In Place Machining: A Stitch On Site Saves Money & Time

By August 23, 2016 Article, Technology No Comments
Ship Engines are Large, Complex Mechanisms

Ship Engines are Large, Complex Mechanisms   

Image Courtesy of BGribnau at http://www.shutterstock.com/pic-250377604/stock-photo-main-engine-of-a-big-ship.html?src=JAEwCYYzpzdRIFWAJjS-zw-1-2    

The Machine Shop at Your Doorstep  

Also known as portable machining, field machining, on site machining, and in situ machining, in place machining is the process of executing machining operations at the location of the workpiece or equipment. Operations are undertaken to produce the part, repair it, or maintain it.

Simply speaking, portable machining brings the machine shop to the workpiece rather than the other way round. And through this, it offers tremendous time and cost savings. The shipbuilding industry was the first to harness the merits of in place machining.

Note the Size of the Ship Propeller: It is Virtually Impossible to Transport it for Repair or Maintenance

Note the Size of the Ship Propeller: It is Virtually Impossible to Transport it for Repair or Maintenance
Image Courtesy of the United States Department of Transportation at https://en.wikipedia.org/wiki/File:Ship-propeller.jpg

Operators typically opt for portable machining when undertaking emergency repairs. Or when the machinery or workpiece is too large and removing it from its assembly is too complex or too costly. Dismantling such machines incurs significant downtime.

Manufacturers design special purpose machines for in situ machining. Such devices drill, mill, hone, face, bore, and execute other machining operations while the equipment or workpiece remains in place, on site, or on line.

Suppose you have to repair the propeller of your (fairly large ship). With in place machining, you do not have to uninstall the propeller, transport it to the repair facility and back, and re-install it. The repair guys bring their tools and machines to your ship.

Installation and un-installation can be expensively cumbersome, particularly if the part or equipment is large and intricately connected with other parts. Propellers of large ships are fairly large and so are their engines.

Then again, the machining facility might be located miles from where your ship is docked – maybe at an overseas location. On site machining is somewhat similar to online shopping with home delivery instead of going out to shop in conventional, brick-and-mortar stores.

Schematic of a Plain Journal Bearing

Schematic of a Plain Journal Bearing
Image Courtesy of Wizard191 at https://en.wikipedia.org/wiki/File: Hydrodynamic_lubrication_attitude_angle.svg

Apart from cutting down heavily on time and costs, in place machining expands productivity and boosts revenues because it slashes downtime to a bare minimum. Furthermore, the service life of the equipment or tool gets an upward revision as you repair or maintain it immediately.

Please note, downtime is a major headache. It can delay the delivery of a consignment causing significant loss of reputation. And reputation is the key to maintaining or growing your business. Downtime might also require you to make expensive emergency arrangements.

General Applications & Utility

Some of the best known companies in the area of portable machining include:

  • Field System Machining Inc.
  • Mactech On-Site Machining Solutions
  • CLIMAX Portable
  • In-Place Machining Company
  • OnSite Machining UK & Worldwide

Chronologically, field machining is often the last process before you can undertake assembly. Most machining operations can be conducted on site. These include but are not limited to:

  • Welding
  • Weld Preparation
  • Turning
  • Boring
  • Tapping
  • Milling
  • Metal Spraying
  • Facing
  • Drilling
  • Thread Cutting
  •  Keyway Cutting
  • Metal Stitching
  • Flange Facing
  • Reaming
  • Screw Cutting
  • Grinding
  • Trepanning
  • Lapping
  • Honing
  • Pipe Cutting

In place machining demonstrates its striking utility when machining a bearing journal. The bearing journal is the part of a shaft in contact with a bearing. When a bearing fails due to prolonged friction or due to a malfunction in the lubrication system, the bearing journal gets damaged.

You therefore have to repair the shaft via in place machining. It is too expensive and too complicate to dismount the shaft from an intricate assembly. Repairing the bearing journal reduces the outside diameter of the shaft.

