I'm aware BSPP is a parallel thread and so won’t taper out as an BSPT or NPT would, but how many threads must be allowed for engagement for a proper connection? ISO 228-1:2003 doesn’t give this information that I saw. Length of threaded distance equal to OD of the pipe? Any direction is appreciated!
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BSPP "Effective Thread" length? 1
- Thread starter Careful
- Start date
racookpe1978
Nuclear
What service conditions? What code are you working to?
What size pipe and what material and what wall thickness?
How will this be used?
What size pipe and what material and what wall thickness?
How will this be used?
- Thread starter
- #3
"What service conditions? What code are you working to?
What size pipe and what material and what wall thickness?
How will this be used? "
The connection will be offered for industrial service, so I don't know what the service conditions of the many customers will be, or what particular purposes they will use them for. I am looking to design for various pipe sizes from 1/4" to 1". The code is what I'm asking for.
If someone were asking what the effective length was for an NPT pipe thread would any of that make a difference? Isn't it more of: "It is what it is"?
What size pipe and what material and what wall thickness?
How will this be used? "
The connection will be offered for industrial service, so I don't know what the service conditions of the many customers will be, or what particular purposes they will use them for. I am looking to design for various pipe sizes from 1/4" to 1". The code is what I'm asking for.
If someone were asking what the effective length was for an NPT pipe thread would any of that make a difference? Isn't it more of: "It is what it is"?
racookpe1978
Nuclear
Well, not really.
A NPT is a wedged-in pipe joint designed to carry internal pressure and a nominal amount of bending and static weight by wedging the tapered threads from the "pipe" of some specific known size (1/4 dia through 4 inch diameter for example) and be strong enough to meet moderate internal pressures when sealed by pipe dope, pipe tape, or simple mechanical wedging. But regardless of pressure or the unknown sideways forces, the NPT connection cannot go any deeper (be engaged any deeper into the female threads) than about 1/2 inch. beyond that amount, the two tapered threads (female internal and male external) cannot go further.
So, mechanically, the NPT is stronger as the diamter goes up by the sq of the diameter, but its length is fixed by the thread engagement.
A straight thread cannot carry any internal pressure, but can go as deep into the opening as the designer wants. But it must either seal against a gasket at the bottom, or some mating machined flat or conic surfaces that themselves either seal the joint enough not to leak, or seal between the two joints and a flexible gasket that seals.
You, as designer, decide how deep the straight threads go and the diameter of teh joint. But then again, you (as designer) have to create the seal by some design and part decision.
Be aware that NPT threads are the accepted method for pressure threaded joints, and that straight threads for random commercially-sold parts will need to be tapped by the manufacturer. Water-tight hose-type threads - if your pressure is that low - are commercially/industrially "standard" and could be used. But you need to accept that kind of gasket and low pressure.
Hence my question: What do you need to seal against and what kind of sideways mechanical pressures do you need to resist?
A NPT is a wedged-in pipe joint designed to carry internal pressure and a nominal amount of bending and static weight by wedging the tapered threads from the "pipe" of some specific known size (1/4 dia through 4 inch diameter for example) and be strong enough to meet moderate internal pressures when sealed by pipe dope, pipe tape, or simple mechanical wedging. But regardless of pressure or the unknown sideways forces, the NPT connection cannot go any deeper (be engaged any deeper into the female threads) than about 1/2 inch. beyond that amount, the two tapered threads (female internal and male external) cannot go further.
So, mechanically, the NPT is stronger as the diamter goes up by the sq of the diameter, but its length is fixed by the thread engagement.
A straight thread cannot carry any internal pressure, but can go as deep into the opening as the designer wants. But it must either seal against a gasket at the bottom, or some mating machined flat or conic surfaces that themselves either seal the joint enough not to leak, or seal between the two joints and a flexible gasket that seals.
You, as designer, decide how deep the straight threads go and the diameter of teh joint. But then again, you (as designer) have to create the seal by some design and part decision.
Be aware that NPT threads are the accepted method for pressure threaded joints, and that straight threads for random commercially-sold parts will need to be tapped by the manufacturer. Water-tight hose-type threads - if your pressure is that low - are commercially/industrially "standard" and could be used. But you need to accept that kind of gasket and low pressure.
