Lubrication and Reliability Handbook 2010 Part 6 potx

b Air or hydraulic pump: i check air or hydraulic circuit, ii ascertain that correct operating pressure is available.. RESERVOIR a Check that the lubricant supplied for filling the reser

Figure 24.2 Nomogram for determination of pipe bore Figure 24.3 Viscosity correction factor, X, for mineral oils only

A guide to piping design

Figure 24.4 Pressure losses per unit length in pipes (Re < 2000)

A24 A guide to piping design

A24.6

Figure 24.5 Nomogram for Reynolds No Re = ␳Vd

␩ = Vd

␯

A guide to piping design

Table 24.4 Loss coefficients

Figure 24.6 Correction factor Z for flow through curved capillary tubes of bore diameter d and coil diameter D

A25 Selection of warning and protection devices

A25.1

Satisfactory operation of a centralised recirculatory lubrication system requires adequate control and instrumentation

to ensure continuous delivery of the correct volume of clean oil at the design pressure and temperature

Figure 25.1 A basic lubrication system complete with warning and protection devices

Table 25.1 The function of each major system component and the device required to provide the

information or control necessary to maintain that function

A25 Selection of warning and protection devices

Table 25.1 The function of each major system component and the device required to provide the

information or control necessary to maintain that function (continued)

Table 25.2 Some protective devices available with guidance on their selection and installation

A25 Selection of warning and protection devices

A25.3

Table 25.2 Some protective devices available with guidance on their selection and installation (continued)

A26 Commissioning lubrication systems

TOTAL-LOSS SYSTEMS

Commissioning procedure

1 Check pumping unit

2 Fill and bleed system Note: it is not normally considered

practicable to flush a total-loss system

3 Check and set operating pressures

4 Test-run and adjust

No special equipment is required to carry out the above

procedure but spare pressure gauges should be available

for checking system pressures

Pumping unit

PRIME MOVER

For systems other than those manually operated, check

for correct operation of prime mover, as follows

(a) Mechanically operated pump – check mechanical

linkage or cam

(b) Air or hydraulic pump:

(i) check air or hydraulic circuit,

(ii) ascertain that correct operating pressure is

available

(c) Motor-operated pump:

(i) check for correct current characteristics,

(ii) check electrical connections,

(iii) check electrical circuits

PUMP

(a) If pump is unidirectional, check for correct direction

of rotation

(b) If a gearbox is incorporated, check and fill with

correct grade of lubricant

CONTROLS

Check for correct operation of control circuits if

incorporated in the system, i.e timeclock

RESERVOIR

(a) Check that the lubricant supplied for filling the

reservoir is the correct type and grade specified for

the application concerned

(b) If the design of the reservoir permits, it should be

filled by means of a transfer pump through a bottom

fill connection via a sealed circuit

(c) In the case of grease, it is often an advantage first to

introduce a small quantity of oil to assist initial priming

Filling of system

SUPPLY LINES These are filled direct from the pumping unit or by the transfer pump, after first blowing the lines through with compressed air

In the case of direct-feed systems, leave connections to the bearings open and pump lubricant through until clean air-free lubricant is expelled

In the case of systems incorporating metering valves, leave end-plugs or connections to these valves and any other ‘dead-end’ points in the system open until lubri-cant is purged through

With two-line systems, fill each line independently, one being completely filled before switching to the second line via the changeover valve incorporated in this type of system

SECONDARY LINES (Systems incorporating metering

or dividing valves) Once the main line(s) is/are filled, secure all open ends and after prefilling the secondary lines connect the metering valves to the bearings

System-operating pressures

PUMP PRESSURE This is normally determined by the pressure losses in the system plus back pressure in the bearings

Systems are designed on this basis within the limits of the pressure capability of the pump

Check that the pump develops sufficient pressure to overcome bearing back pressure either directly or through the metering valves

In the case of two-line type systems, with metering valves operating ‘off’ pressurised supply line(s), pres-sures should be checked and set to ensure positive operation of all the metering valves

