Weld Repair

Specialized weld repair and hot tap assessments from Equity Engineering support facilities in maintaining mechanical integrity without unplanned shutdowns. We provide authoritative in-service welding guidance, thermal modeling, and PWHT for pressure vessels and piping. This metallurgical analysis optimizes welding parameters to mitigate burn-through, cold cracking, and creep damage in high-temperature assets.

Download the Materials & Corrosion Overview here.

Why Do You Need a Welding Assessment?

Understanding the residual stresses associated with welds in pressure vessels, piping, and other structures is essential when designing or repairing equipment for the oil and gas, petrochemical, chemical, fertilizer, and other industrial processing industries. However, it’s important to know the differences between repair welding versus fabrication. Knowing those differences and applying that knowledge in the field will prevent catastrophic failures.   

Equity’s welding engineers will review your current welding procedures and provide practical repair guidance for any type of damage mechanism to ensure new construction or planned maintenance is compliant with the latest industry standards.  

Equity’s Weld Repair & Hot Tap Assessment Services

  • Review welding procedures and provide inspection recommendations
  • Determine materials or filler electrode requirements
  • Conduct onsite failure analysis and root cause investigations
  • Specify weldability concerns and discuss welding metallurgy
  • Identify preheat, interpass, and post-weld heat treatment requirements
  • Provide technical advice on welding and fabrication
  • Conduct cleaning and preparation

Hot Tap Assessment

In-service welding, or hot tapping, is required when in-service equipment needs repairs or when nozzles, tees, sleeves, or other fittings need to be added without bringing the unit offline. However, if fluid dynamics, heat transfer, and welding parameters aren’t properly understood, the result can be catastrophic. We perform detailed hot tap assessments to provide optimized welding parameters that address the risks of burn-through, fluid decomposition, unintended chemical reactions, and delayed weld cracking. We also offer practical guidance related to hot taps.

Our hot tap assessment services include:

  • Evaluate high-risk scenarios on a case-by-case basis
  • Develop special guidance for preparation, including washout or flush for contaminated services
  • Perform detailed sensitivity analysis modeling to identify changes in fluid conditions
  • Address specific application risks (e.g., fluid decomposition, or unintended chemical reactions)
  • Recommend modified welding parameters and techniques
  • Develop specific inspection recommendations
  • Calculate mechanical loads and design loading for existing piping system during and after the hot tap connection

Repair Welding

There are many nuances associated with carrying out repair welds. When repairing in-service equipment, it is essential to understand equipment metallurgy, material properties, potential damage mechanisms, welding procedures, inspection techniques, and many other variables.

At Equity, we help you with:

repair welding
  • Weld solidification and liquation cracking
  • Preheat, interpass, or post-weld heat treatment (PWHT) limitations
  • Weld corrosion or stress corrosion cracking (SCC)
  • Welding of in-service pipelines
  • Weld residual stress and distortion
  • Dissimilar materials welding
  • Cladding or buttering requirements
  • Failure investigation, analysis, and root-cause analysis
  • Inspection recommendations

Post-Weld Heat Treatment (PWHT)

PWHT effectively minimizes weld residual stresses in pressure vessels and piping equipment. Conducting PWHT on carbon and other low-alloy steels will generally help mitigate the risk of crack initiation and ultimately brittle fracture; however, PWHT layouts need to be properly engineered. Equity routinely provides practical recommendations for local PWHT layouts and heating parameters to mitigate the risk for weld cracking or distortion due to severe metal temperature gradients.

Creep Damage

Creep damage progression is known to be accelerated by the mismatch in creep properties of the weld deposit, heat-affected zone (HAZ), and adjacent base metal. This property mismatch results in stress intensification and triaxial tension that can accelerate creep damage near the weldment. Equity specializes in high-temperature analysis of welds and can offer practical inspection guidance for components operating in the creep regime.

Welding Analysis Software: eecHotTap

The cloud-based HotTap software tool assesses the suitability of hot tap welding procedures or repair welds by evaluating the risk of burn-through and cold cracking due to rapid cooling. HotTap uses the latest advances in weld thermal simulation technology to:

  • Support historic HotTap welding models, including weldolets and user-defined custom fluid mixtures
  • Use finite element analysis (FEA) solver to simulate the weld’s thermal history
  • Evaluate the effects of preheating
  • Analyze liquid boiling cases, including nucleate, transition, and film boiling

Related Topics

  • “Equity Engineering has done a great job providing CCDs. They communicated well on what information was needed and produced solid work.”

    – CCDs & IOWs, North American Refinery

  • “It is always a pleasure working with this team. They were all very professional and demonstrated solid technical knowledge and experience. Well done!”

    – Omega Creep Testing, North American Refinery

  • “Equity has consistently provided our global company with excellent support, especially during emergency situations.”

    – Weld Repair Project, Latin America Refinery

  • “Appreciate the detail of analysis that was performed and the research done to understand the system in order to understand the root cause for the failure.”

    – Failure Analysis, North American Chemical Facility

  • “Have had good experiences with this job and others. I find Equity very supportive and honest.”

    – Weld Repair Project, Nitrogen/Fertilizer Manufacturer

  • “All personnel were very professional and resolved the matters in a timely fashion. We continue to utilize Equity Engineering. We did it again during our current turnaround event at our Louisiana site involving a fitness for service.”

    – Structural Stability Assessment, Louisiana, USA

  • “Equity Engineering went above and beyond to assist with our GOH vibration study. They completed the work in a timely manner, kept me informed, and delivered a great final report.”

    – Vibration Clamp Design, Texas, USA

  • “Equity has consistently provided our global company with excellent support.”

    – Weld Repair Project, Latin American Refinery

  • “The work that the team did was very valuable. The whole team demonstrated great knowledge and professionalism.”

    – Wind-Induced Vibration Analysis, European Refinery

  • “I have been collaborating with Equity Engineering for many years and every time I have been extremely happy with their knowledge, professionalism, and dedication.”

    – Fitness-for-Service Assessment, North American Refinery