.
- H2S may be present in a sour gas separator. All personnel in the area must have H2S monitors and appropriate respiratory protection.
Procedure
- 1
Review the differential pressure trend across the mist eliminator section. A rising trend confirms progressive fouling.[1]
- 2
Compare the current gas throughput to the design capacity at the measured pressure drop.[1]
- 3
Inspect the separator from any available external vantage point (manway sight glass) for visible liquid accumulation above the mist pad.
- 4
Plan an inspection during the next scheduled outage. Isolate the separator from the process, depressurize, and open the manway.
Warning: Process separators contain hydrocarbon gas and liquid under pressure. Follow the full isolation, depressurization, and gas-free certification procedure before opening any manway. - 5
Inspect the mist eliminator mesh pad for compression, fouling, or damage.
- 6
Clean the mesh pad with an approved solvent or hot water wash if fouling is soft. Replace the pad if mesh is compressed or damaged.
- 7
After returning to service, verify the differential pressure returns to the clean design value.
Sources
Sulzer Sulzer KnitMesh Process Separator / Knockout Drum general technical documentation, Sulzer
Sulzer KnitMesh process separator general mist eliminator maintenance and inspection procedures (general)
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