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A throttle start-up valve is needed to operate an underwater pelletizer system. It makes it possible to automate the start-up process, thereby minimizing “off-spec” production. In addition to this, it facilitates rapid diversion of the molten product from the pelletizer to the “floor” in the event of a fault.
| Application |  |  |
Typically, during the start-up process and after the rinsing of the die plate, the molten product is initially channeled to the “floor”, until the necessary minimum throughput is achieved. The molten product which is not entirely liquefied, or where the reaction is not fully completed, when the extruder is started up is similarly channeled off as so-called “off-spec” product. Based on this, the start-up valve monitors the timing between entry of the molten product and entry of the palletizing water into the pelletizer.
During production, the adjustable throttle makes it possible to optimize the process parameters by influencing the back-pressure length in the processing section and introducing additional thermal energy into the product.
| Description of the unit |  |  |
The throttle start-up valve consists of a heated housing, a slide valve, a throttle flap and the associated electrical and hydraulic drive units. It comprises three functional units:
| - |  | An adapter for transferring the molten mass from the twin boreholes in the processing section to a single cylindrical channel, for connection to the downstream units |
| - |  | Start-up valve for optional channeling the molten product towards the “floor” or towards the “die plate” |
| - |  | An adjustable throttle flap to influence the back-pressure length in the processing section |
| Attachment |  |  |
The throttle start-up valve is attached to the last housing on the processing section. It can also be used without the throttle flap. If this is required, the borehole to install the throttle flap can be closed using special plugs.
| Series |  |  |
|
Type
|
Unit |
133/ 150
|
177/ 120
|
250/ 150
|
320/ 200
|
320/ 350
|
350/ 350
|
380/ 350
|
|
Permitted pressure of molten mass
|
bar
|
270
|
|
Permitted differential pressure across throttle
|
bar
|
240
|
|
Steam consumption, approx.
|
kg/hr |
80
|
120
|
150
|
|
Thermal transfer oil requirement, approx.
|
m³/h |
2,5
|
5
|
150
|
|
Required heating capacity
|
kW |
40
|
70
|
100
|
|
AV drive unit
|
|
Hydraulic swivel gear
|
Twin working hydraulic cylinder
|
|
Throttle drive unit engine capacity
|
kW |
0,12
|
0,25
|
0,37
|
|
Switching period, approx.
|
s |
5
|
3
|
|
|