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Advice on the Location of the Metcorr


When selecting the location for the metal detection equipment, a number of

environmental factors should be considered and taken into account at the planning

stage including:当为金属检测设备选择安装位置时,应当考虑很多的环境因素和将来规划,包括:

Correct location that provides an optimum performance of Metcorr 117C and

minimizes disturbances of the operation like removing the tramp metal from the

process.正确的安装位置能保证Metcorr 117C最优的性能,同时最小化运行时的干扰,例如工艺中消除杂质金属。

Reliable operation of Metcorr 117C which could be effected by climatic

conditions, mechanical interferences from environmental metal constructions

and electrical interferences like systems which generate radiated noise fields to

air or conductive noise voltages to mains.   Metcorr 117C运行的可靠性受如下条件影响:气候条件,周围的金属结构的机械干扰,电气干扰。电气干扰如系统在空气中产生辐射噪声或在主电源中传导噪声电压。

The given safety distances are approximate values, which could be basis for designing the location of the Metcorr 117C in respect of noise sources. 给定的安全距离是一种个近似值,可根据该值和噪声源设计Metcorr 117C的安装位置。

The exact minimum distance depends on the strength and type of noise and the sensitivity of the Metcorr 117C. 准确的最小距离取决于噪声的强度和类型,以及Metcorr 117C的灵敏度。

Even if the Metcorr obviously operates normally with shorter distances to noise source, it is always recommended to have the safety distances if there is ample space in the installation site.即使Metcorr运行时有很明显的短距离噪声源,但是我们建议如果现场有足够的空间,最好要有安全距离。

 However, if the amount of space is restricted, it is practical to temporarily position the Metcorr to evaluate any problems likely to arise as a result of the environmental conditions.但是,如果空间受限,估计由于环境引起的任何问题情况来比较实际的确定Metcorr的位置。

Location in the Process工艺中的定位

If there is no other limitations, the placing of the metal detector in process should be

just before the object to be protected from tramp metals. 如果没有其他限制,在工艺中该金属检测器的定位应放在物料检测杂质金属之前。

It should also be considered the optimum function of the detector, which mainly determines the application of the external control outputs, and the needs for optional devices.还应考虑检测器的最优化功能,其主要决定外部控制输出应用和可选装置的需要。

The following factors should be considered prior to the installation:在安装前,必须考虑以下因素:

 Is it possible to restart the conveyor when loaded?在加载状态下是否可能重启传送带?

 Where is the most convenient location for the manual removal of the tramp


How often are harmful metal objects likely to appear on the belt?有害金属物质可能出现在传送带上的频率是多少?

Where would the operator responsible for tramp metal removal be located under

normal circumstances? 正常情况下,操作工应该在哪移走杂质金属?

 What are the implications of stopping the conveyor on the in-feeding and outfeeding sides?在加料和出料侧,哪些与停止传送带有关联?

If a magnetic separator is used and it is not operating on continuous duty, but is

switched on only when a metal object is approaching, a metal detector will be

required to initiate the switching sequence. The detector needs to be installed ahead

of the separator.如果使用电磁分离器,他不是持续运行的,而是只有当金属物体接近时启动。金属检测器用来初始化该开关顺序。检测器需要安装在分离器的前面。

For the detection and manual extraction of the non-magnetic metal, another detector

is required after the separator. 为了检测和手动去除非磁性金属,需要在分离器后面再装一个检测器。

In this case, if ore (or other conveyed material) is highly magnetic, it could be magnetized by the separator and acts like a permanent magnet, which has strong response on the Metcorr and causes false alarms from ore. 在这种情况下,如果矿石(或者其他传送物料)具有非常高的磁性,它们将会被分离器磁化成像一个永久磁铁,当他们通过Metccor时反应强烈从而出现矿石假报警。

Then there must be a demagnetizer between the separator and the Metcorr or it can limit the usable sensitivity setting.然后,必须在分离器和Metcorr之间安装一个去磁器或者也可限制可用的灵敏度设置。

