GTEquiz4mod15.22 Engine Storage & Preservation PDF (CASA Part 66)

Engine Storage and Preservation (15.22) Learning Objectives 15.22.1 Describe preservation and de-preservation for a gas turbine engine and its accessories and systems (Level 2). 2022-08-24 B1-15c Gas Turbine Engine Page 95 of 104...

Engine Storage and Preservation (15.22) Learning Objectives 15.22.1 Describe preservation and de-preservation for a gas turbine engine and its accessories and systems (Level 2). 2022-08-24 B1-15c Gas Turbine Engine Page 95 of 104 CASA Part 66 - Training Materials Only  Accessory De-Preservation Good engine performance depends, in part, on the condition of the engine accessories. Although an engine is in a condition to give top performance after being completely overhauled, any oversight or error in reinstalling the accessories can result in an engine malfunction or irreparable damage. Therefore, follow recommended procedures in the overhaul manual or the instructions that come with overhauled or new accessories regarding de-preservation and preparation for operation. Before de-preservation of any of the accessories enclosed with the engine, refer to the accessory records to determine how long the engine and accessories have been in storage. Some accessories are life-limited and are considered unsafe for use if their storage time exceeds the manufacturer’s time limits. Before installing any replacement accessory, check it visually for signs of corrosion and for freedom of operation. Remove any plastic plugs and movement restraints placed on the accessory for shipment. In addition, lubricate the accessory drive shaft and clean the mounting pad and ange prior to installation. Always install an accessory with new O-rings or gaskets between the mounting pad and the accessory. Installation of accessory de-preservation 2022-08-24 B1-15c Gas Turbine Engine Page 104 of 104 CASA Part 66 - Training Materials Only  Engine Storage and Preservation Purpose of Engine Storage and Preservation The primary purpose of engine and accessory preservation is to prevent corrosion and handling damage. Corrosion occurs whenever a base metal such as steel, iron or aluminium combines with oxygen to form an oxide. Therefore, if the base metal is properly sealed, corrosion does not occur. Preservation is performed on engines when they are: Idle for any signi cant period Going into short- or long-term storage Transported over long distances. The procedures for preserving and de-preserving engines vary depending on the length of inactivity, the type of preservative used and whether the engine may be rotated during the inactive period. Observing engine manufacturers’ instructions for preservation increases the life of the engine when it is not in operation. Basic preservation requirements During short-term storage, the engine is started periodically (e.g. every 10–14 days) to ensure seals and hoses remain exible and intact and bearings stay coated with oil. If an engine is to be placed in long-term storage, either on-wing or off-wing, the fuel and/or oil system may need to be drained or inhibited. 2022-08-24 B1-15c Gas Turbine Engine Page 96 of 104 CASA Part 66 - Training Materials Only  Methods vary in detail from one engine type to another, but the engine preservation process is carried out to prevent internal and external deterioration of the engine and its components during storage. A de nition of short-term storage is up to 6 months after the last ight. Long-term storage is longer than 6 months after the last ight. Preservation A number of substances can absorb moisture, and one of these is silica gel. This gel does not dissolve when saturated. As a corrosion preventive, bags of silica gel are placed around and inside various accessible parts of a stored engine. It is also used in clear plastic plugs, called dehydrator plugs, which can be screwed into engine openings. Cobalt chloride is added to the silica gel in dehydrator plugs. This additive makes it possible for the plugs to indicate the moisture content or relative humidity of the air surrounding the engine. The cobalt chloride-treated silica gel remains a bright blue colour with low relative humidity, but as the relative humidity increases, the shade of the blue becomes progressively lighter. It becomes lavender at 30% relative humidity and fades through various shades of pink until, at 60%, it is a natural or white colour. With relative humidity below 30%, corrosion does not occur. Therefore, if the plug remains bright blue, the air has so little moisture that internal corrosion is held to a minimum. Dehydrator plug and humidity indicators 2022-08-24 B1-15c Gas Turbine Engine Page 97 of 104 CASA Part 66 - Training Materials Only  This same process is used in humidity indicator envelopes that can be fastened to the stored engine and inspected for colour change through a small window in the shipping case. A scheduled inspection system is implemented