Product details
Weiss Bimetal Thermowell | BN12-75BS | 12″ Length | Brass | 2.5″ Lagging Extension
Product Description
The BN12-75BS is the specialized socket for 12-inch (300 mm) stem bimetal thermometers. The “BN” designation identifies this as a Bimetal Thermowell with a Stepped Stem design and a Lagging Extension.
In the UAE’s district cooling and large-scale infrastructure projects, main chilled water headers can be very large and require thick thermal insulation. The BN12-75BS is engineered for these specific conditions: it features a 2.5-inch (64 mm) lagging extension (T-dimension) to clear the insulation, combined with a 9.5-inch (241 mm) insertion depth (U-dimension). This ensures the thermometer’s sensing tip is positioned deep within the core of the fluid stream for maximum accuracy. The stepped-stem design further enhances performance by reducing thermal mass at the tip for a faster response time.
Key Features
- Extra-Long 12″ Nominal Length: Ideal for large-diameter pipes (12″ and above) where deep immersion is required to reach the center of the flow.
- 5″ Lagging Extension: Provides ample clearance for thick pipe lagging, ensuring the thermometer dial remains visible and protected from burial within the insulation.
- Stepped Stem Design: Reduces the diameter at the sensing end to allow the bimetal element to react more quickly to temperature fluctuations.
- Premium Brass Construction: Delivers excellent heat transfer and corrosion resistance in chilled water, hot water, and non-aggressive fluid systems.
- 1/2″ NPT Instrument Thread: Specifically threaded for standard bimetal thermometers with a 1/2″ NPT fixed connection.
Technical Specifications
| Specification | Details |
| Brand | Weiss Instruments |
| Model | BN12-75BS |
| Nominal Stem Length | 12″ (300 mm) |
| Insertion Length (U) | 9.5″ (241 mm) |
| Lagging Extension (T) | 2.5″ (64 mm) |
| Material | Brass |
| Stem Design | Stepped Shank |
| Process Connection | 3/4″ NPT |
| Instrument Connection | 1/2″ NPT (Standard for Bimetal) |
| Application | Large Diameter Insulated Piping / District Cooling |
Frequently Asked Questions
- Q: Which thermometer fits the BN12-75BS?
- A: It is designed for any standard bimetal dial thermometer with a 12-inch stem, such as the Weiss 3BBM12 or 5BBM12 series.
- Q: Why is the immersion (U) length only 9.5 inches on a 12-inch well?
- A: The 12-inch “Nominal” length includes the 2.5-inch lagging extension and the threaded portion. The 9.5-inch immersion is the actual length that sits inside the pipe.
- Q: Is this suitable for saline or sea water?
- A: For sea water or highly corrosive fluids, brass is not recommended. In such cases, the 316 Stainless Steel (BN12-75SS) version should be used.