1
Seminar on
Metal Detectors in Food Industries
Presented By- Aman Paul M. Tech. Food Technology-Food Chain Management Roll No.-10MTFTFC005
Presented To- Department of Food Process Engineering, SHIATS, Allahabad (U. P.)
2
Contents S.No.
Topic
1. 2. 3.
Acronyms Objective of Seminar Introduction
a. b.
Metal Contaminant Sources of Metal Contamination in Foods Need Need of Meta Metall Cont Contam amin inan ant’ t’ss Detection
6 6
c.
Page No. 3 4 5
8
4. a. 5.
Metal Detection Devices
9
Basic Principle of Metal Detector
10
a. b. c. d. e.
Contaminant Contaminant Factors Detector Factors Installation Factors Product Factors Electronic Factors
6. a.
7. 8.
Factors Affecting Working of Metal Detector
Alignment of Metal Detector with FSMS Plan Action in Case of Deviation
Limit imita ations of Metal Detectors References
12 13 15 17 20 20
21 22
23 24
3
Acronyms
E - Electromagnetic Force Φ - Magnetic Flux T - Time Wb - Webber Sec - Second V - Volt B - Magnetic Flux Density A - Ampere N - Newton m - Meter a - Area μ - Magnetic Permeability μo - Magnetic Permeability of Substance in Space μr - Relative Magnetic Permeability of Medium ρ - Resistivity σ - Conductivity
4
Objective of Seminar
1. Stud Studyi ying ng basi basicc work workin ing g prin princi cipl plee of meta metall detector. 2. Observing the basic causes of false detections by metal detector. 3. How metal metal detecto detectors rs are aligne aligned d with with the HACCP program.
5
Introduction Food technology is moving towards a new era, of food safety. With the increasing zeal of consumer towards food awareness, the safety has become the prime concern of every firm. Implementation of GMP’ GMP’ss and HACC HACCP P prog progra ram m has orien oriented ted the the industry towards a new dawn. Such programs mainly emphasize on the microbial, physical and chemical safety of the processed food stuffs. With the globalization of firms, the continuous exporting and and impo import rtin ing g of food food prod produc ucts ts thro throug ugho hout ut the the worl world d has has beco become me comm common on.. In such such a situ situat atio ion n food safety has become important, not only from consumer point of view but also in tagging up of the firm firm’s ’s glob global al imag image. e. Inte Intern rnati ation onal al stand standard ardss such as ISO 9001 and ISO 22000 aided the global standardization process. Food safety consists of the underling of the food hazards, irradicating or reducing them to acceptance limit and further prevention. The hazards may be physical, chemical or biological. In this seminar we will mostly focus on the detection of physical hazards that can be detected on the basis of there electrical and magnetic properties, i.e. we will talk about the detection of metallic particles in food processing industry.
6
Metal Contaminants
Meta Metall cont contam amin inan ants ts are are phys physic ical al haza hazard rdss that that could cause serious internal damages to the body when accidentally consumed. A particle of size greater than 2mm can cut all the way when it enters the mouth, proceeding from throat to stom stomac ach h and and so on. on. Thes Thesee cuts cuts caus causee inte intern rnal al bleeding and even death. They can enter through various sources in the food.
Sources of Metal Contamination in Food
There are many channels the metal contaminants contaminants can follow to enter the food. Few of them are listed below:1.
Raw Material- The raw material can itself be contaminated at the primal level. The cont contam amin inan ants ts can can ente enterr the the chai chain n whil whilee the the processes of harvesting, threshing, drying, stor storin ing, g, etc. etc. are are bein being g carr carrie ied d out. out. Talk Talkin ing g about the Indian scenario, there are no check points in the farms as such. This makes the post harvest activities of raw material really prone to metallic contamination.
7
2.
3.
4.
Transportation- Fresh produce of fruits and vegeta vegetabl bles es are usua usuall lly y trans transpo porte rted d in crates crates which may be open and exposed to the environment to facilitate metabolic activities, this this incr increa ease sess the the risk risk of meta metall llic ic contamination in the food. Processing- During processing the metal contami contaminat nation ion can occur occur through through proces processing sing equipments, exposed lines, etc. The food contact surfaces of the equipments may serve as a source of metal inoculation in the food product. Packaging- Packaging infrastructure is a complex unit in itself, which has many potential areas where metal contamination can occur. For example, any screw can fall from the equipment into the product. This is the most common source of contamination from the packaging unit, as the machine is contin continuo uous usly ly vibrat vibratin ing g so there there are are chan chances ces that any of the screw loosen up and contaminate food.
