Industry Best Practices · ASTM A-193 B7 · ACI 318
For load-based sizing verification
Anchor bolt types, embedment requirements, spacing rules, and tensioning procedures
Hooked bolts (J-bolts, L-bolts) develop pullout capacity through the small bend, which straightens under cyclic tension from reciprocating compressors. Straight bolts with a bottom anchor disk (≥ 4× bolt diameter) develop full concrete-cone pullout per ACI 318 Appendix D and resist dynamic loads without elongation.
Industry practice for reciprocating compressor foundations is a minimum embedment of 12× bolt diameter (per GMRC and PCRC guidelines), with 15–20× preferred for high cyclic-load service. For a 1-inch bolt this means at least 12 inches of embedment, with the bottom 4 inches reserved for the anchor disk and cover concrete.
Allowable tension per bolt is 0.6 × Fy × At, where Fy = 105 ksi for B7 (≤ 2.5 in. dia) and At is the UNC tensile stress area: At = (π/4)(d − 0.9743/n)². For a 1"-8 UNC B7 bolt this yields At = 0.606 in² and an allowable tension of about 38,200 lbs per bolt at ASD level.
Sleeves (typically 2× bolt diameter + ½" clearance) allow ±¼ to ⅜ inch of horizontal adjustment after the concrete cures, so the compressor frame can be aligned to the driver before the bolts are grouted in. Cast-in-place bolts must hit template position within 1/8 inch — much harder to achieve and impossible to correct.
Minimum edge distance is 6× bolt diameter to prevent side-face concrete blowout, and minimum bolt spacing is 8× bolt diameter to prevent shear-cone overlap between adjacent bolts. ACI 318 D.8 sets the absolute minimums (3× spacing, varies on edge); the 6×/8× values are the practical recommendations for dynamic compressor service.