Vehicle compressors for mobile cooling - FK series

  • Overview
  • Documents
  • Software
  • Related applications
  • Case studies

FK series - Vehicle compressors for mobile cooling

Leading Through Tradition and Innovation
Decades of innovation for bus, rail, and transport cooling. The FK40, a reliable symbol of quality, leads a constantly evolving series meeting diverse refrigerant and application demands.

Features and benefits of vehicle compressors for mobile cooling

Lightweight, compact, robust, powerful, wide speed range

Decades of expertise: the FK series compressors are the product of extensive experience and innovation.

Versatile applications: designed for bus and rail air conditioning, as well as transport refrigeration, they excel in various settings.

Proven reliability: the FK40, with a rich history, consistently meets high-quality standards, ensuring efficient cooling.

Continuous adaptation: the entire series evolves to meet new refrigerant requirements and diverse application needs, symbolizing ongoing innovation.

Available for R134a, R513A as well as R404A, R407C

  • Wear-resistant and durable power unit
  • Forged aluminium connecting rods for maximum stability and robustness
  • Two easily visible sight glasses
  • Integrated oil collection system with large storage volume
  • Special valve plate systems for bus and transport cooling
  • Demand-oriented capacity regulation possible
  • Product range with 2-, 4- and 6-cylinder reciprocating compressors
  • Ribbed surface optimizing heat dissipation

With the most powerful version FK40/755, we offer customers 15 % more power with the same external dimensions. BOCK® vehicle compressors are equipped with the K valve plate system as standard.

They are ideally suited for bus air conditioning with increased cooling power requirements in city-, intercity and articulated buses or in areas with very warm ambient temperatures.

Unique FK valve plate system specially developed for air- conditioning

  • Valve plate made of aluminium
  • Working valves made of high-quality, impact-resistant spring steel
  • Extremely robust and reliable in the face of speed and pressure fluctuations as well as exposure to liquids
  • Long service life due to loosely guided annular discs which prevent bending and torsional forces
  • Highest operational safety and efficiency

For air conditioning and normal cooling.

  • For universal use in mobile applications
  • Lamellas clamped on one side, which are exposed to bending and torsional forces; therefore limited load-bearing capacity at high speed and exposure to liquids
  • Specially adapted version for low temperature cooling
  • Valve plate TK design for low evaporating temperatures, based on the N-valve plate basic concept with torsionally stiff lamellas
  • With additional measures for delivery rate optimization at low evaporating temperatures
  • Piston crowns provided with grooves in the suction lamella contour: for further damage space minimization and increased performance in the low-temperature range
  • Increased efficiency and performance in the low temperature cooling range

Special K1 housing – Applications for Euro 6

Due to special requirements by customers, there is a demand for additional fastening options on the compressor housing – particularly where there is little installation space available, as is the case in many Euro 6 buses. This has been achieved by means of the K1 special housing, which creates a higher level of stability thanks to the compressor being fastened directly to the vehicle motor.

Special features of the K1 housing:

  • Optimized housing
  • With intermediate flange 46 mm for suction and pressure shut-off valve
  • Available models FKX40/470 K1, 560 K1, 655 K1 and 755 K1
  • 6-cylinder compressor series FK50 with K1 housing with additional mounting points on request

Looking for spare parts?

BOCKSHOP Spare parts catalog


The online spare parts catalog allows you to find the right spare parts and accessories for BOCK compressors and units with just a few clicks. 



Type Name Language Valid for Updated Download File type
Brochure BOCK FK Compressors English Multiple 06 Oct, 2023 2.6 MB .pdf


Compressor selection tools - VAP

The VAP tool is ideal for finding the appropriate compressors for mobile applications. By inputting the required refrigerating capacity and operating conditions, the tool will display compatible components right away. In the VAP tools you will also find additional details about the suggested compressors.

Related applications

Case studies

  • if (isSmallPicture) { Danfoss Engineering Tomorrow logo in red; } else if (isBigColumns) { Danfoss Engineering Tomorrow logo in red } else { Danfoss Engineering Tomorrow logo in red }
    Danfoss adapts Optyma™ Slim condensing unit to meet G&D Chillers’ needs

    Danfoss, to meet the needs of G&D Chillers, used the microchannel heat exchanger and DSH inverter scroll with intermediate discharge valve to customize the Optyma™ Slim condensing unit, making it compatible with the high-efficiency refrigerant R-410A.

  • if (isSmallPicture) { Animated image of an office building; } else if (isBigColumns) { Animated image of an office building } else { Animated image of an office building }
    Engineering Tomorrow facilitates quiet, modular retrofit of office building’s VAV system

    When the owners of One Tower Bridge—a 15-story office building in West Conshohocken, Pennsylvania—needed to replace its 30-year-old HVAC units supplying the facility’s floor-by-floor VAV system, they turned to United CoolAir’s VariCool EZ-Fit units using Danfoss variable speed scroll compressors due to their flexible modular design and ability to handle capacity, efficiency, and noise challenges.

  • if (isSmallPicture) { University’s marine science lab finds extreme savings with variable-speed chiller plant; } else if (isBigColumns) { University’s marine science lab finds extreme savings with variable-speed chiller plant } else { University’s marine science lab finds extreme savings with variable-speed chiller plant }
    University’s marine science lab finds extreme savings with variable-speed chiller plant

    Located close to various waterways, the University of North Carolina Wilmington (UNCW) takes marine science seriously. Its new MARBIONC Building — a 69,000-square-foot interdisciplinary research facility for marine biotechnology — provides labs for lease to commercial enterprises that require reliable, energy-efficient 24/7/365 cooling. Faced with high humidity and mid-Atlantic climate variations, the building required a chiller plant that could take advantage of a wide range of operating conditions and still run reliably.

  • if (isSmallPicture) { Danfoss logo; } else if (isBigColumns) { Danfoss logo } else { Danfoss logo }
    Walk-in coolers: a summary

    Use this list to learn what goes into making an efficient walk-in cooler or freezer.

  • if (isSmallPicture) { Danfoss logo; } else if (isBigColumns) { Danfoss logo } else { Danfoss logo }
    Walk-in coolers: compressors and heat exchangers
  • if (isSmallPicture) { AURA by Desert Aire logo; } else if (isBigColumns) { AURA by Desert Aire logo } else { AURA by Desert Aire logo }
    Engineering Tomorrow doubles new DOAS efficiency

    Improving indoor air quality by increasing the amount of outdoor air (OA) entering a building is necessary in many facilities. Depending on occupant density, some buildings may require 20 cubic feet per minute (CFM) of outdoor air per person, a volume of air that can increase air-conditioning costs.