Because the non-metallic industrial pump has strong competition in corrosion resistance, abrasion and price, its application in industrial production is increasing. The following factors shall be taken into account when selecting non-metallic industrial pumps:

1. Mechanical properties

The pressure bearing parts of the pump must be able to bear the load or stress under the operating condition. If the design of metal industrial pump is simply applied to the design of non-metal parts, the parts are likely to fail. The excessive stress in the short connecting pipe area or bearing box of the non-metallic industrial pump may cause the pump casing to creep, resulting in the deformation or bending of the components and poor alignment. The solution to this problem is to calculate the stress level on the non-metallic parts and design within the allowable stress range.

2. Corrosion resistance and wear resistance

The corrosion resistance of non-metallic materials is generally better than that of metal materials at the same price.

The abrasive wear of metal materials is caused by the continuous falling off of the oxide protective layer on the metal surface, while non-metal materials do not need the protective layer, so they can better resist the less serious wear. The non-metallic materials with good wear resistance include industrial ceramics, wear-resistant rubber and ultra-high molecular polyethylene.

3. Temperature

The temperature resistance of non-metallic materials is much lower than that of metallic materials. Like metal, the mechanical properties of nonmetal decrease with the increase of temperature.

4. Weight and thermal insulation performance

Compared with the metal industrial pump, the non-metal industrial pump is light in weight and easy to install and maintain. In addition, the non-metallic material is a kind of natural insulation material, which does not need to be covered on the pump body.

5. Fire resistance

In a burning fire, thermoplastics will melt and burn, and thermosetting nonmetals will turn into carbon and ash. In order to prevent non-metallic materials from burning, flame retardant can be added. In addition, when providing products, the pump factory shall inform the user whether toxic smoke will appear when the materials are burned in the fire.

Structure of nonmetal industrial pump

1. Structural characteristics of non-metallic industrial pump

The typical structure of plastic lined non-metallic industrial pump is shown in figure l-40.

(1) The structure of the pump body of the non-metallic industrial pump body has two kinds: integral and lining. Integral pump body refers to the whole pump body is non-metallic, generally only applicable to small diameter centrifugal pump. Lining pump body generally refers to the material of pump body is cast iron or cast steel, and the lining layer is non-metal. The whole pump body can be made of thermosetting material and thermoplastic material. The lining pump is divided into elastic lining, spray lining and rigid lining. Nonmetal industrial pumps are generally single-stage, volute type, radial split structure.

For the integral pump body, ribs can be added to strengthen it. In order to prevent the stress vulnerability of the interface of the non-metallic industrial pump, front and rear cover plates can be added on both sides of the non-metallic industrial pump body, and bolts can be used for connection and reinforcement. The lining pump can be fixed by opening a suitable slot in the metal industrial pump casing. In addition, it can be considered to strengthen the shell by welding the tortoise shell wire mesh.

(2) The impeller of non-metallic industrial pump can also be divided into three types: open, semi open and closed. The closed impeller is made of thermoplastic, and the front and rear cover plates can be welded together by ultrasonic or vibration. Semi open, open impeller can be made of thermoplastic or thermosetting plastic.

Impeller is divided into integral structure and embedded metal structure. The impeller with integral non-metallic structure has low strength and is suitable for small pumps; the structure of embedded metal parts is molded with high strength.

1-pump housing; 2-impeller; 3-pump benefit gasket; 4-pump cover; 5-bolt; 6-gasket; 7-spring gasket; 8-screw key; 9-shaft sleeve; 10 seal; ll bracket; L2 oil seal; L3 oil plug; L4 oil drain hole; 15 bearing; L6 bearing seat; 17 main shaft; L8 bolt; L9 end cover; 20 foot; 21 pull rod; 22 base

(3) Sealing ring (port ring) non-metallic industrial pump is generally not provided with sealing ring.

(4) The shaft of the non-metallic industrial pump is generally not in contact with the medium, which is made of metal materials. One end is used to fix the impeller and the other end is used to install the coupling. The pump shaft and impeller of non-metallic industrial pump are usually connected by thread.

(5) The shaft seal types of non-metallic industrial pump include mechanical seal, power seal and non shaft seal structure (see Chapter 2 of Chapter 1 for details).

① Mechanical seal many domestic non-metallic industrial pumps usually use 152 type (or SBZ) external bellows multi spring single face mechanical seal. The pressure range of the seal is 0-0.5mpa, the shaft diameter is 25-55mm, the temperature is less than 120 ℃, the moving ring material is filled with tetrafluoron, and the static ring material is alumina ceramic. The seal can be used for hydrochloric acid with concentration more than 30%, dilute sulfuric acid with concentration less than 50%, phosphoric acid with concentration more than 98% and mixed acid with various concentrations. The service life of the seal is longer, generally more than 4000H. WB2 or 152 mechanical seal is mostly used for clean water medium and acid medium, and l69 mechanical seal is generally used for alkaline medium. When the working medium is special, other types of mechanical seals, including materials, shall be selected according to the characteristics of the medium.

② Power seal includes auxiliary impeller (or auxiliary blade) seal and stop seal. The sealing type is commonly used for conveying medium with solid particles, and generally suitable for medium with solid content more than 15%. The maximum allowable inlet pressure of the power seal pump shall be indicated to avoid a large amount of leakage when the user uses it at a higher inlet pressure.

③ Shaftless structure mainly refers to the non-metallic magnetic drive pump, which can be used to transport all kinds of liquids not allowed to leak.

2. Structural difference between non-metallic industrial pump and metal material pump

Due to the difference of performance between non-metal and metal materials, the structural design of non-metal industrial pump has the following particularity.

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