October 2007
Process Industry Practices
Structural
PIP STE05530
Grating Design Guide
PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES
In an effort to minimize the cost of process industry facilities, this Practice has
been prepared from the technical requirements in the existing standards of major
industrial users, contractors, or standards organizations. By harmonizing these technical
requirements into a single set of Practices, administrative, application, and engineering
costs to both the purchaser and the manufacturer should be reduced. While this Practice
is expected to incorporate the majority of requirements of most users, individual
applications may involve requirements that will be appended to and take precedence
over this Practice. Determinations concerning fitness for purpose and particular matters
or application of the Practice to particular project or engineering situations should not
be made solely on information contained in these materials. The use of trade names
from time to time should not be viewed as an expression of preference but rather
recognized as normal usage in the trade. Other brands having the same specifications
are equally correct and may be substituted for those named. All Practices or guidelines
are intended to be consistent with applicable laws and regulations including OSHA
requirements. To the extent these Practices or guidelines should conflict with OSHA or
other applicable laws or regulations, such laws or regulations must be followed.
Consult an appropriate professional before applying or acting on any material
contained in or suggested by the Practice.
This Practice is subject to revision at any time.
© Process Industry Practices (PIP), Construction Industry Institute, The
University of Texas at Austin, 3925 West Braker Lane (R4500), Austin,
Texas 78759. PIP member companies and subscribers may copy this Practice
for their internal use. Changes, overlays, addenda, or modifications of any
kind are not permitted within any PIP Practice without the express written
authorization of PIP.
PRINTING HISTORY
October 2007 Issued
Not printed with State funds
October 2007
Process Industry Practices
Structural
PIP STE05530
Grating Design Guide
Table of Contents
1. Introduction................................. 2 5. Openings in Panels .................... 5
1.1 Purpose............................................ 2 5.1 Banding............................................ 5
1.2 Scope ............................................... 2 5.2 Dimensions ...................................... 5
5.3 Shop Versus Field Fabrication......... 6
2. References .................................. 2 5.4 Large Openings ............................... 6
2.1 Process Industry Practices .............. 2
2.2 Industry Codes and Standards ........ 2 6. Design Drawings ........................ 6
2.3 Government Regulations ................. 2 6.1 General ............................................ 6
6.2 Fastening ......................................... 6
3. Definitions ................................... 2 6.3 Support Plates ................................. 7
4. General Design ........................... 3 7. Shop Drawings Reviews............ 8
4.2 Design Loads ................................... 3 7.1 General ............................................ 8
4.3 Grating Thickness and Span ........... 3 7.2 Recommended Drawing Review
4.4 Bearing on Supporting Steel............ 3 Checklist .......................................... 8
Process Industry Practices Page 1 of 8
PIP STE05530
Grating Design Guide October 2007
1. Introduction
1.1 Purpose
This Practice provides guidance for the design of rectangular type welded steel
grating for fabrication in accordance with PIP STF05530, Grating Fabrication
Details.
1.2 Scope
This Practice describes the design of rectangular type welded grating and identifies
information required for grating shown on design drawings. This Practice provides
guidance for design of grating openings to accommodate penetrations for piping,
electrical, equipment, etc. A table showing safe loads and deflections for welded
steel grating is provided.
2. References
Applicable parts of the following Practices, industry codes and standards, and references shall
be considered an integral part of this Practice. The edition in effect on the date of contract
award shall be used, except as otherwise noted. Short titles will be used herein where
appropriate.
2.1 Process Industry Practices (PIP)
– PIP STC01015 - Structural Design Criteria
– PIP STF05530 - Grating Fabrication Details
– PIP STS05130 - Erection of Structural and Miscellaneous Steel Specification
2.2 Industry Codes and Standards
• American National Standards Institute (ANSI) / National Association of
Architectural Metal Manufacturers (NAAMM)
– ANSI/NAAM MBG 531 - Metal Bar Grating Manual
2.3 Government Regulations
The following government document has been used as a reference in the development
of this Practice.
• U.S. Occupational Safety and Health Administration (OSHA)
– Regulations 29 CFR 1910 Subpart D (Walking-Working Surfaces)
3. Definitions
fabricator: The party responsible for providing fabricated structural and miscellaneous steel
design drawings: Drawings produced by an engineer that show the work that is to be
performed. See Section 4.2 for information that should be included for the grating on the
design drawings.
