Vibration Analysis Focusing on the Spectrum (Remastered)

Summary

本视频脚本为观众提供了一次关于振动分析的深入讨论。主讲人介绍了振动监测的基本理论，包括如何测量和分析机器的振动信号，以及如何通过振动的频率和幅度来诊断机器的健康状况。通过案例研究，展示了振动分析在监测和预测机械故障方面的实际应用，强调了识别机器故障信号的重要性，并解释了如何利用这些信号来提高设备的可靠性和性能。

Takeaways

• 📈 振动分析是一种监测机器健康状态的有效工具，通过测量振动信号来识别机器中的潜在问题。
• 🔍 机器通过振动信号而非语言与我们沟通，振动监测可以帮助我们理解机器的运行状况。
• 📊 振动监测可以测量信号的高度和持续时间，从而识别机器中具体部件的问题。
• 🔨 机器的振动可能与电气、机械或过程相关，振动监测能够区分这些不同的信号来源。
• 🌡️ 振动测量需要考虑机器的力和运动，包括机器的对齐情况和振动速率。
• 🔄 机器的不同部件，如叶片、螺丝压缩机或齿轮，会产生独特的“心跳”模式，即振动信号。
• 📉 振动信号的波形复杂，但可以通过傅里叶变换等数学方法简化为频率谱，便于分析。
• 📌 频率谱中的峰值可以指示机器问题的性质，如不平衡、轴承损坏或其他机械故障。
• ⚙️ 振动监测不仅关注振动的幅度，更关注幅度的变化趋势，以识别机器状态的变化。
• 🛠️ 通过案例研究，展示了振动监测在实际应用中如何帮助诊断和修复机器故障。
• 🔧 振动分析需要结合专业知识和经验，以正确解释数据并采取适当的维护措施。

Q & A

振动分析是什么，它在机器监测中扮演什么角色？

振动分析是一种监测和分析机器振动信号的技术，用于评估机器的运行状况和预测潜在故障。在机器监测中，振动分析帮助我们通过测量和分析振动信号来理解机器的“语言”，从而提前发现问题并采取措施。

为什么机器会产生振动信号？

机器在运行过程中，由于机械、电气或过程等方面的问题，会产生振动。例如，机器的不对中、轴承损坏或者叶片不平衡等问题都会导致振动，这些振动信号可以被传感器捕捉并分析，以确定机器的健康状况。

振动监测中测量的信号有哪些特点？

振动监测中测量的信号特点包括信号的高度、持续时间以及频率。信号的高度可以反映振动的强度，持续时间可以帮助我们理解每个事件的长短，而频率则可以揭示机器中哪个部件可能存在问题。

什么是机器的“心跳”信号，它如何帮助我们识别问题？

机器的“心跳”信号是指机器在正常或异常运行状态下产生的特定频率的振动模式。通过分析这些模式，我们可以识别机器的特定部件是否存在问题，例如齿轮的缺陷、轴承的损坏等，从而实现对机器健康状况的跟踪和诊断。

为什么需要考虑机器的对中和运动对振动监测的影响？

机器的对中和运动直接影响振动信号的特性。如果机器不对中，会导致额外的力和振动，可能会损坏轴和轴承。了解机器的运动和振动速率有助于我们更准确地诊断问题，比如通过分析振动的频率和幅度来确定故障的类型和位置。

在振动分析中，频率分析的作用是什么？

频率分析是将复杂的时间波形信号转换为频率域，以揭示信号中不同频率成分的强度。这有助于识别和量化机器中的特定问题，如不平衡、轴承损坏等，因为这些问题会在特定的频率上产生特征峰值。

什么是振动信号中的谐波和边带，它们如何帮助诊断问题？

谐波是基本频率的整数倍频率，而边带是位于中心频率两侧的等间隔的频率峰值。它们通常与机器中的非线性问题或松动部件有关。通过分析谐波和边带的分布和间距，可以提供关于机器故障性质和位置的重要线索。

