Insights to ASME pressure vessel design

I started my career in 1980 as process vessel designer in CE-Natco, US company famous in process design of various types of onshore or offshore process vessels, such as 2 or 3 phases oil/gas/water separators, gas dehydration with glycol regeneration, flare system, oil dehydrators, steam boilers, etc....  Apparently now the company is owned by Cameron, ref web....Cameron_Natco   Petrobras, Brazil state-owned is one that  has many of Natco topsides ( glycol gas dehydration package ) installed in the semi-submersible platforms even to-date, like P51,52 and 56.

I have gained quite a bit of knowledge and work experience in the 80s' at CE Natco and understood ASME Section VIII Div 1 vessel calculations where it is somewhat much easier compared to Div 2 design which is seldom in the market needs unless very high internal pressure. It is normally advisable and better to use Div 2 when internal pressure exceed 1500psig in terms of thickness savings and other kind of advantages, eg. nozzle re-pad which will be difficult and this is done with using special forged nozzles with thick nozzle wall to compensate for the opening loss of metal. Also with the thick wall vessel, post weld heat treatment will be mandatory after the complete vessel is being fabricated to stress relief the heat affected zone and remove the stress locked. Lately I noticed there was introduction of Div 3 and this is "alien" to me as I have not seen this reference presently in my job on offshore rig engineering at current organization. In the old days, design calculations and drafting were all done manually but now with availability of design and drafting softwares, it is now much more easier for pressure vessel designers as well as drafters. Less thinking job, leaving it to the computer.

The ASME International Boiler and Pressure Vessel Code establishes rules of safety governing the design, fabrication, and inspection of boilers and pressure vessels, and nuclear power plant components during constructions. The objective of the rules is to provide a margin for deterioration in service. Advancements in design and material and the evidence of experience are constantly being added by Addenda. Originating in 1914, the ASME Boiler and Pressure Vessel Code is now adopted in part or in its entirety, by all 50 states and numerous municipalities and territories of the United States and all the provinces of Canada.

The Code is kept current by the Boiler and Pressure Committee, a volunteer group of more than 950 engineers. The Committee meets regularly to consider requests for interpretations, revision, and to develop new rules.

In the formulation of its rules and in the establishment of maximum design and operating pressures, the Committee considers technological advances including materials, construction, methods of fabrication, inspection, certification, and overpressure protection.

INTERPRETATIONS

ASME issues written replies to inquiries concerning interpretation of technical aspects of the Code. The Interpretations for each individual Section will be published separately and will be included with the update service to that Section; up to the publication of the 2013 Code. Interpretations of Section III, Divisions 1 and 2 will be included with the update service to Subsection NCA. Interpretations are not part of the Code or Addenda.

CODE CASE SUPPLEMENTS

Code Cases clarify the intent of existing requirements or provide, when the need is urgent, rules for materials or constructions not covered by existing Code rules. Cases will appear in the applicable Code Cases book: "(1)" Boilers and Pressure Vessels or "(2)" Nuclear Components. Supplements will be sent automatically four times per year to the purchasers of the Code Cases books up to the publication of the 2013 Code.

Vessels such as steam boilers, air compressors, storage tanks, accumulators and large pipes are subjected to internal fluid pressure which is uniformly distributed. All the above mentioned vessels are classified as cylinders or spheres.


THIN CYLINDER:
If the ratio of the thickness to the internal diameter i.e. t/d is less than about 1/20, the cylinder is assumed to be thin cylinder.

THICK CYLINDER:
If the ratio of thickness to the internal diameter i.e. t/d is greater than 1/20, the cylinder is assumed to be thick cylinder.

STRESSES IN CYLINDERS:
The following stresses are :
CIRCUMFERENTIAL OR HOOP STRESS:
The stress which acts tangent to the circumference and perpendicular to the axis of the cylinder is called circumferential or hoop stress. It is denoted by fh.

LONGITUDINAL STRESS:
The stress which acts normal to circumference and parallel to the axis of the cylinder is called longitudinal stress. It is denoted by fl.

