As the components are initially sand cast and then resin polished prior to electroplating, the design of the cleaning and pre-treatment leg of the twin parallel plant with a cross transfer had to be carefully considered to remove the polishing compound and sand debris. In addition to the twin soak and electro cleaning, there is ultrasonic cleaning and vertical agitation within all the cleaning processes, which also incorporate pumped turbo flow eductor agitation systems.
The components are firstly nickel plated and then cross transferred into the second leg for bright chrome plating and post treatment. Because of the high production volumes, an expansion transporter was developed which allows two flight bars to be processed simultaneously, with expansion to the plating centres and contraction to the compacted form for all other metal finishing operations.
The process incorporates two fume extraction systems to atmosphere, one dedicated to the removal of vapours from the chromium process tanks and one for the removal of composite acid and alkaline processes. In each case, the extraction systems are directed through twin phase fume scrubbers with low velocity discharge stacks to atmosphere. Because of the close proximity of an adjacent housing estate, these are supplied complete with attenuators.
Significantly, all heating applications within the application are provided by a thermal fluid distribution system, with duty and stand-by gas-fired boilers.
The process uses a lot of rinse water simply because of the high volume of parts that pass through the plating lines. There are two plating lines, and because these are brand new systems, segregation is used. Rinse waters move through ion exchange equipment, to reduce the amount of liquid that is sent to foul sewer – and to recirculate as much water as possible.
One of the challenges faced was that of a very low discharge limit. Following the ion exchange regeneration, the decision was taken to install an evaporator in which the regenerant – the concentrated waste – has much of its water content boiled the off. As chemicals like hydrochloric acid are also being boiled, the evaporator is a specialist piece of equipment, constructed of titanium and designed to cope with corrosive chemistries. However, it is an outcome that reduces by half the amount that would have been sent to total loss effluent treatment plant – an elegant solution.