Climatic Conditions 气候条件

If the installation site is wet or is subject to rain, water is dropping down or splashing for some reason over the Metcorr, the degree of protection of the coil and electronics should be considered. Consideration should be given in case of occasional sensitivity adjustments and servicing the system.如果安装现场潮湿或者遭受雨淋,由于某种原因,水会掉下或者溅到Metcorr上面,这时应该考虑线圈和电子元件的保护等级。也应考虑偶尔的灵明度调整和维修系统的情况。

High temperatures should be avoided by installing the electronics cabinet in as cool

a place as possible. The risk of component failure diminishes considerably with a

reduction in the operating temperature. It is beneficial to avoid direct sunshine on

the cabinet in a tropical climate. The coil system is also recommended to locate in a

shaded place to avoid extreme temperatures exceeding the specified temperature

range. 必须避免高温,将电子柜安装到尽可能阴凉的地方。部件失效危及大大减少工作温度的降低效果。在热带气候区域尽量避免阳光直射。同样建议将线圈系统安装到阴暗区域,避免其最高温度超过规定值。

Location of the Electronics Cabinet and the Coil Cables电子柜和线圈电缆的定位

Safety distances from interferences 远离干扰的安全距离

Electronics unit电子单元

 2 meters from the powerful operating electrical systems and their power cables

(systems like electric motors, transformers, relays and walkie-talkies)2米的远离强大的电力系统以及动力电缆(系统如电机,变压器,继电系统和无线对讲系统)

 5 meters from the electrical systems and their cables which could generate

stronger interference fields ( like transformer stations, control systems e.g. thyristors and contractors, magnetic separators and arc welders)5米远离电气系统和可产生强干扰区域的电缆(像变电站,控制系统如整流器,磁分离器和电弧焊机)

Use stable power line for mains supply使用稳定的电源线路提供主电源。

Coils cables线圈电缆

0.5 - 2meters depending on the interference source   0.5-2米,取决于干扰源

Protect against mechanical damage保护免受机械损伤。

Start-up and faultfinding are simplified if the coils and the electronics cabinet are

located close to each other.如果将线圈和电子柜安装在一起,可以是启动和故障查询简单化。

Standard coil cable length is 10 meters and the cable is a shielded type. Despite of

the shielding, the cable route should be as much as possible free from the electrical

interferences. Common cable trays should be avoided, if the other cables are suspected to radiate interferences, such as from high voltage power cables where

load is momentarily switched on and off. In those cases, it is better to run the cable

as far away from the cable trays as the installation place allows.

线圈的标准电缆为10米长的屏蔽电缆。不管屏蔽与否,线圈电缆线路应该尽可能不受电气干扰。必须避免安装到普通电缆桥架中, 如果其他电缆具有辐射干扰,如高压电缆的负载的瞬间开和关。在这些情况下,如果安装条件容许的话,最好将线圈电缆远离电缆桥架。

The distance to interference sources is recommended to be over 2 meters and the

minimum allowable value is about 0.5 meters.


The standard length of cable should be used, if possible, because the extra length is

increasing the risk for interferences. If the standard length is too short, the recommended maximum length is 30 meters.


The coil cable should be protected against the risk of mechanical damage caused e.g.

by falling stones, moving vehicles and working machines. Flexible cable armor is



For mechanical protection (also for electrical shielding) if metallic type is used then

make sure the armor is installed stable near the coil system to avoid false alarms.

If the swing-away type mounting system for upper coil element (e.g. optional coil

mounting set CMS) is used, the need for a free cable length for the swinging

movement should be considered. In those cases the upper coil cable should run over

the top across steel tube of the coil mounting system.


During the operation, there is no need to constantly monitor the cabinet, which can

be located remotely from the sight of the operator. After the initial start-up, the

cabinet door needs to be opened only in the following cases:


 to adjust sensitivity调整灵敏度

fault condition has developed 故障出现

timing of the optional ACU card is readjusted 重新调整可选ACU卡的时间

The installation site is not recommended to be close to the electrical interference

sources. In practice, the minimum allowable distance without problems depends on

the strength and type of interference, which could be difficult to estimate before

testing the operation. Distance 2 – 5 meters is recommended when selecting the

installation place for the electronics cabinet.


