Edunwa302:

If the plugs were fired in numerical order from one end to the other, the successive power impulses from the pistons would cause the engine to run very unevenly and vibrate excessively.

In a four-cylinder engine, vibration is reduced with a firing order 1, 3, 4, 2 or 1, 2, 4, 3.

To add, the crankshaft is an irregular shape object, the piston are all attached to it, to avoid vibration, the crankshaft must be balance dynamically when rotating. That is why u see piston 1 and 4 moving together and only one can fire at a time and piston 2 and 3 moving together and only one can fire at a time
For 6 cylinder engine, piston 1 and 6 move together, piston 2 and 5 move together and piston 3 and 4 move together and that balance the rotation of the crankshaft dynamically. That is why the firing order of 6 cylinder engine can be 1,2,3,6,5,4 or 1,5,3,6,2,4 etc. Once u understand that ur crankshaft has to be balance dynamically and how the piston must move to balance it, den u can chose a firing order as a designer. The same principle apply to 8 and 12 cylinder V-engine

Edunwa302:

Oga pls there's OK? , all internal combustion engine(4stroke/2stroke engine) makes use of diesel or petrol the different is just the injection system which is either compression injestion system or spark injection system.
Its not only heavy duty engine dt runs on diesel, some keke en family size generating set which are two stroke power engines use desiel dt u v nt seen doesn't mean there's none thank you

I work on heavy duty and rotating equipments and I have not seen 2 stroke engine using diesel, it seems possible theoretically but practically, I have not seen. Even in small size family gen I have seen 2 stroke engine using petrol, I don't know of keke. U can tell us the name of the manufacturer of the 2 stroke engine u have seen using diesel. Am not doubting u cos not all engine I have seen but u can tell us the name of the one u have seen to be more sure.
If at all it exist, it must be a very small engine

GeneralSnipper:



Me wen be learner? I gree get power to challenge BABACHA, you see that name Only you nah chairmen.

At least all them wen dey follow you hold ground for grammar self go learn from this. Bros yeeee only you be Broses, you too much. Nice one.............

As e be so if you do mechanical key point for the house office go pay well ooo. Lol!!!

Cheers bro!

Guy u too much too o, I admire the level of ur mechanical reasoning, I be boy o, I no fit open mouth for where my supervisor dey talk o, I learn from him and if u have a good boss, u learn fast.
All of us have partial knowlodge, no one can be expert in all areas of mechanical engineering, if we disagree, that gives us room to research more

GeneralSnipper:


Oga! Get it clear, there are four stroke petrol engines that use carburetor. Look for an old Peugeot 504 engine and you'll see it. We are all here to learn bro..........

I can see you have some good mechanical knowledge, nice one. Here are some questions for your attention

1.) If an engine is not designed to be water cooled (i.e. no radiator) what other means can be used to cool it? Explain the principle behind it.

2.) Why does a two stroke engine generates more smoke than a four stroke engine?

3.) A pump comes alive when powered on but it's not pumping, what could be the problem?

We no dey challeng ourselves, we are sharing idea, throw ur question to the house not me, but let me answer ur questions.
1, Engine are iether cool with liquid or air, if there is no radiator, u use air. But there is a major disadvantage. Air has a low heat density so if the speed of ur air is low, it can only carry a small mass of heat.

2, 2 stroke engine smoke more because they burn oil. Mind u, 4 stroke engine can also produce excess smoke if the piston ring is bad. To add more, these are what causes engine to smoke
Black smoke- if ur air/fuel ratio is imbalance, ie too much fuel in the combustion chember or less air in the chember
White smoke-incomplete combustion
Blue smoke-ur engine is burning oil, ie ur piston ring is bad and oil is entering the combustion chemberl

3 a pump can be runing but not pumping due to any of the following
1, If the suction pipe is not completly filled with liquid
2, If air is leaking into the suction pipe
3, If air is leaking into the pump
4, If ur foot valve is blucked
5, If ur suction pipe is not fully submerged
6, If ur empeller is mounted wrongly
7, If ur pump is not prime
8 etc

gbonsquare:

Bro...I still dont understand bro...I need aw Uare to relate d velocity of a body in a circular path with d angle of an inlet and discharge outlets of centrifugal pump...Thanks Bro!

