Working principle of spring type safety valve

The spring type safety valve is to press the valve core on the valve seat by the force of the spring, so that the safety valve is in the closed state, and the lower part of the valve core is pushed upward by the steam. During normal operation, the downward pressing force of spring is greater than the upward thrust of steam, and the valve is in closed state. When the steam pressure reaches the safety valve seat pressure, the force of steam on the valve core is greater than that of the spring, so that the valve core is jacked up and the safety valve of the rotor pump exhausts steam. Through the adjustment screw on the upper part of the valve stem, the tightness of the spring can be changed to adjust the seat pressure of the safety valve.
This kind of safety valve has the advantages of convenient adjustment, small volume and weight, and large exhaust capacity. It is suitable for boilers with different parameters and capacities.

Causes of abnormal hardness of spring steel spring

The hardness of spring steel spring leaf is insufficient or too high, or the hardness of spring steel spring leaf in the same batch is different, some of which are high or some are low. The main reasons are as follows:
The hardness of spring steel spring is insufficient after quenching

1) The heating temperature of spring is low or the holding time is insufficient. In this state, the content of carbon and alloy elements in austenite is not enough, and even there are some untransformed pearlite or undissolved ferrite in the spring structure, which leads to the hardness of the spring after quenching.

2) If the heating temperature is too high or the holding time is too long, the surface of the spring will be decarburized and the hardness will be reduced.
2. The hardness of spring steel spring is low after tempering
1) The hardness of the spring is too low after quenching, which leads to the low hardness.
2) The higher tempering temperature and longer holding time lead to lower hardness.

3. The hardness of spring steel spring is high. The main reason is lower tempering temperature or shorter holding time.

4. The hardness of spring steel spring is different in the same batch, the main reasons are as follows
The same batch of reed some hardness is insufficient, some high, in addition to technological reasons, heat treatment equipment is also a key factor. Due to the fact that the reeds are mostly heat treated in box type resistance furnace, the reeds are often packed in bulk in metal baskets, and the heating is very uneven, which is one of the important reasons for the uneven hardness of the same batch of reeds.

Solution: reasonable control of heating temperature and holding time, and corresponding inspection after quenching to prevent tempering hardness. In addition, the box type resistance furnace is mesh belt furnace, which can solve the problem of uneven hardness of the same batch of reeds.

Classification of iron

By use

Pig iron for steelmaking
Pig iron for steelmaking refers to the pig iron used for open hearth and converter steelmaking. Generally, the content of silicon is low (ω Si is no more than 1.75%), and the sulfur content is high (ω s is no more than 0.07%). It is the main raw material for steelmaking and accounts for 80% – 90% of the pig iron output. Steelmaking pig iron is hard and brittle with white fracture, so it is also called white cast iron

Cast pig iron
Cast pig iron refers to the pig iron used for casting various pig iron castings, commonly known as foundry iron. Generally, the silicon content is high (ω Si is up to 3.75%), and the sulfur content is slightly lower (ω s is no more than 0.06%). It accounts for about 10% of the pig iron output and is the main commercial iron in iron and steel works. Its fracture surface is gray, so it is also called gray iron

By chemical composition
Ordinary pig iron
Ordinary pig iron refers to the pig iron without other alloy elements, such as steel-making pig iron and casting pig iron
Special pig iron

Natural alloy pig iron
Natural alloy pig iron is a special pig iron made by reducing iron ore or concentrate containing associated metals such as copper, vanadium, nickel, etc. it contains a certain amount of alloy elements (one or more, determined by the composition of the ore), which can be used for steelmaking and casting

The difference between ferroalloy and natural alloy pig iron is that other ingredients are specially added during ironmaking to produce special pig iron containing various alloy elements. Ferroalloy is one of the raw materials for steelmaking and can also be used for casting. It can be used as deoxidizer and additive of alloy elements to improve the properties of steel

There are many kinds of ferroalloys, such as ferrosilicon, ferromanganese, ferrochrome, ferrotungsten, ferromolybdenum, ferrovanadium, ferrovanadium, ferroboron, ferronickel, ferroniobium, silicomanganese, rare earth alloys and so on, of which the largest amount is ferromanganese, ferrosilicon and ferrochrome. According to different production methods, ferroalloys are usually divided into blast furnace ferroalloy, electric furnace ferroalloy, extra furnace ferroalloy and vacuum carbon reduction ferroalloy

