Complex Manufacturing for
Critical Applications

The Heat Debate: Pros and Cons of Hot and Cold Bolting Techniques

Fasteners are tools used in every industry and can be permanent (single-use) or temporary (can be removed and re-used) solutions. Customized bolts and screws are the main types of fasteners used by most industries, including aerospace/military/defense, automotive, construction, marine, medical, mining, energy/power generationpetrochemical, and more. B&G Manufacturing specializes in hot and cold bolting techniques. We also understand your company goals and provide solutions that will best serve your industrial application requirements. 

A bolt is used with a nut and is fastened or tightened by torquing the nut. There are advantages to choosing screws vs. bolts but basically, the unthreaded part of a bolt makes it stronger than a fully threaded screw. 

Hot and Cold Bolting Techniques 

Forging is at the core of the B&G manufacturing process. – WILLIAM EDMONDS 

Firstly, hot bolting is the process of re-tightening or replacing corroded bolts from flange connections on an operating piece of machinery. Additionally, it’s used to avoid a production shutdown and resolve hazardous material containment issues. Hot bolting restores the integrity of the joint and reduces the number of containment events. The process includes calculating the remaining bolts’ stress when the bolt is removed as well as estimating accurate bolt force that maintains a safe gasket pressure during tightening. 

There are two basic types of hot bolting projects: 

  • Sequential – ASME (American Society of Mechanical Engineers) says hot bolting is sequential removal and replacement of bolts on flanged joints while the unit is under operating pressure. 
  • Single-stud – This technique is used to prevent metal erosion before cool-down. (“Half-bolting” is the removal of every other bolt in a flange.) 

Furthermore, when working with one or a series of flange bolts, both industrial bolting techniques involve removing bolts one at a time, relubricating, reinstalling/replacing, and then tightening. 

High-temperature bolting is a hazardous process. A reputable company will perform a risk assessment before attempting hot bolting. In addition to the dangers of working with high-temperature equipment in any environment, risks can include managing flange/pipe deterioration and difficulty accessing the work area. Hot bolting should only be used for 8-bolt flanges that have referenceable design specs and records. 

There aren’t cheaper processes that are as effective as hot bolting …which is why it still exists

Cold bolting is the manufacturing process in which room-temperature metals are used to form fasteners. It’s a large-run process that is safer when it’s an option, but the tooling costs are higher. 

Cold bolting: 

  • Allows for greater precision/used for complex head formations 
  • Faster with high repeatability 
  • Reduces scrap material 

Most materials (aluminum alloys, cobalt, copper, nickel-based alloys, some titanium grades, stainless steels) can be cold-bolted but not all (alloy steels, carbon steels, and titanium grade 5). Cold bolting tends to decrease materials’ pliability. 

Quality-Certified Industrial Components 

Our client relationships are based on our superior capabilities to serve a diverse marketplace, and our reputation for problem-solving solutions that save companies time and money without compromising safety. Why choose B&G Manufacturing? 

  • Bulk-buying power and large inventories give you lower pricing and faster deliverables. 
  • Extensive experience with multiple industries lends itself to innovation and solutions-oriented ideas for you. 
  • We provide professional customer care reps with strengths and experience in your industry. 

Disney said it best: It’s a small world. Global production and purchasing are common. Still, the advantages of North American local sourcing (“Made in the USA”) are vast and becoming increasingly preferred. 

Putting A Pin In Hot and Cold Bolting

B&G Manufacturing has been a leading manufacturer and supplier of specialty fasteners and precision parts for over 60 years. We see 2024 as a landmark year for our company, as we integrate our successful, critical manufacturing capabilities with progressive technology and innovation. This year we’d like to expand our industry- and customer-base relationships to include you. 

Call 800-366-3067 or contact B&G Manufacturing to discuss your projects or request a quote.