Our factories have been manufacturing and supplying anchor chains to the international offshore industry since the 60's. During the years Ramnäs Bruk has improved the production process in order to meet the new customer requirements and use technical developments for automation. New methods of the production process brings an efficient production and cut our costs. Co-operations with the steel industry have improved the steel quality and new high-strength steel for large chain dimensions has been developed.

Today our production capacity is 17000MT per year.

The three most important factors when producing high quality chains are the material, the welding procedure and the heat treatment of the chain - the rest is only control. Ramnäs Bruk only use steelworks qualified and approved by classification societies.

See our production, click on the below images.

The heated blank is bent into the forged chain and thus connected to the chain. This process is performed in the bending machine. It is the responsibility of the forge operator to check the pre-formed link. The checking comprises the following:

Symmetry

Shank alignment

Surface condition of bending tools and rollers

Links are flash-welded. The flash-welding machine is pre-set according to data depending on chain grade and size (welding recipe). The welding recipe is set by the production engineer and stated in our monitoring system Race-Q. It is the responsibility of the operator to continuously check that the welding clamps are clean and have a snug fit.

The flash-weld burr is trimmed by a flash removal tool working along the periphery of the weld. The cut surface aligns closely to the link surface. The operator is responsible for the tool condition. Deburring stripes deeper than 0,5 mm are not allowed.

Ramnäs Bruk's stud anchor chain is fitted with drop forged studs. The asymmetrical design of the stud gives equal stud footprints and contributes to a symmetric stress-distribution in the link.

The purpose of the heat-treatment is to give the link and particularly the weld zone such a microstructure that the desired criteria for mechanical properties are satisfied and the chain load-tests are passed. The treatment is performed in continuous automatically controlled furnaces and consists of austenitization and tempering, both operations followed by water cooling.
The furnace settings are given in Race-Q and the furnace operator reports in the Race-Q system.

The following data are continuously recorded by the furnace instruments:
- Furnace temperature, in each zone
- Water temperature
- Chain speed
The furnace operator logs into the computer recorder and confirms in writing the identity of the chain that is treated.

Mechanical testing of samples taken from the finished chain is performed in order to confirm that pertinent mechanical criteria are fulfilled.

The sample sets are retrieved per the sampling frequency specified in the classification society rules and per each melt of steel.

A normal set of test specimens taken from one sample consist of:
- One break test, three-link-sample. For dimension above Ø 132 mm acc. to DnV rules one link/cast is breakload tested
- Tensile and impact tests, one link
- Spare, one link

The chain must not be proof-loaded until mechanical tests and the break test have been approved.

The mechanical testing is performed according to rules by the classification societies. The test results are recorded in our monitoring system Race-Q.

The proof loading is performed by continuous testing machine. 5-7 links are proofloaded with 2 links overlap. Every link is load-tested to the proof-load specified by the pertinent classification society. Three-link samples are load tested to the minimum breaking load. The load testing is performed in a continuous load-testing machine with computerised recording of load. Click on the image beside to see an Actual Breakload Test.

Ramnäs Bruk's controlled stud expansion, performed after proof loading is the standard method in Ramnäs Bruk production process since 1991.

The purpose of the final magnetic particle inspection is to safeguard that no surface defects remains on the finished chain. The wet method is used in combination with fluorescent light. All links are checked in the most sensitive areas, the link-surfaces which have been in contact with the electrode clamps of the welding machine, the weld itself and its vicinity. For chain diameters of 132 mm and above 10% of the links are subject to surface control of all accessible surfaces. The link identification established at the pre heat-treatment control is utilised at reporting of the MPI-results in Race-Q. The inspection is performed by qualified and certified personnel.

The purpose if the ultrasonic inspection is to check the interior of the link weld. This is obtained by the use of angular probes for testing every link in the longitudinal direction through the weld. UT results are reported in Race- Q. The inspection is performed by qualified and certified personnel.