BP Experiences -- Guided Wave Radar Level Instruments

Rick StanleyAPI SOICS April 2008

2

Overview

• BP Inventory

• Overall Experience

• Design and Operation Issues

− Configuration

− Off Normal Behavior

− Physical Design

• Wish List and Path Forward

3

BP Inventory

• Guided Wave Levels used at all 5 BP US Refineries

− Whiting – 75

− Texas City – 50+

− Cherry Point – 40+

− Carson -- 60

• Services

− Propane storage bullets

− Cooling towers

− Process levels

− Interfaces

• Overall experience is good, but there are problem applications

− Configuration issues

− Post startup adjustments

− Consistency and reliability of measurements

4

Understanding Configuration

• Many Choices – difficult to make the right ones

• Manufacturer guidelines haven’t been that effective

− Contractors incompletely specify configuration

− Deeper understanding of application requirements

• Understanding of what the choices mean and how they interact is experience that we are only now getting

• Some areas of difficulty

− Null zone and hold off

− Dielectric selection

− Thresholds

− Out of range behavior

− Fault behavior

5

Some Real Examples

• Carson 2008 Turnaround – Installed about 40 Guided Wave Levels

• Shop testing – water fill

• Manufacturer tech support on site multiple times

• Some installation difficulties

• Several head swaps prior to startup

• Despite a lot of effort, we were adjusting things prior to and during startup

• Post TAR – Almost all GWR are reading OK and are stable – but it took a lot of work to get there

• We seem to have more difficulties than TxC and Whiting have had, but distance has a way of dulling experiences. Everyone has successes and problem applications

6

Hold Off, Blocking Distance and Null Zone

• Several heads had to be remote mounted due to clearance

• Extension of cable from probe to head lead to mis-interpretation of parameter adjustments required

• Initial operation resulted in end of probe not detected faults

• Faults forced output to 100% even at zero level

• Consultation with factory resulted in correction of parameters

• Problem was fixed, but at cost of operations confidence

• 3 Services with dual GWR – pulled one and replaced with DP

7

Dielectric

• Instruments require careful dielectric selection – process design basis may not be right

• Example -- DEA contactor

− Instrument set for high dielectric (water based)

− During startup hydrocarbon overfill into DEA contactor

− Magnetic float indicated 4”, DP indicated 30” and guided wave indicated 0.

− Guided wave had been indicating up until hydrocarbon carry over

− Corrected dielectric for hydrocarbon – revealed actual level of about 50”

− Left at hydrocarbon dielectric and seems to be working since

• Similar issues to be expected in flare KO drums and similar places why water and hydrocarbon may exist

8

Trend of Hydrocarbon onto DEA

9

Threshold

• Appropriate thresholds for detection of level surface aren’t always constant

• Auto-sense functions can lead to erroneous levels

• Hydrocarbon level in flash drum

− Guided wave and through the air radar tracked very well

− Guided wave went to 100% - Investigation found that threshold had been lost. Reset to manual threshold and they have been tracking since

• Empty Drum

− Threshold set to automatic – result was spikes in level even though drum was empty

− Set to fixed threshold, but still having issues with empty drum

− Had to adjust thresholds differently on parallel services

10

Hydrocarbon – GWR vs. Through Air Radar

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Out of Range Behavior

• Experiencing problems with instruments when level is outside probe range

• Want signal to stay at 0% when level falls below probe or configured range and 100% when level increases beyond probe or configured range

• Having difficulty getting reliable behavior in empty vessels

• Instruments appear to be going into fault, which drives the signal to its configured fault output – this means a low level can indicate as a high level

• Need reliable and predictable out of range performance.

12

Installation

• External Chambers

− GRW manufacturers were generally not planning on getting into the chamber business.

− Users view has been to buy these like displacers – complete assemblies with chambers

• Attempts at response have been mixed. Design development and fabrication quality

− Materials

− Basic design

− Welding quality

• Recent projects have resorted to piping fabricators or local fabrication

13

Installation

• Guided wave installations often don’t have platforms

• View of heads is limited or not possible – operations hasn’t been happy about that

• Need a means of relocating display to grade without affecting radar path

• Long rods are subject to being bent when being removed or re-installed.

14

Documentation

• Guided wave specific specification form

• Baseline configuration for common applications

− Hydrocarbon level

− Mixed service level

− Interface

− Water

− Dry vessel

• Configuration data storage

− Manufacturer’s programs

− AMS or similar systems

15

We Know What These GWR’s areDoing :-)

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Wish List – Path Forward

• Use of GWR has generally been quite successful and well accepted

• Some services still need work and have impacted the attitudes of those who own them

• Effectiveness of manufacturer support is still spotty

− On site support is needed for commissioning of any quantity

− Even with on site support we have still had performance issues

• Successful implementation requires careful attention to device applications and post startup review and adjustment. Not particularly tolerant of error. Right now the commissioning labor per installation is high

• Steep learning curve, but we think we are over most of it.

• Still concern over some services, especially dry vessels or widely varying process conditions.

17

Conclusions

• Guided Wave Radars are not simple but they do work (eventually)

• They aren’t always predictable when first commissioned

• They take more work than Specific Gravity based devices

• We will be developing much more defined practices

− Specification and configuration requirements

− Checkout and commissioning procedures

• We will continue to use the technology, but will run into resistance if we try to eliminate traditional SG based devices

− Operations doesn’t always understand SG devices will be inaccurate

− But….. It does give them a signal even if its wrong.

• It will take time to develop comfort that people have with the old technologies