PHMB is a disinfectant used in disinfection of swimming pools, hot tubs and contact lenses. According to research, swimming pools have proven to be one of the main vectors of adenovirus eye infection transmission. So, how do we determine whether PHMB is an effective disinfectant for ordinary eye Ad serotypes?
Method
The direct antiviral activity of PHMB was determined by incubating high concentrations of clinical isolates Ad1, Ad2, Ad3, Ad4, Ad5, Ad7a, Ad8, Ad19, and ATCC Ad37 at 30 and 20 PPM at room temperature or 40 degrees Celsius. The PHMB and control medium are left for 24 hours.
Standard plaque assays were performed on the reaction mixture to determine the AdMB concentration after PHMB or control treatment. Logically convert the AD concentration and calculate the Log 10 reduction in titer relative to the control.
Result
At room temperature, for any Ad serotype tested at 30 or 20 PPM, the concentration of PHMB does not produce a decrease of> 10 Log10. However, at 40 degrees Celsius, for Ad1, Ad3, Ad5, Ad8, Ad19 and Ad37, the Ad titer of PHMB at 30 and 20 PPM decreases> 10 Log10, but not for Ad2, Ad4 and Ad7a.
In conclusion
When PHMB is used to disinfect swimming pools and hot tubs, it does not reduce AD concentration at room temperature. When the temperature rises to 40 degrees Celsius, the effect of PHMB reducing Ad concentration is enhanced, but the effect does not cover all tested Ad serotypes.
In swimming pools, PHMB does not seem to be an effective disinfectant against Ad, but only moderately effective in hot tubs.
Tag: PHMB Powder CAS 32289-58-0
There are roughly three types of modified shock absorbers-short springs(helical compression spring), twisted teeth, and pneumatic. Today I will talk about the role of short springs in shock absorption.
Springs, which are common in life, are compressible and expandable. The use of springs in cars can reduce vibration, especially for poor road conditions, allowing the wheels to better contact the ground, increasing comfort and safety.
Progressive spring
This kind of spring adopts a design with inconsistent thickness and density. The advantage is that it can absorb the undulations of the road through the part with a lower elastic coefficient when the pressure is not large, ensuring the riding comfort, and the thicker part when the pressure increases to a certain degree The spring plays the role of supporting the body, and the disadvantage of this spring is that the control feeling is not direct and the accuracy is poor.
Linear spring
The thickness and density of linear springs are unchanged, and the elastic coefficient is a fixed value. This design of the spring can make the vehicle obtain a more stable and linear dynamic response, which helps the driver to better control the vehicle.
Short spring(helical compression spring)
That is the short spring that everyone usually talks about. The length of the short spring is shorter than that of the progressive spring, and it is also thicker. The installation of short springs can effectively reduce the center of gravity of the vehicle body, reduce the roll produced during cornering, make cornering more stable and smooth, and improve vehicle cornering control.
The damping setting of the progressive spring shock absorber is more comfortable, so the short spring and the original shock absorber are not very stable in cooperation. It cannot effectively suppress the rebound and compression of the short spring. When driving on bumpy roads, it will There is a sense of discomfort in jumping.
Replacing the short spring is the most affordable conversion option to reduce the height of the vehicle. Although the replacement of the short spring will improve part of the controllability, but the space for improvement is limited, and if the road conditions of the vehicle are complicated, the shock may be affected in the past.
Tag: Trampoline Spring ; Garage Door Torsion Spring ; Helical Compression Spring ; Garage Door Torsion Springs ; Garage Door Torsion Spring for Rolling Shutter ; Heavy Duty Garage Door Spring
First, the working principle of screw compressor refrigeration unit
Screw refrigeration compressor is a new type of high-speed compressor. The principle of increasing gas pressure is the same as that of piston compressor, which belongs to volumetric compression. At present, twin screw compressors are generally used. Twin screw compressors use two mutually intermeshing screws to make relative rotational movements to compress the gas.
With the rapid development of the refrigeration industry and the improvement of processing methods, screw compressor refrigeration units have developed greatly. The cold storage is gradually becoming larger, the types of units are increasing, the scope of use is expanding, and it is expanding to different application areas.
