Key Switch (S, LCU, SCU) – Isolating Hazardous Electrical Energy
Isolation of Hazardous Energy | Key Switch | Environments | Lock Operated Key Switch(es) (LCU) | Knob Operated Key Switch(es) (SCU)
Key Switch – Isolation of Hazardous Energy (with Trapped Key)
The Key Switch can be used for electrical isolation. Electrical (and resulting kinetic) energy is used to mobalise heavy loads, actuate machinery, and perform a host of different tasks in automation and manufacturing. This can be incredibly hazardous to personnel operating around these processes and why isolation is a key factor to many trapped key solutions.
Key Switch(es) are a tried and tested method of mechanically safeguarding dangerous machines and hazardous processes. Mechanical keys eliminate most of the electrical wiring associated with other types of interlocks making it cost effective to install and maintain.
Control interlocking, using keys to change the state of switch contacts, is one method, tried and tested, to isolate hazardous electrical energy.
A Key switch installed for hazardous electrical energy isolation
In the image in Figure 1, a key operated switch is used to swap the state of switch contacts which is used to isolate electrical energy to a particular system. Upon isolation, this key is freed allowing it to be used for controlled access to a particular safeguarded space. The key ensures that access to this space is only possible when the hazard is isolated, and the hazard is only able to be reinstated when the key is returned.
The Key Operated Switch (S-)
Example Part Number: S-CLIS–A02022*
The key operated switch is ideal for use in harsh environments for isolation of power to machinery or switching current. Standard switches come in a range of switch currents; 20A, 32A & 63A and with switch contacts (with key inserted) of 2 NO/2NC or 4NC (NO – Normally Open; NC – Normally Closed).
* 20A – A020.. ; 32A – A032.. ; 63A – A063.. ; 2NO/2NC – A..22 ; 4NC – A..40
When operating in harsh environments, we recommend lock protection for switches to prevent ingress of dust and dirt. In the images below, on the right the lock protection can be padlocked for lockout/tagout procedures.
CLDC – Standard Dustcover | PLDC – Padlock-able Dustcover
Designing the Right Switch for your Environment
Switches can be supplied for mounting within an existing enclosure, or pre-mounted in an enclosure. Both options are offered with up to ingress protection IP65 & IP67.
S-CLIS-A02022 | Key Switch with 20A 2NO 2NC contacts for installation into an existing panel or enclosure
S-CLIS-A02022-WP | Weatherproof: -WP to provide protection up to IP65 and IP67 for installation into an existing panel or enclosure
S-CLIS-A02022-EM | Enclosure Mounted: -EM to pre-mount the switch into an robust metal-alloy enclosure for up to IP65 and IP67.
S-CLSS-A02022-EMS | Stainless Steel Enclosure: -EMS to pre-mount the switch into a full stainless steel enclosure for up to IP65 and IP67
Key Exchange with a Lock Controlled Unit (LCU)
The process of switch isolation can be integrated into a key exchange with the Lock Control Unit or LCU
Example Part Number | LCU2-2-0-CLIS-V-A02022-H01CB (left) ; LCU4-1-3-CLIN-V-A02022-V01CFB (right)
The lock controlled unit can be installed within an existing panel or enclosure (left image above), or supplied pre-mounted into an enclosure (right image above). Enclosures are offered in both painted mild steel and stainless steel.
Common configuration | LCU2-2-0-CLIS-V-A02022-H01CFR
LCU2 (two locks total) ; 2 (switch operated on key removed from first Normally In Lock) ; CLIS (Lock with Dust protection cover) ; V (sequence type) ; A02022 (switch behind first lock, 20A, 2 NO / 2NC contacts) ; H01 (Horizontal one row) ; CFR (cam operated steel fabricated enclosure painted red)
Switch Controlled Unit (SCU) – Knob operated Switch
Isolation can be controlled via a switch with the Switch Control Unit or SCU.
Please note that red and yellow switches should only be used for emergency stop/emergency stop off for applications where operation performs full stop at full speed (for all hazardous energy sources). Where switches are used for isolation, these should be grey and black.
Example Part Number | SCU1-1-0-CLIS-V-A02022-H01CB
The switch controlled unit (as with the LCU) can be installed within an existing panel or enclosure (images shown above), or supplied pre-mounted into an enclosure. Enclosures are offered in both painted mild steel and stainless steel.
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