mm
Choice of a safety system
CATEGORIE
SI
Annexe B of EN954-1 standard gives a first estimate to define the categories of the different parts of control system according to 3 parameters (for an harsher estimate of the risk, we will draw on EN 1050 standard):
S: seriousness of caused lesion
- SI : slight lesion (which is reversible)
- S2 : serious lesion (which is irreversible), death included F : Frequency and / or exposure period to the dangerous phenomenon
- F1 : from rare to quite frequent and / or short exposure period
- F2 : from frequent to continuous and / or long exposure period P : Possibility to avoid dangerous phenomenon
-PI: possible on certain conditions O
- P2 : rarely possible 0
:
0
Oversized measures compared with the risk Possible categories
Possible categories which need additional measures
^ 2 To define the safety category
EN6I496 standard regarding to equipment for electrosensitive protection, defines two types of safety light curtains (ESPE) ESPE type 2 and 4 have respectively to comply with the rules for control system's parts category 2 and category 4, according to EN954-I standard.EN954-1 standard defines these categories as behaviour categories in case of defect in control systems regarding to safety:
Category 2 system : the appearance of a defect can involve permanent or transitional loss of safety function during the interval between 2 controls. However the control has to detect the loss of safety function.
Category 4 system has a better behaviour concerning the defects tolerance because the defects accumulation has been taken into consideration.
^ 3 To define the area to protect
The characteristics which have lo be taken inlo account regarding to ESPE are protected height and range of the equipment.
{ 4 To define the type of" installation
Detection of the finger Detection of the hand
j^l Detection of a person in the dangerous area
Jj^ Detection of a person intrusion in the dangerous area
Without a specific standard for the machine, or when this standard doesn't specify a minimum distance, then it is proper to use the formulas of EN999 standard and to calculate the minimum distance for the used type of safety equipment. Generally speaking, we distinguishes 3 types of approach :
Penetration wav
Penetration way
Reference plan
| s | |
| ^ 1 | |
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| | Dangerous |
| II | area |
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| | Reference plan |
Penel ration way
Dangerous area
Reference plan
Multi-beams ESPE
d < 40mm S = 2000T + 8 x (d - 14) With S minimum > 100mm If S > 500mm
Choose S = I600T + 8 x (d - 14) In this case S couldn't be < 500mm
40<d<70mmS=1600T + 850
The height of the lowest beam < 300mm
The height of the highest beam ^ 900mm
d>70mmS= 1600T + 850
Multi-beams ESPE
S= I600T +(1200-0,4 x ii) With 1200- 0,4 xH>850mm
I5x(d-50)<H< 1000mm When H > 300mm we have to take into account that a non-detected risk of underneath access exists. For H given d<H/15 + 50 Considering that maximum H have to be
of 1000mm, the limits for ESPE detection capability are:
with H = 1000mm. d < 116mm with H = 0mm, d < 50mm
If ß > 30°, see perpendicular approach, d < (H/15) + 50 applies to the lowest beam
If ß < 30°, see parallel approach, S applies t(
d : detection sensitivity (in mm) T : response time of the safety chain's equipments (in seconds) S : distance (in mm)