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MRL-News – 33/11/11 1
Dear -customer,Dear -customer,
In addition to our invitation to leaf through this new issue of MRL News which covers a number of interesting topics, we would like to invite you to visit us in Nurem-berg at the SPS/IPC/DRIVES 2011 from 22.11.2011 to 24.11.2011. This will give you the opportunity to discuss specific new products, the current product range and interesting applications personally with our staff, and also to see them for yourself. We look forward to your visit. You can find us in Hall 9, Stand No. 460.
With respect to the content of this MRL News, our first item today concerns the impor-tant subject of “nip points – danger zones!” (an article by Dr. Alfred Neudörfer, retired Academic Director at the Technical University of Darmstadt).
In addition we provide information on the following:
• the new Product Safety Act (ProdSG); and• new requirements relating to machinery safety in Brazil.
We also report on
• new possibilities for securing guards.
(PTO)
EC MACHINERY DIRECTIVE
New information on the subject of:
“Safety of Machinery and Machine Control Systems”
– Issue 33/11/11 –
2 MRL-News – 33/11/11 MRL-News – 33/11/11 3
We also tell you about an employers’ liability insurance association project concerning tolerable collision forces be-tween man and machine in certain cases.
Please see the table of contents to see where these and other topics can be found!
We hope you find this interesting reading.
With kind regards
Friedrich AdamsK.A. SCHMERSAL Holding GmbH & Co. KG, WuppertalHead of Schmersal tec.nicum
Wettenberg/Wuppertal, 2. November 2011
Table of Contents
Nip points – danger zones! ............................................................................................ 4
New Product Safety Act as successor to the GPSG .................................................... 12
Safety of machinery in Brazil ..................................................................................... 16
A matter that concerns us: don’t go down the slippery slope! ..................................... 17
A contribution to safe cooperation between man and machine .................................. 19
Risk of collision between man and machine ............................................................... 24
QM system and MD 2006/42/EC ................................................................................ 27
Schmersal news ........................................................................................................... 29
Schmersal expert forum ................................................................................................30
New product from the Schmersal Group .....................................................................32
Published by:
Elan Schaltelemente GmbH & Co. KGIm Ostpark 2 35435 Wettenberg
Telephone: +49 (0)641 9848-0 Fax: +49 (0)641 9848-420
Email: [email protected] Internet: www.elan.de · www.schmersal.com
Editor responsible:Friedrich Adams, c/o K.A. SCHMERSAL Holding GmbH & Co. KG,Möddinghofe 30, 42279 Wuppertal; E-Mail: [email protected]
Production: flick-werk – Werbe-Grafik Heinz Flick, 35075 Gladenbach
Liability
The information and recommendations in “MRL News” are provided to the best of our knowledge and in good faith. However they do not absolve you from your responsibility to check and weigh up the various aspects. With the exception of mandatory statutory provisions to the contrary, we assume no liability for any errors and misunderstandings in the presentation.
4 MRL-News – 33/11/11 MRL-News – 33/11/11 5
We have asked our author Dr. Alfred Neudörfer, former Academic Director at the Technical University of Darmstadt, with his many years of experience in the subject, to look into the subject of nip points, not least because it is our impression that nip points on in-running rollers are not only one of the most frequently encountered danger zones on machinery but also one of the most underestimated. In doing so we wish to make a contribution to improving under-standing of this problem, and hope you will find the article interesting.
Dr.-Ing. Alfred Neudörfer, Bensheim
Nip points – danger zones!
Typical nip points occur in the gap between two rollers moving in opposite directions. The physical impact of this is principally used in continuously operating machinery in stretching, rolling, profiling, printing, homogenising technical procedures etc., because the feed movement for the material runs synchronously with the deformation movement. Converging rollers therefore represent one of the most frequently occurring hazard zones on machinery that processes material that is of a wiry, arched, plate or continuous sheet nature. Every roller nip constitutes a significant potential hazard whose effect is incor-rectly estimated by many people during risk assessments. Whilst the physical effects that are exploited in technical processes are primarily designed to impact on the material, they have the same effect on a person with devastating consequences as soon as he or she gets caught in the nip point.
Physical effects at nip points
A wedge action develops in the in-running nip between two rotating rollers due to the cylindrical lateral surfaces: as soon as a part of the body - usually a finger - gets caught, frictional forces develop between each roller surface and the finger. These draw the fin-ger further into the in-running nip. Frictional forces are directly proportional to normal forces (FR = μ.FN), which increasingly crush the finger and cause elastic, followed by plastic, deformation. In the process both the normal forces and the frictional forces nec-essarily expand – a typical self-reinforcing effect.
But on top of this, a second self-reinforcing effect is established at the same time: the tangential frictional forces that occur on both rollers are added as vectors to produce a force parallelogram to the resultant insertion force. The further the finger is drawn in, the sharper the corner angle of the parallelogram, the longer the diagonals of the
Fig. 1: Mechanical effects in nip points
rFR11 FN1
rFR12
μ2
μ1
FN1
v = r.ω
v = r.ω
FEinzug1
FN2
FN2
ω
2
2
21
1
ω
vector addition of the ever increasing frictional forces (see above) and thus the final insertion force. The further the hand is drawn in, the greater the insertion force! It is no longer possible for the person to remove his hand by himself (see Figure 1).
The hazard potential presented by nip points not only arises from the increas-ingly narrow nip, but is also derived from the deformation energy acting in the in-running nip which is directly linked to the drive energy and to the kinetic energy stored in moving mass-es, which in turn is linked to the rotary frequency and the moment of inertia of the rotating rollers or cylinders.
Due to their inertia and the braking time of the drive train, even at low rotary speeds it is never possible to stop cylinders and rollers immediately without overrun. Sometimes this is compounded by spontaneous reactions by the people at risk. For example loosely folded cleaning cloths which get caught in the nip point by their corners can pull fingers into the narrow part of the trailing nip point because operators instinctively hold onto the cloths.
