Allen-Bradley / Guardmaster safety

On a 440G-LZ, operating the auxiliary release causes a fault condition and the switch will not reset until the power is cycled. That is designed behaviour, and it gets guard locking switches replaced unnecessarily.

Guardmaster is the Allen-Bradley machine safety range. Safety components are assessed and certified as part of a machine, so a substitution is not just a commercial decision.

Read the important note near the bottom of this page before ordering a safety replacement.

The 440 bulletins

Guard locking: partial body or full body access

The selection criterion that decides which 440G family a machine needs, and it is not about the door size.

Full body access changes the requirements

If a person can get their whole body inside the guarded area, they can be shut in.

That is why the 440G-MZ carries an escape release option: a means of opening the guard from the inside. A partial-access switch has no such need and no such feature.

So a 440G-LZ is not a substitute for a 440G-MZ on a full body access door, whatever the holding force comparison says.

The MZ also tolerates more guard misalignment, which matters on a large or sagging door.

The auxiliary release faults the switch

Rockwell states it plainly: operation of the auxiliary release causes a fault condition, and to reset the switch you cycle the power.

So a guard locking switch that has gone into fault after someone used the manual release is not broken. Cycle the power before ordering anything.

That behaviour exists so a defeated lock cannot quietly go unnoticed.

Two installation warnings from Rockwell

Both are about defeat and both are worth checking on an existing installation.

If the actuator can be lifted clear of the bolt, the lock can be defeated without tools. That is an installation geometry problem rather than a parts problem, and it is worth looking at on any door that has been rehung.

Unique actuators

The 440G-LZ supports configuring unique actuators, so a switch accepts only the specific actuator taught to it.

That is what stops a guard being defeated with a spare actuator taped to the frame. It also means a replacement actuator has to be taught in, and a replacement switch has to learn the existing one.

Tell us whether the installation uses unique actuators. Same principle as the SICK STR1 coding levels on our SICK safety switch page.

Power to lock and power to release

The principle that decides what happens in a power cut, and the two are opposite.

Rockwell describes the 440G-MT as locking the guard closed until power is isolated while the guard is open, which is the positive mode behaviour.

These are not interchangeable and the choice is a risk assessment decision. A power-to-lock device on a flywheel that coasts for a minute, or a power-to-release device where someone could be shut in, are both wrong in serious ways.

Check the existing device before ordering. It is the single most important characteristic of a guard locking switch and it is not obvious from the outside.

Interlock switches, the 440K range

Tongue operated switches, and the contact configuration is in the number.

A 440K-T11090 is a Trojan 5 tongue interlock with:

Contact count is not a preference

The safety contacts are the safety function and the auxiliary is not. A switch with 2 NC safety plus 1 NO auxiliary is not interchangeable with one that has a different arrangement, because the circuit was wired to what was there.

Break before make matters too. On a safety contact it ensures the safety circuit opens before any auxiliary makes.

The Trojan family runs alongside TLS guard locking and T15 tongue switches, with GD2 variants across several of them.

Actuators are separate parts

The same trap as every interlock and non-contact device on this site.

The switch and the actuator are separately ordered and separately damaged.

On a unique-coded switch, a new actuator has to be taught in. On a standard-coded one it does not.

Tell us which half you need. Actuators are a fraction of the cost of a switch.

SensaGuard, the 440N range

Non-contact RFID switches, and the standard answer where a door is hard to align.

Why non-contact switches get fitted

If a guard is nuisance-tripping because the door has dropped, a non-contact switch is the fix. Adjusting the door is better and not always possible.

And a stainless variant is not a cosmetic choice. In a meat or dairy plant a standard housing corrodes, and the failure looks like a device fault rather than a specification error.

Fault masking on series-wired switches

Worth stating because it affects installations that look correct.

When contact-based safety switches are wired in plain series, a fault in one can be hidden by the others. The chain still opens when a guard opens, so nothing looks wrong, and the fault detection the safety level depended on is gone.

So if a machine has six guard switches daisy-chained into one input, that is worth raising. The fix is OSSD devices or individual monitoring rather than more relays.

Light curtains, the 440L and 445L ranges

GuardShield light curtains, and the protective field height reads straight off the number.

The four digits are the protective field height in millimetres. The P4 denotes the type rating, and the letters around it carry the resolution and function.

Resolution and height are both fixed by the assessment

Resolution sets the mounting distance under ISO 13855. So a coarser curtain is not a cheaper version of a finer one; it is a different safety distance.

And a shorter curtain does not cover the opening the original did. Both numbers have to match.

Sender and receiver

A light curtain is two units. They are separately ordered and separately damaged, and a forklift usually only hits one end.

Tell us which half you need. Cables and mounting brackets are separate again.

The 442L range covers safety laser scanners, for area protection where a curtain cannot follow the shape. As on every brand, a scanner is a lower performance level than a curtain, so the two are not alternatives.

Two generations of safety relay

This is the first thing to work out on a relay replacement.

GSR, the current modular family

The 440R-S13R2 CI relay is directly compatible with the MSR127. If an MSR127 has failed and cannot be sourced, that is the named path forward.

MSR, the earlier family

The MSR127TP is Category 4 rated and takes one 2 NC input, or one 1 NO and 1 NC input, plus one light curtain input.

