West Technology – Design for Manufacture changes that met challenging customer requirements

West Technology – Meeting DSM Challenges

The Project

As a longstanding specialist in the fabrication and welding of high-end pressure vessel structures, LTi Metaltech was tasked by their customer West Technology, with manufacturing a chamber pot pressure vessel with the capability to withstand both positive and negative pressures.

The vessel itself was designed to be used by West Technology’s end customer Megger, for the impregnation of electrical windings in one of their high-voltage testing machines.

LTi’s Challenge

In this project, LTi needed to identify new ways of improving the structure’s manufacturability, so they could meet their customer’s requirement for a reduced cost price point. LTi quickly recognised that they would need to make a series of radical changes to their customer’s original design specifications, if they were to resolve both of these challenges in alignment with the customer’s requirements.

There were many elements in the vessel’s original design specifications that presented LTi with challenges:

  • Firstly, a number of its major parts had been designed to be manufactured from large billets of stainless steel, which would be both labour intensive & expensive to achieve their required finished state.

(This together with the extra complexity of some of West Technology’s original designs can be seen in the diagrams below Fig 1, Fig 2a & 2b and Fig 3).

Fig 1: West Tech’s original lid structure
Fig 2a (above) and 2b (right): West Tech’s original locking ring designs
  • Secondly, the chamber pot’s counter weight was originally designed to be made out of a single bar of stainless steel with a mass of 115kg – an expensive option given other alternatives which could have been found. (West Technology’s original design for the chamber pot’s counter weight and removable hinge bracket can be seen in Fig 4 below)
Fig 4: West Tech’s original counter weight and removable hinge bracket design
  • The original designs also posed some geometric challenges; most notably the cone top structure on the lid of the chamber pot, which in its original state would have been expensive for LTi to manufacture with their existing tooling capabilities. (The diameter hole on the cone top structure was previously a lot smaller, which can be clearly seen in the original West Tech design in Fig 5 below)
Fig 5: The geometry of West Tech’s original cone top structure

Consequently, LTi would need to be extremely innovative to achieve the required Design for Manufacture changes necessary to improve the vessel’s manufacturability and reduce the total cost of producing it.

How LTi went about it

Following from detailed review of all aspects of both the original design stages and the related manufacturing processes, LTi’s expert team of innovative designers and manufacturers utilized techniques including 3D modelling to identify design and structural changes which would make the vessel more cost effective to produce.

Working to EN 13445 European Pressure Vessel Standards, which sets the minimum quality standards in the design, fabrication and inspection of vessels; LTi made a number of key changes:

  • Drawing on their extensive welding expertise, LTi reworked the design of major parts previously configured to be manufactured from large billets of stainless steel into welded structures that only required limited welding or finish machining. (Some of LTi’s design changes are illustrated in the diagrams Fig 6, Fig 7a & 7b and Fig 8 below)
Fig 6: LTi’s revised lid structure
Fig 7a (above) and 7b (right): LTi’s revised locking ring designs
Fig 8: LTi’s revised transmission bracket design
  • LTi also altered the chamber pot’s counter weight to a tube design consisting of inserted circular blocks cut from what would otherwise have been scrap metal offcuts. This helped to significantly reduce costs and made the assembly safer. (The changes LTi made can be clearly seen in diagram Fig 9, outlined below)
Fig 9: LTi’s revised counter weight and removable hinge bracket design
  • The design geometrics of the lid’s cone top structure was also revised to better suit LTi’s tooling capability. By increasing the cone top’s diameter hole by a factor of two, it was now able to be rolled out much more cost effectively on a standard rolling machine – saving approximately £1000 for this part alone. (The cone top’s larger diameter hole is clearly visible in LTi’s revised design in Fig 10 below)
Fig 10: The revised geometry of LTi’s new cone top structure

These changes allowed LTi to reduce the total amount of assembly hardware required to fabricate the multiplicity of machined parts. Essentially this reduces the number of assembly steps involved, which further lowers the risk of any potential human errors and subsequent rework which can slow down the manufacture of a structure and push up costs.

(Photos below from LTi’s factory floor showing some stages during the chamber pot pressure vessel’s construction in Fig 11 and Fig 12)

What was the outcome?

LTi successfully met all the required design changes they set out to achieve, improving the manufacturability of the chamber pot and giving their customer a much more cost effective to produce structure that was still fit for purpose.

Fig 14: The finished vessel was successfully subject to both vacuum & hydrostatic pressure tests: