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
Details, formula, and sources
The 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.
first_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.
The Expansion Joint Manufacturers Association (EJMA) 4-diameter / 14-diameter guide-placement rule and the manufacturer installation guides, by name.
The 4D/14D first-and-second-guide rule is the EJMA published placement standard, republished in every manufacturer's installation guide.
Estimate. AHJ and licensed professional govern.
Field names used by the API: pipe_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