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| Pipe
Fitting Thread Standards |
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CAUTION
- Always wear eye protection when working with Pneumatic
or Hydraulic systems
Never force compressed air into your skin - this can be
fatal!
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This
section is intended as a guide to choosing the correct pipe
fittings for your Pneumatic or Hydraulic system.
Although all the information here is intended for low
pressure systems ( max 10 bar ) the principles
are the same for high pressure systems with the exception
of the Push-Fit fitting range which is low pressure
only
The
most confusing aspect of pipe fittings for a beginner is
the number of different types and threads all with different
intended uses.
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There
are also differences of thread between the USA and
Europe, a thread designed for a particular task in
Europe will have an equivalent in the USA.
This should only be a problem where cross-Atlantic equipment
needs to be fitted.
In the UK the British Standard Pipe threads (BSP) are the
most common. Whereas in the USA the National Pipe Thread (NPT)
standard is used. The two standards are similar but not compatable.
Metric threads are also found but are not extensive yet. |
| Rough
Guide to Fitting Types |
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We have
simplified the choice of fittings to the following :-
a)
For plastic tubing - Plastic Push Fit Fittings - available
in sizes - 4mm, 6mm, 8mm, 12mm.- These have stainless
steel gripping elements
b) For interfacing to Active elements and manifolds
eg. compressors, valves, filters etc.etc. - BSP the
Parallel thread - BSPT the tapered thread
Push-Fit Fittings
The basic principle of operation of the Push-Fit type fitting
is shown in the illustration on the right. For these only
the tubing size and fitting function need be known.
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Threaded
Fittings
The
two main thread types are shown on the left - we have kept
this intentionally simple avoiding thread angle data etc.
as it is not necessary at this point. The pipe diameters
are imperial in inches ie. 1/8, 1/4,3/8, 1/2 etc
BSP
- The parellel thread type is also listed as BSPP
and G
BSPT
- is the tapered thread as shown left - the taper is exagerated
- the taper and parallel threads will mate roughly together
but no seal will be made and it is mechanically unsafe
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Sealing
Methods for the two types of Thread
Parallel
threads
(BSP - BSPP - G) are fluid sealed using a Bonded
Seal washer or a deformable Copper Washer
- Bonded seals are reusable to a greater extent than the
copper washer - Copper washers are not needed on low pressure
low temperature systems
Tapered
threads (BSPT)are sealed using PTFE pipe sealing
tape which is not reusable
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