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FUNCTION : The Centralized Lubrication is required to ensure the failsafe, controlled supply of clean (filtered) Cooled oil to the drive gear boxes. CONFIGURATION : The system comprises of storage tank installed at negative draft to the drive gear box for gravity flow of oil into the tank. The tank is of adequate capacity, to provide stagnant time to oil flow for froth separation. Baffle plates are provide to increase path of oil flow to facilitate de-aeration. Two Nos. positive displacement gear with inbuilt relief valve are provided with shutoff valve at the suction, connected to tank bottom. The pump discharge through check valve, an additional relief valve is connected to two Nos. filters inlet (one running, one standby). The filtered oil from the discharge passed through the shell & tube type heat exchanger. The discharge line of cooled oil to the drive gear boxes is provided with pressure accumulator. CLEAN OIL : Return line from the drive gear box and fresh oil inlet ports are with filters for primary coarse filtration. Two (one standby, one running) secondary filters are provided for fine filtration. The filters are deliberately over designed, to offer prolonged cleaning interval. The filter casing and mountings stands are so designed to facilitate on site clearing/changing of elements (without the need of physical removal of casing from the lubrication pipe). The elements are so designed, so as to provide maximum filtration surface area. The number of elements provided are many times the filtration capacity of the lubrication unit for prolonged element cleaning/changing interval. Pressure switch clogging alarm, necessitating changeover to standby filter is provided across filter. The necessary shut off valves (plug type, AUDCO make) are provided, to change over to the standby filter during cleaning of running filter. COOL OIL : The over sized tank provides the initial cooling surface. The shell & tube type heat exchanger with copper tubes, with adequate heat transfer area is provided. The bye pass valves are provided across heat exchanger, enabling, attending to problem without shutting of the unit. CONTROLLED SUPPLY : A self actuated, diaphragm operated, force balance type, excess pressure valve is optionally provided in the discharge line to maintain constant discharge pressure, within +/- 2%. A) STANDBY EQUIPMENT : i) (a) Standby pumps with inbuilt pressure relief
valves. B) PRESSURE SWITCH : To be interlocked with the drive motor is provided in discharge line. The drive motor cannot be put on, unless there is 2 Kg/cm pressure in the lubrication line and N.O. point charges to N.C. C) ELECTRICAL PANEL :
Is provided with :--- D) THE
PRESSURE SWITCH : Is coupled through
the timer provided in panel for tripping the gear box drive motor
after preset time (at timer upto 2minutes), in case of failure
of both the pumps (or electricity failure). The delayed tripping
allows rolling of the material ejected from the furnace before
mill tripping. The signal can be provided from the N.O. terminal
of the pressure switch to the furnace ejector, indicating imminent
tripping (after the preset time) of the mill, to stop fresh ejection
of material from the furnace. E) THE
PRESSURE ACCUMULATOR : Of two minutes
capacity is provided in the discharge line to maintain oil supply
to the drive gear boxes during the preset time, when the pumping
unit is down, and mill is yet to trip (after the preset time).
There is no dry running of the drives. STANDARD EQUIPMENT: i) Pumps used are with herringbone gears, are gas nitrated and hardened to maintain positive supply of oil for long trouble free duration. ii) All valves are plug type of AUDCO make. iii) Stain less steel, wire mesh filter elements with increased filtration surface area of NAV BHARAT make. iv) All pipes are hydraulically tested (at twice the maximum working pressure) pickled and galvanized, before assembly. v) Pressure/Differential pressure switches are of INDFOSS (previously DANFOSS) make. vi) All electrical items are SIEMENS / L&T make.
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