Introduction

FIT provides process control system audit services to clients who want to assess the overall capabilities of their control systems and how well they are used by plant personnel. The primary objectives of the audit are to identify areas for improvement in control system performance and to determine the cost/benefit details of system upgrades and new applications.

The field of process control combines the multiple disciplines of chemical, process, electrical, electronics, computer and network engineering. Control systems today employ a wide variety of field instrument devices, analysers, analog and digital controllers, control valves and interconnecting signal tubing, wiring and networks. Control engineers who are involved in day-to-day operation and maintenance of control systems must be intimately familiar with many of these disciplines in order to be effective. FIT audits can provide valuable insights to these engineers and their managers and assist them in making quality decisions about the future maintenance and development activities they should consider for their control systems.

Scope of Work Involved

FIT Consultants assist clients by providing a comprehensive audit that comprises:

1. Determination of the current status of the control systems at all levels. The levels may include:
   • Field instruments and process analyzers
   • Control valves
   • Analog and digital control hardware and software at the regulatory level
   • Digital control hardware and software at the supervisory and advanced level
   • Emergency shutdown sensors and Programmable Logic Controllers (PLC)
   • Fire and gas detectors and alarm hardware
   • Signal tubing, wiring and networks
   • Control rooms and ergonomics
2. Determination of the current organization of control systems group, engineering department and instrument/electrical maintenance department. The organization includes the local plant and any head office support staff plus outsourced services.
3. Comparison of the current status with "Best Practices" in the industry in order to determine opportunities for improvement.
4. Determination of activities and projects to be carried out to reach "Best Practices". The activities and projects include updates to control systems at all levels as well as organizational improvements.
5. Determination of preliminary cost estimates and the economic benefits of control system and control room upgrades. A proposed plan of action with time lines and major milestones is prepared.

Methodology

The methodology comprises three phases:

1. Information gathering - Before coming on-site with a compact team of seasoned control system consultants, FIT will transmit a "request for information" to the client. Some of the requested data includes organization charts, Process and Instrument Diagrams (P&ID), Simplified Process Flow Diagrams (SFP), and local plant economics information. After arriving on site, the team will conduct a number of interviews that includes plant personnel at the management level, process control group, operators in the control room(s) and the field, plus instrument and electrical maintenance personnel. Sometimes it is necessary to interview some people from the information systems department depending on how a plant is organized. FIT uses interview templates that improve the effectiveness of the information gathering process.
2. Information analysis - After the information gathering process has been completed on-site, the FIT consultants will frequently return to their home bases and begin the analysis activity. It is also possible to do the analyses at the client's location if desired. The analysis phase begins with a review of the interview notes and preparation of a list of follow-up questions that the client needs to respond to. Once all the clarifications have been received, the analysis phase will be completed. A key activity is the development of the opportunities via the "Gap Analysis" by comparing "Best Practices" in the industry with the observed practices at the client's plant. Considerable attention will be paid to local work practices, skill levels, and availability of resources because FIT knows that it is very important to reflect the client's circumstances while still trying to achieve "Best practices" in the long term. The deliverables from this phase include:
   • A proposed set of activities and projects that should be considered over a five year period
   • A feasible time line or implementation schedule of the proposed projects
   • A preliminary estimate of the potential benefits of control system upgrades or replacements using local economic data
   • A preliminary estimate of the project costs using local resources where possible
3. Management presentation - The findings, recommendations, benefits and costs are packaged on CDROM and presented to the client on site by FIT consultants and discussed thoroughly. Any changes that need to be made to the recommendations as a result of the discussions will be incorporated on a new CDROM.

Examples of Typical Recommendations

Below are some typical examples of recommendations that were made to clients over the past fifteen years. It shows that wide variety of technical content is covered in the control system audit:

1. Off sites
   • Tank farm does not have enough Motor Operated Valves (MOV) to allow automatic oil movements to take place. Additional MOVs must be installed over the next three years and a simple oil movement system should be considered.
   • Enraf tank gauges are failing frequently and Man Machine Interface (MMI) is old. Newest release of the tank gauges and a new MMI should be considered for next year's budget cycle. In addition, a suitable serial data link should be added to connect the tank gauging system to the Distributed Control System (DCS) in control room X.
   • pH control system in the bug plant should be replaced immediately.
2. On sites
   • Regulatory control systems (both analog and digital) are running with 40% of automatic controllers set to manual. This situation is abnormal and the reasons for operating the loops on manual must be investigated in detail and corrected immediately. Not doing so may result in seriously unsafe process conditions as well as loss of revenue through poor product quality control.
   • Large number of analog and digital loops do not appear to be tuned properly. Current technology exists to track loop performance automatically and to propose better tuning constants. This technology should be acquired and evaluated.
   • Several Advanced Process Control schemes have service factors below 60%, while some are turned off. The causes of these low service factors must be investigated and the disabled APC schemes turned back on. The problems with APC schemes are frequently due to poor tuning of regulatory control loops as noted above.
   • There are not enough flow meters on a number of process units to allow calculation of a material balance. This situation should be corrected at the earliest opportunity. Current practice is to have an hourly mass balance that is computed on line using reconciled flow measurements.
   • Control valves in several locations do not have positioners. This leads to very poor loop behavior in most cases. Positioners must be fitted immediately.
   • The instrument air is saturated with water throughout most of the plant. This is caused by a failed regeneration control scheme on the desiccant beds of the air dryers. The condition of the desiccant is unknown. At the very least, the regeneration controls must be recommissioned.
3. Utility Plant
   • Insufficient field instruments have led to a situation where the plant does not know accurately how much steam is provided to each process unit. Additional flow meters must be installed during the next major boiler #6 and #7 shutdown.
   • The automatic blow down systems do not function properly. New conductivity analyzers should be installed. This activity can be carried out during the next planned shutdown.
4. Control Rooms
   • Utility plant control room is extremely close to a main high pressure steam header (in fact, it runs partly through the room). This can lead to unsafe situations in case of emergency. Also, the noise level in the control room is above the OSHA limit. This control room should be relocated. Where possible, the consoles should be placed so that the operator faces the process he controls.
   • The console layouts and poor lighting in control rooms A, B, and C lead to higher than normal operator fatigue and error rates. These control rooms should be immediately upgraded to current standards.
5. Organization
   • Several process analyzers do not work reliably and have poor service factors. The analyzer maintenance group work load and skill level must be reviewed and corrections made to improve analyzer service factors.
   • There is a lack of clear documentation about emergency shutdown procedures in the control rooms. These documents should be updated to make them clearer and possibly be made available on line on the operator console screens.
   • Too many nuisance alarms are generated during upsets. Alarms should be reviewed regularly and rationalized to reduce the nuisance factor to a reasonable level. New alarm display technology should also be considered for the next budget cycle.
   • Control valve maintenance is outsourced to a local contractor. There are signs that this contractor is cutting corners and that valve seats and packing need to be replaced more often than necessary. A new contractor should be hired, or the service should be done by the plant mechanics as was the practice about seven years ago.
   • There are not enough control engineers to keep the systems in the plant properly tuned and maintained. There is enough work to keep two new control engineers busy. Any projects for control systems are handled by the engineering division of the plant in city Y. The current complement of engineers and the new ones should be enough to absorb any new projects, provided that they are handled by engineering division personnel.