der=0 cellpadding=10 cellspacing=0 width=100%>Yahoo! is not affiliated with the authors of this page or responsible for its content.
M e t a l D e t e c t i o n Reduction of Metal Contamination
Building an Effective Programme
M
e
t
a
l D
e
t
e
c
t
i
o
n
For more information
www.mt.com/metaldetection
Mettler-Toledo Safeline Ltd.
Montford Street
Salford
M50 2XD
UK
Subject to technical changes
©06/2007 Mettler-Toledo Safeline Ltd
Printed in UK
SLMD-UK-MDG07-EN-0807
SAFELINE
Metal Detection The information contained in this manual is provided to assist producers in developing and implementing an effective metal detection programme. METTLER
TOLEDO SAFELINE LIMITED does not warrant the accuracy or applicability of the information contained herein and as such is speci cally not responsible for
property damage and/or personal injury, direct or indirect for damages and/or failures which may be caused as a result of using the information provided. i
Table of Contents

Page
Number
Introduction








2
Metal Detection System Selection
Chapter 1 - Introduction to Metal Detection




4
Chapter 2 - Key Design Features





10
Chapter 3 - Factors Limiting Sensitivity





14
Chapter 4 - Systems Design and Applications




20
Building an Effective Programme
Chapter 5 - Reasons for a Metal Detection Programme



30
Chapter 6 - Building an Effective Programme




34
Chapter 7 - Prevention of Metal Contamination




36
Chapter 8 - Selecting Control Points





40
Chapter 9 - Operating Sensitivity






42
Chapter 10 - Installation & Commissioning




46
Chapter 11 - Performance Validation / Auditing




48
Chapter 12 - Dealing With Suspect & Rejected Product



58
Chapter 13 - Data Analysis & Programme Improvement


60
Chapter 14 - Connectivity Solutions





62 2
The need for metal detection systems in the food and pharmaceutical industry is recognised by most manufacturers and
processors as an essential area for focus in any efficient quality regime. In an increasingly competitive market place,
driven by ever-changing customer needs, tightening of industry standards and the growth of regulatory and legislative
bodies, the importance of effective metal detection has been escalated in recent years.
However, merely installing metal detectors alone will not necessarily guarantee that a metal-free product is produced
unless the installations form part of an effective overall metal detection programme. This guide has been written to assist
manufacturers in the setting up of such a programme.
An effective metal detection programme can provide protection against product failure and recalls, help to maintain hard
fought supplier certification status and reduce overall operating costs. The programme can also support the ability to prove
that reasonable precautions and due diligence have been applied in the manufacturing process in the event of a legal claim
situation. The requirements for and the benefits of adopting a programme are summarised in the diagram below.
Introduction
I
n
t
r
oducti
on
External Inputs
Effective Metal Detection Programme
Metal Detection System Selection
1. Introduction to Metal Detection
2. Key Design Features
3. Factors Limiting Sensitivity
4. Systems Design & Applications
Building an Effective Programme
5. Reasons For a Metal Detection Programme
6. Building an Effective Programme
7. Prevention of Metal Contamination
8. Selecting Control Points
9. Operating Sensitivity
10. Installation & Commissioning
11. Performance Validation / Auditing
12. Dealing With Suspect & Rejected Product
13. Data Analysis & Programme Improvement
14. Connectivity Solutions
Customer / Industry Consortiums
Industry Standards
Regulatory Authorities
Retail Consortiums e.g. BRC, IFS
Retailer Codes
Brand Consumer Codes
International Standards e.g. ISO 22000
Industry Standards e.g. HACCP
SQF 1000 / 2000 Code
GMP
Food Safety Legislation
USDA
FDA
Certi cation Bodies
Producer, Retailer & Consumer Benefits
Reasonable
Precautions
Due
Diligence
Reduced
Failure Costs
Protection Against
Product Recall/Claims
Retailer
Con dence
Brand
Protection
Maintain
Certi cation Status
Maintain Approved
Supplier Status 3
This guide provides a definitive reference point for those involved in food safety, giving an insight into all aspects from
basic principles through to implementing a comprehensive metal detection programme.
Chapters 1 to 4 provide an overview of how metal detectors work, an explanation of important design features, an
