66% increase in performance thanks to better-running rollers

The Oman Cement Company (OCC) SAOG, Muscat/Oman, has upgraded the performance of its 30-year-old conveyor, which transports hot cement powder from the cement mill to the silo, from 150 t/h to 250 t/h. The implementation of this 66% increase in capacity via a retrofit of the existing conveyor (with a horizontal length of 255 m and a vertical stroke of almost 44 m) was enabled with the use of high-performance rollers from Rulmeca.

The Oman Cement Company symbolizes Oman’s quest for self-sufficiency in its core industries. This company, with ISO 9001 certification, has become the backbone of the construction industry in Oman ever since the cement plant was established in 1983. As such, it plays a key role in the development of the country’s infrastructure and provides the necessary resources to support the nation’s self-sufficiency efforts. This has been successfully achieved. The plant is continuously increasing its production capacity, and it currently produces 2.4 million t of cement a year. All the raw materials required for its production are indigenous. The limestone deposit, additives, quartzophylites and ferrogenous quartzophylites can be found near the site of the plant. Gypsum, which is used to slow down the cement setting, is extracted from the mines at Ghaba in Wilayat Adam. Three kilns and four cement grinding mills allow for the flexible production of various types of cement.

As part of increasing the output of the cement mill, the conveying technology used in it (both upstream and downstream) has also had to cope with higher throughput. Some throughput optimisation can be achieved with the utilisation of existing performance reserves of existing conveyor technology, simply by making the belt run faster. However, in the case of the conveyor responsible for transporting the hot cement powder to the downstream silos, this buffer was no longer sufficient. Considerably more throughput capacity needed to be achieved. Yes, everything could have been torn down, with the construction of a new conveyor. However, with such large conveyors, one tries to preserve the basic frame with its supporting structures, seeing as how its implementation required such high investments. The challenge is therefore to increase throughput via a retrofit at minimum investment cost.

The engineering, procurement, and construction (EPC) specialist Synergy International FZE was commissioned with the concept for the retrofit1. Synergy International FZE has been based in the Ras Al Khaimah economic hub in the United Arab Emirates since 2005, and has more than 15 years of experience in the markets of the Middle East and North Africa (MENA) as well as in Europe and India. The company specialises in the fields of mechanical power transmission and bulk materials handling (e.g. belt conveyors, industrial chains, gearboxes, fluid coupling systems), as well as wear management solutions and environmental solutions (such as dust collection systems), ball mill optimisation, steel mill optimisation, automated flow control systems, plant assembly, and commissioning. It is thus an ideal partner for OCC.

To increase throughput via a retrofit, Synergy International FZE had to use all possible measures to ensure a higher throughput with the existing basic design. As part of this, the conveyor belt was widened by 23% (from 650 mm to 800 mm). The belt running speed was increased from 1 m/s to 1.34 m/s (i.e. 34%), and this required rollers which were significantly more resilient. The drive drum was increased from 500 mm in diameter to 800 mm, to increase grip. As part of this, the power of the drive motor (with fluid coupling and gearbox) was also increased from the existing 55 kW to 90 kW. Other important elements include Rulmeca’s high-performance idlers, which are crucial for reliable long-term operation of such large conveyors with increased throughput. Compared to simple rollers of inferior quality, they run much more smoothly, and this reduces thermal stress. In addition, they also contribute significantly to lowering overall ownership costs. This is because they have a much longer service life than simple lower-quality rollers, and they also ensure the high reliability of the entire system due to their lower failure rate.

These quality products are manufactured from precision-turned components. Especially hardened steels and other alloys ensure that the conveyor belt rollers function optimally over a long period of time and under the toughest conditions. Various protective measures for the bearings and minimal concentricity tolerances are paramount for the longevity of the bulk material conveyor rollers. Rulmeca achieves maximum precision by balancing each individual roller. It is understandable that this has its price. This investment in quality is all the more worthwhile given the higher speed and greater length of the belt.

However, large conveyors such as OCC’s are not equipped with a single type of idler. Rather, what is required is a very wide variety of components which must be precisely matched to the particular conveying task. Synergy International FZE chose the following components from Rulmeca’s bulk material transportation belt roller range in the design of the OCC conveyor.

PSV1 series rollers (20F, 108N, 323) with a pitch of 1.3 m are used on the carrying side. PSV2 series rollers (25F, 108N, 958) with a 3 m pitch are used on the return side. Both product series are specially designed for heavy-duty continuous operation under high workloads and are characterized by smooth running and minimal maintenance requirements. The rollers of the PSV2 series are designed for higher loads

For better damping of the belt at the loading point, so-called loading rollers (PSV1,20F,63/108NA,323) have also been fitted. These shock-absorbing rollers are fitted with rings designed to absorb the impulse generated by the impact of the material on the belt

On the return side, tape guide rollers of model SG080-30-800-958 are now positioned at three strategic locations. They serve to correct possible belt skew in the return direction and are characterised by the fact that they can centre themselves

On the carrying side, self-centralising troughing sets with a braking effect (P3SF/70 F14 108 H155) were also applied every 25 m: in the event that the belt is misaligned, the self-centralising rotation of the troughing sets guides the belt back to the centre

In addition to these moving parts, Synergy International FZE has also used Rulmeca conveyor roller accessories, thus ensuring the provision of virtually all components from a single source:

A3P1 series transoms (5A-F14-108 H155 Z) are used for smooth belt transition from 10 to 20 and from 30 to 35 degrees of trough angle

SPT series supports (1478 H70 Z) are used on the return side

A primary cleaner (HM-800) and a secondary cleaner (P-800) achieve almost 100% cleaning efficiency at the conveyor’s head. A plough cleaner (VLP-800) is also used for rear cleaning

The retrofit design and component selection was carried out with the use of software by the Australian company Helix Technologies. The modelling was done using SOLID Works (USA) and AutoCAD. Structural analysis is the main tool for ensuring that a structure can withstand the various types of forces that it will be exposed to during its normal operation – this was managed with the German software Dulbal. The feed chute has a wear-resistant lining for a longer service life – this was also modeled using Helix software. The project was wholly managed using MS Project. Rulmeca provided corresponding CAD data for its entire range. This allowed Synergy International FZE to provide OCC with a complete package in which all components in use were comprehensively coordinated with each other. Rulmeca always cooperates with local partners on such conveyor technology tasks, so that the end user can be provided with the most comprehensive support possible during the development process and, as a result, may also be able to take care of maintenance tasks quickly and efficiently (should these be necessary at all): Rulmeca’s conveyor belt rollers are designed for maintenance-free operation of at least 30000 h. Incidentally, the challenge in the design of the feed chute was to optimise it so that it could not overflow – this was a problem with the previous conveyor in particular – but this bottleneck is now a thing of the past.


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