Locking mechanism for heavy machine doors: a bolt thrown into a guard-locking device, rated 7,500–10,000 N, and the padlock that keeps the bolt out while someone is inside

01

10,000 N FZh against 13,000 N Fmax, and 3,000 N once a handle module carries the load

Two forces appear on a bolt lock's data sheet, and only one is the rating. Schmersal lists its AZM400 bistable, motor-driven bolt interlock with a holding force FZh of 10,000 N in accordance with EN ISO 14119 and a maximum holding force Fmax of 13,000 N. [1] Editorial calculation: Fmax is 1.3 times FZh; compare locks on FZh.

Pilz gives a safe holding force of up to 7,500 N for PSENmlock with its actuator, but 3,000 N on swing doors and 2,000 N on sliding doors when the door handle module, with its integrated actuator and escape release, is fitted. [2] Editorial calculation: with the handle module the rated holding force is 40% of the bare actuator figure on a swing door and about 27% on a sliding door, so the force to quote is the one for the parts actually fitted. The 30 N figure is listed separately as an integrated latching force; it is not one of the holding-force ratings. [2]

Both devices state PL e for interlocking and for guard locking: Schmersal gives PL e / Cat. 4 / SIL 3 for both functions, [1] Pilz safe interlocking and safe guard locking up to PL e / SIL 3. [2] Both lock bistably: the AZM400 is motor-driven, [1] and PSENmlock uses a bistable magnet so that the guard locking holds without voltage. [2]

State the force the door can see when locked (people pushing, a falling part, a pressure pulse) and whether a handle module transmits it; ask for FZh to EN ISO 14119 for that arrangement.

02

1 to 7 mm gap, 2° angle, ±3 mm vertical offset, and what 100 N of side load does to the bolt's life

A bolt has to find its hole every time the door closes, so the data sheet sets the window. Schmersal allows 1 to 7 mm between the AZM400 and its actuator and up to 2° angular misalignment; Pilz allows a maximum vertical offset of ±3 mm for PSENmlock, and offers a 10° actuator adapter for small doors of 300 to 500 mm. [1] [2]

Side load on the bolt is the life-limiting case. Schmersal gives the AZM400 a minimum mechanical life of 1,000,000 operations, but 100,000 operations where the bolt sees a lateral force of 100 N; the bolt can still be withdrawn against a lateral force of up to 300 N on a locked door, a limit that does not apply to the emergency exit, Bowden cable or manual release. [1] Editorial calculation: 100 N of side load cuts the rated life to a tenth. A door locked and unlocked 200 times a day reaches 100,000 operations in 500 days, about 1.4 years, against about 13.7 years at 1,000,000.

The motor sets a cycle limit as well: Schmersal gives a minimum open/close cycle of 3 s, a minimum average cycle time of 20 s in continuous operation, a 600 mA peak for 100 ms while the bolt moves, and an ambient range of −20 to +55 °C. [1] Pilz gives 0 to 55 °C for PSENmlock and IP67. [2] Editorial calculation: a 20 s average cycle allows at most 180 lock–unlock cycles per hour in continuous operation, enough for a manned door but a constraint if an automatic door is locked every machine cycle.

Measure the door's sag and the gap between door and frame at the lock position when the door is pushed and pulled; if it falls outside 1–7 mm or ±3 mm, fix the hinges or striker before fitting the lock.

03

Padlocking the bolt out: Pilz's lockout bar for five locks, and where OSHA draws the line

A person who goes through the door into the machine needs to stop anyone from closing and locking it behind them. Pilz's PSENmlock door handle module has a lockout bar for up to five locks to prevent restart, a yellow outer handle that extends the actuator, and a red inner handle that works the escape release. [2]

Pilz notes a reset rule that follows from EN ISO 14119: on PSENmlock versions with automatic reset, an external emergency release cannot be used, because the emergency release must always be reset with a tool or another measure such as a power reset. [2]

A padlocked bolt is not lockout in OSHA's sense. 29 CFR 1910.147 defines an energy isolating device as a mechanical device that physically prevents the transmission or release of energy, such as a disconnect switch or line valve, and states that push buttons, selector switches and other control circuit type devices are not energy isolating devices; lockout means a lock placed on an energy isolating device. [3] Editorial note: a bolt lock reports to the safety controller and acts through the control circuit, so for servicing under the OSHA standard the energy isolating devices still have to be locked out, each authorized employee with a personal lock where a group lockout is used. [3]

OSHA also sets what a lock attachment must withstand: lockout devices must be substantial enough to prevent removal without excessive force or tools such as bolt cutters, and tagout attachment means must have a minimum unlocking strength of no less than 50 pounds. [3] Editorial calculation: 50 lb is about 222 N.

04

Data for a bolt-type door locking mechanism

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Door: [hinged or sliding; weight; leaf width; profile size]
Load on the locked door: [N, from people, parts or pressure]
Required FZh: [N to EN ISO 14119, for the parts fitted]
Alignment: [gap door to frame at the lock; sag; angular misalignment]
Operation rate: [lock–unlock cycles per day; continuous automatic cycling?]
Release: [manual release; escape release from inside; emergency release; reset by tool or power reset]
Lockout: [number of padlock positions on the handle or bolt]
Safety level: [PL / category / SIL for interlocking and for guard locking]
Environment: [temperature range; IP rating]

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