اندازه اتصالات لوله برنجی توضیح داده شده است: موضوعات, ابعاد و راهنمای انتخاب

انتخاب اتصالات برنجی مناسب به سادگی تطبیق دو عدد نیست. یک اتصال مشخص شده است 1/2 اینچ does not necessarily have a 1/2-inch thread diameter, and a fitting with a similar measured diameter may still use a completely different thread standard.

درک کردن brass pipe fittings sizes, thread dimensions, nominal pipe size, and thread standards is essential when selecting brass elbows, سه راهی, کوپلینگ ها, آداپتورها, اتصالات شیلنگ, and other threaded fittings.

This guide explains the most common brass fitting sizes, موضوعات NPT و BSP, how to measure a brass fitting, and how to specify the correct size when ordering.

اتصالات لوله برنجی

What Does “اتصالات لوله برنجی Size” Actually Mean?

When suppliers or buyers refer to a brass fitting size, they are usually referring to the nominal connection size, not the actual physical diameter of the fitting.

Several different measurements may be involved:

Measurement	What It Means
اندازه اسمی	Standardized size designation, such as 1/2″ یا 1″
Pipe OD	Actual outside diameter of the pipe
Thread Major Diameter	Largest diameter across an external thread
Thread Minor Diameter	Smallest diameter of the thread profile
Thread Pitch	Distance between adjacent threads
TPI	نخ در هر اینچ
Fitting Body OD	Outside diameter of the fitting body

به عنوان مثال, الف 1/2″ NPT brass fitting has a nominal size of 1/2 اینچ, but its external thread major diameter is approximately 0.840 اینچ (21.34 میلی متر).

This is why simply measuring a fitting with a caliper is not enough to identify its size.

Nominal Size vs. Actual Diameter

The nominal size is a standardized designation used to describe the pipe or connection. It should not automatically be interpreted as the actual thread diameter or pipe outside diameter.

For accurate identification, check the following together:

• Nominal fitting size
• استاندارد نخ
• Male or female thread
• Thread major or internal diameter
• TPI or thread pitch
• نمایه موضوع

مهم است: The dimensions in the following tables are standard reference dimensions for thread identification. Actual product dimensions can vary according to the applicable standard, tolerance, fitting design, and manufacturer.

Nominal Size vs. Actual Diameter

اتصالات لوله برنجی Size Chart

The most common brass pipe fittings are available in sizes ranging from small plumbing connections to larger industrial piping systems.

The following table provides common reference sizes for BSP threads:

اندازه اسمی	BSP Thread Major Diameter	TPI
1/8″	9.728 میلی متر	28
1/4″	13.157 میلی متر	19
3/8″	16.662 میلی متر	19
1/2″	20.955 میلی متر	14
3/4″	26.441 میلی متر	14
1″	33.249 میلی متر	11
1-1/4″	41.910 میلی متر	11
1-1/2″	47.803 میلی متر	11
2″	59.614 میلی متر	11

These dimensions refer to the نخ, not the overall outside diameter of the brass fitting.

به عنوان مثال, یک 1/2″ BSP threaded fitting has a thread major diameter of about 20.955 میلی متر. The body of the elbow, سه راهی, or coupling will normally be larger.

Common Brass Fitting Sizes

For plumbing, تهویه مطبوع, آب, گاز, and general industrial applications, commonly requested brass fitting sizes include:

• 1/8″
• 1/4″
• 3/8″
• 1/2″
• 3/4″
• 1″
• 1-1/4″
• 1-1/2″
• 2″

Smaller sizes are common in instrumentation, small water lines, and hose connections, while larger sizes are frequently used in industrial and commercial piping.

1/2″ اتصالات برنجی

NPT Brass Fitting Sizes

NPT (مخروطی لوله ملی) is one of the most widely used inch-based pipe thread standards, particularly in North America.

NPT threads are tapered and use a 60-degree thread form. The thread dimensions are standardized under ASME B1.20.1.

A typical NPT brass fitting size chart is:

Nominal NPT Size	تقریبا. External Thread Diameter	TPI
1/8″	0.405″ (10.29 میلی متر)	27
1/4″	0.540″ (13.72 میلی متر)	18
3/8″	0.675″ (17.15 میلی متر)	18
1/2″	0.840″ (21.34 میلی متر)	14
3/4″	1.050″ (26.67 میلی متر)	14
1″	1.315″ (33.40 میلی متر)	11.5
1-1/4″	1.660″ (42.16 میلی متر)	11.5
1-1/2″	1.900″ (48.26 میلی متر)	11.5
2″	2.375″ (60.33 میلی متر)	11.5

These are thread reference dimensions, not the overall dimensions of the fitting.

به عنوان مثال, if you measure approximately 21.3 mm across the external thread of a fitting, it may be a 1/2″ NPT thread. با این حال, diameter alone does not prove that identification. TPI and thread profile should also be checked.

Why NPT Size Can Be Confusing

A common mistake is assuming:

1/2″ NPT = 1/2″ thread diameter

It does not.

1/2″ designation refers to the nominal pipe size, while the external thread diameter is approximately 0.840 اینچ.

This difference is normal for pipe thread sizing and is one of the main reasons buyers should specify the complete thread standard when ordering brass fittings.

NPT Brass Fitting Sizes

BSP Brass Fitting Sizes

BSPP (موازی) and BSPT (مخروطی)

BSP—British Standard Pipe—is the dominant thread family in the UK, اروپا, and many Commonwealth markets. Unlike NPT, BSP comes in two distinct forms:

BSPP (G thread, ISO 228-1): Parallel threads. They do not seal on the threads themselves. A separate sealing surface—usually a bonded washer, O-ring, or gasket—provides the seal.

