Asset Management

Flange Inspection & Maintenance Services

Rusted And Corroded Pipe Flange
FlangeCuff Before Hot Tapping

Whether they are welded, screwed, or bolted together in a flanged joint, MISTRAS provides an array of inspection and maintenance services for this essential piece of asset componentry.

Used to connect pipes, valves, pumps, and other assets, ensuring your flanges are operating safely is critical to the integrity of piping systems.

Given the intense conditions that process facility equipment often experiences, flanges are subject to a variety of defects, including corrosion, scratching, gouging, pitting, and denting. These defects can lead to flange leaks that waste costly resources and slow your facility’s production, or even lead to an unplanned shutdown in the case of severe leaks. And given the nature of refinery processes, leaks are not only wasteful, but can create a hazard for both machinery and for facility personnel.

MISTRAS offers non-destructive testing inspection (NDT) solutions to ensure that the flanges in your facility comply with industry standards and are free of faults that could lead to leaks and other defects. Our technicians are trained and certified to detect and identify flange damages, quickly, efficiently, and accurately, along with repairing defects and servicing damage once leaks are detected.

Our non-destructive inspection techniques can be applied to flanges of any material, including stainless steel, cast iron, aluminum, brass, bronze, plastic, and others. We help to detect and prevent flange leakage, commonly caused by:

  • Uneven Bolt Stress
  • Improper Flange Alignment
  • Improper Gasket Centering
  • Dirty or Damaged Flanged Faces
  • Thermal Shock
  • Improper Gasket Size or Material
  • High Vibration Levels
  • Improper Flange Facing

In-Service Flange Inspection Services

MISTRAS has a range of non-destructive testing solutions for flange inspection to both detect and identify faults in the componentry. Utilizing ultrasonic and phased array technology, technicians can source and determine corrosion damage, sizing the depth of corrosion across the flange face to assist with further repair and rehabilitation. Our flange inspection and maintenance capabilities identify both flanges with existing defects and at-risk flanges before they cause further problems, helping optimize production and improve asset health.

Hydrofluoric (HF) Alkylation Flange Face Inspection

Piping flanges in hydrofluoric (HF) acid systems are typically subject to under-gasket corrosion. Historically, traditional inspection programs have relied on visual inspection methods to identify and determine corrosion damage to the raised face of the flange. This procedure is costly and involves breaking and remaking flanges that in some cases may not be necessary.

MISTRAS has developed a proven ultrasonic procedure to inspect flange faces in HF Alky service using phased array technology, offering the ability to detect corrosion damage in-situ and on-stream, providing critical data for system integrity while eliminating manpower and safety issues. Our HF flange face inspection technique has proven to be a reliable and cost-effective inspection tool in the prevention of flanged joint failure brought on by damage to the sealing surface, all with no need to break the flange.

The MISTRAS flange face inspection technique examines the entire width of the flange raised face (sealing surface) and has the ability to determine corrosion presence, maximum material loss in terms of depth and any progression of existing corrosion across the sealing surface. It also identifies at-risk flanges and eliminates safety issues regarding “open flange” conditions.

While corrosion detection is an obviously important part of the inspection, the ability to size the depth of corrosion across the flange raised face is the single most critical component of the evaluation. MISTRAS’ R&D teams performed extensive laboratory trial testing to meet a predetermined tolerance value of 0.030 of an inch, yielding an accuracy percentage along the axial plane of the flange raised face.

After inspections are completed, our highly-trained technicians record, analyze, and pictorially-present field inspection data in a final report. Data analysis and final reports may include Word, Excel, and AutoCAD drawings, and are combined into one document for final submittal.

Benefits of MISTRAS approach to HF Alky Flange Face Inspection include:

  • provides a non-intrusive examination process
  • may be carried out in-situ and on-stream
  • helps to eliminate unscheduled downtime
  • identifies at-risk flanges
  • eliminates need to disassemble flanges for inspection
  • eliminates safety issues surrounding ‘open flange’ condition
  • assist in compliance with API Recommended Practice 751

Flange Maintenance Services

MISTRAS also provides maintenance & light mechanical services for flanges of all sizes and materials, including:

  • Flange Torqueing & Tensioning
  • Flange Mapping
  • Flange Sealing
In-Service Method for Installing & Replacing 4-Bolt Pattern Flanges

MISTRAS’ Flange Cuff™ technology provides a simple, safe, and effective solution to for MISTRAS maintenance technicians to install and replace 4-bolt pattern flanges on upstream oil and gas piping assets. The Flange Cuff™ offers the ability to sustain high-pressure, divert stress, and eliminate hazards during the replacement, installation, and maintenance of flange equipment.

The Flange Cuff™ also allows MISTRAS technicians to torque, tension, and maintenance flange equipment in full compliance with industry and regulatory agencies. By stabilizing bolted sections of in-service piping, the Flange Cuff™ safely accommodates "hot bolt" tensioning methods, minimizing potential risk to human and piping assets, while promoting a prompt return of flange equipment.


The Flange Cuff™ comes in 2 frame sizes with inter-changeable teeth to accommodate 1”, 1½”, 2” and 3” flange diameters and fits all 150# raised faced flanges. The small compact, robust and chain-like design allows for easy access to flanged connection in tight areas. The Flange Cuff™ was designed to meet the minimum allowable stress values in accordance with ASME B31.3 and ASME Sec. VII, Div. 1.


The Flange Cuff™ is designed as an inclusive unit with a single torque point swing bolt. The single torque point eliminates the need for multiple components such as hydraulic clamps and modular clamps.

The torque value is determined by the size of the flange and is applied at the single torque point. The torque value meets the required gasket seating force. This unit can be used while working at heights to reduce potential dropped objects.


Once the Flange Cuff™ has been installed at the recommended torque values, then MISTRAS maintenance technicians follow recommended hot bolting procedures. Only one stud at a time may be removed then replaced with new. Once the new stud is installed, it is recommended to hand tighten and torque the stud to 5 foot-pounds of torque. Each stud is replaced and torqued in a cross pattern sequence according to Best Practices flange maintenance techniques.

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