|
7 Test Procedures
The following sequence of actions in the skimmer testing process is recommended:
7.1 Prior to testing
Preparations prior to testing:
| a) |
Prepare the required quantity of the test oil. Control that
the oil properties are within the ranges specified in Table 2 at the test temperature.
|
| b) |
Take samples of the test oil for subsequent analysis and documentation.
Measure oil properties as described in Section 10.1.
|
| c) |
Ensure that the water in the test basin is at the required
temperature
|
| d) |
Install the boom in the test tank.
|
| e) |
Locate skimmer inside boomed area. Ensure that the requirements
with respect to clearances specified in Section are met.
|
| f) |
Start the water current and allow sufficient time for it to
stabilise at the desired current velocity (Table 2)
|
| g) |
Preload the tank with the test oil until the desired thickness
(Table 2) is obtained at the prescribed location upstream of the skimmer inlet
(see section ). Register the location of the leading edge of the
slick (length of the slick). |
7.2 Testing period
Actions during the testing period (Reference is made to Figure 1):
| h) |
Start the skimmer and adjust the operating parameters to desired
settings (speed, draft, etc).
|
| i) |
Start the pump to offload recovered product from the skimmer
sump (if applicable). The fluid level in the sump should be constant to prevent
skimmer draft variations. Direct flow to the Recovered Fluid Tank
|
| j) |
Concurrently with the previous two steps, start the oil distribution
mechanism and adjust it to maintain the oil slick thickness at the measuring location
ahead of the skimmer (Section). During periods between measurements,
slick thickness may be approximately controlled by maintaining the location of
the slick's leading edge (see Appendix 1).
|
| k) |
When steady state is achieved, divert flow of the recovery
fluid to the first measuring Tank and maintain for the desired collection period
or until the desired volume is collected (see Section 9.1). Register time for
start of measuring period.
|
| l) |
Throughout the testing period, regularly monitor and control
slick thickness and skimmer operating settings. Record any deviations from the
desired test conditions.
|
| m) |
Once the measuring period is ended, divert flow back to the
Recovered Fluid Tank. Register time for the end of measuring.
|
| n) |
Provided that steady state is maintained, divert the recovery
flow to next measuring tank.
|
| o) |
Repeat points k to m for all measuring tanks.
|
| p) |
Stop oil distribution |
1. Stop skimmer operation
7.3 After testing
Actions after testing:
| q) |
Let the recovered fluid in the measuring tanks settle for at
least 15 minutes.
|
| r) |
For each measuring tank record: total fluid quantity, quantity
of water, and quantity of oily phase.
|
| s) |
Take at least three samples of the oily phase from each measuring
tank for subsequent analysis.
|
| t) |
Measure and record the water content in the oily phase samples
|
| u) |
Calculate performance parameters as given in section 8. |
8 Performance parameters
Performance of the skimmer should be defined by the following parameters:
- Fluid Recovery Rate (FRR)
- Oil Recovery Rate (ORR)
- Recovery Efficiency (RE)
- Emulsification Factor (EF)
Fluid Recovery Rate (FRR)
The total amount of fluid recovered (in m3)divided by the duration of the data collection period (in hours).
Oil Recovery Rate (ORR)
The total amount of the test fluid recovered (in m3) divided by the duration of the recovery period in hours. The ORR must be adjusted for additional water mixed into the oily phase in the recovery process (emulsification factor).
ORR applies to emulsions as well as fresh oils, since the additional water emulsified into the oil is subtracted
Emulsification Factor (EF)
The Emulsification Factor is a measure of the tendency of the skimmer systems to form emulsion and is defined as the increase in water content (emulsified) in the recovered oil compared to the original test fluid. EF is expressed as a decimal fraction between 0 and 1. The emulsification factor is a function of the test oil properties as well as the skimmer, and comparisons are only conclusive for tests with similar oils.
Oil Recovery Efficiency (RE)
The Oil Recovery Rate divided by the Fluid Recovery Rate expressed as a percentage.
9 Quality control
9.1 Test duration and fluid volume
The test measuring periods (period that recovered oil is collected in measuring tank) should be of sufficient duration to: i) even out possible variations in test conditions during the measuring period; ii) provide sufficient volume of recovered product to allow accurate reading of both oil and water volumes, iii) allow sufficient time for necessary registrations and measurements throughout the measuring period.
Table 1 specifies minimum measuring duration and oil volume for different skimming capacities (FRR). The table assumes 50% skimmer efficiency (RE). For more efficient skimmers, the volume may be reduced, while skimmers recovering more water should be subjected to longer measuring periods. Fluid volume should always exceed 0.5 m3 and the minimum test duration should be 1min.
Table 1 Minimum fluid volumes and duration of test
periods (per measuring tank)
Expected
FRR(m3/h) |
Minimum fluid volume
(m3) |
Min. measuring period
(min) |
| 5 |
0,5 |
6 |
| 10 |
0,5 |
3 |
| 20 |
0,5 |
1,5 |
| 50 |
0,8 |
1 |
| 100 |
1,7 |
1 |
| 150 |
2,5 |
1 |
| 200 |
3,3 |
1 |
| 300 |
5 |
1 |
|
9.2 Repetitions
At least three measuring tanks must be used to provide consecutive measurements for the same test conditions. The complete test should be repeated with three new measurements if: i) the standard deviation of the ORR is more than 15% of the mean; or ii) if test conditions were observed to significantly deviate from desired test conditions during the test period.
Individual tests should be rejected (not be included in performance data) if: i) test conditions were observed to significantly deviate from desired conditions during the measuring period; or ii) the test ORR deviates more than 20% from the mean ORR.
|
