Change is in the Air...

Great things are happening at PipeandHose.com !

We are in the middle of a major revamp of our site, which will be a big improvement. We are adding new content, new information, and a new indexing scheme, making it easier to find the information you need. This new site should roll out by the end of October, November, December (no, seriousely, we really mean it this time!) so keep watching.

We want to shout a big thanks to all who have enjoyed our site in the past...

Thank You!

-The Pipe and Hose Team

...about pipeandhose.com

Welcome to pipeandhose.com

With so many different standard fitting types, how do you know which replacement fitting to buy?  How can you know that what you buy will actually screw onto the business end of what you've got in your hand?  Will the threads match?  Or  will it start, and act like it is going to work, but then bind up a turn and a quarter in?

  • Are you frustrated with the lack of information available from your traditional vendors? 
  • Do they speak authoritatively, yet seem to display a lack of knowledge of "what's really out there"?
  • Are you tired of being told, "Yes, this is a standard hose thread," when you know darn well that there are numerable standards in the field?

Well, pipeandhose.com is here for you.

Here you will find answers, answers, answers.  We will be continually building this site with the aim of becoming the world authority on pipe, hose, and tubing.  Though we are only beginning now, we hope you will leave here with more information than when you arrived.  Please use this site as your ready reference, and check back often to see our progress.  Thanks.

-The pipeandhose team.

American National Pipe - NPT/NPS

American National pipe (NPT, NPS), Like British Standard Pipe (BSP), is designated by trade size, rather than actual diameter, as shown in the table below.

There are two basic types of National pipe threads:

  • NPT: National Pipe Taper
  • NPS: National Pipe Straight

NPT threads are also sometimes referred to as

  • MIP (Male Iron Pipe)
  • FIP (Female Iron Pipe)
  • IPT (Iron Pipe Thread)
  • FPT (Female Pipe Thread)
  • MPT (Male Pipe Thread)

Note that these references are somewhat casual, and might possibly be used in reference to NPS instead of NPT.

Both NPT and NPS have the same thread angle, shape, and pitch (threads per inch).  However, NPT threads are tapered and NPS threads are straight (parallel).  Both threads have a 60° included angle and have flat peaks and valleys (this is a Sellers thread form).

If you've worked with pipe much at all, you've probably noticed that the size of the pipe isn't really what size the pipe is.  Unlike tubing, which is generally specified by its OD, or hose, which is generally specified by its ID, pipe is specified by something else... its Trade Size.  So when you say "3/4 pipe," you're actually saying "pipe whose OD is a little more than an inch, and whose ID is about 53/64."  -that is, if you are talking about schedule 40 pipe, which is generally what is used for most plumbing applications.

Pipe dimensions are specified by trade size and schedule, according to the following table.  Note that while British Standard Pipe dimensions are similar, they are not equivalent to the American Standard Pipe Sizes.  See NPT vs. BSP Pipe for thread comparisons.

British Standard Pipe - BSP

BSP: British Standard Pipe

BSP pipe, Like American National pipe (NPT, NPSM), is designated by trade size, rather than actual diameter, which is approximately equal to the thread's Major Diameter in the table below.

There are two types of BSP threads:

  • BSPT: British Standard Pipe Taper -also known as "R" or "Rc" threads
  • BSPP: British Standard Pipe Parallel -also known as "G" or "Rp" threads

Both styles have the same thread angle, shape, and pitch (threads per inch).  However, BSPT threads are tapered and BSPP threads are straight (parallel).  BSP threads have a 55° included angle and have rounded peaks and valleys (this is a Whitworth thread form).

Here are the actual thread dimension data for BSPP and BSPT threads.  The major diameter is a bit larger smaller than the actual OD of the pipe, and the minor diameter should be very close to what you would measure inside the female threaded end of a fitting.  Note that the Gage Length dimension pertains only to the BSPT (tapered) thread. 

NPTR -National Pipe Taper Railing

NPTR - National Pipe Taper Railing

Flare Fittings

The following flare fittings are similar, but not equivalent:

  • AC (Air Corp Standard) also called Parker Triple Fitting (NOT Triple-Lok)
  • AN (Air Force - Navy Aeronautical Standard)
  • AND (Air Force - Navy Aeronautical Design Standard)
  • AS (Aerospace Standard)
  • MS (Military Standard)
  • JIC (Joint Industry Council)
  • SAE 37° also called Parker Triple-Lok
  • ISO 8434 (1986), ISO 8434-2 (1996)
  • SAE 45°

AC (Air Corp)

The AC flare fittings were developed for the aviation industry in the 1930s, and have long since been superceded by AN.  Today, it is rare that you will come across one of these fittings.  AC fittings use a 30° flare angle, and they are most readily recognizable by a very short or non-existent straight section between the top of the thread (on the male fitting) and the major diameter of the flare.  Most flare fittings of the other types have a non-threaded section at the base of the flare.

Note that the AC were talking about here has nothing to do with air conditioning.  It is possible that some people may use the term "AC Flare" to refer to the SAE 45° fittings discussed below.

