Coalescing Filters in Heated Sample Lines — Choosing Element and Housing by Temperature
Heated sample lines keep water and hydrocarbons above their dew point so the analyser sees the real composition. Standard coalescing elements are rated to +150 °C. Above that, silica-bonded elements such as RF-CS-12057-HE are used — and the housing and seal limits decide how hot the filter stage can really run.
Recognise the Symptoms
- Coalescing elements in heated lines lose strength, discolour or release fibres
- Binder odour or deposits downstream of the filter after heating up
- Condensate forms in the filter housing because it is not heated with the line
- Membrane separators fail in hot sample streams
- Seals harden or leak after operation at high temperature
Root Causes
Standard coalescing element above its rating
standard elements are specified from −50 to +150 °C
Housing or seal limit ignored
a silica-bonded element does not raise the limit of the housing (stainless steel 200 °C) or the seal
Unheated filter housing in a heated line
the housing becomes the coldest point and condenses the sample
Membrane separator placed in the hot section
RF-M-GMS170 is rated to 100 °C
Cold spots at fittings and drains between line heating and housing
Diagnostic Checklist
- 1Measure the real sample temperature at the filter, not only the line set-point
- 2Up to +150 °C: RF-C-12057-HE (borosilicate glass microfibre, 99.99 % @ 0.01 µm)
- 3Above +150 °C: RF-CS-12057-HE (silica-bonded, up to 500 °C) — the housing limit of 200 °C for stainless steel and the seal limit apply
- 4Keep the filter at line temperature: insulate or use the heatable RF-HH-122ST housing (¼″ NPT side, 2 bar, 200 °C)
- 5Place the membrane separator only where the sample is below 100 °C
- 6Change coalescing elements every 3 months or earlier when the differential pressure rises
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