From The Ground Up

Order picker or catwalk? Every records center owner likely has contemplated this question at some time in his or her company’s history. Both systems offer advantages and drawbacks, and the option selected will affect a records center’s operations going forward.

REB Storage Systems International, based in Chicago, has specialized in the design, manufacture, distribution and installation of records storage systems since 1962. The company offers a diverse array of shelving designs to match the diversity seen in modern records centers, which range from underground vaults to tall warehouses, with the goal of optimizing cubic capacity at the lowest cost per stored box. The company’s President Tom Lesko and Executive Vice President Lori Palmer answer questions on the evolution of racking and the advantages associated with catwalk and order picker systems for SDB magazine.

SDB: What are the most prominent trends in racking system design? How have racking systems changed during the last 15 years?

REB: Steel shelving was initially used with solid steel shelves, cross bracing and closed back or end panels, and cartons were stored three wide by one or two deep by one or two high per shelf. Heights were limited to 24 feet.

Boltless rivet shelving was the next type, still used today in shorter type systems. Rivet type shelving has steel posts, steel shelf supports and particle board or wire type decking. Cartons are most commonly stored five wide by two or three deep by two high per shelf. Heights are limited to 15 feet to 18 feet.

Heavy-duty records storage racks are the most common type used to date. They can be used in order picker or catwalk systems. Standard beams allow for eight or nine boxes wide by three or four boxes deep by three boxes high and are able to accommodate many types of decking, such as solid steel corrugated decking, wood decking or 50 percent or greater open style decking, such as Snap Shelf, Punch Deck or wire decking. In most cases [the style of decking] will depend on local fire code regulations and the type of sprinkler system at the ceiling. Heights can be erected to 70 feet.

Order picker systems can offer reduced lighting, sprinkler and ongoing labor costs, while catwalk systems can offer greater capacity and less in the way of additional equipment investment.

SDB: What are the primary factors a company should consider when choosing between catwalk and order-picker systems for a records storage center?

REB: Typically an order picker system will require wider service aisles and wide turn-around aisles for the equipment. This will require greater floor space and, therefore, lower carton capacity in the building. The result is reduced annual storage and retrieval revenues.

In a single-level order picker system, each person accessing the system will need some kind of equipment (rolling ladder, scissors lift, order picker, etc.). This will limit the number of workers who can work within the system at any point in time. A catwalk system can have an unlimited number of personnel working at the ground and at each catwalk level.

Overhead sprinklers at the ceiling are usually necessary in both types of systems, depending on the ceiling height and storage height of the system. In-rack sprinklers may be necessary as well, depending on the overall height and type of ceiling sprinklers. Lighting and sprinklers are sometimes necessary in a catwalk system under each walkway level.

Either guiderail or a wire-guided system should be utilized in an order picker system to avoid damage to the floor-level cartons and racking. In addition barriers are recommended at row ends to minimize damage to the rack uprights.

SDB: What secondary factors influence the type of racking a company selects?

REB: Permitting, cost, space, sprinklers and lighting; method of storage for cartons (three high by two deep, three high by three deep, three high by four deep, etc.); local jurisdiction issues; floor load capacity of concrete and subsoil.

SDB: What are the drawbacks and benefits associated with order-picker systems?

REB: The benefits include:
• Reduced lighting cost (especially if order pickers are equipped with head lights);
• Reduced sprinkler system costs;
• Time required for permitting typically is less than the time required to permit a catwalk system;
• Large transfers of cartons can usually be effected in a shorter time frame vs. a catwalk system; and
• Reduced ongoing labor costs.

The drawbacks include:
• Less capacity typically than a catwalk system, especially in a tall building;
• The cost of vehicles and battery chargers;
• The cost of guide rail, buried cables and column protection barriers;
• Maintenance;
• Limited to one operator;
• Downtime for the order picking vehicle; and
• The price of the order picker can get very expensive in heights greater than 30 feet.

SDB: What are the drawbacks and benefits associated with catwalk systems?

REB: The benefits include:
• Greater carton capacity, resulting in maximum building revenue, year after year;
• Minimal additional equipment needed other than carts and rolling ladders; and
• Order picking is not restricted to one or two individuals.

The drawbacks include:
• In-rack sprinklers may be required below catwalks;
• Lighting may be desirable below every-other catwalk level;
• Large one-time moves of cartons into the records center may take longer [relative to an order picker system];
• The cost of catwalk and stairways; and
• Vertical pallet lifts may be needed in taller systems.
 

Records centers often feature aisles from 32 inches to 36 inches in width.

SDB: Is there an optimal aisle width that offers versatility with minimal waste?

REB: Maintaining code and functionality need to be considered. In most cases 28 inches is the minimal code requirement, but that narrow width makes it almost impossible to function. Thirty inches is usually the minimum clear aisle width, and 32 inches to 36 inches are most common. Box overhang should be considered when determining the clear width between cartons.

Burying the building columns is extremely important in the design of a system. This allows travel through the aisles without interference and allows you to still store cartons around the building column that is buried in the racking.
 

SDB: What advice do you have for companies who are currently in the market for racking?

REB: Work with a storage system provider who specializes in records storage. Records storage design is not the same as warehouse storage; it is not just upright frames and beams. A company that specializes in the design of records storage facilities knows the industry and what is needed to achieve maximum profitability.

Let the storage system provider design the overall system in advance. That way you have a plan. You will know what your building capacity will be even though you will be purchasing the overall system in phases. This helps you plan accurate aisles, burying of building columns, cost per box and lighting and sprinkler design. It also allows you to design the system based upon what is required by the industry or local fire codes and regulations. Most importantly, it will provide you with excellent projections of revenue and the long-term profitability within your facility.

Lori Palmer of REB Storage Systems International can be contacted via e-mail at lpalmer@rebsteel.com. The company’s website can be accessed at www.rebsteel.com.

Also check out our Web Extra article, "Operator Error".