Design

1, valve body

Welding can be divided into the whole design and split-type valve body design.

The design of welded tubular body structure and globular structure, tube-like structure is a two-seam, welding heat input process, and residual stress of the complexity of large axial and radial deformation. Cameron is a spherical structure of the four seam stitching, and now as a result of technology advances in the use of hot-forging forming body around to the middle of forming a single seam welding to reduce the line energy input, reduced axial and radial deformation.

Split-type structure in general and about the connector body composition. Connector to connect with the valve body by bolts connecting the flange thickness and bolt connection strength and the body should be substantial diameter flange for analog design, the connection strength must be generated to prevent the pipeline to connect the stress relaxation, so that seal failure. Valve face-to-face contact with the connector, the middle without gaps. Seal must meet fire safety requirements, the use of rubber "O"-ring and the combination of coiled metal sealing pad. Figure (e) below.





Figure (e) with the connector body structure fire



Body of material for forging, temperature-29C ° above the selection of ASTM A105;-29C ° the following selection of ASTM A350 LF2. Body for welding of A105 or LF2 material chemical composition, carbon content and carbon equivalent as well as sulfur, phosphorus and other elements of special restrictions should be otherwise. Forgings forgings in accordance with the standard three-acceptance, to do 100% non-destructive testing, weld inspection and shading to do ultrasonic testing.

2, sealed with the seal seat

The use of combination of valve seat sealing structure, that is, the initial metal on metal "sealed" in order to block the entry of solid particles; rubber, PTFE plastic, nylon, PEEK, such as soft as a secondary seal sealed in order to ensure "zero" level leak, Figure (f) below. However, due to pipeline accidents in the foreign body into the soft sealing material on the damaged pipeline ball valves are equipped with emergency sealant injection system, to obtain temporary sealing requirements.





Figure (f) combination of sealing structure



Sealed with rubber ring has a circular, triangular or other special shapes. Each company has its own design of structural and technological measures to prevent the rubber band in the switching process begins (Blow out) or a bad cut. Class900 level for more than pounds, should use explosion-proof step-down (AED) characteristics of the material as O-ring material.

PTFE seal of the general use of tube-like mosaic structure, and can also be combined into barb-like structure, designed to ensure the seals are not a result of seal failure begins.

Valve seat seal material with the same materials, electroless nickel plating, there are spring loaded to ensure that the initial sealing pressure, springs can be coil spring, plate spring or disc spring, materials for Inconel X-750.

Import and export of client-side seat seal design using two-way symmetrical. This piston seal structure of the medium since, in accordance with customer needs can be designed as a "single-piston effect" (Single piston action), the pressure from the discharge sealed Block structure (Figure 7) and "double piston effect" (Double Piston effect) a double sealing structure. (Figure 8)





Figure (g) discharge pressure seal seat





Figure (h) "dual-piston effect" (Double Piston effect) the structure of double-sealed



Single-piston-side sealing effect that is the import, export client automatically discharge chamber pressure.

Dual-piston side effect that imports and exports at the same time the closed-end, whether gas or liquid dielectric medium, the cavity must be equipped with safety valves, discharge pressure to ensure that.

Effect of single-and dual-piston design piston effect of the valve seat, the chamber pressure there is a difference between emissions. Effect of dual-piston design is more than the pressure of the pressure chamber the pressure of the corresponding level of 1.33 times the value of emissions and discharges to the atmospheric environment. The effect of single-piston design is as long as the chamber pressure is greater than the downstream end of the pipeline pressure downstream pipeline to automatic discharge. Therefore, the general effect of company products as a single-piston standard products, products effect dual-piston products as an option.

Set up a safety valve, the valve diameter should be ≥ 1 / 2 ", discharge pressure of ≤ 1.33 times the rated pressure. Valve seat body and connected with the Department should have a fire safety design, with the valve seat to connect the body surface with the Department of electroless nickel plating should be local .

3, ball bearing axle and

Ball diameter pipeline (2 "or 2" above) are using the ball bearing, the floating valve seat structure (Trunnion mounted Ball and Floating Seat). The role of media in the ball on the edge there are two sliding bearing support for high-pressure, large diameter, the axial thrust to reach dozens to hundreds of tons of tons of pressure sliding axis must be calculated, the allowable pressure not suppliers over the sliding sleeve allowable pressure. Many companies are using stainless steel as a substrate, PTFE plastic lining, which sets bearing bearing pressure of up to 200 ~ 400Mpa, the allowable pressure from 100 ~ 200Mpa, and low coefficient of friction, which reduces torque ball valve operation.

