Combined Car hydraulics operating at high ambient temperature
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06-01-2011, 05:19 PM
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Combined Car hydraulics operating at high ambient temperature.pptx (Size: 5.88 MB / Downloads: 101)
LD#2 DepartmentHere desulfurization of the hot metal is carried out and the hot metal is sent to vessel unit where it is converted in to steel in Basic Oxygen Furnaces.Main material handling jobs are:
Hot Metal handling : Torpedoes of 220/320 t capacity bring hot metal from blast furnaces. These are unloaded in hot metal ladles (155 t) at the torpedo unloading pit.
Desulfurization Unit : desulphurization by CaC2 & Mg powder injection, bring down the “S” content of hot metal < .010% (treatment time depends on input ‘S’ & final ‘S’ content of the product to be made).
Unit – 3 nos.
Supplier – Thyseen Engg.
Capacity – 30 heats/ds/day
Nitrogen gas is used as carrying fluid for CaC2 & Mg powder
Raking Machine : slag raked off initially and after the DS-operation.
Unit – 4 nos.
Supplier – DDS, Germany
A Combined Car is used in a desulphurization unit of the steel plant and is also known as combined hot metal car and slag pot car. It runs on tracks and as the name suggests it carries both ladle and slag pot. There are three main components of a combined car (from front to back):
1. A seat for slag pot
3. Hydraulic power pack and other hydraulic components.
Injection and Raking are possible at the same place.
Multiple lines of over head cranes are possible.
Hot metal can be handled in multiple lines.
Thus the production rate increase.
Function of various accessories mounted
Thermostat: - when temperature of oil in the tank rises more than 55 0c, TS1 will trip off the motor M1 or M2.
Float switch: - when oil level in the tank is below working level, FS1 will switch off the motor M1 or M2.
Pressure switch: - when pressure in the line is out of range, PS1 or PS2 will switch off the motor M1 or M2.
Hydraulic Oil (at 50°C)
Hydraulic oil being used – SERVO SYSTEM 68
Density under operating conditions – 871 kg/m3
Flash point – 210 0C
Specific heat capacity – (2.08) kJ/kg 0C
Volume – 500 L
Thermal conductance = 1.4 W/m 0C
On analyzing the hydraulic circuit, total power lost during actuator operation is found to be13.52 kW.
For a complete heat actuator operates 4 times for 40 seconds.
Average time taken for completion of each heat is 60 minutes.
the interval between consecutive actuator operations or the interval for which the power pack remains idle is 860 seconds.
All of above power ultimately leads to heating of oil.
The interval between consecutive actuator operations is same.
Initially, the oil is at ambient temperature.
temperature after actuator operation can be calculated from the expression: -
Ti = (Y/X)*(1-exp (-40X)) + TAMB*exp (-40X) --------------- (1)
Where X = (UA) / ((MASSOIL)*(SPECIFIC HEAT CAPACITYOIL)) = 2.91 X 10-5
U = over all heat transfer coefficient for oil & storage tank system.
A = effective surface area of storage tank (where the convection off base of tank is neglected due to very less clearance between base and the car body).
Y = (13520/MOILCOIL) + X*TAMB
And temperature after idling period can be found from the expression: -
TF = TAMB + (Ti – TAMB)*(exp (-860*X)) ------------------ (2)
From above expressions the temperature rise after 5 hours comes out to be 10.95 0C.
Hence average rate of heat input is 564.08 W.