FAQ / Vacuum Knowledge

ZT Pumps is the international brand of Nantong Zhongtian Machinery Manufacturing Co., Ltd., a vacuum pump manufacturer based in Nantong, Jiangsu Province, China. The company was founded in 2002 and manufactures industrial vacuum pumps and engineered vacuum systems for customers worldwide. ZT Pumps, Zhongtian Pumps, and Nantong Zhongtian Machinery Manufacturing Co., Ltd. all refer to the same manufacturing business.

ZT Pumps is a manufacturer. Nantong Zhongtian Machinery Manufacturing Co., Ltd. designs and manufactures vacuum pumps and vacuum systems at its own factory in Nantong, Jiangsu, China. The company does not resell third-party products under its own brand.

All ZT Pumps vacuum pumps are manufactured by Nantong Zhongtian Machinery Manufacturing Co., Ltd. at its manufacturing facility in Nantong, Jiangsu Province, China.

ZT Pumps (Nantong Zhongtian Machinery Manufacturing Co., Ltd.) is located in Nantong, Jiangsu Province, China — in the Yangtze River Delta region, approximately 100 km north of Shanghai.

Yes. Liquid ring vacuum pumps are one of the core product lines at ZT Pumps. Available series include SZ, LD, 2BVA, ZTS, 2S, and 2BE. These pumps are suitable for industrial process vacuum, condensable vapour handling, chemical processing, pharmaceutical production, and power generation applications.

Yes. ZT Pumps provides OEM and ODM manufacturing services for vacuum pumps. This includes manufacturing vacuum pumps to customer brand specifications, supplying branded spare parts and repair kits, and providing custom engineering and documentation. Products are available in 50 Hz and 60 Hz configurations for global markets.

Yes. ZT Pumps manufactures vacuum pumps in both 50 Hz and 60 Hz configurations to serve customers in different regions. Please specify your required frequency when requesting a quotation.

Yes. In addition to individual vacuum pumps, ZT Pumps designs and manufactures complete engineered vacuum systems. These include Roots vacuum units (Roots booster + backing pump), liquid ring closed-loop systems (with separator, heat exchanger, and recirculation), and custom vacuum systems engineered to specific process requirements.

Ultimate pressure (also called ultimate vacuum) is the lowest pressure a vacuum pump can achieve under ideal conditions with no gas load — i.e., with the inlet closed. It is typically measured in mbar or Pa and represents the theoretical performance limit of the pump.

Absolute pressure is measured relative to a perfect vacuum (0 Pa). Gauge vacuum (or vacuum gauge pressure) is measured relative to atmospheric pressure — it shows how far below atmospheric the system is. For example, 0.1 mbar absolute ≈ 1013 mbar vacuum gauge at sea level.

The most common vacuum units are: mbar (millibar) — widely used in Europe and Asia; Pa (Pascal) — SI unit, 1 mbar = 100 Pa; Torr — used in North America and scientific contexts, 1 Torr ≈ 1.333 mbar; mmHg (millimetres of mercury) — equivalent to Torr; micron (µm Hg) — 1 micron = 0.001 Torr, used for high vacuum. Atmospheric pressure is approximately 1013 mbar = 101,325 Pa = 760 Torr.

A liquid ring pump uses a rotating impeller inside a casing partially filled with liquid (usually water). Centrifugal force throws the liquid outward, forming a rotating ring that compresses gas pockets between the impeller blades. The gas is drawn in through the inlet port and discharged through the outlet port as the pockets shrink.

A Roots booster (also called a Roots blower or mechanical booster) is a positive-displacement pump with two figure-eight-shaped rotors. It cannot operate alone against atmospheric pressure and requires a backing pump. When combined with a backing pump, it significantly increases pumping speed in the medium-vacuum range (1–100 mbar).

Gas ballast is a controlled air admission into the compression chamber of a rotary vane pump. It prevents condensation of water vapour inside the pump by raising the partial pressure of vapour above its dew point before discharge. Using gas ballast reduces ultimate vacuum slightly but protects the pump oil from contamination.

Liquid ring pumps use a rotating liquid ring to compress gas — they are tolerant of wet gases, condensable vapours, and liquid carry-over, but their ultimate vacuum is limited by the vapour pressure of the seal liquid (typically 33–160 mbar with water). Dry screw pumps use intermeshing screw rotors with no liquid in the pumping chamber — they can achieve much deeper vacuum (below 1 mbar) and are preferred for clean, dry processes where oil or liquid contamination is unacceptable.

In liquid ring vacuum pumps, the seal water temperature directly limits the achievable vacuum. The pump cannot pull below the vapour pressure of the seal water. At 15°C, water vapour pressure is about 17 mbar — so the pump can achieve approximately 33 mbar absolute. At 25°C, the limit rises to about 50 mbar. Cooling the seal water improves ultimate vacuum.

Yes — liquid ring pumps are well suited to solvent vapour applications. The working liquid absorbs and condenses solvent vapours, preventing them from reaching the discharge. In a closed-loop system with a separator and heat exchanger, the recovered solvent can be recirculated or collected for reuse.

A closed-loop system recirculates the seal liquid rather than discharging it to drain. The system includes the liquid ring pump, a gas-liquid separator, a heat exchanger to cool the recirculated liquid, and a recirculation pump. Closed-loop systems are used when the seal liquid is contaminated with solvents or process chemicals, or when water conservation is required.

The choice depends on your process requirements: Dry screw pumps are best for clean, dry processes requiring deep vacuum (< 1 mbar) without oil contamination. Rotary vane pumps suit laboratory and light industrial applications needing deep vacuum with compact size. Liquid ring pumps excel where the gas contains condensable vapours, corrosive gases or entrained liquids — they are robust and tolerant of wet gas loads. Use our Pump Selector tool for a guided recommendation.

Key parameters for sizing a liquid ring pump are: required pumping speed (m³/h or m³/min) at the operating pressure, operating pressure (mbar absolute), gas composition and temperature, seal water temperature and supply pressure, and whether the system is once-through or closed-loop. Contact ZT Pumps with your process data for a sizing recommendation.

A Roots booster system can typically reach 0.1–1 mbar when backed by a rotary vane or dry screw pump. With multiple Roots stages, pressures below 0.01 mbar are achievable. The actual performance depends on the compression ratio of the Roots stage and the ultimate pressure of the backing pump.

Dry screw pumps are oil-free in the pumping chamber and require minimal routine maintenance. Key tasks include: periodic inspection of the nitrogen purge (if fitted), checking gear oil levels in the gearbox, monitoring bearing temperatures, and inspecting shaft seals. Service intervals are typically 8,000–16,000 hours depending on the application.