Working Group on Unexpected Effects and Countermeasures
Leif Vinnogg, Norconsult, Norway
Hydraulic Performance Testing can be viewed as a non-routine operation because it differs from normal plant activities. Special situations can arise that require problem solving on-site. Therefore, careful planning is required before testing. Some examples of unexpected effects that might be encountered during performance testing and possible countermeasures are provided below.
Classifications of Effects
Debris, sedimentation, and ice can float to the trashracks causing blockage which may distort the velocity profile. One countermeasure is choosing an appropriate season for testing when it is known that there is less debris in the reservoir. Seasons when the water level is lower generally results in less floating debris than higher water periods. Usually the station operators have knowledge of the reservoir levels and the likelihood of significant debris. Another countermeasure is scheduling 'clamming', or trashrack debris removal, before testing. Grass and other fibres can be a problem for current meters. Walki-talkies and cellular phones can cause spikes in electronic recordings.
Anomalous readings from equipment, such as spikes in pressure, temperature, power, etc., may be caused by electrical problems usually related to grounding. A possible countermeasures aside from proper electrical connections is screening the data.
Drawings of the station, upon which the testing frames/carriages are designed, sometimes are not available or are not accurate. This can cause the equipment to get stuck during use, or the equipment may not fit at all, resulting in a costly delay. A countermeasure would be to measure site dimensions and test the equipment in advance of the formal testing program.
Pressure taps can be clogged. It would be useful to check them for proper operation before starting the testing program.
Performance testing can require additional temporary manpower. The availability of manpower at remote sites, as well as the longer hours of work can be an issue. Possible countermeasures include establishing agreements with the workers that some overtime is required, and to hire workers familiar or experienced with the testing if possible.
An unexpected stoppage or delay of the testing program can be dictated by System Control, or the agency responsible for power sales. This is usually due to the value of energy outweighing the cost of demobilizing and remobilizing the testing equipment and personnel. A possible countermeasure might be utilizing a business case based on costs, or accommodations for performance testing during planning of scheduled outages.
Safety is becoming one of the highest priorities for energy companies. This can change the way things are done. As an example related to the use of current meters, when the covers are removed from the stoplog gains, the opening has been identified as a potential fall hazard at Manitoba Hydro. Therefore, as a countermeasure, temporary covers over the openings are required until the testing equipment is placed over the hole.