8
Need of Metal Contaminant’s Contaminant’s Detection
The The foll follow owin ing g reas reason onss nece necess ssit itee the the need need of metal detection:1.
2.
3.
Social Responsibility- As we have seen in the above article that the metal contaminants when consumed can even cause death. So it is a social responsibility of every food tech techn nolog logists ists to excl exclud udee all all such uch contaminations for humanity. Consumer Safety- Consumer is investing his trust in the company by buying the product, and if his trust is lost it will let him move towards jurisdiction.
loball playe layers rs often ften loos loosee Firm Firm’s ’s Imag Imagee- Globa there image if they encounter any food safety rem remarks arks on there here bran brand, d, thes thesee coul could d even even uproot there international brand image.
9
Metal Detection Devices The most commonly used metal detection devices are:1. Sifters 2. Metal Detectors 3. X-rays Sifters are used to eliminate particles of size either greater than or smaller than that of food. But sifters are ineffective when the contaminations are inside the food stuff. This makes there use very rare in the industry. X-rays have now become old fashioned. As the debate regarding exposure of food to irradiation is still incomplete and safety concern of food irradiations are highlighted the X-rays have departed there way out of the food industry as a potential metal detection device. Metal detectors working on the electromagnetic principle have now replaced sift sifters ers and and X-ray X-ray util utiliz izin ing g devi device ces. s. Thes Thesee meta metall detectors have now become the soul of every Food Safety Management System (FSMS). Now lets see how these metal detectors really function and the factors affecting there working.
10
Basic Principle of Metal Detector
1. Metal detector works on the “Faraday’s Law Accord rdin ing g to of Electroma Electromagnet gnetic ic Induction Induction”. Acco this law “whenever whenever the magnetic magnetic flux linked with an electric circuit is altered and electromagnetic ”. force is induced in the circuit ”. E = - dΦ/dT
Unit of E = Wb/Sec (Volts)
Here Here the the Magne (Φ) is the the magn magnet etic ic Magnetic tic Flux Flux (Φ) lines passing through a given area. Φ = B.a.cosϴ Wher Wheree “ϴ” is the angl anglee betwe between en a norma normall area area “a” and direction of B. 2. Construction- The The basi basicc cons constr truc ucti tio on of a metal detector is shown below. Transmitting coil Tx(One)
Metal Strike Zone Receiving coil R x(Two)
11
The transmitting coil generates a high frequency magnetic field, while the two receiving coils pick up the the osci oscill llat atin ing g fiel field. d. The The rece receiv ivin ing g coil coilss are are connected to display and alarm. 3. Schematic Block Diagram Signal Generation
Comparison with Threshold
Alarm if Signal >Threshold
Display Signals
4. Functioning a. In a normal state magnetic field coupled is equally to both coils. Therefore a balanced condition exists so no signal is generated on display. b. When the contaminant enters, it distorts the magnetic field, which upsets the balanced condition and a signal is detected, which is displayed on the display-screen connected to the receiving coil. c. This signal is compared to the threshold, if it is above the threshold, the alarm rings.
12
Factors Affecting Working of Metal Detector The following factors affect the working of metal detector devices:1). Contaminant Factors a. Material b. Size and Shape 2). Product Factors a. Moisture b. Undried/Lumpy c. Recipe (Minerals) 3). Installation Factors a. Vibration b. Clearance c. EM/RF Interferences d. Metal Free Zone e. Earthing 4). Electronic Factors a. Threshold b. Signal Processing c. Calibration
13
5). Detector Factors a. Position b. Orientation c. Aperture Size d. Head Frequency Let’s discuss every factor one by one.
Contaminant Factors
a. The most important factor affecting working of metal detector is the contaminant material . The key properties essential for metal detection are:1.
Electrical Conductivity- is the ability of a body to conduct electricity.
σ = 1/ρ Magnetic Permeability- Measure of the ability of substance to support the formation of magnetic field. μ = μo x μr 2.
The magnetic properties play a more dominant property in detection.
14
Below is the decreasing order of conductivity of some metals: Good Conductors ( σ) Silver Copper Gold Aluminium Zinc Nickel Tin Chromium Bad Conductors Lead ( σ) Mercury
Property Matrix
15
b. Another factor that affects the working is size and shape of the contaminant material. It is usually observed that spherical objects are detected with more difficulty and wires are detected easily.
