Thermodynamic Steam Trap Manufacturer | BS19H/BS49H Disc Type
• Thermodynamic disc-type — simple, robust, few moving parts<br>
• BS19H-16 (threaded) / BS49H-16 (flanged), PN16, DN15–DN50<br>
• PN25 versions available: BS19H-25 / BS49H-25<br>
• Max working pressure 1.6 MPa (PN16) / 2.5 MPa (PN25), max temp 250°C<br>
• Resists water hammer, operates in any mounting orientation
Thermodynamic Steam Trap — BS19H / BS49H | Gaoshan Valve Manufacturer
Disc-Type Thermodynamic Steam Trap | Model: BS19H-16/25 / BS49H-16/25 | PN16 & PN25 | Threaded (NPT/BSPT) & Flanged (RF) | DN15–DN50 | ≤250°C | For Steam Mains, Drip Legs & Tracing Lines
Thermodynamic Steam Trap — Product Overview
The BS19H / BS49H thermodynamic steam trap — commonly referred to as a disc steam trap or thermodynamic disc steam trap — is the most widely used steam trap design in industrial steam systems worldwide, and the best-selling product in Gaoshan Valve’s steam trap portfolio. Its popularity stems from an elegantly simple operating principle: the entire trap contains only one moving part — a hardened stainless steel disc that cycles open and closed based on the Bernoulli fluid dynamic effect. There are no bellows, floats, levers, or bimetal elements to wear out, making the thermodynamic disc trap exceptionally durable and virtually maintenance-free. The BS19H series features female threaded connections (NPT or BSPT) for compact installations, while the BS49H series provides flanged RF connections for larger pipe sizes and easier maintenance removal. Both PN16 and PN25 pressure classes are available to match a wide range of steam system designs. With its all-metal WCB cast steel body and stainless steel internals, this disc type steam trap is particularly well-suited for steam main drip legs, steam tracing lines, process equipment drainage, and outdoor installations where resistance to water hammer and freeze-thaw cycles is essential. As a thermodynamic steam trap manufacturer with 50 years of experience, Gaoshan Valve delivers CE and ISO 9001 certified quality at factory-direct pricing.
Key Advantages of the BS19H/BS49H Thermodynamic Steam Trap
One Moving Part — Minimal Maintenance
The entire operating mechanism of this disc steam trap is a single stainless steel disc seated on a precision-machined seat. With no bellows, springs, levers, or float mechanisms to wear out or jam, the trap delivers exceptionally long service life with virtually no maintenance — a key reason it remains the preferred choice for steam main drainage worldwide.
Water Hammer & Corrosion Resistant
The all-metal WCB cast steel body and hardened stainless steel disc are immune to corrosion from steam condensate and highly resistant to damage from water hammer — a critical advantage over float and thermostatic traps in steam main applications where water hammer is common during start-up.
Operates in Any Orientation
Unlike float or inverted bucket traps that must be installed in a specific orientation, the thermodynamic disc steam trap operates reliably in horizontal, vertical (upward flow), or inclined piping — as long as the disc chamber is not completely inverted. This flexibility makes it ideal for space-constrained piping layouts and retrofit projects.
Excellent Air Venting During Start-Up
The disc design provides continuous air venting during system start-up. Cold air and condensate keep the disc open, allowing rapid purging of the steam line and preventing air binding in process equipment — critical for steam main and drip leg applications where fast warm-up is essential.
Wide Pressure Range — PN16 to PN25
A single trap size operates effectively across a wide inlet pressure range without adjustment. Both PN16 (1.6 MPa) and PN25 (2.5 MPa) versions are available, covering most industrial high pressure steam trap applications. The thermodynamic principle automatically compensates for pressure variations.
Compact & Lightweight Design
The disc trap design is extremely compact compared to mechanical traps of equivalent capacity. This saves space in tight piping layouts and reduces piping stress. Threaded BS19H models are particularly compact — the DN15 version has a face-to-face length of only 90 mm and weighs under 2 kg, making it ideal for steam tracing line installations.