Page 2 of 8 Process Industry Practices
PIP STE05530
October 2007 Grating Design Guide
shop drawings: Drawings produced by a fabricator that transfer the information from the
design drawings and other contract documents into accurate, detailed dimensional
information to be used for the fabrication of the grating and structural steel.
4. General Design
4.1 Grating should be designed in accordance with PIP STC01015 and this Practice.
4.2 Design Loads
4.2.1 Design loads should be determined from the intended function of each
platform, walkway, etc.
4.2.2 Loads from maintenance, storage, turnaround, exit requirements, vehicular
loads, and owner requirements should be considered.
4.2.3 As a minimum, loads should be in accordance with PIP STC01015.
4.3 Grating Thickness and Span
4.3.1 After the design load is determined, Table 1 should be used to determine
grating thickness and support beam spacing.
4.3.2 Table 1 is for plain (non-serrated) grating.
4.3.3 If serrated grating is to be specified, the required depth of serrated grating
should be 6 mm (¼ inch) greater than the grating thickness shown in Table 1.
4.3.4 The loads shown in Table 1 are allowable stress (unfactored) loads.
4.4 Bearing on Supporting Steel
4.4.1 Grating should have a 25-mm (1-inch) minimum bearing on supporting steel.
4.4.2 Special consideration should be given to the width of the intermediate
supports where the possibility exists for a break (joint) in the grating panel.
Typically, a channel is not sufficient for these cases.
Process Industry Practices Page 3 of 8
PIP STE05530
Grating Design Guide October 2007
Table 1 – SAFE LOADS AND DEFLECTIONS – WELDED STEEL GRATING (TYPE W-19)
(This table has been adapted from “Load Table for Steel Grating – Type W-19 in
ANSI/NAAM MBG 531)
U = Uniform load, psf
Du = Deflection due to uniform load, inches
C = Concentrated load at mid-span
Dc = Deflection due to the concentrated load, inches
MAX SPAN
SIZE/WEIGHT
SPAN 2'-0" 2'-6" 3'-0" 3'-6" 4'-0" 4'-6" 5'-0" 5'-6" 6'-0" 6'-6" 7'-0" 7'-6" 8'-0" 8'-6" 9'-0"
U 355 227 158 116 89 70
3/4" x1/8"
Du 0.099 0.155 0.223 0.304 0.397 0.503
3’-6”
4 psf C 355 284 237 203 178 158
Dc 0.079 0.124 0.179 0.243 0.318 0.402
3/4" x 3/16" U 533 341 237 174 133 105
Du 0.099 0.155 0.223 0.304 0.397 0.503
3’-10”
6 psf C 533 426 355 305 266 237
Dc 0.079 0.124 0.179 0.243 0.318 0.402
1" x 1/8" U 632 404 281 206 158 125 101 84 70
Du 0.074 0.116 0.168 0.228 0.298 0.377 0.466 0.563 0.670
4’-3”
6 psf C 632 505 421 361 316 281 253 230 211
Dc 0.060 0.093 0.134 0.182 0.238 0.302 0.372 0.451 0.536
1" x 3/16" U 947 606 421 309 237 187 152 125 105
Du 0.074 0.116 0.168 0.228 0.298 0.377 0.466 0.563 0.670
4’-9”
8 psf C 947 758 632 541 474 421 379 344 316
Dc 0.060 0.093 0.134 0.182 0.238 0.302 0.372 0.451 0.536
1-1/4" x 1/8" U 987 632 439 322 247 195 158 130 110 93 81
Du 0.060 0.093 0.134 0.182 0.238 0.302 0.372 0.451 0.536 0.629 0.730
5’-1”
7 psf C 987 789 658 564 493 439 395 359 329 304 282
Dc 0.048 0.074 0.107 0.146 0.191 0.241 0.298 0.360 0.429 0.504 0.584
U 1480 947 658 483 370 292 237 196 164 140 121
1-1/4" x 3/16" D 0.060 0.093 0.134 0.182 0.238 0.302 0.372 0.451 0.536 0.629 0.730
5’-7”
C 1480 1184 987 846 740 658 592 538 493 455 423
9 psf
Dc 0.048 0.074 0.107 0.146 0.191 0.241 0.298 0.360 0.429 0.504 0.584
1-1/2" x 1/8" U 1421 909 632 464 355 281 227 188 158 135 116 101 89 79 70
Du 0.050 0.078 0.112 0.152 0.199 0.251 0.310 0.376 0.447 0.524 0.608 0.698 0.794 0.897 1.006
5’-10”
8 psf C 1421 1137 947 812 711 632 568 517 474 437 406 379 355 334 316
Dc 0.040 0.062 0.089 0.122 0.159 0.201 0.248 0.300 0.358 0.420 0.487 0.559 0.636 0.718 0.804
