4MW vs DW Series Refrigerant Compressor: Capacity, Frame Size and Application Selection

Selection Guide · Refrigerant Compressor · 4MW vs DW Series · NH₃ / CO₂ / Freon · Russia

Both the 4MW and DW are opposed-balance horizontal reciprocating refrigerant compressors manufactured to GOST-R standards in Russia. They compress the same refrigerants — ammonia (NH₃), carbon dioxide (CO₂), and fluorocarbon refrigerants — and share the same opposed-balance frame geometry that cancels primary inertia forces. What separates them is capacity, power range, and the installation scale they are designed for. This guide explains when each series is the right specification.

✓ 4MW · 350–1,600 kW
✓ DW · 55–350 kW
✓ NH₃ / CO₂ / Freon
✓ GOST-R Certified · Russia
4MW series refrigerant compressor opposed balance NH3 CO2 industrial refrigeration Russia GOST-R large capacity 350 1600 kW

4MW series refrigerant compressor — symmetrically balanced frame, 350–1,600 kW, NH₃ / CO₂ / fluorocarbon refrigerant service. The 4MW series is the standard specification for large-scale industrial refrigeration at cold storage complexes, food processing plants, and petrochemical pre-cooling systems where continuous duty over 20–30 year plant lives is the design basis.

4MW: 350–1,600 kW
Power Range
DW: 55–350 kW
Power Range
Both Series
Opposed-Balance Frame
NH₃ / CO₂ / R
Refrigerant Media
GOST-R
Both Certified

What the Two Series Share

Before examining the differences, it is worth stating clearly what the two series have in common — because the shared features cover the majority of the technical specification that a refrigeration plant engineer needs to verify.

Both are horizontal reciprocating piston compressors with an opposed-balance frame: the pistons on each side of the crankcase move in exactly opposite directions, cancelling primary inertia forces and producing near-zero net force to the foundation and connected refrigerant pipework. Both use the same refrigerant-compatible cylinder materials — cast iron or steel cylinder bores, copper-free wetted components for ammonia service per GOST 12.2.007, and fluorocarbon-compatible seal materials for HFC refrigerant service. Both are water-cooled via internal cylinder water jackets and external inter-stage coolers, and both include a lubricated crankcase with circulating mineral oil or synthetic refrigeration oil. Both series are available for NH₃, CO₂, and fluorocarbon refrigerants, and both carry GOST-R certification with Russian-language documentation as standard.

The mechanical design principles of both refrigerant compressor series follow the same engineering logic. Suction and discharge gas valves are the plate valve type designed for refrigerant service, with valve lift limiters to prevent impact damage at high differential pressures. Piston rod packing is of the laminated ring type with oil scraper rings on the crankcase side and gas-tight packing on the cylinder side. Both series include inter-stage moisture separators and oil separators on the discharge side, and are available with automatic capacity control through suction valve unloading on individual cylinders, allowing refrigeration capacity to be stepped down to 75%, 50%, or 25% of rated capacity without stopping the machine.

Technical Comparison: 4MW vs DW Refrigerant Compressor

Parameter DW Series 4MW Series
Motor power range 55–350 kW 350–1,600 kW
Frame type Opposed-balance, 2-column Symmetrically balanced, 4-column
Primary force cancellation Complete (primary forces) Complete (forces + couples)
Refrigerating capacity (NH₃, −15°C / +30°C) 200–1,200 kW 1,000–5,000+ kW
Evaporating temperature range −40°C to +5°C −40°C to +5°C
Two-stage (booster) option ✓ Available ✓ Available
Capacity control steps 100% / 75% / 50% / 25% 100% / 75% / 50% / 25%
NH₃ service (copper-free) ✓ Standard ✓ Standard
Cooling Water-cooled Water-cooled
Motor voltage (standard) 380V / 6 kV 6 kV / 10 kV
Foundation area (approx.) 6–18 m² 18–60 m²
GOST-R certified, Russia ✓ Standard ✓ Standard

Refrigerating capacity at −15°C evaporating / +30°C condensing in NH₃ single-stage service is indicative. Actual capacity depends on evaporating temperature, condensing temperature, superheat, subcooling, and specific refrigerant. Contact our engineering team for capacity calculations at your operating conditions.