The MSR300 family is the expandable modular option, connecting multiple input modules to a base unit with logic across several independent outputs. MSR35H, MSR41 and MSR42 also turn up on New Zealand plant.

Single Wire Safety, and the 30 metre limit

GSR relays use Single Wire Safety, letting multiple relays coordinate over a single wire plus a common ground.

Rockwell states the wire must be less than 30 metres.

That is a hard limit and it constrains how a distributed safety system is laid out across a long line. Worth knowing at design stage rather than at commissioning.

GSR relays can also connect to an EtherNet/IP module without additional wiring, which is usually the better answer over longer distances.

Read the diagnostics before ordering

Guardmaster devices report more than most people use.

The blink pattern frequently points at field wiring rather than the device. On a safety relay that will not reset, read it before replacing anything.

Cordsets, and the length code

Useful because the cable is often the actual fault and the numbering is readable.

For the 440G-LZ, the I/O cordset is the 889D-F5ACDM-2 at 2 m. Rockwell's instruction: replace the 2 with 0M3, 1, 5 or 10.

So the trailing number on an 889 cordset is the length in metres. The same convention runs across the 889D, 889M and 888M ranges.

A cordset out on a machine takes abuse that the device does not. On a switch behaving intermittently, the cable is worth checking first.

Safety I/O across the platforms

Two constraints on the ControlLogix safety modules, covered in more detail on the ControlLogix page: they require a Series C chassis, and the 1756-OBV8S must not be installed next to a controller or communication module.

Safety I/O also requires specific RTBs or IFMs. Both have been agency certified using ControlLogix RTBs, so substituting a generic wiring system can invalidate the certification.

Safety contactors

The 100S-C range is the safety version of the 100-C contactors covered on our contactors page.

Examples include 100S-C09EJ14BC, 100S-C43EJ14BC and 100S-C43QJ14BC.

The frame numbering matches the standard range, so a 100S-C09 is the 9 A frame. The S denotes mirrored and mechanically linked contacts, which is what makes feedback monitoring valid.

A standard 100-C is not a substitute for a 100S-C in a circuit that monitors contactor feedback.

Fail-safe controllers

GuardLogix is the safety version of ControlLogix, and Compact GuardLogix the safety version of CompactLogix.

A standard controller cannot substitute for one on a machine with a safety function, whatever the price difference.

Same principle as the Siemens fail-safe CPUs on our S7-300 CPU page.

Before ordering a replacement

Important: safety replacements

Safety components are certified as part of a machine's safety function, with a rated Category or Performance Level.

A like-for-like replacement of the same catalogue number preserves that assessment. A substitution may not. A relay with different input types, a different output count or different reset behaviour can change the achieved Performance Level even if it physically fits and appears to work. On guard locking, the locking principle and the access type are not interchangeable. On light curtains, resolution and protective field height are not interchangeable, because the mounting distance was calculated from them.

Our position is simple. We will supply the exact catalogue number you specify. If you ask us to suggest an alternative we will tell you what we believe is equivalent and what differs, but the decision on whether a substitution is valid for your safety function belongs to whoever is responsible for the machine's safety assessment. We are a parts supplier, not your safety engineer.

If the original is genuinely unobtainable, tell us and we will help you find it rather than pushing you toward a substitute.

What to send us

The full catalogue number off the device.

Which half you need. Switch, actuator, sender or receiver.

The locking principle, on a guard locking switch. Power to lock or power to release.

Whether the installation uses unique coded actuators.

Resolution and protective field height, on a light curtain.

What the device connects to. Safety relay, safety controller or safety I/O.

What we can supply

Current production. GSR safety relays, 440G guard locking across the LZ, MZ and MT families, 440K and 440N switches, GuardShield light curtains, 442L scanners, safety contactors, POINT Guard and FLEX 5000 safety I/O, actuators, cordsets and mounting hardware. Quoted with a delivered lead time.

Earlier and discontinued. MSR relays including the MSR127 family, TLS and Trojan switches, older interlocks and safety mats. Surplus and tested used.

The MSR side matters. A lot of New Zealand machinery built in the 2000s runs MSR relays, and when one fails the choice is a used original or a safety reassessment.

Actuators and cordsets separately. Usually the cheaper fix.

We buy Guardmaster

Safety relays and interlocks are worth real money to plants still running the same generation, because a like-for-like replacement avoids a reassessment.

Keep switches with their actuators, and light curtain senders with their receivers. Matched sets are worth considerably more than orphaned halves. See Sell To Us.

Related

Allen-Bradley overview, contactors and overloads for safety contactors, and FLEX and POINT I/O for safety I/O.

For safety from other brands see SICK, Pilz, Schneider Preventa, ABB Jokab, Leuze and Omron.

Send us your catalogue numbers

Tell us which half you need, and the locking principle on a guard locking switch. And if a switch went into fault after someone used the manual release, cycle the power first. Quotes in NZD including GST.

Request a quote

Industech is an independent supplier of new, surplus and used industrial automation equipment. We are not an authorised distributor of, approved by, sanctioned by, or affiliated with Rockwell Automation, Inc. Allen-Bradley, Guardmaster, GuardLogix, GuardShield, SensaGuard and Trojan are trademarks of Rockwell Automation. All trademarks, brand names and catalogue numbers are the property of their respective owners and are used here for identification purposes only. Information on this page is for identification and does not constitute a safety assessment.