The inherent corrosion resistance of stainless steels is derived from alloying the base iron with chromium. BS EN 10088-1 states that a steel must have a minimum of 10.5% (by weight) chromium and a maximum of 1.2% carbon to be classified as 'stainless'.Other alloying elements including nickel, molybdenum, nitrogen, titanium (or niobium) are added to form the various grades. These additions are made to enhance the 'basic' corrosion resistance of the steel but can also usefully modify other properties, such as formability, strength and cryogenic toughness.The corrosion resistance of stainless steel arises from a 'passive', chromium-rich, oxide film that forms naturally on the surface of the steel. Although extremely thin at 1-5 nanometres (i.e. 1-5 x 10-9 metres) thick, this protective film is strongly adherent, and chemically stable (i.e. passive) under conditions which provide sufficient oxygen to the surface. This 'normal' condition is the passive state.The key to the durability of the corrosion resistance of stainless steels is that if the film is damaged it will normally self repair (provided there is sufficient oxygen available). However, under certain conditions, the passive state can be broken down, resulting in corrosive attack.If damaged, the film will normally repair itself. If the film is destroyed the surface is said to be in the active state.
The most common forms of corrosion in stainless steel are: a.Pitting corrosion - The passive layer on stainless steel can be attacked by certain chemical species. The chloride ion Cl- is the most common of these and is found in everyday materials such as salt and bleach. Pitting corrosion is avoided by making sure that stainless steel does not come into prolonged contact with harmful chemicals or by choosing a grade of steel which is more resistant to attack. The pitting corrosion resistance can be assessed using the Pitting Resistance Equivalent Number calculated from the alloy content.b.Crevice corrosion - Stainless steel requires a supply of oxygen to make sure that the passive layer can form on the surface. In very tight crevices, it is not always possible for the oxygen to gain access to the stainless steel surface thereby causing it to be vulnerable to attack. Crevice corrosion is avoided by sealing crevices with a flexible sealant or by using a more corrosion resistant grade.c.General corrosion - Normally, stainless steel does not corrode uniformly as do ordinary carbon and alloy steels. However, with some chemicals, notably acids, the passive layer may be attacked uniformly depending on concentration and temperature and the metal loss is distributed over the entire surface of the steel. Hydrochloric acid and sulphuric acid at some concentrations are particular aggressive towards stainless steel.d.Stress corrosion cracking (SCC) - This is a relatively rare form of corrosion which requires a very specific combination of tensile stress, temperature and corrosive species, often the chloride ion, for it to occur. Typical applications where SCC can occur are hot water tanks and swimming pools. Another form known as sulphide stress corrosion cracking (SSCC) is associated with hydrogen sulphide in oil and gas exploration and production.e.Intergranular corrosion - This is now quite a rare form of corrosion. If the Carbon level in the steel is too high, Chromium can combine with Carbon to form Chromium Carbide. This occurs at temperatures between about 450-850 deg C. This process is also called sensitisation and typically occurs during welding. The Chromium available to form the passive layer is effectively reduced and corrosion can occur. It is avoided by choosing a low carbon grade the so-called 'L' grades or by using a steel with Titanium or Niobium which preferentially combines with Carbon.f.Galvanic corrosion - If two dissimilar metals are in contact with each other and with an electrolyte e.g. water or other solution, it is possible for a galvanic cell to be set up. This is rather like a battery and can accelerate corrosion of the less 'noble' metal. It can avoided by separating the metals with a non-metallic insulator such as rubber.
When the surface of stainless steel pipe appears brown rust (point), people were surprised. The general perception towards stainless steel is that it is a super alloy that never rusts. However, the reality is that stainless steel does rust. The word “stain-less” does not imply free from stain or “stain-impossible”. It simply means that the alloy stains less. This is exactly the case with stainless steel. When compared to other metals and alloys, stainless steel the most resistant to corrosion. Stainless steel is an outstanding material with its high resistance to oxidation (rust) and corrosion in many different environments. Such as 304 steel pipe, in the dry and clean atmosphere, there is absolutely excellent resistance to corrosion, but it moved to the near sea area, used in a fog which has large amount of salt containing, will get rust rapidly. Therefore, there not have any kind of stainless steel, in any environment can be resistant to corrosion and not rust.
1. Water cleaning by degreasing agent, cleaning by Supersonic Machine. 2. Dipping in solvent, cleaning by hot water. 3. Dry blowing by air. 4. Final inspection by white cloth for detecting contamination. 5. Pressure testing and visual inspection.
Water hammer (or, more generally, fluid hammer) is a pressure surge or wave caused when a fluid (usually a liquid but sometimes also a gas) in motion is forced to stop or change direction suddenly (momentum change). A water hammer commonly occurs when a valve closes suddenly at an end of a pipeline system, and a pressure wave propagates in the pipe. It is also called hydraulic shock.Check Valves Alleviate Water Hammer
A check valve, clack valve, non-return valve (NRV) or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves work automatically and most are not controlled by a person or any external control; accordingly, most do not have any valve handle or stem. There are various types of check valves used in a wide variety of applications. Basically, check valve is doing the function of avoiding reverse flow no matter what the type is
Yes, but it should back to the factory to do replacing.
Please provide working temperature, media, flow, flow rate, working pressure and other detailed information can be estimated parameters for reference, the use of the environment and the situation we do not know clearly, so the data we gave just for reference, cannot be accurate completely to use.
Absolutely, but there need charge freight if not over a certain amount and price.
WCB/CF8/CF8M/CI/DI/B148 C95800(ALBC3) we usually have stock as above; However, to some special materials, like A8904A/CF3M…etc. We need evaluate if it need MOQ or not.NBR→Usually used in WATER & WASTEWATER TREATMENT. EPDM→Usually used in OIL & GAS. VITON→Usually used in CHEMICAL & PETROCHEMICAL. METAL (Same as Body)→Usually used in HIGH TEMPERATURE ENVIRONMENT, HAVE LEAKAGE.※Rubber seat zero leakage Metal seat leakage permitted values according to standard API598, permitted value is “size*700c.c”/MinOtherwise, we have special type named “__________” Under no pressure environment, no leaking when you pouring water into valve.
Getting too close to pump, easy to produce spoiler, and damaged valve quickly, furthermore shorten the life of the valve. With our years of experience in manufacturing valves, it should be expanded durability if followed our recommendation
we will email our Installation and maintenance instruction for your reference at first transaction.