Slow-running pairs of rollers draw objects in just as forcefully as fast-running ones. The lower circumferential speed of the roller (v = r.ω) at which limbs are no longer drawn in is not known: extremely serious hand injuries have been documented at a circumferential speed of 1.8 m/min!
Morphology of nip points
In addition to the classic in-running nip point where two rollers are moving in opposite directions, other configurations of machinery elements are found in technical solutions which likewise have the effect of pulling in objects, and these are frequently overlooked. The significant variables when it comes to objects getting drawn in at nip points are the curvature radii, the direction and level of movement, the surface structure of the areas of operation as well as the friction conditions that occur between moving machine parts and vulnerable limbs (Figure 2).
6 MRL-News – 33/11/11 MRL-News – 33/11/11 7
Nip point
Combined with Examples
Gear drive
Worm drive
Rollers with
cross-slots
Crushing andconveyor screws
Circular knife
Tube cutters
Cut-off saws
Perforating rollers
Surface grinding machinesInternal and externalcylindrical grind mach.Centerless grindingmachines
Paper and goodstake-ups
Press belts
Nr. 2 31
1
2
3
4
5
6
7
Pinching points
Shear points
Cutting points
Piercing points
Friction points
Traps
Pull-in points
1
2
21
2
1
2
2
1
1
2
1
Fig. 4: Combinations with other danger zones
tips and fingernails rub differently against the same surface. Therefore the possibility of them getting drawn in should never be completely ruled out (Figure 3).
In everyday technical situations nip points occur in combination with other hazards (Figure 4), usually in-creasing the original risk potential of the “simple” nip point.
r1 = r2
1 2 Nr. 4 5 6
1
2
3
4
5
3
Curvature radius
Rot
ary
mov
emen
t
r1 = r2 r1 =
v1 = v2
v1 = v2
r 2
v2
21
r 1
v1
v1 = v2v1 = v2
v2 = 01
2
8
2
1
1
2
2
1
1 2
1
2
1
2
1
2
21
2
1
1
2
2
1
1
2
Fig. 2: Typical nip points
µ1
µ2
µ1 < µ2
Finger-nail
Finger-tip
Fig. 3: Friction conditions in the nip point
The angle of rotation plays a key role in the configuration of rollers which create a nip point. What at first glance appears to be a harmless outlet suddenly becomes a dangerous nip point if, for operational reasons, it becomes necessary to reverse in jog mode.
Rollers rotating in the same direction are often viewed to be safe. However caution is required here too: the only time that objects are not drawn in here is where the sum of the tangential forces is zero, i.e. where both rollers have the same circum-ferential speed and the same curvature ra-dius and establish the same friction con-ditions on points of con-tact. Nevertheless there is always some residual risk: finger-
8 MRL-News – 33/11/11 MRL-News – 33/11/11 9
Fig. 5: Design examples to prevent nip points
Direct safety-related methods
Design examplesunfavourable favourable
Explanations
Ener
getic
Elasticdeformation
Injuries are not to beexpected if at least one of therollers yields as a result of theinsertion forces and its moreeasily deformed than thevulnerable body part.
1 2 No. 3 4 5
1
2
3
4
Minimumgaps
Air pres-sure
Rubbersleeve
120
120< 6
No nip point for fingers andhands is created with gaps> 120 mm between rollersor parts. There is also nonip point if fixed parts standno more than 6 mm verticalto the roller.
Caution: a clear gap < 6 mmbetween moving rollers doesnot prevent the nip pointeffect.
Geo
met
ric
120
60°Interruptionof the power
flow
The inserted hand presses thefirst loosely resting roller out toproduce an adequate safetydistance.
< 6
have absolute priority over measures aimed at the safe conduct of those at risk (signs) – limbs will be drawn in with or without warning signs!
The basis for all safety-related measures must be the result of the risk assessment for the essential activities at or in the nip points. With respect to the “severity of the injury” risk factor, experience shows that in most cases it is appropriate to assume serious, irreversible injuries.
Avoiding nip points. As a matter of principle nip points that do not execute any techni-cal function can be avoided. Energy-related or geometric measures can be implemented depending on the situation (Figure 5). The main advantage of these direct (inherent) safety methods is that the nip points have ceased to exist. When assessing the residual risk remaining at the end of the design process, the direct safety-related measures imple-mented have the crucial advantage that they substantially reduce or completely eliminate
Injuries and their severity
The energy density in the in-running nip of most machinery exceeds all tolerable defor-mation thresholds in and on parts of the body as a result of the drive power alone, caus-ing serious injuries. In such injuries pressure, tensile and frictional forces act on the up-per extremity at the same time. The extent of damage primarily depends on the amount of pressure that builds up in viscoelastic tissue and on the geometry of the pair of rollers (curvature radii, nip width), the type of bearing (rigid, pliable), the surface properties of the rollers and the thickness of the hand that has been drawn in. The cross-section of this hand will vary according to the penetration depth, and the pressure exerted on the hand tissue will vary accordingly.
Emergency surgery [1] is divided into three principal types of injury depending on the occurrence of the most important factors causing damage (tensile, pressure and frictional forces):
1. Extensive tissue damage in the deeper structures of the hand where there has been predominantly pressure impact.
2. Extensive surface injuries (cracks in the skin, avulsion and tearing of the subcutane-ous tissue below) in the case of nip points with low pressure impact but rough roller surfaces.
3. Burns due to frictional heat in the case of relative movements between hand surface and the surface of rotating rollers (slipping) or caused by hot roller surfaces.
The combination of these influencing factors and their chronological impact produces different injuries. The transitions between them are fluid: for example tensile forces oc-cur if the static friction between the skin and roller surface is not surmounted when the hand is drawn in, which leads to tissue being stretched and to torn tissue and avulsion if limits of tissue strength are exceeded. Whilst tensile forces decrease as soon as there is sliding friction between the hand and the roller, frictional heat which causes burns is generated by relative movements.
