Serbia Project Case | Drawing-Based Plate & Weld Neck Flanges
Project details
An equipment engineering customer in Serbia ordered a full set of non-standard flanges machined to their own drawings. The project covered plate-type and weld neck flanges in multiple sizes, supplied in A105 carbon steel and 304/316 stainless steel, with black oxide or mirror-polished finishes depending on service conditions. The flanges went into chemical plant, municipal pipeline and construction machinery piping systems.
Customer Drawings
The customer supplied a complete set of self-made engineering drawings, and no off-the-shelf standard flange could match them. Everything was built to the drawings: flange OD, bolt hole count and spacing, center bore, flange thickness and boss height all followed the tolerances marked on the prints, with hole patterns and thread specifications machined individually as required.
Material selection followed the pipeline medium. Corrosive service took stainless steel flanges with a mirror-polished finish, while ordinary oil and gas lines took A105 carbon steel with black oxide anti-rust treatment. Different sizes had to be boxed separately with paper separator pads between pieces, so the sealing faces would not get scratched in stacking. Every box also needed an English packing list cross-referenced to the drawing number, plus material test reports and dimensional inspection records for European inland customs clearance.
The customer checked dimensions and hole layouts with us remotely several times. Only after the first article passed physical measurement verification did they release the batch production order.
From Drawings to Production Plan
Our technical department translated the foreign-language drawings, converted the dimensions and broke down the machining process, then confirmed the details with the customer in two rounds. All critical dimensions were extracted with machining tolerance ranges marked out, and special-shaped holes and non-standard threads got their own dedicated fixtures.
The process route differed by material. Stainless steel flanges went through multiple mirror-polishing stages, while carbon steel flanges received an overall black oxide treatment after machining. Large-diameter flanges were rough and finish turned on the CK5112 CNC vertical lathe; small and medium sizes ran on CNC lathes and CNC drilling machines in an integrated setup, keeping hole positions and flatness uniform across the batch.
The first article went through full-dimensional caliper inspection. We sent the measured records and photos to the customer for sample approval before starting volume production.
Production and Inspection
Carbon steel and stainless steel raw materials were stored in separate zones, verified by spectrometer on arrival, and filed by heat number for traceability.
Machining followed a fixed sequence:
- CNC vertical lathe/lathe for the OD, end faces and sealing bosses, with flatness tightly controlled
- CNC drilling machine boring holes to the drawing coordinates, keeping bolt holes concentric
Surface treatment split by grade: stainless steel pieces were polished to a mirror finish over several passes, carbon steel pieces were black oxidized for corrosion protection.
Every finished flange was measured against its original drawing dimension by dimension, with actual readings recorded. Hole positions, thickness and bore were inspected 100%. After deburring, our workers sorted out any scratched or defective pieces and placed the approved flanges in metal turnover baskets, kept apart while waiting for packing.
During production, we regularly sent the customer workshop photos, pictures of flanges in turnover and the dimensional inspection records, so they could track a multi-size order in real time.
Packing for Inland Transport
The route to Serbia runs long-distance overland with several road transfers, so packing was designed against impact and moisture in layers:
- Paper buffer pads between flanges, each piece wrapped in stretch film against moisture and friction
- Flanges of different drawing specifications packed in separate cases; heavy-duty solid wood export cases for large, heavy flanges, with buffer clearance left inside
- Wooden cases stacked uniformly on solid wood pallets, cross-locked with high-tensile strapping, the whole pallet sealed in stretch film for moisture protection
- An individual English packing list on every case showing drawing number, specification, quantity and material; material certificates, dimensional inspection summaries and the commercial invoice consolidated for Serbian customs clearance
After all pallets were strapped and wrapped, we counted and arranged the full truckload, took panoramic loading photos and sent the complete document set to the customer.
Delivery Result
The goods reached Serbia by long-haul road transport. At unpacking inspection, all flange dimensions and bolt hole positions matched the original engineering drawings, assembly lined up without misalignment, and sealing face flatness met specification with no leakage risk. The polished and black oxide surfaces arrived intact — no impact damage, rust or scratches from the long transit. Size-by-size packing was clear, and the material and dimensional inspection documents were complete, so inland customs clearance went through smoothly.
The custom flanges now fit across the customer’s equipment piping systems. A long-term drawing-based supply arrangement is in place, and repeat orders for additional non-standard flanges have continued since delivery.
Author: Lewis Liu
Hello, my name is Lewis Liu, and I’m a professional sales engineer with over a decade of expertise in the flange fittings sector.
I am quite informed about flange selection, installation, and maintenance. I am passionate about providing customers with the greatest solutions for keeping their pipeline systems running smoothly, safely, and dependably.
If you have any queries or concerns concerning flange fittings for your pipelines, whether they are about selection, material choice, specification requirements, or anything else, please contact me at any time. I am dedicated to providing expert advice and assistance to help you make educated decisions and reach your objectives.
