Casing

Drilling a well modifies the mechanical and hydraulic equilibrium of the rocks around the borehole. Periodically this equilibrium has to be restored, by inserting a good casing. The casing is a steel tube that starts from the surface and goes down to the bottom of the hole and is rigidly connected to the rocky formation using cement slurry, which also guarantees hydraulic insulation. The casing transforms the well into a stable, permanent structure able to contain the tools for producing fluids from underground reservoirs. It supports the walls of the hole and prevents the migration of fluids from layers at high pressure to ones at low pressure. Furthermore, the casing enables circulation losses to be eliminated, protects the hole against damage caused by impacts and friction of the drill string, acts as an anchorage for the safety equipment and, in the case of a production well, also for the Christmas tree. At the end of drilling operations, a well consists of a series of concentric pipes of decreasing diameter, each of which reaches a greater depth than the preceding one. The casing is a seamless steel tube with male threading at both ends, joined by threaded sleeve joints. The dimensions of the tubes, types of thread and joints are standardized (API standards). There are also Special direct-coupling casings, without a sleeve joint.

The functions and names of the various casings vary according to the depth. Starting from the uppermost and largest casing first comes the conductor pipe, then the surface casing and the intermediate casing, and finally the production casing. The first casing is called the conductor pipe and is driven by percussion to a depth normally of 30 to 50 m. It permits the circulation of the mud during the first drilling phase, protecting the surface unconsolidated formations against erosion due to the mud circulation, which could compromise the stability of the rig foundations. The conductor pipe is not inserted in a drilled hole and is not usually cemented, and therefore it is not considered a casing in the true sense of the word. The first casing column is next and protects the hole drilled inside the conductor pipe. It is also called the surface casing and its functions are to protect the freshwater aquifers against potential pollution by the mud, to provide anchorage for the subsequent casing, and to support the wellhead. To increase its stiffness and make it capable of bearing the compressive loads resulting from the positioning of the subsequent casings, the surface casing is cemented up to the surface. Its length depends on the depth of the aquifers and on the calculated well-head pressure following the entry of fluids from the bottom hole into the casing.

Wear Factors

The wearing of metal parts is the gradual decay or breakdown of the metal. When a part becomes so deformed that it cannot perform adequately, it must be replaced or rebuilt. Though the end results of wear are similar, the causes of wear are different. It is essential to understand the wear factors involved before making a hard surfacing product selection. It is actually easy to select a surfacing alloy if all metal components are subjected to only one type of wear. However, a metal part is usually worn by combinations of two or more types of wear. This makes an alloy selection considerably more complicated. A hard surfacing alloy can thus be a compromise between each wear factor. The initial focus should centre on the primary wear factor and then the secondary wear factor(s) should be examined. For example: upon examining a worn metal part, it is determined the primary wear factor is abrasion and the secondary wear factor is a light impact. The surfacing alloy chosen should not only have a good abrasion resistance but also a fair amount of impact resistance. There are five major types of wear Abrasive (3 categories)

Impact

Adhesive

High temperature

Corrosive.

Abrasive wear - Abrasive wear is caused due to the foreign materials rubbing against a metal part. 50 - 60% of all wear on industrial metal components is due to this. Abrasive wear is this a wear problem. It can be categorized into three:

a. Low-stress scratching abrasion – This is the least severe type of abrasion where metal parts are worn away through the repeated scouring action of hard, sharp particles moving across a metal surface at varying velocities. The velocity, hardness, edge sharpness, angle of introduction and size of the abrasive particles all combine to affect the amount of abrasion.

b. High-stress grinding abrasion – this is more severe than simple scratching that results when small hard abrasive particles are forced against a metal surface with enough force that the particle is crushed, in a grinding mode. Most often the compressive force is supplied by two metal components with the abrasive sandwiched between the two - sometimes referred to as three-body abrasion. The surface becomes scored and surface cracking can occur.

Valves

The variety of valves available for use in piping systems is extensive. This is due to the range of functions that valves perform, the diversity of fluids carried, and the varying conditions under which valves must perform these tasks. Valves can be examined under the following headings:
● Basic parts
● Functions performed by valves
● Valve types
● Installation of valves
● Specification of valves.
The main structure of the valve is the body, which contains – or to which is attached – the other parts of the valve. The main structure must possess sufficient mechanical strength and sufficient resistance to corrosion, erosion and high temperature to meet service conditions. The material from which the valve body is made is important and common materials in use include carbon steel, low-alloy steel, bronze, brass, stainless steel. The operator is the method of actuating the valve. Valves may be operated manually: by the use of handwheels, levers and chains, by geared handwheels on larger valves or by powered operation employing electric, pneumatic or hydraulic actuators. Powered actuators are normally used when:
● Rapid opening or closing is required
● The valve is operated very frequently
● Access to the valve is difficult
● The operation of the valve requires great effort
● Valve operation presents a safety hazard.
Functions performed by valves
Valves perform the following basic functions.
● They shut off the supply in a pipeline or they enable a piece of the pipeline to be isolated so that repairs to piping or equipment can be carried out faulty or damaged items can be replaced, etc. This is shut-off or stops valve.
● The throttle, regulate or restrict the flow passing along a pipeline by partially closing the area of flow through the valve.
● They redirect the flow at a branch line by changing the path along which the flow occurs.
● They protect a system against excessive pressure or sudden increases in pressure. These are safety valves or relief valves. When the pressure in a line reaches a pre-set high pressure, the valve opens and allows the pressure to escape either to the atmosphere or to another part of the system. Safety valves are
the ones that are usually used for steam, air or other gases. Relief valves are usually used for liquids.