Design measures
It is plain that machinery manufacturers must do everything in their power to prevent people getting injured at nip points. Technical measures (preventing or safeguarding)
[1] Boehnke, J.: Behandlung und Behandlungsergebnisse der Walzenquetschverletzungen an den oberen Extremitäten, Dissertation Universität Gießen, 1995 (Treatment and results of treating crush injuries to upper extremities caused by rollers; University of Gießen dissertation)
10 MRL-News – 33/11/11 MRL-News – 33/11/11 11
Releasing the trapped person. Where residual risks exist, designers must expect these to materialise. However they can influence the consequences for the injured persons. Af-ter an accident at a nip point, helpers attempt to free the trapped person quickly, thereby frequently impulsively pressing the control device to reverse the roller movement. This reversal leads to considerable worsening of the injuries for the person concerned, how-ever, because the part of the body must pass through the narrow space in the nip point for a second time, this time in the reverse direction. It is easier to free the person when design measures have been provided to widen the in-running nip space (be this by just a few millimetres). Releasing the bearing widens the space between the rollers, the wedge effect in the constriction collapses, and the compressive stress on the hand declines. As a result the normal and frictional forces cease to have an effect. It is much easier to free the injured person from the nip point.
Conclusion
Nip points have remarkable hazard potential, and can almost always lead to serious inju-ries. All nip points must be determined during the hazard or risk analysis, where possible during the draft phase (CAD animation) but at the latest on the finished machine. Tak-ing operating conditions into consideration, technical safety measures must effectively reduce the damaging impact of nip points to an acceptable residual risk as part of a decisive and accepted safety and operating concept.
Fig. 6: Design examples to safeguard nip points
Design aspects Design examplesunfavourable favourable
Explanations
Safe
ty-r
elat
ed a
spec
ts
Protec-tive
device
Enclo-sure(rail)
Protective devices must function reliablythroughout the entire service life of themachine, and must not cause any newhazards. Round profiles (so-called safetyspindles) in front of rollers merely doublethe number of nip points!
Profiles whose edges are vertical to therotating surfaces only protect in the case ofsmoothly rotating rollers or cylinders.Surfaces with longitudinal slots which arenot deeper than 4 mm and are not widerthan 8 mm also count as smoothly rotating.Raised areas may not be higher than 4 mm.
Safety edges in front of nip points must notform any new nip points (angle or surfacetangent alpha < 90°) or cutting points(alpha > 90°).Limbs are safely kept away if the flank of theangle section is vertical to the surface.
The gap between edge and roller surfacemust not get narrower during the switchingmovement as this will crush fingers. Thefulcrum of the switching movement mustbe on or outside the Thales’ circle put downby the centre of the roller.
6
6
8
4
6
6
Safetyedge
1 2 3 No. 4 5 6
1
2
3
4Thales circle
the “severity of the injury” risk parameter, something that is not only important but is also at the top of the list in most risk assessment procedures.
Safeguarding nip points. Nip points which are essential from a technical and func-tional point of view cannot be prevented. Without them the machine would not work. Because of their great potential to cause injury these must be safeguarded using indirect safety-related measures, i.e. using guards. Nip points can basically be safeguarded using guards or fixed safety devices or safety devices with presence sensing (acting with or without contact) [1]. Guards are dominant in practice, however. Care must be taken when designing them that they do not create any new danger zones (Figure 6).
In terms of the residual risk assessment, the indirect safety measures implemented do not reduce the “severity of the (potential) injury” but only the “frequency or probability of encountering the hazard” parameter. This is because in the event of the safety device being ineffective, which is something that can never be excluded e.g. as a result of ma-nipulation or bridging in special operating modes, the hazard potential of the nip point is completely effective.
[1] Neudörfer, A.: Konstruieren sicherheitsgerechter Produkte (Designing safe products), Heidelberg, Berlin: Springer, 2011
Erratum human est!
In our MRL-News 32/06/11 we reported that the new standard EN ISO 13 855:2010-1 (Arrangement of protective devices with respect to the approach speeds of parts of the human body = amendment of EN 999:1998 + A1.2008) now also incorporates guards in order to decide whether an interlock with or without latching is required to safeguard them (= CORRECT!). It is to be assumed here that the approach of persons should be calculated at a walking speed of 1.6 m/s and an approach speed for upper arms of 2.0 m/s (= FALSE!) 1.6 m/s applies as a general rule (unlike the calculation of safety distances in optoelectronic protective devices, for example).
12 MRL-News – 33/11/11 MRL-News – 33/11/11 13
ing 768/2008/EC will be transposed (with the con-comitant necessary lan-guage and legal system-related revisions). It con-tains common principles and standard clauses for application in all secto-ral acts (e.g. the Machin-ery Directive, Medicinal Products Directive etc.). In future, depending on the product, the legisla-tor can select the neces-sary procedures from the various conformity assessment modules, and these should then be adopted with as little alteration as possible. This ruling forms an overarching framework for legal provisions on the harmonisation of the internal market and moreover contains clear definitions on specific fundamental terms. Until now a wide range of terms has been used in legal pro-visions covering the free movement of goods which were sometimes not defined or were differently defined, so that they did not contribute to legal certainty.
GS mark
It may be important to some readers that there will continue to be a GS mark and that the prerequisites for its granting and for checking its authorised use will in future be formulated more strictly and will be supple-mented. This is in-tended to strengthen the GS mark sustainably and also overcome misuse. For example the committee for product safety is to determine spec-ifications that must be taken into consideration during the inspection. What is more, in future all GS areas must publish information on mark misuse (keyword: blacklist).