Figure 26.1 Schematic diagrams of typical total-loss systems – lubricant is discharged to points of

application and not recovered

A26 Commissioning lubrication systems

A26.2

Running tests and adjustments

SYSTEM OPERATION

Operate system until lubricant is seen to be discharging

at all bearings If systems incorporate metering valves,

each valve should be individually inspected for correct

operation

ADJUSTMENT

In the case of direct-feed systems, adjust as necessary the

discharge(s) from the pump and, in the case of systems

operating from a pressure line, adjust the discharge from

the metering valves

RELIEF OR BYPASS VALVE

Check that relief or bypass valve holds at normal

system-operating pressure and that it will open at the specified

relief pressure

CONTROLS

Where adjustable electrical controls are incorporated,

e.g timeclock, these should be set as specified

ALARM

Electrical or mechanical alarms should be tested by

simulating system faults and checking that the

appro-priate alarm functions Set alarms as specified

Fault finding

Action recommended in the event of trouble is best

determined by reference to a simple fault finding chart

as illustrated in Table 26.2

CIRCULATION SYSTEMS

Commissioning procedure

1 Flush system Note: circulation systems must be

thor-oughly flushed through to remove foreign solids

2 Check main items of equipment

3 Test-run and adjust

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

Flushing

1 Use the same type of oil as for the final fill or flushing

oil as recommended by the lubricant supplier

2 Before commencing flushing, bypass or isolate

bear-ings or equipment which could be damaged by

loosened abrasive matter

3 Heat oil to 60–70°C and continue to circulate until the minimum specified design pressure drop across the filter is achieved over an eight-hour period

4 During flushing, tap pipes and flanges and alternate oil on an eight-hour heating and cooling cycle

5 After flushing drain oil, clean reservoir, filters, etc

6 Re-connect bearings and equipment previously iso-lated and refill system with running charge of oil

Main items of equipment

RESERVOIR

(a) Check reservoir is at least two-thirds full.

(b) Check oil is the type and grade specified.

(c) Where heating is incorporated, set

temperature-regulating instruments as specified and bring heat-ing into operation at least four hours prior to commencement of commissioning

ISOLATING AND CONTROL VALVES

(a) Where fitted, the following valves must initially be

left open: main suction; pump(s) isolation; filter isolation; cooler isolation; pressure-regulator bypass

(b) Where fitted, the following valves must initially be

closed: low suction; filter bypass; cooler bypass; pressure-regulator isolation; pressure-vessel isola-tion

(c) For initial test of items of equipment, isolate as

required

MOTOR-DRIVEN PUMP(S)

(a) Where fitted, check coupling alignment.

(b) Check for correct current characteristics.

(c) Check electrical circuits.

(d) Check for correct direction of rotation.

PUMP RELIEF VALVE Note setting of pump relief valve, then release spring

to its fullest extent, run pump motor in short bursts and check system for leaks

Reset relief valve to original position

CENTRIFUGE Where a centrifuge is incorporated in the system, this

is normally commissioned by the manufacturer’s engi-neer, but it should be checked that it is set for

‘clarification’ or ‘purification’ as specified

FILTER

(a) Basket and cartridge type – check for cleanliness (b) Edge type (manually operated) – rotate several

times to check operation

(c) Edge type (motorised) – check rotation and verify

correct operation

(d) Where differential pressure gauges or switches are

fitted, simulate blocked filter condition and set accordingly

Figure 26.2 Schematic diagram of typical

oil-circulation system Oil is discharged to points of

application, returned and re-circulated.

A26 Commissioning lubrication systems

PRESSURE VESSEL

(a) Check to ensure safety relief valve functions correctly.

(b) Make sure there are no leaks in air piping.

PRESSURE-REGULATING VALVE

(a) Diaphragm-operated type – with pump motor

swit-ched on, set pressure-regulating valve by opening

isolation valves and diaphragm control valve and

slowly closing bypass valve

Adjust initially to system-pressure requirements as

specified

(b) Spring-pattern type – set valve initially to

system-pressure requirements as specified

COOLER

Check water supply is available as specified

Running tests and adjustments

(1) Run pump(s) check output at points of application, and finally adjust pressure-regulating valve to suit operating requirements

(2) Where fitted, set pressure and flow switches as speci-fied in conjunction with operating requirements (3) Items incorporating an alarm failure warning should

be tested separately by simulating the appropriate alarm condition

Fault finding

Action in the event of trouble is best determined by reference to a simple fault finding chart illustrated in Table 26.1