1-1/2" x 3/16" U 2132 1364 947 696 533 421 341 282 237 202 174 152 133 118 105
Du 0.050 0.078 0.112 0.152 0.199 0.251 0.310 0.376 0.447 0.524 0.608 0.698 0.794 0.897 1.006
6’-5”
11 psf C 2132 1705 1421 1218 1066 947 853 775 711 656 609 568 533 502 474
Dc 0.040 0.062 0.089 0.122 0.159 0.201 0.248 0.300 0.358 0.420 0.487 0.559 0.636 0.718 0.804
1-3/4" x 3/16" U 2901 1857 1289 947 725 573 464 384 322 275 237 206 181 161 143
Du 0.043 0.067 0.096 0.130 0.170 0.215 0.266 0.322 0.383 0.450 0.521 0.599 0.681 0.769 0.862
7’-3”
13 psf C 2901 2321 1934 1658 1451 1289 1161 1055 967 893 829 774 725 683 645
Dc 0.034 0.053 0.077 0.104 0.136 0.172 0.213 0.257 0.306 0.360 0.417 0.479 0.545 0.615 0.689
Notes:
1. Maximum spans indicated in the table are based on 1/4” deflection under uniform load of 100 psf. Based on experience, this
is the maximum deflection to afford pedestrian comfort and can be exceeded for other types of load at the discretion of the
engineer.
2. Uniform loads (U) and concentrated loads (C) with corresponding deflections (Du and Dc) shown in this table are based on a
maximum bending stress of 18,000 psi for simply supported spans computed using gross sections and nominal sizes of
bearing bars with bearing bars spaced at 1-3/16” OC and grating cross bars spaced at 4” OC. Uniform loads are in units of
psf. Concentrated loads are at mid-span in units of pounds per foot of grating width. Deflections are in units of inches.
3. When serrated grating is specified, the depth of grating required for a specified load and deflection will be 1/4” greater than
that shown in the table.
Page 4 of 8 Process Industry Practices
PIP STE05530
October 2007 Grating Design Guide
5. Openings in Panels
5.1 Banding
5.1.1 Openings in grating panels for penetrating items (e.g., piping, conduit,
structural members, and equipment) should be banded if greater than three
bearing bars are cut.
5.1.2 Except as specified in Section 5.1.3, banding should be 6 mm (¼ inch) thick
and the same height as the bearing bars.
5.1.3 If more than 25 mm (1 inch) of clear space exists between a grating opening
and the penetrating item, the banding should be 6 mm x 125 mm (¼ inch x
5 inches) toe plate as shown in PIP STF05530, Figure 1 (Section A-A and
B-B).
5.2 Dimensions
5.2.1 Dimensions for openings shown in PIP STF05530, Details 4, 5, and 6 should
be determined during detailed design and shown on the design drawings to
permit shop fabrication of the openings.
5.2.2 The dimensions for the openings shown in PIP STF05530, Details 4, 5, and 6
should be determined in accordance with the following guidelines:
a. For Detail 4, dimension “D” of each circular opening should be 100 mm
(4 inches) minimum greater than the outside diameter of the pipe or other
penetrating item, or if insulated, 100 mm (4 inches) minimum greater
than the outside diameter of the insulation.
b. For Detail 5, dimension “D” should be 100 mm (4 inches) minimum
greater than the outside diameter of the pipe, or if insulated, 100 mm
(4 inches) minimum greater than the outside diameter of the insulation.
Dimensions “A” and “B” should provide 50 mm (2 inches) minimum
clearance to each support lug.
c. For Detail 6, dimension “D” should be 150 mm (6 inches) minimum
greater than the outside diameter of the equipment, or if insulated,
150 mm (6 inches) minimum greater than the outside diameter of the
insulation. Dimensions “A” and “B” should provide 50 mm (2 inches)
minimum clearance to the lugs or to lug fireproofing if the lugs are
fireproofed.
d. Unprotected clear space greater than 300 mm (12 inches) should have
guard rail protection.
