Malleable fittings Selection Guide

by | Sep 15, 2022 | Industry Knowledge, Service

What are the standards and technical parameters that need to be paid attention.

when selecting malleable pipe fittings—Take 4 way cross pipe fitting as an example.

As an indispensable industrial product in human modern life, malleable pipe fittings are already a highly standardized modern industrial product. These standards are summarized and perfected in people’s continuous engineering practice, and more and more standards have been determined to ensure and improve the independence (commercialization), compatibility, interoperability, repeatability safety and of quality malleable products.

A small pipe fitting can be accurately described by many standard parameters. Only when both buyers and sellers clearly and accurately understand the meaning of these standard parameters can they communicate efficiently and smoothly, so as to avoid ambiguity. Close deals quickly. Now let us take the 4 way cross pipe fitting of China Jianzhi brand as an example to explain some technical parameters and precautions about malleable pipe fittings. The following is a link to the website of this product, you can see some technical parameters on the page: 4 Way Pipe Fitting Equal Cross

National standard number of pipe fittings

National standard number of pipe fittings

The above table lists the standard numbers of pipe fitting products in major countries in the world. The national standards promulgated by each country specify the standards that related products should meet in detail. You can query the standards of pipe fitting products in related countries through the number.

This is also the fastest and most intuitive way to understand a country’s requirements for related industries. The national standard for malleable iron pipe fittings in China is GB/T3287-2011, and the material standard for malleable iron is GB/T9440-2010. Jianzhi Group is the main drafting unit of these two standards and plays a key role in the revision of the standards. Below we will explain some key values in conjunction with China’s national standards.

Relevant standards for malleable iron materials

Malleable cast iron is cast iron with a certain chemical composition into a white blank and then annealed. It has high strength, plasticity and impact toughness, and can partially replace carbon steel. The grade of malleable cast iron is indicated by the percentage of the minimum tensile strength value (MPa) and the minimum elongation after fracture, followed by “KTH” (the Chinese phonetic prefix of black-heart malleable iron) or “KTZ” (the Chinese phonetic prefix of pearlitic malleable iron).

For example, the grade KTH 350—10 represents a black-core malleable iron with a minimum tensile strength of 350 MPa and a minimum elongation after fracture of 10%, namely ferritic malleable cast iron; KTZ 650—02 represents a minimum tensile strength of 650 MPa and a minimum elongation after fracture of 650 MPa. Pearlitic malleable iron with a rate of 2%. The material used for the Jianzhi brand 4way cross pipe fitting in the picture below is the black-heart malleable cast iron with the grade of KTH 350-10.

Malleable pipe fittings with material number KTH350-10

Standards for threads

Threads are divided into two types: sealed and non-sealed. Different countries have different regulations for these two types of threads. However, the common threads mainly include the following: NPT, PT, G, etc.

  1. NPT is the abbreviation of National (American) Pipe Thread, which belongs to the American standard 60-degree tapered pipe thread, which is mostly used in North America.
  2. PT is the abbreviation of Pipe Thread, which is a 55-degree sealed conical pipe thread, which belongs to the Wyeth thread family, and is mostly used in Europe and the Commonwealth of Nations.
  3. G is a 55degree unsealed pipe thread, which belongs to the Whitworth thread family. Marked as G stands for cylindrical thread.

Moreover, there are three differences between the metric and Anglo-American thread representation methods:

  1. Metric threads are expressed by pitch, and American and British threads are expressed by the number of threads per inch.
  2. Metric threads are 60-degree equilateral threads, inch threads are isosceles 55-degree threads, and American threads are isosceles 60-degree threads.
  3. Use metric units (such as mm) for metric threads, and imperial units (such as inches) for American and British threads.

China used the metric thread standard for the malleable steel pipe fittings at the earliest stage, and gradually adopted the inch thread standard in the later development. Therefore, the national standard thread of Jianzhi can be used in common with the British standard thread.

It is worth noting that different countries also have different standards for the thread of malleable steel pipe fittings. This must be communicated well before the transaction. Thread selection is very important for the smooth installation of pipe fittings.

Precise thread

Description of Malleable Pipe Fittings

There are many values involved in the description of malleable iron pipe fittings, mainly including size, maximum working pressure, maximum working temperature, elongation and other values.

Taking Jianzhi brand 4way cross pipe fitting as an example, the following figure is the size comparison table:

It is worth noting that in and mm are not directly converted, and they need to be compared strictly according to the values in the above table.

Relevant technical parameters of 4way cross pipe fitting

As shown in the figure above, most of the values describing malleable pipe fittings can be easily known by their literal meaning. When you put your needs to the seller, you should pay attention to the following two points:

  1. Make it clear what your needs are. For malleable iron pipe fittings, what standard should the seller’s products meet?
  2. Make your requirements as comprehensive as possible. There are many standard parameters involved in malleable iron pipe fittings. We must communicate with the seller’s salesman in as much detail as possible, and do not miss any of them, so as to avoid unnecessary losses.

I believe that after reading this article, you must have a more comprehensive understanding of the technical parameters that should be paid attention to when purchasing malleable pipe fittings. Of course, these contents cannot be said to be very comprehensive. If you want to know more, you can open the link below to enter our website. The official website of Jianzhi Group is a huge treasure trove of knowledge about malleable products, I believe you can learn more here.