Technical content reviewed: 18 July 2026, against the current Spirax Sarco separator product range, S13 technical information (TI-P023-26), CS10-1 technical information (TI-P023-59) and separator installation guidance (IM-P023-55). Product availability, materials, connections and certified operating limits vary by market and document revision. Confirm the current document for the selected model before sizing or ordering.
What does a Spirax Sarco steam separator do?
A Spirax Sarco steam separator removes entrained liquid droplets from steam before the steam reaches pressure reducing valves, control valves, flowmeters, heat exchangers or other moisture-sensitive equipment. Internal changes in direction and velocity cause the denser water droplets to separate from the steam flow and collect at the drain connection.
Separating entrained moisture can improve delivered steam quality, reduce erosion and corrosion, support stable heat transfer and help protect downstream equipment. The separator does not remove dissolved impurities or non-condensable gases, and it cannot correct the underlying causes of wet steam such as poor boiler operation, inadequate main drainage or excessive steam velocity.
Steam separator, steam trap and strainer: different functions
| Component | Primary function | What it removes | Important limitation |
|---|---|---|---|
| Steam or moisture separator | Separates entrained liquid droplets from a moving steam, compressed-air or gas stream. | Free liquid carried in the flow and, depending on design and service, some entrained particles. | The collected liquid remains in the separator until a drainage device removes it. |
| Steam trap | Automatically discharges condensate and suitable non-condensable gases while retaining live steam. | Condensate that reaches the trap inlet. | A trap does not provide the same droplet-separation volume and internal flow path as a separator. |
| Pipeline strainer | Captures solid debris in a removable screen. | Rust, scale, weld debris and other solid particles above the screen opening. | A strainer is not designed as the primary device for separating entrained water from steam. |
How moisture separation works
Steam separators commonly use baffles, vanes or a change in flow direction to create inertia. Steam follows the designed flow path, while heavier droplets cannot change direction as quickly and strike an internal surface. The liquid coalesces, falls into the lower part of the body and leaves through the drain connection.
Effective performance depends on the separator geometry, flow velocity, droplet loading and drainage. A separator that is flooded because its trap is isolated, undersized or incorrectly installed cannot maintain its intended separation function. Insulation can also matter because heat loss from an uninsulated body creates additional condensate.
Compare Spirax Sarco separator routes
The current CMS provides direct product routes for the S13 general-service separator and CS10 clean steam separator. Other materials, pressure classes and fabricated separator families may be available through the wider product range; use the current regional documentation to confirm availability.
| Product route | Construction and service direction | Typical application | Key checks |
|---|---|---|---|
| Spirax Sarco S13 separator | Flanged SG iron, baffle-type separator for steam, compressed air and compatible gas systems. | General industrial mains and branch lines where entrained liquid must be removed before downstream equipment. | Exact flange standard, nominal size, pressure and temperature limits, drain connection and insulation requirement. |
| Spirax Sarco CS10 clean steam separator | Traceable 316L stainless-steel construction with hygienic connection and finish options. | Clean and pure steam systems where dryness, material traceability, inspectability and hygienic construction are important. | Connection standard, surface finish, seal material, certification, drainage arrangement and current clean-steam requirements. |
| General separator range | Product families may include SG iron, carbon steel, stainless steel and fabricated constructions. | Higher pressure, larger line size, alternative connection standards or material-specific duties. | Regional availability, design pressure, material, connection, line velocity, pressure drop and model-specific sizing information. |
Verified S13 and CS10-1 reference data
The following values are model-specific reference points taken from the cited Spirax Sarco documents. They do not replace the complete pressure/temperature shell conditions, capacity method, connection restrictions or current regional issue of the technical information.
| Model | Verified item | Published reference | Source |
|---|---|---|---|
| S13 | Nominal size range | DN40 to DN200 | TI-P023-26 |
| S13 | Body design rating | PN25 | TI-P023-26 |
| S13 | Maximum allowable pressure reference | 25 bar g at 100°C | TI-P023-26 |
| S13 | Maximum allowable temperature reference | 350°C at 14 bar g | TI-P023-26 |
| CS10-1 | Nominal size range | ½ inch to 2 inches | TI-P023-59 / STR1013-US |
| CS10-1 | Construction and inspection | Traceable 316L stainless steel with a removable internal baffle | TI-P023-59 / STR1013-US |
| CS10-1 | Published surface finish | Internal 20 μ-in Ra (0.5 μm) electropolished; external 63 μ-in Ra (1.6 μm) satin bead blast | STR1013-US |
| CS10-1 | Connection routes | Sanitary clamp or tube weld ends | TI-P023-59 / STR1013-US |
| CS10-1 | Published performance statement | Designed to achieve steam dryness above 95% | STR1013-US |
Where should a steam separator be installed?
Install a separator where wet steam could affect control, measurement, heat transfer, process quality or equipment life. The best location is normally close enough to the protected equipment that condensate cannot readily reform between the separator and the point of use.
- Upstream of a pressure reducing valve or complete steam pressure reducing station.
- Upstream of control valves, especially where erosion, unstable control or wet-steam damage is a concern.
- Before steam flowmeters and measurement stations that require a defined steam condition.
- At the inlet to heat exchangers, process vessels and other equipment where stable heat transfer depends on steam quality.
- On distribution mains or branches exposed to condensate carryover, poor drainage or sudden changes in demand.
- Before turbines or other high-speed equipment when the equipment supplier requires moisture separation.
Review the wider steam distribution guide when main sizing, drainage pockets, branch connections, insulation and condensate return need to be assessed as one system.
