代做CPE61020: Hazards and Protections Autumn Semester 23-24代写留学生数据结构程序

CPE61020: Hazards and Protections

Autumn Semester 23-24

Instructions

This resit assignment carries 100 marks.

To complete this resit assignment please use the course notes and discussion, the references given plus any other research you deem appropriate. Please justify your statements; justification is as important as being correct.

Please submit your full assignment as a single document to the CPE61020 Turnitin 2023 resit submission point.

The file name of your submission must be your student number - module number e.g. 2201123456 - CPE61020.

The assignments are marked anonymously; please do not use your name within the assignment.

The front page of your submission must have your student number and the unfair means statement.

The unfair means statement is:

“The attached is all my own work except where specifically stated.  I have read the section on Plagiarism in the PGT student handbook.  I understand it and the attached work contains no Plagiarism as defined therein.”

Due Date

The due date for submission of the assignment will be advised by Student Support Please note:

It is your responsibility to ensure that your submission is in a format that can be marked; it is therefore recommended that you check this both before and after you have submitted.

Please refer to the PSLP student handbook for further information on assignment preparation and submissions.

Question 1 - risk understanding (15 marks total) Question 1a [5 marks]

Explain the concept of risk tolerability, using an appropriate diagram to illustrate your answer.

Question 1c (10 marks)

For each of the following activities identify potential hazardous events and for each event describe which risk measure(s) (i.e. Individual Risk, Societal Risk or Environmental Risk) you should focus on. In each case justify your decision.

You should identify a total of 10 events - a minimum of one event and a maximum of three events for each activity.

1)   Purging an oil storage tank in preparation for maintenance.

2)   Lifting afreight container onto an offshore platform.

3)   Offloading a LNG ship at a peakshaving terminal.

4)   Lighting up an industrial gas fired boiler.

5)   Replacing a filter on a caustic soda line.

Question 2 - LPG storage filling operation (55 marks total) Introduction

This question relates to the hazards and risks from the filling of a LPG storage vessel by road tanker.

Questions 2a to 2e comprise the various elements of a QRA on the operation.  Data gathered for the QRA can be found in Table 2. Note that you may not need to use all of the data in Table 2 or  you may need to add to it (quoting sources).

Site Layout

The vessel is located next to a factory which manufactures car parts (see Figure 1).

Figure 1 Site Layout.

Operating parameters

The storage vessel is operated at atmospheric temperature (average 15 oC) and saturation pressure.

The vessel is 1500 mm diameter × 6000 mm length and has an operating capacity of 5te.  It is  located inside a compound surrounded by a chain link fence with 2 (East and West) exit gates.

The vessel and all associated equipment are subject to an annual inspection and service.

It will be filled once a week by road tanker (15 te capacity). Figure 2 shows the storage and filling arrangement.

A flanged, steel braided, 25 mm internal diameter hose connects the tanker to the storage facility.  Liquid is transferred to the storage vessel via a centrifugal pump which is located inside the storage compound next to the vessel.

Tanker outlet valve XV1 and storage inlet valve XV2 are electrically connected to a panel located by the Western gate between the storage compound and tanker bay.  Push buttons on the panel allow each valve to be opened and closed.  An emergency stop button will close both valves simultaneously. It can be assumed that typically this will take 2 minutes to activate.  The push buttons on the panel may not always be accessible in the event of a release or fire.

The pump inlet valve HV1 is a manually operated ball valve.  Bleed valve HV2 allows the hose and inlet valve to be vented which discharges to an elevated cold vent.

A non-return valve NRV1 prevents liquid backflow from the storage vessel V1.

A Level Indicator and High Level Alarm (LIA1) is installed on the vessel which provides a local audible warning. The vessel is also fitted with a local pressure gauge (PI1) and a pressure relief valve (PRV1).

No fire protection (e.g. water deluge, passive fire protection) is installed on the vessel V1. The LPG road tanker is coated with passive fireproofing which provides 30 minutes protection against engulfment by jetfire.

