High-density Mobile Storage Systems (Compactors)

Mobile systems, or compactors, consist of shelving, drawers, cabinets, or racks mounted on wheeled carriages that run on tracks and compact together to eliminate unnecessary aisles. Only one “movable” aisle is necessary for each range of mobile carriages. This allows twice as much material or more to be stored in the same amount of floor space needed with conventional fixed shelving.

• Mobile storage carriages
• Mobile storage units
  
  
  

Considerations

• Size
  Systems can range from small manual units less than 5ft long to an electrically-powered carriage hundreds of feet in length.
• Location
  They can be located almost anywhere from the basement to the roof, depending on the floor loading capacity of the building.
• Modes of operation
  Manual, for small or lightly loaded systems, with carriages up to 16ft maximum; mechanical assist (crank drive) for carriages up to 45ft (Fig. 1); and electric, for heavily loaded or extra-long systems, with up to virtually any length carriages. Electrically-operated carriages should have DC electric motor drives and controls to provide smooth, even acceleration and deceleration to avoid jarring the specimens.
  
  
  
  Figure 1. Manually operated mobile storage system.
  
  
• Guidance systems
  Mechanical details to be considered include wheels, guidance systems and rails. As a general rule, larger wheels provide smoother system operation. Systems with monorail-type roller guidance bearings that grip the rails on both sides are far less likely to bind or rack than systems with flanged wheels and grooved rails.
• Floor Loading
  It is important to have structural steel rails capable of transferring load from the floor slab to the building frame. Where floor loading may be a concern, a structural engineer should be consulted to determine the size of rail required, and where the rails should be placed with respect to the building frame.
• Anti-tip Devices
  These should be specified for tall systems or in any geographic area subject to seismic risk. (The state of California has established standards, initially for hospitals, that are widely used by museums and libraries too.)
• End Panels
  Laminate end panels are usually furnished as standard equipment, but a wide variety of materials and finishes can be specified. This is an individual matter of style and preference, but the potential for outgasing must be considered. The end panels also provide functional utility in that identification of contents through numbers, letters or symbols can be incorporated in the design and the flat surfaces can be used to display educational or instructional material.
• Paint Finish
  Leading case manufacturers have for the most part switched from spray enamel to powder coat finishes, that do not emit volatile solvents. Where out-gasing is a concern, powder coat finishes should be considered. Abrasion resistance can be a factor.
• Security and Protection
  • Where access must be controlled, mobile systems can be locked a variety of ways with waist high or floor level locks. Individual aisles or modules can be separately keyed.
  • Halon, sprinklers, or other fire protection can be built into a mobile system.
  • For dust protection, seals or gaskets can be furnished inside the face panels and along the top edges of shelving.
• System Layout
  There are many ways a mobile system can be laid out, for example, lengthwise in a room with a fewer number of long carriages or crosswise with a greater number of short carriages (Fig. 2).
  
  
  
  Figure 2. Example of mobile storage layout. Aerial view. 
  
  Often the choice is dictated by the number of people who may access the system at one time as well as building obstructions such as columns. The space planner usually starts by determining how high the system can go, which in turn determines how many feet of carriage are required to provide the necessary storage volume. The system is then divided into modules according to the number of people who will access it. Each module consists of a group of carriages and one moveable access aisle. Depending on the level of activity, one module can serve one, two, or sometimes three people. Modules are created by locating a stationary unit as a divider and leaving enough space on each side for a moveable access aisle. Sections are often divided at column locations with stationary units used to fill in the space between columns.
• Housings
  Although mobile systems are most commonly used with standard 4-post shelving, they will accommodate almost any kind of storage housing (some carriage designs are more flexible than others). The housing usually sits on top of the carriage, secured by a retaining lip. Where there may be height limitations, recessed carriages are available to mount the carriage a few inches closer to the floor. This may be enough to accommodate an extra tier of shelves (Fig. 3).
  
  
  Figure 3. top left, Fluid collection storage on open metal shelving with steel lips and vial storage in old museum                drawers mounted on aluminum racks. Note bungee cords which hold drawers in place during seismic 
                 activity. The bottom shelf is designed to carry the weight of stainless steel tanks.
                 
                 top right, Existing storage cabinets are stacked 3 high, back to back on recessed, mobile carriages.                 Drawers are coated and thickly lined with pH neutral blotters.
                 
                 bottom left, Entomology storage in glass covered trays in cabinets with lockable doors as above. 
                 
                 bottom right, Cabinets are designed with lockable doors that are tightly sealed. Interior sides of the                 cabinets are fitted with slots for drawers and trays, plus a pull-out reference shelf.
  
  
  

Mobile storage systems save space, associated energy and maintenance costs. They also enhance efficiency by consolidating storage. This consolidation can provide better control and tighter security where needed. Locking units can prevent unauthorized access.

At a minimum, safety and control options should include an infrared sensing system or a passive safety floor and ramp which deactivates the system and prevents carriage movement when an aisle is entered.

A photoelectric or mechanical safety sweep that extends the length of the carriage stops movement on contact with a person or object in the aisle. Photoelectric aisle-entry sensors detect a foreign object (such as an arm) protruding into an open aisle. Safety tapes on shelf edges are available to stop movement upon contact.