Precommissioning: ticking every box

Carey Aiken, Online Electronics Limited, UK, explains how the utilisation of monitoring, testing and logging technologies at each stage of the precommissioning of a subsea pipeline can provide assurance, mitigate risks and ensure that vessel time and schedule is maintained.

As we know, when it comes to subsea pipeline precomissioning, maintaining vessel schedule is key to a successful campaign and mitigating unforeseen project costs. It is vital that a successful operation or test is quickly confirmed, allowing the contractor to proceed to the next stage. There is also the potential for setbacks to occur – how quickly these setbacks are identified and resolved will determine the impact they have. Therefore, it is vital that real-time

information and data is available, to allow for informed decisions to be made and for the precommissioning to be carried out on schedule.

Online Electronics Limited has been supporting subsea pipeline operators and contractors for 25 years with technology designed to provide and collate the necessary data at each of the stages explored in this article.

Flood and clean During the flooding and cleaning of a newly laid pipeline – in addition to how efficiently and effectively the line is cleaned and prepared for the hydrotest – it is vital that the chosen pig train design allows for uninterrupted travel through the pipeline and into the subsea receiver. Strategically placed pig signallers and a suitable pig locating and tracking system ensure that you can quickly, and with confidence, identify when the pigs have been launched, received or, in the worst-case scenario, locate a stationary (lost) pig at an unknown location, thankfully not such a common occurrence during pipeline pre-commissioning.

The most frequently carried out pig locating operation during precommissioning is confirming the pig train has been successfully launched and then received. This can be achieved by installing a magnetic pig signaller at the pipeline receipt end. Online’s range of magnetic signallers use a two stage detection algorithm, which provides additional assurance that the pig has safely passed the location in question – it does not signal a PIG PASSAGE until the required flux level has been detected and has dropped by a preset amount. This can be critical to ensure all pigs are launched or received, thus preventing lost time in over pumping or having to use other means to identify where a pig is. If the receiver is subsea, a magnetic subsea signaller with an acoustic link allows the vessel to ‘listen’ for the pig receipt, meaning an ROV does not need to be positioned at the receiver, providing both assurance and cost saving flexibility.

In certain circumstances, pre-deployment testing should be carried out, for example where the design of the pig, due to pipeline geometry, means that comparatively small (and consequently less powerful) magnets are fitted and/or the wall thickness of the pipeline is particularly ‘heavy’.

This can be performed simply by using a mandrel with the appropriate magnets fitted (or even the pig without the discs) and then pushed/pulled through a pipe section. The user can set up the correct threshold using Online’s data review capability and thus maximise the equipment capability for the task at hand by optimising the settings for use.

For an added level of confirmation, the exact location of individual pigs can be confirmed using a pig locating system such as Online’s EMTx Multi-frequency Transmitters and EMRx range of receivers and associated software, allowing the operator to promptly move on to the next stage of the precommissioning process.

Confirming a stationary pig in the receiver is a relatively routine task but locating a pig at an

Figure 1. 4000SD Subsea Magnetic signaller deployed on an ROV cradle.

Figure 2. Electromagnetic receiver software facilitates the pig locating process.

Figure 3. EMRx Subsea – diver or ROV held multifrequency receiver.

unknown location, although not commonplace, is more as Online’s Gauging Run Integrity Data (GRID®) system. The problematic and could have severe cost implications, GRID transducer monitors the condition of the gauge plate particularly for subsea operations. With an EM system, and reports this information remotely by transmitted coded detectability can be improved by considering, prior to pulses. These pulses are decoded using dedicated software project commencement, factors such as pipeline diameter, and will provide information on whether the gauge plate wall thickness and pig design and transmitter parameters is a ‘PASS’ or ‘FAIL’ along with the time that any defects such as output power, pulse rate and length and frequency. occurred. When compared with pumping data, this can give These parameters can all influence the detection envelope an approximate position of the defect without the added of the transmitter and the time taken to locate the pig. time and expense of a caliper pig run. Additionally, this

