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Standardization for Oil Water Separator (OWS) and Oil Content Monitor (OCM) Systems In-Service Engineering Agent Perspective. December 2009 Presented to: ASTM F25 Environmental Seminar Presented by: Ray A. Morales US NAVY (NSWCCD).
Presented to: ASTM F25 Environmental Seminar
Presented by: Ray A. Morales US NAVY (NSWCCD)
Provide technical support to the fleet for the in-service Oil Pollution Abatement (OPA) system including OWS, OCM, and transfer system.
Test and Evaluation
System Certification and Training
Provide support for the acquisition programs
Design and Specification reviews
Navy Ships are considered public vessels
Department of Defense (DOD 4715.6-R1)
Office of Chief of Naval Operations Instruction (OPNAVINST 5090.1C)
American Bureau of Shipping (ABS) Naval Vessel Rules (NVR)
USCG (Title 46 CFR Part 162.050 - Pollution Prevention Equipment)
International Maritime Organization (IMO) ( MEPC.107(49) )
ASTM F2283 “Standard Specification for Shipboard Oil Pollution Abatement System”
Provides general design requirements
Refers to MEPC.107(49) for OWS and OCM requirements.Standardization for Oil Water Separator (OWS) and Oil Content Monitor (OCM) Systems
Capital costs of unique systems
Lack of Standards to ensure performance, reliability, and maintainabilityStandardization for Oil Water Separator (OWS) and Oil Content Monitor (OCM) Systems
Case Study –
Testing of Commercial off-the-Shelf (COTS) MEPC. 107(49) Certified Oil Content Monitors (OCMs)
To conduct laboratory testing of selected IMO MEPC 107(49) certified COTS OCMs to evaluate their performance under various operating conditions and in the presence of contaminants to determine if these units would be suitable for shipboard use in Navy vessels based on direct comparison with the in-service OCM unit.
PRESSURE RELIEF VALVE
PRESSURE GAUGE / TRANSDUCER
CONTAMINANT INJECTION SYRINGE PUMP
OIL INJECTION SYRINGE PUMP
5 Micron Filter
TAP WATER FEED
0.5 Micron Filter
Sediment Pre-filterTesting of MEPC. 107(49) Certified COTS OCMs
General checks to determine installation/ interface requirements and to ensure that OCM and testing equipment are operational
To verify OCM calibration at 0 PPM, 15 PPM and maximum oil concentration that the OCM can measure
Oil Droplet Size Distribution Test:
To determine deviations of the OCM calibration due to variations in oil droplet size distribution
Flow/Pressure Range Test
To determine deviations of the OCM calibration within the design Flow rate and Pressure Ratings and to determine if the OCM is fail-safe beyond the design flow/pressure range.
Temperature Range Test
To determine deviations of the OCM calibration within the design temperature Range.
Different Oil Types Test
To determine deviations of the OCM calibration in the presence of different types of oils (i.e., the oil mix# components separately; DFM, 9250, 2190, JP-5 and Synthetic oil)
Response Time Test
To determine time required by the OCM to alarm once high oil content is present.
Contaminant / Interferences Tests (color, air, solids, emulsions, salinity) – Decision Making Test
To incrementally change each given parameter to determine at which point: (1) The OCM measurements are affected and (2) The OCM decisions are affected (i.e., allows overboard discharge or recycle to the oily waste holding tank)
The COTS OCMs tested failed to detect free oil, failed to accurately measure oil under the conditions expected in the effluent of a failing OWS treatment system and required highly mechanically dispersed oil for accurate measurements.
The COTS units tested produced critical failures (would allow overboard discharge of > 15PPM oil-in water), with and without interferences/contaminants, when tested under the conditions expected from a failing OWS treatment system .
COTS units tested did not accurately measured different types of oils (affected calibration)
Then COTS units tested required significant routine maintenance to keep operating properly. The sampling cell of the COTS units were cleaned between tests to ensure a zero baseline and prevent drift in the readings.
Response time results were not consistent with requirement (e.g., < 5 secs)
COTS units tested did not provide for “Fail-safe” design:
Continued operation even with no flow allowing “by-passing” the OCM while the data recorded shows acceptable effluent. This could allow continued operation of OWS even with unacceptable overboard discharge while zero (0) oil PPM is recorded.
