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What Is a Base Plate? | Piping Engineering Glossary
What Is a Base Plate?
In piping engineering and process engineering, a base plate is a flat steel plate welded to the bottom of a support member, such as a post, column, or pipe stanchion, so the support can bear on a concrete foundation or structural steel. It spreads the concentrated load from the support over a larger area and provides holes or slots for the anchor bolts that hold the support in place.
How Base Plates Carry Load
A support carrying pipe weight pushes down on its base plate, which distributes that force across the concrete so the bearing pressure stays within safe limits. The same plate must also resist sideways and uplift forces from friction, wind loads, and seismic loads, which are carried into the foundation through the anchor bolts.
Base plates appear wherever piping is supported from grade or from a slab, including stanchions under elbows, posts under a trunnion support, and frames carrying several lines. A thin layer of non-shrink grout is usually placed beneath the plate so it bears evenly on the concrete even if the foundation surface is slightly uneven.
Applications
Supports at Grade
Most pipe supports that rise from concrete pads use base plates, from simple pipe stanchions to braced frames near pumps and tanks.
Anchors and Fixed Points
An anchor support relies on a well-designed base plate and anchor bolts to resist the large forces from restrained thermal growth.
Sliding Arrangements
Where a line must move, the base plate may carry a pipe shoe or slide surface, or have slotted holes that allow limited adjustment during installation.
Benefits
Spreads Concentrated Loads
A properly sized base plate keeps concrete bearing stress low and prevents crushing or cracking of the foundation.
Provides Secure Anchorage
Anchor bolts through the plate resist overturning, uplift, and lateral forces on the support.
Allows Field Adjustment
Shims, grout, and slotted holes make it easier to set supports at the right elevation and position.
Limitations
Sizing Requires Several Checks
Designers must check plate bending, concrete bearing, weld strength, and anchor bolt tension and shear together, which takes more effort than it first appears.
Corrosion at the Interface
Water trapped between the plate and concrete, or at poorly drained grout, can corrode the plate edges and anchor bolts.
Limited Flexibility After Installation
Once anchor bolts are cast into concrete, moving or enlarging a support usually requires new anchors or post-installed bolts.
FAQ
How thick should a base plate be?
Thickness depends on the support load, the plate’s overhang beyond the support member, and the steel grade. Engineers calculate the bending in the plate from the sustained loads and occasional loads it carries rather than using a fixed size.
Why is grout used under a base plate?
Grout fills the gap between the plate and the foundation so the load is spread evenly, and it allows the plate to be leveled precisely before final tightening of the anchor bolts.
Do pipe supports need anchor bolts?
Most supports at grade do, to keep them from shifting or overturning. Lightly loaded supports on structural steel may instead be bolted or welded directly to the steel member.
What causes base plate failures?
Common causes include undersized plates, missing grout, corroded anchors, and unexpected loads from thermal movement. These are typical findings when investigating a pipe support failure.
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