Stadco Ltd, Shrewsbury

Stadco Cooling were approached to supply and install air blast radiator systems to cool the state-of-the-art welding equipment on Stadco Ltd's body-in-white assembly lines at Nanjing Automotive's (NAC) MG assembly facility in Longbridge.

Objective

• To cool various welding machines, 87 hand held and 9 pedestal.
• To dissipate 231 kW when cooling 1,070 1/min water from 33°C to 30°C, in a design ambient of 26°C dry bulb solution

Customised dedicated sealed and pressurised closed circuit water cooling system

The cooling system was designed so that the coolant, in this case water, is continuously recirculated to avoid water loss and eliminate water costs.

Because the water cooling system is sealed, all air is eliminated soon after the system is charged. The internal pipe work surfaces and the narrow cooling water passageways in the robots, welding guns, heaters and transformers would no longer be subject to the build up of lime scale and corrosion.

Hot water from the equipment to be cooled is pumped through a matrix of extended surface area tubes to maximise efficiency. Cool ambient air is induced (or drawn) across the cooling matrix of the air blast radiator and is exhausted without any contact between the air and the water.

Cooled uncontaminated water is then returned to the equipment to be cooled. Hot process water is drawn through a sealed pump module into an oxygen removal system. Any entrained air is automatically separated from the fluid physically and it is then expelled from the unit without the fluid contacting the atmosphere.

The fluid passes an orifice of the system expansion facility where the required expansion or contraction is accommodated. A safety valve is fitted to release any excessive pressure. Water is drawn into either of two pumps (one as a standby). The pump creates a system flow at an appropriate pressure to compensate for the total process water system pressure drop.

A separate initial fill facility is fitted which automatically compensates for any minor system losses. An electrical control cabinet was also included to accommodate basic manual switching control at the end of the range up to fully automatic control systems at the other.

The system comprised:

• Air blast radiator 210/3, having 10 x 1.3kW fans drawing air over EPOXY COATED aluminium finned copper tubes. Fitted with five fan control thermostats and 10 fan motor isolators, complete with extended legs. The noise levels are approximately 60dBA at 10 metres and 72dBA at 1 metre.
• Sealed dual pump module 1500-D, fitted with two 22.0 kW pumps (1 duty, standby). Each pump rated to deliver the required system flow rate at a pressure differential of 6.0 bar measured at the pump. Complete with auto-changeover via timer and common fault circuit.
• Fitted to the pump module was a Pressurisation Set for initial fill/make-up, comprising a mains break tank with type A air gap, complying with bylaw 30, pump, expansion tank, pressure switch, pressure reducing valve and safety valve. Make up is controlled by means of a solenoid valve controlled by a level switch.
• Electrical control cabinet.
• Frost protection (immersion heater 24 kW)

Result

• Reduction in operating costs
• Improved performance
• Significant reduction of downtime for servicing and/or maintenance purposes
• Improved reliability – sediment free water
• Water conservation as evaporation of water does not occur
• Reduction in corrosion
• Elimination of limescale
• Reduction in maintenance costs
• Health risk reduction
• Low sound levels