A steam separator is a pressure-vessel device that removes entrained water from wet steam by forcing the flow across baffles or into a cyclone body, targeting a delivered dryness fraction of 0.98 or better to the downstream cylinder or turbine [S1].
China's steam-system supplier base runs an estimated 800-1,000 steam-trap and steam-separator factories, of which roughly 20% qualify as large-scale and the rest cluster in the low-to-mid end as fragmented small and medium enterprises [S2].
How a steam separator separates droplets
The operating principle rests on density contrast: water at roughly 950 kg/m3 and steam at roughly 3.6 kg/m3 (8 bar abs) give a density ratio near 264x, so a sharp 90 degree or 180 degree turn across a baffle stack, or a tangential cyclone entry, forces droplets to impact the baffle face while steam follows the curve [S1].
Best inlet velocity for a baffle-type unit sits between 15 and 25 m/s; below 10 m/s droplets lack the momentum to leave the streamline, while above 30 m/s re-entrainment off the baffle carries water out the outlet, defeating the unit even when it is correctly sized [S1].
The drain pocket underneath the separation chamber needs a steam trap rated for the condensate load, because a failed trap fills the pocket, lifts the water level into the chamber, and turns the separator into a humidifier feeding full-flow wet steam downstream [S1].
China supplier landscape: Big Three versus mid-tier
The domestic supplier base is dominated by the "Big Three": Gansu Hongfeng 920, Fujian Yingqiao, and Beijing Valve General Factory, all qualified to CNPC and Sinopec procurement lists and widely specified across petrochemical plants [S2].
The trade-off is price, since the Big Three command a premium and sit in a tight pool of roughly 20 recognized domestic suppliers, while a much larger cohort of small and medium enterprises competes on cost in the low-to-mid end with variable quality [S2].
Foreign brands retain a strong foothold: Armstrong, Spirax Sarco, VENN, TLV, and ARI are widely installed inside Chinese plants, and several Taiwanese brands operate mainland production, which the mid-tier domestic suppliers benchmark against [S2].
Separator types and where each fits
Baffle-type units with a sharp change in flow direction suit low-to-medium flow steam mains and are the most common configuration for general plant service, with separator body ratings matched to the line pressure class [S1].
Cyclone separator designs impart a spin to the flow so droplets are thrown outward by centrifugal force; they are standard on stationary boilers and nuclear steam generators where higher separation efficiency per vessel volume is required [S3].
The simplest configuration is the steam dome on a steam locomotive, but for industrial service the choice is normally between a baffle vessel, a cyclone body, or a combination of the two where carryover limits are tight [S3].
Selection criteria versus the options
Comparing the three main options against the same set of decision criteria: baffle separators score low on cost and ease of maintenance, score adequate on efficiency at moderate velocities, and lose out on footprint at high flow; cyclone separators score higher on efficiency per vessel volume and on footprint, but cost more and have a tighter inlet-velocity band; combination vessels score highest on dryness-fraction guarantees but at the highest capital cost and largest installed length [S1][S3].
For sizing, the practical inlet-velocity window is 15-25 m/s for baffle units, with the dry steam target at 0.98 or higher dryness fraction and a corresponding dynamic-pressure indicator of around 0.72 kPa for steam at the design point versus roughly 190 kPa for the water phase at the same velocity [S1].
Specifiers comparing a baffle unit against a cyclone separator for a turbine feed should weight the dryness-fraction requirement, the allowable pressure drop, and the trap capacity at the drain pocket, because a separator that cannot be drained is functionally useless regardless of its dry-side efficiency [S1].
Failure modes and field symptoms
The clearest field symptom of a failing separator is the engine or turbine starting to thump on every revolution within about 30 seconds of opening the regulator or control valve wide, which is the cylinder taking liquid water [S1].
Three failure modes drive that symptom: a drain trap that has failed closed and filled the pocket, a scale-blanked inlet strainer that chokes the unit and shifts the velocity band, and a baffle face eroded or coated so that droplets no longer coalesce cleanly [S1].
The remedy sequence is consistent: pull the trap, inspect the float or bucket mechanism, and confirm the strainer is clean before any conclusion about the boiler is drawn, because each of these three items produces the same downstream signature [S1].
Standards, quality, and sourcing guidance
For specification work, a steam separator is treated as a pressure vessel and is therefore paired with material, weld, and test requirements drawn from the same codes that govern the upstream steam header; buyers should require documented pressure ratings, hydrotest certificates, and material traceability for any separator destined for a CNPC or Sinopec-qualified site [S1][S2].
For projects outside the Big Three shortlist, the practical filter is CNPC or Sinopec supplier qualification plus documented export track record, since the factory-level statistics show only about 20% of Chinese steam-system plants meet large-scale enterprise thresholds and the remaining 80% carries the quality risk that drives the price gap [S2].
For a deeper look at the velocity, pressure-drop, and sizing math behind baffle versus cyclone selection, the related spec-map article on Steam Separator Sizing and Selection walks the inlet-velocity band and dryness-fraction trade-offs in detail.