Electrical interference can also be in the form of line voltage “spikes”, varying

frequency or voltage level caused by on-off or varying inductive or heavy loads of

electrical equipment on the same power line as the Metcorr. When connecting the

mains a power line free of inductive loads is recommended.


Location of the Coil System in relation to the Mechanical Interferences


Once the location of the Metcorr in the process has been selected, the following

outlines in greater details the mechanical factors that influence and also limit the

siting of the coil assembly. These factors are:


too much static metal in immediate vicinity of the coil system过多静态金属在目前的线圈系统中。

structural vibration结构性振动

moving metals too close to the coil移动金属过于接近线圈

conveyor belt idlers too close to the coil传送带输送辊过于接近线圈

metal reinforced belt 金属高强度输送带

Effect of static metal静态金属的影响

W = width of the coil线圈宽度

W/2 safety distance to static metallic construction.到静态金属结构的安全距离

As the electronics is automatically compensated for the environment, the coils of the

Metcorr can be mounted on metallic conveyor structures. Any metal piece, which

does not move in relation to the coils, is regarded as static from the point of view of

the Metcorr.


Large amount of static metal in an immediate vicinity of the coil element can exceed

the compensating limit of the Metcorr electronics and disturb the operation or at

least it can prevent from installing the coil elements with minimum gap, which is

recommended in order to have a maximum coil sensitivity. The massive metal

constructions and the metallic (conductive) loops can both be harmful.


When designing the coil installation the minimum distances to some type of static

metal constructions should be considered. The safety distances may be used as a

basis for installation.


Avoid installing the lower coil over a crossbar, as such a massive metal bar may

distort the magnetic field. The space below the coil up to the distance of W/2 should

be clear from metallic structural elements, other than the brackets, by which the

lower coil unit is fixed to the frame. Within this distance there should not be any

electrical loops, which could be formed by coil elements mounting structures.


Effects of structural vibration结构振动的影响

L = length of the coil线圈的长度

 Firm coil elements installation 坚固的线圈基础安装

L/2 the safety area from coil with electrically stable joints in conveyor construction 传送带上电气固定连接点到线圈的安全距离

L/2 safety distance from coil with only static metallic constructions.


If the coils or frame assembly of the conveyor vibrate continuously, spurious detections may occur. The decisive factor under vibrating conditions is, whether one

or both of the coils move in respect to each other, or to any part of the metallic

structure. If the coils have been well fixed to a vibrating metal frame, the coils do

not experience the vibration as a change in the electromagnetic environment. Thus

the vibration of the structure does not cause false detections. There is, however, still

the possibility that another nearby metal construction vibrates independently from

the frame structure and may thus cause disturbance.


The extent of vibration, which the detection system tolerates in the presence of metal

without spurious detections, depends on the frequency and amplitude of movement

relative to metal and also on the mass of metal.


Because of this, a non-metallic support structure is not stable. For example, impregnated timber or fiberglass-reinforced plastic is recommended. Small metallic

items, like screws, bolts and brackets may be used without harm. In spite of the

material of the upper coil support, the construction must be firm.


When the coils have been installed on the conveyor frame with the optional Coil

Mounting Set as shown in Figure 1, the structural vibration seldom creates



If metal objects (e.g. the conveyor structure) in the vicinity of coils have been bolted

together and it forms conductive loops, a disturbance may arise as a result of

vibration. The eddy currents created by the detecting system in the metal structure

do not normally cause a disturbance, if they are stable. However, if the electrical

contact of a bolted joint varies under vibration, to an extent where disruption can

occur in the eddy current flow, a spurious detection can occur. Eddy currents are

included in a zone, which extends over a distance that is equal to half of the length

of the coil (or L/2), in any direction from the coil. The distance can even be longer in

the case when electrical loop is not closed inside L/2.


A fully welded support structure in the vicinity of the coil assembly is less prone to

the vibration-related disturbance described above. On an existing conveyor

assembly, bolted joints can be welded, if they are found to be a cause of false



In practice, many metal objects such like metallic wall elements and roof sheeting or

air ducts, may be positioned within the distance of L/2 from the coil. If these metal

objects move or vibrate in relation to the coils, they may cause interference.


