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What
is the "DIN Standard" referred to in the Storz pages of the catalog?
What is the difference between a forging and a
casting?
What is "Hardcoat Anodize" and why do I need it?
What is a "Higbee"?
Will Storz fittings from Red Head Brass mate with
Storz fittings from other manufacturers?
Why is "Seamless" better than "Structural" extruded
aluminum for firefighting applications?
Are there different types of Storz gaskets?
What is the difference between "NH", "NST", "NPSH",
"IPT", and "NPT" threads?
Why Aren't tapered pipe threads (NPT) available in swivels?
What kind of maintenance should be done on
Couplings and Adapters?
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DIN is an abbreviation for the Deutsches Institut für Normung e. V, an
institution of trade and industry responsible for the preparation of National
Standards in Germany. Storz fittings were patented in Europe by Carl August
Guido Storz over one hundred years ago and are now is use worldwide. DIN
publishes standards for the design of these Storz fittings. Although the
catalog refers to the "DIN Standard," there are actually a number of standards
that apply, one for each size and type of Storz coupling or adapter. All of the
Standards for aluminum fittings are in the DIN 143xx series. For instance, DIN
14303 covers Size B (75mm) Aluminum Delivery Hose Couplings for Fire Brigade
Use. This standard specifies that the Storz head be a DIN 1725 Part 1 Aluminum
forging. Cast aluminum Storz fittings can be used for nonfirefighting, lower
pressure applications such as agriculture. In the interests of the safety of
the "Fire Brigade," all Storz couplings, adapters and caps supplied by Red Head
Brass are made from aluminum forgings.
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Forgings are manufactured by pressing metal under great pressure into parts
that, as a result, have high strength. The metal is typically heated, but not
melted, before forging. In the casting process, the metal is melted before
going into a mold. The metal poured into the mold solidifies as it cools. The
control of the molten metal temperature is critical. Likewise, the quality of
the metal being melted must be controlled so that no impurities get into the
molten metal. Any gases that are trapped can create porosity as the metal
cools. Low casting temperature and impurities, such as sand or slag, can cause
imperfections known as cold shots. Metallurgically, a casting has no grain flow
or directional strength. A casting can contain many unseen defects. Forgings,
on the other hand, have no internal voids that can cause unexpected failures.
The grain structure of a forging is oriented to part shape for greater
strength. A forging has greater density. In general, forgings are seen as
having a higher integrity and greater reliability than castings.
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Not all anodizing is the same. "Hardcoat Anodize" is very specific type of
anodize that gives aluminum parts greater abrasion and corrosion resistance
than that provided by the more conventional plain anodize processes. It is
sometimes referred to as "Alumilite Hard Coat," "Martin Hard Coating," "Hard
Anodizing" or "Hard Coating". The coating is a hard aluminum oxide that is
formed by the electrochemical reaction of aluminum with oxygen. It is
chemically bonded to the aluminum. Hard Anodic Coatings are defined by Military
Specification MIL-A- 8625, Type III, Class 1. In order to meet this
specification, the coating thickness must be held to .002" +/- 20%, pass the
abrasion resistance requirement found in the specification, and be routinely
tested to these parameters to insure quality. Plain, or conventional anodize
has no such requirement for thickness or wear resistance. Other coatings, for
instance paint or powder, likewise have no such requirement for abrasion
resistance. The threaded and non-threaded couplings and adapters used in
firefighting greatly benefit from the abrasion and corrosion resistance
provided by Hardcoat Anodize. It is the specification Red Head Brass follows in
manufacturing its quality aluminum products.
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A "Higbee," also known as a Quick Start Thread, is a modification to the first
thread of a hose thread. The thread is machined back from the end until the
cross section of the thread is full, in other words looks like a fully formed
triangle. Mating threads go together and start quickly. There is no partial, or
thin thread to be rolled over and jam the connection.The full strength of the
thread is available as soon as mating threads are connected. On Rocker Lug
parts, there is a notch in the lug adjacent to the Higbee to help locate the
Higbee for ease of assembly. This is especially important for internal threads
where the Higbee cannot be easily seen. NFPA 1963 requires a Higbee on NH
threads. Taper Pipe Thread, NPT, does not get a Higbee.
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Simply put, as long as they are the same size, they should. Red Head Brass
manufactures Storz fittings to meet the established dimensional standards. As
long as the Storz fittings from other manufacturers meet these standards, the
fittings will mate. The 4" and 5" Storz connections, for example, are included
in NFPA 1963. However, there are numerous sizes of Storz fittings available.
Some are only metric sizes. Others are combination English/Metric sizes. Those
sold domestically are very specific sizes for the U.S. market and are usually
marked with the nominal size in inches. They may also be marked with both
English and Metric units. Red Head Brass currently offers 1" (25mm), 1-1/2"
(38mm), 2" (52mm), 2-1/2" (65mm), 3" (75mm), 4" (100mm), 5" (125mm) and 6"
(150mm) Storz fittings.
