Sữa Industry Bearings: Codes & Applications

Bearings for the dairy industry are specialized rolling-element components — predominantly ball bearings in stainless steel with sealed designs — that must simultaneously satisfy three demanding constraints: resistance to high-pressure washdown, compatibility with food-grade cleaning chemicals, and zero product contamination risk if lubricant leaks.

In a modern dairy plant, bearings appear at every processing stage — from raw-milk intake pumps to end-of-line packaging machines. Technical requirements shift sharply by equipment type: UHT sterilizers demand bearings rated to 140°C, centrifugal separators require 6,000–10,000 rpm capability, and CIP/SIP systems impose chemical attack from 2% NaOH and nitric acid. Selecting the wrong bearing — even just the wrong suffix — can halt the production line mid-batch, with product losses reaching hundreds of millions of dong per incident.

Definitions and dairy-specific requirements

The dairy industry falls under food and beverage (F&B) regulations governed by TCVN 5603:2008 (equivalent to Codex CAC/RCP 1-1969) on food hygiene. Two direct constraints follow for bearing selection.

Constraint 1 — Food-contact materials. Bearings in wet zones must use AISI 316L stainless steel or equivalent. Bearings in dry zones may use standard chrome-plated steel, but must have seals preventing ingress of washdown water.

Constraint 2 — Food-safe lubrication. Every location where lubricant could reach the product — even indirectly — must use H1-rated grease per NSF International. H1 grease is approved for incidental food contact up to 10 mg/kg. Standard mineral EP2 or LGMT2 grease is absolutely prohibited in these zones.

Three main equipment groups in a dairy plant, ranked by hygiene stringency:

Bearings for heat-processing equipment

Pasteurizers and UHT sterilizers

HTST (High Temperature Short Time) pasteurizers push milk through plate heat exchangers at 72–75°C for 15–20 seconds using centrifugal pumps. UHT processing reaches 135–140°C. Pump shafts carry primarily radial load, sometimes with mild axial components.

Standard bearing for dairy centrifugal pumps: 6308-2RS C3 (d=40, D=90, B=23 mm, C=32.5 kN, C₀=21.2 kN). The 2RS double rubber seal resists washdown water ingress; C3 internal clearance compensates for thermal expansion as the shaft heats from ambient to 80°C.

For larger pumps (shaft d=50 mm), use 6310-2RS C3 (d=50, D=110, B=27 mm, C=48.0 kN, C₀=31.5 kN). Grease speed limit: 4,300 rpm — adequate for all standard sanitary pumps.

One important detail: the shaft end facing the coupling can receive axial thrust of 3–5 kN. If the pump uses a mechanical seal, the seal adds further axial load. In this case, replace 6308-2RS with 7308 BEP (angular contact ball bearing, d=40, D=90, B=23 mm, C=37.7 kN) for better axial load handling.

Grease: SKF LGFQ 2 — H1-rated polyurea base, rated to 150°C, compatible with EPDM rubber seals. Relubrication quantity: G = 0.005 × D × B = 0.005 × 90 × 23 = 10.4 g. Relubrication interval: 2,000 hours or 6 months, whichever comes first.

Homogenizers

A homogenizer is a high-pressure machine (100–300 bar) that forces milk through a narrow gap to break fat globules. Pistons cycle at 100–300 strokes per minute, creating impact loading on the cam shaft. This is a special case: high dynamic load, temperatures of 60–80°C, and mandatory scheduled bearing replacement rather than run-to-failure, because an unplanned mid-batch stop is extremely costly.

Bearing for the homogenizer cam shaft: 22216 EK/C3 (d=80, D=140, B=33 mm, C=163 kN, C₀=200 kN). The spherical roller bearing (SRB) absorbs shaft misalignment from manufacturing tolerances and thermal distortion. C3 clearance is mandatory when mounting on a tapered bore.

Scheduled replacement interval: every 8,000 operating hours regardless of vibration readings. The cost of an unplanned shutdown during peak production months far exceeds the bearing price.

Centrifugal separators

Separators remove cream from fresh milk by centrifugal force at 6,000–10,000 rpm. The shaft runs vertically; radial load is low but axial load from bowl weight and hydrodynamic forces is substantial. This is technically the most demanding bearing position in a dairy plant.

