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 318-17 Chapter 17 (formerly 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.
Steel allowable tension per bolt is 0.375·Fu·At (AISC 360 ASD, Ω = 2.0 on Fnt = 0.75·Fu; Fu = 125 ksi for B7 ≤ 2.5 in. dia), where At is the UNC tensile stress area At = (π/4)(d − 0.9743/n)². Threaded-fastener strength is governed by ultimate strength Fu, not 0.6·Fy. For a 1"-8 UNC B7 bolt At = 0.606 in², so steel allowable ≈ 28,400 lbs. The bolt must also satisfy the ACI 318-17 Chapter 17 concrete limit states (breakout and pullout); the governing allowable tension is the smallest of steel, breakout, and pullout — for a 12-inch embedment in 4000-psi concrete, concrete breakout governs at about 27,800 lbs.
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 318-17 Chapter 17 (§17.7, formerly D.8) sets the absolute minimums (spacing and edge distance vary with embedment and installation); the 6×/8× values are the practical recommendations for dynamic compressor service.