In a recent project, Online was able to trial a five assurance can be received without having to recover the pig pig train in a 13 m, 36 in. nominal bore pipeline with a to inspect the gauge plate, meaning that the operator can wall thickness of 31.8 mm. The five EM transmitters were immediately start the hydrotest. installed inside a dummy pig mandrel within the pipeline and each transmitter was configured with a different frequency. The main objective was to guarantee the maximum signal levels at the launcher and receiver, and prevent signal loss in case the transmitters were required as a contingency. Put With the optimum frequency arrangement, customised pulse rates and power output and the Down battery life being equal throughout, the receiver was able to detect the maximum signal level without turning the gain too high and Your running the risk of saturation or noise interference. Gauging Work During flood, clean and gauge operations a gauging pig is often used to evidence the pipeline is laid according to the relevant standard. Gloves. A standard gauging pig will advise you of the presence of a pipeline (We’ve got this.)‘intrusion’ – likely due to a problem experienced during lay, or a freespan that could lead to the necessity Maintaining a pipeline is no easy task. With so many things to worry of running a caliper pig to obtain about, you need products you can depend on. Always. Our solid-state additional information on the decouplers help improve your cathodic protection system’s performance position and type of defect before and stand up to AC faults and lightning strikes, in all sorts of conditions. you can perform the necessary We make them rugged so that you can trust them to perform. Always. repair. Unscheduled operations of this nature are clearly expensive Applications Include: and all mitigation methods possible • AC Voltage Mitigation should be considered. In the event of no pipeline intrusion, the gauging pig still must be recovered to obtain • Insulated Joint Protection • Decoupling Equipment Grounding Systems • Gradient Control Mat Isolation this information, an operation that requires valuable vessel time. Learn more about our

An alternative and potentially Always Rugged Promise: more cost-effective solution is to Dairyland.com/AlwaysRugged run a gauging system that includes a connection to an acoustic pinger or electromagnetic transmitter such

Figure 4. 6000SD displaying status of a 24 hour hydrotest.

Figure 5. MEG ARTS Analyser and Sampler – confirm successful pipeline conditioning in real-time.

Hydrotest As is the case with the flood, clean and gauge phases, the aim during the hydrotest is to receive assurance of a successful test and to quickly move on to the next stage, whilst minimising vessel time and costs.

Online’s 6000SD monitors, displays and records pressure and temperature data that can be observed for changes by an ROV or diver viewing the display, or by remote communication using an acoustic pinger, data transducer or strobe. In this way a vessel does not have always have to be on-hand but can still monitor the progress of the hydrotest.

As the unit is logging the pressure and temperature information, the ROV, vessel or diver can perform associated tasks in parallel. This results in accelerated completion of work and potential cost savings and project flexibility.

Additionally, the 6000SD can autonomously examine the data obtained in a set ‘test period’ such as 24 hours and display the time and date at which the hydrotest passed. Recent advances in technology mean that the data is continually monitored by the 6000SD firmware to match the client’s acceptance criteria, whether that is the pressure has remained above the threshold (for the expected time period), or that less than the permissible pressure decrease has occurred over the selected time period.

Another advantage of using a pressure and temperature logger is that a successful hydrotest can be confirmed by one of the methods discussed above without needing to recover the unit.

Dewatering

Critical pipelines, typically those that transport gas, are often dried and conditioned with monoethylene glycol (MEG) in readiness for hydrocarbons. Obviously, a pipeline is only conditioned correctly if conditioned throughout.

Verifying this can be a time-consuming process and it is often close to the start-up of hydrocarbon production and transportation, hence real time assessment of, and confidence in, dryness is critical. A lack of real-time readings and the reliance on theoretical data and/or analysis of sampled MEG carries associated vessel time and cost. Online’s MEG ARTS®

Analyser and Sampler measures the density of flowing

MEG (or other chemicals) at the receipt end of the pipeline and displays and logs this data along with pressure and temperature. This provides a real-time account of the progress of the dewatering operation and conformance with project purity, dryness or hydrate suppression requirements. Most importantly it verifies that MEG has conditioned the entirety of the pipeline, providing assurance that the planned pipeline integrity programme can commence once hydrocarbon transportation commences. The operator may still wish to receive samples for an additional level of validation or as supporting evidence alongside the logged data. Up to seven samples can be taken by ROV from specified positions in the train with a single switch, without the need to move between different valve locations. When practical, there is an opportunity to reduce costs further by taking automatic samples at predetermined density levels. This eliminates the need for a vessel at, or transit to, the receipt location.

Assurance By definition, assurance means ‘a positive declaration intended to give confidence; a promise’. In time critical schedules with multiple challenging activities ongoing simultaneously, assurance is more important than ever. Using as many positive assurance steps as possible in any process is sensible, however they must be practicable and a good use of time. Recent and imminent developments in equipment for subsea precommissioning have met this challenge.

Each project has its own conditions and requirements, occasionally needing custom designed solutions to achieve the necessary level of assurance. With an experienced in-house R&D team and a commitment to continual innovation, Online Electronics has the capability to undertake bespoke projects and the flexibility to modify existing equipment to suit client specific needs.