ndt intelligent pigging

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100% CRUDE HEATER TUBE THICKNESS SURVEY USING

INTELLIGENT PIGS TECHNOLOGY (MERLIN INSPECTION

TECHNOLOGY)

Fallatah, Mousa Mohammad

Inspection Engineer

Yanbu refinery

Saudi AramcoYanbu Industrial CityP.O. Box 30028

E-mail: [email protected]

ABSTRACT: For the first time and since commissioning in 1983, both Crude heaters in Yanbu Refinery had been

subjected to 100% tube wall thickness scanning. Non-reachable areas such as convection sections had been checked

and found to be in good condition. The MIT technology uses a smart intelligent pig which is driven throughout the

tube using a pressurized water flow. Generally the result was satisfactory and a clear picture on tube integrity had

been achieved.


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1. INTRODUCTION:The MERLIN INPECTION TECHNOLOGY (MIT) is one of the available technologies for

heater tube thickness and condition survey. Intelligent pig is introduced into heater tube after

decoking is completed and water is used as a driven media throughout the tubes. Measureddata is collected and down loaded into portable laptop. Collected data was analysis at the siteand initial result was reported.

Yanbu Refinery had contracted and used this technology during the 2011 total refineryturnaround. Decoking was performed at the first as part of MIT test requirement then

followed with 100% heater tube thickness and mechanical condition scanning.

Original plan is to conduct 100% tube scanning on both crude and platfroming heaters.However, due to the requirement of decoking and requirement to introduce water inside

heater tubes which is acceptable in case of platfroming heaters, the test was limited to only

the crude heaters.

2. BACKGROUND:There are two sets of crude heaters in Yanbu refinery and both are in operation since 1983.Internal inspection normally is done every five years and deferent types of conventional NDT

tests are performed such as heater tube wall thickness survey and RT profile shots.

For the first time, a complete thickness survey was carried out. The advantage of this surveyis, it covers all areas including the none-reachable such as straight tubes in the convection

section.

Both heaters are of box types with horizontal type orientation and four passes for each heater.

During past scheduled T&Is, an extensive spot UT reading are measured using convention

manual UT methods.Past histories show no significant wall thinning or damage. All pervious RT profile shots

show no significant coke scale inside the tube.There is no any UT data for the none-reachable tubes located into convection section or

covered by refractory.

During the 2011 TRS and for the first time, a full 100% tube scanning for both radiant and

convection sections were performed and full report on existing tube wall thickness weregenerated and made available with inspection.

3. DESIGN AND SPECIFICATIONS:Services: Crude Heater

Design Tube Wall Temperature: 593CDesign Pressure: 21.1 kg/cm2

Tube Material: A335-P9

Radiant Tube Thickness: 12.7 mmConvection Tube Thickness: 11.0mm

Radiant Tube Outside Diameter: 219.1mm

Convection Tube Outside Diameter: 168.3mmNo. of passes: 4 pass


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4. DECOKING PROCESS:There was no any need to perform decoking process on YRD crude heater becauseequipment history shows non-significant coke scale inside the tube. The crude oil processed

by YRD is light crude. There was no expected to have a significant coke scale.

Decoking was performed because it is part of MIT test requirement in order to remove anyscale which might affect the accuracy of wall thickness measurement. Figure 1 shows sample

of pigs that used for tube decoking.

As per decoking report there was a low to moderate amount of cocking scale. Total volumeof remove coke scale was 1 cubic meter and coke thickness of 1 to 2mm inside radiant tube.

FIGURE 1: sample of decoking pigs used for decoking process.


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FIGURE 2: flow of decoking water to potable tank.

5. INSPECTION:After completion of heater tube decoking process, intelligent pig was introduced into the tube

and extensive tube wall thickness measured was collected. The intelligent pig was driven by

flow of pumped water. Figure 3 shows photo of intelligent pig.

FIGURE 3: Intelligent Pig

Nondestructive ultrasonic testing was carried out by the latest generation MK III intelligent

pig on the Crude Heaters V04-H1- (A&B) in both 6-inch convection and 8-inch radiant

sections.The extensive amount of data recovered was judged to be accurate and consistent, from

which a detailed evaluation of the mechanical and physical properties of the furnace tubes

could be made.


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In general, the wall thicknesses of the tubes were well within our set tolerance, with minimal

wall thinning observed. Careful analysis of the as-obtained data has revealed little evidence

of internal or external corrosion on any section of tubing within the pass.The internal diameters measured were steady and consistent throughout the pass, with few

variations from the mean. No evidence of any significant bulging, creep or ovality was

observed in either heater.In general, all tubes were in excellent condition, with very little deviation from the designspecifications. This is indicative of the operating conditions under which the crude heaters

are run.

6. TYPE OF DEFECT CAN BE DETECTED BY MIT TECHNOLOGY: Actual UT thickness measurements with exact location. Internal tube diameter and if any change started. Tube bulging Creep Tube Ovality

7. CONCLUSION: Full picture of crude heater integrity condition was built and established. This technology is good tool to collect and measure tube wall thickness for none-

reachable areas.

The test proofed the effectiveness of the normal conventional NDT methods that beenlong time utilized to monitor the integrity of crude heater condition and changes thought

out it life.

One of the disadvantages of this technology is mandating of the decoking process andusing water to drive the smart pigs.


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8. INSPECTION REPORT:Flowing figures shows samples of inspection report received from the contractor.

FIGURE 4: YRD Crud heater tube arrangement


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FIGURE 5: number of heater tube


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FIGURE 6: summary report of heater tube wall thickness


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FIGURE 6: Heater tube wall thickness


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FIGURE 7: heater tube diameter change report

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