Pneumatic valve material selection:

1, the metal material; material is a critical factor, such as material properties, creep, thermal expansion coefficient, oxidation resistance, wear resistance, abrasion resistance and thermal heat treatment temperature, which is a matter first of all should pay attention to. At high temperatures, creep and rupture is one of the main factors in material damage, particularly carbon steel, when long-term exposure to 425 ° C above the steel carbide phase may be converted to graphite, and for austenitic stainless steel Only when the carbon content exceeds 0.4%, it can be used more than 528 ° C. Therefore, when used at high temperatures should be calculated separately body material tensile strength, creep, high temperature aging and other parameters. As for the trim design, it should also consider the additional material at high temperature hardness, thermal expansion coefficient with the member, the guide member hot hardness difference, elastic deformation, plastic deformation. In the design, should be given appropriate safety factor and reliability factor to ensure avoidance of damage in a multi-factor generated. And to be familiar with the material under high temperature creep rate to select the appropriate stress, bringing the total creep material within the range of normal life does not extend to allowing it to produce micro cracks or deformation without affecting the normal use of the guide member.
To avoid the pneumatic valve internals (FD-LOK Monoflange needle valve, valve seat) surface abrasion, erosion and cavitation, high temperatures hot hardness of the material to be considered to prevent metal hardness change. In the high differential pressure, most of the energy of the fluid concentrated in trim were released, the inner parts of the valve that might have excessive load, and the high temperature mechanical properties of most materials deteriorate, material softens greatly affect the valve life member. Therefore, the correct choice of appropriate materials, to extend the life of the valve. Also, consider the effect of high temperature aging on the physical properties of materials, such as between toughness and corrosion changes. When the temperature reaches or exceeds the heat treatment temperature, the trim will have annealed, hardness decreased and other issues, in order to prevent changes in hardness of the material, the maximum temperature limit must be selected within a safe range. The same media, at high temperatures, the molecular activity is relatively active, some media have generally corrosive to the body and may trim metal serious corrosion damage, state media with high-speed ion penetration metal interior, so characteristic of the material changes, such as thermal expansion, intergranular corrosion, etc. Therefore, the choice of materials, in addition to cost, should also consider the failure of the multi-factor generated.
High differential pressure at high flow rates, even if the temperature is normal, it should assess the characteristics of the material, and the material to meet the conditions. In general, at room temperature, when the pressure exceeds 15bar, it should spool valve seat material 316 is adjusted to Stellite surfacing alloy or higher requirements, for weak corrosive media, the choice 420QT (quenching and tempering), 440QT like. High differential pressure, high flow rates can lead to serious erosion or cavitation, which is the trim material damage is very large, therefore, the material requirements of the valve body and trim is very high, the spool should consider using stainless steel surface nitriding (HRC70) process, so that it has a strong resistance to erosion, improve accuracy and service life of the valve flow. Oxidation resistance at high temperatures the material, but also a very important parameter. In the temperature cycling, and the choice of materials should avoid repeating material surface oxidation, producing oxide and other issues. Under normal circumstances, the Department of austenitic stainless steel, carbide Department and the Department of special alloy material has good temperature stability, the choice of suitable materials depending on the temperature conditions.
2, non-metallic materials
General non-metallic materials can not withstand high temperatures (300 ° C or more), but flexible graphite can withstand temperatures above 700 ° C, and therefore high-temperature conditions, both static seal or dynamic seal, generally can choose flexible graphite or composite materials, it should be noted that the coefficient of friction increases.

Structure and thermal conductivity of the pneumatic valve component selection:

High temperature and high pressure differential FD-LOK instrument check valve design, it must carefully consider the impact of thermal expansion of the different components of the trim operation. When the high temperature medium flows through the valve, since the coefficient of linear expansion of the valve body is often smaller than the linear expansion coefficient of the valve seat, the valve seat so that the valve body limits the radial expansion of the inner diameter of the expansion valve can only, at a high temperature so that the valve working gap between the core and the valve seat is less than the gap between the standard design at room temperature, resulting trim stuck. Spool and the guide sleeve will produce the same phenomenon. Thus, when the valve used in high temperature, room temperature design space standard valves (including inter-valve, valve seat; guide sleeve, between the stem) should be appropriately increased, so that it will not work stuck phenomenon occurs at high temperatures . Therefore, the gap design is very important because confirm material, size and temperature parameters on poor design staff is very important, at present, the corresponding data can be obtained from "ASME Boiler and Pressure Vessel Code Material D Part Ⅱ Performance" in.
Request a higher amount of leakage occasions valve and valve seat as far as possible the same alloy steel, and a single seat or cage structure, try to avoid using the valve seat structure, but also in the sealing surface hardening process, so as to avoid high temperature dramatically increasing the amount of valve leakage. It should also consider the body, bonnet and connectors withstand damage caused due to the additional load caused by high temperatures.
Cyclic changes in temperature cause the seat and the guide sleeve is loose, it must be sealed lap welding and welding to locking or clamping structure. Seat gasket seal is greater than the yield limit gasket sealing force to be able to get, but at a high temperature, high pressure and thermal cycling conditions, the sealing material creep arising from leakage, the seat can be used as a whole, by a valve made directly on the body and hardened valve seat. For large diameter valves, welding seat on the body, removing shims to avoid unnecessary leaks. Depending on the temperature level of the medium, but also consider the stuffing box packing can withstand temperatures and actuators can withstand temperatures.

