Product Overview
The THINKTANK TT-A38Y Series is a dual full-lift spring-loaded safety valve assembly designed for overpressure protection of equipment and piping systems handling steam, air and similar compatible media.
The assembly consists of two TT-A48Y full-lift safety valves of the same model and size mounted on a common Y-type inlet junction.
The nominal diameter of the TT-A38Y refers to the inlet diameter of the common Y-type junction, rather than the nominal size of each individual TT-A48Y branch valve.
The series is available with common inlet sizes from DN50 to DN150 and pressure ratings of PN16, PN25 and PN40.
The listed maximum operating temperature is 350°C.
Assembly Configuration
The supplied product data defines the TT-A38Y as:
TT-A38Y = 2 × TT-A48Y + Y-Type Junction
Pressure from the protected equipment enters through the common Y-type inlet body and is distributed to two TT-A48Y full-lift safety valves.
The two branch valves provide parallel relieving paths through a single common inlet connection.
The complete assembly should be sized according to the required total relieving capacity rather than simply according to the common inlet DN.
Quick Specifications
| Parameter | Specification |
|---|---|
| Model | TT-A38Y |
| Product Type | Dual Safety Valve Assembly |
| Branch Safety Valve | TT-A48Y |
| Configuration | 2 × TT-A48Y + Y-Type Junction |
| Lift Type | Full Lift |
| Main Inlet Size Range | DN50–DN150 |
| Pressure Rating | PN16 / PN25 / PN40 |
| Connection | Flanged |
| Applicable Media | Steam, air and similar media |
| Maximum Operating Temperature | ≤350°C |
| Main DN Definition | Y-type junction inlet diameter |
| Manufacturer | THINKTANK |
How It Works
During normal operation, both TT-A48Y branch safety valves remain closed under spring force.
System pressure enters the common Y-type junction and is transmitted simultaneously to both branch safety valves.
When the protected system reaches the specified set pressure, pressure force acting on the valve discs overcomes the spring force and the valves open according to their operating characteristics.
The process medium is then discharged through the two relief paths, reducing pressure in the protected equipment or piping system.
When system pressure subsequently falls into the reseating range, spring force returns the valve discs toward their seats and the safety valves reclose automatically.
Full-Lift Dual-Valve Design
Each branch of the TT-A38Y assembly uses a TT-A48Y full-lift safety valve.
Under the general performance criteria applicable to this safety valve family:
Lift H ≥ 1/4 d₀
where:
- H = Valve lift
- d₀ = Orifice diameter of each individual branch valve
The dimensional table expresses the combined orifice arrangement as values such as:
- 2 × 20 mm
- 2 × 32 mm
- 2 × 40 mm
- 2 × 65 mm
This indicates that the complete assembly contains two parallel relieving orifices.
The total relieving capacity must be based on the approved performance of the complete dual-valve assembly.
Branch Valve Size Relationship
The TT-A38Y common inlet DN is larger than the nominal size of each individual TT-A48Y branch valve.
| TT-A38Y Main Inlet DN | Corresponding TT-A48Y Branch Valve DN |
|---|---|
| 50 | 32 |
| 80 | 50 |
| 100 | 65 |
| 150 | 100 |
This relationship is important when selecting replacement branch valves, spare parts or checking installation dimensions.
Typical Applications
The TT-A38Y Series can be considered for:
- Steam systems
- Compressed air systems
- Industrial gas systems
- Pressure vessels
- Process piping
- Utility systems
- Boiler-related piping
- Packaged equipment
- Skid-mounted systems
- Applications requiring two full-lift safety valves on a common inlet connection
Final selection should consider the actual medium, set pressure, operating temperature, required total relieving capacity, back pressure and discharge piping arrangement.
General Performance Requirements
| Applicable Medium | Shell Test Pressure Ps | Seal Test Pressure Pm | Blowdown ΔP | Discharge Pressure Pp | Lift Height H |
|---|---|---|---|---|---|
| Steam | — | 90% Pk or the minimum reseating pressure, whichever is lower | When Pk ≤ 0.4 MPa: ΔP ≤ 0.04 MPa; when Pk > 0.4 MPa: ΔP ≤ 10% Pk | ≤1.03 Pk | Full-lift: ≥1/4 d₀; Low-lift: ≥1/20 d₀ |
| Air or other gases | 1.5 PN | When Pk ≤ 0.3 MPa: Pm = Pk − 0.03 MPa; when Pk > 0.3 MPa: Pm = 90% Pk | When Pk ≤ 0.2 MPa: ΔP ≤0.03 MPa; when Pk > 0.2 MPa: ΔP ≤15% Pk | ≤1.1 Pk | Full-lift: ≥1/4 d₀; Low-lift: ≥1/20 d₀ |
| Water or other liquids | — | When Pk ≤0.3 MPa: Pm = Pk −0.06 MPa; when Pk >0.3 MPa: Pm = 80% Pk | When Pk ≤0.3 MPa: ΔP ≤0.06 MPa; when Pk >0.3 MPa: ΔP ≤20% Pk | ≤1.2 Pk | Full-lift: ≥1/4 d₀; Low-lift: ≥1/20 d₀ |
Notes:
- Pk = Set pressure
- d₀ = Orifice diameter
- PN = Nominal pressure
- Actual performance requirements shall be confirmed according to the selected assembly, project specification and applicable standard.
- For the TT-A38Y, the full-lift criterion applies to each TT-A48Y branch valve.
Dimensions
Pressure Rating: PN16 / PN25 / PN40
| DN | L (mm) | L₁ (mm) | B (mm) | DN′ | Orifice d₀ | H Approx. (mm) |
|---|---|---|---|---|---|---|
| 50 | 198 | 225 | 165 | 40 | 2 × 20 | 310 |
| 80 | 230 | 285 | 190 | 65 | 2 × 32 | 335 |
| 100 | 275 | 350 | 230 | 80 | 2 × 40 | 420 |
| 150 | 343 | 400 | 275 | 125 | 2 × 65 | 555 |
Dimensions are for preliminary engineering and layout reference. Final approved dimensional drawings should be confirmed before piping fabrication or installation.
Dual Safety Valve Selection
For correct selection of the TT-A38Y assembly, provide:
- Process medium
- Set pressure
- Operating pressure
- Design pressure
- Operating temperature
- Relieving temperature
- Required total relieving capacity
- Required common inlet DN
- Back pressure
- Pressure rating
- Discharge piping arrangement for both branch valves
- Required materials
- Applicable standards or certification requirements
- Installation orientation
- Available installation space
The total required relieving capacity should be verified against the approved capacity of the complete two-valve assembly.
The two TT-A48Y branch valves should also be supplied in the approved matching configuration.
Engineering Support
THINKTANK supports EPC contractors, system integrators, boiler and pressure equipment manufacturers and industrial users with:
- Dual safety valve assembly sizing
- Total relieving capacity review
- TT-A48Y branch-valve selection
- Set-pressure configuration
- Y-type junction engineering
- Material selection
- Dimensional drawings
- 3D models for system integration
- Existing dual safety valve replacement
- Project-specific technical documentation
With more than 30 years of industrial valve application experience, THINKTANK can support engineered dual-valve safety assemblies and equivalent replacement solutions for steam, air and industrial gas systems.
