## Circulation Systems Commissioning procedure

Mote circulation systems must be thoroughly flushed through to remove foreign solids. 2 Check main items of equipment. No special equipment is required to carry out the above but spare pressure gauges for checking system pressures, etc., and flexible hoses for bypassing items of equipment, should be available. Figure 19.2 Schematic diagram of typical oil-circulation system. Oil is discharged to points of application, returned and re-circulated Figure 19.2 Schematic diagram of...

## Basic Mechanisms

Fretting occurs where two contacting surfaces, often nominally at rest, undergo minute oscillatory tangential relative motion, which is known as 'slip'. It may manifest itself by debris oozing from the contact, particularly if the contact is lubricated with oil. Colour of debris red on iron and steel, black on On inspection the fretted surfaces show shallow pits filled and surrounded with debris. Where the debris can escape from the contact, loss of fit may eventually result. If the debris is...

## Selection of journal bearingsA2

Selection of journal bearings with continuous rotation for special environmental conditions Rubbing plain bearings (non-metallic) Good up to the temperature limit of material Good to temperature limit of lubricant Externally pressurised plain bearings Watch effect of thermal expansion on fits Selection of journal bearings with continuous rotation for special performance requirements Rubbing plain bearings (non-melallic) Usually requires a circulation system Externally pressurised plain bearings...

## To Find The Deflection And Slope Of A Stepped Shaft

(1) Find all the loading and bearing forces acting on the shaft. (2) Set up a z axis along the axis of the shaft, and right-angle axes x and j perpendicular to this axis. Choose the orientation of x, and y to coincide with one direction in which the shaft deflection is wanted. (3) Resolve all the forces into components along each of the axies. (4) Consider the shaft split into sections, each section containing one step of the shaft (i.e. each section consists of a piece of shaft of constant...

## Compostion And Properties

The stress levels in rolling bearings limit the choice of materials to those with a high yield and high creep strength. In addition, there are a number of other important considerations in the selection of suitable materials, including the following High endurance under fatigue loading Steels have gained the widest acceptance as rolling contact materials as they represent the best compromise amongst the requirements and also because of economic considerations. The through hardening steels are...

## Rotary Mechanical Seals

Table 6.1 Common failure mechanisms of mechanical seals Likely symptoms High High High leakage friction wear OPERATING CONDITIONS Speed of sliding high Speed of sliding low Appreciable vibration present X XXX Excessive friclional heating, X Thermal stress cracking of the X X X X Thermal distortion of seal tion, solid contact X X Face separation unstable Low pressure differential High pressure differential Sterilisation or cleaning cycle used Exposure to sunlight, ozone, radiation (X) Fluid...

## Visual Examination Of Used Lubricating

1 Take sample of circulating oil in clean glass bottle (50-100 ml). 2 If dirty or opaque, stand for 1 h, preferably at 60 C (an office radiator provides a convenient source of heat). System withoutfilter1-1' or centrifuge Clear oil with separated water layer Run off water (and sludge) from drain'3' Check centrifuge '6' if centrifuge fails to clear change oil Notes (1) The term filter is restricted to units able to remove particles less than 50 fim coarse strainers, which are frequently fitted...

## Calculation of contact Hertzian stress

It is now necessary to calculate the Hertzian stresses between the cam and tappet. Most tappets and cams can be classified into one of the forms shown in Figure 10.4. The appropriate formulae for the Hertzian stress are listed below. The following symbols and units are used W load between cam and tappet (N) b width of cam (mm) Rc cam radius of curvature at point under consideration (mm) Rfi tappet radius of curvature in plane of cam (mm) Rjo tappet radius of curvature at right angles to plane...

## Methods Of Selection

Simple bearings, Small numbers, low duty, easy access Small heat removal, difficult access, large numbers Ring or disc systems. Oil circulates reservoir total loss or limited circulation Plain bearings, low duty. Light loaded mechanisms Bearings packed on assembly. Refilling impossible without stripping Rolling bearings, some plastic bushings Feed pipes brought to manifold or pump Reasonable numbers. lna< (I's ihle bearings Grease pump feed to bearing and sets of bearings from automatic pump...

## Materials For Flexure Hinges And Torsion Suspensions

Flexure hinges and torsion suspensions are devices which connect or transmit load between two components while allowing limited relative movement between them by deflecting elastically. Selection of the most suitable material from which to make the elastic member will depend on the various requirements of the application and their relative importance. Common application requirements and the corresponding desired properties of the elastic member are listed in Table 25.1. Table 25.1 Important...

## Wear resistant materials

The following tables give more detailed information on the materials listed in Table 18.3 with examples of some typical applications in which they have been used successfully. When selecting the materials for other applications, it is important to identify the wear mechanism involved as this is a major factor in the choice of an optimum material. Further guidance on this is given in Table 18.1. Heat-treatable. Can be lined with glass, rubber, enamels Many engineering parts, crusher cones,...

## A7 Grease wick and drip fed journal bearings

Table 7.3 Guidance on the choice of lubricant grade Table 7.3 Guidance on the choice of lubricant grade Up to 60 C lt 0.5 m s gt 0.5 m s 60 C to 130 C lt 0.5 m s gt 0.5 m s Lithium hydroxystearate based grease with high V.I. mineral oil and antioxidant additives Good quality high V.I. crankcase or hydraulic oil with antioxidant additives fatty oils for drip-fed bearings Best quality fully inhibited mineral oil, synthetic oil designed for high temperatures, halogenated silicone oil Notes for...