How do I select the capacity of the deioniser for line speed and belt width?

How many ions per metre and second. A simple calculator for selecting deionisation for your line

A well-chosen deioniser (ioniser) must 'keep up' with the material: the charge neutralisation time must be shorter than the time the strip is in the ion zone. Below you will find a practical framework: what data to collect, how to calculate the time of interaction, when to choose an ionising strip and when to choose ionised air knives/curtains, how to position the devices over the width, and three ready-made calculation examples.

What data do you need to have to start?

• What is the line speed in m/min or m/s?

  Write in both units: v [m/s] = v [m/min] ÷ 60. For 120 m/min → 2.0 m/s.

• What is the width of the tape and how many sides do you want to neutralise?

  Specify the net width (material area), indicate whether you are operating from one or both sides.

• At what distance from the material can you mount the unit?

  Measure a realistic installation distance (e.g. 50, 100, 150 mm); the closer, the shorter the charge fade time.

• What kind of material is it and what kind of loading problems does it have?

  Foils, paper, non-wovens, laminates? Note areas of sparking, dust attraction, roll sticking, printing/cutting problems.

Key selection principle: neutralisation time vs. impact time

• How to count the interaction time in the ion zone?

  t_dwell = L_eff / v, where L_eff is the effective length of the ionisation zone in the direction of belt movement, and v is the belt speed.

• How to estimate L_eff for different solutions?

  For a slat without blowing, the following is a simplified assumption L_eff ≈ 2×d (d - distance to material). For blow moulding/curtains L_eff ≈ 3-4×d thanks to the 'pull' of ions through the airstream.

• What condition should the deioniser specification meet?

  t_decay(spec) ≤ 0,5 × t_dwell at your distance d (reserve for humidity fluctuations, ageing and dirt).

Selection of device type for speed and width

• When is a non-blowing ionising strip sufficient?

  For low/medium speeds (up to ~80-120 m/min) and distance ≤100 mm at widths of up to ~1.6 m, when the problem is mainly dust attraction and 'pinching'.

• When do you need a blow bar or ionised air knife/curtain?

  At higher speeds (≥120 m/min), larger installation distances (≥100-150 mm), when discharging through thicker air/dust layers or when you want to blow off dust at the same time.

• With very wide bands, is it worth using several sections?

  Yes - for width >1,8-2,0 m consider two slats in series (increase in L_eff) or two opposite (both sides), alternatively modular curtains with even blowing over the entire width.

How do you "recalculate" the air with ionised knives/curtains?

• How do you estimate the required air volume?

  For the gap s and widths W and exit velocity v_air:
  Q = v_air × (W × s). Example: W=1,2 m, s=1 mm (0.001 m), v_air=30 m/s → Q ≈ 0.036 m³/s ≈ 130 m³/h.

• How do I choose the air jet speed?

  Startup 20-40 m/s at the knife outlet ensures ion delivery and "breakthrough" of the boundary layer on a fast web. Increase if tape thick/"sticky" or distance large.

• Is compressed air or a blower better?

  The blower is usually cheaper energy for continuous operation and wide belts; leave compressed air for local nozzles/nozzles.

Placement and geometry - where and at what angle?

• Does the angle of the slat make a difference?

  Yes - set 10-20° "upstream" relative to the movement of the tape so that ions "flow" along the surface. Avoid shading (rollers/shields).

• Where to place deionisers on the line?

  Minimum: before winding, upon unwinding and in front of critical zones (printing, cutting, lamination). With plywood/dust catching - just before the process.

• Do two slats in a row improve the outcome?

  Yes - second slat 150-300 mm behind first increases L_eff and reduces the residual load on high-speed lines.

Simple calculation examples - how to use the rules in practice?

• Example A: 120 m/min, 1.2 m wide, d = 100 mm - what to choose?

  Data: v=2.0 m/s; L_eff≈2×0.1=0.2 m → t_dwell=0.2/2.0=0.10 s. Require t_decay ≤ 50 ms at 100 mm. One strip without full-width blowing is usually sufficient; if loads are returning - add a second in line.

• Example B: 150 m/min, 1.2 m wide, d = 150 mm, dust - what to do?

  v=2.5 m/s; air curtain: L_eff≈3×0.15=0.45 m → t_dwell=0.45/2.5=0.18 s → t_decay ≤ 90 ms. Match the ionised knife with the Q≈130-200 m³/h (see formula) and an outlet of 20-40 m/s.

• Example C: 300 m/min, 1.6 m wide, d = 150 mm - "high speed" line?

  v=5 m/s; strip without blowing: L_eff≈0.3 m → t_dwell=0.06 s → t_decay ≤ 30 ms (difficult). Solution: two curtains (up/down) or two slats in a row with blowing, possibly modular sections in width.

Controlling the effect - how to measure and control?

• Is online measurement of the load required?

  Yes - the electrostatic field sensor upstream and downstream of the ionisation zone will show the real drop (target: as close to 0 V as possible with process tolerance).

• Should the ion balance be adjustable?

  Choose systems with automatic balance (± a few tens of V), which compensate for fouling of emitters and changes in conditions.

Scaling in width - how do you cover the whole tape?

• How do I match the length of the skirting board to the width?

  The strip should cover full width plus a 20-50 mm allowance on each side to avoid edge loading.

• Is it worth segmenting in very broad applications?

  Yes - controlled sections (e.g. 2×800 mm instead of 1×1600 mm) facilitate servicing and maintain an even ion density.

Environmental conditions and service - what affects effectiveness?

• Do humidity and draughts change the outcome?

  Yes - low humidity (in winter) increases charges; side drafts 'blow off' ions. Screen the zone and ensure stable conditions.

• How often should the emitters and air filters be cleaned?

  Depending on the dust - often every 1-4 weeks. Dirt = longer t_decay and greater offset.

• Does deionisation generate ozone and is it a problem?

  Minimally - with the correct distance and flow. Provide ventilation and stick to the manufacturer's recommendations.

Common mistakes - what to avoid?

• Can you mount 'where it fits' without counting t_dwell?

  No - too short a zone at high speeds is a guaranteed inefficiency.

• Will a single strip solve every problem on a wide strip?

  Not always - above ~1.8m or at 300m/min you usually need a both sides and/or blowing.

• Is increasing the voltage or flow 'blindly' a good idea?

  No - without measuring you can only shift the problem (ion offset, edge charges, dusting).

Checklist before selection - 5 questions to tick off

• Have you counted t_dwell and compared it with the device's t_decay spec?

• Have you taken into account the real mounting distance and shading?

• Do you have a plan to cover the entire width (one/two pages, sections)?

• Do you know what Q and v_air you need at the curtain/knife?

• Have you made provision for online measurement and a cleaning schedule?

FAQ - quick answers

• At 60 m/min, is a non-blowing bar sufficient?

  Usually yes, if d ≤ 100 mm and width ≤ 1.6 m and no intense dust.

• Is it necessary to neutralise both sides of the material?

  It is worthwhile when charges return after contact with rolls or when laminating/printing on both sides.

• Does increasing the mounting distance always worsen the effect?

  Yes - t_decay increases with distance; compensate by blowing or extending L_eff (second strip in series).

Summary

Deionisation selection is a fitting the neutralisation time To impact time and even width coverage. Count t_dwell = L_eff / v, require t_decay ≤ 0,5×t_dwell at your distance and decide: strip for slower/medium lines and short distances, curtain/blowing knives for speed and long distances or when dust needs to be blown off. Scale in width (sections/two sides), add on-line measurement and emitter service - and you have a stable process with no dust attraction, roll sticking or ESD discharge.