PRODUCTION CAPACITIES

Constantly increasing investor demand for shorter delivery times and increasing product quality have motivated OKZ HOLDING to expand its production capacity and invest in modern and thus more efficient production equipment.
Even though the size, variety and uniqueness of our products do not permit full automation of the production processes, OKZ HOLDING makes use of production lines and other equipment increasing both our productivity and the quality of our products. Thanks to innovation and the mechanisation of production, the company has a capacity available to its clients of up to 25,000 t of steel structures and prefabricated elements for storage tanks per year.

The main production processes:

• Surfaces blasting – continuous
  Continuous pass-through machines with roller conveyor LAUCO 2,000 x 600 mm and LAUCO 2,500 x 750 mm, material through speed up to 2.5 m/min
• Drilling and sawing of section steel on automatic systems producing steel structures, VOORTMAN V630/1,000M (2 pcs), maximum profile cross-section 1,000 x 600 mm, line productivity 600 t/month
• Oxyfuel or plasma cutting of sheet metal on NC portal machines, producer ESAB, MGM, Vanad, material thickness 0.5 – 300 mm, maximum lay-out of processed metal sheet is 3,200 x 12,500 mm
• Cutting metal sheets with table saws max. width 3,000 mm, thickness up to 16 mm
• Machine profiles cut by band sawing max. dimension 600 x 1,000 mm
• Preparation of weld edges using a bevel machine thickness range from 4 to 60 mm
• Steel sheet bending (cylinders and cones) thickness up to 65 mm, max. width 3,000 mm, minimum radius is: R = 1,400 mm
• Steel section beam and pipe bending max. section dimensions: PLO = 300 x 70, L 200 x 200 x 20, I 320, TR – DN 300
• Metal sheet bending with CNC press brake 300 t, max. length 4,000 mm
• Conventional turning up to ∅ 1,200 mm, length up to 3,000 mm, max. weight of worked part 3,000 kg
• CNC turning lathe up to Ø 420 mm, length 700 mm
• Conventional milling works with clamping surface 500 x 1,800 mm
• CNC milling with clamping surface 500 x 2,000 mm
• Conventional drilling up to ∅ 50 mm (steel), clamping surface 1,200 x 2,000 mm
• Shot blasting with steel grit – blasting by metal pellets using air pressure machine using different kinds of cast iron, steel in blasting boxes with dimensions from 15 x 5 x 5 m up to 19 x 6 x 6 m, maximum work piece weight 30,000 kg
• Painting – high-pressure and low-pressure spraying painting box type USF OLT with dimensions of protected area 12 x 6 x 6 m and painting and drying box WISTA with protected dimensions of 18 x 6 x 6 m
• Welding machine – inverter and pulsed welding sources and automatic welding machines made by highly respected producers – CLOOS, Fronius, ESAB, Kemppi, Lincoln Electric
• Welding positioners for cylindrical product welding up to ∅ 5,200 mm, max. weight up to 20,000 kg

All production processes are subject to strict technical procedures and instructions.

WELDING METHODS IN PRODUCTION

Welding is an important specialised production process. In our plants, we weld various kinds of metal, starting with unalloyed steel, alloyed and austenitic, up to high-alloy special steel.

These processes are implemented and guaranteed by qualified personnel, using carefully selected welding equipment supplied by a leading industry manufacturer, and following approved welding processes. We use all methods of manual welding – by electrode, MIG, MAG, TIG and flame. In addition, we are continually increasing the percentage of mechanised and automated methods – MIG, MAG, TIG and fully automatic submerged arc
welding.

Quality management of welding processes is guaranteed by certified International Welding Engineers (IWE) and European Welding Technologists (EWT).

The quality of welds is tested using all non-destructive methods available, either internally by OKZ or by external experts.

PROJECT MANAGEMENT

A single project manager is responsible for the implementation of the entire project according to the terms of the contract.

Works are executed in accordance with the time schedule approved by the client. A site manager coordinates work organization and order kept on the construction site.

The construction site equipment and machinery are located according to a plan, which forms a part of the preparatory documentation, and authorised personnel only may control their operation.

All the equipment used for assembly, anticorrosive system applications, and insulation works is owned by OKZ HOLDING.

We also use specialised high-standard assembly fixtures and equipment manufactured in the company design workshop.

A procurement manager cooperates with OKZ HOLDING production plants and controls their supplies of materials.

Quality is verified according to approved internal procedures. Further, quality assurance managers can avail of other quality control personnel and welding engineers, on the construction site.

OCCUPATIONAL HEALTH AND SAFETY

Work safety during production and assembly complies with standards according to OHSAS 18001:1999, internal regulations and relevant decrees, and clients’ explicit requirements.

Each contracted project shall be supervised by an authorised employee. Special safety regulations apply to assembly and welding works in explosion hazard areas.

QUALITY CONTROL AND TESTING

Quality control of welds includes all types of non-destructive tests (NDT), such as visual, vacuum, magnetic, ultrasonic, X-ray and capillary testing.

OKZ HOLDING executes thickness measuring for metal sheets and piping, as well as hardness testing of basic materials.

These services are provided by the subsidiary company Metesta based in Lithuania, which holds all the certificates required for the performance of such activities within the EU.

To control the stability and tightness of storage tanks, in addition tightness hydrostatic tests are carried out.

Both specific function and overall testing are always carried out with theparticipation of the client or the investor, before handing over the project.

Protocols of tests performed constitute a mandatory part of the final documentation.

TECHNOLOGICAL PROCEDURES OF TANKS CONSTRUCTION

The most important thing for large capacity storage tanks construction is the choice of the right technological procedure, a description of which is always included as a part of each job proposal.

Besides the standard erection procedures (so-called “metal sheet by metal sheet” procedures), during an assembly we also execute lifting by hydraulic jacks (so-called “jacking”).

There are different procedures for assembling the storage tank roof:

• Assembly through a temporary central pole
• Assembly at the tank bottom and lifting by crane
• Assembly at the tank bottom and lifting by flooding the tank with water
• Assembly outside the storage tank incl. welding the last course of the tank shell and lifting by crane

Our project preparation department suggests the most suitable procedure in light of the project schedule, required standards and weather conditions, and clients’ particular requirements.

WELDING METHODS DURING ASSEMBLY WORKS

For tank fabrication and erection on the construction site, both manual and fully automated welding methods are employed:

• Shielded metal hand arc welding (111)
• Fully automated submerged arc welding in positions PA and PB (121)
• Fully automated submerged arc welding in position PC with single or double head automatic welder for horizontal welds (121)
• Fully automated welding in all positions – methods MIG/MAG (131, 135, 136, 137)

Welding works are executed in accordance with the stated WPS procedures (EN ISO 15609-1).

OKZ HOLDING is entitled to carry out WPAR approved welding procedures, developed according to EN ISO 15614-1 for all welding methods and different types of basic and additional materials.