Representation of steel grades in South Korea

KS (Korean standard) is the code of Korean national standard. Since most of KS steel standards refer to Japanese JIS standard, the representation method of steel brand is basically the same as that of Japanese JIS standard. Some steel grades are only changed in the letter or order of brand number, while some are even the same as Japanese JIS standard. The brand is even the same. See table 1-23 for the substitutions of grades and the types of steel.
Brand letter
Types of steel
Brand letter
Types of steel
S ×× C
Carbon structural steel
High speed tool steel
Manganese structural steel
stainless steel
Chromium structural steel
Heat resistant steel
Cr Mo structural steel
Carbon cast steel
Ni Cr Mo structural steel
Heat resistant cast steel
Ni Cr Mo structural steel
High manganese cast steel
Free cutting structural steel
High manganese cast steel
Spring steel
Cast Jinshan (iron) with high temperature and high temperature
Bearing steel
Low temperature high cast steel
Alloy tool steel
Nodular cast iron
Carbon steel
malleable iron
① Scph is not only the code of high temperature and high pressure cast steel, but also the code of high temperature and high pressure natural iron. However, when the steel grade is composed, the tail of cast steel is only a numerical number, while the tail of cast iron grade is added with the letter “CF”, such as scph21-cf.

How to choose the most suitable shrinking machine

The buyer may find that the zinc layer is easy to fall off and scratch the mold base and cylinder block with zinc foam after using it for a short time after purchasing the pipe shrinking machine, and even damage the core parts. What should I do when I encounter this problem? How to choose a high-quality pipe shrinking machine? If your buckle press is not a new one, you will find that there is no resin sponge between the mold base of your buckle press. Who wants to replace it all the time with a shrinkage machine? How to maintain their service life? How to avoid this phenomenon?

working principle:
Driven by the motor, the oil pump outputs hydraulic oil to push the plunger in the buckle cylinder forward, so that the plunger and the two inner conical sleeves on the front cylinder head push the die base with symmetrical conical surface to shrink radially, so as to realize the module to buckle the rubber hose. When the shrinkage reaches the setting value of the scale, the buckle stops automatically, the solenoid reversing valve changes back, and the hydraulic oil enters the two mold opening cylinders to push the buckle plunger to move reversely, and the die seat drives the module to recover under the action of spring.
Working process: the fastening mechanism is the working mechanism of the locking machine. Driven by the cylinder piston, the pressing sleeve realizes reciprocating movement, and continuously compresses and relaxes the spring pressure head fixed on the front plate. Put the assembled joint into the appropriate position in the middle round hole of the spring pressure head, start the motor to drive the oil pump to supply oil, control the electromagnetic reversing valve to change direction, drive the oil cylinder piston to move forward, and press the spring pressure head with the same taper through the pressure sleeve with inner taper hole, so as to achieve the purpose of pressing. Press the mold opening button, the piston drives the pressing sleeve to move in the opposite direction, and the spring pressure head recovers. At this time, the hose joint can be taken out from the pipe locking machine.

Features of pipe shrinking machine:
(1) The upper part is provided with a holding part for stacking embryo tubes, and the front part is provided with a channel to guide the embryo tubes one by one to the front and fall to the bottom;
(2) A pushing device is arranged at the bottom of the blanking groove, which is provided with a receiving mechanism to receive the embryo tubes falling from the chute one by one, and a pushing feeding mechanism;
(3) The feeding device is provided with a movable claw cylinder which moves the embryo tube from the feeding position to the working position;
(4) The clamping device is provided with a clamping claw cylinder for clamping and positioning the embryo tube at the working position;
(5) The pushing positioning device is provided with a positioning die which can push forward and retreat at one end of the embryo tube;
(6) The double rotating shaft forging device is provided with a body which can advance and retreat, in which a roller group is arranged in a ring, and a rotatable mold holder is arranged on the inner side of the roller group, the mold holder is provided with a radial groove, two guide blocks are parallel arranged on both sides of the groove, and two separate moulds are arranged between the two guide blocks, and the outer side of the mold is provided with a roller group In addition, the center rotating shaft column can be set in two mold cavities, and then combined with the structure mentioned above, a new practical heat conduction pipe shrinking machine is formed.

