With the standard position switches, mechanical positions of moved machine parts are converted into electrical signals. Through their modular and uniform design and large number of variants, the devices can comply with practically all requirements in industry.

Devices are available with enclosure versions to suit the particular ambient conditions. Different control tasks can be performed with the best contact blocks suited for the particular purpose. And many different actuator variants are available to match the mechanical configuration of the moved machined parts. Dimensions, fixing points and characteristics are largely in accordance with the EN 50041 or EN 50047 standards.

The devices are suitable for use in any climate.

Standards

IEC/EN 60947-5-1.

The "total insulation" protective measure is guaranteed by the plastic enclosure when using plastic screw-glands.

Safety position switches

For controls according to IEC/EN 60204-1, the devices can be used as a safety position switch. They comply with the standard EN ISO 14119. A TГњV certificate is available. To secure position switches against changes in their position, keyed techniques must be employed on installation.

Safety circuits

The IEC/EN 60947-5-1 standard requires positive opening of the NC contacts. In other words, for the purposes of personal safety, the assured opening of NC contacts is expressly stipulated for the electrical equipment of machines in all safety circuits and marked in accordance with the IEC 60947-5-1 standard with the symbol (–>).

Category 2 according to EN ISO 13849-1 can be attained with 3SE5 position switches with (–>), and category 3 or 4 when using an additional position switch, if the corresponding fail-safe evaluation units are selected and correctly connected. Example: 3SK or 3TK28 safety relays or the corresponding devices from the ASIsafe, SIMATIC or SINUMERIK programs. The operating mechanisms (actuators) must also be connected to the enclosure by keyed techniques. The corresponding operating mechanisms are marked in the catalog with (–>).

Contacts for each application

Snap-action contacts: NC and NO contacts switch simultaneously – regardless of the actuating speed (v_min = 0.01 m/s) and contact erosion.

Slow-action contacts: Distance differential between "NC contact opens" and "NO contact closes"; the switching speed is the same as or proportional to the actuating speed (v_min = 0.4 m/s).

Slow-action contacts with make-before-break: e.g. suitable for adding a second function to a sequence control.

Operating mechanisms for each application

Standard, rounded and roller plungers

• Operation in direction of the plunger axis or in case of roller plunger with bar at right angles to the plunger axis
• The roller plunger is recommended for lateral actuation and relatively long overtravel.

Roller levers and angular roller levers

• For actuators made of finely ground steel in the form of cams, straight-edges (approach angle 30°) or cam disks

Spring rod

• Can be used for undefined actuations and changing starting conditions
• Starting from any direction is possible

Twist levers and rod levers

• For a high starting speed (v = 1.5 m/s)
• Variety of starting options
• Insensitive to oil, grinding dust, ice and coarse-grained material
• Adjustment of the lever in increments of 10°
• Can be set with left or right switching

Fork levers

• Switchable in two directions
• Latching actuator
• For reciprocating movements

Monitoring with fail-safe evaluation units from the 3SK and 3RK3 series

Safe evaluation units			Maximum achievable safety level according to type of switch
			Compact	Standard	Hinge	Separate actuator	Tumbler
3SK	3RK3		3SE54(в†’)	3SE51 /3SE52(в†’)	3SE51 /3SE52(в†’)	3SE51 /3SE52(в†’)	3SE53(в†’)
Use of only one position/safety switch
Monitoring with 1 contact: 1 x NC contact			SIL 1 / PL c
Monitoring with 2 contacts: 2 x NC contact or 1 x NC contact + 1 x NO contact			SIL 1 / PL c		SIL 2 / PL d
Use of a second position/safety switch
Standard switch		3SE51/3SE52	SIL 3 / PL e
Safety switch / hinge switch		3SE51/3SE52
Safety switch with separate actuator		3SE51/3SE52
Safety switches with tumbler		3SE53

Note

Taking account of certain fault exclusions (e.g. actuator breakage), use of just one hinge switch or a switch with separate actuator with or without tumbler up to SIL 2 or PL d is possible as described in the table.

Since the machine manufacturer must provide proof of fault exclusion, the component manufacturer is unable to carry out a definitive assessment of the measures taken.

For more information, see: https://support.industry.siemens.com/cs/ww/en/view/35443942

The maximum achievable SIL or PL always depends on other assumptions as well. Factors to be taken into account include the DC (Declaration), the CCF (*), and the number of actuations.

Information on the safe evaluation units and an introduction to safety systems, see "Safety Technology".