BAE Systems employs lean manufacturing to build Astute submarines
E&T visits BAE systems in Barrow-in-Furness, birthplace of the Astute class submarines.
Submarine construction is in the waters at Barrow-in-Furness, location of the BAE Systems site that launched the Holland One 110 years ago. But the new Astute class of submarines being built for the Royal Navy has challenged that century-long manufacturing proficiency to the full.
At 97m long and displacing 7,400t, the Astute class is certainly impressive, but the Devonshire Dock Hall is more than capable of hosting its manufacture. The 268m-long facility, opened 25 years ago by then Prime Minister Margaret Thatcher, can house two subs and a frigate together, and it remains the hub of the manufacturing operation.
Astute-class subs are manufactured in seven pieces at the Bridge Road facility in Barrow, before making the half-mile trip to the DDH for assembly, and finally moving into the water aided by a 162m shiplift.
'Submarines are enormously complicated, with a unique range of materials and technologies,' says John Hudson, managing director of submarine solutions at BAE Systems. 'I can't think of a single man-made product that has the diversity of materials, systems, arrangements.
'We have to embrace a huge range of manufacturing technologies. Our facility is based on lean principles; I think some of the technologies such as six sigma are difficult for us because we are very low-volume manufacture. We are trying to integrate manufacturing and fabrication with some quite high-end engineering craftsmanship covering machine surfaces and tolerances.'
It is within the manufacturing operations at Barrow that much of the innovation is taking place. 'I don't think anyone can avoid where we are as a nation and defence spending is hugely challenged,' Hudson adds. 'I would say now that our biggest driver is actually affordability. I think UK defence products are still capable, The Astute class is a very capable submarine. It has the usual aspects of submarines that one would expect; it's got exceptional sonar, it's got an exceptionally quiet signature so it makes it a world class submarine. But we have to do that in a way that drives cost down. We are using more commercial off-the-shelf materials and processes to deliver that military effect. Affordability is probably the single biggest driver of what we do.
'If you go back to Nelson and back to the middle of the last century, the naval sector drove industry. The materials and manufacturing technology came from the naval sector. The first attempt at volume manufacturing was tackle blocks for naval frigates: the first mass-produced item that was used by anyone in the world was driven by naval technology. A lot of the high-tensile steels were driven by naval technology. A lot of the analysis techniques that we use in industry were driven by naval technology.'
However, despite that pioneering heritage from the naval sector there has been a fundamental shift, with the commercial world now leading the defence industry in innovation. It can be argued that the continued drive to reduce costs allied with the safety-first approach required for submarines has put a brake on innovation and to some extent Hudson agrees with that, but still points to ways that the product and manufacturing process is innovative.
'I think that the submarine environment is a very, very difficult environment: it's safety critical, so there is a natural degree of conservatism,' he explains. 'If you've ever been hundreds of metres beneath the surface in a pressure vessel in a dynamic vehicle you'll understand why we need to be very safety-conscious and that drives a degree of conservatism. Within that, though, I think we are able to offer innovative solutions particularly around the combat systems.
'We have done quite a lot of work to make the combat systems more capable. A lot of our innovations are about taking cost out which is actually not about technology. It's about how we do what we are trying to do but in a more cost-effective way.'
For innovation he singles out a device called a low-pressure blower, which, when the submarine is on the surface, is used to blow air into the tanks. 'That's quite an expensive piece of equipment and we were looking at how we could make that equipment cheaper and more operable to the navy,' he says. 'We surveyed what was happening in industry and found there was a grain blower technology that uses an air blower to blow grain into silos and we were able to take that piece of technology and to incorporate it and to make some very modest changes and bring that into the submarine environment.'
From drawing board to deep blue sea
The development of a submarine such as the Astute class can broadly be broken down into four processes: concept; functional design; spatial design; and manufacturing. Innovation starts on the drawing board, or more accurately the CAD system, and despite the unique tendering process for military procurement, that remains the same for submarines. It begins with what Hudson describes as a broad dialogue with the customer that sets out the baseline specifications. This covers criteria such as speed, length of patrol, how quiet it has to be, what its military effect is going to be and how many reloads it requires.
After assessing these requirements the engineering team starts to turn that into a concept for the design of a submarine. 'We look at the primary aspirations that the customer has and then there are always those little things that are just evolution,' Hudson explains. 'We may want to improve the habitability standard for the crew because when you go on board it's pretty sparse. If we are designing a submarine now, it's going to be operational in the 2030s; probably the submariners in that time will want slightly better accommodation.
'Then, with all of that analysis, the Ministry will look at different options that we have prepared for. So that requirement will cost you that and will take this long to deliver and this requirement will cost you this and take this long. Then the government will go in and analyse those.'
The Astute class was a slightly different case, because it was a competition. The Ministry went to industry and said 'this is the requirement, now go and cost it'.
'Astute was pretty complicated because it had a pre-contract concept phase,' Hudson says. 'With Astute we did the concept stage and they fixed the requirement and then they went to industry and asked for the cheapest way to meet those requirements.'
With the concept accepted the process moves into stage one design, which is the functional design. 'This is the time when we design such things as how many pumps we will have in the hydraulics system or how many accumulators there will be. When we have completed the functional design of the system we are able to write all the technical specifications for all of the equipment.
