Additional Test for the Quality Control of OSDs

Preventing Metal Contamination

  • Metal contaminants are mostly classified as ferrous (magnetic), nonferrous (highly conductive nonmagnetic metals such as copper, aluminum, and brass), and nonmagnetic stainless steel. The easiest to detect are ferrous contaminants, while the most difficult to locate are the 300 series stainless steel contaminants (such as those commonly used in the pharmaceutical processing and packaging machinery) since the material is not particularly conductive or magnetic.

Characteristics of a Metal Detector

  1. A metal detector features an aperture or tunnel, through which the product passes and a user interface–control system, which is generally housed separately but may be integrated in some models.
  2. The aperture is sealed to protect the components inside and is lined with a nonmetallic material.
  3. Within the aperture, a transmitter coil emits a radio frequency signal and generates an electromagnetic field.
  4. Receiver coils on either side of the unit detect disturbances in the field caused by magnetic or electrically conductive material. This configuration often is described as a “balanced coil” system.
  5. The size, shape, and orientation of the particle and type of material determine the strength of the signal.
  6. Ferrous contaminants generate the strongest signal, followed by nonferrous and nonmagnetic stainless steel. Spherical particles are the easiest contaminants to identify. Wire-shaped contaminants can be extremely difficult to detect because the signal varies depending on the orientation of the metal piece.


  • Phasing is the process which differentiates the signals generated by the product and any contaminants.

Why Phasing OCCURS?

  • To correct errors during detection which becomes complicated when the product creates a magnetic or conductive signal for which the unit must compensate.
  • Wet products are more challenging to scan than dry products.
  • Phasing differentiates products to be classified as dry (nonconductive) or wet (conductive).

Preventing Metal Contamination

  • Unit sensitivity is proportional to the size of the aperture (i.e., a small size indicates higher sensitivity). A unit with a 50-mm-high aperture can locate ferrous and nonferrous contaminants in dry products as small as 1 mm, but a 200-mm-high aperture will limit sensitivity to a 2-mm fragment.

  • There are several metal detectors which are specifically designed for the examination of tablets and capsules. These detectors are typically positioned to check product in either pre- or post-filling, but sometimes a unit is already installed to inspect the product before filling and another unit is used to double check filled containers. In some cases, metal detectors may be integrated with checkweighers to provide another quality control function. Metal detectors are designed to be integrated with tablet presses while dedusters are built to comply with strict hygiene standards.

1. Safeline PharmX, Safeline Metal Detection, Tampa, FL

  1. This detector has a detection head mounted on three axes to be easily adjusted to the tablet press outlet without tools.
  2. Product contact parts are constructed from mirror-polished stainless steel and food-grade plastic and quickly disassemble for cleaning.
  3. A variety of aperture sizes and reject mechanisms accommodate a wide range of pill sizes and help provide throughput rates < 10,000 tablets/min.
  4. A reject confirmation feature alerts the operator if a contaminated product is not ejected.
  5. Should the power fail, the diverter automatically switches to reject mode to ensure no off-spec product slips by.
  6. Finally, validation software notifies operators when testing should be performed, and a self-check capability provides a warning if sensitivity drifts outside set parameters.

2. Phantom Pharmaceutical Metal Detector, Fortress Technology Inc., Scarborough, ON

  1. Offers full validation documentation and can run multiple search heads from a single microprocessor controller.
  2. This controller interfaces with other equipment, accommodates data logging, and holds product readings in memory for quick setup.
  3. An automatic on the-fly or one-button “learn” function compensates for readings generated by the product itself and simplifies changeover and a digital signal processor delivers the highest level of sensitivity.

3. Loma Pharmaceutical System, Loma Systems, Carol Stream, IL

  1. A failsafe reject mechanism happens whenever the easily dismantled product chute rejects the device to characterize another metal detector, which is capable of checking <10,000 tablets/ min

4. E-Z Tec Pharmaceutical Metal Detector, Eriez, Erie, PA

  1. This detector has an expedited start-up feature that allows operators to pass through and test sample product in production within five minutes.
  2. Start-up efficiency is also supported by an easy clean chute to speed changeovers and the position of the detector’s head, which is fixed at a slope of 30° to eliminate lengthy timing adjustments of downstream reject equipment.