Thermodynamic Steam Trap — Technical Specifications
| Parameter | BS19H-16 / BS49H-16 | BS19H-25 / BS49H-25 |
|---|---|---|
| Nominal Pressure | PN16 | PN25 |
| Maximum Working Pressure | 1.6 MPa | 2.5 MPa |
| Minimum Working Pressure | 0.05 MPa | |
| Maximum Allowable Temperature | 250°C | |
| Nominal Diameter | DN15 – DN50 | |
| Connection Type (BS19H) | Female Threaded (NPT / BSPT) | |
| Connection Type (BS49H) | Flanged (RF, per GB/T 9113 / JB/T 79) | |
| Suitable Medium | Steam, condensate | |
| Operating Principle | Thermodynamic (disc-type, Bernoulli principle) | |
| Air Venting | Continuous during start-up, automatic | |
Main Parts & Materials
| Part Name | Material |
|---|---|
| Body / Bonnet | WCB Cast Steel |
| Disc | Stainless Steel (hardened) |
| Seat | Stainless Steel (hardened, precision ground) |
| Disc Chamber (Cap) | WCB Cast Steel |
| Gasket / Seal | Graphite Spiral Wound / Metal Ring |
| Bolts / Studs | Alloy Steel (zinc-plated or black oxide) |
Thermodynamic Steam Trap — Model Selection
| Model | Connection | Pressure Class | Size Range | Max Temp. |
|---|---|---|---|---|
| BS19H-16 | Female Threaded | PN16 | DN15 – DN50 | 250°C |
| BS49H-16 | Flanged (RF) | PN16 | DN15 – DN50 | 250°C |
| BS19H-25 | Female Threaded | PN25 | DN15 – DN50 | 250°C |
| BS49H-25 | Flanged (RF) | PN25 | DN15 – DN50 | 250°C |
Selection Tip: For compact installations on small-bore piping (tracing lines, drip legs), choose the threaded BS19H series. For larger pipe sizes or where frequent maintenance access is needed, choose the flanged BS49H series. Select PN25 for systems operating above 1.6 MPa.
How a Thermodynamic Steam Trap Works — Disc Cycling Principle
The BS19H/BS49H thermodynamic steam trap operates on the Bernoulli fluid dynamic principle. The trap consists of a precision-machined seat and a single stainless steel disc that sits on top of the seat, forming a chamber between the disc and the cap. When cold condensate or air enters the trap, it flows easily under the disc, pushing it upward and allowing free discharge — this is why the disc steam trap provides excellent start-up air venting. As steam reaches the trap, a high-velocity steam jet passes under the disc into the chamber. The high-velocity steam creates a low-pressure zone in the chamber (Bernoulli effect) while the pressure under the disc remains at inlet pressure. This pressure differential snaps the disc down onto the seat, closing the trap tightly. Steam continues to fill the chamber, and as it condenses, the chamber pressure gradually drops. When the chamber pressure falls below the inlet pressure, the pressure differential lifts the disc and the cycle repeats. This rapid cycling — several times per minute — ensures that only condensate and non-condensable gases are discharged, while live steam is retained in the system. The cycle timing automatically adjusts to the condensate load: faster cycling under high load, slower under low load. For a detailed explanation, refer to our thermodynamic steam trap working principle guide available on request.
BS19H / BS49H Thermodynamic Steam Trap — Disc Cycling Principle & Structure Diagram
Thermodynamic Steam Trap — Dimensions (mm)
BS19H Series (Threaded Connection)
| DN | Inch | Thread | L (Face-to-Face) | H (Height) | ∅D (Chamber) |
|---|---|---|---|---|---|
| 15 | 1/2″ | RC 1/2″ | 90 | 55 | 78 |
| 20 | 3/4″ | RC 3/4″ | 100 | 55 | 78 |
| 25 | 1″ | RC 1″ | 120 | 60 | 88 |
| 32 | 1-1/4″ | RC 1-1/4″ | 130 | 72 | 108 |
| 40 | 1-1/2″ | RC 1-1/2″ | 140 | 72 | 108 |
| 50 | 2″ | RC 2″ | 160 | 82 | 128 |
BS49H Series (Flanged Connection, PN16 / PN25)
| DN | L (Face-to-Face) | H (Height) | D (Flange OD) | Weight (kg) |
|---|---|---|---|---|
| 15 | 155 | 55 | 95 | 5.0 |
| 20 | 190 | 55 | 105 | 7.0 |
| 25 | 200 | 60 | 115 | 9.0 |
| 32 | 230 | 72 | 140 | 15.0 |
| 40 | 230 | 72 | 150 | 18.0 |
| 50 | 230 | 82 | 165 | 23.0 |
*Note: Flange dimensions per GB/T 9113 / JB/T 79 (PN16 RF). Dimensions are for reference; consult factory for exact dimensions before installation. Thread sizes are RC (BSPT female taper); NPT threads available on request.