RADIAL STRESS:
The stress which acts in a direction perpendicular to the internal surface is called radial stress. It is denoted by fr. Radial stress is very small as compared to fl and fh in case of thin cylinder and is therefore ignored.


I have compiled a set of slides and extracted some pictures from web and I thank those who has directly or indirectly contributed to the information in this slide presentation and if there is any violation of copyright, do notify me and I shall have no reservation in removing the content immediately from the presentation. There are some slides that have hyperlink to other external files which will not be readable below, I apologise for this inconvenience, however should you need more information, do drop me a note  :-

Pressure vessel slides


pressure vessel slides



Understanding Well Control

INTRODUCTION

The function of Well Control can be conveniently sub-divided into two main categories, namely Primary Well Control and Secondary Well Control. These categories are briefly described in the following paragraphs.

1.1.1 Primary Well Control (Hmud > Pf )

This is the maintenance of sufficient hydrostatic head of fluid in the wellbore (HMUD) to balance the pressure exerted by the fluids in the formation being drilled (PF).

However, it should be noted that balancing formation pressure is a theoretical minimum requirement; good drilling practice dictates that a sufficient excess of hydrostatic head over formation pressure, be maintained at all times to allow for contingencies. This excess head is generally referred to as ‘Trip Margin’ or ‘Overbalanced’.

1.1.2 Secondary Well Control (Hmud < Pf )

If for any reason the effective head in the wellbore should fall below formation pressure, an influx of formation fluid (kick) into the wellbore would occur. If this situation occurs the Blowout Preventers (BOPs) must be closed as quickly as possible to prevent or reduce the loss of mud from the well.

The purpose of Secondary Well Control is to rectify the situation by either:

a) allowing the invading fluid to vent harmlessly at the surface, or

b) closing the well in. i.e. providing a surface pressure to restore the balance between pressures inside and outside the wellbore.

This latter procedure prevents any further influx of formation fluid and allows any one of a variety of ‘Kick Removal’ methods to be applied thus restoring a sufficient hydrostatic head of fluid in the wellbore. This re-establishes the preferred situation of Primary Well Control.

BOTTOM HOLE PRESSURE

The term ‘bottom hole pressure’, as used here, means the sum total of all pressures being exerted on a well by our operations. Bottom hole pressure is the sum of the hydrostatic pressures exerted by the fluids in the well, plus any circulating friction loss (e.g. Annular Pressure Loss), plus any surface applied back pressures, where appropriate.

This is the total pressure exerted by us. It is usually intended to at least balance the formation fluid pressures in the exposed portion of the well.

FORMATION FLUID PRESSURE (PF)

The formation fluid pressure, or pore pressure, is the pressure exerted by the fluids within the formations being drilled. The sedimentary rocks, which are of primary importance in the search for, and development of oilfields, contain fluid due to their mode of formation.

ABNORMAL PRESSURES

Abnormal formation fluid pressures, or ‘sur-pressures’ as they are sometimes known, can arise for a number of reasons.

They can be categorised as:

a) Differential Fluid Pressure
b) Surcharged Shallow Formations
c) Sediment Compression
d) Salt Beds
e) Mineralisation.

The main causes of kicks are:

a) Failing to fill the hole properly when tripping
b) Swabbing in a kick while tripping out
c) Insufficient mud weight
d) Abnormal formation pressure
e) Lost circulation
f) Shallow gas sands
g) Excessive drilling rate in gas bearing sands


INDICATIONS THAT A KICK IS IN PROGRESS

1) During Drilling

There are several indications which show that a kick is in progress:
a) FLOW RATE INCREASE.
b) PIT VOLUME INCREASE.
c) PUMP PRESSURE DECREASE/PUMP STROKE INCREASE.

2) During Tripping

The indication of the presence of a kick is:

a) INCORRECT HOLE FILL VOLUME.

If this indication is not noticed at an early stage, it should become progressively more obvious.
In the extreme case the hole would eventually stay full, or flow, while pulling out. This may sound ridiculous, but it has occurred.

b) HOLE KEEPS FLOWING BETWEEN STANDS, WHILE RUNNING IN.