Effects of moving metals 移动金属的影响

The safety distances to coil: 到线圈的安全距离

1.5 x L metal-clad door金属包门

4 x L crusher破碎机

4 x L vibrating screen振筛机

7 x L loader, dozer装载机,推土机

The most sensitive area of the coil assembly is situated within the aperture between

the coils. The magnetic field, which is generated by Metcorr for scanning the

aperture, also extends externally over the outer surfaces of the coils.


This field weakens rapidly with increasing distance from the coils. This means that Metcorr can detect also moving metals outside the coil system with sensitivity which is depending on the distance between moving metal and coil, the mass of metal, the

amplitude and the frequency of movement. Large metal objects that move in the

exterior range of the field may cause spurious detections. To avoid false alarms, the

Metcorr should be located away from heavy mobile machinery of any kind.


Effects of idlers  输送辊的影响

Electrically stable joints with roller shaft mountings.滚动轴部件的电气固定连接点

2.5 x W - the distance between rollers where coil locates inside.线圈定位在其内的两辊的输送距离-2。5倍宽。

-the distance from flexible mounted rollers.活动支架辊的距离

If interferences use special constructions 使用特殊结构的干扰

Roller shafts 辊轮轴

If the shafts of the rollers are fixed without bolts to the idler frame and are held in

place by gravity in fork-like brackets, the joint of the shaft is electrically unstable,

especially when subjected to shocks and vibration. This may cause spurious

detections. Welded or tightly bolted joints are thus preferred on the neighboring



Distance of idlers 输送辊距离

Reducing the distance between the idlers may result in increased interference,

although the resultant reduction in belt sag is beneficial from the standpoint of:


minimal flapping and minimal disturbance from steel cords钢绳的最小振动和扰动

minimal separation of coil units and thus optimum sensitivity 最小的线圈的分离和最优的灵敏度

In case of metal-free belt and light load, the optimum distance may compare

favorably with standard design procedures.如果是轻载的非金属传送带,其最优距离可能比得上标准设计值。

With heavily loaded and steel-reinforced belts carrying coarse material, the optimum

distance of the rollers is around 2.5 x W (centerline to centerline). If a shorter

distance is required by the manufacturer of the conveyor, the clearance between the

edge of the coil and the surface of the roller may be reduced to a few centimeters (or

two inches), but in such a case it is quite likely that a non-standard roller construction shall be used.


Flexible mounted rollers 活动辊

Only fixed-mounted troughing sets and rollers may be used within the distance L

from the coils. Therefore, training troughing sets and flat belt trainers shall not be

mounted on troughing sets, which allow some, albeit limited, movement of rolls,

may not be used on this range.


The following special constructions can be used to circumvent interference from


Construction结构                                 Efficiency效率

Roller sleeves of low conducting and                Fair

non-magnetic metal (e.g. NiCr-steel),

shaft rotating                                       良好



As above, but shaft non-rotating                    Good

如上,但轴不旋转                               好

Rollers of non-metallic material,                   Good

shaft rotating ( e.g. rubber-disk rollers)

非金属材料辊轮,轴旋转(例如盘式橡胶辊轮)         好

Rollers of non-metallic material,                   Very good

except for flanges and bearing houses,                     好

which are of non-magnetic metal, shaft




Effects of metal reinforced conveyor belts 加强金属传送带的影响

Steel reinforced belts, depending on the material, may limit the sensitivity.根据材料,钢芯传送带可能限制灵敏度

Minimize vertical and horizontal flapping of the belt.最小化横纵向的传送带的扰动

Use Splice Detector for interferences from splicing and repairing the belt.使用连接检测器检测连接部分的干扰以及修复传送带

If a conveyor belt contains discrete steel reinforcements the Metcorr can be used

under most circumstances, however, it is unlikely that the full sensitivity of Metcorr

could be achieved. In practice, the lower detection limit of the unit is impaired, as

very small objects can no longer be detected with ease. The sensitivity setting of the

instrument would be reduced to a point where all spurious detections resulting from

the reinforcing wires disappear. Where very small metal pieces are to be detected

and no compromise is possible, the belt should not contain metal in any form. Belts

reinforced by synthetic fibers, such as polyamide are suitable for applications where

high strength and absence of metal are simultaneously required.