Fully welded ball valve installation:

1, the valve lifting. Lifting should be the right way valve, in order to protect the valve stem, do not sling tied to the hand wheel, gear box or actuator. Protective cap sleeves at both ends of the valve not removed prior to welding.
2, the valve welding process. Buried fully FD-LOK Mini needle valve and trunk pipeline connection to take welding. Weld quality must meet the "disc flexor fusion welded joints radiography" (GB3323-2005) Ⅱ grade sheet standard, usually once a weld does not fully ensure that all qualified, so when ordering valves at both ends of the valve should require manufacturers to increase 1.0m long sleeves, welds failed once there is enough length to cut off defective weld and re-welded ball valve and pipe welding time, the valve should be at 100% full open position, so as not to damage the valve ball welding slag splashing, while ensuring internal valve seal temperature up to 140 degrees Celsius, cooling can take appropriate measures when necessary.
3, install valve well cast. FD-LOK bellows seal valves using a special design, with maintenance-free features, buried on the outside of the valve before coating Pu special anti-corrosion coating, while the three were urgent grease the seat and stem injection tubes, Cavity appropriate to extend the vent pipe and valve stem according to Huang to depth, so that staff can be on the ground to complete the operation. To achieve buried after laying a small hand valve shaft can be, and for conventional non-welded ball valve can not be directly buried, and need a large masonry valve well, the result is the formation of a dangerous confined space, is not conducive to safe operation . At the same time the body itself and the bolt body and the pipe joints will be electrical corrosion, affecting the life of the valve.

American Standard ball rolling thread less susceptible to shear forces and require less friction torque.

Rolling Thread can also benefit long-term. To save space parallel to the valve can be made compact, short structure. These three way ball valves are sometimes referred to as "clip-gate" in this, "WAFER", is used to mean "thin." These valves are not as literal as lazy thinking sandwiched between two pipe flanges. But the flange machined directly on the boring body length of the valve is reduced. Flange simply refers flange, stud or bolt and nut with two nuts can not be used.
For those who have not may disassemble the valve assembly, the American Standard ball valve connecting surface can be equipped with studs, you must use the substitutability of bolts.

Floating ball valve

The FD-LOK High pressure ball valve is floating at medium pressure, the ball can produce a certain displacement and pressed on the sealing surface of the outlet end, to ensure that the outlet end seal.
Simple floating ball valve structure, good sealing, but the ball all bear the load of the working medium to pass the exit ring, so to consider the ring material can withstand the work load media sphere. This structure is widely used in the low-pressure valve.

Fixed ball valve

The FD-LOK high pressure ball valves manufacturers is fixed, no movement after compression. Fixed ball valve comes with a floating valve seat, by medium pressure, the valve seat to move, so that seals pressed onto the ball, in order to ensure the seal. Usually with the ball, the lower shaft with bearings, operating torque, suitable for high pressure and large diameter valves.
To reduce the valve operating torque and increase the reliability of the seal, valve seals in recent years has emerged, both pressure injection of a special lubricant between the sealing surface to form a layer of film that enhances the tightness, but also reduce operating torque more suitable large diameter FD-LOK High pressure ball valve

Elastic ball valve

The ball valve is elastic. FD-LOK Ball valves seat rings are metal materials, sealing pressure than the large, rely on the pressure medium itself has reached less than the requirements of the seal, must apply force. This valve is suitable for high temperature and high pressure medium.
Elastic sphere is a sphere at the lower end wall to open a resilient groove, and access flexibility. When closing the channel, with the stem of the wedge-shaped head with the ball to open up the valve seat seal. Loosen before turning the ball first wedge-shaped head, the ball along with restoration of the original prototype, make small gap, sealing surface can reduce friction and operating torque between the ball and seat.
Ball can be divided according to their channel positions straight-through, tees and right angle. After Instrumentation ball valves for dispensing the media and change the flow of the medium.