The Al Sarif Group is famous as a leader in infrastructure projects in Saudi Arabia. To continue to earn the confidence of its customers, SCBM has set itself the task of driving quality forward through continuous improvements and product diversification. With a new shotblasting and curling line, Al Sarif is well equipped to meet the latest quality standards in the modern building materials industry. The new finishing line was supplied and installed by SR SCHINDLER as the 1st phase of an ambitious investment plan to produce “world-class premium pavers and tiles.”  

Finishing line supplied by SR Schindler 

A shotblasting unit removes the cement from the product surface, exposing the aggregates in paving stones and concrete slabs. The products are machined on the face side. Shotblasting machines are operated with steel or stainless steel blasting materials. In operation, the steel or stainless steel balls, standard size 0.6–0.8 mm, get thrown using turbines at the products to be shotblasted. 

The blasting speed and belt speed are adjustable depending on the treated product and the desired surface appearance. The turbine and belt drive is frequency-controlled for a homogeneous treatment from rough to fine. 

SR-1250 shotblasting unit 

A type SR-1250 shotblasting unit is supplied by the German plant manufacturer, SR Schindler, to finish the surface of concrete products. The SR-1250 shotblasting unit processes layers with dimensions between 800 x 800 mm and 1,200 x 1,200 mm. Layers with a side length of more than 1,200 mm are rotated by 90° and then transported with the shorter side at right angles to the direction of movement so that these layers can also be processed in the shotblasting unit. The maximum product thickness is 200 mm. 

The finished stone packages are set down on the 11.70-m-long heavy-duty conveyor with a frequency-controlled drive. The parcels are transported to the LPU stacker with a four-sided electromechanical clamp. The running gear of the LPU is also equipped with an electrical industry. At the same time, an electromotive rotary device allows the layers to be individually positioned on the shotblasting unit’s rubber conveyor belt before the infeed entrance lock. The rubber conveyor belt is ribbed at right angles to the direction of movement, which prevents the product layers from drifting apart during finishing. 

The shotblasting chamber is made of 12 % austenitic manganese steel to protect against damage and wear from the blasting process. In the shotblasting section, two frequency-controlled turbines, each with an output of 18.5 kW, blast the surfaces of the layer positioned below with small steel or stainless steel balls. This exposes the aggregates in the facing layer of the concrete products, and they are given a refined and aesthetic surface finish. Another effect of the shotblasting process is the much-improved slip resistance due to the acquired roughness of the surface. 

The blasting material's throughput is approx—240 kg per minute and turbine. The dosing amount of blasting material can be regulated electro-pneumatically. 

Once the blasting process has finished for a layer, this is transported out of the shotblasting chamber, and a new layer is positioned in the room. The shotblasting process is automatically stopped while the layer is being changed and only starts up again as soon as the next stone layer is in the correct position in the chamber. 

In the following cleaning chamber, two high-pressure blowers with height-adjustable slot nozzles remove the blasting material from the surface of the processed concrete products. The contaminated blasting material is collected, and dirt particles are removed from it in a cleaning unit. It is then made available for the shotblasting process again in the blasting material silo. 

Curling unit CA 1200

A layer pusher with a transfer table transports the freshly shotblasted products in an endless row into the CA 1200 curling unit, also supplied by SR Schindler. 

Curling is particularly well suited for textured products but also gives a slight shine and exclusive surfaces to roughened and/or shotblasted products. By removing surplus cement, the aggregates in the stone are presented in detail and polished by the brushes. This makes the product surfaces dirt-repellent and non-slip. 

The main drives and vertical movement are frequency controlled. The machine has a control system with an operating panel and display. The processing parameters can be saved for each product type. 

The endless row of products is pulled apart on a downstream accumulating roller conveyor with free-running rollers. At this point, a visual inspection takes place. Products that do not meet the quality standards can be sorted out here manually and replaced with flawless products by hand. The following layer pusher transports the finished stone layers onto the subsequent belt conveyor. A second LPU layer stacker with the identical design to the first-mentioned stacker takes the finished stones from the belt conveyor one layer at a time and stacks the layers on the heavy-duty roller conveyor arranged parallel to it onto transport pallets that are fed automatically. Once the desired stack height has been reached, the stone packages are transported into the buffer area to be taken away by a forklift truck.