Elmo Rietschle R-WPB - Manual (Page 8)

Rietschle Thomas GmbH + Co. KG page 8 / 23
4. M
ACHINE
The RT SHARK-compact units sets are fitted with RT base
units of the Roots type with three-tooth rotors.
The Rietschle Thomas Roots blowers work on the principle
of oil-free gas transport. These blowers are the most
widespread type of two-rotor blowers. The axes of the rotor
rotation are parallel. A synchronizing gear, both of whose
wheels have the same number of teeth, moves the rotors.
The synchronizing gear ensures contact-less movement of
the rotors. The rotors turn against each other. Both the
suction and discharge sockets run between the rotor axes.
The blower transports gas without increasing the pressure.
Gas is compressed in the discharge socket by the gas that
has already been transported (blowers with external
compression).
The rotor seals of the standard blower types are not subject
to wear. Since the seals do not ensure absolute tightness of
the blower, the oil levels in the covers must not exceed the
stipulated limits. Otherwise, oil could leak into the
blower’s working space or outer space. In order to
prevent oil from leaking during transport and/or
handling of the blower, you must fill oil before putting
the machine into operation.
Blower Drive
Blowers are mostly driven by electric motors. A belt drive
normally transfers the torque from the motor shaft to the
blower shaft. The blower shaft is a part of one rotor.
Blower sets are shown in the dimensional drawings of the
individual types that are enclosed with this Manual.
The main parts of the blower sets are:
• A suction filter - a resonance silencer with a filter insert.
• A discharge silencer - a welded construction of the base
frame and the vessel. It serves as a supporting element
for the blower and is also designed to suspend and
secure the pendulous motor frame.
• A pendulous motor frame - it is suspended by pins in
the silencer frame. It enables the belts to be tightened by
tipping the motor.
• A non-return valve – an inter-flanged type. The non-
return valve of the overpressure machine type is
installed at the discharge section while that of the
vacuum machine type is installed at the suction section.
• A safety valve - it serves as overload protection of the
blower.
a) Overpressure version: if the valves are opened, air
(gas) is released into the atmosphere. Directly
controlled, HEROSE spring valves are used in smaller
blower sets. Their opening pressure is set by spring bias.
Larger types of blower sets are protected indirectly by
controlled combined safety and starting valves (see the
PVO valve description for more detail information).
b) Vacuum version: if the vacuum set by the spring has
been exceeded, the seat will lift and air will be sucked
from the atmosphere into the suction pipeline. The used
valves are directly controlled and spring-operated. Their
opening pressure is set by spring bias.
• A compensator - metal bellows.
• An electric motor - a bottom, fixed-speed or two-speed
electric motor.
• A belt drive with V-shaped or toothed belts.
• A belt guard - it is made from common constructional
steel.
The standard blower sets in acoustic enclosures are
not equipped with a belt drive guard because the
enclosure itself protects the drive.
• Bases with rubber dampers - they minimize transfer of
vibrations to the bases.
• A visual indicator of suction filter clogging. For
blower sets in acoustic enclosures, a pressure gauge is
used instead of the indicator.
• A discharge overpressure gauge or a suction vacuum
gauge.
• Optional accessories:
a) A suction pressure gauge, or an electric indicator of
filter clogging instead of the visual indicator.
b) An electric motor. You can choose a fixed-speed or
two-speed motor or a type of motor where a frequency
converter changes the motor revolutions.
• Special accessories:
a) A acoustic enclosure for inside or outside installation.
b) Pressure and temperature sensors.
c) An auxiliary discharge silencer of the vacuum blower
set. It (usually with a acoustic enclosure) serves to
reduce noise made by air being released into the blower
set’s surroundings.
Functions
The PVO combined valve has two functions. When the
blower is starting, the valve gradually increases the air
pressure, thus increasing the torque – starting valve
function. When the blower is in operation, the valve
protects it against overload (against pressure increase over
the permissible limit) – safety valve function.
Valve description
The numbers of the main parts correspond to the numbers
of the positions shown in Appendix 4 (PVO combined
valve assembly): control valve (1), mobile base (2), bottom
base (3), top base (4), bellows flange (5), hose (6), guide
rod (7), bellows (14), and springs (15).
If there is no pressure, the main valve is open – the springs
(15) lift the bottom base (3). When the blower is starting,
pressure is generated in the gap between the seat and the
disc. The control valve will feed the pressure into the
bellows. As the bellows area is larger and the bellows
power is higher than those of the seat, the bellows will
close within several seconds due to gradually increasing
pressure, thus enabling the blower to start with the load
increasing fluently. The bellows must simultaneously press
the springs (those ensuring that the unloaded valve will
open). If the unloaded valve were closed, it would not serve
as a starting valve. By removing the springs, you could
disengage the starting valve function.
By installing a solenoid valve (a special design), you could
control the blower’s start-up time electrically. When the
electromagnet of this valve is turned on, the inner space of
the bellows is interconnected with the atmosphere and the
main valve is open.
During normal operation, i.e., after the blower has started,
the main valve disc is closed. The control valve
interconnects the spaces of the outlet pipeline and the
bellows. If pressure exceeds the adjusted limit, the control
valve will release it into the atmosphere. This will result in
reducing the pressure in the bellows and opening the main
valve disc. After the pressure has dropped, the control
valve will stop releasing the pressure into the atmosphere,
thus increasing the pressure in the bellows and closing the
main valve disc.
Acoustic enclosures serve to reduce the blower set noise.
Acoustic enclosures are steel with absorption damping
material. The enclosures are equipped with fans ensuring
forced ventilation. The intake and exhaust openings for
cooling air are fitted with silencers. During forced
ventilation, the fan exhausts air out of the enclosure. The
enclosures enable the machine to be installed both outside
and in the machine hall. The types of outside enclosures up
to K 552 differ from the inside enclosures only in their
finish. The K 802 outside enclosures also have small roofs.
You can find the dimensions of the appropriate enclosure
types in their dimensional drawings.
CAUTION
Forced acoustic enclosure ventilation does not
replace machine hall ventilation.
4.1 B
LOWER
DESCRIPTION
4.2 B
LOWER
SET
DESCRIPTION
4.3 PVO
COMBINED SAFETY
AND STARTING
VALVES
4.3.1
S
TARTING
VALVE
FUNCTION
4.3.2 S
AFETY
VALVE
FUNCTION
4.4 N
OISE-
DAMPING
HOOD