Issue 139 August - October 2020

Please note: The issue content below is just a summary of the articles in the printed magazine.
The articles are not available on-line. Please refer to the printed magazine for the complete article.
Connecting people to smart systems – for better real-time decision making

While New Zealand manufacturers are fighting to survive shutdowns and disruptions to their suppliers as well as their customers, the opportunity to increase productivity, efficiency and competitiveness during this disruption has never been greater.

This opportunity has arrived with the new wave of automation driven by the ease of connecting devices and machines on the plant floor across production and business management systems and the better-informed decisions that result from it.

The electrical industry has a key role to play in helping local organisations survive and compete in this challenging market, says country manager for NHP Electrical Engineering Products, Mike Heron.

He says the work NHP is doing with its partners to modernize industrial, large commercial and infrastructure facilities throughout New Zealand has confirmed there is real value in the connectivity at the core of all the talk today of IOT and Industry 4.0.

The new head of Rockwell Automation in New Zealand, Mike Greig, agrees. He says he is greatly encouraged by the number of companies that are investing in smarter connectivity as a means of improving their performance.

Installing machines under HSWA

While installing an electrically-driven industrial machine is fraught with legal risks, there are pathways to compliance that will seriously reduce these risks for electrical installers who take advantage of the protective measures provided in the law.

The last issue of ElectroLink identified two pathways that can be followed when installing a machine imported by an industrial company for its own use: treating the relevant parts of the machine as fittings and installing them to AS/NZS 3000, or treating the machine as an appliance and leaving the primary responsibility for the safety of the machine with the owner of it. (See 'Machine Installation', ElectroLink July issue, page 7)

The following article addresses the crossover from the Electricity Regulations to the Health and Safety in Employment Act (HSWA), where the liability facing electrical contractors installing machines carries over into HSWA.

Understanding how electrical law is set up (but not carried through into training prescriptions by ITOs) can be helpful to licensed engineers, electricians, and inspectors in this legislative crossover. It is particularly helpful in managing any future risks to the safety of machine operators for which installers can be held liable under health and safety law long after the installation is completed.

Test and tag fails the test of time

While a review of the standard for testing and tagging in-service electrical equipment is now underway, there is no sign of any government interest in addressing the misuse of this standard and the regulation that cites it.

This regulation, which calls up AS/NZS 3760, drew the ire of the previous government which used it to highlight the kind of regulatory creep that adds a lot to the cost of compliance but little to safety.

In 2015 the government’s Rules Reduction Taskforce described the requirement to test and tag electrical equipment as a “loopy” rule that was “out of date, inconsistent, petty, inefficient, pointless or onerous” and an example of where “inappropriate interpretation, over-zealous enforcement and lack of focus on the customer” needed to be fixed. (See ElectroLink, November issue 2015, page 14 ‘Trouble with testing and tagging’)

Five years later, the standard is being addressed but not the ‘loopy’ rule that cites it. It is up to the government to amend the Electricity Regulations that cite the application of AS/NZS 3760 and there appears to be no interest in doing that.

What does the earth peg do?

Electrical inspector Athol Gibson comments on earthing issues

The New Zealand MEN system of earthing is a variation of the international TN-C-S earthing arrangement. It has a history in New Zealand almost as long as electricity has been generated here.

For circuit fault protection to operate, Electricity Regulations require that an earthing arrangement be provided for all installations. This is accomplished in the MEN system by connecting the transformer star point to the general mass of earth at the transformer location. The network neutral is also connected to this earth connection. The installation earth bar is connected to the neutral bar by way of the MEN link and any installation fault current returns to the supply point through the network distribution neutral. The installation earth bar is ‘earthed’ by connection to the earth electrode through the main earthing conductor. The network distribution neutral may also be earthed at additional locations in the network.

Motion safety - safety that is non binary

The integration of electrical safety systems into machinery has unquestionably made workplaces safer. This is due to the ability of safety systems to detect potentially hazardous situations and reliably shut off machinery, thus protecting workers. Methodologies to help achieve this reliable safety can be found in a range of international standards.

Programmable safety controllers, utilising functional safety (as per IEC 61508), have traditionally used digital I/O exclusively, which only allows strict binary states. This is appropriate for many applications as safety conditions are often binary – a gate, for example, can be either closed or not closed, nothing else.

The input devices and logic within the controller’s program are purely binary, as are the digital outputs used to control machinery. A safety trip, such as the activation of an emergency stop switch, effects an immediate return to the safe state, where all outputs are turned off.

Once stopped, a reset operation (which is usually initiated by a reset switch) is needed to restart the machinery. (Part of the reset routine is to check if it is safe to restart i.e. the cause of the trip has been resolved).

Time of flight sensors – a new way of detecting objects

The ability to detect the presence of moving workpieces is one of the most common tasks in industrial processes. It’s vital that it be done quickly and, most importantly, reliably. Failure to detect the presence of a workpiece or a false trigger (when the workpiece is not present) can cause potentially serious disruptions to workflow, which will adversely affect productivity.

Two common methods of detecting workpieces are by contact (eg: an actuator arm of a limit switch) or contactless, such as a beam of light (photoelectric sensor) or electromagnetic field (proximity switch). Contactless methods are generally preferred as they are faster and not subject to wear and tear.

While presence detection may seem simple, in practice many applications need to sense workpieces of diverse shapes, made from differing materials, at varying distances, and all with high reliability. This article seeks to explain how current methods solve certain applications and how the improvements offered by the latest sensing technologies open new opportunities.

Healthcare lighting update

If you are designing lighting for healthcare premises new guidance is available to help light the facility to a world standard.

Produced by the Society of Light and Lighting (SSL), the release last year of LG2 2019 provides lighting engineers and architects updated guidelines which allow more scope to humanise spaces not required for clinical purposes. To help lighting professionals keep up to date and maintain best practice, the LG2 updates were presented to users in a recent webinar.

There is a new emphasis on lighting for community care facilities in the new guidance as well as improved guidelines for architectural areas. The document also includes updates on hospital emergency lighting, helipad lighting and other specialised areas.

Lighting for indoor farming

Animals are similar to humans in that a combination of daylight factors work together to influence their physiology in ways that are not yet fully known. But what is known is that light does effect farm animals and that can have a bearing on their productivity. Good lighting design can improve this.

Daylight factors to consider include the duration of light exposure, colour temperature, spectral distribution, intensity and angle of incidence.

When animals are kept in indoors for some or all of their lives, they might be reliant on artificial lighting to replicate some or all of the effects of daylight.