FAQs

Threaded pipe fittings for use in installations for the delivery of air, gases or fluids under pressure have a threaded section that is slightly conical (in contrast to the cylindrical section commonly found on bolts and leadscrews). This is called a "tapered thread". The seal attained within a threaded pipe joint depends upon the seal created by the deformation of the threads when they are tightened to the proper torque and, in almost all applications, the use of a sealing coating such as thread seal tape ("Teflon tape"), a liquid or paste pipe sealant such as pipe dope, or pre-applied sealant. Tapered thread joints typically do not include a gasket.

"Visual" of a Tapered Thread pipe plug; note that the threaded portion is tapered and so touches the calipers at only two points. Photo by Ben Frantz Dale

"NPT" (National Pipe Thread/Tapered) designates the thread form often used for standard commercial "U.S. inch" pipe and pipe fittings. The NPT thread form is designed for flank-to-flank interference fit and requires use of some type of sealing material applied to the threads to achieve adequate seal.

"NPTF" (National Pipe Thread Fuel-Tapered) designates the thread form most commonly found on "U.S. inch" pipe plugs. The NPTF thread form is designed for crest-to-root contact. These "crush" immediately prior to the mating thread flanks making contact, to achieve maximum metal to metal interference fit. NPTF threads offer the best potential for leak-free taper thread assemblies. Pre-applied sealant or adhesive should be used to compensate for any variations in the condition of the mating threads and the assembly process.

"3/4" Taper" describes the diametrical taper of 3/4" per 12" of length of standard tapered pipe plug threads.

3/4 Taper is applicable to SAE, ASME/ANSI, DIN, British, and Japanese Standard tapered pipe plug threads.

"7/8 Taper" describes the diametrical taper of 7/8" per 12" of length of tapered flush seal PTF - 7/8 pipe plug threads.

To correctly gauge a 3/4 taper thread pipe plug, two gages are required: an L1 Gage,which verifies the "bottom" size/threads; and an L2 Gage, which verifies the top size/threads.

To correctly gauge a 7/8 taper thread pipe plug, two gages are required: an F2 Gage,which verifies the "bottom" size/threads; and an F1 Gage, which verifies the top size/threads.

No. Use of "NPT" gages to gauge "NPTF" (Seaway) pipe plugs may erroneously indicate an out-of-spec part.

Tapered pipe plugs are "sized" relative to the pipe or pipe fitting with which they are assembled; therefore, an "inch" pipe plug measures larger than the designated size. Often these pipe plug sizes are identified as "IPS" (Iron Pipe Size).

A Short Standard pipe plug is one thread pitch shorter than a Long Standard pipe plug, and the one thread is always removed from the bottom of the plug.

• Pallet and cartons are sized to maximize use of transit cube and warehouse storage space while maintaining manageable gross weights per carton and per full pallet.
• Cartons are packed “full” (no head space) to minimize transit damage caused by handling and stacking/crushing. Seaway's custom size bulk pack carton (7" x 7" x 5.25") assures that no full carton exceeds 40 lbs.
• Half pallets are used when appropriate to minimize the environmental impact of the disposal of packaging material. Half pallets also help to maximize transit cube space and warehouse storage space.