A component is considered obsolete when it is no longer supported by the vendor. The IEC 62402 standard [1] on Obsolescence management defines Obsolescence as the “Transition from availability to from the original manufacturer to unavailability” and considers a component to be obsolete when it is not available from the original manufacturer to the original specification.
One of the main reasons for obsolescence is advancement in technology. New technologies offer products with improved performance and additional features. Advances in technology even make it cheaper to produce new components, when compared with the old technologies. A second reason for obsolescence is the evolving standards and changes to regulations, which can lead to non-compliance of the old equipment. For process control systems, obsolescence can apply to hardware, firmware, software platforms and application software for the process plant distributed control system (DCS) and any package equipment programmable logic controllers (PLCs).
Once a product is obsolete, the manufacturers cease selling the hardware and supporting the legacy software associated with the product. Every manufacturer defines phases of the product lifecycle and the current status of the product. An example of product lifecycle phases for a control system could be as follows
- Mainstream Phase –The product is actively being sold, promoted and fully supported by the original equipment manufacturer (OEM).
- Mature Phase – The product is supported by the manufacturer but is withdrawn from sale.
- Extended Support Phase – The product is no longer supported by the manufacturer. However, support can be provided by a system integrator and essential spare parts are still available on the market.
- Obsolete Phase – The product is not supported by the manufacturer. Essential spare parts, maintenance tools or key specialist resources are not readily available in the market.
Control system hardware failure rates generally follow a bathtub curve over their lifecycle. The lifecycle can be split into the early stage when the equipment is first introduced, followed by the useful life when the equipment is in service and the final stage when the equipment exceeds its service life.
During the wear-out period, the failure rate rapidly increases and this can lead to an increase in maintenance activities. The maintainability of the equipment in turn will depend on operational spares in the warehouse and spare part availability in the market. For obsolete equipment, the plant may need to stock additional operational spares or buy refurbished hardware since the product is no longer sold by the OEM. In addition, with no support available from the OEM, skilled engineers familiar with the product to troubleshoot and maintain the equipment may not be readily available. These factors make obsolete equipment difficult to maintain during the wear-out period of the lifecycle and increase maintenance costs.
If the equipment is production critical, then increased time to replace or replace failed obsolete control system components at a process plant can have a significant impact on the availability of the asset. This in turn will affect the production capability of the process plant and lead to loss of revenue.
Therefore, a proactive approach is recommended to address the obsolescence of critical process control systems, rather than waiting for equipment to become obsolete before planning an upgrade. Convincing management to invest in migrating to a new control system is always a challenging activity. Budget constraints can make upgrading of an entire DCS, which is often a multi-million dollar investment, difficult to justify. The financial impact of not upgrading obsolete equipment is to be considered. This can be supported by evidence of actual failure events at the facility that have led to the loss of production. A well-planned strategy on how to address the obsolescence risks should be developed. This usually starts with an obsolescence risk assessment.
How can we assess obsolescence?
So, how do we go about determining if we have an obsolescence risk at our process plant? The first step is to know your asset and identify what is installed at the process plant. It is advisable to review all the system architecture drawings for the facility and identify equipment at the different levels of the Purdue model.
During this step, the owners of equipment will also be identified, for example, the equipment in level 4 (Business Planning and Logistics) may be managed by the Information Technology (IT) department within the organisation, while levels 0 to 3 would be managed by the production and operations department. Process control equipment lies within levels 0 to 3 of the Purdue model.
A site survey should be carried out to verify all the process control equipment against the available documentation. The key documents that can assist will the survey are the system architecture and network architecture drawings, functional design specifications, operation and maintenance manuals, control system cabinet general arrangements and equipment lists. The equipment to be surveyed typically covers the Central Processing Units (CPU), Input/output (I/O) Modules, Power Supply Units (PSUs), Human Machine Interface (HMI) – Panels, Servers and Workstations. The network equipment such as switches, hubs, converters and routers are also covered. Depending on the various types of equipment, the information to be collected can include hardware model and serial numbers, firmware versions, operating system software versions, application software versions and communication protocol versions used.
Once the survey is completed, information can be collected and maintained in a database, let’s call it an obsolescence database, for all the process control equipment. The OEM should be consulted to determine the lifecycle status of all the equipment. This lifecycle information should then be included in the database and the timeline for the next phase should be included.
On reviewing this database, the plant may discover that a lot of equipment is in the extended support phase or obsolete phase. This indicates that the plant is already facing an obsolesce risk that could lead to reduced plant availability. However, some equipment is more critical to plant safety and productivity than others. To be able to prioritise and justify the list of equipment to be upgraded, an obsolescence risk assessment of this equipment is to be carried out.
