BP Experiences Guided Wave Radar Level Instruments

1
BP Experiences -- Guided Wave Radar Level
Instruments

• Rick Stanley
• API 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 havent 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 arent 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
11
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 dont have
  platforms
• View of heads is limited or not possible
  operations hasnt 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
• Manufacturers programs
• AMS or similar systems

15
We Know What These GWRs areDoing -)
16
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 arent 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 doesnt 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