5.2.3 The guidelines in Section 5.2.2 assume that lateral movement of the
penetrating item is negligible because of thermal growth. If significant
movement is anticipated, the dimensions should be adjusted accordingly.
5.2.4 If insulation or fireproofing on the penetrating item includes corrugated
sheathing or banding hardware that protrudes from the insulation, the
dimensions in Section 5.2.2 should be adjusted accordingly.
Process Industry Practices Page 5 of 8
PIP STE05530
Grating Design Guide October 2007
5.3 Shop Versus Field Fabrication
5.3.1 Because smaller openings frequently are relocated late in the design life of a
project, only openings 300 mm (12 inches) diameter and greater should be
provided by the fabricator.
5.3.2 Openings less than 300 mm (12 inches) diameter should be field located and
field fabricated in accordance with PIP STS05130.
5.4 Large Openings
5.4.1 Additional grating support beams should be added where large openings are
cut into the grating.
5.4.2 Engineering judgment should be applied to large openings because the size and
location of the openings both affect the need for additional support beams.
6. Design Drawings
6.1 General
6.1.1 The location and limits of grating and the direction of the span of grating
bearing bars should be shown on the design drawings.
6.1.2 The appropriate detail in PIP STF05530 for each grating opening, including
the opening dimensions, should be specified on the design drawings. See
Figure 1 for an example method of specifying a detail.
PIP STF05530 DETAIL 6
D = 4’ – 6”, A = 3’ – 3”, B = 1’ – 6”
Note: Other methods of showing this information are acceptable.
Figure 1. Example Opening Detail Specification
6.1.3 For cases where the fabricator does not have the necessary information to
size openings, the design drawings should provide dimensions and details of
shop fabricated openings. For example, PIP STF05530 Detail 2 may be
required for an equipment support provided by the equipment vendor. In this,
and similar cases, the grating opening dimensions should be provided on the
design drawings.
6.1.4 If some grating openings shown on the design drawings are to be field cut,
the drawings should clearly show which openings are to be fabricated in the
shop and which are to be fabricated in the field.
6.2 Fastening
6.2.1 The method for fastening grating to the support steel should be specified on
the design drawings.
6.2.2 If selecting the grating fastening method, the following should be considered:
Page 6 of 8 Process Industry Practices
PIP STE05530
October 2007 Grating Design Guide
a. Grating design and material of construction
b. Electrical conductivity
c. Existence of rolling loads and other usage requirements
d. Integrity of protective coatings and fireproofing
e. Is grating required to be removable?
f. Ease and safety of installation
6.3 Support Plates
6.3.1 Grating support plates, 6 mm x 75 mm (¼ inch x 3 inches), should be
provided in accordance with PIP STF05530, Section C-C and Details 2, 5,
and 6.
6.3.2 The design drawings should clearly show that the grating support plates are
required. Showing these plates on the design drawings is important, as the
grating detailer is normally different from the structural steel detailer, and
these support plates will probably be missed if the structural steel detailer is
expected to catch them.
6.3.3 See Figure 2 for a suggested grating support plate detail.
Figure 2: Suggested Grating Support Plate Detail
Process Industry Practices Page 7 of 8
PIP STE05530
Grating Design Guide October 2007
7. Shop Drawings Reviews
7.1 General
7.1.1 Grating shop drawings should be thoroughly reviewed because the openings
typically change significantly during the design life of a project and the
fabricator needs the latest information.
7.1.2 Also the drawings should be reviewed for interferences between structural
steel and the grating because the grating is typically detailed by a different
detailer than the structural steel.
7.2 Recommended Drawing Review Checklist
7.2.1 Grating detailer is using the latest revision of the grating design drawings.
7.2.2 Grating locations, extents, and span directions are correct.
7.2.3 Interferences with gusset plates where bracing penetrates the grating are
considered by the grating fabricator.
7.2.4 Grating is being split as required so that the grating can be installed without
being field cut.
7.2.5 Locations, sizes, and details of openings are correct.
7.2.6 Locations of banding and toe plate are correct.
7.2.7 25-mm (1-inch) minimum of support has been provided for the ends of the
bearing bars.
7.2.8 Cutouts permit space for insulation and fireproofing.
7.2.9 Structural steel shop drawings show the 6 mm x 75 mm (¼ inch x 3 inch)
plates in accordance with PIP STF05530, Section C-C, and as shown in
Figure 2 of this Practice everywhere the plates are required.
Page 8 of 8 Process Industry Practices
