Screw Compressors

Screw Compressors

Today. FTI’s screw compressors, production of which began in 2008, have received high acclaim for their technological strength and reliability. They are renown globally not only in the food, beverage and cold storages in distribution centers, but also in the oil & gas and chemical markets for Gas compression and refrigeration applications where extreme durability is required of critical equipment. FTI is also an industry leader in customer satisfaction, deliver quality local customer support from more than 30 locations worldwide.


FTI’s industry leading technology has enabled gas compression for virtually all kinds of gases under various conditions. It has broadened the range of applications of FTI compressors:

  • Hydrocarbon gases -CmHn (VOC vapor recovery, wellhead gas gathering, etc.)
  • Gases containing corrosive components like sour gas, flare gas, or coke oven gas
  • Raw material gases such as vinyl chloride, monomer and methyl chloride, etc.
  • Corrosive gases such as chloride, hydrogen chloride, hydrogen sulfide, C2F4, etc.
  • Fuel gases such as natural gas, coal seam gas, liquefied petroleum gas, etc.
  • Industrial gases such as helium, hydrogen, carbon dioxide, air, etc.
  • Natural refrigerants such as propane, propylene, butane, pentane, ammonia, etc.
  • Synthetic refrigerants including HFC, HCFC.


Compression is achieved by successive volume reduction of the space enclosed between the meshing line by the rotation of the male / female rotors and the casing.

During the suction phase, the gas enters the compressor rotors via the suction port and is sealed between the rotors and the casing.

As the rotors continue to rotate, the meshing line of the lobes moves toward the discharge end of the casing and the trapped volume gradually decreases, resulting in gas compression.

At the moment when compression reaches the designated ratio, this trapped volume becomes exposed to the discharge port and exits as a compressed gas.

These phases are continuously performed.


Compared to a conventional reciprocating compressor, a screw compressor has no consumable or fragile parts like suction/discharge valves, piston rings, etc.

The main friction-bearing parts are limited to journal bearings, thrust bearings, shaft seals and the fully lubricated intermeshing rotors, therefore the construction of the compressors is extremely simple and robust. The rotors are also constructed with high strength materials and can withstand slightly wet gases containing mist or liquid where reciprocating or centrifugal compressors may have serious problems.

Even under the most severe operating conditions, the screw compressor demonstrates very high reliability. Fewer parts mean less maintenance work, and superior operational lifespan is achieved.


Built-in unloader slide valve function enables the compressor capacity to be continuously adjusted from 10%* to 100%. Therefore, the compressor is able to run with appropriate load across a wide range of operating conditions, resulting in high efficiency operation.

Capacity control through the use of bypass control valves or by variable speed inverter can be used in conjunction with the slide valve as well, depending on the process requirement.

*The minimum value of capacity control varies by operating conditions and models.


Previously, API619 was the standard for dry screw compressors exclusively, but from the 3rd edition (and moving forward) oil flooded screw compressors are also officially included. FTI is able to meet the specifications required by API 619 such as cast steel casings, forged steel rotors, tilting pad thrust bearings,

vibration and displacement probes, bearing temperature sensors, etc., to fit any customers’ requirements.


Sleeve type radial bearings and anti-friction ball thrust bearings are standard, but special material sleeve bearings and tilting pad thrust bearings are also  available* to meet the customer’s requirements based on gas properties and compression conditions


In oil-flooded screw compressors, lube oil is injected during the gas compression process to provide lubrication for the rotors and casing, minimize gas leakage, and to cool the gas. Therefore, discharge temperatures are lower than those that occur with dry screw compressors, and higher volumetric efficiency is achieved from low compression ratios to high compression ratios


All FTI  screw compressors go through Hydrostatic Test and Pneumatic Test to ensure their excellent pressure resistance and airtight sealing. Only the compressors that satisfy the performance, vibration, noise and function standard after Mechanical Running Test are shipped from the factory. Other tests, including tests for third party certifications, such as DNV, GL, and BV, can be arranged.


For capacity and control monitoring, FTI provides slide valve position sensors with indicators (without indicators on GH series models). Explosion proof indicator is available as an option.


The oil flooded type screw compressors require only one shaft seal, unlike the dry type compressors. In order to ensure high reliability and durability under all

operating conditions, various kinds of shaft seals are available. The balance type single mechanical seal is used most often but a double seal, bellows seal, gas seal, etc. are also available.


Unlike conventional reciprocating compressors, screw compressors have no reciprocal motion, so that the noise and vibration are far lower. Also, unlike centrifugal or dry type compressors, high rotation speeds are not required and no high frequency noise will be generated.

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