'Then we move from the functional design into the spatial design where we integrate it physically. Where is the start button? Where is the valve? How is a man going to maintain that filter? How do you lay the submarine out? How do you get from one end of the submarine to the other? All of this is part of the spatial layout phase and this takes place in a CAD environment.'
With the layout locked in, the process moves on to adding intelligence into the design; incorporating part-numbering, understanding the sequence of build, producing all of the manufacturing information and the tolerance machining and delivering all the outputs to the manufacturing team which then starts construction.
Part of the process used to include hand-crafting beautiful full-size wooden models of the entire ship, but sadly the use of CAD has largely consigned that art to the realms of history. In very select areas it is still necessary to produce a physical mock-up. One example is the ship control console: where the person who is going to physically operate the submarine will sit.
'Where he sits and controls the hydroplanes, we will physically mock it up so he can sit there and press buttons. For example, Astute has a joystick to control it. It is a tiny little joystick operated by the left hand and it's next to the bulkhead. There are two operators, the guy who drives the submarine and the panel operator next to him. We decided to put the control to the left and have it left-hand-operated so there is no chance that somebody could knock his hand.
'Most of it is done in a visual mock-up. We will have a CAD representation of it. You can walk through it and you can reach things. You have mannequins to see if they can reach things so we can simulate the submarine.'
There will be seven Astute class submarines by the time the programme reaches its conclusion. The first, HMS Astute, was launched four years ago, the second, HMS Ambush, is in the water going through final fit-out, while the third and fourth boats, HMS Artful and Audacious wait patiently in the manufacturing hall. *
Welding the Astute class
The pressure hull on an Astute submarine is made up of eight sections, or units, and each one of these typically comprises three separate pieces of flat steel, which are formed to make a cylinder shape.
It is at this stage that these three plates are manually welded together – a process which takes place when the unit is in an upright position, rather than horizontal. Each join has one welder assigned to it, working simultaneously with the others.
The edges of the pieces of steel are cut in a wedge shape, so that when each is brought together with another it forms a deep groove for the weld to fill. Before the welding can begin, the steel needs to be heated using strip heaters, which enables a more effective weld.
The first weld takes place on the outer face of the unit, and to assist this process a ceramic rod is wedged behind, which acts as a guide for the welder to follow as he completes his first run, known as the 'route run'. A second run, known as the 'hot pass', follows, and secures the plates of steel in place, before a number of subsequent runs, or 'beads' are gradually welded on top of each other.
When the outer weld is halfway complete, the ceramic rod is chipped away, and the area gouged out so that welding can begin on the interior joins. The same process is then followed until the beads of weld fill the join, before a final 'capping run' is applied – ensuring there is sufficient excess for a grinder to leave a completely smooth finish between the weld and the steel. Throughout the entire process, the unit is regularly checked by each welder, as well as a dimensional-control team to make sure the unit retains its shape.
At the end of the weld, the unit is left to cool before undergoing rigorous inspection, known as non-destructive examination (NDE). This takes the form of both visual inspection, and deep ultra-sonic testing, to guard against any defects. From start to finish the entire process can take up to two weeks.
The only exception to the above method is when the forward and aft domes of the pressure hull are welded to a unit – this takes place horizontally and is fully welded from the inside before being back gouged.
When two pressure hull units are ready to be welded, they are brought together within a matter of millimetres of each other in a horizontal position. The welding process is again performed manually, involving a team of four working simultaneously, each assigned a different quarter. The first job is to secure the two units together with a number of 'block tack' welds, before applying two or three runs from the interior of the hull.
At this point the 'block tacks' are removed and the area gouged out, so that welding can begin on the outer facing joins of the unit. Again, the beads are gradually built up on either side, before a final 'capping run' is applied and grinded to leave a smooth finish. The completed weld is also subject to the same stringent NDE. This entire process can take a number of weeks.
There are a number of challenges facing the welder: when undertaking an interior weld he regularly has to work in confined spaces, and as the steel needs to be heated, the temperature inside the unit in extremely warm – meaning he can only work for a certain period of time before taking a rest to replenish any lost fluids.
The technique employed by the welders is MIG – metal inert gas. As well as their welding gun, they each carry what is known as a welding suitcase, within which is a reel of flux that is heated to form the molten metal. There is a double safeguard to prevent against any atmospheric attack during welding – the first is a protective wire that contains the flux which gradually strips away as the weld is applied, and the second is a shielding gas (comprising argon and CO2).
Facts and figures
- When fully stored Astute will displace 7,400 tonnes of sea water, equivalent to 65 blue whales.
- HMS Astute is 97m long, longer than ten London buses.
- The submarine is fuelled by a nuclear reactor powerful enough to power a city the size of Southampton.
- Armed with Tomahawk cruise missiles, Ambush can strike at targets up to 1,000 km from the coast with pinpoint accuracy ' equivalent to driving from London to Paris and back twice.
- She can circumnavigate the world without surfacing.
- There is around 110 km of cabling and pipe work on board Ambush ' equivalent to driving from Bristol to Oxford.
- Ambush's Sonar 2076 sonar suite has the processing power of 2000 laptop computers. It has the world's largest number of hydrophones, providing the Royal Navy with the 'biggest ears' of any sonar system in service today.
- James Martin had a Pancake Day cook-off with a Royal Navy chef to christen the galley in February 2007 and the Hairy Bikers visited the galley in April 2008 in the search for unusual locations from which to film their cookery programme.
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