Separator bearings are OEM-specific. Manufacturers such as Alfa Laval, GEA, and Tetra Pak specify proprietary codes technically equivalent to duplex DGBB pairs or angular contact pairs in DB or DF arrangement. Standard bearings must not substitute OEM units here. Mandatory replacement interval: every 4,000–6,000 hours depending on model.

Per NSK technical catalogue, angular contact bearing 7208 CDB (DB pair, d=40, D=80, B=18×2 mm) handles 16.3 kN axial load at up to 10,000 rpm with oil-mist lubrication.

Bearings for packaging equipment

Filling machines

Aseptic fillers operate inside a sterile chamber. Bearings in this zone are exposed to H₂O₂ at 30–35% concentration and 50–60°C during COP (Clean Out of Place) sterilization cycles. Standard nitrile (NBR) rubber seals degrade in H₂O₂ — PTFE or EPDM seals are mandatory.

Standard bearing for filling heads: 6204-2Z (d=20, D=47, B=14 mm, C=9.95 kN) with metal shield. Metal shields resist chemicals better than rubber seals and are preferred at low speeds (< 500 rpm) in wet environments.

Bearing for the main cam distribution shaft: 6305 C3 (d=25, D=62, B=17 mm, C=11.2 kN) — C3 clearance needed due to accumulated eccentricity on long shafts.

Sealing machines

Tetra Pak, Combibloc, and HDPE carton sealers use heat-sealing temperatures of 160–200°C at the sealing jaw. Bearings near the sealing head need heat resistance — rubber seals must be avoided; use open bearings with high-temperature grease.

Bearing at the sealing cam: 6006 (d=30, D=55, B=13 mm, C=13.5 kN, open type) with Klüber Isoflex Topas NCA 52 grease (PTFE base, rated to 220°C). Relubrication interval: 500 hours because elevated temperature accelerates grease oxidation.

Bearings for refrigeration systems

Refrigeration compressors

Dairy plants maintain 2–6°C in fresh-product cold stores and –18 to –25°C in frozen stores. Refrigeration compressors — reciprocating or screw type — are critical infrastructure. A four-hour compressor failure at a frozen store can destroy an entire production batch.

Bearing for reciprocating compressor shafts: 6309 C3 (d=45, D=100, B=25 mm, C=40.5 kN). Synthetic POE (polyol ester) refrigeration oil in R404A/R134a systems permeates bearing seals and dilutes standard grease. POE-compatible grease is mandatory — standard lithium grease is incompatible with synthetic refrigerants.

Compatible grease: Mobil SHC Polyrex EM — polyurea base, POE-compatible, operating range –40°C to +150°C.

For screw compressors: 22320 EK/C3 (d=100, D=215, B=73 mm, C=520 kN) at the suction end; 32218 (d=90, D=160, B=40 mm, C=216 kN) at the discharge end to handle axial thrust. Bitzer catalogue rates bearing design life in industrial refrigeration compressors at 25,000 hours with correct oil-ring lubrication.

Evaporator fans

Evaporator fans in frozen stores (–18 to –25°C) generate more unexpected failures than almost any other bearing position in the plant. Standard grease stiffens at –20°C, creating high starting torque — either the fan motor burns out, or the bearing scores from starvation during start-up.

Standard bearing for evaporator fans: 6205-2RS (d=25, D=52, B=15 mm, C=14.8 kN) — the most widely used size for 0.18–0.75 kW fan motors. However, the grease factory-filled in standard 6205-2RS is not suitable for deep-cold temperatures.

Solution: order 6205-2RS/VT378 (Schaeffler suffix VT378 = Arcanol TEMP90, rated –50°C to +90°C) or re-grease with Shell Gadus S5 V100 2 before installation. Fill quantity: G = 0.005 × 52 × 15 = 3.9 g — fill only 30–50% of cavity volume, never pack full.

CIP/SIP cleaning and food-grade requirements

Understanding CIP and SIP

CIP (Clean-in-Place) is a recirculating wash process that cleans pipe interiors and equipment surfaces without disassembly. Standard CIP cycle in a Vietnamese dairy plant:

1. Pre-rinse with hot water at 60–70°C for 5 minutes
2. Caustic wash with 1–2% NaOH at 70–80°C for 15–20 minutes
3. Intermediate water rinse
4. Acid rinse with 0.5–1% HNO₃ or H₃PO₄ at 60°C for 10 minutes
5. Final rinse with hot or sterile water

SIP (Sterilize-in-Place) uses saturated steam at 121°C for 15 minutes or 134°C for 3 minutes.