为什么振动监测需要定期进行，而不仅仅是在机器启动时？

定期进行振动监测可以追踪机器的运行趋势和健康状况的变化。机器可能在运行过程中逐渐出现问题，如磨损或损坏，这些问题可能不会立即显现，但通过定期监测可以及时发现并采取措施，避免更严重的故障发生。

在实际案例中，振动监测如何帮助识别和解决轴承问题？

在实际案例中，通过监测轴承的振动信号，可以发现异常的频率峰值，如谐波和边带，这些特征表明轴承可能存在问题。通过进一步分析这些峰值的频率和间距，可以确定故障的具体类型，如内圈、外圈或滚动元件的损坏，并据此进行维修或更换。

振动监测在旋转设备上的应用有哪些局限性？

虽然振动监测是一种强大的工具，但它也有局限性。例如，它可能无法检测到所有类型的故障，特别是那些不产生显著振动信号的问题。此外，振动监测需要专业知识来正确解释数据，而且可能需要与其他监测技术结合使用，以获得更全面的机器健康状况评估。

Outlines

00:00

🔍 振动分析基础与监测理论

本段介绍了振动分析的基本概念，包括振动监测的目的和基本理论。振动分析可以帮助我们通过测量机器发出的信号来了解其健康状况。机器的信号不是用语言，而是通过振动来表达。振动监测可以测量信号的高度和事件持续时间，以识别机器中有问题的特定组件。此外，还讨论了不同类型的振动源，包括电气、机械和过程振动，并强调了正确准备和放置传感器的重要性。

05:01

📊 振动信号的测量与分析

这段内容深入探讨了如何通过振动监测来测量和分析机器的信号。解释了机器的'心跳'如何反映其健康状况，以及如何通过监测这些心跳来跟踪机器的状态。讨论了不同类型的机器组件，如叶片、螺杆压缩机和齿轮，它们如何产生独特的心跳模式。强调了监测这些模式变化的重要性，以及如何通过频率分析来识别机器问题的性质，例如不平衡、冲击事件或轴承损坏。

10:02

🌐 振动信号的频率分析

本段讲述了如何将复杂的振动信号转换为更易于分析的频率谱。介绍了通过数学方法将时域信号转换为频域信号的过程，以及如何通过频率谱来识别和诊断机器问题。解释了如何通过观察频率谱中的峰值来识别机器的特定问题，例如不平衡、轴承损坏或其他机械故障。还讨论了如何通过分析频率谱中的谐波和边带来进一步诊断问题。

15:04

🛠 振动监测的实际应用案例

这段内容通过实际案例展示了振动监测在工业应用中的重要性。描述了一个锤式磨机轴承的监测案例，说明了如何通过定期的振动测量来跟踪机器的冲击强度和频率变化。通过监测这些变化，可以及时发现问题并在必要时进行维修。案例还展示了如何通过频率谱分析来识别特定问题，例如轴承外圈故障，并采取相应的维修措施。

20:06

🔧 振动监测在大型驱动系统中的应用

本段讨论了振动监测在大型驱动系统中的应用，特别是在一个气体循环风扇的电机驱动案例中。描述了如何通过定期监测来识别和诊断问题，例如通过分析振动信号的频率谱来发现谐波和边带，这些特征表明了转子条问题。案例强调了高分辨率测量的重要性，以及如何通过分析数据来确定问题的根本原因，并采取适当的维修措施。

25:06

🔄 振动监测的总结与问题解答

最后一段对振动监测的重要性进行了总结，并强调了理解振动信号或'心跳'对于识别和解决问题至关重要。振动监测不仅可以帮助识别机器的多种缺陷，还可以通过分析信号来确定何时采取纠正措施。演讲者感谢听众的时间，并欢迎任何问题，显示了对主题的深入理解和对交流的开放态度。

