Meaning of “On-Stream Factor” for Process Plants
The on-stream factor or on-stream time is a key performance parameter used in the process industries (e.g., oil refining, petrochemicals, power plants) to measure the operational efficiency and availability of a plant or a specific unit within the plant.
“On-stream factor is the ratio of the number of operating days to the number of calendar days per year, the process unit remained available for production”
On stream factor is in important parameter to check the performance of the process unit with respect to plant reliability. Greater, the on-stream factor more is the plant reliable and available for production.
Definition
The on-stream factor is typically expressed as a percentage and calculated using the formula:
On-Stream Factor (%) = (Actual Operating Time /Total Available Time) ×100
Where:
- Actual Operating Time: The time the plant or unit was actively running and producing as intended, excluding the down time of the unit. The downtime of the plant might be due to maintenance activities.
- Total Available Time: The total time in the evaluation period (e.g., an hour, a day, month, or year).
Example of On-steam Factor Calculation
A crude distillation unit remained in service for 340 days and remained out of service or under maintenance for 25 days then on-stream factor of the unit is as follows.
On-stream factor = 340/365= 0.93 or 93 %
On monthly basis on-stream factor for the unit remained out of service for 6 hrs, in a month of August out of 744 hrs;
= 738/744 = 99.20 %
Importance of On-Stream Factor
- Reliability Assessment: A high on-stream factor means a reliable plant with minimum downtime. It serves as an indicator of effective maintenance and operational strategies, with the target on minimum downtime and maximum availability of the unit for production.
- Production Efficiency:It indicates how effectively a plant is utilizing its operational time to maximize output. Low on-stream factors shows inefficiencies, either due to frequent shutdowns or operational bottlenecks.
- Financial Impact:Directly correlates with revenue and profitability; more on-stream time equals more production and sales. Helps forecast production and revenue for budgeting and planning.
- Benchmarking: Used to compare performance across different plants, units, or companies. Industry standards or historical data can serve as benchmarks to evaluate performance. Companies target for high on stream factors to compete the benchmarks in their sector.
Factors Influencing On-Stream Factor
- Planned Downtime: Includes scheduled maintenance, inspections, revamps, or turnarounds. Well planned maintenance activities can improve the on-stream factor of the plant.
- Unplanned Downtime: Includes unexpected equipment breakdown, process upsets, or utility outages. It is the major contributor to a reduced on-stream factor. Unplanned downtime can be reduced by adopting high tech diagnostics and best maintenance practices.
- Process Efficiency: Process issues such as feed stock variability, lack of training, operational errors, or bottlenecks can lead to reduced production time.
- External Factors: Feed and products Supply chain disruptions, regulatory policies, or weather conditions affecting operations.
How to Improve On-Stream Factor
- Preventive Maintenance: Conduct regular inspections and maintenance to reduce unplanned outages. Implement predictive maintenance technologies using IoT and analytics.
- Process Optimization: Optimize plant operations to reduce variability and improve reliability. Address bottlenecks and inefficiencies in the process. Operate the unit at its within its operating limits.
- Training: Ensure that operators and engineers are well-trained to handle equipment and process upsets effectively. Using operators training simulators can improve the skill levels of DCS operators to work in the emergencies.
- Technology Upgrades: Invest in digitization of the process plant by using modern equipment and automation to enhance operational stability and reduce downtime.
- Data-Driven Decisions: Use real-time monitoring and performance data to identify trends and anticipate issues.
Oil Refineries and Petrochemical Plants, typically aim for an on-stream factor for more than 95% to earn the profits and sustain in the market.
