Make the connection

In the transition from part design to manufacture Planit's advanced CAD/CAM software, Edgecam, is providing the company with consistent and secure manufacturing programs. 

Increasingly, the hydrocarbons used to power our daily lives are being extracted from deepwater fields using ingenious systems under the sea, including tension leg platforms (TLP), floating production units, vessels and remotely operated vehicles. Oil States Industries (UK) is one of the world's leading suppliers of tubular connections required by these oil and gas extraction systems with a product range that includes Swift, Leopard, Lynx, Puma and Merlin connectors. The different products are designed to match the varied needs of the industry.

John Coutts, CNC programmer/supervisor is responsible for all machining activities. Due to the large scale parts required by the oil industry the workshop is equipped with six large CNC machine tools operated by 16 skilled machinists. He says: “As leading manufacturers of subsea connectors and advanced tubular connection systems, we design and manufacture our own products which have an enviable reputation for quality at oil fields across the globe. Connectors simply must not fail because the downtime is expensive and the damage could be catastrophic. An hour or two's downtime offshore could run into millions of US Dollars, so our products carry up time guarantees.” 

Keep things in-house

While the more established products, which have simpler designs, can be produced by subcontracted machining during busy spells, a technically demanding product like the Merlin will always be produced in house to meet the critical tolerances required and also protect the manufacturing process technology. “These connectors have to be machined in a certain way in order to attain the crucial taper and face contact between the two halves of the joint,” Mr Coutts explains. “On the high specification Merlin joints we are working to tolerances of between 1 and 1.5µm.”

To achieve this on the large machines used Oil States Industries keeps to a tight maintenance schedule. Along with laser alignment prior to large projects or during servicing, every machine tool is regularly checked using Renishaw's Q10 Ball Bar. There is no manual inspection and every part produced in the machine shop is 100% checked by the company's CMM department.

The connectors are assembled using Oil States Industries Proprietary Tooling. Annular ring grooves are machined into both the male and female sides of the tapered connectors, which after assembly lock together to provide a metal-to-metal sealed joint that is stronger than the parent material of the pipe section it is welded to. Machined from forged steel rings the connectors are cut using NC code programmed by Mr Coutts using Edgecam. He uses the advanced CAM software both in solid and wireframe mode. “We use the solid model, provided by our design team using Autodesk Inventor, to simulate the NC program for verification. Verifying in Edgecam prior to sending program to the shopfloor highlights any potential collision points and allows me to thoroughly check any issues before machining commences,” he says. “The need for the level of CNC program security offered by Edgecam becomes evident given that some components can take up to 110 hours each to machine.”

On the wire

All programming is carried out offline using Edgecam and bespoke post-processors have been written by Planit staff for Oil States Industries' machine tools. Mr Coutts sets all the cutting data, feeds and speeds in the software and the program is never altered on the shopfloor.

Edgecam's ability to turn threads and grooves is critical to the company's products and using the pecking function minimises the build up of swarf – forming ‘bird nests' on the part. Mr Coutts also programs stop points into the code where the tool is backed away to allow the operator to remove any swarf built up on the component and carry out inspection activities. He points out: “It is much easier for our application to use Edgecam in wire frame. The design department provides the 2D DXF profile needed to generate the tapered grooved contour required on the connector.”

As the machining process for the various connectors follows similar procedures with variation in diameter groove profile, Mr Coutts is looking in the long-term at using Edgecam's PCIs to construct a macro program, which will significantly reduce the time required to generate the CAM program.

For Tension Leg Platform applications, sections of pipe up to 40 inch diameter and up to 72m long each with a female Merlin connector on one end and a matching male Merlin connector on the other – called a box and pin – are used to tether the floating oil platform to the sea bed in water depths in excess of 5,000 feet. These tethers culminate in an Oil States Roto-Latch connector, which is sunk into the bedrock and provides the anchor point.

The machined Roto-Latch was designed and then programmed using Edgecam, with the finished program just short of 1 million lines of NC code. “Because the Oil States connectors are holding the rig to the seabed, quality control is critical and each component must pass a 200% inspection procedure.” Mr Coutts affirms. “Components cannot be measured for 12 hours after machining to remove thermal anomalies and they are then inspected again within a defined timeframe with the results of both CMM checks compared to ensure the part is within tolerance. This is followed by a 200% penetrative UV dye non destructive crack test.”

Customer driven

New developments are driven by customers' ever changing requirements and new products will allow the company to target new markets. One such new product is currently at the prototyping stage, and Mr Coutts has programmed it on Edgecam and carried out machining trials to prove the manufacturing process.
From a small team of around 90 people just 15 years ago, Oil State Industries' Aberdeen site has grown to 140 employees, working day and night shifts to support the global oil and gas industry. Turnover today for this highly advanced facility is around £50 million and it is one of the most profitable sites for the American-owned company.
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