Shaft bearing design, one is turning into the ball up and down the journal, and two upper and lower bearing support plate, built by the middle of PTFE-lined stainless steel sleeve, the bearing journal axis length L and the ratio of d, due to the structure of restricted access L / d = 0.4 ~ 0.8. Another design is turning into a ball inside the hole, up and down by the two supporting shafts, bearings in the body, this design generally L / d = 1.2 ~ 2.. This two kinds of structure, the former because of the short thick neck, so the resistance moment of a larger ball valve, which supports the on-axis, and at the same time stem the transmission of torque, it is in a complex stress state, the bearing axis (stem) of the material can be selected to be ANSI 4140 and electroless nickel plating. Stem the transmission of torque with the ball can be single, double, Spline connection, also directly connected with the ball after the welding assembly of the structural design.

Sphere of the machining accuracy, roundness ≤ 0.005mm, electroless nickel plating, coating thickness of the coating above the valve seat.

For large-diameter, high pressure ball valves class should be calculated ball deformation, such deformation can cause seal failure.

4, stem and packing

Stem safety design standards should be under pressure at work to prevent the "blow", the anti-stem begins with a circular flange disposed of Central, in order to reduce the friction coefficient. Can fill two "O"-ring seal, can be used to shape皮碗packing with PTFE processing and packing graphite fire safety and emergency sealant injection of external systems. Interface with the ball in the stem and the valve stem contacts with the Department should have a anti-static institutions, to prevent static electricity in the ball on the concentration, in Figure (i) as shown.









Figure (i) the structure of stem and packing



5, DBB function design

DBB is the functional design, whether in open or closed valves, and pressure relief valve discharge chamber, the upstream end and downstream end of the valve seat should be closed at the same time (Double Block & Bleed), and from the discharge valve to allow the Agency to carry out on-line valve seat sealing performance tests, without affecting the operation of the pipeline.

6, the design of sealing systems for emergency

Emergency sealing system consists of a syringe (Injector) and Check Valve (Check Valve), namely the installation of the valve body, in the seat outside the Department of Measurement and lateral stem packing Department. Emergency sealing system can be used to prevent or reduce the pipeline block valve seal leakage, sealant injection to carry out pre-cleaning and washing, and cleaning agents specialize in the production of resin and sealed with manual or electric tools to cleaning agents or sealed resin from the syringe into the mouth, and suppliers by using the instructions provided by emergency cleaning and sealing operation. (Figure 10)





Figure (10) syringes with non-return valve



7, fire safety and anti-static design



Fire safety and anti-static design axis in the bearing, sealing Block be disclosed in the notes section, anti-static structural design, measured in 24VDC, resistance value does not exceed 10 ohms.

8, valve operation

Valve operation, a manual, worm gear drive, pneumatic (dual-role or spring reset), high-pressure pneumatic (direct use of gas pipelines), electric, hydraulic (double acting or spring-reset), as well as gas-liquid interaction. Gas-liquid interaction can be the implementation of local and remote control, remote control and satellite line of SCADA system, when the pressure drop downstream of the rate or duration of super-multi-set value, (ie, burst pipe), emergency shut-off valves automatically cut off, and with Accumulator of emergency, and for manual operation.

9, the end of the design

Connect client based on customer requirements, and end the flange connections and welding end.

Flanged connection or convex side to bring the annular trough, and its size, tolerance and smoothness, as well as drilling, flange face, countersink holes, down hole, such as the following criteria should be;

DN600 and below, in accordance with ASME B16.5, which DN550 by MSS-SP44;

DN650 and above in accordance with ASME B16.47 Series A

Welding should end section 434.8.6 of ASME B31.4 Figure (1), (2) or ASME B31.8 in Figure (14) and (15).

10, bolts

Bolt body with ASTM A 193 B7 materials, nut with ASTM () manufacturing, and in accordance with the provisions of NACE-TM 0284, customers can ask for coloring test, according to ASME section V to chapter 24.

11, direct-buried underground

Directly buried underground valve for the whole pipeline welding ball valve body, stem length according to customer access, then a long stem should be firmly part of the design that can carry anti-ground, all the valve on the connecting pipe, sealant injector, at the bottom discharge valve, safety relief devices have access to the surface, to take over the welding and body. Then the design of long-rod, the long axis of the drive chain around the song and the gap junction to be controlled to prevent the switching process, the ball can not be accurately or in a related position to open, resulting in transmission errors.

12, the scope of

According to API standards 6D, as well as equipment manufacturing, product supply range:

Class100-600 pounds class DN1 / 2 "-60"

Class900 pound class DN1 / 2 "-36"

Class1500 pound class DN1 / 2 "-16"

Class2500 pound class DN1 / 2 "-12"

On special occasions, foreign suppliers to provide:

Class150-600 pounds maximum class size to DN72 "

The largest diameter class Class900 pounds to DN40 "

The largest diameter class Class1500 pounds to DN36 "

The largest diameter class Class2500 pounds to DN24 "

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