I. Sharing a Single Vacuum System (Most Common, Causes Severe Interference)

The vacuum pump, condenser, and vacuum buffer tank are shared, and the vapor-phase piping from both evaporation chambers converges into a single vacuum manifold. Once flow imbalance occurs, a chain reaction of disturbances ensues:

The unit with higher feed rate produces more steam, monopolizing vacuum resources

The unit with higher feed has a higher evaporation load, generating a large amount of secondary steam per unit time, which continuously consumes the vacuum pump’s suction capacity; the vapor flow in the main line surges, pipeline resistance increases, and the absolute pressure in the main line rises.

The other unit, with lower feed and minimal steam production, sees its originally stable negative pressure raised by the increased main line pressure; the gauge vacuum drops simultaneously, the boiling point rises, and evaporation efficiency decreases.

Flow fluctuations cause vapor backflow and pressure surges

When feed rates fluctuate wildly, the high-load unit experiences instantaneous steam bursts; high-pressure steam travels backward through the shared vapor header and impacts the other unit’s chamber. This creates instantaneous positive pressure pulses, causing the vacuum probe to drift violently and triggering frequent automatic gas replenishment and temperature control oscillations.

Foam entrainment causes cross-contamination and exacerbates pressure differentials by blocking shared piping

Units with excessive feed are prone to foaming; foam and salt mist enter the main header, adhere to the pipe walls, and narrow the passage. This increases overall system air resistance, causing vacuum levels in both units to deteriorate simultaneously, with the unit under lower load being more significantly affected.

Imbalanced condensation load distribution leads to accumulation of non-condensable gases

The side with higher steam production occupies the majority of the condensation heat exchange area. The trace amounts of non-condensable gases generated by the unit with lower feed cannot be evacuated in a timely manner, causing gas to accumulate and build up pressure within the chamber, resulting in persistently low vacuum.

II. Separate vacuum pumps, with only the front-end feed lines connected in parallel (minimal but still present interference)

The vacuum systems are completely separate, with feed distribution occurring only at the feedstock tank. Interference arises from indirect conduction on the liquid side:

If the feed flow rate of one unit suddenly increases, the tank liquid level drops rapidly; the suction pressure of the other unit’s feed pump becomes insufficient, leading to inadequate circulating feed volume, dry wall heating, and localized instantaneous vaporization, causing short-term pressure fluctuations in the chamber;

The stock concentration fluctuates due to imbalance in distribution; one system’s concentration ratio continues to rise, altering foaming characteristics, and steam volume fluctuates dramatically; Even with independent vacuum systems, interference from workshop ambient pressure and shared exhaust stack airflow can cause minor synchronous vacuum drift.

III. Typical vacuum interference phenomena caused by uneven flow

One vacuum remains stable while the other remains persistently low, resulting in polarized temperature differences and evaporation rates;

Both units exhibit synchronized periodic vacuum fluctuations, synchronized with the start/stop of the feed pump and valve openings;

Low-load units frequently trigger low-vacuum alarms, causing the temperature control system to automatically increase the temperature for compensation, resulting in a significant rise in energy consumption;

Extreme operating conditions: High-load units experience instantaneous steam production overload, causing pressure buildup in the main pipe, while low-load units experience vacuum breakdown and backflow of condensate.