Keywords

💡振动分析

振动分析是一种监测和诊断机器设备状态的技术，通过测量设备在运转过程中产生的振动信号，分析其频率和幅度等参数，以评估机器的健康状况。在视频中，振动分析是主题，用于讲解如何通过监测振动信号来识别机器故障。

💡信号

信号在振动分析中指的是机器运转时产生的振动波形，可以是电信号或机械振动等形式。视频中提到通过测量信号的高度和事件持续时间，可以理解机器中哪个部件出现问题。

💡故障诊断

故障诊断是指通过分析振动信号来确定机器故障的原因和位置。视频中通过振动监测来诊断机器故障，例如通过分析振动信号的频率和幅度变化来识别问题所在。

💡频率

频率是振动分析中描述振动发生次数的参数，通常以每分钟的周期数来衡量。视频中提到频率对于理解振动的来源至关重要，如不平衡或轴承问题会产生特定频率的振动。

💡振幅

振幅表示振动信号的大小或强度。在视频中，振幅的变化被用来识别机器问题，如振幅的增加可能指示机器存在不平衡或其他故障。

💡轴承

轴承是机器中常见的旋转部件，其状态直接影响机器的振动特性。视频中讨论了轴承问题如何产生特定的振动信号，如轴承损坏会产生非整数倍的转速频率。

💡不平衡

不平衡是指旋转部件的质量分布不均匀，导致机器运转时产生周期性的振动。视频中提到不平衡会在旋转速度的频率处产生振动峰值，是常见的故障类型之一。

💡冲击振动

冲击振动是由机器内部的冲击或碰撞引起的振动，如轴承损坏或齿轮啮合问题。视频中通过分析冲击振动的频率和幅度，可以识别机器内部的冲击问题。

💡频谱分析

频谱分析是一种将时域信号转换为频率域信号的技术，用于识别信号中的不同频率成分。视频中使用频谱分析来简化复杂的振动信号，并通过频率成分来诊断机器故障。

💡案例研究

案例研究是实际应用振动分析技术来诊断和解决机器故障的实例。视频中通过几个案例研究展示了振动分析在实际中的应用，如锤式磨粉机和离心风机的故障诊断。

Highlights

振动分析讨论会旨在提供振动监测的基础知识和视觉洞察。

机器通过振动信号而非语言与我们交流，振动监测可以帮助我们理解机器的健康状况。

振动监测可以测量信号的高度和持续时间，以识别机器中的问题部件。

机器的信号可能与电气、机械或过程振动有关，振动监测可以帮助区分这些问题。

振动监测时，机器的对齐、运动和振动速率是关键考虑因素。

机器的不同部件，如叶片、螺杆压缩机和齿轮，都有其独特的“心跳”模式。

通过监测机器的“心跳”，我们可以跟踪其健康状况并预测潜在问题。

振动分析中，振幅和频率的变化是识别机器问题的关键指标。

通过频谱分析，可以将复杂的时间波形转换为更易解读的频率谱。

频率谱中的峰值可以帮助我们识别机器中的缺陷，如不平衡、轴承问题或齿轮缺陷。

振动信号中的谐波和边带是识别机器问题的重要特征。

案例研究展示了如何通过振动监测数据识别并解决实际的机器问题。

通过长期趋势分析，可以观察到机器振动水平的变化并采取相应的维护措施。

振动监测不仅用于检测问题，还能帮助提高机器的可靠性和性能。

在分析振动数据时，理解机器的运动和振动特性对于诊断问题至关重要。

振动分析是一种有用的工具，可以补充高频方法，以识别旋转设备上的多种缺陷。

理解振动信号的“心跳”是识别问题原因并采取纠正措施的关键。

Transcripts

[Music]

