Vacuum Pump Selection Guide: Rotary Vane to Dry Screw

Full-Series Vacuum Pump Selection Guide: From Rotary Vane Pumps to Dry Screw Pumps — A Detailed Look at Vacuum-Fresh Trading’s Product Line

Article Summary: The vacuum pump is the “heart” of a vacuum cooling system—selection directly affects pump-down time, cooling efficiency, and operating costs. This article reviews the performance parameters and application scenarios of three major categories—rotary vane pumps, Roots pumps, and dry screw pumps—and provides a quick-reference table for matching chamber volume and pump pumping speed as well as a domestic replacement cost-reduction plan. Keywords: vacuum pump selection, rotary vane pump, dry screw pump, Roots pump, vacuum cooling system, pump-down time, domestic replacement Publish Date: 2026-07-30

I. Problem: Low Efficiency in Vacuum Cooling Systems Often Traces Back to the Vacuum Pump

During operation of vacuum cooling systems, one high-frequency problem repeatedly arises: customers report that the cooling cycle is far longer than expected, and the equipment may even fail to reach the target temperature entirely. After 120+ project calculations and verifications, more than 50% of solutions have a mismatch between pump power and chamber volume. Pump-down time accounts for 40%~70% of the entire cooling cycle—this means that if the vacuum pump is selected incorrectly, even a good refrigeration system is wasted.

II. Cause Analysis: Pump Selection Logic Is Underestimated

Many users focus their attention on the compressor or cooling capacity but overlook that the vacuum pump is the “starting point” of the cooling cycle. The vacuum pump’s task is to reduce the chamber pressure below the saturated vapor pressure of water (approximately 660Pa), causing moisture in the material to boil and evaporate at low temperature. The pump’s three parameters—pumping speed, ultimate vacuum, and power—directly determine:

• Whether pump-down time can be kept within a reasonable proportion of the cooling cycle
• Whether the final cooling temperature meets the target
• The proportion of pump energy consumption in operating costs (approximately 15%~35% of the entire machine)

III. Principle: Core Matching Formula

The formula for estimating actual pump-down time is:

Actual pre-pumping time = (V / S) × ln(101325/660) × 1.3
Where V = chamber volume (m³), S = total pump pumping speed (m³/h)

If the calculated result exceeds the claimed cooling cycle × 0.7, then the pump configuration is the system bottleneck and must be upgraded.

IV. Solution: Comparison of Three Major Categories Across the Full Series

Vacuum-Fresh Machinery Trading’s product line covers three mainstream vacuum pump types, each with its applicable scenarios:

Full-Series Parameters of Rotary Vane Pumps (Domestic DLT Series)

Full-Series Parameters of Dry Screw Pumps (BLG Variable Pitch Series)

Quick-Reference Table for Chamber Volume and Pump Configuration

V. Domestic Replacement Cost-Reduction Path

After repeated bench testing and on-site verification, the domestic Dalutong DLT series and Leybold SV series have a pump-down time deviation of less than 15%, but the cost difference is significant:

VI. FAQs

Q1: What causes oil emulsification in rotary vane pumps? How can it be solved? A: The main cause of oil emulsification is that the pump draws in a large amount of water vapor; after the oil contains water, it turns milky white. Preventive measures are to ensure the moisture trap is working properly and to run unloaded for 5–10 minutes before shutdown. Once the oil is found to be milky white, the oil should be changed immediately. Q2: In a vacuum cooling system, is a larger pump power always better? A: No. Excessive power causes unnecessary energy consumption, while too little power makes the pre-pumping time too long. The core principle is to match chamber volume with pump pumping speed; simply use the formula t=(V/S)×ln(101325/660)×1.3 for calculation. Q3: How reliable are domestic vacuum pumps? A: Daluotong DLT series, Zhongde/Feilu, and other domestic pumps have been verified to operate reliably for more than 2000 hours in small and medium-sized machine solutions, and are suitable for domestic standard configurations. The deviation of core indicators (ultimate vacuum, pumping speed) from imported brands is controllable. Q4: Can a Roots pump be used alone? A: No. A Roots pump requires a backing pump (rotary vane pump or screw pump) to work with it; the ultimate vacuum can reach below 10Pa, but it cannot discharge directly to atmosphere. It is mainly used in high-vacuum scenarios such as freeze-drying production lines. Q5: What are the advantages of dry screw pumps compared with rotary vane pumps? A: Dry screw pumps run oil-free, can reach an ultimate vacuum of 1Pa, require extremely low maintenance, and are suitable for food-grade clean environments. The disadvantages are higher price and greater weight. It is recommended that food factories with high cleanliness requirements give priority to them. Q6: How can you determine whether a pump needs maintenance? A: Compare the measured ultimate vacuum with the nominal value; if the difference exceeds 30%, maintenance is required. Troubleshooting sequence: inlet filter clogging → exhaust valve plate carbon deposits → insufficient oil level → pump chamber wear.

VII. Summary

Vacuum pump selection is the first threshold in vacuum cooling system design. Yuanxian Machinery Trading’s product line covers 7 rotary vane pump models, 6 dry screw pump models, 5 Roots pump models, and a full set of consumables and repair parts, supporting domestic substitution for cost reduction and imported brand customization. If you need assistance with selection, please refer to the vacuum precooler product page to learn about matching solutions, or contact the Yuanxian Machinery technical team to obtain pump configuration calculation services.

The data in this article is based on 120+ vacuum system solution calculations and actual vacuum pump selection case summaries by Yuanxian Machinery.