
Volcanic ash fall advice in HTML poster versions for:
- Advice for waste water-managers
- Advice for water supply managers
- Advice for roading managers
- Advice for airport operators
- Advice for power transmission and distribution system operators
- Advice for power plant operators
- Advice for facilities managers: buildings
- Advice for all facilities managers: gensets and HVAC
- Advice for facilities managers: computers and electronics
- Advice for urban clean-up operations
ADVICE FOR POWER PLANT OPERATORS
Volcanic ash is: hard, highly abrasive, mildly corrosive and conductive when wet.

Impacts on power generation facilities
General Impacts:
-
Flashover: Ash contamination of station and line insulators leading to flashover is the most common impact at power plants
- See companion poster “Advice for Power Transmission and Distribution System Operators”
- Step/Touch Potential: ash may reduce the resistivity of ground gravel cover, reducing tolerable step and touch voltages
- Disruption to Control Systems: ash ingress into heating, ventilation and air-conditioning (HVAC) systems can block intakes leading to reduced performance, and affecting dependent systems
- Structural damage: Very thick ash deposits (>100 mm) may create excessive loads on structures
- Long span, low pitched roofs are typically the most vulnerable
- When ash is wet, static loads may increase by up to 100%
- Internal gutters: may block with ash, potentially leading to water ingress to indoor electrical equipment.
Hydroelectric Power Stations
- Ash suspended in intake water can cause accelerated wear of hydroelectric turbines (e.g. runner blades, labyrinth seals, cheek plates and wicket gates)
- Hazard depends on volume of ash deposited in catchment, reservoir size, settling rate of ash, abrasiveness of ash
- Ash may also fill rain gauges in climate stations throughout river and reservoir catchments.
Thermal Power Stations
There are few case studies to guide possible impacts or advice.
- Ash may block air intakes for gas turbines and boilers, or sub-aerial condenser systems causing blockages, abrasion and creating cleaning difficulties
- Ash falls have created airborne particle concentrations of up to 9 g m-3, several times higher than dust- or sand-storms
- Mechanical seals may be vulnerable to abrasion and corrosion by ash
- Fine ash ingested into gas turbines may cause accelerated wear or melt on turbine surfaces (similar to an aircraft turbine)
- Ash may contaminate exposed surface water cooling reservoirs, potentially blocking heat-exchange systems.

Recommended actions
Where to find information
See www.geonet.org.nz for ashfall forecasts in the event of an explosive eruption.
How to prepare
At-risk power generation facilities should develop operational plans for ash fall events, including:
- Install turbidity monitoring instrumentation at intake and identify threshold for intake closure
- Priority schedule for inspecting/cleaning essential sites and components
- Site cleanup may be required following an ash fall. Cleanup plans should include:
- Standardised ash fall clean-up procedures, suitable to your local conditions and site
- Stock or have access to sufficient supplies and equipment for cleaning;
- Clean up and additional maintenance can create significant additional labour and resource demands
- Insulators usually require cleaning. See the companion “Transmission and Distribution ” poster and IEEE Std 957 “Guide for Cleaning Insulators”. Ensure that roofs and similar elevated areas where ash accumulation will need to be removed, have pre-installed fall arrest anchor points and that a safe means of access is identified
- Field crews should use safe operating procedures when operating in an ‘ashy’ environment. See www.IVHHN.org for guidelines for protecting people from ash hazards
- Transmission/distribution lines feeding the generation site may be disrupted and require additional planning – see “Transmission and Distribution ” poster
- Hydroelectric plant (HEP) facilities may consider hardening turbines during design and refurbishment programmes.
How to respond
- Consider increased inspection and preventative maintenance
- Seal key facilities to limit ash ingress.
- See companion “Facilities Managers: Buildings” poster
- Clean up site to reduce remobilisation of ash and thus recontamination of energised components. Use dry methods where possible
- Remove ash from gutters to avoid localised flooding
- Internal gutters may require suction cleaning
- Be aware of increased electrocution hazard if ash covers the ground. Isolate and earth energised apparatus before entering site
- Hydroelectric Power Plants : Monitor the suspended solid load in water intakes. Be mindful of volcanic debris flows (lahars). Consider by-passing turbines, if necessary
- Geothermal/thermal: assess ash hazard and consider shut-down if necessary.

More information
The following resources provide further information on volcanic hazards:
http://www.geonet.org.nz
http://www.gns.cri.nz
http://volcanoes.usgs.gov/ash/index.html
http://www.ivhhn.org
Based on diagrams drafted by Tom Wilson, Johnny Wardman and Carol Stewart, 20 September 2013