okay and good afternoon everybody

welcome to this very short 30 minute

discussion on vibration analysis

hopefully it gives you a good taster and

a visual insight into vibration

monitoring and hopefully the end we'll

just talk about one or two case studies

so uh we're going to talk about some

theoretical points to start with very

basic hopefully

talk about the signals we measure and

indeed as i say um

some couple of case studies to talk

through so

talk our machines talk

they talk to us but maybe what they

don't speak is uh

english or spanish or german

obviously they speak vibration

when they're not healthy

you know be nice if they actually said

what was wrong with them but sadly

that's not the case

but what they do talk is signals

so with vibration monitoring we can

measure the signals we can measure the

height of the signal

and we can measure the distance the

how long each event takes to understand

which component in the machine is

problematic

so we can narrow it down to a specific

component within the rotating asset

here we have a sensor placed on the

machine the forms of liberation that we

measure at this particular location

could be

electrically related

they could be mechanically related to

different parts of the machine itself in

a mechanical context we'll talk about

those in a moment

and thirdly it could be a process

vibration so whenever we take a

vibration measurement to measure the

health and trying to track the health of

an asset

all of those different considerations

could be measured through the signal and

we can separate them out to understand

which part of the machine is it

processed is it electrical or is the

mechanical problem we're dealing with

i think a key point to think about with

preparations

around this machine i will measure those

forces obviously very exaggerated

but if the machine were misaligned like

this and it's bolted down

actually is trying to do this in real

operation and that's going to destroy

the shaft bearings the chassis and so

forth

so we have to think about the forces and

secondly think about the motion and

indeed the

the rate of the vibration the rate at

which it moves we'll look more in in a

moment about that different parts of the

machine will vibrate the heartbeat the

the heartbeat of the machine here if the

blades the way that liquid cuts through

the system is disturbed maybe the

causation force from

this the vibration signal we see will

produce a different heartbeat to what we

saw before

maybe the loops and screw compressor

there will be a certain number of uh

sorry screws here so we have various

screws on each

shaft there

both screws will produce a unique

heartbeat if there's four screws four

heartbeats per rotation

obviously much more detailed here maybe

but in simple terms each gear will have

a certain number of teeth

and this defect on one of the teeth or

all the teeth or some of the teeth

the heartbeat pattern will be distinctly

different again to what we saw before

where the machine was misaligned or

secondly we saw the loops or the blades

on the pump

so you can see there obviously you've

got a certain number of teeth on each

gear that will produce a certain number

of pulsations if it's 20 teeth on this

gear for example 20 pulsations per

rotation

so we can trend we can track that

particular heartbeat and measure the

health

maybe with an imbalance you know the

forces here are more radio again the

force is radial but it's more of

emotional force maybe in this context

with the heartbeat it could produce

another distinct pattern the shutter

speed produces a particular force

maybe in this situation we've got more

of a shock event or an impact event so

it's going to disturb the signal in a

slightly different way to what we've

seen before

maybe with a bearing

you know if if there's a damaged spot on

the bearing it's going to produce a

certain number of pulses impacts per

rotation maybe the next slide we can

count them the defect here is where that

red dot is at 12 o'clock one shot two

three four five six seven eight and a

bit

eight and a bit shocks per rotation not

seven not eight but eight point

something that's uniquely different

that's what we discussed before

maybe we have a defect here on the outer

race we're not going to count them but

again it's going to produce a unique

heartbeat that's different

i guess bringing it into a more complex

machine like a wind turbine we've got

you know a complex array of rotating

components within this system the hub

bearing the gears

the drive shafts for the uh

generator itself an epicycle gearbox

with gears that are traveling around but

each part of that

machine each component produces distinct

unit heartbeats and we can trend and we

can track those heartbeats

and you know assess the health of each

part of that machine

so how does it kind of work well

vibration is kind of a strange thing

people think vibration is going to shake

and everything's going to move quite

dramatically but maybe that's not the

case

if my machine were

out of balance

you know that would cause more uh

emotional force and i would touch the

machine i would feel it's vibrating no

problem obviously i need to quantify

that and measure that

but if i had a bearing problem

that's not actually going to cause the

machine to move and vibrate excessively

it's going to be more localized impacts

shocks

actually due to the bearing that might

be damaged

so that's a different heartbeat inside

maybe the rotor bars they've got a

different heartbeat kind of bring them

all together

you know and it kind of gets a bit

more complicated maybe that's a bit loud

sorry about that

but obviously the heartbeats combined

together we measure these heartbeats

distinctly with our vibration are at key

strategic measurement locations and we

can trend and track

each component within the machine

[Music]