Figure 2 LPG Storage and Filling

Filling Procedure

The filling operation consists of the following steps:

i)           Tanker arrives onsite and drives forward into LPG Tanker loading bay.

ii)          Open both gates to storage compound.

iii)         Remove flexible hose from tanker, positioning one end next to pump and the other next to the tanker manifold through the Western gate.

iv)         Connect hose to tanker manifold and pump inlet valve HV1.

v)          Electrically connect tanker outlet valve XV1 to panel.

vi)         Push button on panel to open valve XV1 on tanker and pressurize hose.

vii)        Check for leaks.

viii)       In the event of a leak suspend procedure until leak corrected.

ix)         Open ball valve HV1 to pressurize pump inlet line.

x)          Open bleed valve HV2 to allow liquid to fill hose and pump inlet line.

xi)         Close valve HV2.

xii)        Push button on panel to open storage vessel inlet valve XV2.

xiii)       Start pump P1 to transfer liquid to vessel.

xiv)       Monitor level in vessel using the level gauge (LIA1).

xv)        When vessel is full switch off pump P1.

xvi)       Push button to close liquid valve on tanker XV1.

xvii)      Push button to close liquid valve on vessel XV2.

xviii)     Open bleed valve HV2 on pump and depressurize hose and pump inlet line.

xix)       Close pump inlet ball valve HV1.

xx)        Close bleed valve HV2.

xxi)       Disconnect hose and store on tanker.

xxii)      Electrically disconnect tanker outlet valve XV1 from panel.

xxiii)     Close gates to compound.

xxiv)     Driver reverses from LPG loading bay and leaves the site.

Personnel distribution

During working hours (08:00 to 18:00 Monday to Friday), there will typically be 3 people loading finished components onto trucks in the loading bay with a further 6 inside the warehouse. The truck driver will be standing by the side of their vehicle as it is loaded. Outside working hours a security guard will be the only person present onsite and will be outdoors at a post in the loading bay.  Two security guards are employed in this role and work alternate shifts.

The LPG delivery can take place at anytime (i.e. within or outside working hours). The driver of  the LPG tanker will conduct the transfer operation and will be present throughout the operation (approximate duration 1 hour).

The nearest residential housing is located 40 m directly to the South of the factory and consists of a population of 100 people.  A second larger residential population of 500 people is located at adistance of 90m to the West of the factory. Residential population may be assumed to be present all of the time. At anytime 10% of the residential population can be assumed to be outdoors and 90% indoors.

Meteorological Data

Table 1 gives the annual average probabilities of wind from each direction. You may assume (typical) conditions of stability D weather, 5 m/s wind speed apply at all times.

Table 1 Wind direction probabilities

Direction (from)	N	E	S	W
Probability	20%	30%	15%	35%

QRA Data

Data has been gathered in preparation for conducting a QRA on the filling operation and is presented beloww in Table 2.

Table 2 QRA Data Table

Parameter	Value	Units
Level gauge readslow	0.01	/yr
Level alarm fails to sound	0.005	/yr
NRV fails to close	0.01	per demand
Hose rupture	0.001	per filling operation
Incorrect or omitted step in a procedure	0.0001	per procedural step
Tanker driver fails to respond to alarm	0.001	per alarm
Probability push buttons inaccessible for release or fire	0.05
Push button fails to initiate valve closure(s)	0.001	Per demand
Valve fails to close on initiation	0.005	er demand
Probability tanker ESD button is inaccessible	0.05
Immediate Ignition probability of LPG release	0.1
Delayed ignition probability of LPG release	0.2
Probability that ignited release impinges on vessel	0.2
Liquid release rate from ruptured hose	3	kg/s
Downwind distance to LFL from ruptured liquid hose (D5)	30	m
(Full) Crosswind distance to LFL from ruptured liquid hose	15	m
Fireball radius for 5te BLEVE	50	m
Fireball duration for 5te BLEVE	8	s
Fatality rate (outdoors only) @100m from centre of fireball	10	%

For flash fires assume a fatality rate of 50% to outdoor populations within the burning cloud and 100% to workers inside the warehouse (due to internal explosion) .

Assume a 100% fatality rate for any population (indoors and outdoors) within the fireball radius and assume that the LPG tanker driver is sufficiently close to the release to be within the flash fire for any wind direction.

