Metal bar grating can be defined as a series of metal bars positioned vertically, placed an equal distance apart and joined by cross members to form a rectangular or reticuline pattern. Typically manufactured from mild carbon steel, 6000 series aluminum and 300 series stainless steels, bar gratings are also available in specialty metal alloys to suit nearly any application.
The vertically positioned bars are designated as the bearing bars. These bars range in size from 3/4" x 1/8" for light pedestrian traffic to 7" x 1/2" for extreme vehicular loads. Typically, the spacing of the bearing bars is indicated in sixteenths of an inch, measured from the center of one bar to the center of the adjacent bar. This center to center or on center spacing ranges from 7/16" to 19/16" (1-3/16") on standard grating products. Standard gratings are also available with wider spacings providing an even greater open area, but should not be specified without consulting the manufacturer. Heavy Duty grating products are commonly manufactured with bearing bar spacings ranging from 15/16" to 38/16" (2-3/8") on center.
The bars used to secure the position of the bearing bars are commonly designated as the cross bars. Crossbar profiles vary according to the method of assembly and material selected. As with bearing bars, cross bar spacing is measured as on center spacing. The customary cross bar spacing is 4" on center. On special order, 2" on center and other special spacings are also available.
Proper specification of bar gratings includes a determination of load conditions, effective unsupported clear span, flooring surface, trim and finish. Appropriate consideration of these elements plus any features unique to their particular application will allow the specifying authority to select products that will provide years of continuous service.
SPAN – In grating nomenclature, span serves a dual role in defining two significant features. First, unsupported span indicates the clear distance between effective points of support for the grating. Once the specifier has established the design load and acceptable deflection criteria, grating selection will be dictated by determining the maximum unsupported span and consulting the load tables on the pages that follow. Secondly, span indicates the overall finished length of the grating panels (parallel to the bearing bars) as they are supplied to the customer.
WIDTH – The overall dimension of the grating panel measured perpendicular to the bearing bar span is designated as the panel width. Commonly manufactured and stocked in 24" and 36" nominal widths, grating panels can easily be supplied in a variety of widths to suit the needs of any application. For non-stock widths, consult the Panel Width Chart on page 17 of this catalog. Additionally, custom widths can be shop fabricated to hold any specific tolerance.
SERRATED SURFACE– The excellent drainage and self-cleaning characteristics of plain surface grating make it suitable for the majority of applications. In the presence of materials which could cause the top surface of the bars to become slippery, the optional serrated surface should be considered. When serrated surfaces are specified, the bearing bar depth must be increased 1/4" greater than the sizes shown in the load tables and selection guides to provide the equivalent strength of non-serrated bars.
BANDING – To enhance the architectural appearance or to provide additional transverse stiffness, the open ends of the grating panels can be banded. This is achieved by welding a flatbar, similar in size to the bearing bars, to the cut ends of the grating panel. Banding can reduce impact stresses by transferring loads to adjacent bars that are not directly subjected to service loads. Trim banding should always be considered when the grating panels are designed to be removable on even an infrequent basis. Additionally, banding should always be specified when the ends of the bearing bars are unsupported or the grating is designed to service vehicular loads. Further banding descriptions and welding standards can be found on page 17 of this catalog.
FINISHES – Steel grating products are usually shipped with one of three standard finishes, bare steel, painted with one coat of the manufacturers red or black paint, or hot dip galvanized after fabrication in accordance with ASTM Standard A-123. Aluminum products are commonly supplied as mill finished, but are also available with optional anodized finishes. Stainless steel products as produced typically require secondary finishing such as chemical cleaning, abrasive blasting or electro-polishing. All of our grating products can additionally be supplied with special custom finishes such as enamel or epoxy coatings. When considering such finishes, careful evaluation of the specified material and consultation with the coating manufacturer is essential.
