MAS Full Port Brass Ball Valve B-3-1/2 | 1/2 in. FNPT
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MAS Full Port Brass Ball Valve — Part No. B-3-1/2
- Part Number: B-3-1/2
- Supplier SKU: VAL-B-31/2
- Brand: MAS (B Series)
- Type: Full-Port Brass Ball Valve
- Nominal Size: 1/2 in.
- Connection: Female NPT × Female NPT (both ends)
- Port: Full port — approximately 0.59 in. opening diameter
- Flow Coefficient: Approximately 15 Cv
- Body / Ball / Stem: Brass
- Seats & Packing: PTFE
- Handle: Lever-style steel, quarter-turn operation
- Stem: Blowout-proof with adjustable packing gland
- System: Plumbing / Marine Plumbing — on/off isolation service
What This Valve Does
The MAS B-3-1/2 is a 1/2-inch full-port brass ball valve designed for reliable on/off isolation in compatible fluid systems. The full-bore design keeps the internal flow path close to the nominal pipe diameter, reducing pressure drop compared with standard-port valves. A quarter-turn lever gives instant visual confirmation of open or closed position.
Note on part number: In this series, the final "1/2" denotes the valve size — this is a 1/2-inch valve. The supplier SKU format (VAL-B-31/2) can read as ambiguous; confirm you are ordering the 1/2 in. size before purchasing.
Compatible Applications
- Fresh water supply and shutoff lines
- Oil lines (confirm fluid compatibility with brass and PTFE)
- Gas lines (confirm installation standard and approval requirements for your jurisdiction)
- General marine plumbing isolation service
- Other compatible liquid or gaseous media at rated pressure and temperature
Fitment & Selection Checklist
- Pipe size: 1/2 in. nominal
- Thread type: NPT (National Pipe Taper) — confirm mating fittings are NPT, not BSP
- Confirm system pressure and temperature are within the valve's rated range
- Confirm fluid compatibility with brass body and PTFE seats/packing
- For marine through-hull or seacock service, verify the complete installation meets applicable standards — a standard inline ball valve is not automatically rated as a seacock
When to Replace
- Leakage through the closed ball or around the stem
- Seized, stiff, or erratic operation
- Visible cracking, corrosion damage, or stripped threads on the body
- Excessive handle or stem play indicating internal wear
Installation Notes
- Apply thread sealant compatible with the system fluid and brass fittings
- Support adjoining pipework — avoid placing mechanical load on the valve body
- Handle parallel to the pipe = open; handle perpendicular = closed
- Use for full-open or full-closed service only — ball valves are not designed for fine flow throttling
Parts Desk Insights
This valve is well suited as a general-purpose shutoff in fresh water, oil, and compatible gas lines where a compact, low-restriction 1/2 in. valve is needed. The full-port design is the right choice any time you want to preserve flow capacity through the line. One common ordering error: customers confuse the supplier SKU format (VAL-B-31/2) and assume this is a larger valve — it is a 1/2-inch valve. If your application calls for a seacock or through-hull valve to a marine standard, confirm the installation requirements separately before using a standard inline ball valve in that role.
Shipping information
In-stock and OEM parts: ship same or next business day.
Locally warehoused items: ship within 1-3 business days.
Special-order items: timeline confirmed after order.
Returns & warranty
Returns & Satisfaction Guarantee
We stand firmly behind the quality of every product we sell. Your confidence matters to us — and we back it with a straightforward 30-Day Satisfaction Guarantee.
If you are not fully satisfied, you may request a return within 30 days of delivery. All returns must receive pre-approval prior to being sent back. Unauthorized returns will not be accepted.
To qualify for a return:
Item must be in new, unused condition
Product must be in its original packaging
All parts, components, hardware, manuals, and accessories must be included
Packaging must be undamaged and suitable for resale
Important:
Electronics are strictly inspected. No returns on open-box electronics. Exceptions may apply only with prior written approval. Any electronic unit that has been installed, powered, activated, or altered may not be eligible for return.
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