Forming method of double torsion spring and double seal ring

Forming method of double torsion spring and double seal ring
Generally, if the outer diameter is not very large, the two sealing rings are formed on the mandrel! It is relatively stable! The back sealing ring is pressed by a thread gauge knife, and then the left or right two oblique knives are used to make the rear sealing ring! If the outer diameter is small, the left and right lower oblique knives can be used as auxiliary cores

Material selection of heat resistant spring steel

Specification for material selection and maximum service temperature heat treatment of heat resistant spring steel
Maximum service temperature of steel grade hot forming quenching temperature tempering temperature
50CrVA 300 880-900 850-870 oil 430-500
4Cr13 400 850-1050 980-1050 air cooling 540-560
Cold drawn 18-8 stainless steel wire 400, cold rolled, stress relieved and tempered at 400C, 15-60min
W18Cr4V 600 1000-1200 1280-1290 oil or air cooling 700
60Si2MnA 250 880-900 860-880 oil 350

Spring use and maintenance common sense oil outlet valve spring

Spring use and maintenance common sense oil outlet valve spring
After the spring force of the oil outlet valve decreases. It will cause serious internal leakage of high-pressure oil, reduce the residual pressure in the high-pressure oil pipe, and the oil outlet valve does not seat quickly, resulting in the reduction and instability of fuel supply, and the engine is unable to work and “travel”. In addition, it will make the fuel injector start to spray powerless, cut off the fuel not simply, and drop after the phenomenon, resulting in combustion deterioration, engine overheating, exhaust smoke. Therefore, the spring of the oil outlet valve should be replaced after 3600-4500 h of use. If there is bending deformation, it should be replaced in time.

Steering spring of walking tractor

Common sense of spring use and maintenance steering spring of walking tractor
When installing the steering spring, first identify the left-hand spring or the right-hand spring. The left side should be equipped with a right-hand spring, and the right side should be equipped with a left-hand spring. If the left and right springs are installed wrongly, the steering spring will be subjected to a reverse twisting force when the tractor turns, which will deform the spring, even break the spring, or scrape the inner step of the steering gear. Once the spring is broken and the steering handle is released, the steering gear will lose its thrust and the jaw will not return to its original position, which may lead to serious accidents.


Identification method of left and right rotation spring: hold the spring with left hand, thumb upward, and the other four fingers with the same direction of rotation as the steel wire are left-handed spring; otherwise, it is right-handed spring.
In addition, the insufficient spring force of the steering spring may cause the walking tractor to lose its handling stability. Therefore, the steering spring should be checked regularly. The inspection and adjustment method is the same as that of valve spring, but flat washer of the same thickness should be padded on both sides. Generally, it should be checked and adjusted once every four years.

Elastic force calculation method of compression spring and tension spring

Pressure spring
·In addition to the spring size, the design data of pressure spring need to calculate the maximum load and the load of deflection size;

·Spring constant: expressed by K, when the spring is compressed, the load (kgf / mm) of each increase of 1 mm distance;
·Spring constant formula (unit: kgf / mm)
G = steel modulus of wire: Piano steel wire g = 8000; stainless steel wire g = 7300, phosphor bronze wire g = 4500, brass wire g = 3500
D = wire diameter
Do = od = outer diameter
Di = id = inner diameter
DM = MD = pitch diameter = do-d
N = total number of turns
NC = effective number of turns = n-2
Calculation example of spring constant:
Wire diameter = 2.0 mm, outer diameter = 22 mm, total number of turns = 5.5 coils, steel wire material = piano wire

Tension spring
The K value of tension spring is the same as that of pressure spring
·The initial tension of tension spring: the initial tension is equal to the force required to pull apart the tightly attached spring and coil. The initial tension occurs after the spring is rolled and formed. When the tension spring is made, the initial tension of each tension spring is uneven due to the difference of steel wire material, wire diameter, spring index, static electricity, lubricating grease, heat treatment and electroplating. Therefore, when installing the tension spring of various specifications, it should be pre pulled until the parallel coils are slightly separated. The force required is called the initial tension.
·Initial tension = P – (K × F1) = maximum load – (spring constant × tensile length)

Torsion spring
·Spring constant: expressed in K, when the spring is twisted, the load (kgf / mm) of each additional 1 ° torsion angle
·Spring constant formula (unit: kgf / mm)
E = steel modulus of wire: Piano steel wire e = 21000, stainless steel wire e = 19400, phosphor bronze wire e = 11200, brass wire e = 11200
D = wire diameter
Do = od = outer diameter
Di = id = inner diameter
DM = MD = pitch diameter = do-d
N = total number of turns
R = arm of force under load