AN, AND, MS, AS

AN / AND fittings have a 37° flare angle and use a class 3A/3B thread, which is a close tolerance, radiused root thread.  These fittings have traditionally been available in aluminum, carbon steel, stainless steel, and titanium.

AN / AND fittings remain in prevalent use today, and they may alternatively be designated with an MS number, which are generally directly cross-referenced replacement fittings (functionally equivalent).  For instance, an AN815 is equivalent to an MS24392.  MS, however, is a very broad standard covering all kinds of hardware, and is not limited to AN fluid couplings.

The AN and MS designations for many fittings are being superceded with AS (Aerospace Standard).

In general, there appears to be a trend away from flared tubing in favor of compression type fittings, probably due to the fact that flares require greater special attention to craftsmanship (and more time) in assembly

JIC, SAE 37°, ISO 8434, Parker Triple-Lok

When someone says it's a JIC fitting, this is generally what they are talking about.  This fitting is the general industrial adaptation of the AN fitting.  These fittings have a 37° flare angle and use a class 2A/2B thread, which is a standard tolerance industrial thread with normal trapezoidal root truncation.  These fittings have traditionally been available in carbon steel, stainless steel, and brass. Some of these fittings may conform to MIL-F-18866 and/or SAE-J514.

SAE 45°

The SAE 45° fitting is typically used for low pressure applications, usually with soft copper or soft aluminum tubing, which flares easily to the 45° angle.  These fittings are easily recognized by placing them on a square, or by placing two males flare-against-flare at right angles, and observing the 90 degree included flare angle,  The 45° flare fitting is the one you are most likely to run across at your local hardware store.  They are commonly found in use in the following applications:

  • refrigerant lines
  • fuel lines
  • natural gas appliance hookups
  • ice maker connections
  • domestic water systems in motor homes

JIC 37° / SAE 45° Dual Angle Seat

There are some fittings made which can be screwed onto either a 37° or a 45° fitting.  The dual angle flare seat is apparent.  Obviously, this is a kind of bastard fitting, and should not be selected as a primary style in the design of any hydraulic system, though they surely come in handy at times.

Federal Specification WW-C-621G

WW-C-621G
February 7, 1990
SUPERSEDING
WW-C-621F
April 4, 1983

FEDERAL SPECIFICATION

COUPLING ASSEMBLY, HOSE (FIRE, WOVEN-JACKETED,

RUBBER- OR FABRIC-LINED AND UNLINED)

Fire Hydrant Standards

There are several different fire hose coupling standards in use in the U.S. today.  The trend toward national standardization has been very slow and long in coming.  The first real effort in national standardization commenced in the wake of the Great Baltimore Fire of 1904 over one hundred years ago, and it is still far from complete.  Many cities and municipalities continue to use their own standard couplings, and some may have different standards from one neighborhood to another.  Most couplings in use today are NST standard, with several notable variants, New york City, and Chicago, in particular.  See this interesting article for details.

Here is a partial list of some cities and the dimensions of their Fire Hydrant Fittings.  The National Standard (NS) Hydrant has two carry hose male fittings of 2.5 inch NST/NH and one pumper fitting of 4.5 inch NST/NH.  It should be noted that some of the hydrant fittings below, that are not NS compliant, might very well be an NST/NH fitting of a different nominal diameter, although some clearly are not, since their diameter and pitch do not match an NST/NH spec.  Furthermore, since these diameters are nominal values relating to a given hose size, and not the actual thread diameter, they cannot be used to assure NST/NH compatability without more precise dimensional information, e.g. pitch diameter.

 

Fire Hydrant Connections

  Carry Hose Pumper Hose
City Nom. Dia Thds/Inch Nom. Dia Thds/Inch
         
NS - National Standard (follows NST -also NH) 2.5 7.5 4.5 4
         
Austin, TX NS 4 6
Charlotte, NC NS 4 6
Chicago, IL     4.5 6
Cleveland, OH 2.5 8 4.25 6
Colorado Springs, CO NS 4.5 6
Columbus, OH - - 4 6
Dallas. TX NS 4 4
Denver, CO NS 4.5 6
El Paso, TX NS 4 6
Fort Worth, TX NS 4 4
Indianapolis, IN NS    
Kansas City, MO NS 4 4
Las Vegas, NV NS 4 4
Los Angeles, CA NS 4 4
Memphis, TN NS 4 7
Miami, FL NS 4 7
New Orleans, LA 2.5 6 NS
New york City, NY 2.375 8 NS
Oklahoma City, OK 2.5 6 NS
Phoenix, AZ 2.5 6 4 6
San Antonio, TX NS 4 4
San Diego, CA NS 4 4
San Fransisco, CA 3, 3.5 3 3, 3.5 3
San Jose, CA NS 4 4
Santa Ana, CA NS 4 4
Seattle,WA NS 4 6
Tulsa, OK NS 4 4
Washington, DC NS 4 4
Wichita, KS NS 4 4

AS568B O-Ring Data

Click this title (just above this text) and then follow the index links below or to the right for more dimensional data on the various o-ring series.