Longitudinal steel cords纵向钢筋

If the belt has steel cords, spurious detections may occur. Thus, the full sensitivity of

the detector cannot be achieved, as the adjustment is dictated by the necessity to

avoid spurious detections.


The Metcorr does not experience any change in the environment, as long as the belt

containing the longitudinal steel cords moves smoothly, as the cords can be regarded

as static metal in the same way as the frame. Disturbing spurious detections are

generated only by vertical or horizontal movement of the belt. Untroughed belts are

especially prone to flapping when running empty, or being started.


The following factors affect the tendency for flapping:


distance of idlers   辊距

evenness of material feed 进料的均匀性

lump size 料的大小

angle of troughing 凹槽的角度

tension variation at the start 启动时张力的变化

The movement can be reduced through modification of above-mentioned factors.


Steel-cord weft 钢束织物

Steel cords in a transverse direction to the belt produce a different electrical

interference from those of longitudinal cords. If the pitch of cords and the speed of

the belt are known, it is possible to calculate the frequency of weft cords passing

through the coils. If this frequency is 25/second or more, the risk of interference is

very low. On the other hand, if the frequency is less than 10/second, it may be

necessary to reduce the sensitivity adjustment to a level that avoids spurious

detections, even though the vertical flapping of the belt has been minimized.


Woven metal fabric 金属编织结构

If the belt is reinforced by metallic woven fabric, in which the warp and the weft are

in electrically conducting contact with each other, the detection will be severely

impaired or may prove impossible. Modifications to minimize flapping do not

remedy the problem, because the metallic net very badly distorts the magnetic field

in the aperture of the coils.


If the warp and weft are eclectically isolated from each other, performance is

comparable to that obtainable with longitudinal steel cords.


Splicing the belt 传送带的连接

Splicing of steel-corded belt with vulcanized joint breaks the electromagnetic

properties of the belt, as the cords are cut. This causes trouble mainly when there is a

need to detect small metal objects. If the splicing is made with additional cords for

additional strength, this break may be larger. If it is found, that the splice causes

false detections and a lower sensitivity is required, the optional belt fastener detector

may be used. This device deactivates Metcorr each time the fasteners pass through

the coil.


Belt fasteners 传送带紧固件

Metallic belt fasteners used for splicing and repair create a strong response in

Metcorr, when they pass through the coil system. It is therefore necessary to have

the optional belt fastener detector in such applications. If this - however infrequent -

failure to detect metal is unacceptable, it is better to limit the use of belt fasteners to

emergency repairs only (e.g. when the belt shall be replaced but there is no new belt

on hand and the process cannot be stopped).


The nuisance signal from the belt fasteners can be somewhat minimized by the use

of non-magnetic types (e.g. made of stainless, Monel, Everdur) and by using singleplate or separated fasteners. If the strip type is used, it should be of separable design and the fasteners should be separated if there is need to keep the spurious signal to the minimum. The belt fastener detector is available as an accessory and optional extra to Metcorr.


Location of the Coil System in relation to Electrical Interferences


The safety distances from the coil:


 2 x L with operating electrical devices and their power cables (systems like electric motors, transformers, walkie-talkies, relays, and switches).


7 x L with electrical devices which could generate strong interference fields

(systems like transformer stations, high power control systems e.g.

thyristors and contactors, magnetic separators, arc welders and high power

electric motors).


 5 x L between coils in non synchronized Metcorr systems.

5倍L, 远离在无同步线圈的Metcorr系统

L between coils in synchronized Metcorr systems.

L, 远离同步线圈的Metcorr系统

Electrical interferences are the factors that influence and can limit the location of the

coil system. Any kind of device which generates varying magnetic fields to the

active area of coil system may cause interference despite of the internal filtering,

because Metcorr is sensing magnetic fields during normal operation. Reaction of

Metcorr to noise source is dependent on the field strength, frequency and direction,

distance between coil system and noise source and sensitivity setting of Metcorr.


Synchronization, see section Connection Instructions.


In practice the noise problems can be avoided or at least minimized with having

enough space from the coil system to the possible interference source.