Steel Bar Grating Load Table
Swaged Aluminum Grating
Pressure Locked Grating
Indiana Gratings offers two distinct types if Pressure Locked Gratings which are identified by their method of assembly. Manufactured without the introduction of heat or riveting, these gratings provide a finished product with attractive architectural lines. This pleasing appearance makes pressure Locked gratings ideal candidates for architectural and ornamental applications, such as grilles, screens, and fences. Additionally, pressure locked methods of manufacturing allow for the production of close mesh gratings with minimal open area. pressure Locked gratings with bearing bars spaced at 11/16" and 7/16" on center conform with the rigid spacing requirements of the Americans with Disabilities Act (ADA). These products are commonly installed at the entrance to public buildings where concerns of pedestrian traffic and high heeled shoes coincide with needs for ventilation and drainage.
Swaged Pressure Locked Gratings
Pressure Locked Gratings manufactured by swaging are designated by the profile "SG." These products are assembled by inserting hollow tube cross bars into pre-punched holes in the bearing bars and then swaging the cross bars (similar to the aluminum gratings found on page 4). This permanently locks the entire cross bar/bearing bar intersection within the interior of the bearing bar.
Dovetail Pressure Locked Grating
Pressure Locked Gratings manufactured with deep rectangular cross bars are identified as dovetail pressure locked and are designated by the profile "DT." These products are assembled by pre-punching both the bearing bars and cross bars, aligning the bars in an egg-crate manner, and deforming the cross bar into the dovetail slot in the bearing bar under intense hydraulic pressure.
Commonly produced in ASTM A-1011 mild carbon steel, 6000 series aluminum and 300 series stainless steels, Pressure Locked Gratings can also be manufactured in select specialty alloys. For assistance in selecting appropriate specialty alloys, please contact our sales department.
All Indiana Gratings Pressure Locked Gratings are fabricated to size on a "per order" basis. To enhance longevity, all products are manufactured with each outside cross bar/bearing bar intersection fillet welded in accordance with NAAMM standards. Banding provides additional transverse stiffness and it is highly recommended that all Pressure Locked Gratings be specified with all cutouts and open ends banded (see banding definition on page 3).
Custom Bearing Bar Spacing
The Dovetail Pressure Locked method of manufacturing is particularly flexible in that it allows for the production of gratings with custom bearing bar spacings. Small quantities can easily be manufactured to suit the precise needs of most applications. To specify non-standard spacings, simply insert the desired bearing bar center to center spacing (in sixteenths of one inch) in lieu of the standard spacings shown in the table above (note that 4" and 2" cross bars centers should be maintained).
Bearing Bar Selection & Load Tables
The bearing bar sizes offered for pressure locked gratings are common to those in welded steel, swaged aluminum and stainless steel gratings. In that the sizes and spacings of the bearing bars are consistent with these products, the load tables are similarly interchangeable.
Riveted gratings, which provided the foundation for the manufacture of commercial grating products, continue to serve many of industrys' most demanding applications. Manufactured by riveting crimped flat bar cross members to rectangular bearing bars in a reticuline pattern, these products offer superior resistance to impact, fatigue and repetitive loads. The truss-style reticulated cross bars offer excellent strength and durability when subjected to the concentrated stresses of rolling loads imposed by cart and dolley traffic.
Materials & Specifications
Riveted gratings are produced in carbon steel, 6000 series aluminum and 300 series stainless steels. To specify Riveted Grating, first, specify the type of grating from the table. In the instance of Standard Riveted Grating, The "18" indicates the method of the assembly shall be riveted construction, the "18" indicates that the bearing bars shall be spaced 18/16's (1-1/8) inches apart, and the "7" indicates that the rivets shall be spaced at 7" on center. Following selection of the type of grating, consult the load tables to select the appropriate bearing bar size for the loads and spans to be served. To complete the specification, indicate which of the three materials is desired for the application, carbon steel, aluminum or stainless steel.
When the walking surface of bar gratings are subject to the accumulation of moisture or other slippery substances, the optional serrated surface should be considered. Unlike rectangular mesh gratings where the bearing bars are typically constructed with the serrated surface, the standard method of manufacture for riveted gratings is to serrate the crimped cross member. When the grating is assembled, these crimp bars are allowed to project slightly above the top surface of the bearing bars to provide a superior unidirectional skid resistant surface. Environments particularly prone to unsafe walking conditions can be further specified as 100% serrated where both the bearing bars and the crimp bars are provided with serrations.
Riveted Grating Loading Table