Brompton Bicycle: future-proofing the air supply to a titanium frame shop

Why a fixed speed compressor with the inverter already fitted was the right answer for the shotblast cabin behind Brompton’s T Line frames.

The Atlas Copco GA22 FLX FF and air receiver installed at the titanium frame facility in Sheffield

At a glance

The customer

Brompton Bicycle is the largest bicycle manufacturer in the UK and the company behind the folding bike that Andrew Ritchie first designed in the mid 1970s. Most Bromptons are built at the company’s factory in Greenford, west London, where a high proportion of components are made in house and the majority of output is exported.

Titanium is handled separately. Working it calls for different skills, machinery and processes from steel, so Brompton built a dedicated facility in partnership with the long established Sheffield precision engineer C W Fletcher, housed within Fletcher’s Sterling Works site. Frames for the T Line, Brompton’s lightest bike, are precision engineered and hand welded there before travelling south to London for final assembly. The shotblasting unit this compressor feeds is part of that titanium frame process.

The challenge

The frame shop needed a dedicated compressed air supply for an Acton DP12/14 shotblasting unit working on titanium frames. Shotblasting is an unforgiving duty. Demand is high and near continuous while the operator is in the cabin, and any moisture or oil carry over in the air stream shows up immediately in surface finish quality. On a hand welded titanium frame that is going out on a finished bike, the finish is the product.

The two operating points sat a long way apart: a 6 mm nozzle draws around 80 cfm, an 8 mm nozzle 142.6 cfm at 6 bar. Brompton also wanted the freedom to experiment with nozzle size and working pressure to find the best finish and cycle time, rather than being locked to one configuration on day one. So the requirement went beyond simply matching the blaster. It was to deliver Grade 4 air or better at 6 bar nominal at the point of use, with enough headroom and adjustability for the process to be tuned, and without over sizing the plant for a duty running 1,500 to 2,000 hours a year.

The thinking behind the specification

A single blaster duty at these hours would, on paper, point straight at a fixed speed machine. Fixed speed is the efficient answer when the load profile is flat and predictable, and it avoids paying for variable speed hardware that a steady duty never exercises.

That reasoning only holds while the profile stays flat, and manufacturing sites rarely stand still. Add a second blast cabin, drop to smaller nozzles, or bring a paint plant into the building, and demand becomes variable. At that point fixed speed stops being the efficient choice and a variable speed drive begins paying for itself.

The GA22 FLX FF answers both cases. It runs as a dual speed fixed speed machine, which suits the current single blaster duty, while the inverter is already physically installed in the machine. Should Brompton’s air profile change, the VSD functionality is unlocked by licence. There is no new compressor to buy, no re-piping, and no need to dispose of an asset part way through its life.

The decision to move to VSD has been separated from the decision to buy a compressor. Brompton have the right machine for the duty they run today, and the cheaper route to variable speed if that duty changes.

The installation

The system was configured with a 7 bar setpoint and a tight 0.3 bar cut in and cut out differential to draw maximum output from the machine, with pressure adjustable between 7 and 8 bar so Brompton can trial nozzle and pressure combinations, and system pressure limited to 12 bar by the receiver safety valve. At 160 cfm the compressor covers the 142.6 cfm worst case with headroom rather than running flat out against it, and on the 6 mm nozzle duty the dual speed control drops to its lower speed rather than holding full speed against a part load.

Aftercare

Brompton took the Guardian Plus 7-year service plan. It carries all service spares, all breakdown spares, breakdown labour within normal working hours and Smartlink Uptime monitoring, and it brings with it the free 7-year extended warranty on the compressor. The plan price is fixed for the whole seven years, so the cost of keeping the machine running is a single known line in the budget, and there is no contract to sign and no cancellation penalty. Run hours are reviewed annually against service records so the maintenance regime stays matched to actual use.

Nine weeks in

The compressor has now been in service for nine weeks supporting the shotblaster and is performing to specification. Air quality and pressure at the nozzle have been stable across both nozzle sizes, and Brompton have the adjustability they asked for to keep refining the blast process. The client has told us they are delighted with the installation.

The takeaway

Brompton bought a compressor for one shotblaster. They also bought the ability to run two blasters on smaller nozzles, or add a paint plant, or change the shift pattern, for the cost of a licence rather than a second compressor.

William G Search Limited

Market Works, Whitehall Road, Leeds, LS12 6EP

Tel 0113 263 9081 · air@wgsearch.co.uk · www.compressive.co.uk

Paul Newsholme, Sales Manager
paul.newsholme@wgsearch.co.uk
07771 708255

Ref PN/AMF/Q22395A