Electrical Systems

Three considerations for selecting the right enclosure

Choosing the right enclosure goes beyond the basic design; users also need to consider value, design flexibility, and modifications to the plant floor.
By Steve Sullivan July 3, 2019
Users need to consider value, design flexibility, and potential modifications when choosing an enclosure for a manufacturing application. Courtesy: Rittal

The enclosure is the foundation of a machine or other plant-floor or facility system, but it is often the last consideration in building the spec and deciding on the purchase budget. Enclosures serve two basic functions: it is a mounting space to place controls, switchgear and protective devices; the other function is environmental and contact protection.

When it comes to freestanding enclosure design, there are two basic options: modular and unibody. Both provide mounting surfaces, doors for pushbuttons or human-machine interfaces (HMIs), and sidewalls for climate control. They also provide mounting surface as well as contact and hazard protection.

Modular enclosures are typically frame-based systems. The frame delivers the strength to support the enclosure and all its components. Exterior panels, including the roof, sidewalls and doors provide load-bearing capabilities and environmental protection.

Unibody enclosures use a thicker gauge steel welded into a box shape. They also include a door configuration with lift-off or welded hinges. The walls are welded together to provide support for the unit and the mounted controls.

Beyond the enclosure’s construction, different considerations apply for each application. Three of the most important are:

  • Value
  • Design flexibility
  • Ongoing modifications.

1. Understanding value

What is value? There’s a formula that highlights the purchase price of an enclosure plus the use costs equals the total cost of ownership (TCO). Other models may put in operating costs, which would cover maintenance and downtime. The big question is: What value does the enclosure deliver over time versus the initial purchase price?

Value is the opposite of waste. Waste is the hidden costs users may not consider in the purchase price. This includes mounting panel preparation, grinding off paint to ensure proper ground, and tooling replacement costs from working with thicker steel. All of these add to the total cost.

Let’s think about human nature. What do employees do when they shut an enclosure? Is it a quarter turn of the wrist or is it multiple locking mechanisms that take a lot of time? Most people don’t even fasten those down. If it’s a clamp lever cover box, users may clamp the top ones and leave the bottom ones open. This negates the NEMA rating; the protection they’ve paid for is failing and placing equipment and people at risk of harm.

While it’s in our DNA to find the quickest and easiest way to get things done, this is where design needs to save people from their tendencies. For instance, a quick turn lock with foamed-in-place gaskets could completely seal and lock a door to the proper protection level.

If we look at the formula again, we see value is dimensional based on time, labor, protection and other factors not part of the initial equation.

When looking at enclosure value, it’s also important to consider efficiency because maintenance time equals cost. Common actions such as removing a door, sliding out a mounting panel or working inside the enclosure take time. Interchangeability and consistency of installed accessories helps lower use costs. If maintenance doesn’t have to include multiple employees, forklifts, hoists and cranes it’s easier and more cost effective. All of these factors change the initial purchase equation.

2. Design flexibility

Design flexibility is another consideration. Enclosures should have the flexibility in height, width and depth. A frame-based system has the ability to be reconfigured without significant modification. Side panels can be removed, doors reversed or legs added. If this can be done on-site easier and faster than other types of enclosures, time and money can be saved.

Users need to consider value, design flexibility, and potential modifications when choosing an enclosure for a manufacturing application. Courtesy: Rittal

Users need to consider value, design flexibility, and potential modifications when choosing an enclosure for a manufacturing application. Courtesy: Rittal

Flexibility is particularly important as Ethernet and information technology (IT) gear is moved to the plant floor to support edge computing and Industrie 4.0. The Big Data now part of manufacturing will need shared space. Does the enclosure design allow for the addition of that type of equipment? Control systems may be joined with more routers, remote monitoring and different types of climate controls. The enclosure must be able to handle half mounting panels and 19-in. racks for IT equipment. This may differ considerably from the initial consideration. If users can do it without an additional enclosure, there are significant savings in floor space and budget.

3. Modifications

It’s important to consider modifications and cutouts when looking at enclosures. If users are going to create holes for pushbuttons or HMIs, add climate control to the roof, or add cable entry, then the difference between unibody and modular stand out.

When working with a unibody enclosure, users are often either laying it down or climbing a ladder to make modifications. Where do the shavings go once users start cutting? Into the enclosure. Additional time is required for cleaning and inspection to ensure the shavings and debris don’t create problems with electronics on the panel.

With modular enclosures, users simply remove any of the panels that need to be modified, including the roof, door or sidewalls. Cutting, hole punching and mounting can be done in the workshop to keep debris and cleanup away from the enclosure and electronics. This improves safety, efficiency and protection for the components and the employees.

Reducing downtime, improving efficiency and delivering value over time are key considerations when selecting an enclosure. When considering enclosures for an application, it’s also important to consider flexibility, future-proof design and ongoing maintenance in the purchase equation. These affect the use costs over the life of the enclosure and the control systems and other devices it is protecting. Enclosures need to evolve with operations; the right choice will protect equipment and the bottom line.

Steve Sullivan is training supervisor, Rittal North America LLC. Edited by Chris Vavra, production editor, Control Engineering, CFE Media, cvavra@cfemedia.com.

MORE ANSWERS

Keywords: Enclosures, maintenance

Modular and unibody enclosures provide the same service, but they have different requirements and considerations.

Apart from enclosure type, users also need to factor in potential value, design flexibility and modifications.

Choosing the right enclosure for an application will protect equipment and the bottom line.

Consider this

Which of the three considerations highlighted in this article most influences your enclosure specification?


Steve Sullivan
Author Bio: Steve Sullivan is training supervisor for Rittal North America LLC.