LIMRA VACUUM

A)Purpose of VPD plant :

-This plant is required for the heating of Transformer coils and Complete Transformers upto 765 KV class. Maximum limit of temperature in the VPD Plant for heating medium is 180' C. The operating temperature shall be 130 C.
-This plant shall be used for vacuum drying & oil impregnation of Transformers / Reactors (i.e. oil filling of the transformer tank) weighing up to 300 Tonnes.
-Transformer shall generally consist of Copper-20%, Iron-75%, Insulating Material (Paper & Press board)-5 % by weight. Heating in the VPD plant shall be with vacuum.
-Vapour Phase Drying process is required for drying Power Transformers, Reactors,
transformers I reactor's windings, coils, etc. in an autoclave with evaporator using advance vapour phase drying process sequence: i.e. Heating up phase with Intermediate Pressure Lowering Phases, Pressure Reduction Phase, Fine Vacuum Phase, Oil filling (in transformer tank) Phase and Aeration by Dry Air.
-The whole process shall be fully controlled automatically. The computer shall monitor the process and reports can be printed timely and backup automatically for 1 year.
-Location of storage tanks & Cooling equipments : All storage tanks (i.e. solvent storage, waste water tank, waste oil tank etc.) and cooling equipments 1,nocling tower 8. chiller etc.) shall be situated 200 mtr. (Max.) from autoclave.

B)Plant Configuration:

I) Autoclave (inner dimension : 9 mtr. length x 6.5 mtr. width x 6.5 mtr. height). It shall be in welded construction of steel sheets and beams. The autoclave is loaded/ unloaded by the loading Trolley connected to a gear arrangement driven by an electrical motor. -All sides of the autoclave are heated by heating manifolds located between stiffeners on the outside. Suitable provision shall be provided for measuring the temperature of the autoclave during process. Measurement of temperature of autoclave should be displayed on the computer.

II)Iso-Static Press ( Central cylinder pressing type) : 3 sets-lso-static pressing system shall be integrated wilh autoclave which ensures an application of continuous constant pre-determined pressure on the windings throughout the drying cycle in the VPD plant. Iso-static pressing arrangement shall be used for pressing in VPD plant under hot conditions. -The coil shall be pressed in between the top & bottom clamping plates of steel structure. The press plate shall be of Central hydraulic cylinders design mounted on the bottom clamping plate . Three sets of Pressing Arrangement suitable to Press coils of below mentioned size shall be Provided by the Suppliers. For Lower diameters of the Windings, the Drawings for Pressing arrangement shall be provided by the Vendor.

III)Evaporator :Heating Capacity of 450 KW (min) with backup calculation or any higher Suilabie capacity to be provided to complete the process of transformer/reactor in 120 + or - 10 hrs. ( 15 Tons of insulation).
-The evaporator should be equipped with an automatic control system.
-Heating Circuit and temperature regulation for evaporator - The solvent is circulated via filter system through evaporator. An optimal solvent / vapour distribution in the autoclave and thus homogeneous heating up of the drying transformer and its parts etc. by condensation under the given temperature and pressure conditions should take place-Suitable nos. of valves and accessories for solvent, vapour and vacuum piping shall be provided by vendor.
-The gas mixture containing solvent and water as well as leakage air is pumped into the vapor return line to the main condenser where water and solvent condensate to minimise waste with optimum output.

IV)Main Condenser (Mixed Vapour):Welded in construction made of steel, complete with all pipework and accessories made of non corrosive material for water cooling. The water and solvent will re-condensate in the tank and are separated by the difference of density.

V)Distillation System: Distillation system shall be provided to work in parallel during the Vapour Phase drying process.

VI)Pneumatic Switch Panel For Wall Installation:Comprising the following: Pressure reduction regulator, Pneumatic control elements., Pneumatic switch panel should be such that all valves be operated by separate / individual lines.

VII)Vacuum Pump System:-Main/Base Vacuum pump Complete with gas ballast and motor. Suitable nos.
-Suction Capacity af main/ base pump - 2000 m3/hr (Min.) / suitable.
-There should be an oil level sensor,temperature sensor to be provided with each pump and quantitative values of these parameters to be indicated on screen during the process.
-Suitable interlocks to be provided to prevent running of vacuum pumps without oil and if temperature inside pump exceed certain prespecified value limit
-Booster Pumps - Complete with tanged motor - Suitable nos.
-Suction Capacity of Booster pumps - 12000 m3/hr (Min.) / suitable/Two stages- Pre. Booster and Intermediate booster (Total Suction -I 2000) @50 Hz.
-Intermediate Condenser - Water cooled, in welded construction with automatic draining system.
-Exhaust Separator - Water cooled with a water measuring device and drainage pump.

VIII)Process control & Control panel : SCADA required for VPD & Conventional Process separately:
-The plant is equipped with the system control software for continuous controlling, monitoring, visualising & observing the operation of vapour phase drying plant.-It shall monitor all process relevant data depending on the actual achieved Values and allow the automatic selection of the optimal parameters for the ongoing drying process
-The system should be such that the operator sets only general conditions and the extended system carries out unattended operation of the plant during the whole drying process.

IX)Water Chilling Plant :-Suitable capacity Water Chilling Plant is required for cooling of vapour condensers of Vapour
-Phase Plant & water jacket cooling of Vacuum Pumping System,