Shot blasting equipment: purpose, types, characteristics
Contents
1. Shot blast Cleaning - General Information
2. Factors affecting blast cleaning efficiency
4. Types of shot blasting equipment
4.1.Batch-type Tumble Blasters
4.2. Hook Type Shot Blasting Cleaning Machines
4.3. Rotary Table Shot Blasting Cleaning Machines
4.4. Roller conveyor Shot Blasting Cleaning Machines
4.5. Pipe Cleaning Shot Blasting Machines
4.6. Welded Steel Structure Shot Blasting Machines
7. Main components of shot blasting machines
Shot blast Cleaning - General Information
The philosophy of shot blasting is that the surface to be cleaned is affected by a plume of shot. The shot is blown on the surface of the product accelerated up to 100 m/s in the shot blasting apparatus. The purpose of shot blasting is to clean the metal from scale, rust, old paint and to make the surface of the desired roughness. Shot blasting can also be used for surface hardening - peening.
Another way to clean metal is with compressed air. Shot blast cleaning with compressed air under high pressure may be less productive than shot blasting delivered under the action of centrifugal force, but it finds its application if it is necessary to clean large-sized products or hard-to-reach areas.
Cast or grit shot, fused corundum, etc. can be used as abrasive media.
Purpose of shot blast cleaning:
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Removal of rust, scale, other foreign layers;
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Removal of paint and varnish coatings;
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Making the surface of the required roughness, preparing the surface for painting or insulating coating;
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Peening - to harden the product surface;
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Decorative surface treatment.
Factors affecting blast cleaning efficiency
The effective operation of shot blasting machines depends on the following factors:
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The intensity of the shot blast feed;
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Type of a blast abrasive;
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Size of the abrasive;
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The direction of abrasive flow, width and size of the blast plume;
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The condition of the shot blasting machine parts (wear and tear).
Choice of equipment
The choice of shot blast cleaning equipment depends on the following factors:
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Cleaning capacity;
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Product configuration and weight;
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The ability to rotate the product;
Types of shot blasting equipment
Batch-type Tumble Blasters
Tumble blasters are used for cleaning small and medium-sized workpieces.
The products are rolled during the blasting process.
Hook Type Shot Blasting Cleaning Machines
Hook type shot blasting cleaning machines can be used for cleaning medium-sized parts (cleaning on the herringbone fixture) as well as large-sized parts.
The required configuration of the shot blasting machine is determined depending on the characteristics of the products to be blasted, the required productivity, and the production environment of the Customer.
Design options
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dead-end;
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pass-through;
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with Y-rails;
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with closed conveying system.
Rotary Table Shot Blasting Cleaning Machines
Rotary table shot blasting cleaning machines come in a variety of sizes from 1000 mm to 3500 mm. The rotary table shot blast chamber is a versatile solution for production facilities where high productivity is not required. Processing on the rotary table allows for cleaning both large and small products with complex configurations. In case of need for additional cleaning of shadow areas, a worker can blast manually (inside the chamber).
Roller conveyor Shot Blasting Cleaning Machines
Roller conveyor shot blasting cleaning machines are mainly used for cleaning sheet and profile metal products. The roller conveyor system in combination with transverse conveyors (transfers) make it possible to combine such production operations as shot blast cleaning, preservation, measured cutting and drilling into a single unit.
Pipe Cleaning Shot Blasting Machines
Pipe cleaning shot blasting machines are used in lines for applying various types of insulation coatings to pipes.
The shot blasting machine cleans the outer surface from dirt, rust and scale to cleaning degree 2 (PSA 2 1/2 ISO 8501-2).
The pipes are conveyed by a transport system in a rotating and reciprocating manner into the joint, one after another through the chamber where they are cleaned.
Welded Steel Structure Shot Blasting Machines
The metal structures can be fed through shot blasting chamber either by roller conveyor or on a trolley (the trolley consists of two sections connected to each other). The arrangement of shot blasting machines allows for cleaning of complex metal structures from all sides. End surfaces, stiffening ribs and weld seams can be cleaned.
Blast room
The operating principle of blast rooms is based on the use of high velocity shot flow forced by compressed air.
Shot blast cleaning with compressed air under high pressure may be less productive than shot blasting delivered under the action of centrifugal force, but it is used when large-sized products need to be cleaned (e.g. when cleaning railway wagons, large-sized welded metal structures, when hard-to-reach areas need to be cleaned).
Air cleanup system
The air cleanup system consists of a filter unit, radial fan, air ducts, service platform and ensures removal of dusty air from the working chamber, its cleaning and emission into the atmosphere. Shaking of cartridges from dust is performed by supplying a short-term pulse of compressed air into the cartridge. This way the dust accumulated on the cartridge falls into the dust collection container, and the air filtration process does not stop.
Main components of shot blasting machines
The elevator is designed for vertical conveying of the shot and dust mixture to the separator. The spent shot enters the elevator from the silo part of the chamber. The elevator belt is driven by an electric motor, which is mounted on top of the elevator. A platform is provided for maintenance of the elevator belt drive motor.
The separator is designed for separation of shot from dust and foreign objects. The type of separator is air-mechanical. The separator consists of a detachable housing with covers, technological nozzles, a screw conveyor and a gear motor. The shot-dust mixture enters the separator through the feeding chute and is moved by a screw along the housing. At the same time, the shot falls through the adjustable slot into the blowing zone, where the air flow captures dust and small inclusions, and clean shot falls into the storage hopper. The separator separates the shot from dust and foreign matter (scale, dirt, etc.). The coarse inclusions are directed through a hose to the waste container.
The storage hopper is designed to ensure uninterrupted operation of shot blasting machines. Sector gates are designed to cut off the shot flow. Pneumatic cylinders are used as a power drive in the gates. Air is supplied to the pneumatic cylinders dried and cleaned. In the lower part of the hopper there is a tray with spigots for connecting shot pipelines. To prevent the ingress of large inclusions into the shot circulation system, a mesh is installed in the silo.
The screw conveyor is designed to move the shot-dust mixture from under the chamber to the elevator and consists of a welded screw mounted on bearing supports, a gear motor and a housing.
For maintenance of shot blasting apparatuses, elevator, separator, the installation has service platforms with ladders and guardrails providing free and safe access to all mechanisms and units of the machine.