● They enable one part of a continuous system of piping to operate at a different pressure from another part. These are pressure-reducing valves (also known as pressure regulators) and are often used in air piping to reduce the compressor or mainline pressure down to a low value for operation of low- pressure equipment.
● They prevent flow in one direction along a pipe or they allow flow in one direction only. This valve is referred to as a non-return, or check or reflux valve.

Weld Cladding

Weld cladding techniques were first developed at Strachan & Henshaw, Bristol, United Kingdom, for use on defence equipment, especially, for various parts of submarines. Through weld cladding, the composite structure is developed by the fusion welding process. All metals used as fillers may be used for weld cladding. Materials such as nickel and cobalt alloys, copper alloys, manganese alloys, alloy steels, and few composites are commonly used for weld cladding. Weld clad materials are widely used in various industries such as chemical, fertilizer, nuclear and steam power plants, food processing and petrochemical industries. Various industrial components whose base metals are weld-clad are steel pressure vessels, paper digesters, urea reactors, tube sheets and nuclear reactor containment vessels. Cladding using gas tungsten arc welding is widely used in aircraft engine components to maintain high quality. Weld cladding can be done by using various processes such as Submerged arc welding (SAW), Gas metal arc welding (GMAW), Gas tungsten arc welding (GTAW), Flux-cored arc welding (FCAW), Submerged arc strip cladding (SASC), Electro slag strip cladding (ESSC), Plasma arc welding (PAW), Explosive welding, etc. GTAW and PAW are widely used for the cladding operations, and they produce superior quality cladding because they generate high stable arc and spatter free metal transfer. Welding variables and inert gas shielding can be precisely controlled in both GTAW and PAW. Though GTAW and PAW cladding can produce excellent overlay with a variety of alloy materials, deposition rate is low compared to other processes which limit its application in industries. Submerged arc strip cladding (SASC) and Electro slag strip cladding (ESSC) is extensively used for cladding large surfaces of the heavy–wall pressure vessels. Three most important characteristics of SASC and ESSC are high deposition rate, low dilution and high deposition quality. Deposition rate in ESSC is much more than in SASC because of the absence of arc, whereas, dilution in ESSC is less compared to SASC because of the same reason. Weld cladding is widely done using flux-cored arc welding (FCAW) process due to various advantages. With properly established process parameters automation and robotization can be done easily in FCAW. Wear, corrosion and heat resistance of material surface is enhanced by plasma transferred arc (PTA) surfacing. PTA process is also considered as an advanced GTAW process used largely for overlay applications. Various advantages of PTA surfacing are very high deposition quality, high-energy concentration, narrow heat-affected zone, less weld distortion, etc. On the other side, demerits of PTA surfacing are low deposition rates, overspray, and very high equipment costs Cladding with the use of submerged arc welding (SAW) is applied for large areas, and its fusion efficiency is quite high. SAW can be easily automated and employed especially for heavy section work.

Piping Fundamentals

The piping system includes pipe, fittings, valves, and speciality components. All piping systems are
engineered to transport fluid or gas safely and reliably from one piece of equipment to another. Piping can be divided as • Small bore lines • Large bore lines As a general practice, those pipelines with nominal diameters 2” (50mm) are characterised as a small bore and preceding that as a large bore. Pipe sizes are on the basis of Diameter and Thickness. In some places, pipe size is designated by two non-dimensional numbers: Nominal Pipe Size (NPS) and schedule (SCH). Some major relationships:

• Nominal pipe size (NPS) is to describe a pipe by name only. Nominal pipe size (NPS) is generally related to the inside diameter (ID) for sizes 1/8” to 12”. For pipe sizes of 14” and beyond, the NPS is equal to the outside diameter (OD) in inches. Outside diameter (OD) and inside diameter (ID), as their names imply, refer to the pipe by their actual outside and inside measurements. The Outside diameter (OD) is the same for a given size irrespective of pipe thickness.

• The schedule belongs to the pipe wall thickness. As the number increases, the wall thickness
increases and the inside diameter (ID) is reduced.