Thermodynamic Steam Trap — Installation & Maintenance
- Install with the disc chamber (cap) in the horizontal or vertical-upward position. Do NOT install with the chamber facing downward (inverted), as this can cause the disc to stick in the open position and result in live steam loss
- Provide a strainer (Y-type or basket) immediately upstream of the trap to protect the disc and seat from pipe scale, welding slag, and debris — this is the single most important factor for long disc steam trap service life
- Install isolation valves (gate or ball valves) on both inlet and outlet sides to allow trap removal without system shutdown
- For outdoor installations or in freezing climates, insulate the trap body and downstream piping. Unlike thermostatic traps, disc traps can retain water when closed and may require insulation or steam tracing in sub-zero environments
- Install a test valve or sight glass on the trap outlet to allow periodic verification of proper cycling operation — a healthy thermodynamic trap cycles several times per minute with an audible “click”
- Allow a minimum of 3× pipe diameters of straight pipe upstream of the trap for stable flow conditions
- During start-up, the trap will cyclically discharge air, condensate, and some flash steam until the line reaches operating temperature — this is normal operation, not a sign of trap failure
- If the trap fails to cycle (continuous blowing or continuous closed), check for: (a) seat/disc damage from debris, (b) incorrect orientation, or (c) back-pressure exceeding 50% of inlet pressure
- For steam main drip legs, ensure the drip pocket is adequately sized and the trap is installed at least 300 mm below the steam main to provide a proper water seal
- For steam tracing lines, install the BS19H threaded model close to the tracing line low point to ensure complete condensate drainage
Industrial Applications — Where Thermodynamic Steam Traps Excel
Process Equipment Drip Legs
Steam Tracing Lines
Heat Exchangers
Sterilizers & Autoclaves
Laundry & Textile Processing
Food & Beverage Processing
Outdoor Steam Piping
High-Pressure Steam Systems
Petrochemical & Refinery
Chemical Processing Plants
Power Generation
Quality Standards & Certifications
- Design & Manufacture: GB/T 12247 (Steam Trap)
- Face-to-Face Dimensions: GB/T 12250
- Flange Ends: GB/T 9113 / JB/T 79
- Threaded Ends: GB/T 7306 / ISO 7-1
- Test & Inspection: GB/T 12251 (Steam Trap — Test Methods)
- ISO 9001 Quality Management System Certified
- CE Certified
- 100% hydrostatic shell test at 1.5× rated pressure before shipment
- 100% seat leakage test with steam or air
- Disc and seat hardness test verification for each production batch
Packaging & Shipping
Each BS19H/BS49H thermodynamic steam trap is individually packed with protective threaded caps or flange covers, sealed in a poly bag with desiccant, and secured in a corrugated carton (threaded models) or plywood case (flanged models) for export shipment. The disc chamber is cushioned to prevent impact damage to the seating surface. All shipments include a packing list, material certificate, hydrostatic test report, and operation manual. We support FOB, CIF, DAP, and other Incoterms to suit your logistics requirements.
After-Sales Service
- 18-month warranty from date of delivery under normal operating conditions
- Technical support for trap selection, sizing, and system troubleshooting
- Spare disc and seat kits available for field refurbishment
- Gasket and fastener replacement kits available for maintenance
- On-site inspection and trap survey service available upon request
- Trap selection guide and steam loss calculation support provided free of charge
Compare Gaoshan Steam Trap Series
Not sure which type fits your application? Compare all three Gaoshan steam trap series side by side to find the best match.
| Feature | BS19H / BS49H Thermodynamic (Disc) | CS11H / CS41H Free Float Ball | S44F / S14F Thermostatic (Bellows) |
|---|---|---|---|
| Operating Principle | Thermodynamic disc opens/closes by flash steam pressure differential; single moving part | Free-floating ball rises/falls with condensate level; continuous drainage via float buoyancy | Liquid-expansion bellows responds to condensate temperature; modulates based on subcooling |
| Pressure Rating | PN16 – PN25 | PN16 – PN40 | PN16 |
| Max Temperature | 250°C | 425°C | 203°C |
| Discharge Type | Intermittent (cyclic on/off) | Continuous | Modulated (proportional to temperature) |
| Steam Loss | Low — disc seals tight after each cycle; minor bleed during operation | Very Low — water seal prevents steam leakage; near-zero in normal operation | Very Low — closes before steam reaches orifice; rated ≤0.5% no-load leakage |
| Back-Pressure Tolerance | Moderate — back pressure affects disc cycling frequency; typically ≤50% of inlet | High — float mechanism tolerates significant back pressure; suitable for condensate return | High — ≥80% of inlet pressure; well-suited for closed-loop condensate recovery |
| Freeze Protection | Limited — may retain condensate when closed; requires insulation or tracing in cold climates | Limited — body retains water; requires insulation and/or steam tracing for outdoor use | Built-in — drains completely when cold; element stays open below set temperature |
| Typical Applications | Steam main drip legs, steam tracing lines, outdoor piping where simplicity and durability are key | Heat exchangers, air heater coils, condensate recovery systems, high-pressure/high-temp processes | Low-to-medium pressure heat recovery, freeze-prone areas, HVAC heating, processes needing controlled subcooling |
| DN Range | DN15 – DN50 | DN15 – DN50 | DN15 – DN50 |
| Maintenance | Low — only one moving part (disc); no internal linkage or mechanism | Moderate — float and seat require periodic inspection; internal mechanism has multiple components | Low — bellows element is field-replaceable cartridge; no internal linkage or pivot points |
Steam Trap Selection Guide — Which Type Do You Need?
