Expansion Joint / Loop Guide Spacing (EJMA 4D/14D)
Where the first two guides go so an expansion joint or loop compresses instead of buckling sideways.
Example
You enter
- Pipe OD (in) 4.5
- First-guide multiplier (D) 4
- Second-guide multiplier (D) 14
You get
- First guide (from the joint) 18
- Second guide (past the first) 63
- Guide2 from joint (in) 81
Checked against published worked examples from: Metraflex.
Details, formula, and sources
ScopeThe first guide within four pipe diameters of the joint, the second within fourteen diameters of the first, per the Expansion Joint Manufacturers Association (EJMA) rule. A 4 in line (OD 4.5) guides at 18 in then 63 in past it (81 in from the joint); the distances scale directly with the diameter, the multipliers are the fixed rule. Beyond guide 2 the intermediate spacing comes from the EJMA table or the pipe-column stability calc. This places the planning guides; the anchor and joint selection govern.
Formula or tablefirst_guide = d1_mult x pipe_od (default 4 diameters from the joint); second_guide = d2_mult x pipe_od (default 14 diameters past the first guide); guide 2 is first_guide + second_guide from the joint.
Source and editionThe Expansion Joint Manufacturers Association (EJMA) 4-diameter / 14-diameter guide-placement rule and the manufacturer installation guides, by name.
Free accessThe 4D/14D first-and-second-guide rule is the EJMA published placement standard, republished in every manufacturer's installation guide.
What governsEstimate. AHJ and licensed professional govern.
API field namespipe_od_in, d1_mult, d2_mult, first_guide_in, second_guide_in, guide2_from_joint_in
- First two guides first guide within 4 pipe diameters of the joint, second within 14 diameters of the firstEJMA
- Beyond guide 2 intermediate guide spacing comes from the EJMA table or a pipe-column stability calc (user-supplied)EJMA
- Anchors the anchor loads and joint selection are a separate design and governEJMA / manufacturer