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Frequently asked questions

Safety Light Curtain Questions

PJ-V Series
1. Are safety light curtains suitable for guarding all types of machines?
Ans. No! Safety light curtains must only be used on machinery that can consistently and immediately stop anywhere in its cycle or stroke. Safety light curtains should never be used on a full revolution clutched power press or machine.

2. Is the PJ-V safety light curtain OSHA approved?
Ans. OSHA ( Occupational Safety and Health Administration ) does not approve products. OSHA sets safety standards which manufactures use as guidelines when designing products. Other organizations such as the American National Standards Institute ( ANSI ) also publish safety standards that are generally recognized by industry in the United States. KEYENCE light curtains meet or exceed these standards.

3. What is IEC61496?
Ans. With the advent of the European Common Market, safety regulations are being harmonized between all member nations.
The standard of concern to most safety light curtain users is IEC61496. This standard comes in two parts. Part 1 involves the general requirements and functional testing for a safety light curtain while Part 2 spells out specific requirements.

4. What is Category 4? What other Categories are there?
Category or Level 4 - A single fault in the control shall not lead to a loss of safety function(s). Whenever possible, the single fault shall be detected at or before the next demand on the safety function, or if this is not possible, then accumulation of faults shall not lead to a loss of safety functions.

Level 3 - A single fault in the control shall not lead to the loss of the safety function, and whenever practical, the single fault shall be detected. Some, but not all, faults shall be detected. The accumulation of undetected faults may lead to a dangerous output.

Level 2 - Safety functions shall be checked at least every start up of the machine. When a fault occurs between start up intervals, the safety function may not be performed, and the fault may lead to a dangerous situation at the machine. The fault is detected by the check.

Level 1 - Using well tried components and safety principles, improved reliability of the safety related functions may be achieved. When a fault occurs, the safety function may not be performed and may lead to a dangerous situation at the machine. Some faults remain undetected.

Level 0 - Point of hazard is safe.

5. What is the IP rating of the PJ-V?
Ans. The rating for the sensor head, PJ-V20, 21, 22 is IP-65. The rating for the controller is IP-20. This should be placed in an enclosure of at least IP-54.

6. How is the minimum object resolution determined for light curtains?
Ans. Minimum object resolution is determined by adding together the beam lens diameter and the beam spacing. Use of this formula allows users to make direct comparisons between different light curtains.
Minimum object resolution = Beam lens diameter + space between beams.

7. Once an obstruction is removed from the light curtain-sensing field, what does the curtain do?
Ans. If it is operating in the standard mode, the light curtain will reset itself and the stop signal will be removed from the guarded machinery. With "Lockout" mode operation enabled, the stop signal will not be removed until manually reset by an authorized person.

8. Can we have 5 meters of cable for the receiver and 17 meters of cable for the transmitter?
Ans. Yes, as long as the cable length for either the transmitter or receiver does not exceed 21.5 meters.

9. What is the maximum segments ( extensions ) the PJ-V can use?
Ans 1 Base unit and 7 extensions ( 6 PJ-V21 with 1 PJ-V22 or 7 PJ-V22 )

10. What is the response time if the extended controller ( PJ-V91) is used and the light curtains are both 1.2 meters in length?
Ans. 15ms MAX.

11. What is the typical service life of the FSD1, FSD2, SSD and AUX relays?
Mechanical: 10 Million operations or more.
Electrical: 100,000 operations or more.

12. What is FMEA?
Ans. FMEA stands for Failure Mode Effect Analysis, ( which is part of IEC61496, which is the old standard. The PJ-V passes the new standard IEC61916.) This process identifies what will happen in the event of a specific failure and helps our engineers design for control reliability.

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