The presence of some or all of these indications require that a flow check be carried out to determine whether or not a kick is in progress.

When a kick occurs, the surface pressure required to contain it will depend mainly upon the size of the influx taken into the wellbore. A small kick closed in early means lower pressures being involved through the kill. Furthermore it is easier to deal with a kick which is noticed early and closed in quickly.

ANNULAR PREVENTERS

Annular Closing Times

• API RP53 state that surface annular preventers closing times should not exceed 30seconds for smaller than 18 3/4” and 45 seconds for 18 3/4” and larger.

• Subsea annular preveters should not exceed 60 seconds.

Shaffer Spherical BOP

Shaffer annular BOPs are rugged, compact and will seal on almost any shape or size- Kelly’s, drill pipes, tool joints, drill collars, casing or wireline. They also provide positive pressure control for stripping drill pipe into and out of the hole. The annular BOP is one of the first lines of defence in controlling a kicking well. When the BOP is actuated, hydraulic pressure operates, and in turns closes the spherical shaped preventer. The closure occurs in a smooth upward and inward motion, as opposed to horizontal motion.

Special features include:
• Rugged and reliable sealing element provides positive seal after hundreds of tests to full working pressure.
• Strong and simple construction-only five major parts.
• Simple hydraulic system-only two hydraulic connections are needed.
• Wear rings on movable parts prevent metal-to-metal contact. This feature prolongs preventer life.
• Suitable for H2S service.
• Servicing is easy- Element can be changed without getting mud and grit into the hydraulic system.


Diverters

A diverter is a safety system, which reroutes a well fluid flow away from the rig. Shallow gas is permitted to flow until depleted, or until the well is bridged over or killed by pumping in heavy mud. Ready during upper hole operations, a diverter is intended for use when there is a danger of penetrating a pressurised gas zone, while the casing shoe strength may not be sufficient to contain shut in pressures. Massive flows of gas and sand can quickly destroy a rig’s diverter system. Hydril incorporate integral valve functions and switchable target to minimise equipment and thereby decrease the risk of malfunction.


MUD GAS SEPARATOR (POOR BOY DEGASSER)

The height and diameter of an atmospheric separator are critical dimensions which affect the volume of gas and fluid the separator can efficiently handle. As the mud and gas mixture enters the separator, the operating pressure is atmospheric plus pressure due to friction in the gas vent line. The vertical distance for the inlet to the static fluid level allows time for additional gas break-out and provides an allowance for the fluid to rise somewhat during the operation to overcome friction loss in the mud outlet lines. As shown in Figure 39, the gasfluid inlet should be located approximately at the midpoint of the vertical height. This provides the top half for a gas chamber and the bottom half for gas separation and fluid retention. The 30 in. diameter and 16 ft minimum vessel height requirements have proven adequate to handle the majority of gas kicks. The separator inlet should have at least the same ID as the largest line from the choke manifold which is usually 4 in. Some separators use tangential inlet, which creates a small centrifugal effect on the gas-fluid mixture which causes faster gas break-out. The baffle system causes the mud to flow in thin sheets which assists the separation process. There are numerous arrangements and shapes of baffles used. It is important that each plate be securely welded to the body of the separator with angle braces.

Well Control Basics

Guide to Drilling Eqpt Opns.pdf

Ageing Wisely

Some ways to live life more useful and possibly improve your prospect in the year of rabbit 2011:

Some feel that we should get less on the virtual internet and more real networking with professionals and "people on the street". Engage with them and networking in the real world will do far more good if you are into some business than networking in the virtual social networld. Most of the activities in virtual networking will likely not get you into any kind of productive or "economic" benefits, so to speak, unless you have that much free time to spare. Office seniors or executives often face issues they can’t discuss with others at the company. Sometimes they just need an outside perspective from another management executive. Example, some of Oracle CEO Larry Ellison’s friends are Apple CEO Steve Jobs and Mark Hurd ( HP ex-CEO). They met and discussed. I cannot imagine what happen when Bill Gates or Warren Buffet meets. A huge component of any manager’s success is their ability to anticipate significant changes or innovations. While nobody could really glaze at the crystal ball and predict, if you get enough anecdotal data from enough sources, you can get a pretty good idea of what’s going on. You don’t know what you don’t know. While there are exceptions, know-it-alls don’t typically get ahead. Managers know what they don’t know and do not try to be smart and fool themselves. It means they depend very much on comparing notes with others in their networking.

