Expert answer:University of Nairobi Quantitative Risk Assessment

  

Solved by verified expert:Q1)The elimination of hazards is the first order of safety. The control of physical condition is basic and frequently difficult in a plant and it requires the best of scientific, engineering and management information for its accomplishment. The evaluation and control of mechanical and physical hazards encompass four engineering aspects: design, construction, operation and maintenance. Choose a suitable process industry and conduct a HAZOP and risk analysis study for a particular section of the industry or the total plant. List out the various factors and identify the issues taken into consideration about the discrepancies in the design, operation, control and maintenance of the plant. Through this analysis also bring out various protection methodologies presently adopted by the industry and discuss its ability in meeting the safety norms and standards. Q2) Industrialization and related activities in the last few decades resulted in many issues with the use and handling of hydrocarbons and other components used in oil and gas process industry. Major accidents represent the ultimate, most catastrophic way in which a process industry project can go wrong. Accidents cause death, suffering & pollution of the environment and disruption of business. To minimize accidents it is highly important to assess and analyze various risk scenarios associated with the industry and projects. Briefly explain about Quantitative Risk Assessment (QRA) techniques and mention its basic difference from other type of hazard analysis. Explain the objectives, methodologies and the procedural steps adopted in QRA. Choose any process industry and by using process flow diagram (PFD), briefly describe its salient features. Identify all possible hazards in the chosen section of the plant and tabulate process parameters (make suitable assumptions).List out minimum five failure scenarios and asses the risk quantitatively by assuming suitable failure frequencies Note: Q1) minimum 2000 words Q2) minimum 2000 words – Paraphrase – include relevant calculation, and justification wherever necessary. Include relevant pictures, diagrams, charts, graphs, tables etc. Give proper in-text-citations and reference (APA/Harvard style) – include conclusion for etch quotation
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Hazard Identification and management in oil and Gas industry using HAZOP
In this section, we will discuss how to conduct in detail an HAZOP study for a
speciific example, which I will illustrate you step by step. So, this section is dedicated to
hazard identification and management in oil and gas sector using HAZOP methodology.
Let us quickly recapitulate why and what are all the important factors which lead us
to do HAZOP study.
Oil and gas industry plays a major role in world’s economy. Huge investments are made
to upkeep the facilities in order to increase the production capacity, even marginally.
Any accident like blowout, oil spill, operational problems, shall cause heavy economic
loss to the industry. Several techniques are available to identify and assess these hazards.
For example, hazard and operability study which we call as HAZOP which are now
focusing in the present lecture. Failure mode effect analysis which is called FMEA,
which we will discuss in the subsequent lectures. Quantitative risk assessment (QRA),
which we will discuss in the next module. Event tree analysis and fault tree analysis ETA and FTA respectively which we will discuss in the subsequent modules.
Let us quickly recapitulate that HAZOP is actually applicable at four stages of operation.
You can apply HAZOP at the drawing board stage which we call as a design stage. You
can also apply HAZOP at the construction stage or the process stage. You can also apply
HAZOP when you want to make any process modifications or finally, you can also do an
HAZOP study once the accident has occurred. We specifically call this kind of action as
accident investigation report – AIR.
Now, I want you to take through a case study which we will discuss and prepare an
HAZOP report for this case study. This is actually an application problem of a group
gathering station. I hope you all understand what do I mean by a group gathering station.
I will explain very briefly what is the segment of analysis of a GGS considered in the
present study. I have identify group gathering station and tried to located the hazard and
operability problems of that station because a group gathering station in general has
potential to cause damage to the operation plant personnel and environment as well.
So, the objective of this study could be to eliminate or to reduce the probability and
consequences of incidence. Remember the catch word here is not an accident. Incident is
related to hazard, hazard is a scenario. As long as the hazard or the scenario is not
realized into an accident, there is no risk. So, to eliminate or reduce the probability and
consequence of incidents in the installation and an operation of a group gathering station.
So, this HAZOP study is applied to a GGS at the installation and operation stage itself. I
have used a software by name PHA-pro version 7 for preparing the HAZOP worksheet.