5. Goring Kerr DSP IP, Thermo Goring Kerr, Minneapolis, MN

  1. A metal detector which is capable of withstanding high-pressure wash-down conditions.
  2. The detector”s design eliminates the most water sensitive areas of standard detectors, which usually must be covered during wash-down and then cleaned separately by hand.
  3. Water-resistant features include an etched steel-membrane keyboard, an integrated detector head and control box, and flanged seals which are designed to deflect the water.
  4. Integrating the power supply and input-output into the detection head not only eliminates the need for a control box and attendant wiring between the two, but also results in a more compact unit.

6. Autosearch II Plus Ferrosearch, Cintex of America Inc., Kenosha, WI

  1. Locating ferrous contaminants in foil packaging is possible with some units, which actually magnetize the contaminant to enable identification.
  2. This can automatically adjust sensitivity to accommodate production variations, eliminate false rejects, and automatically recalibrate for new products to reduce changeover and setup time.


  1. X-ray inspection systems can identify metal contamination and fragments of materials such as glass or rubber.
  2. X-ray systems also can check product count, product size, product mass, container fill level, product–package condition, and package insert presence.

A tablet deduster is a machine that removes dust from newly pressed tablets either by vibration or air pressure. The process usually happens immediately after a tablet press.

Why there is a need of Tablet Deduster?

  1. When compressing powders into pharmaceutical and nutraceutical tablets, dust sometimes becomes a byproduct, adhering to the tablets as they exit the tablet press.
  2. The gap between the press punches and dies can allow burrs to forms around tablet edges. Both the powder and the burrs lead to unwanted dust in downstream processes.
  3. Removing the dust as the tablets leave the press allows process and packaging equipment to work more efficiently with less maintenance and keeps the work area cleaner.

Six primary requirements to use a tablet deduster:

  1. Identify the minimum and maximum tablet sizes. The size, along with the speed at which they enter the deduster, determines the machine volume required to transport and dedust the tablets effectively.
  2. Know the maximum output of the tablet press for each size of the tablet made. This information allows the company to determine the deduster capacity the operation requires.
  3. Know the tablet’s hardness and the nature of the dusts since tablet hardness factors into deduster size.

    *** Chewable or effervescent tablets, for example, may require very different dedusters. Soft tablets, such as effervescents, could be damaged if the deduster must operate at its capacity limit. As for the dust, is it hazardous or toxic? If so, the deduster may need dust-tight containment to prevent exposing press room personnel. It may also require a wash-in-pace or wet-in-place system to prevent worker exposure when the equipment is cleaned following a batch.

  4. Determine whether a metal detector should accompany a deduster. A metal detector requires roughly 10 inches of height, which must be accounted for when specifying the deduster.
  5. Decide how many containers will collect the dedusted tablets. If they must be collected in two or more containers, a diverter will be needed, which adds to the overall height, which must be taken into account.
  6. Determine the outlet height of the press and the inlet height of the collection container(s). To calculate this, measure the distance from the floor to the bottom of the tablet outlet chute and from the floor to the top of collection container. These two distances determine the deduster’s conveying height – the height required to reach the collection container.
Horizontal, Vertical or Brush Type

Horizontal dedusters

As the tablets travel that distance, vibration dislodges the dust, which drops through the perforations and is pulled away by the suction of a dust collector. Some horizontal dedusters direct compressed air into the tablets. This helps dislodge the dust and keeps it airborne, enabling the dust collector to capture it more efficiently.

• Drawbacks for Horizontal Dedusters

  • They can be noisy;
  • Tablets spend only a short time on the perforated plate/tube, and a short residence time may limit the equipment’s efficiency when dedusting the products.
  • Their big footprint may require more space inside the press area or press suite than is available. They can use only small tablet collection containers – 2 feet tall or less.

Vertical dedusters

• Downward conveying

  • An inexpensive and older style of deduster.
  • Tablets enter at the top, descend through several perforated plates, then bounce around until they find the exit and drop to the next plate.
  • After passing from the plate to plate, the tablets drop out neat the machine’s base.
  • It includes a compressed-air blow-off capability to boost dedusting efficiency.

• Upward conveying

  • Uses a helical perforated tray fixed to a central column.
  • Some units use a blast of air to assist in dedusting and to keep the dust airborne, which makes it easier for suction from a dust collector to extract the dust.
  • The big advantage for upward conveying vertical dedusters is their small footprint, which minimizes the loss of production space.

Brush Type

  • Available in horizontal and vertical configurations, also has a low upfront cost.
  • They compromise a helically wounded brush located inside a stainless steel tube – similar to a screw conveyor – driven by a variable-speed motor.
  • Uses plastic brushes that can impart an electrostatic charge to the product. The brushes also wear, which raises the question of where the residual particles and broken brush fibers go.