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Although they may look the same, structural and seamless tube are two
distinctly different products. The two products are extruded by two different
techniques. "Seamless" is extruded from a hollow billet by the die and mandrel
process or from a solid billet on a piercer press. In either case, the wall of
the extruded tube never separates as the shape is extruded. This results in a
uniform structure with predictable strength throughout. Structural tubing, on
the other hand, is produced by a bridge die or port hole die. The mandrel that
makes the inside diameter of the tube is supported by webs. As the metal passes
through the die it is separated by the webs. As the metal exits the die a
mechanical bond, or weld, is created. The grain structure is often different
where the weld seams are located. The weld seams run down the entire length of
the tube. The seams can often be seen after anodizing. The seams take on a
different color than the surrounding metal. When viewed on end, the seams
appear as spokes on a wheel. There are no standard industry guidelines for weld
seam quality and each producer establishes their own internal criteria. There
are no published burst pressure ratings for structural tube. Manufacturers of
structural tubing do not recommend its use for pressure applications. Test
pressures for fire hose couplings and adapters can be in the 1000-1200 psi
range. For its quality hose couplings and adapters, Red Head Brass machines
these critical components from seamless extruded 6061-T6 aluminum exclusively.
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In general, there are two different types of Storz gaskets, namely Pressure
gaskets and Suction gaskets and they operate in different ways. It is
important, when ordering, to specify the application so that the correct
coupling or adapter, with the proper gasket, is supplied. The gaskets, although
similar, are generally not interchangeable. The Pressure gasket has a lip, or
flap, that is open to the inside, facing the water. As the line is charged, the
lip pushes out tighter and tighter against the lip of the gasket in the mating
coupling to make a waterproof seal. The coupling torque to assemble two mating
pressure couplings is small so that the couplings can easily be connected.
Water may leak out until the pressure in the line rises to push the flaps
together. On the other hand, Suction gaskets have a flap on the outer rim,
facing the outside. The coupling torque to assemble mating suction couplings is
higher so that these flaps on mating couplings are pressed together initially,
sealing out the outside air, so that the draft can be started. As the suction
increases, the flaps are pulled together even tighter. Because of the higher
connection torque, wrenches may be needed to assemble Storz Suction fittings.
Pressure gaskets are black in color. Suction gaskets are grey. NFPA 1963
requires that Suction gaskets be installed in Storz Caps.
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"NH", or National Hose, thread is the thread that has become the standard
thread used in firefighting today. The threads specified in NFPA 1963 are "NH".
This thread was previously known as "NST" or National Standard Thread. "NPSH",
or National Pipe Straight Hose, is slightly smaller in diameter and has more
threads per inch than the same nominal diameter "NH" thread. "NPSH" thread is
sometimes referred to as "IPT", or Iron Pipe Thread. "NH" and "NPSH" threads
are not interchangeable. "NH" and "NPSH" threads are straight threads and
require a gasket for sealing between mating threads. "NPT", or National Pipe
Tapered, is the thread most commonly found in plumbing applications. Being
tapered, the seal between mating threads is made by squeezing the threads
together. No gasket is used. "NPT" and "NPSH" threads are similar in diameter and
threads per inch. For more information on threads, see page 31 of this catalog.
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They typical coupling consists of three main components; male, band, swivel.
The swivel's job is to bring together the male and the band, squeezing a gasket between
them, sealing the water path. With straight threads, like NH and NPSH, the swivel turns on the
male as far as necessary to make this seal. However, NPT threaded components seal by jamming
the mating threads as they are tightened. No gasket is used. The turns required to tighten may vary.
If NPT threads are used in a coupling, the end of the male may not stop at the correct place in the
swivel. The male can be tight into the swivel but, even with a gasket, it may not seal against
the band. This would allow water to leak out of the joint. Thus, NPT threads are not available in swivels.
However, a coupling set with a NPT male and a NPSH swivel can work. NPSH thread is the straight version
of NPT thread. A NPT male will screw into a gasketed NPSH swivel and seal against the band,
provided the end of the male is cut square.
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The NFPA publishes an excellent Standard, NFPA 1962 Standard for the
Inspection, Care, and Use of Fire Hose, Couplings, and Nozzles and the Service
Testing of Fire Hose, that covers this subject very well. Red Head highly
recommends that the Standard be followed. Chapter 6 of the Standard pertains to
Nozzles, Couplings, and Gaskets but the recommendations in the chapter apply
equally well to appliances, such as elbows, wyes, and adapters, both threaded
and non-threaded. In general, NFPA 1962 recommends that these type items be
inspected after each use and at least annually. The annual Service Testing of
hose is a good time to include these inspections. Some of the items the
inspection should look are:
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Waterway clear, no obstructions.
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Threads not damaged.
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Swivel rotates freely, bearing plug and bearings in place.
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No excess corrosion.
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Gaskets in place and in good condition.
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Clamp bolts on LDH coupling collars in place and tight.
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Storz head lock levers, if so equipped, in place and operating freely.
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Hose not slipping out of the coupling.
In the case of connections of components made of dissimiliar metals, for
instance brass and aluminum, the standard recommends that they be disconnected
and inspected quarterly for corrosion. If the inspection reveals problems, the
item should be fixed immediately, taken out of service and fixed, or replaced
as necessary.
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