The changes will take some getting use to
The new terminology “available on the market” and “making available on the market” which supersede the previous terminology of placing on the market (or putting into op-
Nobody will surely be angry and disappointed about the fact that there will not be any important changes in the new ProdSG for the design and operation of machinery!
ALT NEUThe following information refers to German law and interpretations as represented in Germany only.
New Product Safety Act as successor to the GPSG
The superseding of the former German Equipment and Product Safety Act (GPSG) by the new act on the provision of products on the market (Product Safety Act or ProdSG) would appear to be going smoothly. As with the GPSG, the purpose of the ProdSG is likewise to transpose the EC Machinery Directive MD 2006/42/EC into national law (along with the majority of the remaining internal market directives such as the Low Volt-age Directive, Pressure Equipment Directive etc.). The German Bundestag and Bun-desrat approved it in September 2011 and October 2011 so that the new Act will probably come into force on 1 December 2011 (1st day of the month after its publication in the Federal Law Gazette). The practical transposition of EC internal market directives using regulatory measures remains, and therefore applies to the Machine Ordinance which is now called “9th ProdSV”.
The impetus for the new Act was to transpose the European New Legislative Frame-work (NLF), whereby substantial changes are chiefly confined to areas other than safe design (MD 2006/42/EC) and the operation of machinery (BetrSichV). However the supplementary Directive 2009/127/EC (machinery for the application of pesticides) was in-serted. This means that with respect to the area we are interested in there are basically no changes, or at least no substantial changes, when it comes to content. According to what we have read and heard, the only change is that products that are not ready to use (which includes used products) are now also covered by the ProdSG (this should not be confused with partly completed machinery which already falls under the MD/42/EC).
Transposing the NLF (New Legislative Framework)
The focus here is on adapting competing regulations in the GPSG resulting from EC Regulation 765/2008 and which principally concern the so-called notified bodies and market surveillance. Among other things the ProdSG plans new and improved provi-sions in the area of market surveillance. For example the cooperation between market surveillance (which Federal States are responsible for) and customs is to be intensified so that dangerous products can be tracked down as quickly as possible. In addition the rul-
14 MRL-News – 33/11/11 MRL-News – 33/11/11 15
With this interpretation paper (which ought to be revised) and with the help of further employ-ers’ liability insurance association checklists, the result arrived at in future will frequently (usually?) be that there has been no substantial change.
This means that it continues to be the intention to generally not get to the point in the process where “Substantial alteration: yes!” is reached. This takes into account the notion that not all current MD requirements relating to the chang-es to machinery can be satisfied, in part for objective reasons and in part from the point of view of eco-nomic viability. However this does not mean that a disproportionate degree of reduced machinery safety is tolerated. Rather the Ordinance on Industrial Health and Safety (BetrSichV), which is the national implementation of the Use of Work Equipment Directive 2009/42/EC, must then be applied in Germany. Consequently actual changes must be implemented according to the state of the art unless, in exceptional cases, this is con-siderably technically or economically unreason-able. Only the parts of the machinery that are unaffected by alterations may be left out of considerations (as long as these at least comply with the national transposition of the Use of Work Equipment Directive 2009/42/EC, in other words with the BetrSichV in Germany, which apply under all circumstances).
So …
there is our summary which focuses on the subject of “machinery”. If we have over-looked any important elements we will include information on these at a later date in another edition of the MRL News.
eration) [1] will take some getting used to (1). According to the comment [2], this is not associated with any amendment to the area of application, however. It merely concerns adaptation to NLF terminology. The second aspect that will take time get-ting used to (2) could be the term “economic operators” as an umbrella term for a manufacturer, authorised representative, importer or dealer; there may also be other new terminology and/or other requirements, but there are no major changes re-lated to our subject (see above).
Used products
According to the comment there ought not to be any need to discuss used machinery. The wording on this now goes as follows: “The possibility of achieving a higher safety level or the availability of other products that present less risk is no sufficient reason to view a product as dangerous.” The comment on this is as follows: “The new, much more understandable Sentence 3 achieves the same objective (as in the former GPSG), namely to facilitate the placing on the market of used technical work equipment which does not correspond to the most recent state of the art but which should nevertheless be viewed as safe.”
Substantial modifications to products
Furthermore this does not affect the area of the substantial modification of machinery, even if this formulation no longer exists in this way in legislative texts. The wording here is as follows: “With the adaptation of the term placing on the market to (EC) Regula-tion No. 75/2008, the term of “substantially altered product” also no longer applies. No change to the facts and circumstances is associated with this. A used product that has been substantially altered compared to its original state will still be regarded as a new product in future. In connection with this, refer in particular to European interpre-tation No. 2.1 of the implementation guidelines of the principles drawn up according to the new concept and the overall concept: “A product which has been significantly altered since it was put into operation with the aim of modifying its original power, use or design, can be viewed as a new product” and also the national interpretation in the Bund-Länder-Papier “Wesentliche Veränderung von Maschinen” dated 7 September 2000 – Bundesarbeitsblatt 11/2000 P. 35.“
[1] Available on the market is every release of a product against payment or free of charge for distribution, consumption or use on the market of the European Union as part of business.
[2] Comment on the bill before the German Bundestag (similarly quote et seq.)
NLF objective (among others): improved CE mark integrity
Machineis safe
Injury(damage toproperty)?
Irreversible(high)
MD 2006/42/EG
Unsafe?
Yes
Probability?
High
Substantial alteration?
Substantialalteration
New hazard/increased risk?
No substantialalteration
Restoresafety
No substantialalteration
Yes
Simple guardpossible?
No
Reversible(low)
Low
No
Yes
MD 2009/104/EG(BetrSichV)
No
Other protective devices are also possible (an interpretation that is shared by the employers’ liability insurance associa-tions) if they are professionally and cor-rectly installed and there is no, or only superficial, intervention in the existing control device.
