TWI services for SMEs in the UK's North East
improving business performance through
best practice & innovation
Case studies
Help when the heat is on
Subsea engineering benefits from review
Quality improved t'anks to TWI
Earth moving giant cleans up
Regional technology project pops welded bubbles
Help when the heat is on
| Hot gas extrusion welding, one of the many conventional and advanced processes which TWI can help companies use more profitably |
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In bidding for a contract to build a 20 000 litre tank in polypropylene, SK Plastics of County Durham contacted TWI for technical advice and assistance to identify any unforeseen problems in advance.
Under the Joining Forces North East programme they were able to take advantage of on-site assistance, including trials, from Andy Knight, a highly experienced Plastics Welding Instructor from TWI Technology Centre (North East) in Middlesbrough.
Keeping apace with technology, SK Plastics had recently purchased a new Leister Weldmax extrusion welding gun. Initially Andy spent time assisting with the optimisation of the welding parameters for this equipment utilising his knowledge and past experience. He then discussed various joint designs and fabrication technique options that could be used, whilst maintaining integrity of design and compliance with British Standards.
As the tank was so large it could not be fabricated in the normal workshop space; a different site was therefore acquired. The tank was made in two sections, which were then joined using the hot gas and extrusion welding processes. SK Plastics has since relocated to much larger premises in order to facilitate such future contract work.
Not only was the tank successfully fabricated but SK Plastics also benefited from the discussions. The processes and parameters examined in general terms will be of help in future projects with cost and efficiency benefits for the company.
Hot gas extrusion welding, one of the many conventional and advanced processes which TWI can help companies use more profitably.
TWI's help was available to SK Plastics under the Joining Forces North East technology transfer programme.
Subsea engineering benefits from review
Deepstar Subsea are a company in the North East of England involved in the design and manufacture of engineered products for subsea applications.Like all companies, Deepstar Subsea wanted to improve customer service, and one way of achieving this was to improve their bidding system for duplex pipework and other materials in common use in the oil and gas industry.
| A Deepstar Subsea welder completes a weld in stainless steel pipework for deep sea operation. The company made some 300 similar welds for this contract, all meeting the highest quality standards |
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Specifically, it would be an advantage to be more aware of possible problem areas or technical difficulties particularly in the field of joining dissimilar materials.
Harry Forrest from Deepstar contacted TWI having heard about their Joining Forces programme. "I had a number of high alloy steels and nickel based alloys I wanted to review for the business, and required that the information be presented in a succinct and easy to use format. TWI has the experience and expertise to coordinate such a minefield of information".
The programme was able to offer the company a Review of its materials selection requirements, the results of which were presented in a comprehensive table summarising material data and welding considerations for alloys being specified for new contracts.
The information covered such topics as typical mechanical properties, welding processes, the need for pre-heat and potential problems in manufacturing applications.
Deepstar Subsea were very pleased with the outcome of the Review and are now using the information on an everyday basis.
TWI's help was available to Deepstar under the Joining Forces North East technology transfer programme.
Quality improved t'anks to TWI
Newton Aycliffe-based Permoid Industries has boosted welded fuel tank quality by making changes in its manufacturing procedures. The changes resulted from taking on board expert technical advice available at no charge via the Joining Forces North East business support programme run by welding and joining specialist TWI.Permoid produces several thousand diesel fuel tanks for earth moving vehicles each year to a demanding service specification. Quality Manager, Steve Toas initially asked TWI to address two issues as part of their continuous quality improvement drive relating to the welding of fuel tanks.
Steve explains: 'Permoid continually seeks to improve its welding operations. It was important to know whether these issues originated from a manufacturing defect or the result of service incidents. We wanted to minimise any need for re-work by improving our procedures so that we can enhance quality and reduce costs.'
| Photo courtesy of JC Bamford Ltd |
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Focusing on the tank corner tie-in welds and the drain plug weld region, a TWI engineer carried out a Joining Forces Product and Process Review. This confirmed that despite the combination of robotic and semi-automatic welds in the same application, the corner weld quality was consistent and demonstrated good fusion and met the design requirements of the tank. TWI then gave recommendations on how to maintain this quality on each unit.
Investigation of the second issue, a failed drain plug, revealed that a crack propagated by fatigue from the toe of a fillet weld had caused a leak.
Further examination concluded that this was more likely the result of inappropriate design than of poor weld quality. TWI recommended that further information be gathered about any other failures of this nature before deciding any remedial action.
TWI's help was available to Permoid under the Joining Forces North East technology transfer programme.
Earth moving giant cleans up
Following on from a useful Product and Process Review, Permoid Industries Ltd asked TWI to conduct an analysis of debris from the fuel tanks that they manufacture for earth-moving giant JCB.Steve Toas, Quality Manager comments: 'JCB is an important customer of ours and Permoid aim to meet and exceed cleanliness specifications. We were asked to carry out an analysis on two samples of debris and worked with TWI in this examination.'
| Back scattered electron images of spatter particles |
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- assessing the different types of particle and their source
- assessing the chemical composition of each type of particle
- determining the proportion of each type of particle
- suggesting methods of reducing particulate matter
Using a light microscope, a scanning electron microscope (SEM), image analysis and photomicrography, TWI was able to distinguish three main types of debris - scale, spatter and swarf. Permoid were advised on the likely sources of the debris and what action they can take to prevent future incidences. Recommendations included the use of a backing gas to minimise scale, and the manipulation of the welding parameters and changing the welding gas to reduce spatter. The swarf had been introduced by external contamination, sources of which need to be identified independently.
'Thank you for delivering the report within the timescale I requested. I was very impressed with the professionalism of the report and the conduct of all TWI's staff; we are now producing an even better quality product as a result of your recommendations', said Steve Toas.
TWI's help was available to Permoid under the Joining Forces North East technology transfer programme.
Regional technology project pops welded bubbles
When welders at Hiatco, the Annfield Plain based welding company, hit unexpected technical problems, expert help from TWI via a North East regional project came up with the solution.Hiatco specialises in welding aluminium and stainless steel for products such as access platforms, ladders and roof racks. Its welders must regularly pass 'approval' tests to confirm their competence to carry out particular tasks.
Recently, when the welders took their approval test on joining aluminium alloy pipe in a butt joint, they failed because x-ray inspection revealed unacceptable porosity - bubbles caused by trapped gas in the welds which would weaken the joints. Exactly similar tests had previously been completed successfully, and so with no obvious reason for failure, Hiatco's welding supervisor Michael Errington called on TWI for advice.
| Welding of fabricated 'T' to 20" diameter spiral welded aluminium tube |
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One of TWI's team of welding engineers, Geoff Eames, took up the challenge and began a series of checks and trials to find the cause of the problem. The welders were using the tungsten inert gas (TIG) arc welding process, which involves a shield of argon to protect the molten weld metal from the air.
Geoff therefore thoroughly checked the equipment and the purity of the gas, before starting to make some trial welds. These demonstrated the importance of completing all weld passes without allowing the pipes to cool, and showed that it was crucial to select an appropriate water based degreasing agent.
As a result Geoff was able to advise Hiatco of the methods to adopt to produce welds of suitable quality. With the problem solved, the company's welders were once more appropriately qualified for a full range of welding tasks.
TWI's help was available to Hiatco under the Joining Forces North East technology transfer programme.
Joining Forces North East aims to boost growth, competitiveness and innovation in the region's small and medium sized companies. For more information and how your company can benefit, contact - TWI (Technology Centre) North East on 01642 210512 or e-mail: sarah.welch@twi.co.uk.
