Automation24 957901130 Safety Light Curtains User Guide
- June 9, 2024
- Automation24
Table of Contents
Automation24 957901130 Safety Light Curtains
Installation
Did you know that you need safety technology? Anyone who works with and on machines, automated systems or robots, is often not aware of the dangers involved. The potential impact on the health of all users can be devastating, however. As is so often the case, prevention is the best protection! The right safety technology is needed here. Why safety light curtains in particular are the best solution and what important selection criteria as well as installation information which needs to be taken into consideration can be found in this guide.
Why is safeguarding hazardous points with safety light curtains relevant for you?
Hazards from machines lurk around almost every corner in manufacturing
processes. A particularly high risk is posed by manual work and testing
stationssuchaspresses,cutting,bendingandpunchingmachines.Withoutappropriateprotectivemeasures
it can happen all too quickly that users come into contact with
movingmachineparts.Theconsequences:cuts,bruises,fractures,sprains or
even worse.
Topreventthisfromhappeninginthefirstplace,reliable detection of
fingers, hands and other limbs entering hazardous areas is essential. In
this way, the shutdown of dangerous
machinemovementscanbeinitiatedautomatically.Safety light curtains are
anidealsolutionforthis!
What are safety light curtains and how do they work?
Safety light curtains are one of a range of optoelectronic safety sensors.
They consist of a transmitter and a receiver unit and are similar
in their operating principle
tothroughbeamlightbarriersfromthefieldofphotoelectricsensors,whichareusedinparticularforpositiondetection.
A safety light curtain transmitter transmits a multitude of light beams
at defined distances to the receiver module. This creates a virtual and very
close-meshed barrier to demarcate or secure hazardous areas. As soon
as fingers, hands or other
limbspenetratethisbarrierandinterruptthelightbeams,thehazardous
movements can be automatically switched off.
Anotherimportantdifferencetostandardlightbarriersisthatsafetylightcurtains,as
safety sensors, have corresponding safety technology and/or features to
prevent unexpected failures. For example, they have redundant OSSD outputs
that pass on switching states to corresponding safety controllers or
safety relay modules. OSSD is the abbreviation for the full name
„Output Signal Switching Device“. These outputs send out periodic test
pulsestodetectpossibleshortcircuits.Inaddition,safetylightcurtainshave
self-test functionsthatalsocounteractsystemfailure.
What are the selection criteria for a suitable safety light curtain for your application?
The selection of a suitable safety light curtain is very simple. You only need to consider these three to four selection criteria:
| Criteria | Descr |
|---|
ΠResolution
| Describes the distance between the light beams. This defines which part of the body can be relia- bly detected.
Finger protection: 14 mm Hand protection: 30 mm
Protection field height| Stands for the height of the area to be protected by the safety light curtain. This depends on the size of the accessible danger area.
Ž Protection type
| Provides information about the internal structure of the light curtain to safeguard against unex- pected failures. A distinction is made in particular between type 2 and type 4 safety light curtains (rarely type 3).
The higher the type, the higher the Performance Level (PL) that can be met according to the DIN EN ISO 12849 standard.
Type 4 light curtains meet the requirements up to PLe.
Nowadays, type 4 light curtains have established themselves as the standard and light curtains with lower types are increasingly being displaced from the market.
Range
(optional)
| Describes the maximum distance between trans- mitter and receiver. However, the maximum range of most safety light curtains is usually so large that it only plays a role in very few applications. There- fore, it is considered an optional criterion.
There are other design features in which safety light curtains can differ. These include, for example, an extremely narrow type or the elimination of a dead zone. However, these features are relevant for very few industrial applications. In most cases, the use of light curtains with standard functions is perfectly adequate.
Safety light curtains vs. safety light grids
Did you know that? It is not uncommon for safety light curtains and safety
light grids to be misleadingly used as synonymous terms. This is a
fallacy, however. Although outwardly they look very similar to each other,
there are essential differences with regard to their characteristics
and suitable areas of application.