The Symmetrical Balance Advantage of the 4MW Frame

4MW series refrigerant compressor user site installation large cold storage ammonia NH3 Russia permanent plant

The designation “4MW” in the series name refers to the four-column symmetrically balanced frame architecture — what Russian compressor engineering practice designates the M-type (symmetrically balanced, as distinct from the W-type opposed-balance two-column frame used in the DW series). The 4MW frame places four cylinder columns around the crankcase in a symmetric arrangement: two on each side, with the pistons of each opposing pair moving in exactly opposite directions. This configuration cancels not only the primary inertia forces (which the DW two-column frame also cancels) but also the primary couples — the moment forces that arise from the axial offset between cylinder pairs along the crankshaft.

In practical terms, the 4MW frame transmits an even smaller alternating force to its foundation and connected refrigerant pipework than the DW series, despite operating at two to four times the power level. For a large NH₃ refrigeration system at a cold storage complex where the refrigerant pipework runs for hundreds of metres to distributed evaporator coils in multiple cold rooms, this near-zero foundation force is the engineering justification for the 4MW specification: the joint fatigue accumulation at every flange in the refrigerant circuit is negligible over the 25–30 year plant design life, regardless of the larger refrigerant inventory and higher operating pressures involved.

The 4MW frame also accommodates more cylinders per machine than the DW frame — typically 4, 6, or 8 cylinders depending on the model — which gives the refrigerant compressor a wide range of single-machine capacity options without requiring multiple parallel units. A single 4MW unit at 800 kW motor power provides more refrigerating capacity than five DW units at 160 kW each, at significantly lower total installation cost, maintenance requirement, and floor space per kW of refrigerating capacity delivered.

Application Scenarios: When Each Refrigerant Compressor Series Fits

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Large Cold Storage Complex — 4MW Series

Cold storage complexes with a total refrigerating capacity requirement above 1,000 kW at standard NH₃ conditions (−15°C / +30°C) are the primary application for the 4MW refrigerant compressor. A 10,000-tonne cold store operating at −18°C to −22°C typically requires 1,200–2,000 kW of installed refrigerating capacity, served by two or three 4MW units running in parallel — one or two on-load, one standby. The 4MW frame’s long service interval (3,000–5,000 hours between valve inspections), low foundation vibration, and high capacity per machine make it the standard specification for this application across Russia and CIS.

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Fish Processing and Blast Freezing — 4MW or DW Series

Fish processing plants combine blast freezing tunnels at −35°C to −40°C with cold storage at −18°C to −22°C, requiring both high-stage and low-stage NH₃ compression. For total refrigerating capacity above 600–800 kW, the 4MW series is the standard choice. Below this level — small processing facilities, on-board fishing vessel refrigeration systems, or modular freezing units — the DW series covers the requirement at lower capital cost and smaller installation footprint. Both series support the two-stage NH₃ compression arrangement used in blast freezing applications.

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Brewery and Beverage Cooling — DW Series

Brewery refrigeration for fermentation temperature control, beer cooling, and carbonation chilling typically requires 200–600 kW of refrigerating capacity in NH₃ or HFC service at −5°C to +5°C evaporating temperature. This capacity range maps squarely to the DW at 55–350 kW motor power. The DW opposed-balance frame provides the vibration performance needed for permanent installation in brewery utility rooms where the refrigerant pipework connects rigidly to heat exchangers and jacketed fermentation vessels throughout the building. The 4MW series would be significantly oversized for all but the largest brewery refrigeration systems.

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Petrochemical Pre-Cooling — 4MW Series

Propylene and propane refrigeration systems used in ethylene plant cold trains and LNG pre-cooling applications require large refrigerant compressor capacity in the 500–2,000 kW range. The 4MW series handles these duties in propylene or propane refrigerant service, with high-voltage motors (6 kV or 10 kV) matching the MV electrical infrastructure of petrochemical plant facilities. The symmetrically balanced frame of the 4MW series is particularly valued in these applications because petrochemical plant refrigerant pipework is extensively welded and rigidly routed over long runs — the near-zero foundation force of the 4MW series protects weld integrity at every joint in the refrigerant circuit over the 20–25 year plant design life.

Capacity Overlap: The 350 kW Zone

DW 4MW refrigerant compressor capacity overlap 350 kW selection zone NH3 industrial refrigeration Russia

At approximately 350 kW motor power, both the DW series and the 4MW series offer viable refrigerant compressor models. The DW series reaches its maximum capacity at this level, and the 4MW series begins at its minimum. This overlap zone is the most nuanced part of the selection decision, and the answer depends on factors beyond nameplate power.

