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How to complete a weld seam removal subsea

Posted by Simon Pownall on Nov 7, 2014 12:00:00 PM


    

MR1500_NEW

Weld seam removal subsea project 

As part of a Subsea 7 project in the North Sea, Mirage was commissioned to supply a portable machine tool to work on a 16” subsea pipeline. The pipeline required seam weld crown removal for clamp installation, and due to the location of the pipeline the machine needed to be diver operated.

Method

With the diver operated requirements for the project, a cold cutting solution was specified. A prerequisite from the customer was to guarantee that the machine supplied by Mirage would not cut into the parent pipeline.

mirage_logo_mr1500For the seam weld, the machine was mounted onto the pipeline and had fixed feed stops. A simple breakdown of the process:

  1. Ensure the 75mm face milling is fully retracted within the spindle housing. Using the chain wrap clamp `V` visually position the Mirage MR1500 central to the weld cap being removed
  2. Route the clamping chain around the work piece and secure the machine assembly using the chain wrap clamps
  3. Connect the hydraulic hoses to the machine spindle and the machine auto feed. If not already positioned, power the milling spindle using the auto feed to one end of the machine to start machining
  4. Start the milling spindle and axially advance the face milling cutter toward the weld cap. With care contact the weld cap and stop
  5. Expected materiel removal 3mm to the parent material. Set the axial slide stop at 2.5mm from the in contact position (step 4) which will act as the positive stop to prevent contact with the parent material
  6. Advance the face milling cutter further into the weld cap to achieve the required depth of cut. 1.0mm depth of cut, expected feed rate of 250mm/min. Repeat the milling passes until the axial slide contacts the axial slide stop
  7. Upon completion stop and isolate the hydraulic power to the machine assembly
  8. Assess the height of the remaining weld cap and decide if further passes are required with controlled depths of cut. Carry out further passes as required.

Milling of the seam welds took less than 60 minutes over a 3 metre length.

Equipment

Mirage supplied a 2 axis MR1500SS and pipe chain clamping system for subsea installation with chain tensioner to allow for diver installation.

The bespoke set-up was created with the MR1500 2 axis milling machine featuring precision linear 'V' rails, ball screw feed, hand and auto feed to 'X' axis and direct drive ISO 40 spindle.

Built for rigidity with a lightweight cast rail, the milling machine is ideal for all general purpose in situ machining, as well as testing subsea conditions.

MR1000 video

MR1000 technical details

Range

  • Maximum stroke - 1016mm (40")
  • Maximum cutter diameter - 254mm (10")
  • Maximum quill spindle down feed - 80mm (3.15")
  • Drive (Pneumatic) - 4.0Hp (3.0Kw)
  • Drive (Hydraulic) - 5.0Hp (3.7Kw)
  • Spindle R.P.M - Min: 50, Max: 640

Feed

  • Pneumatic @ 6 bar (90 p.s.i): 1.5 Hp (1.11Kw)
  • Hydraulic: 2.2Hp (1.64Kw)
  • Hydraulic @ 70 bar (1050 p.s.i): 50 L/min (13 gal/min)
  • Air consumption required: 98 s.c.f.m (2.69 m3/m)

For more information and technical details on the MR1000, download our free Linear and Gantry Milling Buyer's Guide here.

Download the Mirage Machines Linear Milling Buyers Guide

Topics: Subsea, milling

   

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