What I've shown here are some generally useable groove design data, but if you really want the whole story of oring seal design, this Parker handbook is the real authority.  Serious readers only.

The following tables give the gland dimensions for static and dynamic (reciprocating) applications.

Static O-Ring Axial (Face Seal) Glands
AS568B Cross Gland Squeeze Groove Width Groove
Section Depth Inches % Liquids Gases Radius
-004 thru -050 .070±.003 .050    .054 .013   .023 19     32 .101   .107 .084   .089 .005   .015
-102 thru -178 .103±.003 .074   .080 .020   .032 20     30 .136   .142 .120   .125 .005   .015
-201 thru -284 .139±.004 .101   .107 .028   .042 20     30 .177   .187 .158   .164 .010   .025
-309 thru -395 .210±.005 .152   .162 .043   .063 21     30 .270   .290 .239   .244 .020   .035
-425 thru -475 .275±.006 .201   .211 .058   .080 21     29 .342   .362 .309   .314 .020   .035

 

Static O-Ring Radial Glands
AS568B Cross Gland Squeeze Diametral Groove Width Groove
Section Depth Inches % Clearance 0 BR 1 BR 2 BR Radius
-004 thru -050 .070±.003 .050    .052 .015    .023 22    32 .002    .005 .093    .098 .138    .143 .205    .210 .005   .015
-102 thru -178 .103±.003 .081    .083 .017    .025 17    24 .002    .005 .140    .145 .171    .176 .238    .243 .005   .015
-201 thru -284 .139±.004 .111    .113 .022    .032 16    23 .003    .006 .187    .192 .208    .213 .275    .280 .010   .025
-309 thru -395 .210±.005 .170     .173 .032    .045 15    21 .003    .006 .281    .286 .311    .316 .410    .415 .020   .035
-425 thru -475 .275±.006 .226    .229 .040    .055 15    20 .004    .007 .375    .380 .408    .413 .538    .543 .020   .035

 

Dynamic O-Ring Reciprocating Glands
AS568B Cross Gland Squeeze Diametral Groove Width Groove
Section Depth Inches % Clearance 0 BR 1 BR 2 BR Radius
-004 thru -050 .070±.003 .055    .057 .010    .018 15    25 .002    .005 .093    .098 .138    .143 .205    .210 .005   .015
-102 thru -178 .103±.003 .088    .090 .010    .018 10    17 .002    .005 .140    .145 .171    .176 .238    .243 .005   .015
-201 thru -284 .139±.004 .121    .123 .012    .022 9      16 .003    .006 .187    .192 .208    .213 .275    .280 .010   .025
-309 thru -395 .210±.005 .185    .188 .017    .030 8       14 .003    .006 .281    .286 .311    .316 .410    .415 .020   .035
-425 thru -475 .275±.006 .237    .240 .029    .044 11    16 .004    .007 .375    .380 .408    .413 .538    .543 .020   .035

Comparison of hose stock types

 Comparison of hose stock types

Chemical name
Neoprene
Nitrile (Buna-N)
Butyl
Hypalon
EPDM
CPE
ASTM-SE designation
SC
SB
R
TB
R
None
SAE J14 & SAE J200
BC
BG
AA
CE
AA
None
Flame resistance
Very good
Poor
Poor
Good
Poor
Good
Petroleum base oils
Good
Excellent
Poor
Good
Poor
Very good
Diesel fuel
Good to excellent
Excellent
Poor
Poor
Poor
Very good
Resistance to gas permeation
Good
Good
Outstanding
Good to excellent
Fair to good
Good
Weather
Good to excellent
Poor
Excellent
Very good
Excellent
Good
Ozone
Good to excellent
Poor for tube
Good for cover
Excellent
Very good
Outstanding
Good
Heat
Good
Good
Excellent
Very good
Excellent
Excellent
Low temperature
Fair to good
Poor to fair
Very good
Poor
Good to excellent
Good
Water-oil emulsions
Excellent
Excellent
Good
Good
Poor
Excellent
Water-glycol emulsions
Excellent
Excellent
Excellent
Excellent
Excellent
Excellent
Diesters
Poor
Poor
Excellent
Fair
Excellent
Very good
Phosphate esters
Fair for cover
Poor
Good
Fair
Very good
Very good
Phosphate ester based emulsions
Fair for cover
Poor
Good
Fair
Very good
Very good
Syndicate content

 
Pipe Size
Pitch  (Threads/Inch)
NPT/NPS
BSP
 1/16"
27
---
 1/8"
27
28
 1/4"
18
19
 3/8"
18
19
 1/2"
14
14
 5/8"
---
14

 
Pipe Size
Pitch  (Threads/Inch)
NPT/NPS
BSP
 3/4"
14
14
1"
11 1/2
11
1 1/4"
11 1/2
11
1 1/2"
11 1/2
11
2"
11 1/2
11
2 1/2"
8
11

 
Pipe Size
Pitch  (Threads/Inch)
NPT/NPS
BSP
3"
8
11
3 1/2"
8
11
4"
8
11
5"
8
11
6"
8
11
8"
8
---