The Spirax Sarco SCA series comprises maintainable carbon steel inverted bucket steam traps with integral strainers for a wide range of operating pressures. Available in sizes DN15 to DN25, with threaded, socket weld or flanged connections, and models from SCA3 to SCA40 selected according to maximum differential pressure.
Front product view of the Spirax Sarco SCA inverted bucket steam trap
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SCA Inverted Bucket Steam Trap | Spirax Sarco
Maintainable inverted bucket steam trap for condensate drainage from steam mains and equipment, with integral strainer and sizes from DN15 to DN25.
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Specifications
- Steam trap type
- Inverted bucket steam trap
- Body material
- Carbon steel ASTM A105
- Cover material
- Carbon steel A216 WCB
- Integral strainer
- Yes
- Serviceability
- Repairable type
- Body design conditions
- ANSI/ASME 300 (PN50)
- Maximum allowable pressure
- 51 bar g
- Maximum allowable temperature
- 400°C
- Cold design hydrostatic test pressure
- 78 bar g
- Nominal sizes
- DN15 (1/2"), DN20 (3/4"), DN25 (1")
- Connection type
- BSP/NPT threaded, socket weld (ANSI B16.11), PN40 / ANSI 150 / ANSI 300 flanged
- Maximum differential pressure models
- SCA3, SCA5, SCA11, SCA15, SCA30, SCA40
- Standard supply models
- SCA15, SCA30, SCA40
- Material certificates
- EN 10204 3.1.B available
Application scenarios
Steam system condensate discharge
For condensate discharge from steam mains and equipment. The SCA series is a repairable carbon steel inverted bucket steam trap. The trap body must be installed vertically, with the inlet and outlet at the same horizontal level, and below the drainage point to maintain a water seal.
Selection for different differential pressure conditions
Select SCA3 to SCA40 according to the maximum differential pressure. SCA15, SCA30, and SCA40 are standard products; SCA3, SCA5, and SCA11 can be ordered as required. For flanged connections, also check whether the flange pressure limit matches the internal mechanism differential pressure.
Selection points
Repairable carbon steel inverted bucket design
The SCA series is a repairable carbon steel inverted bucket steam trap. The body is ASTM A105 carbon steel and the cover is A216 WCB carbon steel.
Integral strainer
The SCA series is fitted with an integral strainer, making it a selection criterion when the steam trap needs integrated filtration.
Multiple sizes and connection options
The product is available in DN15, DN20, and DN25 sizes, with BSP or NPT threaded, ANSI B16.11 socket weld, and PN40, ANSI 150, or ANSI 300 flanged connections.
Select the SCA model by maximum differential pressure
The SCA series offers maximum differential pressure models SCA3, SCA5, SCA11, SCA15, SCA30, and SCA40. SCA15, SCA30, and SCA40 are standard supply models and should be selected according to the system maximum differential pressure.
Defined pressure and temperature design limits
The body design condition is ANSI/ASME 300 (PN50), the maximum allowable pressure is 51 bar g, the maximum allowable temperature is 400°C, and the cold design hydrostatic test pressure is 78 bar g.
Installation & maintenance notes
Installation orientation and water seal requirements
The SCA series must be installed vertically, with the inlet and outlet at the same horizontal level, and below the drainage point to maintain a water seal. If installed incorrectly or if the water seal cannot be maintained, the inverted bucket will not operate correctly, possibly causing steam blow-through or failure to discharge condensate.
Verify differential pressure and flange pressure limits
Before selection and installation, select SCA3 to SCA40 according to the actual maximum differential pressure, and confirm that the flange pressure limit is higher than the internal mechanism differential pressure limit; the saturated steam pressure limits for ANSI 150, PN40, and ANSI 300 are 14.1, 36.1, and 41.6 bar g respectively.
Isolate and depressurize before maintenance and replace gaskets
Before maintenance, close the isolation valves upstream and downstream, confirm that the pipeline is depressurized, and wait for the body to cool to ambient temperature. It is recommended to replace the gasket after each repair. The cover gasket contains a stainless steel support ring and must be handled with care.
Reassemble using the recommended torque
When reassembling, tighten the cover bolts, strainer cap, valve seat, and valve plug guide screws to the recommended tightening torques. See the torque table on the product page and the installation and maintenance instructions for specific values.
FAQ
What is the operating principle of the Spirax Sarco SCA inverted bucket steam trap and where should it be installed for drainage?
The SCA series uses an inverted bucket mechanism. The up-and-down movement of the bucket under steam and condensate conditions controls the opening and closing of the valve plug to discharge condensate from steam mains and equipment. The series has an integral strainer and must be installed below the drainage point to maintain the water seal inside the trap and support normal operation.
How should SCA3, SCA5, SCA11, SCA15, SCA30, and SCA40 be selected according to differential pressure?
These models correspond to maximum differential pressures of 3, 5, 11, 15, 30, and 40 bar respectively, and all are available in DN15, DN20, and DN25 sizes. Selection should be based on the actual maximum differential pressure between the trap inlet and outlet, and the allowable pressure of the selected connecting flange should also be checked against the application: the saturated steam pressure limits are 14.1 bar g for ANSI 150, 36.1 bar g for PN40, and 41.6 bar g for ANSI 300. SCA15, SCA30, and SCA40 are standard supply models.
What sizes and connection methods are available for the SCA series, and how do they match existing piping?
The SCA series covers DN15 (1/2 inch), DN20 (3/4 inch), and DN25 (1 inch). Available connections include BSP or NPT threaded, socket weld to ANSI B16.11, and PN40, ANSI 150, and ANSI 300 flanged connections. During procurement and engineering selection, confirm the pipe nominal size, connection standard, and flange pressure rating at the same time to avoid a mismatch in connection standard or pressure rating.
What are the pressure, temperature, and main material conditions for the SCA inverted bucket steam trap?
The body design condition for this series is ANSI/ASME 300 (PN50), the maximum allowable pressure is 51 bar g, the maximum allowable temperature is 400°C, and the cold design hydrostatic test pressure is 78 bar g. The body is ASTM A105 carbon steel and the cover is A216 WCB carbon steel; the bucket, strainer screen, internal sleeve, and other main internal parts are stainless steel. Actual maximum operating conditions are also limited by the selected orifice size and connection type.
How should the SCA series be installed and maintained?
During installation, the trap body should remain vertical so the bucket can move vertically up and down. The inlet and outlet should be at the same horizontal level, and the trap should be located below the drainage point. Before maintenance, close the isolation valves upstream and downstream of the trap, confirm that the pipeline has been depressurized, and wait for the body to cool to ambient temperature. After disassembling internal components, replace the gasket. Cover bolts, strainer cap, valve seat, and other parts should be reassembled to the specified torque.