Choose DW at 350 kW When:
  • This is the full installed capacity — no future expansion planned
  • Installation space is limited — DW footprint is smaller
  • 380V electrical supply — avoids MV switchgear cost
  • Multiple smaller units are preferred over a single large machine
  • Budget favours lower capital cost at equivalent capacity
Choose 4MW at 350 kW When:
  • Future capacity expansion is planned — 4MW scales higher
  • Installation is a permanent process plant with 25+ year design life
  • 6 kV electrical infrastructure is already installed
  • Refrigerant pipework is extensively rigid-welded (petrochemical)
  • Single machine preferred over two parallel DW units
Note: The comparison above applies to reciprocating refrigerant compressors only. Screw refrigerant compressors cover a different pressure and capacity range and are not directly comparable in the same technical framework as the DW and 4MW reciprocating series. Contact our engineering team if you are evaluating screw alternatives for refrigerant compression duties.
Related Application · Plastics Manufacturing

Refrigeration for PET Preform Cooling in ISBM Production

Injection stretch blow moulding (ISBM) facilities require refrigeration at two points in the production cycle: chilled water for mould cooling during the blow cycle (typically +8°C to +12°C supply, served by a water chiller rather than a direct refrigeration circuit), and in larger plants, a separate NH₃ or HFC refrigeration circuit for conditioning the preform storage area and the production hall ambient temperature during summer operation. For ISBM plants producing above 50 million bottles per year, where the production hall cooling load exceeds 300–500 kW, a DW refrigerant compressor at 55–200 kW is the appropriate specification for the production hall cooling duty — providing the opposed-balance vibration performance needed for a permanently piped refrigerant circuit in a food-contact production environment.

Related equipment: One-step three-station ISBM machines for PET bottle production — production hall refrigeration supports consistent preform conditioning and ambient temperature control during high-throughput operation.

ISBM Machine ›injectionstretchblowmolding.com

FAQ — 4MW vs DW Refrigerant Compressor

Q1: What does the “4MW” designation mean in the series name?
The 4MW designation refers to the four-column (4) symmetrically balanced (M-type, from Russian М-ОБРАЗНЫЙ meaning symmetrically balanced) frame architecture combined with the W-type horizontal cylinder arrangement (W = horizontal). This is the same naming convention used across the Russian reciprocating compressor industry. The 4MW frame has four cylinder columns arranged symmetrically around the crankcase, cancelling both primary forces and primary couples — which is why the 4MW refrigerant compressor produces even lower foundation vibration than the two-column DW opposed-balance frame, despite operating at significantly higher power levels.
Q2: Can both series handle CO₂ refrigerant as well as NH₃?
Yes. Both the DW and 4MW series are available for CO₂ (R-744) refrigerant service, which operates at significantly higher pressures than NH₃ or HFC refrigerants — approximately 3.5 MPa condensing pressure and 2.0–3.0 MPa suction pressure in transcritical CO₂ systems. The CO₂ variant of both series uses cylinder materials and seals rated for the higher operating pressures, and the crankcase lubrication system uses CO₂-compatible synthetic oil. For subcritical CO₂ systems — low-temperature stage in cascade refrigeration systems with NH₃ on the high stage — both series are available in the appropriate pressure configuration. Contact our engineering team with your CO₂ system operating conditions for a specific configuration recommendation.
Q3: What is the typical valve inspection interval for each series?
Gas valve inspection and replacement intervals for NH₃ service at standard operating conditions: DW series — typically 2,000–3,000 hours between valve inspections; 4MW series — typically 3,000–5,000 hours between valve inspections, due to lower running speed and more favourable valve lift geometry at larger cylinder bore dimensions. In both cases, intervals are extended by maintaining clean, dry refrigerant supply and keeping discharge temperatures within specification. In CO₂ service, valve intervals are generally shorter due to the higher operating pressures and greater differential pressure across the gas valves.
Q4: What information is needed to obtain a refrigerant compressor proposal?
To prepare a refrigerant compressor proposal for either series, provide: refrigerant type (NH₃, CO₂, or specific HFC grade); required refrigerating capacity (kW) or motor power (kW); evaporating temperature (°C) and condensing temperature (°C); whether single-stage or two-stage compression is required; suction superheat and liquid subcooling where known; site electrical supply voltage (380V, 6 kV, or 10 kV); and the installation type (cold store, process plant, brewery, or other). Response within 48 hours with a capacity calculation at your operating conditions and a preliminary quotation for both series where the capacity falls in the overlap zone.
Engineering Enquiry

Request a 4MW or DW Refrigerant Compressor Proposal

Our engineering team supplies DW and 4MW series refrigerant compressors for NH₃, CO₂, and HFC service across Russia and the CIS. GOST-R certified with Russian-language documentation. Spare parts stocked in Russia for 24–72 hour dispatch.