Hence my question: What do you need to seal against and what kind of sideways mechanical pressures do you need to resist?
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1
- Thread starter
- #5
For future readers: The information can be found in standard BS 5200:1997.
Also worth knowing: If your BS 5200 male fitting is firmly seated in the receiving female fitting, but still still leaking, it's possible the female fitting is a JIS B8363 as they use the same thread, but the male JIS fitting has a longer threaded portion.
Also worth knowing: If your BS 5200 male fitting is firmly seated in the receiving female fitting, but still still leaking, it's possible the female fitting is a JIS B8363 as they use the same thread, but the male JIS fitting has a longer threaded portion.
Straight threads only provide a mechanical junction. They don't really seal.
A seal is not achieved by the threads and another means of sealing must be introduced (ie. Gasket or O-Ring). Both the male and female threads are parallel, the female having a positive tolerance and the male having a negative tolerance on the basic diameters, thus producing clearance between the two. This combination of threads is used extensively in the hydraulics industry and with the correct selection of an appropriate seal material or seal form for the application, high pressures can be maintained.
The threaded fitting should be fully inserted and bottom out against the gasket or 0-ring.
A seal is not achieved by the threads and another means of sealing must be introduced (ie. Gasket or O-Ring). Both the male and female threads are parallel, the female having a positive tolerance and the male having a negative tolerance on the basic diameters, thus producing clearance between the two. This combination of threads is used extensively in the hydraulics industry and with the correct selection of an appropriate seal material or seal form for the application, high pressures can be maintained.
The threaded fitting should be fully inserted and bottom out against the gasket or 0-ring.
- Thread starter
- #7
What aspect is extraneous and what part is not common information available in the public domain? If pipe threads were proprietary information like the Microsoft products, they would most likely sell for $100 per threaded connection.
ISO 228-1:2000 is the Code for parallel threads if that is what you are after, not standard BS 5200:1997.
BS 5200:1997 is a specification for dimensions of hydraulic connectors and adaptors. If someone were asking what is the effective length was for parallel pipe threads, why would anyone respond with a specification for dimensions of hydraulic connectors and adaptors? You would have to be able to do mind reading, no?
The answer for connector applications is that the threaded fitting should be fully inserted and bottomed out against the sealing gasket or sealing 0-ring. The connectors are fabricated to fit together in this fashion, otherwise they will leak.
If your application involves a connection where mechanical strength is required such as a handrail application, then a fastening rule of thumb states that the maximum thread engagement length should be 1.5D, where D is the major diameter. The thread engagement length will prevent the fastener being pulled out due to thread stripping.
Information regarding misthreaded JIS B8363 would seem to be an example of extraneous content.
ISO 228-1:2000 is the Code for parallel threads if that is what you are after, not standard BS 5200:1997.
BS 5200:1997 is a specification for dimensions of hydraulic connectors and adaptors. If someone were asking what is the effective length was for parallel pipe threads, why would anyone respond with a specification for dimensions of hydraulic connectors and adaptors? You would have to be able to do mind reading, no?
The answer for connector applications is that the threaded fitting should be fully inserted and bottomed out against the sealing gasket or sealing 0-ring. The connectors are fabricated to fit together in this fashion, otherwise they will leak.
If your application involves a connection where mechanical strength is required such as a handrail application, then a fastening rule of thumb states that the maximum thread engagement length should be 1.5D, where D is the major diameter. The thread engagement length will prevent the fastener being pulled out due to thread stripping.
Information regarding misthreaded JIS B8363 would seem to be an example of extraneous content.
racookpe1978
Nuclear
I thought about that 1.5 OD rule of thumb, but assumed it was only valid for a solid threaded rod like a bolt or stud.
Seems like a 2 inch (nominal diameter) pipe with hollow walls and a very large OD to thread engagement ratio (thread engagement 3/8 to 1/2 maximum) could not follow that "stiffness" thumb rule.
Seems like a 2 inch (nominal diameter) pipe with hollow walls and a very large OD to thread engagement ratio (thread engagement 3/8 to 1/2 maximum) could not follow that "stiffness" thumb rule.
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