You can recollect that HAZOP worksheet can be recorded in two formats. You can have
a full recording format which includes all possible deviations from the design intent
given therefore, the report is very comprehensive. So, here what I am describing to you
is a full recording format of an HAZOP worksheet which is prepared or generated
using a software by name PHA-pro version 7.0.
Let us quickly go through the methodology how this case study was done. In a given
group gathering station from the piping and instrumentation diagram given to you in
detail, study carefully the P and I diagram and identify at least one section of the plant.
Now, we call this section identified as node in the study. Now, for that identified section
of the plant of the group gathering station define the design intent and the normal
operational conditions of this section. Once you have defined the design intent then
identify subsequently at least one deviation of this design intent or operating conditions
by now applying a system of guide words.
Recollect
that the guide words are primary and secondary
keywords which we discussed in the last lecture. Try to make a list of possible keywords
which can be appropriately used for the selected problem like a group gathering station.
Pick up those appropriate keywords and try to list them before you start doing an
HAZOP study. Then identify the possible causes related consequences and
existing safeguards for the identified deviations. Based on your detailed investigation
carried out on this level, suggest or recommend actions to reduce or to eliminate these
deviations. Finally record the complete discussions you have or you intend to
have with the management and also what recommendations you propose in terms
of reducing or eliminating or mitigating the envisaged risk on the plant.
These are as 8the following six steps of what we will do to carry out the HAZOP report
for the case study of the group gathering station.
Now, the case study considered is a group gathering station I have a figure of the station
in the next slide.
So, this is the group gathering station. I will explain this process very quickly using this
figure then I will explain what is actually happening in each of them slightly in detail.
This is a process and flow diagram of a GGS. There are many manifolds which supply
oil from the wells which are a type of non enhanced oil recovery feed. I call them as
group header, because the name group header qualifies that this is a header which
collects from different groups of wells in one. So, I can have many number of group
headers. Here in this P and ID, I have got two set of group headers – group header one
and group header two. The group header one and two receive the oil supply from the
drilling well to this collection point. From the group header one and two, the substance
or the content starts flowing to what we call as bath heater. There are many bath heaters
located in this scenario, there are about five in numbers. I simply say one to five.
The purpose of a bath heater is, it will separate oil, water, and gas from the accumulated
substance from group header one and two. To do this, I need a chemical dosing tank for
enhancing this process. So, I supply a dosing chemical from this tank to this bath heater.
This diagram do not show any of the instrumentation and the valves located because this
is simply a process flow diagram.
If you want to look at the location of valves and other pressure gauges and
instrumentations in the system you should look at what we call as process and
instrumentation diagram. So, from the PFD diagram once the substance is collected in
the bath heaters which is separating oil, water, and gas from the inlet substance the gas
collected is transferred to what we call as flare stack. The oil collected and the water
together will be sent to what we call as enhanced recovery tank. The recovery tanks ER,
there are about five to eight in numbers in this process. Then the substance is forwarded
further to what we call as jumbo heater. The jumbo heater again further purifies oil and
water, and whatever content of water has been separated, it has been taken to what we
call as ETP.
ETP is effluent treatment plant. The oil purified here or separated here is collected in a
storage tanks one to four, from the storage tanks one to four the oil is further dispatched
through the pump house to a common tank facility from where it will be distributed. So,
this is one segment of the process and flow diagram, which is under the present scope of
study. These are the nodes which I keep on marking in my P and FD.
So, the well fluid emulsion received at the limits of GGS is distributed to three
production manifolds. From the main group header well fluid goes to the bath heaters for
the first stage of purification where they separate oil, gas and water. The separated oil is
subsequently stored in the emulsion recipient tanks, which are called as E R tank
associated gas is then separated out and sends to what is called flare stack. The separated
water goes to effluent treatment plant what we call as ETP.
From the emulsion recipient tank, oil is then subsequently fed to jumbo heater through
the feed pump, for further refined treatment. In jumbo heater, further separation of oil
and water takes place. The separated oil is then subsequently pumped to what we call as
a common tank forum. So, this is my process and flow diagram which I am going to
concentrate, and based on this diagram and understanding the process I am going to now
do an HAZOP study.
