The checking and testing phases of a new plant is by necessity a relatively detailed and sophisticated process. Not all parts of the plant reach the same degree of completion at the same time, hence some areas or units may be mechanically completed, while others are not. It would therefore be a waste of time to wait for the whole plant to be mechanically completed before starting commissioning activities.

The project planning shall be optimized if the completion activities are organized not as whole plant activities, but as Operational “System” and “Sub-system”. The “System Approach” induces the following terminology, related to the Systems, Sub-systems, and the relevant milestones:

  • Sub-system is “Ready for Commissioning”, when all Pre-commissioning activities are complete.
  • Sub-system is “Ready for Start-Up”, when all Commissioning activities are complete.
  • System or group of Sub-systems are “Ready for Operation”, when all Start-up activities are complete.

System/Sub-System Definition

This specific partition of a plant into Systems and Subsystems for completions activities takes place as early as possible, at “Basic Engineering” phase. This is carried out by OICO, in accordance with precise Sub-systems delimitation rules and reported on marked-up PID’s and One Line Diagram’s as support documents.

Resources for the training and implementation of OPERCOM™ and ICAPS© shall be planned at an early stage during the detailed engineering phase.

The completion activities of a new hydrocarbon processing plant consists of a series of verifications carried out just before the plant is brought on line. The aim of these verifications is to ensure, as thoroughly as possible, that every piece of equipment is built and operated according to the design. These verifications are also the last critical review of the design before the Start-up. Their ultimate goal is to render the oil or gas plant as safe and trouble free as possible.

These completion activities are separated into two main phases, Pre-commissioning and Commissioning, this split roughly corresponds to the static and dynamic tests phases respectively. These completion activities are followed by the Pre Start-up and Start-up phases, corresponding to the introduction of the hydrocarbon feed into the plant.


Pre-commissioning consists of inspecting equipment installations to ensure proper installation according to the initial engineering drawings and conducting cold/static/ de-energized tests. Pre-commissioning activities will be executed on a Sub-system wise basis by construction subcontractors and supervised by the commissioning team.

It should be considered that for hooked up sections, pre-commissioning activities will be executed.

Pre-commissioning includes following three main types of field activities:

  • Conformity checks of equipment items by using related check lists.
  • Static/de-energized tests of equipment items by using related test sheets.
  • Specific operations, such as the pipes and vessels flushing and cleaning.


Commissioning consists of live and on line tests of major equipment after energizing. Commissioning team performs the commissioning activities based on the defined Subsystems.

Commissioning corresponds to hot/dynamic/energized tests, which essentially, include the three following categories of tasks:

  • Dynamic verifications
  • Running-in and on-line tests
  • Piping and vessels preparations

Pre Start-up

Prior to conducting the commissioning operational tests and/or introducing the feed into the plant, a number of specific process operational activities must be carried out on the piping and vessels. This group of activities are classified under the generic terminology of ‘’Pre Start-up’’ activities.

These operational activities, which their proper preparation and execution are integral to the commissioning phase, include the following groups of activities:

  • ESD checks
  • Safety system checks
  • Operational tests


Start-up activities begin with final preparations for the introduction of the feed into the plant and consist of a series of various tests carried out, while the plant is being brought on line. The aim of these tests is to ensure that all equipment operate normally and securely.

Start-up activities are prepared with the integration of specific Start-up and routine procedures that are prepared by OICO. The field activities consist of two sub-stages:

  • Operation prior to oil/gas in
  • Operation after oil/gas in

Using the correct maintenance strategy and successful planning method, practice, and process enables OICO to deliver high work productivity, improve the plant availability and ensure equipment reliability.

OICO’s maintenance strategy focuses on the following four important areas:

  • Increasing the plant stability,
  • Increasing the plant life time,
  • Increasing the equipment and plant availability,
  • Decreasing the maintenance and operation costs.

To achieve these goals and ensure that our strategy is effective, OICO’s maintenance department maintains the following 4 main sections:

  • Executive maintenance of all disciplines
  • Maintenance methods and planning
  • Condition based monitoring (CBM)
  • Technical inspection.