FAULT FINDING

Table 26.1 Fault finding – circulation systems

A26 Commissioning lubrication systems

A26.4

Table 26.2 Fault finding – total-loss systems

A27 Running-in procedures

1 GENERAL REQUIREMENTS

Running-in to achieve micro-conformity can be monitored by surface finish measurement and analysis before and after the running-in process Surface finish criteria such as Ra(CLA) and bearing area curves are likely to be the best The comparison of these parameters with subsequent reliability data can guide manufacturers on any improvements needed

in surface finish and in running-in procedures No generally applicable rule of thumb can be given

2 RELATIVE REQUIREMENTS

The running-in requirement of assembled machinery is that of its most critical part The list below rates the ease of running-in of common tribological contacts

Figure 27.1 Profilometer traces (vertical magnification 5 times the horizontal)

A27 Running-in procedures

A27.2

3 RUNNING-IN OF INTERNAL COMBUSTION ENGINES

The most effective running-in schedule for new and

rebuilt engines depends to a large extent on the

individual design of engine and materials used It is

therefore important to follow the maker’s

recommenda-tions In the absence of a specific schedule the following

practice is recommended

Running-in on dynamometer

Running-in a road vehicle

Monitoring running-in

The following observations provide a guide as to the completeness of the running-in process:

A27 Running-in procedures

In research and development the following additional

observations provide valuable guidance:

Running-in accelerators

Running-in accelerators should only be used in consulta-tion with the engine maker Improper use can cause serious damage

Ferrography

Ferrography is a technique of passing a diluted sample of the lubricating oil over a magnet to extract ferrous particles It has found useful application in running-in studies aimed at shortening running-in of production engines and so making possible large cost savings The principle is to examine suitably diluted samples of engine oil to obtain, during the process of running-in, a measure of the content of large (L) and small (S) particles Over a large number of dynamometer tests on new production engines a trend of ‘Wear Severity Index’ (Is= L2– S2) with time may be discerned which allows comparison to be made between the effectiveness of running-in schedules

Figure 27.2(a) Un-run cylinder liner ⴛ140

Figure 27.2(b) Run-in cylinder liner ⴛ 140

A27 Running-in procedures

A27.4

4 RUNNING-IN OF GEARS

Procedures

It is not feasible to lay down any generally applicable

running-in procedure The following guiding principles

should be applied in particular cases:

Materials and lubricants

See also Sections A23, 24, 25 Running-in has been found

to be influenced by materials and lubricants broadly as

follows:

Observing progress of running-in

Figure 27.3 Examples of oil temperature variation during early life of hypoid axles

A27 Running-in procedures

5 RUNNING-IN OF PLAIN BEARINGS

Special running-in requirements

Procedure

6 RUNNING-IN OF SEALS

Rubbing seals, both moulded and compression, undergo

a bedding-in process No general recommendations can

be given but the following table summarises experience:

Figure 27.4 Typical effects of running-in on

warm-up of plain journal bearings

A28 Industrial plant environmental data

A28.1

TEMPERATURE

The main problems in industry arise with radiation from hot processes Typical examples of heat sources are as follows:

Table 28.1 Effects of atmospheric conditions

Table 28.2 Temperatures of some industrial processes

A28 Industrial plant environmental data

These graphs are based on laboratory and field

measurements where a blackened metallic body was used

with convective cooling Figure 28.2 is for a source area

of 20 in2 Increasing the source area will reduce the slope

of the graph towards that of Figure 28.1 which

approx-imates to an infinite plane source The multiplicity of

variables associated with radiative heat transfer precludes

a simple accurate calculation of the temperature any body will reach when placed near any source of heat However, the graphs will indicate if temperature is likely

to be a problem The heat generated by the body itself must, of course, not be overlooked

HUMIDITY

Relative humidities above 45% often lead to condensation problems

Figure 28.1 Applicable to furnace walls from 150

to 300°C

Figure 28.2 Applicable to sources from 300 to 1400°C

Table 28.3 Typical values of relative humidity and dry bulb temperatures for working areas found in

industry

A28 Industrial plant environmental data

A28.3

CORROSIVE ATMOSPHERES

DUST

Table 28.4 Industries and processes with which corrosive atmospheres are often associated

Table 28.5 Industries in which dust problems may be excessive

Table 28.6 Particle sizes of common materials as a guide to the specification of seals and air filters

A29 High pressure and vacuum

PRESSURE

Effect of pressure on lubricants

Figure 29.1 Effect of pressure on viscosity of HVI

paraffinic oils

Figure 29.2 Effect of pressure on viscosity of LVI naphthenic oils