16 MRL-News – 33/11/11 MRL-News – 33/11/11 17
Safety of machinery in Brazil
The German Engineering Federation (VDMA) advises of a reform to the Brazilian Ma-chinery Safety Directive No. 12 which we cite as follows:
Features and impact of the revised version
The new version promulgated in December 2010 is designed to revolutionise the safe-ty of machinery workers according to the Brazilian press. The 80-page document is based on initiatives by President Dilma Rousseff who assumed office in 2010. As yet the VDMA does not have any assessments of this Directive, very probably because the transition periods range between 12 months and several years.
An initial perusal suggests the interventions could be considerable; in some areas there is talk of shutting down or banning machinery designs. Brazilian lawyers have been heard saying that the text concerns a ruling from the Ministry of Labour and Employ-ment, but that its consequences are so serious that they can actually only be regulated by law, which is why constitutional challenges are conceivable. Currently it is only pos-sible to speculate on the impact on German mechanical engineers.
Further information for VDMA members
An English version of the new Brazilian Machinery Directive No. 12 can be re-quested from ([email protected]).
We will also keep you informed as soon as we know more!
A matter that concerns us: Don’t go down the slippery slope!
We want to remind people of this piece of advice, not only against the background of the cold season that awaits us but also in case you are contemplating an interlock for a guard with electromagnetic latching. This new technology, which will have normative “blessing” conferred on it in the course of the amendment to EN 1088:1996 (in future EN ISO 14 119), demonstrates a number of functional and safety benefits because the electro-magnet – the latching element in traditional devices – is replaced by the electromagnetic force. The Schmersal range has a device for this in Model MZM 100 (see figure).
There are no longer any protruding parts on devices of this kind, for example. What is more they are easy to clean and have no insertion openings for actuators where dirt can collect (keywords: hygiene and availabil-ity); in addition they have high resistance to dust and liquids and have no moving parts. However it is important always to consider and to weigh up as part of a risk assessment the fact that this concerns a device based on working current, so that unless a UPS is available, the latching function is no longer present if there is a power interruption.
One can come unstuck if the advertised presentation of the manufacturer fails to correctly distinguish between inter-lock-ing devices with electromagnetic latch-ing and interlocking devices with safe electromagnetic latching. Only the latter – which we can also refer to as safety electromagnetic interlocks – are suitable for human protection functions (typi-cally for hazardous overrun movements). The new standard makes a conscious and explicit distinction here between personal protection and process or ma-chine protection.
Interlocking device with electromagnetic interlock – safety-related classification: PL “e”, CC 4 or SIL 3
18 MRL-News – 33/11/11 MRL-News – 33/11/11 19
But what makes an interlocking device with electromagnetic latching into an interlock-ing device with safe latching, in other words a “solenoid interlock”?
The answer is basically three supplementary safety features and properties, in addition to safe monitoring of the position of the guard door:
1. A machinery movement can only start once the integrated position monitoring “re-ports” the closed position of the guard door AND a certain minimum latching force takes effect;
2. a machinery movement is stopped if this minimum latching force is interrupted dur-ing the process;
and
3. the (damage-free) wilful tearing open of a guard door during the process is “sanc-tioned” by a blocking time of 10 minutes.
These supplementary conditions must be satisfied by corresponding monitoring meas-ures in order to safeguard a personal protective function using interlocking devices with electromagnetic latching. They are only unnecessary and can be disregarded for process and machinery protection.
The Schmersal devices from the MZM 100 range naturally satisfy the very personal pro-tection requirements that have also been expressly confirmed in the type approval tests by DGUV, the German Social Accident Insurance (BG) and TÜV. Elsewhere – please permit us this dig - you should make specific enquiries about this!
Please use the information request on Page 34 et seq. if you would like to know more about electromagnetic interlocks from the MZM 100 range and other “members of the family”.
A contribution to safe cooperation between man and machine
Designing special operating modes on machines and production systems intelligently, i.e. so that they are user-friendly on the one hand but also safe, means avoiding unneces-sary hazard potentials and significantly reducing the motivation for manipulating protec-tive devices. The new variation of the solenoid interlock in the Schmersal range – Model AZM 200-D – makes a contribution here.
Its special feature is that it has 2 safe enable levels which can be analysed independently of each other. It operates once with the “interlocking device with latching” function, and once with the “interlocking device with-out latching” function. This means that a machine or mechanical plant operating in automatic mode can request guard door position and latching function (applica-tion 1) where this is necessary for safety or process-related reasons, but in a special operating mode just the guard door posi-tion (application 2).
In application (1), i.e. in automatic mode, a machine or mechanical plant cannot be accessed, for example until the hazardous overrun movements have come to a halt. The device acts as interlocking device with latching. By contrast an “authorised person” (an appropriately trained and au-thorised operator, maintenance technician or service engineer) can “run” the plant within the danger zone in application (2) after selecting the correct operating mode, e.g. set-up, programming, process moni-toring etc. The prerequisite for the special operating mode is that he has closed the guard door behind him, however, so that in the special operating mode the equipment only operates with the enable level “guard door closed” as interlocking device with-
Fig. 1: New version of the solenoid in-terlock AZM 200-D with two optionally actuated enable levels: 1 × as interlock-ing device with latching (PL “d”, CC 3, SIL 2); 1 × as interlocking device without latching (PL “e”, CC 4, SIL 3)
20 MRL-News – 33/11/11 MRL-News – 33/11/11 21
to “interlocking device without latching”, for example using an RFID operating mode selector switch. During synchronous time monitoring he would be registered to briefly bridge the guard door monitoring using an enabling device, i.e. to be able to open the guard door and close it again behind him immediately without interrupting automatic operating mode, and then take up his safe standing space.
By contrast an unauthorised person would be unable to enter the machine or mechani-cal plant unnoticed because the guard door monitoring would in the meantime be ac-tive again following the expiry of the short window. The operator himself can leave the danger zone again by going through the sequence described above in reverse order. With an interlocking device without latching it is also not a problem if the operator needs to be rescued from an improbable unplanned hazard. What is more he would be able to free himself, even if the actuator had been inserted into the de-vice by an external inter-vention. An additional installed escape release is available to him on one side in such a situa-tion (also see the PS on Page 23).