insight into factors which potentially limit performance of the equipment and the integration of metal detectors with
effective rejection systems.
Chapters 5 to 14 go on to explain that simply installing a metal detection system alone is not enough. A comprehensive
metal detection programme is required and the key elements of such a programme are explained in detail.
Margin assists are used throughout the guide to draw attention to points of particular note. The symbols used and their
meanings are described below:
Symbol
Meaning
Warning - An operating practice that could result in the
incorrect operation or use of the metal detection system
Best Practice - An operating practice that can be consi-
dered best practice at time of publication
Record - Highlights pertinent records that should be gene-
rated and maintained in order to demonstrate the effective
operation of the metal detection programme 4
Chapter 1
Introduction to Metal Detection
1
:
I
n
t
r
od
ucti
on t
o
M
e
t
a
l De
t
e
cti
o
n
In order to make informed decisions about metal detection systems, it is important to gain
an understanding of the main system components and principles of operation. This chapter
aims to deliver a basic overview and develop an understanding which can be built upon
in subsequent chapters to gain a greater understanding of metal detection technology,
equipment capabilities and performance.
1.1 Sources of Metal Contamination
The sources of contamination are numerous and even
the most stringent controls cannot prevent the occasional
incident. Good working practices will minimise the
likelihood of metal particles entering the production flow
and correct equipment design and appropriate selection
will maximise the likelihood of reliably detecting and
rejecting any that do.
Contamination normally comes from one of four sources:
Raw Materials
Typical examples include metal tags and lead shot in
meat, wire in wheat, screen wire in powder material,
tractor parts in vegetables, hooks in fish, staples and
wire strapping from material containers.
Personal Effects
Buttons, pens, jewellery, coins, keys, hair clips,
thumb tacks, pins, paper clips, etc.
Maintenance
Screwdrivers and similar tools, swarf and welding
slag following repairs, copper wire off cuts following
electrical repairs, miscellaneous items resulting
from inefficient cleanup or carelessness and metal
shavings from pipe repair.
In-plant Processing
The danger of contamination exists every time the
product is handled or passes through a process.
Crushers, mixers, blenders, slicers and transport
systems all contribute. Examples include broken
screens, metal slivers from milling machines and
foil from reclaimed products.
Identifying the likely source of contamination is an
important stage in developing an overall metal detection
programme.
1.2 What is a Metal Detection System?
An industrial metal detection system is a sophisticated piece
of equipment used to detect and reject unwanted metal
contamination. When properly installed and operated, it
will help to reduce metal contamination and improve food
safety. A typical metal detection system consists of four
main parts as follows:
Detector Coil or Search "Head"
Most modern metal detectors fall into one of two main
categories. The first type utilises a "balanced coil" search
head. Detectors of this design are capable of detecting
all metal contaminant types including ferrous, non-
ferrous and stainless steels, in fresh and frozen products.
The products being inspected can be either unwrapped
or wrapped and can include those wrapped in metallised
films. The second detector type utilises permanent magnets
in a "Ferrous-in-Foil" search head. These search heads are
capable of detecting ferrous metals and magnetic stainless
steels only within fresh or frozen products which are packed
in an aluminium foil wrapping.
Whilst it is recognised that other technologies exist, this
guide concentrates mainly on the "balanced coil" detector
type and to a much lesser extent on the Ferrous-in-Foil
(FIF) technologies.
5
The search heads are manufactured in virtually any size to
suit the product being inspected. They may be rectangular
or round and may be mounted horizontally, vertically or on
an incline. Each has an opening through which product
passes. This is called the "aperture." When a piece of metal
contamination is detected by the detector search head, a