BSPT (R/Rp thread, ISO 7-1): Tapered threads. Like NPT, BSPT seals by thread compression. با این حال, the thread angle is 55 درجه (Whitworth form), not 60 درجه.

Common BSP Sizes

BSP Size	تقریبا. Major OD	TPI
1/8″	9.728 میلی متر	28
1/4″	13.157 میلی متر	19
3/8″	16.662 میلی متر	19
1/2″	20.955 میلی متر	14
3/4″	26.441 میلی متر	14
1″	33.249 میلی متر	11
1-1/4″	41.910 میلی متر	11
1-1/2″	47.803 میلی متر	11
2″	59.614 میلی متر	11

Thread dimensions per ISO 228-1 (BSPP) و ISO 7-1 (BSPT). زاویه نخ: 55درجه (Whitworth form). BSPP is parallel; BSPT is tapered at 1:16.

A common field observation: A thread measuring roughly 1/2 اینچ (12.7 میلی متر) across the outside is likely a1/4″ BSP thread, not a 1/2″ BSP. 1/2″ BSP thread actually measures20.955 میلی متر across its major diameter. This “quarter-inch larger” rule of thumb holds approximately for BSP sizes up to about 1″, but always verify with a thread gauge rather than relying on visual estimation alone.

BSP Brass Fitting Sizes

NPT در مقابل BSP: Why the Same Size May Not Fit

This is not a deep comparison—there is a dedicated article coming on that topic. But you need to know the essentials:

ویژگی	NPT	BSP
Primary Market	آمریکای شمالی	انگلستان, اروپا, Commonwealth
Thread Angle	60درجه	55درجه
Common Types	NPT (مخروطی)	BSPP (parallel), BSPT (مخروطی)
Seal Method	Thread compression + درزگیر	BSPP: gasket/washer; BSPT: thread compression
قابل تعویض?	خیر	خیر

Never specify a brass fitting only as “1/2 inch.” Always confirm the thread standard.

Even when nominal sizes match—for example, both are labeled 1/2″—NPT (60° زاویه نخ) and BSP (55° Whitworth) will not thread together properly. The 5° angle difference causes cross-threading and guarantees leaks. Forcing them together damages both threads.

How to Measure a Brass Pipe Fitting

When you have an unmarked fitting in hand, five measurements will identify it:

مرحله 1: Check the Fitting Type

آرنج, سه راهی, جفت شدن, آداپتور, or connector? The type tells you what the fitting does, but not its size.

مرحله 2: Measure the Thread Diameter

Use a vernier caliper. For male threads, measure across the outside diameter at the widest point. For female threads, measure the inside diameter.

مرحله 3: Count the Threads (TPI)

Use a thread pitch gauge or place a ruler along the thread and count how many complete threads fit within one inch. This is the TPI.

مرحله 4: Identify the Thread Profile

مخروطی یا موازی? NPT and BSPT taper; BSPP and metric threads are parallel. Roll the fitting on a flat surface—a tapered thread will wobble visibly.

مرحله 5: Check Male or Female

تایپ کنید	توضیحات
Male	نخ خارجی
Female	نخ داخلی
Male × Male	External threads on both ends
Female × Female	Internal threads on both ends
Male × Female	Mixed thread ends

A thread identification kit containing pitch gauges, a caliper, and reference profiles is worth the investment if you regularly handle mixed-standard fittings.

Measure a Brass Pipe Fitting

How to Choose the Right Brass Fitting Size

Once you understand what the size number actually means, selection becomes systematic. Run through these seven checks before placing an order:

بررسی کنید	Question to Ask
اندازه لوله	What is the pipe nominal size?
Thread Standard	NPT, BSPP, BSPT, یا متریک?
اتصال	نر یا ماده?
فشار	What working pressure is required?
دما	What operating temperature?
برنامه	آب, تهویه مطبوع, گاز, or industrial fluid?
مواد	What brass grade is required?

Common brass grades for fittings include CW617N (CuZn40Pb2) for general-purpose plumbing and CW602N (CuZn36Pb2As) for dezincification-resistant applications in aggressive water conditions.

Brass Fittings in industrial applications

Common Mistakes When Choosing Brass Fitting Sizes

اشتباه 1: Treating Nominal Size as Actual Diameter

یک 1/2″ fitting does not necessarily have a 1/2-inch thread diameter.

اشتباه 2: Measuring Only the Fitting Body

The body diameter does not identify the thread size.

اشتباه 3: Ignoring NPT vs. BSP

A similar diameter does not mean the threads are compatible.

اشتباه 4: Confusing BSPP and BSPT

Both belong to the BSP family, but one is parallel and the other is tapered.

اشتباه 5: Ignoring Male/Female Configuration

A correct thread size is not enough if the connection gender is wrong.

اشتباه 6: Selecting by Diameter Without Checking TPI

Two threads can have similar diameters but different pitches or TPI.

اتصالات برنجی Size vs Pipe Size: Are They the Same?

No—and this is where the confusion peaks.

مشخصات	Refers To
Fitting nominal size	Standard connection size label
Pipe OD	Outside diameter of the pipe
Pipe ID	Inside diameter of the pipe
Thread OD	Actual measured thread diameter

A fitting marked 1/2″ does not have a 12.7 mm thread OD. In NPT, the 1/2″ size has a 0.840″ thread OD. In BSP, the 1/2″ size has a 20.955 mm major diameter. The nominal size is a matching reference, not a physical dimension.

Brass Fitting Size vs Pipe Size

Need اتصالات لوله برنجی for Your Project?

Need brass pipe fittings in specific sizes, استانداردهای نخ, or connection types? Share your required fitting type, nominal size, thread standard, مواد, and application with our team. شرکت فناوری انرژی Luoyang Datang, Ltd will confirm the appropriate specification and provide a quote.

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