okay

so just a little bit of

theoretical stuff here before we kind of

move forward with some signals and

understand how these heartbeats produce

themselves

and one of the key aspects of the story

with vibration condition monitoring

we're trending and tracking the health

and what's most important obviously is

we measure the amplitude

how good we have all the vibration is or

how large it might be because if our

machine has a problem

the aperture is important but the change

in amplitude is important as well

condition monitoring about looking for

change trend and track the health and

look for change

once that change occurs we can say the

vibration has changed due to what well

that's where we need to understand the

frequency the rate of the heartbeat

you know is it 25 pulses per rotation is

it six pulses per rotation or is it one

pulse per rotation

depending upon what's causing it to

vibrate so the frequency enables enables

us sorry to understand the nature of the

source of what's causing this thing to

vibrate the defect itself is it the

bearing is it the blades is it the

coupling and so forth

and then main understanding how a

machine might move

by understanding the motion would

actually provide us with more diagnostic

information to narrow down the problem

so if we take a look at the basic uh

initial

part of the signal we measure it's the

waveform forgive me

with this simulator here i can just

start this machine up and just bear with

me a moment

i can see that this shaft is being

displaced i've got a clock gauge to

visually show you what normally a

vibration sensor would do we might use a

sensor placed on the body of the bearing

it's measuring the the vibration within

that bearing

and just pop that clock gauge back on

again um so obviously if

my my shaft had a fan on it and there's

a heavy spot it's going to cause it to

vibrate at a frequency of once for

rotation due to the heavy spot

if the hairstyle gets related because

products building up on a fan blade

maybe then obviously what will happen is

the amplitude the level of the vibration

will grow and just be steady there i'm

going to weigh that bearing if i'm not

careful just wind that back a bit um

so we can see that the amplitude of the

signal now is grown due to a heavier

mass on the actual fan

maybe that's that's mounted on that

particular shaft

so that's good if the speed changes

if the speed changes then obviously

behind the signal the waves get closer

together so the speed increases but it

takes less time to do one full rotation

less time

so one thing that's very important about

vibration is that we that we measure and

we correlate speed with the signals and

with statistically that's normally quite

a simple task to do so

um

that's a very important point of speed

measure that we need to understand

so what do all those peaks mean kind of

vibration people look at signals and

heartbeats how do they know

you know what the dominant frequency is

where is it coming from within the

machine

in

reality due to the complexity of the

fact i've got electrical vibrations i've

got process vibrations maybe here from

the air going through the ventilation

system i've got mechanical vibrations

inherently in the machine

the waveform is very complicated and

difficult to maybe relate to

but thankfully

there is a way to simplify this to make

what is a complex signal a much more

simplified signal

mathematically it's a very involved

process but thankfully due to uh

technology today

it's actually not that difficult in a

graphical way

and indeed for the analysts to very

quickly interpret the results so here's

my wave

here's the wave if i increase the speed

there just to make it a little bit more

destroying so we're going to speed up

the speed that fan

this wave the right one

of the signal represents one rotation of

the shaft

okay

so obviously as the imbalance grows at a

fixed speed now the speed is now fixed

the imbalance grows or it weakens

because

the shape of the wave

will go all the way

balance

so what do we do well

you know as you saw just now that

waveform is very complex well let's make

it easier

let's ask you this question here's the

wave i'm looking now at that signal i'm

looking 90 degrees at that signal what

do i see the end of the wave

a line a peak

so in simple terms

vibration systems today take the signal

initially like this which is currently

very simple

and they they convert it to a frequency

spectrum by initially i turn that 45

degrees

and then complete the 90 degree rotation

what do we see one single peak what do i

see looking at 90 degrees i see the

weight

so we take the time wave and we convert

it to a frequency

very crisp very sharp way of

presenting the data

this peak here would be

proportional to rotation speed let's