Ladies and gentlemen, before we start doing an HAZOP study, we should first
understand what is exactly the process happening in the case, and how the flow takes
place. Based on this understanding, we should be in a position to select the design intents
of different nodes or segments in this case. Subsequently appropriate deviations can be
identified, because to prepare a HAZOP report primary and secondary keywords are
important. Primary keywords associate to design intent and secondary keywords are
associated with deviations. And only this segment of the group gathering station is now
currently considered for the HAZOP study. If you have any questions please play back
the couple of slides earlier, and try to understand the component level functioning of
each one of them for a better understanding of HAZOP report.
Remember, if you do not understand the process and the flow sequence of a given PFD, I
am sure you will not be able to successfully prepare an HAZOP report. HAZOP report is
a perseverance of possible deviations from the design intents of a given process plant.
So, mandatory is to understand the process first. I presume you have understood the
functioning of a group gathering station. You have understood the importance of the
selected nodes in the group gathering station discussed in the previous slide. Now, taking
forward or the HAZOP worksheets, which we are going to prepare using a software
PHA-pro.
For example, let me identify the first node. Name the node as one. Remember this is not
a typed excel sheet this is an outcome or a screen saved from basically the software
output. So, the software output says node one identified is given as group header which
is basically a twelve inches pipe designates 102-A3A class. The deviation from the
design intent is low no flow. And the type is a pipe line. So, basically you are talking
about a flow, and the deviation could be either there is no flow in the line or there can be
a low flow in the line. The design conditions and parameters considered for the study are
the following.
The liquid rate is about 2500 cubic meters a day. The gas flow is negligible, the
operating temperature in pressure 50 degree Celsius and 10 kg per centimeter square.
The viscosity of the oil is about 270 cp. And the density at operating temperature is about
966 kg per cubic meter. For the design intent and the deviation identified for the flow to
be either low or no what are all the possible causes, what could be the consequence, what
could be the safeguard and what are the recommendations, I will focus this specific
column slightly later.
Let us first identify the first class which can result from either a low or a no flow on a
pipe segment twelve inches diameter from a group header. There could a possible leak or
rupture on the header, if there is a leak or rupture you can very well understand there
could be either no flow or there could be low flow. The consequence this leads to a fire
and environmental hazard. There can be loss of material, the process can become upset.
So, all these possible consequences are subsequently numbered in an order, even all the
causes are also subsequently numbered in an order. You may wonder why this
numbering is significantly important.
This is necessary, because when we generate a report later by identifying the number I
can easily access any specific cause or any specific consequence for any specific
deviation in the report. That is electronically possible, because this is software generated
report.
So, wherever you see any of these recommendations given it automatically generates a
number associated under a specific heading. For example safeguard one for example, a
new cause again 1, 2, and so on. So, there is an order, there is a format, there is a
protocol which is a software initiates by itself, it is very easy and necessary understand
why this has happened.
After identifying the possible consequences for the causes resulting from these deviation
on a twelve inches flow pipe line of a group header, which is operating under the
following pressure and temperature, let us examine is there any safeguard present in the
system. Remember the availability of safeguard is not seen in process flow diagram, you
must look for process and instrumentation diagram. Once you looked at the process and
instrumentation diagram, you will know what are the possible existing safeguards or
recommended safeguards.
For example, these specific case fire protection systems are available in position in the
GGS. Considering the due regard for the existing safeguards in the system we
recommend the following; the pressure transmitter to be provided for the group header
line just to check whether the pressure can record a low flow, because pressure and flow
are related anyway quantitatively. So, if my group header has a low flow, because of
rupture, if a pressure transmitter is fitted at least from the pressure transmitter reading
one will come to understand that there is a problem of this deviation in the line.
Number two recommendation: Do periodic hydro testing for the pipelines. Hydro testing
is a physical examination category which will tell how a pressure to be maintained in an
existing pipeline. We also recommend periodic inspection must be carried out, and
thickness measurement of the line to be done. The thickness measurement will give me
an idea about the quality and standard of lifetime of the pipeline, because if this is
corroded or is the crude deposit is happening along the surface of the pipeline, because if
the diameter is effectively reduced, pressure will enormously increase whereas, the flow
will not be affected.