Engineering data needed for separator selection
A separator should be selected from the complete duty rather than the pipe size alone. Record normal, minimum and maximum conditions and confirm the selected model against its current sizing method.
| Required input | Why it matters |
|---|---|
| Fluid and steam condition | Confirms whether the duty is plant steam, clean steam, compressed air or another compatible gas and identifies material or hygiene requirements. |
| Operating and design pressure | Determines pressure class, certified limits and the density used in velocity or sizing checks. |
| Operating and design temperature | Confirms body, internal, seal and connection suitability. |
| Maximum, normal and minimum flow | Defines velocity through the separator and whether performance remains suitable across the expected load range. |
| Line size and connection standard | Establishes physical compatibility, available models and whether reducers or a fabricated route are required. |
| Allowable pressure drop | Prevents the separator and connecting pipework from consuming pressure needed by downstream equipment. |
| Expected moisture load | Influences separator duty and the required capacity of the drain trap and downstream condensate line. |
| Material, finish and certification | Separates general industrial selection from clean or pure steam duties requiring traceability and hygienic construction. |
Design the separator drainage arrangement
The separator drain must discharge condensate as it collects without allowing live steam to pass continuously. Select the steam trap for the available differential pressure, condensate load, start-up demand, backpressure and required air-venting behavior. The trap connection should not create a water seal or excessive lift that prevents free drainage from the separator body.
For many continuous separator duties, a suitably sized float-type trap is a common engineering route because it can discharge condensate as it forms, but the exact trap type must be confirmed from the service and current application guidance. Review the ball float steam trap range alongside the complete steam-trap options.
- Provide isolation that allows safe maintenance without leaving the separator unintentionally flooded.
- Fit the separator with its drain connection vertically downward unless the model instructions state otherwise.
- Keep the drain line adequately sized and avoid configurations that impose unverified backpressure.
- Route trap discharge and any blowdown safely into the condensate system specified for the site.
- Insulate the separator where required, while keeping identification and service points accessible.
Clean steam and hygienic separator duties
Clean and pure steam systems require more than a corrosion-resistant body. The separator may need traceable material, controlled internal surface finish, hygienic connections, suitable seals, drainability and access for inspection. The clean steam product range provides the wider context for filters, traps, valves and other components used with the CS10.
Installation and commissioning checks
- Verify the flow direction, body orientation and drain position against the exact installation manual.
- Confirm that piping loads, alignment and flange or hygienic connections do not stress the body.
- Clean and flush new pipework before commissioning so construction debris does not enter the separator or drain trap.
- Check that the steam trap, isolation valves and discharge route are correctly installed and operational.
- Warm the system gradually and inspect connections for leakage.
- Observe separator drainage at start-up, normal load and peak demand; investigate retained condensate, waterhammer or unstable downstream operation.
- Maintain insulation and weather protection without hiding corrosion or preventing safe inspection.
Common steam separator problems
The separator remains full of condensate
Check that the drain isolation valves are open, the trap is correctly sized and installed, and the discharge line is not blocked or exposed to excessive backpressure. A functioning separator cannot protect the system if collected liquid cannot leave the body.
Wet steam symptoms continue downstream
Confirm actual steam flow, line velocity, separator size and installation orientation. Also inspect upstream main drainage, boiler carryover, insulation and the distance between the separator and protected equipment. New condensate can form downstream of a correctly operating separator.
Pressure loss is higher than expected
Compare the actual flow and pressure with the current sizing data. An undersized separator, unexpected peak load, internal obstruction or incorrectly sized connecting pipework can increase pressure drop.
Waterhammer occurs near the separator
Investigate drainage rather than assuming the separator itself is the cause. Retained condensate, an incorrectly arranged trap discharge, inadequate steam-main pockets or rapid start-up can create damaging slugs of water.
Frequently asked questions
Is a steam separator the same as a steam trap?
No. A separator removes entrained droplets from the moving steam and collects the liquid. A steam trap discharges that collected condensate while retaining steam. A practical separator installation normally requires both functions.
Does every steam line need a separator?
Not necessarily. The decision depends on steam quality, drainage, velocity, equipment sensitivity and process requirements. Separators are particularly valuable before pressure control, measurement and critical heat-transfer equipment or where wet steam is known to occur.
Can a separator remove solid debris?
Some separator designs may capture entrained particles, but a pipeline strainer is the dedicated component for solid debris. Use each device for its intended duty and check whether both moisture and solids must be controlled.
How is a steam separator sized?
Use the manufacturer's model-specific method with steam pressure, maximum and minimum flow, line size, allowable pressure drop and moisture load. Do not select solely by matching the nominal pipe diameter.
When should a clean steam separator be used?
Use a clean steam route when the process requires hygienic connections, controlled surface finish, traceable materials, inspection access or other documented quality attributes beyond a general industrial separator.
Official product information and installation documents
Use the current product document for materials, pressure and temperature limits, dimensions, sizing, installation, drainage and spare parts. These official references were accessible when this page was reviewed:
- Spirax Sarco separator product range
- S13 SG iron separator — technical information (TI-P023-26)
- CS10-1 clean steam separator — technical information (TI-P023-59)
- S1, S2, S3, S5, S6, S7, S8, S12 and S13 separators — installation and maintenance instructions (IM-P023-55)
Select the complete moisture-removal arrangement
Steam separator selection is part of a wider steam-quality and drainage design. Confirm pipe sizing, condensate pockets, insulation, separator duty, steam-trap capacity, discharge backpressure, maintenance access and the protected equipment requirements before ordering. Explore the Spirax Sarco separator range, or contact Spirax Sarco with the steam pressure, flow range, line size, connection standard, moisture condition and application details for review.