kind of switch it back again

and maybe the bearing here the defect

okay so the bearing's got a

hitted

spawn point on the bearing and in one

rotation there'll be a certain number of

pulsation forces every time a ball

strikes the bearing

count the number of poles is there if

you wish to

higher or lower frequency

higher frequency yeah so the green wave

is the heartbeat of the bearing

let's bring that together just click on

there sorry about that

there we go let's put it 45 degrees what

do we see

two separate peaks one proportional to

rotational speed

the unbalance in the fan and one that

shouldn't be there because there

shouldn't be a problem with the bearing

but it's appeared at i don't know 6.1

times the speed not six not seven but

6.1 times the speed for example

so that's a key difference for the

bearing it's actually not a whole number

so these peaks you know we can we can

separate them from a very complex wave

and trend them discreetly to know what's

wrong

with the machine it was vibrating too

much

so with knowledge

we could look at problems with spectra

and you know this might be a normal

reading there's hardly any other peaks

in the spectrum quite a low level

running speed peak which is very

normal to see at low amplitude happy

days

a heavy mass sticks to the fan up

frequency will grow the amplitude will

grow and we'll know exactly what's

causing our software we click on the pig

and we're told it's once times the

speed we'll see in a moment maybe if two

shafts are not aligned so two shaft

motor pump should be perfectly aligned

but maybe one is shimmed higher than the

other now think about the forces think

about the motion as it rotates one

rotation

one pulse

two pulses

one pulse two pulses so two puppets turn

two postures per rotation producing a

very distinctive characteristic second

peak an imbalance would not underline do

that

it's completely different

so different

parts different defects different

properties show a distinct difference

in the appearance

in the frequency spectrum in the

heartbeat of the machine here there's

obviously several peaks

if we have a problem with a bearing

for example this

this data here is showing me a small 1x

peak that's normal but these bearing

peaks should not be there end off

sadly it's a vibration reading they're

present the damage is done this peak

here is at 3.1 pulses per rotation if i

click on that in my software it would

tell me it's occurring at 3.1 times the

speed

it's three blade it would be a three

times the speed if the blades were

problematic but here it's 3.1

so that's indicating maybe a bearing

okay so the spectrum itself um

what's nice you know one single peak

maybe easier you know i can look at that

i can see one p

the reality is

machines don't produce just few pure

smooth vibrational forces some of them

can be shocked we've spoken about those

some of them might be uh you know

pushing and pulling forces against each

other with two shafts that are fighting

each other so that's going to cause the

data

to distinctly change and there's other

techniques which i'm sorry to say we

don't have time to cover today but you

know there's other supplementary

techniques that do support the analyst

in diagnosing problems

so where the vibration is smooth in

summary what do we see

you know heavy mass rotating around the

rotor you know a strong radial force an

increase in vibration at what frequency

once times the speed

so an imbalance in the system will

actually occur at once times the speed

little else present

that's the main problem

other peaks might mean there's a second

problem

the vibration's going to change it

behavior it's not such a smooth force

you've got two shafts fighting one

another

that'd be bolted down but think about

the stress

of the exhibits on that sheet

so that's going to change the shape of

the spectrum the frequency spectrum

where we see maybe more than just one

peak here we've seen three particular

peaks due to uh

non-linearity's distortion of of the

wave so being nice and smooth it's

distorted that fighting force is causing

that distortion

here with shock i know i always take

that scenario take a slow and throw it

into a pond you kind of get the impact

of the stone and then you get the echo

the ripple

here

shop might be quite small intent shops

here it's maybe quite visually

exaggerated but that will change the

shape of the reading we see the spectrum

the frequency part b

could come from bearings

shock could come from loose

shaft on the bearing so it's working

loose on the shaft that would cause

shock as well

that produces stiffly something uniquely

different

characteristics that we call harmonics

lots of them here we've got seven

typically we see actually a lot more

where something might be loose

harmonics like the echo kind of

