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PRE-COMMISSIONING JOB

An Experience with in itself – A Breathtaking Ride

Squeezed between timelines of construction and commissioning with no breathing space, having limited resources, without explicit guidelines, always in a race against time and above all working for a demanding customer – Operations Department.


Its quite hard to find specific guidelines, books, code and standards for carrying out pre-commissioning job of petrochemical plants. It is more like a roller coaster ride befitting for personnel having abilities of clubbing or using practical experiences and creating work arounds to get the job done within shortest possible time frame.

Pre-commissioning is the period of the project beyond Mechanical completion, when certain system is ready to receive process fluids or for the engergisation of electrical/instrument equipment.
This includes, but not limited to : Lube oil flushing, flushing of water circuits, steam blowing, instrument loop checking, calibration of instruments/Pressure Safety Valves, Catalyst loading, refractory dry outs, installation of temporary strainers, machinery alignments, blowing of process and seal lines, removal of gags and setting of spring supports, boroscopy of compressors suction lines, card board blasting, power flushing(using air/water at the same time), steam blowing, high pressure nitrogen testing and circuits air leak tests etc.

Step called, ready for pre-commissioning is achieved once the system or a portion of it has reached a point where all the relevant testing of the construction has been done except couple of items like painting and insulations etc and other items similar to which could be implemented during or after the commissioning.

Every pre-commissioning activity starts with a trigging document called pre-commissioning procedures. Pre-commissioning procedures which are being provided by operations department to pre-commissioning group can be stated as the only starting document. This document bears the information for pre-commissioning by dividing the system into different loops  and their respective requirements like providing dummy spools in place of control valves, removal of NRVs flappers, golden joints, steam/air blowing vents, water flushing hoses installations, instrument removals, temporary headers/pipe line laying and jump overs for lube oil flushing etc. It also contains acceptance criteria and loop clearance certificates for sign off, once the acceptance criteria is met, which is duly  verified, witnessed  and declared approved by relevant operations department personnel/vendor.

Taking here an example of one pre-commissioning activity like steam blowing. Installation of vents at the main header/off takes and a dummy spool in place of control valves/flow venturies covers the major job scope of steam blowing arrangements. Vents installation should be made in a way to ensure its direction at safe location and not being obstructed by any object/passage way. Each temporary vent should have a hole at its lowest point in order to let the hot condensate drain from that point and not to shower in the air during steam blowing. Insulation of steam header and vents up till man height is mandatory prior to start of steam blowing activity.

Steam blowing is done in two steps. When the arrangement for steam blowing are declared ok by pre-commissioning group, the system is cross checked by operations department for conformity against the pre-commissioning procedure. Once the mutual agreement is reached between the two interfaces steam blowing activity is planned for the upcoming night. Heating of steam system and then course blowing from the all the vent points are carried out in the first step.  Heating of the system takes almost 2 hours and which follows 2-4 hrs course blows. This step is repeated for at least two days. After this comes the turn of blowing through each vent, the whole steam of the system is being blown through individual vent at required possible flow and pressure for at least 15 mins (Piping Support to be provided for each vent arrangement in order to cope for thrust of blowing). After 5-6 blows of the system target plate is installed on couple of strategic positions to check out cleanliness level of the circuit.

In case of steam blowing at petrochemical/fertilizer plant, where steam is largely being used for fueling turbines of major compressors and pumps, where target plate installation is normally used as acceptance criteria. This acceptance is being measured as per allowable visible particle on per square inch rule according to turbine vendor recommendations. Before putting any turbine into running every single inlet line of turbine is suppose to be steam blown and cleared as per the above mentioned criteria. However in some instances during steam blowing an additional precautionary activities like boroscopy and flushing/air blowing of steam inlet lines are carried out even after steam blowing. This normally happens to get the suspect-able welding/grinding particles removed from the line when golden joint or cutting is being done after the steam blowing which were not possible prior to it due to workability constraints.

Risk taking, decision making and practical/realistic approach comes into play during the pre-commissioning job, when we talk about code and standards conformity for temporary spools fabrications, fittings, materials used and NDT requirements. In case of steam blowing the piping material used for the temporary arrangements must comply with specifications of the system as in case of failure the foreseeable consequences can be quite horrific. However due to timeline constraints and owing to temporary nature of the job piece, NDT requirements are not been conformed as per the code or standards, nevertheless best welder are being deputed for the job to minimize the risk. On the other hand where circuits are blown using process air compressor at high pressure ranging from 20-35 kg/cm2, the temporary spools/fitting specifications are based at minimum required side, which normally results in slightly lower in design requirements. Cost effectiveness and easy material handling are the two driving forces for choosing this. Just like in steam blowing, NDT requirements are also not complied in this case as per the standards. However in case where temporary arrangement are used to sustain pressure for longer period of time and risk is quite high specially incase of compressed pneumatic fluids involved, it is the job of the pre-commissioning department to evaluate as per engineering requirement and carry out necessary checks i-e NDT and hydrotesting prior to using it.

In short Pre-commissioning assignment can be reckoned as practical natured job based on experience, requires instant decision making, risk taking and realistic approach. It is a job squeezed between timelines of construction and commissioning with no breathing space, having limited resources, without explicit guidelines, always in a race against time and above all working for a demanding customer – Operations Department.

       
 
Ahsan Hafeez
Ahsin Hafeez
Project Engineer - working with Engro Fertilizers since 2007. Played a significant role in Pre-commissioning of Engro's new Fertilizer Project

 

       
       
 

 

 

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