Hi, I am Angela, and this is another episode of Heads Up for Hosers.
In this video we will going across the pond to jolly old England
and discuss British Standard Pipe Fittings.
Today, we are going to talk about one of the British Pipe threads, BSPT commonly referred
to as British Standard Pipe Tapered thread.
British Pipe Threads are based on something called the Whitworth Thread.
This thread has been the standardized thread in Britain since 1841.
BSPT creates a seal by a wedging action.
It is a tapered thread as seen here.
This is different than most fittings that we have seen in Heads Up for Hosers videos
where the threads are parallel threads and seal differently
like on a metal to metal seal or an o-ring.
Because of this wedge design, these fittings were never intended to be a connection that
would be taken apart on a regular basis.
Each time the connection is put back together the wedge must be driven deeper to create a seal.
Soon there is no wedge left due to wear.
Although British Threads are a European Thread they are commonly mistaken for metric threads.
They are not metric threads because they are still measured using imperial units.
So, we take our fitting.
We see that this is a tapered thread.
This means that it could be only one of two things.
BSPT or NPTF.
We also see that there is a chamfer at the end of the fitting.
Not all BSPT fittings are going to have this, but keep in mind that it might be present.
Here we see the same fitting with and without the chamfer.
The chamfer is needed when mating BSPT with BSPP or British Standard Pipe Parallel.
Which we will go into more detail in another episode of Heads Up For Hosers.
BSPT threads come in a wide range of sizes, here at Gregg's we are more accustomed to
dealing with DASH two to DASH forty-eight.
What the heck is dash size?
Well, a dash size is the determination of sizes for hose, tubes, and fitting measurements.
This is measured in one sixteen-inch segments.
In this video series we will deal mostly with hose and fittings, but note that for tubing
the dash size calculation is slightly different.
Now here are a couple of hose examples: So, when dealing with most types of hose,
dash four equals four one sixteenth inch segments, which equals four sixteenths, or equal to
one quarter inch hose ID.
Now, to measure pipe threads you need to have an understanding of nominal pipe size as well.
Nominal Pipe Size means that in this day and age, a 1-inch BSPT fitting may not measure
one inch anywhere on the fitting.
This is due to the inconsistency in early pipe manufacturing.
But it's a mouthful to call a 1 inch fitting a 1.30 or a one and five sixteenths inch fitting,
so instead we opt for its nominal size, or "in name only", for simplicity.
So, getting back to it, to measure BSPT male thread, start by measuring the OD,
or Outside Diameter, of the third thread from the end.
Here we see it is a one and five sixteenths.
The next step for measuring British Pipe threads is to subtract one quarter inch from your
OD measurement to get close to the nominal pipe size.
This does not get us exactly to our measurement but it is a good starting point.
For example: the male fitting we measured had an OD of one and five sixteenths.
Looking in your identification book, we can see that one and five sixteenths minus one
quarter comes close to one inch, which is the nominal pipe size for this fitting.
Based on this we see that this is a DASH 16 fitting.
To verify this, we need to confirm the nominal thread size.
Now, we will take out our thread pitch gauge, finding the number eleven.
Next, we will lay this on the threads of the fitting like so.
Here we see it is a nice fit, confirming that it is a one-inch fitting with eleven threads per inch.
This means this is a DASH 16 BSPT fitting.
Something to note for British Pipe Threads.
Frequently, the tread size is expressed as a fraction preceded by the letter "R" or "G".
The "R" represents a tapered thread and the "G" indicates a parallel thread.
For example, the nominal thread size of BSPT 3/8 - 19 may be expressed as R 3/8.
The Dash 16 fitting that we just measured, may be expressed at R 1.
A female BSPT fitting will be measured close to the same way as the male fitting, but it
differs in one way, where you take your initial measurement from.
The female fitting ID, or inside diameter, is measured from the largest thread,
which is located at the end of the fitting.
After collecting this measurement, the steps to determine the dash size of the fitting
are the same as it's male counterpart.
To start, you would determine the ID, or inside diameter, of your fitting,
here we see that its 31/32 of an inch.
Consult your book with your measurement and subtract one quarter inch to come close to
the nominal thread size.
Here we see that this is a dash 12 female fitting with a nominal thread size of 3/4 - 14.
To install a BSPT fitting you should lightly lubricate the threads with oil that will be in your system.
Once you have it hand tight you only need 1.5 complete turns to ensure it is fully tightened.
Any more than this and you will reduce the life of the fitting.
Because of the wedging action, it is difficult to orient on elbows being that you have to
tighten the fitting to a certain spec, and once completed the fitting might not be orientated
where you need it to be.
Also, because of its wedge design this seal was never intended to be a connection that
would be taken apart on a regular basis.
Each time the connection is put back together the wedge must be driven deeper to create
a seal and soon there is no wedge left due to wear.
Here at Gregg's, we recommend you do not reuse these fittings.
A common problem when identifying BSPT fittings is their relation to NPTF or
National Pipe Tapered Fuel threads.
Although we explained the difference when we discussed NPTF fittings in the previous
video, it is important to know their relation when attempting to identify BSPT fittings.
Because BSPT fittings share a lot of the same design characteristics to NPTF they can often
be mistaken for each other and, at certain sizes, even thread together fairly well.
Referring to these size charts we can see that when dealing with DASH 8 or DASH 12 fittings
these two share the same nominal pipe size and thread pitch,
making identifying them very difficult.
Truthfully the biggest difference is that Pipe thread has a 60º thread angle where
as BSPT has a 55º thread angle.
This means that even though they feel like they thread together well, the difference
in thread angle means that a true seal is never formed and there is a chance of leaking.
Because there is no discernible difference between these fittings it is recommend that
you question what equipment this fitting came off of.
Depending on the type of equipment and the country of origin of said equipment you can
have a sense of what type of fitting you are working with.
For example, if the equipment is from an American manufacturer your fittings will most likely
be a NPTF rather than a BSPT.
This is a rare circumstance that you will get to this point, but for a Dash 8 or a Dash
12 BSPT fitting it is important to note that this mix up could be a possibility.
To solve these short comings such as orientation, on the next episode of Heads Up for Hosers
we will discuss the BSPP thread.
On behalf of our employee investors, thank you for spending some quality time with us
Canadian hosers today, and we will see you on the next episode of Heads Up for Hosers.