Pre Heat treatment
Thermal stresses occur as molten weld pools cool at which point cracking can occur both during and after welding. Moreover, the colder parent or base metal resists the inevitable contraction of the weld metal. In some instances heavy wall materials and aluminum alloys with higher thermal conductivity can act as a heat sink, drawing heat away from a weld and cooling at an accelerated rate. If moisture is present at a welded joint, the high heat of the welding arc will break the water down into its elements, hydrogen and oxygen. The hydrogen by-product easily dissolves into the weld metal and causes weld porosity during weld solidification. During and after completing of the welding process, both the weld pool and the heat affected zone (HAZ) can harden and crack when cooling at a rapid pace. Pre heat treatment is used to prepare the base metal work area so as to improve the integrity of the weld or machining process by raising the temperature gradually thereby improving ductility in advance of the work taking place. This enables the higher temperature area to respond more effectively to the weld or machining process.
THE BENEFITS OF PRE HEAT TREATMENT
- Reduces the levels of thermal stress
- Compensates for high heat loss
- Minimizes the rate of weld hardening
- Reduces the porosity of the weld
- Reduces hydrogen cracking
- Improves micro structure of heat affected zones
Post Weld Heat treatment (PWHT)
Welding and machining induces changes in the chemical/mechanical properties of the base material which could result in distortion, cracking and misalignment (of precision machined holes, for instance). To minimize this affect, controlled heat treatment is undertaken to lower the temperature gradually over a defined period to reduce the stress within the heat affected zone as well as the area immediately adjacent to it, thereby reducing metal hardness and improving ductility across the worked on area. By uniformly heating the base metal (pipe, vessel, etc) to a sufficiently high temperature, just below the metal transformation temperature range, then reducing the temperature over a prolonged, controlled period (dependent on material thickness), the base metal can return to the normal operating temperature and the pre-stressed state.
THE BENEFITS OF POST WELD HEAT TREATMENT
- Relaxes residual stresses
- Relaxes thermal stresses
- Tempers the metal
- Removes diffusible hydrogen
- Metallurgical structure is improved
- Strength and life of the material is enhanced
Pre and post weld treatment has a role to play in normalizing pipes, pressure vessels, reformers, boiler headers, boiler heater tubes, steel mill rollers, furnaces and other critical plant and equipment. It is of particular benefit in start-ups following outages, stabilizing welding and mechanical work.
Furmanite’s Combustion Heat Treatment Services
With over 80 years of developing cutting edge technology, Furmanite is a name you can trust for all of your on-site technical service needs. We own and operate the most advanced and dependable fleet of Heat Treatment Equipment available for use in the field today. Combine our advanced equipment technology, the best trained and most knowledgeable Heat Treatment Technicians, and strategic locations of our field service centers and you have a combination that delivers quality results on time and under budget.
On-Site Field Heat Treatment Technology
Combustion Services and Refractory Dry Outs
- Refractory Dry Outs Give Your Linings
- Improved Refractory Strength
- Refractory Separation Eliminated
- Removal of Mechanical Water
- Minimize Explosive Spalling
- Avoid Thermal Stress
Improved Refractory Strength
- Near 1000 Degrees F Ceramic Bonding Takes Place.
- High Velocity Burners Apply High Pressure and Heat
- This Ensures Cross-Sectional Ceramic Bonding.
- Increasing Refractory Strength, Resulting in Increased Service Life.
Refractory Separation Eliminated
Proper Dry Out Ensures That Dual Component Linings Will Not Experience Sagging or Separation from Anchored Refractory By:
- Utilizing hot, cold, and intermediate thermocouples.
- Ensures proper through wall temperature gradients.
- 1000 degrees f, ceramic bonding takes place.
Removal of Mechanical Water
Refractory Heated too Quickly or Unevenly May:
- Lock moisture in, causing shortened refractory life.
- Proper Dry Out
- Removes mechanical water at closely controlled temperatures below 600 degrees F.
Minimize Explosive Spalling
Controlled Dry Out Will:
- Slowly & safely, force mechanical and chemical water from
- the refractory lining.
- Avoiding pressure buildup and explosive spalling.
Avoid Thermal Stress
Controlled Dry Outs Prevent
- Minute cracking
- Thermally induced stress which weakens the refractory.
Industries Requiring Refractory Dry Outs
- Steel Mills
- Chemical Plants
- Power Plants
Heat Treatment Services
Furmanite’s Heat Treatment Services – Setting a new industry standard utilizing the latest in thermal processing technology
Furmanite, the worldwide innovator and leader in comprehensive on-site and on-line plant and pipeline maintenance continues to set new industry standards by utilizing the latest in thermal processing technology. As the new leader in the heat treating service’s industry, Furmanite has heat treating options from low-voltage systems to high-velocity combustion systems.
Furmanite has developed PLC (Programmable Logic Controllers) and SCADA (Supervisory Control and Data Acquisition) Software to become the leader in thermal processing technology.
Our field personnel are exceptionally qualified and experienced in on-site heat treating services, which is why we’re able to give you fast and correct solutions for any type of heat treatment situation. We manufacture, own and operate the most complete and technologically advanced heat treatment equipment available in the marketplace. Much of the equipment we manufacture is proprietary, is designed by our engineers and built at Furmanite’s manufacturing facilities. Our capabilities provide assurance to out customers that we can address virtually every possible heat treatment process regardless of temperature and /or application.
Furmanite offers a full range of heat treatment services through a wide range of temperatures. We utilize both electrical and fuel fired methods as a source of heating with the objective of bringing your project in on time and on budget.
Furmanite’s onsite electrical heat treatment services include the following:
- Welding Preheat
- Post Weld Heat Treatment – PWHT
- Hydrogen Bake Out
- Line Thaws
- Refractory Dry-out’s
- Phenolic Cures
- Coating Cures
- Heat/Shrink Expansion
- Permanent and Temporary Furnaces
- Warming Systems
- OEM Equipment Manufacturing
- Calibration & Service
- Equipment Sales & Rental
- For onsite service, Furmanite’s fleet of self-contained mobile generator rigs offers the customer 18 points of heating control.
Furmanite’s gas division, specializing in the glass, aluminum, foundry, & steel industries is fast becoming the standard of the industry.
The use of Furmanite’s high velocity burners is an effective method of curing and drying out moisture from refractory materials in the start up process. Working under carefully controlled conditions, we can eliminate the risk of damage that can be caused by spalling and thereby extend the life of the refractory.