How can we manage obsolescence?
Depending on the size of the plant, budget constraints and the resources available, if an obsolescence risk assessment has never been performed, it is more practical to exclude mainstream equipment and any equipment having more than 4 years remaining in the mature phase of the lifecycle from the risk assessment.
A key to the success of the obsolescence risk assessment is having the right people in the room. The team should include competent & experienced personnel from operations and maintenance, process engineers, instrument and control engineers, automation engineers, systems engineers and network engineers. Whenever possible, an external consultant or system integrator familiar with the facility should also be invited to the assessment.
In preparation for the obsolescence risk assessment, it is vital to evaluate the current inventory levels for the identified obsolete equipment and any trends where there has been a frequent re-order of components.
An interesting approach to evaluating obsolescence risk is described in the paper “Obsolescence Risk Assessment Process Best Practice” [2]published in the Journal of Physics Conference Series. This paper proposes using a probability matrix where the probability of an obsolescence issue is evaluated based on stock consumption vs consumption rate and the years to end of life vs the number of manufacturers. This probability is then evaluated against the operation impact evaluated during the risk assessment. The operational impact can consider the potential consequences of the failure of the equipment to personnel health and safety, environment and regulations, production loss and asset damage. Any supporting plant operation data like recorded incident reports of process control equipment faults and failures that have resulted in production downtime will serve as valuable input to the operational impact assessment.
The outcome of the obsolescence risk assessment is a risk ranking of high, medium or low for each of the obsolete equipment. The plant can now go about defining a strategy to manage each of the risks and define mitigation measures till the equipment is replaced or upgraded. The corrective actions to address the risks and mitigation measures are to be further developed and prioritised, taking budget and resource constraints and the company’s business objectives into consideration.
Low-risk components will be less critical to safety and production and could be dealt with in a reactive way, where the equipment is run to fail and replaced on failure.
For the medium and high-risk components, a strategy to manage obsolescence risks is recommended and mitigation measures till the equipment is replaced or upgraded should be defined. One mitigation measure is a high-cost purchase of sufficient stock of obsolete components to cover the period till the upgrade or for the remaining period that the equipment use is anticipated. Another may be to purchase refurbished parts or find the best alternative substitute from the same or different manufacturer that can be replaced without any design changes. There may also be an opportunity to reclaim stock by upgrading in phases, for example on pipelines that have several identical remote terminal units (RTUs), the control system can be upgraded at a few critical RTUs and the obsolete parts can be used as spares in stock for the remaining RTUs. This will in turn provide additional time to manage obsolescence across all the RTUs.
The strategy to manage obsolescence for critical equipment should be a long-term plan that considers technology forecasting and long-term business case planning and development. For an obsolete DCS platform, an upgrade of the entire system should be planned. DCS upgrades are always complex, particularly when there are various control system packages across the facility. The operating company can work jointly with the OEMs to ensure that the obsolete equipment is managed until a migration is performed.
It is good practice to re-assess the obsolescence database and the risk assessment once every two years and after every plant turnaround. Many upgrade activities may also be planned to coincide with the plant turnaround schedules. The various control systems can also be broken down and upgraded in phases, for example, the HMI graphics can be upgraded in one year and the CPU and IO modules, a year after, to coincide with a planned plant shutdown.
The facility may also consider setting up long-term spare parts, extended support and technical service contracts with an OEM to manage the obsolescence database, especially if an upgrade of the DCS is being planned over the next few years.
As the famous saying goes “Everything that has a beginning has an end”, similarly, the obsolescence of control systems cannot be avoided. However, a management program that is well integrated with the plant maintenance and inventory management plans together with careful preparation and planning to upgrade the obsolete equipment can safeguard the facility against obsolescence risks and minimise the impact on the plant availability and reliability.
Related Articles
References
- IEC 62402:2019 – Obsolescence management
- J Romero Rojo, F & Roy, Rajkumar & Kelly, S. (2012). Obsolescence Risk Assessment Process Best Practice. Journal of Physics: Conference Series. 364. 10.1088/1742- 6596/364/1/012095.
Further Reading
- Strategies to the Prediction, Mitigation and Management of Product Obsolescence by Bjoern Bartles, Ulrich Ermel, Peter Sandborn and Micheal G. Pecht.
- The Book of Obsolescence Management (BoOM) by Mark Proctor and Jonathan Wilkins