Whether 2010 was the best "recovery" year on record or a "lull and dull" year waiting for another few more unexpected world crisis to happen, learn what you can from the numerous events happened around the globe and move on. We all probably will be better off living in and focusing on the present and plan out what we should do in the coming future, be it with some risks, no risk at all.

Whether it is your lousy job, your unreasonable boss, or your a**hole colleagues, either do something about it or suck it up. Whining does not help but make everyone around your office as miserable as you are. It just dampen the office spirit further. If you need to spoonfeed your staff, give it to them bit by bit and tell them it is time now for them to "swim by themselves". Whatever it is that has you all wound up, if you actually bite the bullet and deal with it, it’ll free your mind for what really matters.

Put the E-gadgets down. Safe advice for pretty much all of us in this gadget-crazy world. You’ll be more productive and have more to look out for in life than what you think you have achieved so far.

If all else does not seem to work on your end, try changing it. We all faced with thing or issue at times we know aren’t working on our side. Whether it’s your job, your marriage, or your investment portfolio, once you know for sure, the sooner you change it, the likelihood you will work around it better.

Take care of yourself and not be hard on yourself. Just do the best you can and then, be good to yourself and those around your family members. Spend time with yourself and your love ones. Work out, eat right, meditate, get out and have fun. 

Try new things, take on some challenges, even if they might seem a bit of risky. Don’t take dumb risks but reasonable, calculated ones. Most people are too risk averse for their own good.

We all spend a good deal of time on "bs". You know what this is - mindless distraction. If it’s fun or with colleagues and friends, that’s great. But if you sit around for hours with your eyes glued to your LCD TV or notebook, you’ve likely got some problem and need to re-assess yourself. Keep away your laptop for a while, check your I-phone no more than once a day. Go for a walk every day and think about one of the issues on your list. Don’t worry about conclusions. Just think and think and you may realise you have been missing the point.

It maybe true that every chinese new year’s resolutions don’t really work except psychologically in your own mind. The start of a english or chinese lunar new year is as good a time as any to take stock of what is and isn’t working in your life and doing something about it. Do not look back and try to "search your soul" for what doesn’t exist and, instead, just do something worth about it. Simple said than doing it but with a little bit of push and commitment, you should be able to see some "light at the end of the tunnel", as they say.

People when asked how they feel about getting older, and they will probably reply : “Old age isn’t so bad when you consider the alternative.” Stiffening joints, weakening muscles, fading eyesight ( these are what my parents are now going through at the seventies ) and the clouding of memory, coupled with the modern world’s careless contempt for the old, seem a fearful prospect—better than death, perhaps, but not much. Life is not a long slow decline from sunlit uplands towards the valley of death. It is probably a U-turn and how you personally going to deal with it positively.

More on Offshore Drilling

A jack-up rig consists of a movable platform which can be jacked up and down the (usually) three supporting legs. The video clip below shows one of the typical designs. These provide a common means of drilling in water, where the water depth is relatively shallow - say, 50 to 400 feet.

Jack-ups will be floated out to location and the legs then lowered independently until they are bedded securely and the platform is level and above wave height. It is clear that their use would be restricted when

there are strong currents or an unstable seabed.

A semi-submersible is a floater drilling rig. In this case, a deck is supported by a tubular structure, and by two hulls to provide buoyancy. Again, the deck carries equipment, accommodation modules, a helicopter pad and typical layout is shown in the below video clip.

Semi-submersibles can move easily from one location to another either by being towed or under their own thrusters power. They are mainly used, therefore, for exploration and appraisal drilling where this ease of movement is essential.

When on location, the semi-sub (as it is often helipad called) takes on water ballast (into the two hulls, etc). This will lower the structure in the water and lower the centre of gravity. In this position it is shielded from the effects of rough water at the surface and achieves a high degree of stability.

