Plastics for cryogenic and high temperature applications

Because polymer technology has experienced a major evolution, plastic materials have the ability to resist and perform in extreme conditions in relation to the temperature. All the high temperature polymers must include specific characteristics in order to lift up to the manufacturers’ requirements and standards. These characteristics have the goal to control the behavior of plastics in environments that present hotter and colder temperatures than ever anticipated and include creep resistance, exceptional wear properties, excellent resistance to hot water, thermal stability, high and low thermal conductivity, good sealing traits.

Characteristics of plastics at extreme temperatures

Plastics that present high resistance to extreme temperatures are very useful for various applications that demand superior mechanical properties and involve speeds or loads. If the plastic encounters moving parts, it must prove to wear resistance and low friction while withstanding various chemicals. The creep resistance represents a trait that helps to maintain tight seals while low stiffness is essential for mating surfaces. Moreover, plastics are perfect for electrical insulation. The multitude of polymers available provides irreproachable fire resistance and dielectric strength. Of course, manufacturers have performed multiple tests in order to meet the highest electrical standards. Because plastics offer low thermal conductivity at extremely cold temperatures, they can be used as part of physics research equipment.

Material selection for high temperatures application

Considering that the high temperature poyurethane will be used in high temperatures environments, manufacturers must analyze data concerning the material properties. The main factors they always keep in mind are degradation, thermal expansion, strength and modulus, stress relaxation and creep. Manufacturers must assess and control thermal degradation of polymers, which might degrade after a long period when facing high temperature environments. In comparison with metals, plastics materials are more vulnerable when it comes to thermal expansion meaning that they change in the area, volume and shape in response to drastic temperature change. That being said, manufacturers must ensure that dimensional changes between metal parts and plastic parts do not lead to a malfunction. When exposed to extremely hot temperatures, plastic material become soft, this means that they lose strength and modulus. For this reason, the importance of examining mechanical properties cannot be neglected. Apart from losing strength and modulus at high temperatures, plastics present higher stress relaxation and creep strain, factors that need to be taken into account during the production process.

Material selection for cryogenic applications

Plastic materials are also exposed to cryogenic temperatures, not only in extremely hot environments. When producing plastic components for this type of situation, manufacturers ensure that the plastics present a low thermal expansion and ductile behavior. The adequate thermal conductivity is imperative when dealing with heat transfer. Plastics wear differently when in cold environments so if they must be produced for bearing, choosing a material with low friction and excellent wear properties at cryogenic temperatures becomes essential. In certain industries including aircraft and spacecraft, the temperature level varies. This means that plastics must function perfectly throughout the respective temperature range. Obviously, various considerations appear when using plastics at different temperatures.

Everything you need to know about gear pumps types

Gear pumps are the most common positive displacement devices. They are used in almost every industry in which dense liquid transfer is required. There are two major types of gear pumps internal and external. Both these types are explained as under:

Internal gear pumps

Internal gear pumps have two types of gears. One is known as drive and the other is known as an idler. Thin and thick liquids are pumped at the same speed using this pump. With a large density range there are many applications which use internal gear pumps. This type of pump also has a high range of temperature and the variation is also great. The end clearance has single point due to which the temperature alteration is handled. The internal pump has clearance which can also be altered. The clearance factor is one which allows the internal gear pumps to work with high efficiency. There are several other factors which are associated with clearance. The pumping and density of liquids are made more efficient if the clearance value is altered.

Advantages of internal pumps

There are several advantages which are associated with internal gear pumps. Some of these are as follows:

  • The internal gear pumps are self-priming.
  • Such pumps can also run dry for small intervals
  • The rotation is multi-dimensional which means that internal gear pumps can also be used for other purposes.
  • The internal pumps are very reliable and are easy to install. The maintenance cost is also close to zero which means that over cost reduction is likely to increase of this pump is used.
  • These pumps require no technicalities for operation. Even a novice user can be deployed to operate these pumps as their structure is too easy to understand.

External gear pumps

As compared to internal gear pumps the external ones are applied in a large number of industries. The main applications of external pumps are oil stations, gas pumps and large food industries. There are many types of external gear pumps. Some of these are as follows:

  • Spur
  • Helical
  • Herringbone

The spur type pumps offer rough passage of fluids as compared to helical and herringbone types. Mostly herringbone types are used as they have less sound and the smooth passage is allowed. Another astonishing fact is that the large external pumps operate slowly as compared to small pumps. The shafts of external gear pump also allow support from both ends. They are ideal as they work in line with the hydraulic mechanics. Precision is another factor which external pumps offer. The internal tight clearances allow preserving precision factor.  Operators enjoy full control over fluid transfer which makes it most used the device in many industries.

Advantages of external gear pumps

  • These devices have high speed and work very swiftly
  • The less sound make them ideal for all environments
  • The design can be customized and a wide range of fluids can be pumped
  • The pressure as compared to all other types is high and offers precise measurement of liquids