Driven by the motor, the driving rotor rotates with the motor, and at this time, the driven rotor that is engaged also follows the opposite direction. In the rotor movement, when a pair of meshing grooves of the driving rotor and the driven rotor communicate with the suction duct, sufficient suction is performed. When the rotor continues to rotate, the pair of suction grooves leaves the suction orifice on the suction end face, and the gas in the tooth groove enclosed by the suction and exhaust end seats is isolated from the outside of the casing and begins to be compressed.
The driving and driven rotors continue to rotate, and the tooth peaks of the driving rotor continuously fill the tooth valleys of the driven rotor. Similarly, the tooth peaks of the driven rotor also continuously fill the tooth valleys of the corresponding driving rotor. As a result of the mutual filling, the groove volumes of the respective rotors are gradually reduced, and the gas in the grooves is gradually compressed. When the gas pressure reaches the specified value, the rotor is turned to a position where the groove communicates with the exhaust port to discharge the gas. Such continuous operation, the refrigerant is continuously compressed and discharged from the screw compressor refrigeration unit.
Screw refrigeration compressors inject a large amount of oil during the compression process, which can take away the heat generated during the compression process. At the same time, the oil film is used to seal the gap between the female and male rotors and the gap between the rotor and the cylinder, so that internal leakage losses are reduced.
Advantages and disadvantages of screw compressor refrigeration unit
1. Main advantages
(1) Easy management
The screw compressor refrigeration unit has no suction and exhaust valves, pistons, piston rings, cylinder liners and other fragile parts, which is convenient for maintenance and repair. Smooth and reliable operation, easy to realize long-distance operation and automation.
(2) High speed and good economic performance.
Screw compressors are rotary machines. Because there are no suction and exhaust valves, the speed can be increased. Usually the speed is 1500-3000 / min, which is generally higher than the speed of piston compressors, thus improving the economic indicators.
(3) Small size and light weight.
Due to the high speed, when the exhaust volume is the same, the machine is small in size, compact in structure, light in weight, low in metal consumption, and small in area.
(4) The foundation is small.
Since the screw compressor refrigeration unit does not have the mass inertia force of the piston compressor and the dynamic balance performance is good, the foundation can be made small.
(5) Strong adaptability to operation.
Can be applied to a variety of refrigerants, high volume efficiency. Good performance even at low evaporation temperatures and high compression ratios. Because there is no clearance volume, the volumetric efficiency is much higher than the piston type.
(6) The exhaust temperature is low.
With oil injection cooling, the exhaust temperature is lower than the reciprocating type, so single-stage compression can still be used at higher compression ratios. When the evaporation temperature is -40 ° C, the discharge temperature is less than or equal to 90 ° C, which is beneficial to the operation of the machine.
(7) Continuous stepless adjustment.
Since the most widely used current is the use of slide valves for energy adjustment, the refrigeration capacity can be adjusted steplessly within the energy range of 10% to 100%, achieving continuous stepless adjustment.
(8) There is no danger of liquid strike.
Due to the structural characteristics, the screw compressor is not sensitive to the wet stroke. It can allow wet vapor or a small amount of liquid refrigerant to enter the body without the risk of liquid strike.
2. The main disadvantages
(1) Rotor processing is difficult.
The rotor requires high machining accuracy and is difficult to process, requiring special equipment.
(2) The auxiliary equipment is huge.
For screw compressor refrigeration unit, in order to separate the lubricating oil in the exhaust gas, an oil separator and an oil return device with large volume, complicated structure and high efficiency are required.
(3) The noise is large.
Because the rotor cogging passes through the suction and exhaust orifices at high speed periodically, and leaks through the gap, the noise is relatively large. Generally, if all screw-type refrigeration compression is set in the machine room, the machine room should not be close to the main warehouse or other workshops. It is better to leave it separately from other buildings.
Tag: Modular Cold Room Cold Storage ; Cold Storage Air Cooled Condenser ; Turn-key Cold Storage Solutions ; Cooling Tube Fin Cold Room
The rubber rollers of printing press machine play an important role in the printing process, but in actual production, many printing companies will soon need to replace the original rubber rollers. Due to insufficient cleaning and maintenance of the rubber rollers by most manufacturers, the original rubber rollers are prematurely aged, causing printing failures and cost loss.