for engines in storage. In a pressurised container, the pressure must be maintained, and if the indicator turns pink, then the engine must be re-preserved. Details of the procedure used and any special requirements during storage should be recorded (in the engine logbook) and a copy included with the engine documentation. Some manufacturers recommend spraying oil in the compressor while the engine is motoring, while others caution against this practice. Always follow the manufacturer’s instructions. The following is a generic process. Preservation can be on-wing or off, and the materials discussed can be used on either. Fuel System Preservation Disconnect the fuel inlet line to the pump (or fuel heater if tted) and connect a supply of inhibiting oil. Disconnect the fuel line at the dump valve inlet to prevent inhibiting oil entering the fuel manifold. Place the line in a container to allow drainage. With the ignition and fuel supply valve turned off, and the fuel cut-off lever in the FULL OPEN position, complete a wet motoring cycle. During the cycle, move the power lever from take-off to idle and back to take-off. Repeat the motoring cycle, if necessary, until inhibiting oil ows from the opened fuel line. Do not exceed duty cycle limits for the starter motor. Connect fuel lines and install all engine plugs, caps and covers. 2022-08-24 B1-15c Gas Turbine Engine Page 98 of 104 CASA Part 66 - Training Materials Only  Oil System Preservation Close the normal fuel supply shut-off valve and rotate the engine with the starter until oil pressure and compressor rpm are indicated. Disengage the starter. Drain all engine oil from the tank and gearboxes. Remove and drain the main oil lter. Add inhibiting oil and rotate the engine as per the AMM. Tag the oil ller cap with the date of preservation. If the engine is to remain in the aircraft, place desiccant (moisture-absorbing material) in the engine compartment, exhaust ducts and inlet ducts. Seal all engine openings to prevent the entry of foreign matter and accumulation of moisture. Preserved engine in storage 2022-08-24 B1-15c Gas Turbine Engine Page 99 of 104 CASA Part 66 - Training Materials Only  Storage Containers When engines are removed from the aircraft and stored for any length of time, all openings and pipelines should be blanked and the engine placed in an airtight storage container. The storage container may just be a plastic envelope, a heavy cardboard or wooden box, or a metal container pressurised with an inert gas such as dry nitrogen. Calico bags full of desiccant, such as silica gel, are placed in the storage container. Cover with an airtight moisture seal incorporating inspection windows for observation of the humidity indicators. Storage containers 2022-08-24 B1-15c Gas Turbine Engine Page 100 of 104 CASA Part 66 - Training Materials Only  Storage container example Inspection of Stored Engines Engines which have been placed in storage will have a scheduled inspection period. Normally the humidity indicators on the stored engines in the shipping containers are inspected every 30 days. If the humidity indicator shows a colour indicating more that 30% humidity internally, all the desiccant bags should be replaced. 2022-08-24 B1-15c Gas Turbine Engine Page 101 of 104 CASA Part 66 - Training Materials Only  Engine Transport If an engine is to be transported over long distances, a special transport stand must be used. The engine supports must have adequate suspension or shock absorption. If the engine is to be transported by road, the transport vehicle should be equipped with air-ride suspension. These precautions prevent brinelling of the main engine bearings. Engine transport 2022-08-24 B1-15c Gas Turbine Engine Page 102 of 104 CASA Part 66 - Training Materials Only  De-Preservation The de-preservation process is carried out to restore the engine to operational condition, ready for operation on an aircraft. After de-preservation of the fuel, oil systems and accessories, the engine should be run. The procedures set out below should be treated as a basic guide only. The maintenance manual must be closely followed. Typically, de-preservation involves the following steps: Remove the container cover or storage bags and any desiccant material. Remove other covers and blanks, such as those over the intake, exhaust and accessory mounting pads. Inspect exposed and uncovered areas for corrosion and foreign objects. If installing the engine, drain inhibiting uid from the fuel and/or oil system, recharge tanks and prime the systems (‘wet motor’ prior to start). Ensure that any engine accessories tted have not exceeded their life limit. Start the engine, run it at idle for a minimum of 5 min to burn off any residual preserving uid and shut it down. Check the engine oil level and replenish as necessary. Install a new engine oil lter. 2022-08-24 B1-15c Gas Turbine Engine Page 103 of 104 CASA Part 66 - Training Materials Only