One of the most significant differences is the resolution. While light curtains create a multitude of light beams at a small distance,light grids usually create only two to four light beams spaced at significantly larger distances.
This is due to the different purposes for which they are designed.
While safety light curtains are used for finger and hand protection detection
at hazardous locations, light grids are used for more extensive area
protection, whereby body detection by means of fewer light beams is
sufficient.
Area safeguard are often relevant in logistics applications. In this context, muting is also an important requested feature, which makes it possible to bridge light grids for a short time in order, for example, to move pallets out of the hazardous area without bringing system processes to a standstill. Immediately after the pallet transport, the light grid is reactivated to detect persons entering the danger zone again.
Hazardous location safeguarding with light curtains does not require a muting function in most cases, as transporting materials out of the danger zone is rarely necessary here.
How do you install and test safety light curtains correctly?
Before safety light curtains can be used, it is important that they are first installed correctly and that their functionality is tested.
Light curtain safety distance – calculation formula:
S = min. safety distance
K = approach speed
t1 = response time of the light curtain
t2 = response time of the machine until standstill
C = maximum distance of undetected movement behind light curtain
K and C set the standard here.
K as reaching speed = 2,000 mm/s,
if result of this formula > 500 mm,
K = 1,600 mm/s (walking speed) may be used
C equals 8 * (resolution (d) – 14 mm)
i.e. when using a 14 mm light curtain, C = 0 mm,and with a 30 mm light curtain
C = 128 mm
The following formulas are derived from this:
For light curtains with 14 mm resolution: S = 2,000 mm/s * (t1+t2)
For light curtains with 30 mm resolution: S = 2,000 mm/s * (t1+t2) + 128 mm
How do you install and test safety light curtains correctly?
Anti-circumvention protection
When correctly installing a safety light curtain, it is imperative that limbs
entering hazardous areas are detected without exception. The prerequisite for
this is the correct selection of the appropriate protection field height so
that it is not even possible to reach past the light curtain into the danger
zone.
Furthermore, it must be ensured that no one can be present behind the light curtain unnoticed. If the safety distance in an application needs to be very large, the additional installation of a horizontal light curtain is essential.
Correct vs. impermissible mounting:
Alignment aid
Since the light beams transmitted by the light curtain are not visible,
aligning the transmitter and receiver over longer distances can prove very
difficult. Laser pointers mounted on the transmitter can help here.
Vibration protection
Safety light curtains are designed to cause machines to be switched off as
soon as the light beam transmitted by the transmitter cannot reach the
receiver. However, this is a hindrance with strongly vibrating machines, as
the vibration may cause the transmitter and receiver to be briefly offset from
each other. Vibration-heavy applications, therefore, require the use of
special vibration dampers to prevent false tripping.
Daily function tests with test rods
To trust is good, to check is better. This also applies to safety light
curtains! To verify correct functionality and reduce the risk of liability in
the event of a malfunction, a daily function test of each safety light curtain
is recommended.
For this purpose, a test rod is passed through the protection field to check the correct interruption of the light curtain beams. The test rod must have the diameter of the resolution of the relevant light curtain.
Protect yourself and your employees with light curtains
You now know how important it is to have adequate point-of-operation guarding and why safety light curtains in particular are a great solution here. In many online shops you will find designs for every need and budget. Most applications can be covered with basic light curtains. For example Automation24 offers an appealing range from Datalogic for standard requirements. Particularly good prices and fast delivery capabilities go hand in hand with this offer.
Safety technology must not be a luxury. Do not take your health or the health of your employees lightly and insist on reliable safety light curtains for your protection! With this compact guidebook, you are now ideally prepared, to choose the right safety light curtain for your application and install it in accordance with the standards.
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Correct vs. impermissible mounting:
Fig. 7: Installation at a low
safety distance
Fig. 7.1: It must not be
possible
to reach past a
safety light curtain.
Fig. 8: At a very high safety
distance, the horizontal
installation
of a safety light
curtain is required.
Fig. 8.1: An undetected stay
behind the light curtain must
not be possible.
Useful things to know, selection guide & installation tips
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