Detector Factors
a. Orientation effect -
1. Easy for non-ferrous 2. Difficult for ferrous
1. Easy for ferrous 2. Difficult for nonferrous
16
b. Position effect -
At centre magnetic field is weak and objects are difficult to detect
At sides the magnetic field is the strongest and easily detected
d.
Aperture size- Lower the aperture size, higher is the sensitivity of metal detector and vice-versa.
Aperture Size
17
e.
Head Frequency-
Higher the Frequency, Higher the Sensitivity
High Rates of False Rejectio ns
Lower the Frequency, Lower the Sensitivity
Detects Stainless Steel
Installation Factors
Metal Free Zones- This place a very important role in the proper functioning of the metal detector. The Metal free Zones are classified in two categories:a.
MFZ 1 (For non moving metal particles) MFZ 2 (For moving metal particles)
18
MFZ 1 (For non moving metal particles)
MFZ 2 (For moving metal particles)
19
b. Vibrations- High level of mechanical vibrations causes an increase in the number of false strikes. c. Clearance- Here clearance can be detected as the vertical distance from throat to chute. It should be at least 10mm. Clearance is necessary for performing of validation test and for expansion/movement of flexible product chute. d. Electromagnetic/Radio Frequency Interference
Air-Borne Disturbances in Environment
Another Detector (AM Receiver)
Inverter Motors, Clutch/Brake and Power Cables
EM/RF Interfere nce
Mobile Phone and Walkie Talkie
Fluorescent Lamp
20
Note- Metal detectors are very sensitive to AM radio receiver.
Product Factors a.
Wate terr is a good con conducto ctor of Moisture- Wa electricity. It may cause a false metal strike, if moisture is present in high concentration. Rejected products may test negative after a few days as the particles could have been broken or product dry up. So it detection gets difficult.
b. Recipe- If the product is rich in mineral matter, faulty metal detections often appear at a fast rate.
Electronic Factors
Factors such as detection threshold, fault in signal processing system and calibration error also plays important role in the proper functioning of metal detectors.
21
Alignment of Metal Detector with FSMS Plan In current scenario, metal detector has become an active part of all FSMS plans. Metal detector has turned out into a CCP essential. It is used to track particles of size more than 1mm. The The onli online ne test testin ing g of meta metall dete detect ctor orss shou should ld be carried out in the following manner:-
Hazard - Metal Particles 2. Location- All filing lines 3. Specification- Correct functioning of metal detection system and should detect operating limit defined by the factory. Critical Limit is SS 2.0mm. Note- The test piece should be spherical and certified by the supplier for both operational and critical limits. 1.
CCP monitoring procedure:1. Check proper functioning of metal detector at least once per shift with standard spherical test pieces of operational limit. 2. Ensure that the product incriminated by the metal detector is kept separately and sorted by offline metal detectors.
22
3. Metal retrieved retrieved from the rejections rejections are retained and root cause analysis is done. 4. Record for online testing, offline testing and retrieved metal pieces. 5. In case of increasing number of metal retrievance proper correcting action should be taken by the production/engineering section. Action in Case of Deviation
1. Incas Incasee the the meta metall dete detecto ctorr fail failss in the the rout routin inee check, than stop the line. 2. Check Check the detect detector or with 2mm 2mm SS, if it passes passes than release the product since last check and recalibrate the detector. 3. If dete detect ctor orss fails ails with ith 2mm SS, SS, block lock the the product since last check. 4. Pass Pass the produc productt through through offlin offlinee metal metal detector. 5. Incinerate Incinerate the rejections rejections and rework the unrejected ones.
23
Limitations of Metal Detectors
Limitations
Sensitivity
Can only detect metal contaminants
To be detected the metal diameter should be greater than 1mm
Installation
Needs a bigger vertical space
Performance is affected by noise and vibrations
24
References 1.
www.metaldetection.com/subtwo140.html
2.
www.wikipedia.en/metaldetector.html 3.
Gaur, R.K. and Gupta, S.L. 2003. Engin Engineer eering ing Phys Physics ics.. Dhanp Dhanpat at Rai Rai Publications.
4. Pott Potter, er, N.N. N.N. and and Hotc Hotchk hkis iss, s, J.H. J.H. 2007 2007.. Food Science. CBS Publishers & Distributors. 5.
Alli, I. 2004. Quality Assurance:Principles and Practices. CRC Press LLC.