scenario are equally spaced peaks

that appear in the spectrum equally

spaced piece so that's you know

distinctly different to what you saw

just now with a smooth vibration where

there was only one single dominant peak

one other factor maybe one step too much

here but let's just scratch the surface

um uh another characteristic in the

reading called sidebands

what's the difference well look at these

gears look at how the teeth that one

part of the rotation come right into the

roof of the teeth then the gap opens

so that means the vibration once the rev

goes strong

goes weak

goes strong

goes weak as it comes deeper into the

root the amplitude that wave and the

signal being produced very strong and

where it separates because there's not

so much force

the strength is

these are equally spaced peaks

either side of central peak

so here we have several peaks equally

spaced either side of the center

frequency

so they are spaced by a a delta a

difference in frequency that's known

and they're equally spaced and they're

common

on bearing problems

gear problems

looseness

bearings and gears maybe electrical

problems might be another one as well

where we see that distinct

behavior and again there's some more

side bends

maybe if the defect here think about

this the defect that red dot is inside

the bearing there's a pitted damage spot

when the defect enters the lower part of

the bearing due to gravity the forces

are greater so we get a stronger seat

look then as the debate

out of the load zone towards the top

as we said just a second ago a distinct

pattern suffers but we've got shock as

well

so what do we see shock results in

harmonics equally spaced peaks the

larger ones there in yellow

and side bands where we see equally

spaced peaks around those harmonics

maybe that's one step too far for those

of you that maybe are newer to the

subject but distinctly different

pictures to simplify

okay um

we've got some examples here some case

studies i think i have time to uh

maybe choose there's

probably too many to go through them all

but so i'm just going to go to this

particular one here

so

this is a hammer mill bearing um

on a particular bearing on a motor

there's the actual drive itself so this

mill

crushes or mashes wheat in preparation

for bi-ethanol

fuel reducing process

variable speed motor so it varies in

speed during operation

and monthly vibration measurements were

collected when the plant first started

up in 2010 and continued to monitor this

machine up to present day

on a monthly basis now this trend is a

trend actually of the shock within the

machine the impact force you know the

shocks that might be produced from a bad

bearing well this is the strength of the

shocks where at the baseline the first

measurement taken here which may not

always be the baseline actually

doesn't always mean it's good because

it's the first reading but it's 5g well

that's kind of quite reasonable it's a

p2p

measurement of the shock of

the signal up to 70 g's you can see the

degradation there is up to 70 g's

and then you can see after

repair that the level's returned to

normal afterwards

what's this well this is the frequency

heartbeat

of a particular point on the machine

the motor drive end or motor inboard

bearing here so this is the bearing at

the motor driving and you can see the

heartbeat month on month here

the most recent reading back when the

problem was present being at the back

how the heartbeat has changed

the heartbeat has changed if this was a

problem with balance for example that

was lower down the scale my 1x peak is

this kind of very small peak down here

not of concern but these stronger peaks

here are

you know the main cause

why that trend caused that kind of

degradation

so here we can see the actual uh singles

spectrum the heartbeat the frequency

spectrum from that particular point

and in this case we can clearly see due

to the purple dots there harmonics are

evident within that particular fft sorry

the spectrum itself the frequency

spectrum

equally space peaks clearly evident the

point is

what is the rate of those peaks what is

the spacing between it well the driving

frequency the first one

is at 3.05 times the speed so let's

spread it out to 3.1 times the speed not

three but 3.1 shots per rotation

this particular case the bearing was

known

the bearing was home

we knew it was a six three two two

bearing

and in that case that correlated with

these dotted lines

that match the outer race frequency of

the bearing so we knew exactly that it

was the outer race of the bearing

okay some might think we don't have a

bearing number in all cases not a

problem what else could cause 3.1 shocks

per rotation on a pump motor assembly or

sorry a grinder here and a motor

apart from transmitted vibration

