Urgent Lead Time: EMG Delivers Hot-Dip Galvanised ASTM A193 B7M Collar Bolts in Record Time

Overview

A valued long-term client required non-standard collar bolts in ASTM A193 Grade B7M for a sour-service flanged connection where a plain stud could not provide the required shoulder location. Collar bolts are not a catalogue item — the integral collar must be machined into the blank before threading, which normally pushes lead times well beyond the client's shutdown window.

Challenge

The bolts were needed inside a maintenance window that left no room for a conventional make-to-order cycle. B7M adds a hardness ceiling of 235 HBW that must be verified on every piece, and hot-dip galvanising to AS/NZS 4680 introduces an additional external process step plus thread clearance control after dipping. Any one of those steps slipping would have delayed the joint.

Solution

EMG released certified B7M bar to a nominated machining partner and ran collar machining, threading, hardness verification and galvanising as an overlapping sequence rather than a linear one. Threads were oversized ahead of dipping so nut assembly was guaranteed after coating, and each bolt was individually hardness tested before dispatch. Bolts were sleeved in protective mesh and palletised for direct site handover with matched A194 2HM nuts.

Results

• Collar bolts delivered inside the client's urgent shutdown window
• 100% individual hardness testing to the 235 HBW NACE ceiling
• Galvanised threads verified for free-running nut assembly after dipping
• Zero rework or dimensional rejections on receipt

Compliance & Documentation

EN 10204 Type 3.1 mill certification with heat number traceability, individual Brinell hardness records for NACE MR0175 / ISO 15156 sour service compliance, and a hot-dip galvanising certificate to AS/NZS 4680 including coating thickness readings.

Products Supplied

• ASTM A193 B7M Collar Bolts (Made-to-Drawing)
• ASTM A194 2HM Heavy Hex Nuts
• Hot-Dip Galvanised Coating to AS/NZS 4680