All control-related intercon-nections referred to above must, of course, be realised within the framework of safety-related parts of con-trol systems and taking the standard EN ISO 13 849-1 into consideration.
Some readers may be sur-prised at “all the things that are possible today. The “new” EC Machinery Di-rective (MD 2006/42/EC), which in particular opened up the area of intelligent operating modes, not least due to constructive influence by the German employers’ liability insurance associations, is the force behind this.
To understand this it is important to remember at all times that impractical operating concepts only motivate operators to manipulate protective devices. The work awaiting them has to be done after all. In any case this is the result of an empirical study pub-lished by the employers’ liability insurance associations in 2005 [1].
[1] Report “Manipulationen von Schutzeinrichtungen” (manipulation of protective devices); download at: www.dguv.de/ifa/de/pub/rep/pdf/rep05/manipulation_schutzeinrichtungen/ReportGesamt.pdf
out latching. From a safety-related point of view this ensures that an unauthorised third party cannot access the danger zone during the special operating mode without there being a safety-related STOP signal on the controller. On the other hand the operator can decide to leave the danger zone after completing his work or can do so at any time in the event of a critical situation (albeit likewise with the consequence of a safety-related STOP signal).
Known applications for which the new AZM 200-D solution is especially well-suited are in robot systems, and specifically the particularly critical T2 operation. Here the operator is protected from the full-speed operation of the robot by standing in a safe place in the robot cell, however the access of an unauthorised person would literally be “life-threatening” should the guard door monitoring be bridged and accessible in special operating mode, especially if the robot system was confusing or unclear.
However working from a secure position inside the machine plant while unauthorised persons are kept “outside the door” is also a familiar situation in integrated manufac-turing systems. This involves process monitoring from a safe place [1]. The authorised person can switch the safety guard from the function “interlocking device with latching”
[1] Also see EN ISO 11 161 with fundamental requirements relating to Integrated Manufacturing Systems (IMS)
22 MRL-News – 33/11/11 MRL-News – 33/11/11 23
Please use the information request on Seite 34 et seq. if you would like to know more about the solenoid interlock Model AZM 200-D.
PS: If you are interested in this subject we would be happy to welcome you as partici-pant at the Schmersal tec.nicum-Seminars K9/12 (Christoph Preuße, BGHM: Integrierte Fertigungssysteme) on 25.01.2012 in Wuppertal and on 03.07.2012 in Maulbronn/Ster-nenfels (also see page 29).
According to this study, 37 % of all protective devices are permanently or temporarily bridged, and there were estimates that 25 % of all machinery accidents, which “trans-lates” into 10 to 15 fatalities per year, can be put down to manipulated protective de-vices. It was also apparent from the result of this study that hardly any operators were “daredevils”, manipulating the devices “just for fun”; rather there were substantial, albeit subjective reasons, e.g. during set-up, when troubleshooting or during servicing.
The hope is also that deployment of the AZM 200-D with its double functionality will help to stem the critical bad habit of locking oneself inside an installation to perform a task there and to keep “others” away.
Frequency Increasing the risk of accidents
63%14%
23%
withouttempo-rarily
perma-nently
49%51%
Ja!Nein!
In your opinion, what percentage of protective devices on machines is perma-nently/temporarily manipulated?
In your opinion, what percentage of all manipulation to machinery or protective devices can result in accidents?
Accident causes Tolerance
75% (otherreasons)
25% (attributableto manipulation) 66% 34%
Nein!Ja!
In your opinion, what percentage of all industrial accidents can be attributed to manipulated protective devices?
What percentage of companies toler-ates manipulated machines or protective devices?
The “most important” results of an empirical employers’ liability insurance associa-tion investigation into the manipu-lation of protective devices
24 MRL-News – 33/11/11 MRL-News – 33/11/11 25
Collaborating robots are a new application field that was created in the course of revising and realigning the standards relating to industrial robots (in particular EN ISO 10 218-2) so that the respective strengths and weaknesses of the “human” and “machine” work sys-tems could be better balanced and especially to use robots to support people and take the load off them. The prerequisite for this, however, is that there is closer collaboration [1].
If you are surprised at the use of the word “collaboration”, which also has negative con-notations in German, and if you have been searching in vain for the word “cooperation”, the reason for this is simply that “cooperation” has already been used elsewhere in the new robot standard, where it refers to cooperation of robots amongst each other. Putting aside the historical context, the term collaboration today is used in several contexts such as in economics as a synonym for teamwork, very probably because in English texts the term teamwork is also represented by collaboration. As such a collaboration or team-work represents a strong kind of cooperation (quote from Wikipedia).
When planning a workplace that includes a collaborative robot, the user must perform a risk assessment based on regulatory principles – the Machinery Directive, standards for industrial robots – and must also incorporate the assessment on risks of injury through collisions between robots and people in the collaborating operation. In the standards that apply to industrial robots there are not sufficient safety requirements to evaluate these risks of injury, however.
On the initiative of the Expert Committee for Machine Construction, Production Systems and Steel Construction (MFS), the IFA (Institute for Occupational Safety and Health of the German Social Accident Insurance – DGUV) compiled the technological, medical/biomechanical, ergonomic and work schedule requirements relating to such workspaces in a development project. They supplement and define the requirements in standards and have been summarised in recommendations.
Result
The following table shows the limit values for forces and pressures and constants of body plasticity according to the body areas in the body model:
[1] If you are interested in this subject we would be happy to welcome you as participant at the Schmersal tec.nicum-Seminars K10/12 – “Safety requirements during the integration of industrial robots in machine installations and manufacturing systems – New EN ISO 10 218-2 2008 (draft)” on 19.01.2012 in Maulbronn/Sternenfels. Also see Page 29.