Ink roller
Ink roller refers to the rubber roller in all ink supply systems. The role of the ink roller is to quantify and uniformly transfer the printing ink to the printing plate, which can be divided into three types: ink, ink transfer, and printing plate.
The ink is used to extract a fixed amount of ink from the ink fountain and then transfer it to the transfer roller. The ink transfer roller receives these inks and distributes them evenly to form a uniform ink film. It is then passed to the platen roller, which is responsible for distributing the incoming ink on the printing plate. At this point, the task of the ink roller is completed.
In offset presses, rubber rollers and hard rollers are always spaced apart to form a soft-hard alternate arrangement. This arrangement is more conducive to ink transfer and uniform distribution. The function of the ink roller can further strengthen the axial distribution of the ink. When it is working, it also rotates in the axial direction and performs a series of axial translation. Therefore, it is called an ink roller.
The ink roller is used to transfer ink, so the rubber must be ink-friendly. Due to the long-term contact between the adhesive layer and the ink, it must have certain resistance to ink corrosion. At the same time, the speed of the offset press is very high, and the speed of the ink roller is also very high, which causes serious heat generation of the adhesive layer, thereby accelerating the aging of the rubber. Therefore, to make the rubber roller durable, the requirements on the rubber material are also very high.
Water roller
The water roller is a rubber roller in the water supply system, similar to the ink roller, and its function is to uniformly transport water to the printing plate. Water rollers also have water, water, and plate. At present, there are two types of water supply methods for water rollers. One is the continuous water supply method. The water supply amount is achieved by adjusting the speed of the bucket roller, which is suitable for high-speed printing. The other is intermittent. The platen roller is covered with a fleece cover, and the water roller swings back and forth to supply water.
The water roller is used to transfer water, so it must be hydrophilic and resistant to water corrosion, and its hardness is usually lower than that of the ink roller.Ink rollers and water rollers of offset printing presses traditionally use nitrile rubber, but they have their own emphasis on the formula of rubber compounds. Of course, other materials can also be used as long as they meet the requirements for use.
Causes of Rubber Roller Wear
1. Improper pressure adjustment of the ink roller will cause wear of the ink roller, especially if the pressure is heavy on one side and light on the other, it will easily cause damage to the rubber roller.
2. Forgetting to close the handles on both ends of the water bucket roller will cause the colloid of the metering roller to tear and damage. If one end is not closed or the other end is not in place, the metering roller and the plate-type water roller will be worn.
3. During the plate loading process, the PS plate is not installed properly, the bite of the PS plate and the tension screw at the end of the plate are not tightened. The PS plate will wear out the rubber roller due to the untensioned part and the protruding protrusions; The plate is too tight or the top plate is too powerful, which causes the plate to deform or rupture and damage the ink roller, especially because the plate water roller has low rubber hardness and its damage is also * obvious.
4. In the printing process, when printing a long order, the running conditions of the two ends and the middle are different, which will cause the two ends of the ink roller to wear.
5. Poorly printed film. The powder and sand particles falling off the film will cause the ink roller and copper roller to wear.
6. Use a sharp tool to draw a gauge line or make other marks on the printing plate, resulting in damage to the ink roller.
7. During the printing process, due to the poor local water quality and high hardness, and the printing plant did not install a proper water treatment device, the surface of the ink roller accumulated calcium compounds, which increased the rubber hardness and increased friction. This problem not only causes wear of the ink roller, but also causes serious print quality problems.
8. The ink roller is not regularly maintained and recycled.
9. The ink on the surface of the metering roller will not cause abrasion if it is not washed for a long time.
10. Special processes, such as printing gold and silver cardboard, stickers or films, require special inks and special additives, which will accelerate the cracking and aging of rubber rollers.
11. The roughness of ink particles, especially the roughness of UV ink, has a direct impact on the wear of rubber rollers.
12. The speed of wear of rubber rollers in different parts is different. Such as the ink transfer roller, because its action is stationary → high speed → stationary continuously reciprocating, its wear degree is faster than ordinary.
13. When the rubber roller is stationary for a long time when it is stopped for a long time, the rubber diameter of the rubber roller is uneven, and the rotation and deformation of the rubber roller are different, which exacerbates the wear of the rubber roller.
14. The temperature control of the working environment is not good. It exceeds the physical properties of the rubber roller and increases the wear of the rubber roller.
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