If u use ur hand to spin water that is inside bucket, u will observe that the water will move away from the center of the bucket to the edge creating a vacuum at the center. That is what centrifugal pump does, the empeller spin the fluid and a vacuum is created at the center of the empeller for more fluid to come in. That is why u have ur suction at the center of the empeller.
From simple harmonic motion, the velocity of object in circular part is usually tangential to the circumference, that is why the discharge is always tangential to a particular point on the circumference of the empeller.

Draw a circle, draw a tangential Line to any point on the circumference of the circle, from the point of tangent, draw a line to the center of the circle. Ur 90 degree will appear. The tangential line is the discharge and the center of ur circle is the suction.
Hope is clear?

presiade:

You're not seeing your mistake. 4 stroke engines can either be CI (diesel) or SI (gasoline/etrol). It seems what you believe is 4 stroke engines are mainly diesel consuming. Car engine is 4 stroke and some run on diesel, others on petrol.
Get it?

Those petro car that u talk about use injector, do u know?

Petro is liquid, u can't compress it

presiade:

You're not seeing your mistake. 4 stroke engines can either be CI (diesel) or SI (gasoline/petrol). It seems what you believe is 4 stroke engines are mainly diesel consuming. Car engine is 4 stroke and some run on diesel, others on petrol.
Get it?

Let me tell u how the air move, from outside to the air filter, from air filter to inlet manifold, from inlet manifold to inlet valve, from inlet vale to chember,

Bros we are all learning, this is practical not theory,
If u tell me the point they mix and the component that mix them, I will agree

lobito007:

Bro, do your research adequately before posting here so as not to mis-educate people. To start with, liquids can be compressed due to the weak inter-molecular forces between them. 2: four-stroke engines could be of diesel or gasoline. The difference is that in a diesel, combustion occurs by just compression of the fuel-air mixture. In a gasoline engine, combustion occurs via spark plugs. This is why diesel engines are said to have a higher thermal efficiency than gasoline engines. The heat generated during compression alone is enough to bring about combustion.

Let me tell u how the fuel or diesel move in 4 stroke engine

From the tank, the fuel move along the hose to the primary fuel filter, from the primary it move to the secondary fuel filter (if the engine has two fuel filter), from the fuel filter to the injector pump, from injector pump to nozzle, from nozzle to combustion chember,.
If air should enter ur fuel line, ur fuel pump will not work effectivly and ur engine will go off. That is why mechanic bleed the fuel line to remove any air trap.
So fuel and air no dey mix with 4 stroke engine before they enter the chember

lobito007:

Bro, do your research adequately before posting here so as not to mis-educate people. To start with, liquids can be compressed due to the weak inter-molecular forces between them. 2: four-stroke engines could be of diesel or gasoline. The difference is that in a diesel, combustion occurs by just compression of the fuel-air mixture. In a gasoline engine, combustion occurs via spark plugs. This is why diesel engines are said to have a higher thermal efficiency than gasoline engines. The heat generated during compression alone is enough to bring about combustion.

Go to a mechanic workshop and ask..

There is no 2 stroke engine that use diesel,
Also ask them if air and fuel are mixed before they enter the combustion chember.

This in not theory but practical, u can go and read more

Also the compressibility of liquid is so small that is regarded as incompressible, visit ur fluid mechnics text book again.

I have one question for u, can u tell us which component mix the air and diesel before they enter the combustion chember? I never see diesel engine with carburator
Another question for u, what is the need of compressing the fuel?
Bros go look heavy duty diesel engine very well before u argue. Fuel and diesel meet only at the combustion chember

sharks776:


In contributing my quota to the service of my country, I believe this organisation (NNPC) if not the most, is the largest and I will love to build a carrier here while moving the organisation to becoming the biggest in Africa. (i stand to be corrected by nairalanders)

From my own angle, I think is better u mention what attract u to NNPC, such as their core value, carrer growth, their level of technicality etc but not salary, and that those are the things u are looking for in ur carrer life and that u will be happy to develop ur carrer with them

2 stroke engine has carburator that mix ur air and petrol but 4 stroke engine do not have carburator.
4 stroke, ur turbo charger suck in air and only the air enter through the inlet valve while ur injector and nozzle break down the fuel to a form of gas and they enter from the nozzle.
That is why they call diesel Automotive gas oil (A G O) cos the injector and nossle break it down to gas form and as the nozzle spray it into the compressed air that is already hot, combustion take place

lobito007:

Good analysis. However you should note that in a 4-stroke engine, like in a 2-stroke in engine, it is the fuel-air mixture (not only the air) that enters the piston during the intake stroke and is compressed.

