Slew limiters: Everything you need to know

What is a slew limiter?

Slew limiters monitor the position of an excavator’s boom and dipper as they move from side-to-side, warning operators when they approach pre-set safety limits. This prevents collisions with nearby hazards such as barriers, signage and oncoming traffic, helping to protect everyone from the risks of excavator operations. For increased safety, advanced systems also feature motion cuts to restrict movement if limits are reached.


Why do I need a slew limiter?

You need a slew limiter if you want to use excavators safely next to live railways, highways, fixed hazards or the passing public. Major civils construction sites increasingly expect excavators to be equipped with an approved slew control system, particularly when working within central reservations. Using a slew limiter demonstrates that safety is a priority for your business, helping to open the door to new opportunities. 

Yet slew limiters are more than just a tick box. Minimising machine downtime while mitigating costly incidents, slew control protects your profits while offering a quick return on investment.

Select slew limiters also offer full-envelope control, which limits height, reach, slew and depth to maximise safety.


What can I install it on?

Slew limiters are designed to protect single, mono and triple boom excavators. There are also options available for backhoes, telehandlers and cranes.


What solution fits my operations?

To get the most out of your system, it’s important that you find the right slew limiter for your construction needs.

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Types of slew limit



Angular slew limiting

Angular slew limiters use two points that extend outwards at an angle from the centre of the machine. This determines the operator’s movement parameters, limiting slew if the set working area is exceeded.

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Virtual wall slew limiting

The most advanced slew limiters use virtual wall technology to deliver full-envelope controlThis expands the machine’s safe working zone when compared with angular systems. Perfect for working next to highways or railways, operators can easily set singular, dual-point and multi-point virtual walls to avoid multiple hazards in busy urban environments, improving productivity by minimising machine repositioning time.

Singular virtual walls

With singular virtual walls, operators can outline a more specific exclusion area than angular slew, giving operators more space to manoeuvre. This slew limiting type is an effective way to work safely next to live road networks.

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Twin virtual walls

Dual-point virtual walls are identical to singular virtual walls apart from they allow operators to set two exclusion areas. This protects operators working in narrow areas with hazards either side, such as central reservations.

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Multi-point virtual walls

Designed for the most confined working areas, multi-point virtual walls allow operators to plot complex exclusion zones that maximise space. Operators can then avoid multiple obstacles with ease when working in compact environments.

With our PME range, you can easily switch between any of these slew types using our simple, graphical display.

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Motion cuts

Although all slew limiters alert operators when pre-set limits are approached, some systems use hydraulic motion cuts to restrict machine movement when these are reached. Protecting against user error, motion cuts are recommended to ensure the highest levels of safety when operating excavators. 

To ensure that all operatives return home safely from work, every PME system features motion cuts as standard.

Complying with regulations

Slew limiting is required to get site access in various applications to ensure safe excavator operation. As excavator operations continue to move closer to the passing public, highways projects increasingly mandate the use of an approved slew limiter. Developed in JF Prolec’s UK production facility, our PME range undergoes extensive quality control to ensure that systems are fully compliant with the latest safety regulations.

For safety-critical rail projects, there are strict regulations in the UK and EU to protect road-rail vehicle (RRV) operations. Under these, all plant must be equipped with a slew limiter that has full-envelope control and RCL (Rated Capacity Limiter). Delivering reliable protection for any rail project – including any line open operations – PME Rail and Euro Rail are fully compliant with UKRIS1530 and Europe’s EN15746 standards.

Tail swing monitoring

Tail swing monitoring measures the position of the excavator’s chassis in real time to help prevent collisions with hazards behind operators. Designed for excavators with housing that extends beyond their tracks, this delivers increased safety when working in confined areas. Tail swing protection is available with all full-envelope control systems in our PME range.

Safe system use

Correct slew limiter use is key to safe excavator operations. Designed with this in mind, our PME range features a simple, icon-led display to deliver easy, hassle-free limit setting. Read our PME Quick Start Guide to learn more.

To maximise safety and productivity, we also recommend that operators are upskilled with accredited safety system training. 

Override key switch

In exceptional circumstances, slew limiters sometimes need to be overridden. All PME systems come with override key switches so that you can move machines freely in these situations. 

Managing access to limits

In certain cases, supervisors need to set safe working zones themselves. With our PME technology, supervisors and site managers can easily manage access to limits directly from the device.

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Explore our solutions for slew limiting