So, you will be able to understand that by measuring thickness. You can also avoid some
further more consequences or deviations on the existing line. When you look at the next
cause; for example, isolation valves – in the inlet crude oil line. The inlet crude oil line
may have an isolation valves, the isolation valves can also result in a consequence. It can
result in pressurization of an upstream section the process can be upset. The safeguards
could be pressure gauges are already available to tell whether the pressurization is being
done or not, a non-return valve is available just to check that the process is not very
seriously upset in the lines.
There are also bypass lines available in this GGS, in case any such problem occur, I can
bypass this from this line to next line. However, we still recommend the following. A
pressure transmitter is to be provided to check whether the pressure is available properly
or maintained properly in the line. Of course, we also recommend periodic inspection.
Now, you may see here very carefully that the recommendation column has a sequence
number 1, 2, 3. Now, three relates to periodic inspection, four also relates to periodic
inspection. So, two qualitative recommendation cannot have the same number, because
this is periodic inspection and thickness measurement this is a different kind of
recommendation, this is periodic inspection and maintenance of isolation valve this is
different kind of recommendation. So, whenever in the report you start typing, these
kinds of keywords in the software, the new number is automatically generated.
Let us look at the further cause, cause number three. Non return valve in inlet line on the
oil group, it can result in pressurization of the upstream section, it can also safeguard is
there using a pressure gauge, but we recommend to provide a pressure transmitter and a
period inspection of and maintenance of non return valve.
Ladies and gentlemen, remember that when you say a recommendation of pressure
transmitter is to be provided for a GGS it gets the number one, which is as same as the
number one what you already have in the previous recommendations. So, you can easily
identify that there is no overlap of this numbering in any such situations, and so on and
so forth, keep on analyzing the drain valve, the consequence then the safeguard and
recommendation.
Then choking of the inlet crude oil, the consequence could be pressurization, process can
be upset, though pressure gauge is available, you put a pressure transmitter has the same
number as it has been given earlier. When you enter for the first time in the software any
such kind of recommendation it generates a number automatically, and later on when
you try to invoke this particular recommendation the number is carried forward as a
constant number through and through of the report. So, absolutely there is no overlap of
any specific recommendation.
Now, there is a great advantage of this kind of common numbering, because if you really
wanted to know what is that recommendation of pressure transmitter to be fixed, simply
type this number one in the through and through report, it will easily access and tell me
where this recommendations are to be implemented? For example, the recommendation
one should be implemented in NRV in the inlet line, in the drain valve in the inlet line, to
avoid the chocking of the inlet line; all locations I have to install a pressure transmitter.
So, I can easily know where are the nodes which can address what cause this
recommendation is satisfied. So, this numbering is having a very exclusive and explicit
advantage in recording. Look at the periodic inspection just for recollection, the moment
I say periodic inspection it compares existing number and periodic inspection and
thickness of measurement of inlet crude oil line is having a different number seven like
this.
So, let us say, node. The second deviation which is high low, the previous deviation was
low or no flow, the type is a pipe line. The conditions of operation remain same. The
cause can be if there is a high flow; the high flow from upstream section of this node can
cause a pressurization of the line you can already regard for the pressure safety valve
provided in the line, but still we recommend to put or install a pressure transmitter in the
group gathering line. The recommendation is common for the previous deviation the
number is carried forward in the same pressure. Now also remember, if you have already
have an existing safeguard like a bypass line etcetera, again the number is carried
forward from the previous recommendation.
Like this manner, we can keep on identifying different kinds of primary and secondary
keywords, identify the deviation, identify the causes, subsequently consequences, check
for the existing safeguards, and keep on recommending, whatever action can be deemed
fit to either eliminate the consequence completely or to reduce the effect of this
consequence on the process. Let us now focus on this specific column, where I am
generating what I call as a risk matrix. This particular column has three sub division as
you see here. S L and R R; S stands for severity, L stands for likelihood.
Ladies and gentlemen, recollect from the previous lectures that risk is a product of these
two, and I am quantitatively converting – the qualitative statements into a number and
based on this number I give a risk ranking, it is not a rank of 1, 2, 3; I am using a rank of
A, B, C, D where A, C, B, etcetera have a specific meaning which I will discuss
subsequently in the coming slides.
Let us look at the third deviation; there can be reverse flow or there can be misdirected
flow on the group header line of 12 inches P 102 A3A under the same operating
condition. The isolation valve in the first g …
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