Bros in 4 stroke engine, is not the mixture of air and fuel that enter combustion chember, 4 stroke engine
are diesel engine, u don't have any 2 stroke engine that is diesel.
4 stroke engine, air enter first, after the air has been compressed, then the nezzle spray in diesel in form of gas into the combustion chember. That is why u don't have nozzle in 2 stroke engine because the mixture of air and fuel enter the chember from the inlet valve.
But in 4 stroke engine, only air enter the chember from the inlet valve and fuel enter from the nozzle. So they don't mix before they enter
U compress air to make it hot, u don't compress fuel, fuel is liquid and air is gas

gbonsquare:
Pls I'm not an English teacher ooo and I'm not forming one.I just like that Ur question as it interest me as a Mechanical Engineer.I want to try providing an answer...
The Suction and discharge at 90degree should be because each turn of d valve is a quarter.so the opening and closing of the outlets is 90degree.

The answer is in ur simple harmonic motion, just go back and look at ur simple harmonic motion, especially the velocity of an object in a circular path, then u will understand it more clear why the suction and discharge of a centrifugal pump are usually 90degree but if u still don't understand, we can share it togther here

Olumosey:
@ gloom: U r vry correct. PSV n PRV do nt regulate flow, bt release excess pressure 4 safety of personnel n equipments.

Actually globe valve and angle valve are best use for regulating flow, but PRV keep the flow constant and in a way regulating.

We are all engineers, we all can research futher on it, we are all learning and am open to learn from any one here

Gloom:


Sorry, am not going to argue with you. We learn everyday. Even with my experience in the industry, I still open up to learning from our vendors. What you read in books are guides to real field realities. Am for EH but I still come to this thread to check on technical contribution I could benefit from.

We all are learning, am still a boy in the oil and gas and I be boy for where u dey. If my experience in the oil and gas where to be above 5years, I would have apply for EH like u, we still need ur contribution here, we are only sharing idea and we learn from each other. But don't see us as those just talking from what we read in books, some of us are working in the oil and gas sector too but not up to ur years of experienc.

Gloom:



In a process design, there is what we call operating pressure and maximum allowable working pressure. It is desirable for you to keep your operation within the designed operating pressure. However, pressure build up comes up at times due to improper lining of valves, problem with instrument air that operates SDV. Pressure relief valves are mounted along the spool to prevent the pressure from building up to the maximum allowable working pressure. MAWP is based on the pipe schedule.

In oil and gas operation, you don't usually rely on gravity to push flow. In tank application, you normally have a recycle pump to push the flow. For a wellhead, because the downhole formation pressure is high enough to create desired flow rate, a choke valve and some other valves are used.

You only rely on gravity to drive flow in domestic application.

So if a pressure relief valve are mounted to remove excess pressure that may build up due to any reason and keep the flow rate within a safe working operation, then the valve is not only acting as a safety valve but also as a flow regulator because absent of it will increase the pressure and when pressure increase, flow also increase

Gloom:



In a process design, there is what we call operating pressure and maximum allowable working pressure. It is desirable for you to keep your operation within the designed operating pressure. However, pressure build up comes up at times due to improper lining of valves, problem with instrument air that operates SDV. Pressure relief valves are mounted along the spool to prevent the pressure from building up to the maximum allowable working pressure. MAWP is based on the pipe schedule.

In oil and gas operation, you don't usually rely on gravity to push flow. In tank application, you normally have a recycle pump to push the flow. For a wellhead, because the downhole formation pressure is high enough to create desired flow rate, a choke valve and some other valves are used.

You only rely on gravity to drive flow in domestic application.

