Description
This is a robust, corrosion-resistant fitting, typically made from high-strength plastic such as glass-filled Polypropylene (PP) or PVC. It features a large male or female thread designed to screw directly into the 4-inch standard threaded port found on the top of commercial FRP pressure vessels (often 14 inches in diameter and larger). The plug often includes an integrated O-ring or requires an external gasket/sealant to ensure a completely leak-proof, high-pressure seal.
Features
- Positive Seal: Designed to completely and securely close off a vessel port.
- Thread Standard: Compatible with the standard 4-inch thread on commercial FRP vessels (often 4″ NPSM).
- Material: High-grade, food-safe (often NSF certified) plastic offering excellent resistance to corrosion from water, common treatment chemicals, and mineral media.
- Durable: Built to withstand the maximum operating pressure of standard FRP vessels (typically up to 150 psi / 10 bar).
- Tool-Ready: May feature a large wrench flat, handle, or hex head for easy installation and removal with standard tools.
What Does It Do?
The primary function of the 4-inch Threaded Vessel Plug is to permanently seal an unused port on a water treatment vessel. This is necessary in a few scenarios:
- Top-and-Bottom (T/B) Port Vessels: Many large vessels have both a 4-inch top opening and a 4-inch bottom opening. If the vessel is configured to operate with a distributor tube running only through the top, the bottom port is sealed with this plug.
- Conversion: Used to convert a versatile T/B port tank into a standard top-port tank, ensuring the vessel maintains its full pressure rating.
- Temporary Sealing: Used to seal the vessel opening during shipping, storage, or for pressure testing before a control valve or other fitting (like a reducer) is installed.
Good to Know
- FRP Vessel Compatibility: The plug is specifically for FRP (Fiberglass Reinforced Plastic) pressure vessels used for water softeners, activated carbon filters, multimedia filters, and iron removal systems. It is generally not for use with Reverse Osmosis (RO) pressure vessels, which have a different design.
- Sealant is Key: Even with an O-ring, applying a good quality PTFE thread seal tape or paste to the threads is highly recommended to prevent any weeping under pressure.
- Thread Confusion: Ensure the thread type (e.g., NPSM) of the plug matches the thread of the vessel opening.
| Attribute | Details |
|---|---|
| Nominal Size | 4 inch |
| Connection Type | Male or Female Thread (Varies by plug design) |
| Material | Glass-Filled Polypropylene (PP) or PVC |
| Standard | Typically compliant with FRP vessel standards (e.g., NSF/ACS certified materials) |
| Max Pressure | Up to 150 psi / 10 bar |
| Max Temperature | Up to 120°F / 49°C Standard Water Treatment Range |
Maintenance
The plug itself is virtually maintenance-free.
- Inspection: During any system downtime or media change, visually inspect the plug and its threads for any signs of cracking or damage.
- O-Ring Check: The primary point of maintenance is the O-ring or sealing surface. If the plug is removed, replace the O-ring to ensure a new, positive seal when reinstalled.
- Torque: When reinstalling, tighten the plug firmly but do not over-torque it, as this can crack the plastic threads of the plug or the vessel port. Use the manufacturer’s recommended torque specification if available.
What’s in the Box?
- 1 x Threaded Vessel Plug (4 inch)
- 1 x O-Ring / Gasket (Often included)
Dimensions
- Nominal Thread Diameter: 4 inches
- Overall Diameter (Head): 115mm to 125mm to accommodate the wrench/handle
- Thread Length: 40mm to 60mm
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