Oil & Gas Industry Case Study


PROJECT 1: VACUUM FURNACE FIXTURING DEVELOPMENT

The project background

The company is a leader in the precision design and manufacture of a range of valves, couplings and fittings used for the transportation of bulk liquids in tank container, road container and rail container industries (fig 1). The transportation of gases and liquids by road, rail and sea must be done safely, and so the company works closely with the industry and regulatory bodies to ensure all their products meet the required safety standards. The company’s products include manways and hatches, airline valves, safety relief valves, discharge valves, butterfly valves, ball valves as well as couplers and ancillary fittings. The company had recently taken delivery of a new vacuum furnace (fig 2) for heat treating the tanker components they manufactured. Heat treatment was used to ensure that the metal components had the most ideal microstructure. This was essential  bearing in mind the harsh and corrosive environments the tanker components would encounter.

(Fig 1)

In a typical vacuum furnace, the product is surrounded by a vacuum during processing as the absence of air or other gases prevents oxidation, heat loss from the product through convection and removes a source of contamination. This enables the furnace to heat materials to temperatures as high as 3000°C. In this case, an inert gas Argon was pumped into the furnace in order to create a contaminant free atmosphere.

(Fig 2 - Vacuum Furnace)

Objective

Fabwell sought to design, develop and manufacture two distinct parts that were to be used for separate applications within the furnace, that was to be heated to a temperature of 900°C to treat the tanker components. These parts included:

 

1.  A frame used for an initial survey of the furnace to ensure it met the stringent American Society of Mechanical Engineers (ASME) standards. The frame was to be almost the same size as the space within the furnace and be used to determine how effective the furnace was in achieving a uniform and consistent temperature throughout its interior, by having thermocouples fitted at all four extremities of the frame.

2.  A special fixture needed to securely hold a very large number of different sized stainless steel tanker components as they were being heat treated. The combined weight of all the tanker components would be around 1200 kg

The technological baseline and status at the start of the project

This was a very complex project for which there was no suitable off the shelf solution available and thus a bespoke programme of development had to be instigated.

Work done

The project began with Fabwell conducting a feasibility study to understand how the vacuum furnace functioned as well as its dimensions and space constraints within; the temperature and heat treatment process; the properties and behaviour of materials that could be used; the size, geometry and weight of the various tanker components etc.; before a suitable design, development and implementation strategy was identified. As part of this process, Fabwell trialled a number of different alloys in the furnace based on the temperature range specified by the customer in order to determine which would be best suited for this application and eventually chose Inconel 600 (BEIS guidelines paragraphs 27b, 31g and 36).

 

A detailed project plan was created to monitor progress and task execution. Fabwell subsequently undertook an iterative design exercise with the aid of CAD software, exploring a number of configurations for the survey frame and holding fixture.

 

The survey frame was made from Ø16mm Inconel following which a suitable welding technique was chosen after a number of trials to enable the frame parts to be joined. A special location point was designed at each extremity of the survey frame to enable thermocouples to be fitted ready for testing. A structurally sound holding fixture was manufactured from laser cut material to a tolerance of +/-0.2mm.The holding fixture consisted of 3 layers in order to accommodate the different tanker components, with each layer separated by pins. The heavier components were placed on the bottom most layer. Furthermore, a series of baskets had to be created to hold the very smallest of components. The drawings for the survey frame and fixture are shown below in figs 3 and 4 respectively.

Testing

Fabwell embarked on an extensive testing process in-house to ensure the survey frame and holding fixture were compliant with the stringent technical specification and ASME standards i.e. with regards to size, weight, fit, form, ease of assembly and dimensional accuracy. The dimensions of each part were first verified on a coordinate measuring machine (CMM) followed by assembly testing and quality checks. Further temperature tests were then carried out by the customer at their premises. The survey frame was initially loaded into the furnace with the thermocouples attached to measure the uniformity of the internal temperature (BEIS guidelines paragraphs 27c and 39). Once the required standards were confirmed to have been met the fixture was signed off by the customer and put into service.

(Fig 3 - Survey Frame)

(Fig 4 - Tanker Component Fixture)