Case Study

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Using ID5000 Active Ultrasonic PIG Signaller to Locate PIG

Problem

We have been asked by a client to find a non-intrusive method of locating a ‘stuck/stalled’ foam pig on an onshore facility.

Method & Objectives

Online Electronics proposed the use of the ID5000 ACTIVE Ultrasonic ATEX topside pig signaller /locator to give an indication of pig’s location.

The ID5000A is designed to sit statically on the pipeline with the purpose of signalling pig passages by sending a high frequency ultrasonic pulse through a liquid pipeline medium several times a second, this pulse creates an ultrasonic ‘beam’ along the pipeline by reflecting off the opposite side of the pipe wall. Once this beam is broken a passage is signalled.

This beam can also be used to measure the internal pipe diameter by measuring pulse widths transmitted and received.

By viewing the live display (below) a visual representation of the pulses can be viewed and analysed to give an accurate indication of any object within the pipe, eg discs on a hard bodied pig, or a foam pig.

If the ‘spikes’ shown at 31cm (in this example) disappear then there is no reflection from the back wall and so with care and a skilled operator the unit can be used to find a pig.

When pipe is clear, a reading of the full Internal Diameter is given. 

When placed at the 12 o’clock position the sensor will give a measurement of the clean space above any debris that has collected at the bottom of the pipeline – allowing for a calculation of the ‘settled debris’ in the line.

The pig blocks the signal giving NO response and so signals the pig’s location.

Solution

The system was used to pinpoint the exact location of a pig in a receiver known to have high quantities of wax present. This wax build up was blocking the receiver and raising concern that the rear of the pig had not cleared the main isolation valve.

As per the image below, the front of the pig was located 4.1m from the Receiver door. A reading was taken behind the pig which confirmed that the line was clear, giving a reading consistent with the ID of the pipeline.

When a reading was taken in front of the pig, the back wall of the pipeline could not be seen giving a reading of 0. Once the receiver door was open it was found that a build up of debris and wax had been collected by the pig and was blocking the signal from the ID5000A transducer.

The results of the OEL survey were corroborated by a later survey conducted by a radiograph of the receiver. The results of this survey are below

 

During the pig location exercise at terminal, OEL was requested to inspect the kicker line for any debris build up.

The kicker line was inspected at 17 different points, each ~0.5m apart. Results are outlined in the below graph.  

Data points were taken both horizontally (to determine pipeline diameter) and vertically on the pipe in order to determine the level of debris settled at the bottom of the pipe.

The Kicker line was found to be free of debris for the first 0.5m of the line. Our operator was unable to find a signal at the one metre mark due to lack of access. Large amounts of debris were recorded up until the 5.5m mark whereupon the level of debris was significantly reduced.