Answer these 3 questions and our engineers will recommend the right model for your application.
1Where is the trap being installed?
For steam mains, drip legs, and tracing lines, the BS19H/BS49H thermodynamic disc trap is the industry standard — simple, durable, and works in any orientation. For heat exchangers and process equipment, consider CS11H/CS41H float traps or S44F/S14F thermostatic traps depending on your temperature and pressure requirements.
2What is your steam pressure?
The BS19H/BS49H covers PN16 to PN25 (up to 2.5 MPa), making it suitable for most industrial steam systems. For high-pressure applications above 2.5 MPa, the CS11H/CS41H free float ball trap (up to PN40 / 425°C) is recommended.
3What is your priority?
Need minimum maintenance and maximum durability? → BS19H/BS49H (one moving part). Need maximum heat transfer efficiency? → CS11H/CS41H (continuous discharge). Need lowest steam loss and freeze protection? → S44F/S14F (thermostatic modulation).
Case Study: Refinery Steam Main Drainage Upgrade — BS49H Thermodynamic Steam Traps
How a Middle Eastern refinery eliminated trap failures on steam main drip legs by switching to Gaoshan BS49H thermodynamic disc traps
From Frequent Failures to Five Years of Reliable Operation
A major refinery in the Middle East was experiencing persistent steam trap failures on their high-pressure steam main drip legs. The existing float-type traps were failing due to water hammer during start-up and contamination from pipe scale. Each failure meant live steam loss and increased fuel costs.
After replacing 120 traps with Gaoshan BS49H-25 thermodynamic disc steam traps (PN25 flanged), the refinery achieved:
- Zero trap failures over 5 years of continuous operation
- Water hammer resistance during steam main start-up
- Simple on-site maintenance — only the disc needs replacement if worn
- All-orientation installation flexibility in congested pipe racks
Traps Installed
Zero Failures
Warranty Period
Frequently Asked Questions About Thermodynamic Steam Traps
What is the difference between a thermodynamic steam trap and a thermostatic steam trap?
A thermodynamic steam trap (BS19H/BS49H) uses the Bernoulli fluid dynamic effect — a single disc cycles open/closed based on pressure differential created by flash steam velocity. It has one moving part and operates intermittently. A thermostatic steam trap (S44F/S14F) uses a liquid-expansion bellows element that responds to condensate temperature, providing modulated discharge. Thermodynamic traps excel in steam main and drip leg applications where durability and simplicity are priorities; thermostatic traps are preferred for heat recovery and freeze-prone environments.
Can the BS19H/BS49H be used on superheated steam?
The BS19H/BS49H is rated for saturated steam up to 250°C. For superheated steam applications, the thermodynamic disc principle can work, but the trap will cycle differently because there is less condensate to cool the chamber. We recommend consulting our engineering team for superheated steam applications — in many cases, a free float ball trap (CS11H/CS41H, rated to 425°C) is a better choice.
How does the BS19H/BS49H compare to an inverted bucket trap?
Both are widely used for steam main drainage, but key differences: (1) The disc steam trap has one moving part vs. the bucket trap’s internal linkage mechanism — simpler and less to go wrong. (2) Disc traps operate in any orientation; bucket traps must be installed horizontally with the bucket vertical. (3) Bucket traps require a water seal to operate; if the seal is lost (common after shutdown), the trap blows live steam. Disc traps self-seal without a water prime. (4) Bucket traps typically handle larger capacities at very low pressures. For most steam main applications, the thermodynamic disc trap offers superior reliability.
How often does the disc need replacement?
Under normal operating conditions with clean steam and proper upstream filtration, the hardened stainless steel disc typically lasts 3–5 years. The seat may require re-machining or replacement on a similar interval. We supply spare disc and seat kits for easy field refurbishment without replacing the entire trap body. The disc and seat are the only wear parts in the entire trap.
Do you provide thermodynamic steam trap specification sheets and dimensions?
Yes. Full thermodynamic steam trap specifications, dimensional drawings, and material certificates are provided with each shipment. Downloadable PDF specification sheets are available on our website or upon request. Each shipment includes a material certificate, hydrostatic test report, and seat leakage test report. Third-party inspection (SGS, BV, TÜV) is supported.
Get a Quote — BS19H / BS49H Thermodynamic Steam Trap | Factory Direct Pricing
As a thermodynamic steam trap manufacturer with 50 years of experience, Gaoshan Valve offers factory-direct pricing on the complete BS19H/BS49H series. Need help with steam trap selection, sizing, or determining the right pressure class (PN16 vs. PN25)? Contact our engineers today for competitive pricing, thermodynamic steam trap specifications, and technical support.