Vessel diameter and manhole
State the vessel and manhole diameters. We use these to specify a one-piece pad or overlapping segments for assembly inside the vessel.
dwg AVX-1801 · Products
Demisters & mist eliminators
Every micron engineered. Every millisecond protected.
Definition
A demister is a knitted wire mesh pad in a vessel or column that separates entrained liquid droplets from a rising gas or vapour stream. Droplets contact the wires, combine into larger drops and drain against the flow. Separation depends on pad condition and on gas velocity remaining within the design range.
Also known as: mist eliminator · demister pad · knitted mesh pad · droplet separator · vapour-liquid separator
Liquid carry-over can result from a pad sized for different operating conditions, blocked by solids or replaced without checking the specification. Possible effects include compressor fouling, wet product and reduced column performance. The cause needs to be assessed against the current process conditions.
We supply demister pads to vessel dimensions, with the specified alloy, support grids and hold-down bars. Send vessel diameter, operating pressure and temperature, gas rate and liquid load. We can work from an existing drawing or prepare one from the application data.
Pads larger than the manhole are supplied in overlapping segments for assembly inside the vessel. Grids, rings and hold-downs use the same alloy as the pad unless the specification requires otherwise.
Where it is used
- Separator vessels and knock-out drums
- Distillation and absorption columns
- Evaporators and flash vessels
- Scrubber outlets and vent stacks
- Compressor suction protection
- Steam and gas conditioning
| Property | Value |
|---|---|
| 100–300 mm (standard range) | |
| 0.10–0.28 mm | |
| 80–192 kg/m³ | |
| 97–99 % | |
| typically from 3–5 µm — confirmed per application | |
| 0.07–0.11 m/s (Souders–Brown) | |
| typically < 250 Pa | |
| one piece or sectioned for manhole entry |
Values shown are standard industry ranges for knitted mesh demister pads, not a commitment. The exact specification — pad style, wire diameter, density, thickness and alloy — is confirmed per application after technical review of your process data.
What to specify
Gas velocity window
Gas velocity must stay within the design range. Below that range, separation may be insufficient; above it, liquid may be re-entrained. Provide gas rate and density for sizing with the Souders-Brown relation.
Liquid load and fouling
Liquid load, solids and the required droplet separation affect wire diameter and pad openness. Coarser, more open pads can suit dirtier service; finer constructions can improve fine-droplet capture. If a pad blocks, review these conditions before specifying a replacement.
Alloy and temperature
316L is used for many duties. Chlorides, sour service and elevated temperatures may require Duplex, Inconel, Monel or Hastelloy. State the medium and design temperature so suitability can be checked.
Materials & variants
Standard in 304 and 316L. Also supplied in Duplex, Inconel, Monel, Hastelloy and, for lower-temperature or corrosive duties, in polypropylene or PTFE. Support grids, rings and hold-down bars are matched to the pad alloy. Availability and lead time for the higher alloys are confirmed at quotation.
Frequently asked questions
What is the difference between a demister and a mist eliminator?
In practice, none. "Demister" and "mist eliminator" describe the same knitted wire mesh pad. Vane packs and cyclones are also called mist eliminators, so if the distinction matters in your specification, say which construction you mean.
How do I know my demister pad has failed?
Two signatures. Rising pressure drop across the pad with no change in throughput points to blinding. Liquid appearing downstream at unchanged pressure drop points to re-entrainment or a bypass around the pad, usually a hold-down that has worked loose.
Can you supply a pad for a vessel that is larger than the manhole?
Yes. The pad is supplied in segments with an overlap and assembled inside the vessel. Give us the manhole diameter with the vessel diameter and the segmentation is worked out before anything is made.
Which alloy should I specify?
316L is the default. Chlorides, sour gas or higher design temperatures usually move the choice to Duplex, Inconel, Monel or Hastelloy. Send the medium, concentration and design temperature and we come back with an alloy and the reason for it.
What data do you need for a quotation?
Vessel and manhole diameter, operating pressure and temperature, gas flow and density, liquid load, and the alloy or the service that decides it. A sketch of the existing pad and its support ring helps; a drawing helps more.
Do you also supply the support grid and hold-down bars?
Yes, as one scope. Pad, support grid, hold-down grid and the fixings are supplied together in matching alloy, so nothing on site has to be improvised during a shutdown.
How fine a droplet can a demister remove?
Knitted mesh pads typically start to work from around 3-5 µm, with the achievable figure depending on gas velocity, liquid load and pad style. The rating for your duty is confirmed per application; a number quoted without the process data behind it is not worth much.
RFQ
Send a drawing or ask us to help create one.
Share your specifications, sketch or description using this form. You will receive a personal response within two business days.