Tony Hague, managing director of PP Electrical Systems, explains why the right interconnectivity has never been so important for machinery builders – especially those exporting to North America.
Almost every machine builder gives considerable thought when designing a control system for a piece of equipment.
Time is invested in looking at panel design so that cost and performance can be optimised, sophisticated CAD software can quickly generate layouts and wiring schedules and 3D software can consider mechanical constraints and assist in the overall design and integration.
However, often the amount of time invested in looking at the overall machine interconnectivity is considerably less and firms could be missing out on significant opportunities, or worse, not complying with certain standards for markets such as North America.
When considering interconnectivity design, we can broadly split it into two areas:
- Technology & Process Quality
- Standards & Compliance
Technology & Process Quality
Over recent years we have seen the growth and development of ‘bus systems’ that are now offered by many different technology providers.
Networks are now far more flexible and ‘open’ and such systems allow us to replace traditional multi-core cables and connectors with remote I/O and ‘plug in’ style M8/M12 connectivity.
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The benefits to the customer are multiple and include speed of wiring/install, significant reductions in the number of cables trailing around a machine and the use of propriety, tested cables and modules that can be quickly and easily interchanged or expanded.
Talk to any machine builder and they will always confirm that the single biggest contributor to machine downtime and field failure is caused by poor ‘connectivity’.
This is hardly surprising when you consider the sheer volume of electrical connections in and around a piece of complex machinery, coupled with the often demanding environments that machinery is operating in – lots of vibration, water ingress and mechanical strain.
However, steps can be taken to optimise the quality and reliability of such connections, including:
- Automation of cable crimping – for example, PP Electrical Systems uses equipment that incorporates crimp force monitoring technology, which allows 100% in-line process quality checking of every crimp being put onto a given cable.
- Use of Spring Clamp technology – can often provide significant benefits over screw clamp technology, providing constant tension and offering resistance against vibration.
- Use of Torque Tools – where screw clamps are used, it is essential to ‘torque’ up connections in line with manufacturers’ recommendations. The errors of a ‘loose’ connection are obvious, but equally the potential impact of ‘over-tightening’ a screw connection is equally damaging.
- There is nothing more difficult for a service engineer to find than an intermittent fault caused by a faulty connection, when a machine is down and the customer is losing production time.
Standards and Compliance for North America
More machine builders are beginning to exploit the sales opportunities presented by the growing market in North America. They may well be aware of the associated UL508a standard that is relevant to the electrical control panel, which is of course vitally important.
Often, however, they are not aware of the equal importance of the National Fire Protection Association standards that are relevant to the machine wiring.
The National Electrical Code (NEC) is written by the NFPA, a US trade association that creates and monitors standards and codes for use and adoption by local governments in connection with machine building and installation…this code is also known as NFPA70.
NFPA79 is a ‘standard’ for the electrical part of a given industrial machine and covers machines operating at 600V or less. The standard details permitted wiring types, wiring practices, as well as interconnectivity of components and safety etc.
What it covers:
- Operating conditions
- Protection from electric shock
- Control function
- Wiring Practice
Hence when we consider a typical machine, we would be evaluating such areas as control cables, field bus wiring, data cables and servo motor cables.
Machine builders also need to understand the key differences between:
- UL ‘listed’ cables
- UL ‘recognised’ cables
A ‘listed’ cable signifies it has been tested and approved for a specific use and meets the UL standards and requirements of NEC.
A ‘recognised’ cable signifies the product is rated as a ‘component’, being part of an application. Cables with ‘Appliance Wiring Material AWM std 758’ are always recognised.
The use of such cables will have certain limitations.
PP Electrical Systems works closely with its technical partners in order to provide complete control and automation solutions to machinery builders.
The benefits to the customer can result in:
- Reduced manufacturing costs
- Compliance to standards such as UL508a & NFPA79
- Reduced production times
- Improved quality and reliability, therefore reduced machine downtime.
- Reduced customer lead times
These are tailored to provide specific information around topics such as UL508a and NFPA compliance for machine builders.