in Vol. 13 - September Issue - Year 2012
Effective Blasting And Painting Of Steel Sections And Constructions
Roller conveyor shot blasting plant (AGTOS) and blastroom (SLF)
Entry side of the roller conveyor shot blasting plant (AGTOS)
Blasted section on the outlet roller conveyor (AGTOS)
View of the open-space paint spray system with telescopic dryer (SLF)
View into the blastroom (SLF)
One of the long-flow nozzles of the open-space paint spray system (SLF)
Located in the north of Germany, Schone & Bruns manufactures supporting frames, pipeline bridges and special designs for clients in the fields of the chemical industry, petro-chemistry and power station construction. For the coating of sections and constructions, the company invested in a new blasting and painting machine. Recently , they started running a blasting and painting line with a coating capacity of 12.000 tons of steel per year.
The Managing Director Carsten Bruns explains: "The existing coating technology was the bottle neck since we could neither coat the necessary amounts nor achieve the necessary quality. We had to have the work pieces coated externally and time and again encountered problems such as disturbances of the production flow and difficulties in meeting the delivery dates." This is why it was decided to buy property and build a completely new site.
The requirement specifications included requirements regarding the highest possible functionality, conceptual design as a self-contained process, compliance with the amount to be invested, low operating costs and compliance with the legal stipulations. In April 2011, construction work began, and by May 2012, Schone & Bruns started trial operations.
The sections and steel constructions to be coated first pass through the mechanical pretreatment process, for which two blasting chambers are available: an automatic roller conveyor shot blasting plant as well as a blastroom for the manual pretreatment. Depending on the dimensions of the work pieces, the decision is made in which chamber the pieces are treated. The continuous shot blasting plant (AGTOS) is designed for work pieces and constructions up to a width of 2.600 mm, a height of 1.400 mm and a length of 15.000 mm. The minimum work piece length is 1.200 mm; smaller pieces need to be placed on gratings for blasting. The transport of the work pieces is effected by a roller conveyor whose gear motor is infinitely variable.
To make sure that blasting only takes place when work pieces are in the blasting zone, the work pieces activate a switch unit situated in front of the inlet sluice. The sluice itself is sealed with wear-resistant rubber curtains towards the inlet and furnished with rubber lamella sealings on the bottom. The blast chamber is made from highly wear-resistant manganese steel and is equipped with eight high performance turbines. Their alignment and inclination ensures that the work pieces are cleaned in a reliable manner.
At a passage speed of approx 0,4 to 1,5 m/min, the cleaning level B Sa 2,5 is achieved. This corresponds to a roughness of 30-50 µm. After passing through the blasting zone, the pieces cross the outlet sluice and arrive at the blower unit, where they are cleaned of blasting dust. The abrasive that is collected there and in the blasting chamber is purified and recycled into the abrasive circuit. The abrasive collection hopper can hold up to 8 tons of which approximately 1.800 kg/min are fed into the circuit by means of an electro-pneumatic dosing device.
After the blasting process, the pieces are tested for the quality of the roughness and the degree of cleanness. Smaller parts are painted in a separate tunnel machine.
After the blasting process, sections and constructions are transported to two open-space paint spray systems (SLF), 15 m long and 8 m wide, by means of a hall crane. This machine technology enables painting in an open space without restricting cabin walls. The ventilation of the paint systems is effected through sectional ventilation technology by means of dual-stream long-flow nozzles installed in the hall ceiling.
A special feature is the type of forced paint drying. "It happens by means of a telescopic dryer that is placed onto the paint station using an embedded rail system in the ground of the production hall."
If the dryer is extended, it reaches a maximum length of 15.400 mm. If it is not needed, it can be reduced to a space-saving length of 5.800 mm and can be parked in front of the painting station.
"With the help of the telescopic dryer, the drying and handling time can be significantly reduced."
The whole machine is trend-setting regarding productivity, ecology and profitability. It is operated by ten operators in two shifts.
Gesellschaft für technische
48282 Emsdetten, Germany