We are talking about the uses of valves and u said they don't stop and start flow and I explain to u how they stop and start flow, tanker discharge petroleum product at the filling station by gravity, is that domestic use? Visit tank farm and see more flow by gravity
Note also that temperature increase the pressure in pipeline, especially if the pipeline carry PMS

My guy oil and gas is wide, try understand what happen in the upstream, midstream and the downstream, don't limit ur explanation to only the upstream cos NNPC operate in all the streams

[quote author=gbonsquare post=32704489]

Babacha but U said two stroke have two valves-d inlet and exhaust valve therefore have no induction and compression strokes but the other person said two stoke have two valves which fires for every turn made by d crankshaft(revolution) ...Pls Engr Babacha...explain further![/quot

3 things are needed for combustion, fuel, air and heat

In 4 stroke engine, the air and fuel are not mix b4 they enter the combustion chember, so u have one stroke for intak of air, another stroke to compress the air, the compressed air becomes hot, Those two stroke make one revolution. After compressing the air, u have one stroke for combustion and another stroke for exhaust, these two stroke again make another revolution and that is how u have the two revolution for 4 stroke engine

Now in 2 stroke engine, the air and the fuel are mix before entering the combustion chember, so u don't have intak of air and compression of air.
When the mixture of air and fuel enter the chember, the spark plug bring the heat that is needed for combustion. So u only have combustion and exhaust stroke and those 2 stroke make one revolution which is the one revolution for 2 stroke engin
Both 4 stroke and 2 stroke engine have 2 valves

Gloom:
[ :-


Pressure relief valve and pressure safety valve are both safety valves and not for flow regulation. One is used in liquid application and the other in gas application

When u remove excess pressure along a line such that the flow remain constant, what are u regulating? And that is what pressure relief valve does, it regulate flow.

If I have product stored in a tank such that the product flow out by gravity and I close the valve along the line in which the product fow out, what have the valve done? It stop the flow and when I open the valve, it start the flow again. I don't need pump to stop and start flow under gravity, is valve that does that

For more information on valve, check shell SITP training material, u will see the 3 things I mention

There is question that every one who put experience in his or her CV should expect.

Let all share some idea on it, that question is

Why do u want to leave ur current place of work to join NNPC?

Guys ur idea, no comment is wrong

uyosolo:
@caucasian,r u fightin against flesh nd blood or principalities nd power? U seriously nid help!!! Ur village ppl hv troubled u too much

Guy how far, how ur day na?

Caucasian:
Hahahaha ... it is not chEms but chAms. You are too dull like sombaby. You are even making errors in what you just spied. And who told you I didn't pass?

My guy went back to those two thread and delete his post there, u for leave them make people go read. Infact I no get ur time again

To throw more light.
1, under those that stop and start flow, u have valve like gate valve, butterfly valve, ball valve etc
2, Under those that regulate flow, u have the pressure relief valve and they are usually spring loaded, the spring is design with a certain pressure in view. When the pressure on the line exceed what the spring can hold, it pushes the spring and the valve open for some fluid to flow out of the line to regulate the pressure.
3 under those that stop back flow, u have the check valve

scarletdp:

To ensure flow in a specific direction

That is good but they do more than that. The do basically 3 things
1, To stop and start flow
2, To regulate flow
3, To stop back flow

Let some one bring question too na

Ozugbo:
Guy u ar 2 much in ur 'english'

Guy I no dey perfect o and i am not mr know all, I keep learning and I upgrade myself not only in english but in all aspect of life. But one thing am sure of is that, when it comes to defending what I know,
and business friendly, my level of "grammar" can sail me through.
I prepare report when I am on duty, I deliver pep talk, I take part in most meetings. Is it my local language I use in all of this? After all, how many nigerian president are pro in English, but we understand them when they speak and that is what every company need, been able to communicate reasonbly with English. U social science guys should be careful the way u promote English and grammar.
I have said this before, most of the expert in nigeria are not good in English, u hardly hear them when they speak if u ever work with them and they earn their salary in doller.
Guy na money be the mata, forget English and grammar, watin small boys with HND dey get for total, mobil, chevron, those professor in English no dey get am o
If u are good in grammar, that is fine but don't look down on the other person because every body has his own way of attaining his goal

For the engineering guys, let's share one question that u often see in an oil and gas company interview

What are the uses of valves?

No comment is wrong, let's share ideas

prelinctus:
@babacha, you seem to misunderstand my intent. Let me put this into perspective. Most major companies, in recent times, have moved on from just 'panel interview' to 'assessment centre'. If you've ever been to an AC(obviously you haven't), you'd realise there's always a presentation stage where you'd have to express yourself. Communication skills, among other things, are examined here. Now, if you commit the kind of blunders you've been committing here, you'd be written off even before you have the chance to flaunt your mechanical engineering skills at the interview stage. So, just accept the corrections and kindly do the needful.