Bearings in direct CIP flow paths — such as CIP pumps and butterfly valves — undergo repeated thermal-chemical cycles every 4–8 hours. Standard NBR rubber seals cannot withstand prolonged hot NaOH exposure — they swell and harden within 6–12 months. EPDM or PTFE seals are required.

Selecting food-grade bearings

Per 3-A Sanitary Standards (3-A SSI 03), bearings installed in food-contact equipment must meet:

• Housing and inner/outer rings: AISI 316L stainless steel (equivalent to DIN 1.4404)
• Balls or rollers: AISI 440C or ceramic Si₃N₄
• Seals: PTFE, EPDM, or FDA-compliant elastomer
• Grease: H1 group (NSF/ANSI 61 or H1 registration)

SKF Food Line provides a complete series: 316L housing, AISI 440C balls, EPDM seals, factory-filled with LGFQ 2 (H1) grease. Identification suffix: /H or /VK388 depending on type. Example: 6308-2RS/VK388 — functionally identical to standard 6308-2RS but with all food-grade components throughout.

ZVL Inox line (ZVL Slovakia) manufactures 316L stainless steel bearings to EU standards, suffix /SA or /INOX. Quality equivalent to SKF Food Line, with competitively priced options — well suited for mid-size dairy plants managing maintenance budgets without compromising hygiene standards.

The standard grease mistake

The most common error in Vietnamese dairy plants: maintenance technicians apply EP2 lithium grease on filler bearings because it is cheap and readily stocked. EP2 carries no H1 certification. If discovered in a hygiene audit, the entire production batch faces recall risk.

H1 greases readily available in Vietnam:

Brand comparison

SKF Food Line

SKF is the largest food-grade bearing supplier in Vietnam, with a wide distribution and technical support network. The SKF Food Line catalogue lists over 800 standard 316L bearing codes covering essentially every position in a dairy plant.

Strengths: comprehensive technical documentation, online SKF Bearing Calculator for life estimation, OEM support for Tetra Pak and GEA equipment. Limitation: list prices typically run 20–35% above comparable EU alternatives.

ZVL Inox

ZVL Slovakia manufactures bearings to ISO 355 and DIN 5412 standards at its EU facility. The Inox line uses AISI 316L steel with quality control under EN ISO 9001. Multiple dairy plants in Vietnam — particularly in the Mekong Delta — have adopted ZVL Inox for conveyors, sanitary pumps, and filling heads, realizing meaningful cost savings versus SKF/FAG. Best fit: non-OEM-critical positions where the equipment manufacturer does not mandate a specific brand.

FAG Stainless

FAG (Schaeffler) offers suffix /VT379 (316L housing, Arcanol FOOD2 grease). Quality equivalent to SKF Food Line. Commonly selected at plants already standardized on Schaeffler for industrial equipment — convenient to unify suppliers.

Brand comparison table

Real-world case study

At a fresh-milk dairy producing 150,000 liters per day in Binh Duong province, the engineering team dealt with a recurring failure: frozen-store evaporator fans (–22°C) burned out motors an average of 3–4 times per year. Each event cost 6–8 hours of downtime and approximately 40–60 million VND in repairs plus temperature excursion losses.

Analysis of the removed bearings showed hard, caked grease and dry ball surfaces — no spalling from overload. Root cause: the plant was using standard EP2 grease (SKF LGMT 2), which has a minimum operating temperature of 0°C and is entirely unsuitable for frozen environments.

Solution: replaced all 24 evaporator fan bearings with 6205-2RS pre-packed with Arcanol TEMP90 (rated –50°C to +90°C). Total replacement cost: approximately 18 million VND (bearings plus labor). Outcome after 18 months of monitoring: zero recurrences. ROI turned positive within the first three months.

Key lesson: the failure was not caused by inferior bearings — it was caused by wrong grease. Standard 6205-2RS is entirely adequate for the load and speed. Only the correct grease suffix for the operating temperature was missing.