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Compact flanges: applications, benefits and machining kits


Above: The compact flange a sealing ring and angled faces which come together when the bolts are tightened


Applications for compact flanges

Compact Flanges are commonly used in offshore rigs and various subsea installations including;

  • Flexible and rigid risers
  • Subsea production flowlines
  • Christmas trees
  • Subsea gas-lift and water injection flowlines
  • Subsea metering equipment
  • Subsea, valves, pumps and compressors

Joints of this type are thought to be stronger than the actual pipe they are connecting and also have better fatigue properties than the flange pipe weld. This means they are specified for critical areas where conventional flanges are not accepted. There are commonly 3 sealing faces in a compact flange joint, with the ‘heel’ sealing the internal bore.

Benefits of compact flanges

As the name suggests, compact flanges and are much smaller than conventional ASME flanges, but there are also many other significant advantages such as;

  • Lighter (saving up to 80% in weight)
  • The gapless design avoids corrosion on flange faces
  • Blots do no need to be re-tightened regularly
  • Fully flush bore does not disrupt flow
  • Incorporates 3 sealing faces
  • Less likely to fail when used with flexible components
  • More reliable sealing: using a metal seal ring instead of gaskets and with multiple sealing areas.


Swivel type compact flanges

Alignment is an important and critical feature when bolting subsea pipeline flanges, so using a flange that swivels around the joint makes the process of aligning bolt holes in subsea environments much easier, therefore reducing the dive-time and the cost of the operation.

Machining compact Flanges

Despite the best efforts of flange manufacturers to protect the flange’s sealing surfaces, damage can occur in transit and during other stages before final joint assembly. In these situations, it is necessary to resurface the flange which is possible using a flange facing machine.

With this in mind Mirage has developed a range of internally and externally mounted products for compact flange machining which can be used with an attachment for accurate machining of the taper angles specific to compact flanges. The conversion kit allows for angle adjustment of the saddle carriage assembly and contains components and tools including a digital indicator, operator manual with angle tables.


The MM300E CF  flange facing machines is one of several that can be used with a compact flange machining kit

Flange facing machines currently suitable for machining compact flanges include the MM300E, MM600E, MM860i MM1000i

If you have a potential project needing this product right now  please click here to get in touch.

You are also welcome to download our guide The Complete Guide to Managing Flanges

Download The Complete Guide to Managing Flanges



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