INTRODUCTION 

A fitting or adapter is used in pipe systems to connect straight sections of pipe or tube, adapt to different sizes or shapes, and for other purposes such as regulating (or measuring) fluid flow.[1] These fittings are used in plumbing to manipulate the conveyance of water, gas, or liquid waste in domestic or commercial environments, within a system of pipes or tubes.
Fittings (especially uncommon types) require money, time, materials, and tools to install, and are an important part of piping and plumbing systems.[2] Valves are technically fittings, but are usually discussed separately.

Ductile iron pipe fittings are made of magnesium or rare earth magnesium combined with gold spheroidizing agent, which is added into molten iron before pouring to spheroidize graphite to reduce stress concentration, so that the pipe fittings have the advantages of high strength, high elongation, impact resistance, corrosion resistance and good sealing; 

PERFORMANCE REQUIREMENTS
1. Surface quality
(1)The internal and external surfaces of ductile iron pipe fittings must be smooth, and there are no obvious defects that hinder the use, such as cracks, cold insulation, wrong boxes, etc. local defects that reduce the wall thickness are allowed, but their depth shall not exceed (2 + 0.05T) mm, where t is the wall thickness of the pipe body.
(2)The spare flange of ductile iron pipe fittings shall have a clear outline and shall not have casting defects affecting the use.
(3)with the consent of the buyer, the partial defects that are not affected may be repaired, but the repaired fittings must be re tested for water pressure or tightness.
2. Coating
(1)The internal and external surfaces of ductile iron pipe fittings can be coated with grid asphalt or other anti-corrosion materials. If there are special requirements, they shall be determined through consultation with the supplier and the buyer.
(2)When the ductile iron pipe fittings are used for water supply, the sanitary conditions shall comply with the relevant provisions of the health department.
(3) Before coating, the inside and outside of pipe fittings shall be cleaned. After coating, the inside and outside surfaces shall be smooth, the coating shall be uniform and firm, and there shall be no abnormality due to climate change.
3. Characteristic
Strong corrosion resistance, good pressure resistance and bending resistance, convenient joint, no peculiar smell in water, harmless to health, etc
4. Superiority
(1)Due to its flexible joints, the construction operation is more convenient, which can improve the construction efficiency, improve the construction conditions and reduce the construction cost. Moreover, most of the interfaces are connected by rubber rings, which is simple to operate, which can shorten the construction period and reduce the construction cost.
(2)Ductile iron pipe fittings can bear high water supply pressure, resist external load and adapt to the changes of geological conditions. The pipe has the advantages of high strength, good toughness, corrosion resistance, convenient installation of flexible interface, strong seismic resistance and low labor intensity. It can be applied to sections with Poor Geology and cross highways without additional processing of steel pipes. In addition, it has strong corrosion resistance and can be applied to coastal and saline alkali areas. It is widely used in underground pipeline engineering. The large-scale pipeline installation project can better reflect its advantages of convenient installation and low labor intensity.
(3)ductile iron pipe fittings have good sealing performance and are not easy to leak, which can reduce leakage rate and reduce daily maintenance cost of pipe network.