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SOLUTIONS & APPLICATIONS

nerations of screw vacuum pumps, the pitch of the • Sensitive to particles entering the system
screws is the same across the entire length. This • Cannot be used with process gases that tend
leads to compression of the process gas in the last to be reactive at high temperatures
half rotation of the screw, which generates exces-
sive thermal load there. Thus, adjusting to the ideal
operating temperature with water cooling is more Once-through oil-lubricated
difficult. Generally, dry screw vacuum pumps ope- rotary vane vacuum pumps
rate at higher temperatures than liquid ring vacuum
pumps. Condensation of process gas elements is Oil-lubricated rotary vane vacuum pumps have
thus largely eliminated. This enables the process been successfully used in many fields for decades.
gas to be conveyed through the vacuum pump wi- Today, they are amongst the most widely used
thout contamination or causing a reaction with an mechanical vacuum pumps in the industry. Busch
operating fluid. Cast iron is the standard material already developed the Huckepack, a two-stage
used for work pieces for all parts that come into once-through oil-lubricated rotary vane vacuum
contact with the pumped medium. It is either un- pump in the 1960s, which was specially desig-
treated or treated with a special coating to make ned for chemical and pharmaceutical processing
it resistant to nearly all chemicals. After the end of technology. Busch has constantly further develo-
the process, we recommend flushing the vacuum ped this vacuum pump, which continues to enjoy
pump with a suitable cleaning fluid and to purge it great acceptance in processing technology today
with nitrogen to avoid corrosion and deposit for- thanks to its robustness.
ming during stand-still.
Huckepack rotary vane vacuum pumps (Fig. 5)
With different sealing systems and various coa- have three significant distinguishing features when
tings, screw vacuum pumps from Busch can be compared to other vacuum pumps that operate
configured to be compatible with any chemical. according to the rotary vane principle:
1. Two compression stages are stacked and
Advantages of dry screw vacuum pumps: connected to each other which facilitates
• Dry compression, no contamination or reac- initial compression of the process gas in the
tion possible between process gas and ope- first stage and secondary compression in the
rating fluid subsequent second stage. This makes it pos-
• High vacuum level sible to achieve a lower ultimate pressure.
• Energy efficient 2. These vacuum pumps feature an oil-lubrica-
• Can be designed for nearly all process gases tion which means that a defined amount of
thanks to material selection and temperature operating fluid, oil or other media-compatible
regulation fluid is injected into the compression chamber.
In contrast, other rotary vane vacuum pumps
Disadvantages of dry screw vacuum pumps: use oil circulating lubrication.

Tecnologia del vuoto per l’industria

chimica e farmaceutica

La scelta della tecnologia del vuoto più adeguata per le applicazioni di processo in campo
chimico e farmaceutico è spesso difficile. Da un lato, un sistema per vuoto deve fornire
la capacità di aspirazione richiesta alla pressione di esercizio e garantire così il tempo di
evacuazione necessario. Dall’altro, deve essere resistente ai gas di processo e soddisfare
tutti i requisiti relativi ai sistemi di sanificazione in loco (CIP, clean in place) e recupero di gas.
L’affidabilità e l’efficienza economica ricoprono inoltre un ruolo decisivo nel decidere quale tipo di
tecnologia del vuoto usare.
Tre le tecnologie del vuoto più usate nei processi chimici e farmaceutici:
• Pompe per vuoto ad anello liquido;
• Pompe per vuoto a vite a secco;
• Pompe per vuoto rotative a palette lubrificate a olio.

Tutte le tecnologie di generazione del vuoto presentano vantaggi e svantaggi. Non esiste una
soluzione ideale per tutte le applicazioni. Per questo è importante consultare un esperto del vuoto
e considerare tutti i parametri coinvolti: a partire dalle condizioni di processo, i gas di processo e
l’integrazione nel controllo del processo fino alla considerazione degli aspetti relativi all’efficienza
economica, alla sicurezza e all’affidabilità della futura generazione del vuoto. Il risultato di queste
considerazioni sarà nella maggior parte dei casi un sistema per vuoto individuale a misura dei
requisiti.

94 94 Impiantistica Italiana - Settembre-Ottobre 2020