Design does ensure diverter valve default position to recycle during all possible failures modes
COTS units tested were designed and calibrated to meet MEPC.107(49)
Test Results/ FindingsOil Droplet Size Distribution Test (Disperser’s settings)Oil Droplets Micrographs: 15 PPM oil injection at 8,000 RPM Disperser’s Speed (Standard Conditions)Testing of MEPC. 107(49) Certified COTS OCMs
Oil Concentration, PPMv
2190 lube oil
9250 lube oil
Different Types of Oils
OCM 1 @ 8k RPM
OCM 1 @ 12K RPM
OCM 2 @ 8k RPM
OCM 2 @ 20k RPM
OCM 3 @ 8k RPM
OCM 3 @ 22K RPMTesting of MEPC. 107(49) Certified COTS OCMs
Target Response Time, 5 secs
Required by MEPC.107(49)Testing of MEPC. 107(49) Certified COTS OCMs
Test Results/ Findings Contaminant/Interference/Salinity Test – Summary
The Navy in-service OCM was not affected by the presence of interferences/ contaminants at low concentrations. It produces unnecessary recycle at high concentrations of these interferences/contaminants and “fails safe.”
The COTS unit tested produced critical failures with and without interferences/contaminants when tested under the conditions expected from a failing treatment system.
The COTS unit tested was not significantly affected by the presence of interferences/contaminants when the sample was conditioned at very high disperser’s speed.
OWS and OCM
Revise ASTM F-2283
Different Type of Oil test
Reliability and maintainability
Free oil and droplet size distribution tests
Fail-safe designTesting of MEPC. 107(49) Certified COTS OCMs
Test Set-up is shown in next figure
Baseline - Navy OCM calibration standard conditions:
Mixture by vol 50% diesel fuel, 25% 2190 lube oil, 25% 9250 lube oil (used for years as standard in all Navy testing)
In-line disperser set at 8,000 rpm to produce approximately 20% oil droplets above 20 um diameter (expected in the effluent of a failing parallel plates OWS)
Performance results from the in-service OCM unit
OCMs tested within a range of various operating conditions, oil types and contaminants/ interferences
Oil concentration was determined by mass balance of oil injected into the water stream
Notes: (1) Standard disperser’s speed (8k RPM).
(2) maximum disperser’s speed
(3) OEM of COTS units indicated that their units were calibrated to meet the MEPC. 107(49) and that
recalibration will invalidate this certification
Critical Failure - >15 PPM Overboard Discharge
The COTS OCMs tested failed to detect free oil, failed to accurately measure oil under the conditions expected in the effluent of a failing parallel plate OWS, and required highly mechanically dispersed oil for accurate measurements
These OCMs were not designed to condition the sample
The accuracy of these units will depend on the sample conditioning of the secondary treatment effluent
These units may produce unacceptable overboard discharge if the failure of the treatment systems produces large oil droplets (e.g., cracked membrane, etc.)
The measurements of the OCMs tested were not significantly affected by variations in pressure or temperatures
The measurements of all the units tested, including the In-service OCM, are dependent on the type of oil present.
The response times of all the MEPC. 107(49) Certified OCMs tested exceeded the maximum of 5 seconds required for this certification (e.g., 11 to 43 seconds)
The ET-35N was not affected by the presence of interferences/ contaminants at low concentrations. It produces unnecessary recycle at high concentrations of these interferences/contaminants and “fails safe.”
The COTS unit tested produces critical failures with and without interferences/contaminants when tested under the conditions expected from a failing parallel plate OWS
The COTS units tested were not significantly affected by the presence of interferences/contaminants when the sample was conditioned at very high disperser speeds.
OEM of COTS units indicated that their units were calibrated to meet the MEPC.107(49) and that recalibration will invalidate this certification.
The sampling cell of the COTS units were cleaned between tests to ensure a zero baseline. These units may require self-cleaning capabilities for proper operation.
COTS units continued operation even with no flow allowing “by-passing” the OCM while the data recorded shows acceptable effluent.
COTS units do not provide signal output to energize the diverter valve when the OCM is operational and readings below 15 ppm as required for a “fail-safe” installation.
Performance and reliability shipboard demonstration should be conducted prior to considering these units for shipboard installation.
Integration requirements should be developed to ensure that the “fail- safe” intent is met if these units are considered by the Navy for shipboard use:
Diverter valve “Fail-safe” requirements
Diverter valve position to overboard only when received signal from OCM.
Default position of the diverter valve shall be to the OWHT when
Normal de-energized position
No signal input from the OCM
Electrical power supply failure
OCM signal output “Fail-safe” requirements:
OCM shall have consecutives acceptable readings for at least 1 minute prior to send signal to the diverter valve to:
Verify that the effluent is acceptable prior to being sent overboard.
To avoid constant cycling of the diverter valve that can result in unacceptable overboard discharge and valve failure.
OCM signal shall be immediately interrupted if any reading is unacceptable
The units tested use some variation of light scattering technology. Other available technologies such as UV fluorescence should be evaluated.