somewhere else perhaps which it wasn't

because it was only present at the motor

electrical vibration

could cause a

strange number here but it wasn't that

it had to be

so we would have known anyway

so there's the actual bearing that was

um taken out it's a very distinct wear

pattern in this bearing as well which

provides the analysts with recorded

information because it's not just about

detecting the problem really conditional

monitoring only trends and tracks of

defect

to improve the actual conditions improve

the reliability we need to ask why what

caused it and what action we're going to

take rather than just say put a new

bearing in

what's caused it let's put that to bed

as well as obviously install a new

bearing

and i think since that time

after replacing them that's continued to

trend

quite happily to present day

so let's check the time yet so i've got

uh maybe more time for one more

um slight different twist of the tail

here actually um

this

problem um

is maybe not quite as common on general

plant but on certainly larger drives it

has a place where it could occur this is

more maybe common for a larger drive

not small sort of 1.5 kilowatts but

large machines

this is a motor driving uh centrifugal

fan it's a gas recycle fan you've got

your motor obviously with your two

plumber block cooper bearings here and

then your coupling is just under this

guard here

so again this machine i believe has been

trended periodically since 1999

on a monthly basis when the client runs

during their operational

a little season there about the machine

315 kilowatts 1500 rpm less slip

so my general vibration trend according

to an iso standard actually was well

within a tolerance

but because

it's important not just to trend

the general level of vibration perhaps

different parts of the vibration either

different heartbeats you can trend them

independently

this particular trend segment here

obviously violated an alarm

drilling down slightly deeper into the

data you can see the degradation this is

one particular point again this is on

the motor non-drive end so this

particular measurement was taken at an

android

the most recently

reading taken at the time this was a

problem is at the back and you can see

the visual picture there has changed

uh where you see obviously more activity

at the back harmonics

so there they are in a bit more detail

zoomed in there if you like and just

taking that one spectrum out

but

upon further investigation

we took a higher resolution measurement

like on your digital camera you take

more pixels if we take more lines we get

clearer sharper crisper peaks

and it revealed actually that we had

harmonics

equally spaced peaks

and

equally spaced peaks either side of the

central peak so we had harmonics and we

had cybex

which fits with what we discussed before

we had both

and you can see here this is the signal

in raw form very complicated very

difficult to relate to but the picture

is it goes strong it goes weak it goes

strong it goes weak the amplitude's

changing that's why they're sideways

the harmonics are there due to

distortion

zoomed in a bit more around those main

peaks there

and understanding the spacing of the

sidebands was the final part of the

jigsaw so the spacing between the

central peak and the peaks basically

equally

the difference the delta frequency was

the key

the spacing was 42 cycles per minute or

0.7 hertz

and then with some known mathematics

that to be focused where today deals

with this for you anyway but

mathematically this tied down

to a rotor bar problem

not a bearing problem

not a balance problem not relying on the

problem but a rotor bar problem

and thankfully the frustration can be we

don't always get the feedback but we got

feedback on this from the actual company

they they took it on board they planned

the repair centered away to the remote

repair shop and that is the damage

of the broken bar

that caused that distinct particular

harpy we knew it wasn't the bearings we

knew it wasn't the fan we knew it wasn't

the cutting it was down in this case

it's the actual rotor bars

okay so just some uh just getting on my

time there just

give me a skip to the end of that the

other time for another one

so

in summary

vibration is a useful tool on generally

rotating equipment

it's fair to say supplemented maybe by

high frequency methods it has

a wide variety of different defects on

rotating plant

and understanding the actual signals the

heartbeat is the key to understanding

what's causing the problem

and then judgments can be made as to

when you're going to do your corrective

action

so happy days i can't believe i've kept

that within the 30 minutes to be honest

but

it's gone so quickly but

for myself personally that's a thank you

but i welcome any questions