FEAT RE MAC FEA ATURE
MACHINERY SAFET Y
SAFETY
MAKING YOUR PRESENC E FELT FOR SAFETY’ S AK E
KING YOUR PRESENCE FELT FOR SAFETY’S SAKE
Implementing operator safety via protective devices can often be at the expense of productivity. rkin is a
plementing operator safety via protective
devices can often be at the expense of productivity. Piece working is a particular case in poiint.nt. However, a simple safety innovation has the potential to transform the experience of operators, ile incre sin rtin
rticu How ver, a si case in safety i novation has the
poten ial to transform th experience of operators, while increasing productivity by up to 40 per cent. Dr Martin Kidman, SICK UK’s product specialist for machinery safety and FS Engineer (TUV Rheinland 3017/16), outl in
tiv ty b to r ce SICK UK product specialist for
for piece w rki g processes tool is from the front with the two-hand
control being used as a ‘remote-hold measure’. The hazard may still be
T
he production of any stamped, guillotined, pressed, drilled, sawn,
cut, formed, screwed or s components may depend
,
on piece work. haped
If workers are rewarded for maximum productivity there is an age-old battle between speed and safety.
It’s a familiar and common process: An operator inserts a component or sub- assembly into amachine, and then once it has beenmachined replaces it with the next item. It’s an operation that usually requires some kind of protective device. The required PL/SIL of the safety function incorporating the protective device will be dependent on the risk associated with the machine and any relevan t standards; fo r presses it would normally be a PLe/SIL3 solution. The problemis that safety systems introduced to protect operators
speed at which the cycle i can sometimes dramatica
PLe/SIL3 solution and can
s completed. lly limit the
technique is available that The good news is that a
actually increase provides a simple
cycle speeds and boost pr oduction . HANDS AND FINGERS AT RISK HANDS AND FINGERS AT RISK
A typical work process involves inserting a piece into a tool and activating a cycle by pressing and holding down a two-hand control, compliant to EN 574. The two- hand control prevents the operator from inserting his hands into themachine. Usually protected on three sides by physical guards, access to the machine
26 26 DECEMBER/JANUAR 201 ANUARY 2017 | AU AUTOMA MAT ATION
Using safet Using safety ly lightight cur ains with safet
L3
curtains with safety controllers can provide protection up to Le/SIL3
controllers can provide protection up to PLe/
reached if the control device is activated, but two-hand controls are designed and installed such that no body part can be in the hazardous zone at the same time as using it. However, depending on risk assessment and the requirements in any local, national or international standards, additional devices such as foot pedals and/or safety light curtains may be required to protect a second person from reaching in. Of course, if there is a chance of parts being emitted from a machine then a suitable physical guard must be used.
EN 574 specifies the safety
requirements for two-hand control devices and has requirement s such as; they should be designed so that the operator must use both hands for the same time period and it must not be possible to use one hand or a hand and an elbow to activate the device. Also, an output signal should be generated only when both switches on the control device are actuated with 0.5 seconds of each other. The standard contains many more additions which depend on the type of device selected (Type I, Type IIIB etc.) and the type is selected base d on a number of factors including the hazard, the risk, experience and C-standards - all of which this article does not cover. This solution requires the installation of large, robust, two-hand control devices chines and footprint.
can dramatically increase the to be mounted in front of ma
achi ery safety and FS Engineer (TUV Rheinland #13017/16), outlines the principles of Presence Sensing Device Initiation and what it could mean for piece working processe s
ce Initiatio
es the pri ciples of Presence it c o
Ergonomically, it can induce repetitive strain to arms and shoulders with consequent damage to the employee’s health and also adds additional time to the process.
An alternative systemcould be a
physical guard that must be closed before operation of the machine. While it may protect operators this solution also limit s operating speeds since the machine would have to be reset every time the guard is opened and closed. Downtime could be another issue due to repeated use of electromechanical devices which would wear and get damaged.
,
These are a few of the reasons that safety has a reputation as a barrier to productivity, and can be regarded with irritation by both e mployee and employer .
BREAK DOWN HE PRODUCTIVITY
BREAK DOWN THE BARRIERS PRODUC IVITY
ARRIERS TO
There is an approach to safe guarding a machine for piece work that is already available and is being used globally achieving increases in productivity of up to 40 per cent.
This innovation is called ‘Presence Sensing Device Initiation’ (PDSI). It’s a simple solution using safety light curtains with safety controllers and can provide protection up to PLe /SIL3 It quickly pays for itself though increased productivity and there is less equipment involved. Any attempts at manipulation are a
.
disincentive because they would actually slow operating speeds down. PSDI can be implemented as long as it is not possible to enter amachine or cross through and
/AUTOMATION AT /AUTOMATION
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