A semi-sub can operate in deeper water than a jack-up. Its maximum operating water depth depends on the type of mooring system employed. Some semi-subs use anchors with wire and chain to hold them on station. Others use dynamic positioning which is a system of computer controlled thrusters, to maintain their position. Modern semi-subs using anchors may, in exceptional circumstances, drill in water up to 3,000 feet deep.

Semi-subs using dynamic positioning systems are capable of drilling in even deeper waters, up to 6,000 to 10,000feet deep.

The drilling equipment in the semi-submersible is more sophisticated compare to a jack-up and more costly as the semi-sub has various sea motions while afloat and the drilling system on board has to be able to function at the same time deal with the heave motions while the rig is afloat. Some drilling systems may be able to discoupled from the vessel in case of severe and uncontrollable situation such as unexpected storm or harsh environment and for the safety of the crew, the drilling riser may be released after the sub-sea LMRP/BOP is being shut from the well.

In comparison to semi-submersibles, a jack-up has some advantages:

a) Lower construction costs. Semi-sub usually cost almost double of that of jack-up or more
b) Less personnel required to run the rig. Jack-up has about 120men compared to Semi-sub with 200men onboard
c) Because of (a) and (b) lower day rates.
d) The possibility to work over a fixed platform.
e) It is cheaper for the operator to use a jack-up:
 -Less powerful tug boats to move the rig while it is afloat
 -No mooring system required, no lost time to run anchors. But some rigs now come standard with anchors
 -Less maintenance costs.
 -Surface BOP without sub sea system.
 -Simple well head assembly.
f) Less down time:
 -No wait on weather due to motions.
 -Drilling equipment can be handled faster and easier.

However, the jack-up have some disadvantages:

a) Limited water depth. The maximum water depth for the largest JU is 450ft. Semi-sub could work up to 10,000feet on the latest design.
b) Depends on bottom condition. The bottom soil conditions may cause a punch through or deep leg penetration. Semi-sub does not have such issue as it is afloat while drilling operation is carrying out.
c) In case of a blow-out the rig can not move off location whereas a semi could.
d) More fragile. Many incidents and damages during moving and because of a punch through. Statistics have shown that over 75% of the incidents occur under tow or during jack-up/jack-down operations.
e) Safe operations require strict procedures.

The table below show some of the different jackup designs ( excluding KeppelFELS design of A-class, Super A, B-class, Super-B,etc ) and its capability in terms of size, VDL capacity,etc :

Types of Drilling Rig Capability

Some key personnel on board the drilling rig and their roles and responsibility :-

Tool pusher - In overall charge of rig operations, implementing the drilling plan and compliance with all safety requirements. Reports to the company representative.

Driller - In charge of the drilling process and operations. Responsible for compliance with the drilling plan and for the drilling crew. Reports to the tool/tourpusher.

Assistant driller - Assists the driller. Usually responsible to the driller for the operation of bulk storage equipment (for handling mud chemicals, etc.) and for the mud flowline system. Reports to the driller.

Derrickman - Responsible for the storage and movement of tubulars in the derrick and monitoring the mud systems. Reports to the driller.

Roughneck - Works on the rig floor. Responsible for general rig floor activities under the direction of the driller/assistant driller. Reports to the driller.

Rustabout - A member of the general workforce, assisting with the movement of materials,cleaning, painting, etc.

Drilling Operation and components

Drilling Completion

Formulas for Drilling and Prod



Rig Functions

Drilling Mud Technology

Drilling Mud Technology

More on Offshore Drilling

A jack-up rig consists of a movable platform which can be jacked up and down the (usually) three supporting legs. The video clip below shows one of the typical designs. These provide a common means of drilling in water, where the water depth is relatively shallow - say, 50 to 400 feet.

Jack-ups will be floated out to location and the legs then lowered independently until they are bedded securely and the platform is level and above wave height. It is clear that their use would be restricted when

there are strong currents or an unstable seabed.

