How to Choose the Right Case for Rack Mount Equipment

There are two predominate styles of shipping and transit cases.  Cases with foam interiors and cases that are designed for the mounting and operation of 19” rack mount equipment.  Rack mount cases are used for applications that include servers, mass memory storage, test instrumentation, satellite broadcast equipment, radar equipment, C4 (command control communications and computers) equipment and educational and research equipment, and musical road equipment.

 A rack case allows for items that are typically installed on a fixed rack to be safely transported, and when needed in the field, operated in the case with limited additional set up.  A rack case can be designed for use in indoors, in a shelter, or in on-road vehicles. Rack cases can be designed for damage-free shipment via military modes, including wheeled or tracked vehicles, aircraft and sea vessels.  Some styles of rack cases can be stored and used in the most severe weather conditions. 

Rack mountable equipment standards have been set by the Electronics Industries Alliance (EIA) – now controlled by the Electronic Components Industry Association (ECA). These standards ensure that any rack mountable unit will fit into a rack mount case. Rack mountable equipment has a front faceplate with vertical holes on the front left and right sides.  EIA set the width from the left set of vertical holes to the right set of vertical holes at 19”. They then set the vertical dimensions of holes in 1-3/4” increments - by what they termed as a “Rack Unit” or “U”. The rack mount case has a pattern of holes in the metal posts (or uprights) that the front face plate is mounted to consistent with the 1-3/4” pattern. This simplifies the process when picking a case. As an example – A rackmountable piece of equipment that is 7” in height will require a 4U case. Multiple units can be packaged in the same case simply by adding up the totals Us for all the equipment. For shock protected racks (explained later) – the weights of the unit(s) will be needed so the case specialist can pick the correct set of shock mounts to properly protect the equipment if the case is subjected to drops or vibrations.

Rack mount cases are available in several materials and are manufactured with various processes.  What they have in common is the metal frame inside that replaces a static rack for transport.  All of the equipment is mounted onto the rack so that it will remain stable during transport.

Fabricated cases are usually a wooden plywood case with a covering over the plywood.  They can also be made of a laminated plastic material.  The walls are constructed  using aluminum valances and corners with the wall material  riveted in  aluminum grooves.  The outside covering of the case typically is ABS plastic, aluminum or even carpeting covered plywood. Fabricated rack cases can be made in unlimited combinations of rack height and depth. 

Plastic rotationally (or roto-) molded cases are made using plastic pellets that are ground down to powder.   The powder is poured into a mold and placed in an oven.   While the mold is in the oven it is constantly turning. Once completed the case corners will be 15% thicker than the walls because of the constant rotational movement. These cases have molded in ribs to give strength and to recess handles and latches.  Roto-molded cases are available in a number of standard sizes and configurations.

Vacuum-formed plastic cases start with sheets of plastic formed over a mold that, when heated, conform to the shape of the mold.   Once the mold is completed, an aluminum valance is formed around edges of the case.  This valance is used to keep the structure of the case. The rack is attached to the case walls or is integral to the valance. 

Aluminum cases can either be a fabricated aluminum similar to the fabricated plywood case or formed similar to the vacuum-formed cases using sheets of aluminum heated and pressed over a mold to form a shape. Formed aluminum cases are often seam-welded for environmental and EMI (Electro-Magnetic Interference) sheilding.

Rack equipment mounted on railsIf the equipment is already ruggedized and/or transported by vehicle, and stays with in your control, a hard mounted case may be chosen.   A hard mounted case offers limited impact protection with a low profile, and is lightweight so it is easily maneuverable.    This case would have two EIA rails mounted to the inside walls in the front and often the rear of the case.  Equipment will attach directly to these rails.

If the equipment needs protection from shock and vibration a Shock -mounted case should be selected.

These cases have the ability to protect from 15 to 120Gs with a standard case configuration.

Rack mount case with removable lidsTypically a rack mount style of case will have two removable lids (front and rear).   This is done for easy access to your equipment.    Shock protection can be in different varieties depending on what style case you may use. 

A fabricated case would have an inner box built inside the outer box with a layer of foam in between.  The foam is used as the shock absorber.    

A plastic roto-molded/vacuum formed or aluminum case will have  an EIA rack mount frame  fixed in the case with a shock isolators connecting the frame to the inner wall of the case.

Typically on this style case eight rubber isolators would be used for the shock protection.  The shocks come in different tension increments depending on the weight load of the equipment packaged in the case.    Another form of a shock mount is a wire isolator.    These would be used in an extreme application that requiring a low G rating.    See photos below:

 rubber isolator

Picture of installed rubber isolator

 wire isolater

Wire isolator used for shock mounting items

 

Rack mounted cases are capable of accepting a large number of optional items to ease the use and handling of the case in the field. The 19” rack may be removable from the case for equipment servicing or use.   The cases can be outfit with casters that range in size from 3.5” to 8” chosen based travel surface.  The cases can be configured with storage options including pouches and locking drawers.  Rack cases have many of the options used in data room racks including fixed and sliding shelves, power strips, horizontal equipment supports and cooling fans.  For cases that are utilized in harsh environments, the rack mount case can configured as airtight and waterproof, and it can include air-conditioners. Rack mount cases can be configured to be self-contained operating systems when outfit with table legs to elevate the case off the ground and chair kits that allow the user to sit in front of the case.   

When you work with a packaging specialist you will receive the benefit of his experience, technical knowledge, and design expertise.  The specialist will provide the most cost effective and technically sound shipping case interior protective solution regardless of the type of case or container that you select.