Designing for Efficiency:
A Case Study in LPG Cylinder - Conveyor System Optimisation
Client: Indian, Oil Marketing Company
Industry: Oil & Gas (LPG Cylinder Refilling Plant)
Type: LPG Cylinder Conveyor System re-designing
Project Overview:
A familiar officer we had worked with before reached out with a challenge
The Ask?
To redesign the conveyor system for a LPG cylinder filling shed preparing for a major upgrade—a 48-point carousel. We executed the project under a formal Purchase Order. Our challenge was clear—redesign the conveyor system to handle double the capacity while working within space constraints and integrating new machinery.
The key aspects that we needed to account for during the design process included:
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Increased Throughput: With the 48-point carousel replacing the earlier
24-point carousel, the line’s capacity was doubling. This required the addition of a new branch in the conveyor system. -
Limited Space: The new branch needed to fit within the existing shed, which had limited available space.
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Machine Overhaul: All downstream machines after the carousel had to be replaced or revamped, and the upstream machines needed to be upgraded, requiring modifications to the lines.
Challenges:
There was another 24-point carousel (let's call it K2) in the shed that was staying as-is. In designing the conveyor line for the 48-point carousel (K1), we required at least four unloading fingers and four loading fingers to ensure proper flow of cylinders. Plant had only 4 finger available and the earlier carousel (K2) was already using two of them, leaving us with just two more for the new conveyor system for K1. This created a bit of a challenge, especially considering the initial firefighting limitations that restricted the construction of additional unloading finger.
Further complicating matters, K1- the 48point filling station carousel was going to be positioned in the center of the shed, in the position where earlier carousel was placed and we didn't have enough dedicated space for the conveyor route to accommodate the cylinder identified due for pressure testing or so called as rejected cylinders. The only option was to run a conveyor line above the existing system—similar to a highway. This wasn’t a common solution, but drawing from my previous experience with a similar project, I knew it was possible.
Regulatory Standards:
The regulatory guideline we adhered to was OISD-144, which is most stringent when working on LPG bottling installations in India which is guided under SMPV(U) Rules , 1981. While there are other codes also to follow, OISD-144 is the most detailed and specific,
A major change I proposed was to separate the K1 and K2 conveyor lines. Previously, there was a connecting conveyor line for both K1 & K2 lines, which could cause issues with machine sequencing and automation. By making the lines independent, we gave both K1 and K2 the freedom to operate or undergo maintenance without affecting each other. Our design also had to plan for the cylinder storage (empty and filled) where OISD144 governs safety distances for storing both of them meticulously.
Designing Objective:
Beginning from the purging unit, which is required near the unloading area, needed to be repositioned due to space constraints. Initially, they asked me to place it on the unloading finger, but that wasn't permissible under the code. So, we added an additional branch of the conveyor to accommodate the purging unit. This not only made space for the unit but also provided enough room to process cylinders at a rate of 1000 cylinders per hour. Our design was also to suit to a total input of 3500 cylinders approx, making about 1000 cy per unloading line per hour. This was nearly exactly the rated capacity of the 48-point carousel which is theoretically 3200cy/hr .
Solutions:
Once we positioned the purging unit, washing machines, and vision unit and the carousel, we needed to plan for the rejection line leading to the pressure testing shed conveyor line. After discussing with the client, I suggested this elevated rejection line. I also had them reach out to a previous client I worked with to get feedback of such a elevated conveyor line. The key to design this elevated conveyor, was ensuring that we had enough clearance for the tallest cylinders (the 19kg cylinders) and a little extra for safety. We also had to ensure the incline and decline of the chain conveyor system line were designed in such a way that the cylinders wouldn’t topple, thus a steep incline was ruled out and longer incline was opted. This opt also elongated the conveyor sections.
The 48-point carousel, also known as the Flexispeed carousel, has very specific space requirements for its ancillary machines and conveyors. After calculating the distances, we found that the newly drafted conveyor exceeded by 100-150 meters by the earlier, which was a significant challenge given the space limitations and restrictions on new finger construction.
However, during a joint meeting with the corporation’s project team, which included the Head of Projects, the Head of South, Project Coordinator, the Plant manager, and others, we received approval to build a new unloading finger, even if it had limitation based on the firefighting calculations. This was a critical moment, as it allowed us to move forward with the design, despite initially conflicting with firefighting codes. The Head of Projects had a unique approach to resolving the issue with firefighting calculations as well, but that’s a separate case study on its own.
With the new finger in place, we had the necessary space to achieve the required distances for K1. We also strategically positioned the 48pt Felxispeed carousel in the facing opposite direction, which allowed us make the conveyors to take a round-about to reach and increase in the minimum required meters to travel. This move also ensured that we have more designing space for conveyor lines for quality check machines. Within two revisions we able to finalise on that as well.
Solution & Conclusion:
By the time we were ready for final approval, we had successfully positioned all the necessary equipment: purging unit, washing machines, vision unit, and other quality check stations. The layout was designed to accommodate all machines for both K1 and K2, ensuring smooth operations in the cylinder filling shed. We also had to plan for the HR/CR rejection machine and an auto cap-removal machine, which were installed on a trial basis, to be accommodated in the newly designed lines.
Ultimately, the plant now had an adequate chain conveyor system, a carousel positioned on other side and elevated conveyor system, which wasn’t initially preferred by the operations team. Add to that, owing to the new PESO (Petroleum & Explosive Safety Organisation) regulations, we had to design a transport system to have the rejected cylinders reach the degassing shed to degas themselves, located 60 meters away! This led us to move away from the idea of an elevated ground conveyor and instead opt for an overhead conveyor system. This OHC system would the take the rejected cylinders from K1 & K2 Lines to the degassing shed, and the same loop was taking them to pressure testing shed.
By carefully planning every detail, from the conveyor layout to meeting regulatory standards [PESO, OISD-144, SMPV(U)], we reached the point of approval. The layout is now fully approved, and the design project has successfully reached completion.
Final Inferences:
Working on this project was an enriching experience. It involved overcoming several challenges, especially with space limitations, regulatory requirements, and technical constraints. But by thinking creatively, adhering to safety guidelines, and collaborating closely with the client, we were able to deliver a solution that met all the requirements and standards.
For anyone working on similar projects, the key takeaway is the importance of flexibility and innovation. You may encounter unexpected challenges, but with a problem-solving mindset and careful planning, even the most complex systems can be successfully designed and implemented. It’s about finding the right balance between regulatory standards, operational needs, and engineering feasibility.