Question 2a [20 Marks]

Develop a fault tree for “LPG liquid release from filling operation” .  Quantify the top event frequency using the “gate by gate” approach.

You need only consider releases at three locations - from the connection between the vessel and tanker, from the pressure relief valve and from the cold vent. You may assume that when normally venting down the hose and pipework at the end of the fill (step xix in the procedure), this will not result in a liquid discharge from the cold vent due to the small volume of liquid

involved.

You should consider human errors and equipment failures, but you should ignore releases directly from equipment on the storage facility which are unrelated to the filling operation (e.g. from pressure vessel failure, leaking pump seal etc.). Where a release is due to human failure to correctly complete a step in a procedure, you must fully describe the nature of the failure and refer to which step in the overall procedure it relates to.

Question 2b [10 Marks]

Develop an event tree associated with “LPG liquid release from hose rupture”,where the outcomes are described as “jetfire”, “flash fire”, “BLEVE” and “unignited release” .  “Flash fire” can betaken to include the subsequent jetfire and “BLEVE” can betaken to include the preceding jetfire and any preceding flash fire.  Use the tree to determine the frequency of each of the four outcomes.  The possibility of a VCE is discounted because of the low level of congestion.

A BLEVE of the storage vessel will be possible in the event of direct flame impingement on the vessel for greater than 10 minutes. Note that if the vessel is engulfed by fire it will not be possible to close manual valve HV1.  You may discount the possibility of BLEVE of the road tanker because of its passive fire protection.  .

Question 2c [15 Marks]

Calculate the individual risk from “LPG liquid release from hose rupture” to personnel working    in the loading bay area, to the security guard and to the two residential areas.  You may assume that risk is dominated by flash fires and storage vessel BLEVE.  For this exercise the risk contribution from jetfires and VCEs maybe ignored.  For flash fires, delayed ignition should be assumed to occur as soon as the (elliptical shaped) cloud reaches its maximum extent. For

BLEVE events you may ignore the consequences associated with any preceding flash fire. Flash fire and BLEVE hazard ranges are provided in Table 2.

Question 2d [10 Marks]

Calculate societal risk in the format “Potential Loss of Life (PLL)” from flash fires and BLEVE from “LPG liquid release due to hose rupture” .

Question 3: Two-stage separation process (30 Marks)

Figure 3 describes a two-stage separation process.

A mixture of liquid hydrocarbon product and gas from a cracking unit enters a high-pressure separator V1.  The vessel operates at a pressure of 50 barg (design pressure 55 barg) and a

temperature of 30C.  The gas offtake (methane) is directed to a compression system for

subsequent treatment and export into the sales gas pipeline. The liquid from V1 (mostly

butane) is transferred to the low-pressure separator V2. V2 operates at a pressure of 10 barg (design pressure 12 barg) also at a temperature of 30C. Gas from this vessel (a mixture of methane, ethane and propane) is directed to the fuel gas system.

Pressure relief valves are located on each vessel.  Vessel V1 relief discharges via PRV1 to a HP (high pressure) 10” flare line (back pressure 2 barg) and vessel V2 relief via PRV2 to a 18” MP (medium pressure) flare line (back pressure 0.7 barg).  The flow from V1 to V2 is under level control (via loop LIC1) which maintains vessel V1 at 50% full.  The orifice diameter for the level control valve when fully open is equivalent to a diameter of 30mm.

Question 3a [10 Marks]

Based on the following information determine the required sizing of PRV1 and PRV2 based on fire engulfment (you may assume single gas phase relief).

Vessels V1 and V2 – length = 7m, diameter = 2.5m, hemispherical ends.

For this part of the exercise, you may assume that any rise in pressure is due to vaporisation of n-butane liquid and the gas discharging from the relief vent will be pure n-butane (see Figure 4 for vapour pressure data).

Question 3b [10 Marks]

Quantify the change to the relief valve sizes if the vessels are fitted with fireproof insulation.

Question 3c [10 Marks]

For PRV2 determine the sizing for gas breakthrough due to loss of liquid level in V1 as a result of LIC1 valve failing open (again you may assume single gas phase relief).