This in itself creates another challenge because now you have to use a bearing with a size lower than that of the one at the other end of the shaft. If it is a roller bearing, you have to replace it.

Repairs are acceptable with babbitt bearings because you can repeatedly re-babbitt the housing of the babbitted bearing to any required size. The term babbitt encompasses all those alloys used for creating a bearing surface in a plain bearing.

3 - Microstructure of Babbitt

Microstructure of Babbitt Image Courtesy of Edward Pleshakov at https://en.wikipedia.org/wiki/File:BabbitB83.jpg

Also known as white metal, babbitt metal, or bearing metal, babbitt is a soft, white, and non-ferrous alloy with good anti friction properties that make it a favored candidate for plain bearings. Isaac Babbitt invented the original babbitt metal in 1839 at Taunton in Massachusetts, USA.

Plain bearings are those without any rolling surface. These are the simplest type of bearing made of just a bearing surface. The bearing journal slides over the bearing surface thereby making anti friction a paramount property for the plain bearing material.

Another area that just cannot do without in place machining is the complex operation of machining flat an installed weldment. This is because you cannot maintain the required tolerances if the weldment (workpiece) is first machined flat and then installed.

Precisely why operators undertake tapping, milling, honing, drilling, and boring of weldments only after first installing them. Weldment is a structure formed by welding diverse elements.

In Place Machining in Shipbuilding & Repair

As mentioned, the shipbuilding industry was the first to tap the merits of in place machining. Not surprising because ships can be colossal structures with very large parts.

Consider this. MSC Oscar, the world’s largest container ship, is nearly 400 m long and almost 60 m wide. That is almost as large as four football fields placed end-to-end. Its main engine, the MAN B&W 11S90ME-C two-stroke diesel, is 25 m long, 15.5 m high, and 11 m wide.

Ship Engines are Large, Complex Mechanisms

Ship Engines are Large, Complex Mechanisms
Image Courtesy of BGribnau at http://www.shutterstock.com/pic-250377604/stock-photo-main-engine-of-a-big-ship.html?src=JAEwCYYzpzdRIFWAJjS-zw-1-2

Now, imagine the scale and complexity of the operations if you have to dismantle the connecting rod of this engine, carry it to the nearest machine shop which might be a few hundred miles away, and re-install it. Precisely why shipyards are located on waterfronts.

According to Mactech On-Site Machining Solutions, following are some of the areas on a ship that need to be installed, maintained, or repaired via portable machining:

  • Deck Mounts such as Guns (in case of naval ships) and Antennae have to be machined flat employing operations such as flange facing, milling, and laser metrology

 

As mentioned, machining flat already installed weldments is a better solution than doing it the other way round because the former method enables achieving the necessary tolerances

 

  • Boring of Struts and Stern Tubes is an important operation. Stern tubes support propeller shaft bearings and, as such, need to be correctly aligned with the actual output device
  • Doors of Hatches and Manways need surfacing via flange facing equipment
  • Vertical Line Boring of Rudder Stocks and Propeller Tubes is a necessary operation in the construction and repair of ships
  • Flat Machining of Foundations with Portable Mills and Gantry Mills provides the critically essential flat surface for mounting motors, pumps, z-thrusters, and engine foundationsIn Place Machining: A Stitch On Site Saves Money & Time

In place machining also helps with the production, maintenance, and repair of:

  • Crane Mounts
  • Anchor Winch Mounts
  • Valve Repair
  • Motor and Generator Pads
  • Heat Exchangers

Finally

Seldom does precision become a happy partner with speed. More often than not, there is a tradeoff between these. But by taking the workshop to the workpiece, in place machining effectively bridges the divorce between these two essentials.

Visit out blog for a wealth of information on marine and industrial engineering.

Contact Kemplon Engineering for in place welding solutions as well as the best in marine fabrication, marine pipe fitting, and large scale custom metal fabrication.