Types of Greases

A sealant, such as Apiezon W, is a good example of a material that was designed for an extremely limited application. Apiezon W is a hard black wax that needs to be heated to 80°-90°C before it is soft enough to apply to the members you wish to join. At room temperatures it is hard and has no lubrication abilities whatsoever and is therefore not usable for a stopcock. It has a relatively high vapor pressure (10 3 torr), so it cannot be used for most vacuum work. However, at temperatures of about 100° to 150°C, it becomes very thin like hot honey and can easily be applied to joint members. Therefore, if you have a standard taper joint that will not be in a high-heat or ultrahigh-vacuum environment, there is no need to separate often, and you don t want it to accidentally separate, Apiezon W is the type of sealant you need. 

Apiezon L Joints where it s used will be in applications of very low vapor pressure (10 10 to 10 torr). Not intended for stopcock use. Moderately expensive (= 130/50 gm). 

Apiezon M Similar to Apiazon L for general applications, but cheaper (= 79/50 g). Higher vapor pressure (10 7 to 10 8 torr) than Apiazon L. Not intended for stopcock use. 

Apiezon N Stopcocks because of special slippery properties. Its price (= 135/25 g). 

Apiezon T Joints or stopcocks used in high temperature. Its price (= 130/25 g). 

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There are hundreds of types of greases available, and machineiy manufacturers usually provide a guidehne for the greases to be used on their equipment. There are also highly specialized greases, such as the ones that can be used in food processing machineiy, or the ones used in nuclear power stations. 

To have a minimum tracking temperature (at which the grease may start conducting) of 200°C. Apply this grease swiftly after the surface cleaning to avoid a fresh oxidation. The following are a few types of greases ... 

Leakage A burette must be tested for any sort of leakage before putting it into operation. Teflon stopcocks are usually adjusted by a knurled nut for perfect use. Glass stopcocks may require a small quantity of a special type of grease or lubricant to allow both ease of operation and to check leakage. 

Oil on the dial is indicative of oil migration from the pumping system. Improper and/or inadequate traps or user error are to blame for this problem. Clean with an appropriate solvent for the type of grease found. Rinse and dry the gauge before reinstalling back onto the line. Methanol is a good final rinse as it dries quickly and cleanly. 

Aldehydes are formally named by changing the final -e of the name of the alkane with the same number of carbon atoms to the suffix -al. Thus, the formal name of the compound represented above is methanal, based on the one-carbon alkane methane. Methanal is commonly called formaldehyde. A water solution of formaldehyde was used in the past to preserve biological specimens. However, formaldehyde s use has been restricted in recent years because evidence shows it may cause cancer. Industrially, large quantities of formaldehyde are reacted with urea to manufacture a type of grease-resist-ant, hard plastic used to make buttons, appliance and automotive parts, and electrical outlets, as well as the glue that holds the layers of plywood together. 

There are a variety of different types of grease that are produced with specific functions in mind. Therefore, properties vary with the method of preparation as well as with the metal included in the grease. 

Lithium soap grease is normally smooth in appearance but may exhibit a grain structure. This type of grease is resistant to water and to the highest... 

Other important lithium compounds include lithium chloride, which has significant water-absorbing power. This allows for the use of lithium chloride in the manufacture of air conditioning units. Another compound, lithium stearate, is the product of a reaction between stearic acid and lithium hydroxide. This compound is useful as a type of grease able to withstand extremely low temperatures. 

A mixture of oil and graphite is better than pure graphite for use at higher operating temperatures. Other substances used in vertical thermowells are glycerine, napthalene, oils and various types of greases and proprietary heat transfer fluids. 

Type of grease Maximum operating temp. ( C) Composition or manufacturer Application... 

Requires less effort than NPEOs for equivalent cleaning Provides equivalent detergency at lower concentrations Emulsifies all types of grease, carbon and soil Superior engine degreaser Low glycol content... 

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