1. Calibration Stand Update
Calibration of Liquid Density Meters at Combined Temperature & Pressure
Calibration Stand Update
Tony Wright
Customer Services Manager

2. Agenda Background Project requirements Calibration Process
Current status
Test plan
New equations
Calibration approvals
Calibration of customer’s 7835’s
Summary

3. Background for New Calibration Strategy
DECC (Department of Climate Control) in the UK requested all densitometer manufacturers and Oil companies in the North Sea to launch a project “JIP” (Joint industry project) to understand the behaviour of temperature and pressure effects on Liquid Densitometers and to develop a new calibration strategy.
TUV NEL ltd, as an independent calibration facility, were contracted to test and validate Liquid Densitometers at combined temperature and pressure. The calibration facility used 4 transfer standard fluids across the temperature range from 20⁰C to 100⁰C and from atmospheric pressure to 100 bar.
From the NEL testing, it was concluded that there is combined pressure and temperature effect during elevated temperature and pressure operating conditions which need to be taken into density calculations.
DECC then released an instruction stating that Liquid Densitometers should be calibrated at their anticipated operating conditions, i.e. simultaneously at temperature and pressure, using one or more transfer fluids, the density of which has been determined across the required temperature and pressure range with an uncertainty not exceeding 0.01%, directly traceable to national standards.

4. Project Requirements Objective and Scope
Provide a production calibration stand(s) for combined temperature/pressure density calibrations.
3 different fluids:
Silkospark (current Slough calibration fluid [machining fluid] ~ 825 kg/m3)
Sebacate (~960 kg/m3)
Sodium Bromide – (~ 1400 kg/m3)
Combined P+T for two fluids (Silkospark, Sebacate) at
20°C – 0,50,100,150 bar
80°C – 0,50,100,150 bar
20°C at 1 bar A calibration on Sodium Bromide (stand to be capable of combined P+T if required)
Double capacity of current calibration stands

5. Calibration Process Flow
Steve/Bob to provide flowchart of calibration steps for various options

6. New Stands Schematic Overview

7. Current status Original promise date July 2011
Slippage due to:
Damage in shipping
Design changes during testing
Pressure test rig commissioned
Cleaning station commissioned
All calibration stands fully functional
Modifications completed
Testing and commissioning re-started
Similar system under test in MMI Boulder

8. Pressure Test and Cycle Hydro Stand
Hydrostatic pressure test rig
Rig will be used on all new and repair 7835’s to:
Pressure test each sensor to 1.5 maximum operating pressure
Pressure cycle each sensor for 30 times to maximum operating pressure

9. Cleaning Station Designed to flush out calibration fluids
Up to 3 x 7835’s each cleaning session
3 stage cleaning process

10. Liquid Density Calibration Stands Combined Pressure and Temperature

11. Test Plan Stability and repeatability tests on distilled water
Change water to calibration fluids
Repeat stability and repeatability tests
Monitor for cross contamination
Validate calibration results against
Engineering Dept combined P+T calibration stands
Current production calibration stands
UKAS laboratory (also monitor contamination of fluids)
Send fluid samples to external UKAS Laboratory to determine effect, if any, of contamination

12. New Density Equations All major flow computer manufacturers contacted
Existing format certificates will continue to be available for limited pressure and temperature ranges
Dp = Dt * (1+K20*(P-1)) + K21 * (P-1)
K20 = K20A + K20B*(P-1) + K20C*(P-1)^2
K21 = K21A + K21B*(P-1) + K21C*(P-1)^2
Dpt = Dp * (1+K22*(t-20)*(P-1)) + K23*(t-20)*(P-1)
K20A,K20B,K20C,
K21A,K21B,K21C
Calibrate on new calibration stands on 2
fluids at 20
°C for each unit
K22, K23
Calibrate on new calibration stands on 2 fluids at elevated t&P for each unit
Optimum Solution
Equations
New calibration stands

13. Calibration Approvals
Our current ISO17025 (UKAS) calibration laboratory has been in operation since 1981
20 Deg C and 1 Bar A
Will apply for ISO for new stands
Traceability through current UKAS Laboratory
Liquid P+T via 3rd party approved laboratory
Planned schedule for approval application is 6 months from release of calibration stands
On receipt of approval, we will apply for MID approval using new stands

14. Re-calibration of Installed 7835’s
All installed 7835’s can be re-calibrated on the new stands to DECC requirements
7830’s are not supported
Fiscal (Micro Motion business partner) has built and installed a new 7835 cleaning facility
Operational from December 2012
Over-check to include air-check and detailed visual inspection prior to despatch to MMI Slough

15. Summary Functional testing of complete system has started
Calibration stands will be fully commissioned by mid January 2013
Existing stands will then be decommissioned
Stands are designed to fully comply with DECC requirements
Plan to have new calibration stands approved to ISO by mid 2013