Magstream-p - case studies


Courtesy of Fluid Dynamics International Ltd

HDL Magnetic scale preventers enhance quality and cut costs at jaguar

Installed HDL unit in phosphate spray pipework in Dec 1988

Before     2x 2000 gals tankers removed sludge every six weeks
Now     One tanker every 12 weeks is more than enough
Before     Jets blocked
Now     jets stay clean producing more consistent and uniform coating, improved control achieved - proven statistical analysis of phosphate weights on body
    Installed second HDL unit to heat exchanger pipework
Now     Significant improvement in control of phosphate temperature 50+- 2oC a critical process parameter

Hoover universal (UK) TD Leigh-On-Sea, Essex

Metal pretreatment plant 7 stages iron phosphate (ici):

Practical examples

Beford plant *Luton)

Treatment of rinse water in Bedford Van body metal pre-treatment plant. Installation of magnetic unit hard water rinse system following alkali rinse bath.

Resulted in removal of calcium phosphate / Calcium carbonate scale 6-8mm thick from wall of tank 163Cu meters capacity. Scale estimated to weigh 1.25 tonnes.

Estimated annual savings: £22,000 (acid cleaner now longer necessary)

Practical examples

Motor Industry Metal Pre - Treatment Plants

Whether the design of a pre-treatment plant is spray, dip, or full immersion, an inevitable and undesired consequence in the process is the formation of a light solid or sludge.  This is a by-product and it has a tendency to attach itself to  surfaces, gradually building up.  the inner layer of the sludge accumulation becomes denser and increasingly difficult to remove.  Further more, with all pre-treatment processes being water based, the problem of scaling is frequently manifest throughout pipework, and particularly affect heat exchanger and spraying regions.

IBC Vehicles and Vauxhall Motors

At the IBC van plant in Luton, the problem was compounded by excessively hard water from bore wells.  In the degrease zone, water was supplied to dip tank spray rings, and drawn through a plate heat exchanger to maintain temperature at up to 60'C.  Scale build up was reducing heat exchanger efficiency, causing spray nozzel blockages, and was forming a cooling on the interior of the dip tank.  To maintain high quality standards in the end product, the tanks were cleaned twice a year with chemicals at a considerable cost.

HDL scale preventers were fitted to the pipe runs of the degrease heat exchanger and the 'Rinse 1' tank.  The latter tank, with a capacity of 100m3, posed a considerable test for the HDL unit, as a deposit of hard scale of between 6 mm and 19 mm had built up on the tank walls, an indication of the high calcium carbonate content of the process water.  The heat exchanger was operating satisfactorily for two or three times  longer between acid cleaning, but according to process engineering sources 'the most starting revelation was in Rinse 1'.

Every fortnight the tanks were put to drain, washed out and refilled with fresh process water.  The fast time the tanks were emptied after fitment of the HDL unit scale preventers, an area of stainless steel measuring 2 meters in diameter was revealed, completely free of scale deposit.  Two weeks later the clean area had spread to both ends of the tank, and after eight weeks all scale on the tank walls was 'loose and fluffy' and could be washed down with hose.

Following the experience with HDL scale prevention units at the associate van manufacturing plant, Vauxhall fitted units on the new pre-treatment plants at Luton and at Ellesmere Port.

At Luton, an HDL unit was fitted on the Rinse 1 tank as at IBC Vehicles, but not the degreaser because this used a tube type heat exchanger that was not prone to scaling.  in the phosphate tank, the process department at Vauxhall thought it might be possible to reduce jet and pipe blockages caused by sludge.  By reference to its own laboratory work and academic research.  HDL was able to advise that neither the morphology more lay-down characteristic of the protective phosphate layers on the pre-treatment steel would be affected by the scale prevention unit.  Vauxhall obtained information of this form its chemical suppliers.

Two of HDL's units subsequently, fitted to the heat exchanger, under-surface agitation system and sprays of the phosphate plant.  Capacity of the heat exchanger was increased at the same time, to reduce the interface temperature (that is the temperature difference between hot water entering the heat exchanger and that of the bath) from 40'C to 15'C.  The acid cleaning requirement was reduced from once every two or three weeks to just four times a year and jet and duct blockages went down by an estimated 80 per cent.

In addition to the savings in chemicals, maintenance costs have been lowered and energy usage is more effective.

Practical examples

Jaguar Cars

At Jaguar, the fitting of HDL magnetic scale preventers in the metal pre-treatment plant has enabled the company to enhance quality by giving a more consistent and uniforms appearance to the phosphate coating on car bodies.  At the same time, the consumption of chemicals has also been reduced.

Jaguar installed an HDL unit to the phosphate spray circuitry.  As a result, the length of time between cleaning and plant and in removing the sludge had more than doubled.  Previously, two 900 litre tankers were required to remove sludge every six weeks.  After fitting the magnetic scale preventers, Jaguar report there is barely enough sludge to justify one tanker every twelve weeks.

In addition, pipework which required caustic cleaning due to the drastic reduction in bore size as a result of layered encrustment of precipitant, has stayed relatively clean.  The HDL units prevent crystalline formation on the inside of the pipes by retaining the sludge in suspension where Jaguar's vacuum filtration plant can easily remove it.

The jets which spray the phosphate on to the car bodies also remained clearer giving a more consistent and uniforms appearance to the coating.  Jaguar carries out a statistical analysis of phosphate coating weights daily on each shift.  In the three months period following the installation of the HDL units improved control has been achieved.

The company installed a second HDL unit into the heat exchanger unit.  A significant improvement in the control of phosphate temperature, a critical process parameter of 50+2'C, has resulted.

Practical examples

Hoover university (Uk) LTD Leigh-on-Sea, Essex

Metal pretreatment plant 7 stages iron phophate (ICI).

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