My guy let me correct u so that u don't judge me with what u see here.
The last interview I did was not for children. After the aptitude test, they gave those of us who pass a topic to develop on power point with not more than 5 slide. I develop the topic using power point, save it to a flash and on the interview day I went there with my flash and deliver a presentation using the slide I prepare for 10minutes, after that, the panel start asking question as I stand in front of them, they gave me marker and some times I need to make a sketch on a board to answer their question.
At the end, with the help of God I passed and that is where I am currently working now. So guy don't judge me here cos is not an exam and I am not reporting to any body here,
If both of us are to face a critical assessment with a prize attached to it, if u pass me even in this ur english u think u know, then I will have to go back to school

To tell u too, I have taking part in a debate organize by one of the bank in nigeria. From the branch level, I move to the state level and then to zonal level and finally to the national level and I came second nationwide at the last stage. The recommendation letter the bank gave me is still with me and if u want to see, send me ur email and I will send it to u. Bros mind the way u judge me

Caucasian:
... Too bad. I thought you were almost better than your husband (abacha) who uses his half engineering degree as an alibi for his overall academic poverty. I guess you were a baby engineering student too.

My commiserations for you hinges not only on your poor mental coordination and spelling errors but also on your careless and dirty talk. YOU TALK VERY DIRTY. Using the " F " word at random just like you really do in the secrecy of your hypocrisy.

You were even asking someone if you did a nice job. Hahah haha ha ha.. what a local girl you are with zero self-awareness. Like i did to your shameless abacha, I would also show you a level of maturity and mental discipline by not insulting your parents in return because I respect them even if I don't know them at all.

It took you almost too days to compose this shit. Groping for words to express your tiny mind and all you could produce is your imperfection in speech and disgust. Aawwwwww!!! SomMUMU oh sorry sombaby, you are less than decent my dear. No wonder I just chose to disregard you from the beginning as I labeled you INSIGNIFICANT.

Am glad my test really paid off. .. Your performance revealed your filthy self and poor moral up-bringing. Keep it up pig.

Let me quote cuascasian word for word

On Chems Mangement Trainee thread, u said " wande I ve not gotten an invite yet" when ur mate who pass has been invited

Again, on CITA Petroleum Aptitude Test Invitation thread, u said "Plzzz someone tell me.. are they still calling or inviting for interview? ? Am in the social sciences. . Or does any one knows if they ve already conducted interview for dose in social sciences? ? Am new here plzz let a gud fellow help with a gud
response."
U still did not pass again wen ur mate has been invited

So all this ur grammar na here u dey
use them, u no dey fit use them pass aptitude test. Guy u get brain.

Poeple here don pass aptitude test, pass interview and even dey work. Go pass aptitude test first before u talk here

Abeg sombaby no answer him again, na fustration dey worry him

He is already crying over his own failure I beg make una no make him cry again. Prilinctus if u know who get blo job, I beg contach him make he manage that one since he no dey fit pass aptitude test, blo job no need aptitude test, no give him work dat need test o, he no go fit pass

uyosolo:

na so,b4 Adam nd Eve open eye,we don open eyes finish,no dulin,oil republic...i tink i knw dat ogaga,bt nt sure if its d pngp ogaga or med ogaga...i dnt wnt to mention my name so dat som ppl wud nt throw me 4rm towers

Guy I beg no mention ur name here o, we go find time know ourself more, I enjoy making pti graduates as friends, I base in ph, if na ph u dey too, den we can see in any of my off days

prelinctus:

Lol, nice one. Admit it, you were bored too, weren't you?

Body don sweet u nao, na watin u dey find be dis, cuascacian na ur guy o, he don beg u say he need job and he don tell u the one he fit manage o, go find work him o, but pls check for STD before u give him any work

I could recall, in early 2011 when I did interview with Nigeria Flour Mill, the head of the panel ask me "Why did I put on suit to this interview, don't I know is an engineering position?"
Before I join sahara group in 2012 (am no longer with them now) during my first stage interview, one of the panelist ask me " if I were to become an animal, which animal will I become and why?" And in the second stage interview with the MD and Head of operation, the MD ask me "which football club do I support and why I support them"
U can't predict interview question, u just have to be bold and say some thing reasonable