The Patternless® process provided the quickest and most cost-effective option for Severn Glocon when they needed a valve casting on short delivery to meet the demands of the Danish offshore sector.
Severn Glocon, based in Gloucester, UK, have been designing and manufacturing control valves and actuators for over 40 years, giving them extensive international experience across the whole spectrum of the Process Industry. At Severn Glocon, “Specials” are “Standard” and often valves are needed on short delivery – two factors which encouraged the company to look at the benefits of the Patternless® Process developed at Cti. By directly machining the sand mould used in the casting process, lead times can be significantly reduced, whilst accuracy is improved and extremely high quality and surface finish are maintained.
Severn Glocon’s customer, Valtor – Offshore Esjberg, based in Denmark, required a valve for the Danish Offshore sector of the North Sea. The valve is a 12″ ANSI class 900lb Angle Globe Valve fitted with a low noise trim and operated by a powerful piston actuator and a ‘Smart’ positioner, to be installed on a Hydrocarbon Gas Control application.
Although many of Severn Glocon’s valve bodies are sand cast using existing and standard pattern equipment, this Angle valve had no pattern and was on a short delivery. The company would normally have considered a solid forging or a fabricated forged body as the method of production in order to meet the tight deadline but, on learning of the Patternless® Process, Severn Glocon realised that casting could provide a faster and more reliable option.
Allan Homfray, Technical and Commercial Manager at Severn Glocon, explains: “Cti’s Patternless® casting process was chosen because the overall lead time, when compared to fabricated forgings with a great deal of NDE and weld qualification approvals, was considered shorter and more reliable. Ultrasonics and MPI were required on the casting and Cti was able to offer this service in house, which was an added benefit“.
The 3D model of the valve design was used to create the data to programme the sand machining system at Cti. The blocks of sand constituting each mould half were first machined to produce a ‘sand core box’. These were painted with a standard mould coating and cores rammed up and stripped. The ‘sand core boxes’ were then further machined to provide the mould cavities, i.e. the wall thickness was created by machining. The feeding system was also machined along with the lettering and ingates to connect with the tile runner system. After painting, the core was positioned accurately in the prints from which it was made and the moulds closed and poured. Non-destructive testing proved the casting met the stringent quality requirements.
Allan Homfray was extremely pleased with the results:
“The quality and definition of the lettering was particularly impressive and would not have been incorporated into temporary patterns that might have been produced to satisfy this requirement. There is a further consideration with this process“, he added. “Low usage patterns are stored at foundries and when required to be used they are often beyond repair or carry expensive refurbishment costs. The ‘pattern’ in the Cti process is held as software and does not deteriorate with time.”
Allan continued, “We will now consider this process whenever standard pattern equipment is not available. Non standard shapes which require patterns, or would require extra machining if forgings were chosen, are prime candidates. Special materials can also be accommodated for components that could not be produced in the foundry where the standard pattern resides, i.e. stainless steel parts replacing iron components, for low temperatures etc.”
“At present, our use of the process is only limited by the size of the machine and the pouring capacity at Cti. Because of this we will mostly use it for valves in the 6-12″ range. Were the process available in other foundries, this would help to widen our scope for its use.”
Cti is making moulds for Members to pour themselves or producing castings on their behalf, both to demonstrate the process and to assist them secure business where delivery times cannot otherwise be achieved and where quality and accuracy are critical. The process has already stimulated great interest and Member companies are now installing their own machining equipment, and benefiting from the expertise and experience available in Sheffield.
For further information on the Patternless® process contact Mike Ashton
For further information on Severn Glocon please contact Allan Homfray, Severn Glocon Ltd, St Luke St, Southgate Street, Gloucester, UK, GL1 5RE. Tel:(0)1452 318 900 Fax: (0)1452 318901 or look on their website: www.severnglocon.com