Risks of collision between man and machine
It is a bit of a breach of taboo, albeit well motivated, when employers’ liability insurance associations recommend courses of action that involve tolerable injury risks which can be attributed to the effects of stress caused by collisions between man and machine, in this case between man and robots. Clear limits are defined, however.
Tolerable in this sense refers only to injuries/risk of injuries to the skin and subcutaneous tissue which cannot lead to deeper penetration of the skin and the tissue with bleeding wounds. Fractures or other damage to the musculoskeletal system are already excluded. “Tolerable” should also not be understood as meaning that collisions are now “permit-ted”, but only that the aim is to contain any existing residual risks (see Figure).
Background
There are no longer any guards in certain work and collaboration rooms when collabo-rative robots are used so that a risk of collision between robot and person cannot be completely ruled out. Technical protective measures other than guards must therefore be used here to continuously determine the risk of collision and constantly minimise it as part of the robot control system, despite this a residual risk remains.
Maximum permissible body compression on reaching the limit force (relative to budoy surface)
Maximum body penetration(relative to body surface)
Detection path (path between detection point and body surface)
Specified distance to body surface(change from working speed to reduced speed)
Working speedBumping fromrobot part
Speed on contact
Reduced speed ofthe collision robot part
Speed to the detection point(start of the braking and reversing procedure)
Body surface(not compressed)
Reverse movementto home position
Body area left upper arm,collision point: outside of upper arm at shoulder height
26 MRL-News – 33/11/11 MRL-News – 33/11/11 27
QM system and MD 2006/42/EC
This is something that is often forgotten during discussions about implementing the “new” Machinery Directive MD 2006/42/EC because it is regarded as self-evident, but the fact is: if you place products on the market/put products into operation on your own responsibility within the scope of the MD 2006/42/EC, you need a QM system which corre-sponds to Annex VIII. This annex describes a conformity assessment procedure that the manufacturer must perform under Article 12 (2) for products which do not fall under Annex IV or also for products covered by Annex IV if he manufactures these ac-cording to a harmonised standard.
Whilst these requirements do not mean that one needs a QM system that is certified to ISO 9000 et seq., it is necessary to set down rules for how these requirements are satisfied. Final inspection records according to a specific model (possibly also interim inspection records) or acceptance protocols could form part of these.
In addition it is important to tie these in with documents required under Annex VII, and one critical aspect is whenever changes are made to a machine or mechanical installa-tion in situ, for example during trial operation. This “loop” must also be included in the procedure in a suitable manner if it is required in Annex VIII.
Body model – main and individual areas with coding
Limit values of requirement criteria
KHB KEB KQK STK DFP KK[N] [N] [N/cm2] [N/mm]
1. Head and neck
1.1 Skull/forehead 130 175 30 1501.2 Face 65 90 20 751.3 Neck (sides/neck) 145 190 50 501.4 Throat (front/larynx) 35 35 10 10
2. Torso 2.1 Back/shoulders 210 250 70 352.2 Chest 140 210 45 252.3 Stomach 110 160 35 102.4 Pelvis 180 250 75 252.5 Buttocks 210 250 80 15
3. Upper extremi-ties
3.1 Upper arm/elbow joint 150 190 50 303.2 Lower arm/wrist 160 220 50 403.3 Hand/finger 135 180 60 75
4. Lower extremi-ties
4.1 Thigh/knee 220 250 80 504.2 Calf 140 170 45 604.3 Feet/toes/ankle 125 160 45 75
KHB, name of the main body part with code; KEB, name of the individual body part; KQK, clamping/crushing force; STK, impact force; DFP, pressure and surface stress; KK, compression constant
CAUTION: The above table should be understood within the overall concept of the recommendations which you can obtain by searching for “collaborative robots, recommenda-tion, IFA” on Google.
ANNEX VIIIConformity assessment with internal production
checks during the manufacture of machinery
1. This Annex describes the procedure by which the responsible per-son, who carries out the obligations laid down in points 2 and 3 of this Annex, ensures and declares that the machinery concerned sat-isfies the relevant provisions of the Directive.
2. For each representative type of the series in question, the respon-sible person shall draw up the technical file referred to in Annex VII, part A.
3. The manufacturer must take all measures necessary in order that the manufacturing process ensures compliance of the manufactured machinery with the technical file referred to in Annex VII, part A, and with the provisions of the Directive.
28 MRL-News – 33/11/11 MRL-News – 33/11/11 29
Schmersal news
We would like to update you with news from the Schmersal Group.
The best way would be to visit us at the SPS/IPC/DRIVES 2011 in Nuremberg from 22.11.2011 to 24.11.2011. This will give you the opportunity to discuss specific new products, the current prod-uct range and interesting applications personally with our staff, and also to see them for yourself. We look forward to your visit.
You can find us in Hall 9, Stand No. 460.
✤
We would also be happy to give you our new “2011/2012 innovations” brochure, where you can find out about a wide range of new products and developments and their special features and properties.
Please use the reply on Page 34 et seq. if you are interest-ed in this information (keyword: 2011/2012 innovations).
✤
Last, but not least … the “2012 Schmersal tec.nicum” programme brochure has now been completed. NEW to the 2012 seminar programme is information on legal concepts and liability questions which are not precisely defined, on requirements for validation of safety-related parts of control systems and on the new Product Safety Act (ProdSG). Special interest topics and basic seminars on machinery safety have been updated.
tec.nicum-Seminars will be held in German language.
Again, please use the reply on Page 34 et seq. if you are interested in the programme brochure (keyword: 2012 Schmersal tec.nicum).
Sicherheit im System: Schutz für Mensch und Maschine. Neuheiten 2011/2012
Safe solutions for your industry
SchmersalSeminarprogrammfür Kunden und Mitarbeiter
To give you a better understanding, we cite the following extract from the Guidelines to MD 2006/42/EC:
“Annex VIII, number 2 refers to the obligation of the responsible person to compile a technical file according to Annex VII, part A, number 1. The technical file must include the basic health and safety protection measures that apply to the machinery and a de-scription of how these requirements have been satisfied. The term “representative type” is coterminous with the terms “type” or “model”.
It must be noted here that the technical file is stipulated both for series manufactured machinery and for single unit production of machinery. If modifications are made to the design of series manufactured machinery, for example if materials or components from different suppliers are installed or if design improvements have been made, the compli-ance of design aspects to which modifications have been made must be reassessed and the technical file updated accordingly..
According to Annex VIII, number 3, the manufacturer is obliged to ensure through suit-able measures that the manufacturing process guarantees that the machinery produced complies with the technical file and satisfies the applicable basic health and safety protection requirements. This involves the “internal production checks” referred to in the title of Annex VIII.”
If you wish more detailed information, reference is made to the article “Auswirkungen der Maschinenrichtlinie auf die Fertigung” in „Reusch: Praxishandbuch Maschinensi-cherheit – 47. Erg.-Lfg. – November 2010” (impact of the Machinery Directive on manu-facturing. However if you do not have access to or wish to order this loose leaf collection you will have get it from a library.
30 MRL-News – 33/11/11 MRL-News – 33/11/11 31
Schmersal expert forum
Once again we want to help take a broader view, and our expert forum is designed to do just this.
Functional machinery safety today and in 2030.
The year 2030 in the above heading merely stands for a medium to longer-term scenario. With the help of renowned experts, we would like to examine trends with you that can-not fail to have an influence on the design of machine safety, i.e. questions which ask the following:
• What changes to the man-machine interface are to be expected?
• What role will hybrid machine installations play and what safety requirements arise here?
• Will we need more or less or different safety technology in future? Where will it be important to offer new approaches? What influences will demographics and globalisa-tion have?
• Will there be new regulations on the obligations relating to producing proof and to inspection?
• What new functionalities will become possible due to new operating principles of technical safety devices?
• Which new requirements could/should be included in a new machinery directive?
The following experts will give lectures to get you started and will be around to take part in discussions:
• Dipl.-Ing. Berthold Heinke Wood and Metal Employers’ Liability Insurance Association (BGHM), Head of the Electrotechnical Competence Centre
• Dipl.-Ing. Ulrich Hochrein EDAG GmbH & Co. KGaA, Safety Engineer for Industrial Manufacturing Equipment
• Dipl.-Ing. Alois Hüning Wood and Metal Employers’ Liability Insurance Association (BGHM), Head of the Machine Tools and Production Systems competence centre
• Dr. Alfred Neudörfer Academic Director (retired) from the TU Darmstadt
• Dipl.-Ing. Karl-Heinz Lang Bergische Universität Wuppertal, Member of the Executive Board of the Institute for Occupational Health, Safety and Ergonomics e.V. (ASER)
• Prof. Dr. Ralf Pieper Bergische Universität Wuppertal, Head of the Safety and Quality Law field in the Safety Department
• Thomas Dahmen K.A. Schmersal GmbH, Wuppertal, Head of Product Management
Dates:
• 26.01.2012 (Hamburg)• 15.02.2012 (Wuppertal)• 08.03.2012 (Ulm)• 29.03.2012 (Erfurt)
This event will be held in German language.
Please use the online registration at http://marketing.schmersal.com/index.php?id=96 (or www.schmersal.com → Messen und Veranstaltungen → Informationen zur Maschinen-sicherheit aus erster Hand → Online-Anmeldung) if you would like to take part in the expert forum. Each begins at 9 a.m. (with a coffee to welcome you as from 8.30 a.m.) and ends in the early afternoon (with a break for coffee and lunch). We would then like to invite you to an informal exchange of ideas during a small reception.
© k
ablic
zech
- Fo
tolia
.com
32 MRL-News – 33/11/11 MRL-News – 33/11/11 33
New product from the Schmersal Group
Smaller than the standard: Z/T 196 position switches with safety function
In its Z/T 196 range, the Schmersal Group has developed new position switches for use in the so-called passive safety circuit in lifts, for limit switches and for position detection in classic machinery and plant engineering.
The devices are extremely compact and smaller than the standard switch described in EN 50 047.
With a height of just 20 mm and three possible cable or connector positions, in many cases the switch permits a reduction in the size of modules. At the same time it is com-patible with existing designs because it has the same connection dimensions as conven-tional standard switches.
The Z/T 196 switch range is available with different contact variations with snap or slow action. Due to a high quality contact system with inbuilt redundancy, the switch is espe-cially suitable for switching extra low voltage.
In terms of actuator the user can choose between plungers, roller plungers, angle levers and various roller and swivel levers. This permits versatile use in machines and lifts, so that it can claim to be “a real all-rounder”.
The switch is connected using an AMP positive lock connector, blade terminal 6.35 × 0.8 mm or four-pole standard line socket (M12). The user can also use the wiring service now offered by Schmersal and order the Z/T 196 with connecting cable in the desired length.
With these options the compact safety switchgear, which of course meets all require-ments set out in current standards applying to elevator technology and machinery safety, can be perfectly adapted to the application in question. It facilitates efficient series pro-duction and enables newly built lifts and machinery to be more compact due to its re-duced size.
Please use the information request on Page 34 et seq. if you would like to know more about the Model Z&T 196 position switch with safety function.
34 MRL-News – 33/11/11 MRL-News – 33/11/11 35
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36 MRL-News – 33/11/11
Elan Schaltelemente GmbH & Co. KG
Im Ostpark 2D-35435 Wettenberg
Telephone: +49 (0)641 9848-0Fax: +49 (0)641 9848-420
Email: [email protected]: www.elan.de · www.schmersal.com
