"B" nut
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"B" nut
Just curious, how did the term "B" nut in pipelines came about? Why "B"?
Other terms I can understand, like "E"-seal (since the seal has an "E" shape) or "P" seal (seal has a "P" shape), but "B" nut???
Other terms I can understand, like "E"-seal (since the seal has an "E" shape) or "P" seal (seal has a "P" shape), but "B" nut???
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I’m sure many of you have heard, and maybe used, the term “B Nut” when referring to an AN818 fitting. The question of why it’s called a “B Nut” might have even crossed your mind. Well, here’s the story.
The term “B Nut” goes back to the early days of standardiza- tion of aviation hardware for the military. For tubing and plumbing, the terminology that was adopted came from the leading supplier of aviation products at the time, the Parker Appliance Company. Parker published a book called “Maintenance of Aircraft Tubing Systems”. I’m not sure when the first edition of this book was published, but I am aware of a “second edition” that was published in 1939, and the copy we have in the EAA library was published in 1943.
There is a section of this book titled “Flared Tubing Fit- tings”. It is in this section that references to a “B Nut” are found. It is interesting to note that the AN818 coupling fit- ting commonly referred to these days as a “B Nut” is not actually a “B Nut”. It is actually a “BT Nut”. The AN819 sleeve that is used with the AN818 coupling is a “T Sleeve”.
There is a “B Nut” mentioned in the book, and it is also used for flared fittings. However, the “B Nut” is a male thread nut that is made to be used in a matching female thread re- ceptacle. This combination was called the “AC810 series fitting” and to my knowledge was not included when the move was made to the “AN” series fittings that we know today. The “BT Nut” and “T Sleeve” that became the AN818 and AN819 fittings we use today were referred to as the AC811 series in the Parker book. In the 1943 edition of the book, the AC810 series (including the “B Nut”) is re- ferred to as “obsolete”.
Whether you call it a “B Nut” or an AN818 fitting, you need to make sure to use the proper torque when tightening it. Use this table as a guide and pass this info along to builders when you make your Technical Counselor visits. Info on proper tightening torque may also be found in AC 43.13 and in the Standard Aircraft Handbook.
The term “B Nut” goes back to the early days of standardiza- tion of aviation hardware for the military. For tubing and plumbing, the terminology that was adopted came from the leading supplier of aviation products at the time, the Parker Appliance Company. Parker published a book called “Maintenance of Aircraft Tubing Systems”. I’m not sure when the first edition of this book was published, but I am aware of a “second edition” that was published in 1939, and the copy we have in the EAA library was published in 1943.
There is a section of this book titled “Flared Tubing Fit- tings”. It is in this section that references to a “B Nut” are found. It is interesting to note that the AN818 coupling fit- ting commonly referred to these days as a “B Nut” is not actually a “B Nut”. It is actually a “BT Nut”. The AN819 sleeve that is used with the AN818 coupling is a “T Sleeve”.
There is a “B Nut” mentioned in the book, and it is also used for flared fittings. However, the “B Nut” is a male thread nut that is made to be used in a matching female thread re- ceptacle. This combination was called the “AC810 series fitting” and to my knowledge was not included when the move was made to the “AN” series fittings that we know today. The “BT Nut” and “T Sleeve” that became the AN818 and AN819 fittings we use today were referred to as the AC811 series in the Parker book. In the 1943 edition of the book, the AC810 series (including the “B Nut”) is re- ferred to as “obsolete”.
Whether you call it a “B Nut” or an AN818 fitting, you need to make sure to use the proper torque when tightening it. Use this table as a guide and pass this info along to builders when you make your Technical Counselor visits. Info on proper tightening torque may also be found in AC 43.13 and in the Standard Aircraft Handbook.
http://www.eaa.ca/safetywire/mar09.pdf
