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

	Dangerous
M	area

Penetration way

Reference plan

s
^ 1
	Dangerous
II	area
	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)