|
Expansion Engine:
The Expansion
Engine is vertical, single acting, reciprocating type. This produces
the cold required for the plant. High pressure air enters through inlet
valve at the start of downward stroke of the piston On further
downward motion, the inlet valve closes and entrapped Air expands.
During upward stroke, outlet valve remains open and inlet valve remains
closed.
Therefore, in
downward stroke Air enters the cylinder and expands. In the upward
stroke the expanded air is pushed outside. The electric motor is used
to start the machine. Thereafter the engine is moved by the Air
pressure itself and during which time the engine motor retains the
speed by acting as a brake. Since work is done by Air in rotating the
flywheel, it loses it heat content (enthalpy), thus the Air gets
cooled. This cooling is more than that of an expansion in an expansion
valve.
An elementary
factor for the function of an expansion engine is to use dry and carbon
dioxide free air, as otherwise, ice and dry ice will form on valve
seats, causing mal-function.
The approx.
temperature drop across expansion engine is 50 to 70oC, depending on
inlet air pressure, temperature and inlet cam position.
The Expansion Engine consists of three major units:
- The drive unit
- The cylinder unit for Air expansion
- The Hydraulic system for operating the valves
The
drive unit is similar to any reciprocating machine with usual parts.
Such as crank case, crankshaft, connecting rod, crosshead, etc. The
Expansion Engine has an extended crankshaft enabling the accommodation
of the cam box. The moving parts are lubricated through a hole in
crankshaft. Oil scrapper rings are provided to prevent oil escape to
cylinder unit.
The cylinder unit
handling the process Air consists of cylinder, piston, inlet and outlet
Isolation Valve Assemblies. The Ball valves are actuated mechanically
by a Push Rod as per the timing transmitted by the cam. The Push Rods
are housed in a stuffing box to avoid Air leakage and are actuated by
the Hydraulic system.
The Hydraulic system is the control system. The Hydraulic oil is fed by a pump to:
- Pressurized oil container for valve actuation
- Lubricate crankshaft and drive and drive unit parts
- Lubricate the rolled holders
Technical Specifications:
Specifications
|
80/100/130 M3/Hr Oxygen Plant
|
170/200 M3/Hr Oxygen Plant
|
Type of Expansion Engine
|
Vertical Single Acting
|
Vertical Single Acting
|
Diameter of cylinder bore
|
90 mm
|
80 mm each
|
No. of cylinders
|
1
|
2
|
Piston stroke
|
150 mm
|
125 mm
|
Speed of Engine
|
200 RPM
|
200 RPM
|
Inlet valve opening time cam setting
|
8 positions
|
8 positions
|
Electric Motor
|
10 HP / 1000 RPM (TEFC)
|
20 HP / 1000 RPM (TEFC) |
Piston head clearance
|
1.2 +/- 0.2 mm
|
1.2 +/- 0.2 mm
|
Inlet valve pastel clearance
|
0.4 to 0.5 mm
|
0.4 to 0.5 mm
|
Inlet air pressure
|
60 kgs/cm2g
|
60 kgs/cm2g
|
Outlet air pressure
|
5 kgs/cm2g
|
5 kgs/cm2g
|
Throughput volume at 40 kgs/cm2
|
400 Nm3/hr.
|
700-800 Nm3/hr.
|
|