A semi-submersible is a floater drilling rig. In this case, a deck is supported by a tubular structure, and by two hulls to provide buoyancy. Again, the deck carries equipment, accommodation modules, a helicopter pad and typical layout is shown in the below video clip.

Semi-submersibles can move easily from one location to another either by being towed or under their own thrusters power. They are mainly used, therefore, for exploration and appraisal drilling where this ease of movement is essential.

When on location, the semi-sub (as it is often helipad called) takes on water ballast (into the two hulls, etc). This will lower the structure in the water and lower the centre of gravity. In this position it is shielded from the effects of rough water at the surface and achieves a high degree of stability.

A semi-sub can operate in deeper water than a jack-up. Its maximum operating water depth depends on the type of mooring system employed. Some semi-subs use anchors with wire and chain to hold them on station. Others use dynamic positioning which is a system of computer controlled thrusters, to maintain their position. Modern semi-subs using anchors may, in exceptional circumstances, drill in water up to 3,000 feet deep.

Semi-subs using dynamic positioning systems are capable of drilling in even deeper waters, up to 6,000 to 10,000feet deep.

The drilling equipment in the semi-submersible is more sophisticated compare to a jack-up and more costly as the semi-sub has various sea motions while afloat and the drilling system on board has to be able to function at the same time deal with the heave motions while the rig is afloat. Some drilling systems may be able to discoupled from the vessel in case of severe and uncontrollable situation such as unexpected storm or harsh environment and for the safety of the crew, the drilling riser may be released after the sub-sea LMRP/BOP is being shut from the well.

In comparison to semi-submersibles, a jack-up has some advantages:

a) Lower construction costs. Semi-sub usually cost almost double of that of jack-up or more
b) Less personnel required to run the rig. Jack-up has about 120men compared to Semi-sub with 200men onboard
c) Because of (a) and (b) lower day rates.
d) The possibility to work over a fixed platform.
e) It is cheaper for the operator to use a jack-up:
 -Less powerful tug boats to move the rig while it is afloat
 -No mooring system required, no lost time to run anchors. But some rigs now come standard with anchors
 -Less maintenance costs.
 -Surface BOP without sub sea system.
 -Simple well head assembly.
f) Less down time:
 -No wait on weather due to motions.
 -Drilling equipment can be handled faster and easier.

However, the jack-up have some disadvantages:

a) Limited water depth. The maximum water depth for the largest JU is 450ft. Semi-sub could work up to 10,000feet on the latest design.
b) Depends on bottom condition. The bottom soil conditions may cause a punch through or deep leg penetration. Semi-sub does not have such issue as it is afloat while drilling operation is carrying out.
c) In case of a blow-out the rig can not move off location whereas a semi could.
d) More fragile. Many incidents and damages during moving and because of a punch through. Statistics have shown that over 75% of the incidents occur under tow or during jack-up/jack-down operations.
e) Safe operations require strict procedures.

The table below show some of the different jackup designs ( excluding KeppelFELS design of A-class, Super A, B-class, Super-B,etc ) and its capability in terms of size, VDL capacity,etc :

Types of Drilling Rig Capability

Some key personnel on board the drilling rig and their roles and responsibility :-

Tool pusher - In overall charge of rig operations, implementing the drilling plan and compliance with all safety requirements. Reports to the company representative.

Driller - In charge of the drilling process and operations. Responsible for compliance with the drilling plan and for the drilling crew. Reports to the tool/tourpusher.

Assistant driller - Assists the driller. Usually responsible to the driller for the operation of bulk storage equipment (for handling mud chemicals, etc.) and for the mud flowline system. Reports to the driller.

Derrickman - Responsible for the storage and movement of tubulars in the derrick and monitoring the mud systems. Reports to the driller.

Roughneck - Works on the rig floor. Responsible for general rig floor activities under the direction of the driller/assistant driller. Reports to the driller.

Rustabout - A member of the general workforce, assisting with the movement of materials,cleaning, painting, etc.

Drilling Operation and components

Drilling Completion

Formulas for Drilling and Prod



Rig Functions

Drilling Mud Technology

Drilling Mud Technology