Thermo 300 Bar DIN outlet, 7/8 UNF inlet threads

Name: Thermo 300 Bar DIN outlet, 7/8 UNF inlet threads
Brand: Thermo
SKU: XSS-VA378-35A
Price: 99.95 USD
Availability: InStock

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$99.95

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SKU

XSS-VA378-35A

This valve will NOT fit most modern scuba tanks, it is a replacement 300-bar valve intended older high-pressure steel cylinders with the smaller 7/8 UNF opening. This valve is NOT available in a Nitrox Ready version.

The Thermo brand 300 BAR DIN valve with 7/8 UNF neck thread is for Air Service Only. This unique valve is designed for use with smaller neck diameter High Pressure cylinders. The valve is rated for 3500 PSI service pressure.

Details

The Thermo 300 Bar DIN valve with the 7/8 UNF neck thread is made of marine grade brass with triple chrome plating for long life protection in salt water. Easy grip soft rubber safety hand wheel with stainless steel insert ensures long life and large ribs make turning handle easy even when wearing gloves. Valve has a dedicated DIN outlet for air service only at {3500 psi |240 bar} service pressure. Includes Dip Tube for base of valve. This valve has a 5250 psi burst disk.

This 300 bar DIN valve can not be used with yoke regulators. A yoke adapter insert does not exist, and even if it were made, we have never seen a yoke clamp long enough to fit over a 300 bar DIN outlet. There is a yoke-to-din fill adapter device for 300 bar valves, but it is strictly for filling only.

This 300 bar DIN valve will fit older design 3500 psi "Genesis" steel SCUBA cylinders that are forced to use a 300 bar outlet because a valve with a 200 bar outlet AND the proper 7/8 UNF inlet threads to fit the cylinder is not available. If you wish, this valve could also be reduced service pressure with a burst disk change.

This 300 bar DIN valve is marked as suitable for AIR ONLY service and is not available in an oxygen service version. The issue is not the cleanliness or material compatibility of the valve; rather the AIR ONLY restriction is as a result of the design, rated pressure and intended application of the valve itself. XS Scuba, the manufacturer, has communicated to Dive Gear Express that the valve should NOT be aftermarket prepared or modified in a misguided attempt to make it suitable for oxygen service.

More Information

More Information
Brand	Thermo
SKU	XSS-VA378-35A
Weight	1.5 lb
Country of Manufacture	Taiwan
HS Code	9506.29

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Tek Tip

Is My HP Tank 3/4 NPS or 7/8 UNF Neck Threads?

Today, the most common thread form used in the US with SCUBA cylinders and valves is National Pipe Straight also known as NPS. The specific thread form used with most SCUBA cylinders in the US is named 0.750-14 NPSM, often referred to as "3/4 NPS." This thread form is seen on both steel and aluminum modern SCUBA cylinders with service pressures of 2400+ (2640), 3000, 3180+ (3498), 3300 and 3442 psi, and is sealed with a size 214 O-ring. However, when the now defunct Pressed Steel Tank Company began manufacturing their high-density steel 3500 psi service pressure SCUBA cylinder in 1987 (sometimes referred to as "Sherwood Genesis" cylinders... the brandname they were originally sold under) , they used a thread form for the neck opening known as Unified National Standard Fine. The specific thread form used with the steel 3500 psi SCUBA cylinder is named 0.875-14 UNF, often referred to as "7/8 UNF" and is sealed with a size 116 O-ring. Some similar 3500 psi steel tanks manufactured by Asahi were also imported to the US from Japan.

In 2003, PST introduced their modern high-pressure 3442 psi E-series cylinders, and they reverted to the 3/4 NPS threaded opening. This was followed by similar designs from Faber and Worthington. So now there are two different high-pressure steel SCUBA Tanks in use, the long discontinued 3500 psi cylinders with 7/8 UNF threaded opening and the current 3442 psi cylinders with 3/4 NPS threaded opening.

It's very important to understand that the 3/4 and 7/8 trade descriptions do NOT indicate relative sizes of the physical dimensions of the opening! This is because the two thread forms are from two different standards, and the names used to describe them refer to only the trade size and schedule. The 3/4 NPS opening is visibly larger than the 7/8 UNF opening. Another test, if the valve is out of the cylinder, is that a U.S. quarter coin will fit through the 3/4 NPS cylinder neck opening but will not fit through the 7/8 UNF opening.

So how do you figure out what high pressure cylinder you have? Assuming your cylinder was manufactured exclusively for the North American SCUBA market in the last 50 years or so, look at the SCUBA Tank neck for the DOT stamp. If it reads DOT-Xxxxx-3442 it's a cylinder with the common 3/4 NPS threaded opening. If it reads DOT-Xxxxx-3500 it's a cylinder with the relatively rare 7/8 UNF threaded opening. (The Xxxxx is a manufacturer specific four or five digit exemption number that starts with the letters E or SP.) If it's neither 3442 or 3500, then it's something other than a high pressure steel scuba cylinder. For more information see our detailed article titled SCUBA Valves, Regulator Fittings, 200 vs 300 Bar FAQ, and Cylinder Neck Openings

Thermo 300 Bar DIN outlet, 7/8 UNF inlet threads

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