• Nominal Bore (NB) with schedule (wall thickness) is used in British standards classification.
The main purpose of piping design is to configure and lay equipment, piping and other accessories
meeting relevant standards and statutory regulations. The piping design and engineering involve the following six (6) steps:

Selection of pipe materials according to the characteristics of the fluid and operating conditions including maximum pressures and temperatures.

• Finding economical pipe diameter and wall thickness.

• Selection of joints, fittings and components such as flanges, branch connections, extruded tees, nozzle branches etc.

• Developing piping layout and isometrics.

• Performing stress analysis as per the potential upset conditions and an allowance for those upset
conditions in the design of piping systems.

• Estimating material take-off (MTO) leading to material requisition.

The Pipe Material Specification (PMS) is the major document for piping engineers. This document
describes the physical characteristics and specific material attributes of pipe, fittings and manual valves necessary for the needs of both design and procurement. These documents are contractual to the project and those contractors that work under them. A piping specification must contain those components and information that would typically be used from job to job. The following items below provide the primary component report and notes required for a typical piping system. − Pressure/Temperature limit of the Limiting factor for Pressure/Temperature − Pipe material − Fitting type, rating and material − The flange type, rating and material − Gasket type, rating and material − Bolt & nut type and material Manual valves grouped by type − Notes − Branch chart matrix with corrosion adjustment 1.14. DESIGN FACTORS The design factors that affect piping engineering include:

• Fluid Service Categories (Type)

• Flow rate

• Corrosion rate

• Operating Pressure and Temperature All this information is available in the Process Flow Diagrams (PFD’s), Piping and Instrumentation Drawings (P&ID’s) and Piping Material Specification (PMS).

What is Quantity Surveying?

 Quantity surveying refers to the cost management, procurement and contractual issues in the supply chain and marketplace. They usually advise on cost implications of the clients’ requirements and other stakeholders’ decisions. They monitor and update initial estimates and contractual obligations as the construction progress based on additional works and variations. The practices do provide services that are focused on buildings (the architectural elements), and civil engineering now provides services that include heavy engineering, oil and gas, and building engineering services. Although the engineering services are part of buildings, it would be out of place to claim that all quantity surveyors have the required skills and knowledge to provide expert advice on building engineering services as they do for other aspects of construction. Most of the quantity surveying practices consider building engineering services a specialised duty. Most of the building clients have become uncomfortable with the inability of quantity surveyors to provide conclusive and accurate estimates for their buildings arising from using lump sum approaches to price engineering services. Today, it is common to see or hear statements like ‘M&E Quantity Surveyors’ ostensibly to mean quantity surveyor that is ‘qualified’ to offer advice on building engineering service. Many of the universities now offer a degree in building services quantity surveying which aims at providing students with a sound understanding of the principles and practices involved in the building services quantity surveying specialism, up to degree level standard, and to help them in the progression to Masters the level should they so wish. A general question is if such degrees are required considering the knowledge and skills expected of quantity surveyors in the measurement of building works. Quantity surveyors have a background rich in the dynamics of costs of construction. Arguably, such degrees are not warranted. Several studies show that quantity surveyors have generally expanded on the nature and scope of services they now provide. In order to understand this, we evaluate the levels of involvement of quantity surveyors in the procurement of building services engineering. The study aims to provide fresh knowledge on the expertise of quantity surveyors with a focus on the procurement of building engineering services. This knowledge is valuable to academic institutions that offer quantity surveying programmes, practising quantity surveyors and other players in the construction industry. Quantity surveying is universal. However, it is carried out under different names. In a few countries, quantity surveying is very much related to cost engineering, while they are also referred to as cost economists or cost consultants in other places. However, quantity surveying is not just a simple thing. As such the phrase “quantity surveying” is a catch-up term that hides a multitude of meanings. The modern quantity surveyors perform various types of services that extend beyond the services traditional quantity surveyors provide and higher institutions offering quantity-surveying programs are responding accordingly by modifying and upgrading their course content. Quantity surveyors must provide advice on the strategic planning of a project. For the construction worker, this advice affects clients’ decisions on whether to construct or not and if the client decides to construct what effect does cost have on other criteria within the clients/users value systems including time and quality, function, satisfaction, comfort and aesthetics.

What is Submerged Arc Welding?

In Submerged Arc Welding (SAW) process, the arc and the molten weld metal are covered by an envelope of molten flux and a layer of unfused granular flux particles. The arc is literally submerged in flux, as such the process is relatively free of intense radiation of heat and light. In most typical open arc welding processes the resulting welds are very clean. Like Gas Metal Arc Welding (GMAW) process, SAW process makes use of a solid wire electrode that is consumed to produce filler metal. The arc currents are usually considered to be very high (500A to 2000A). The efficiency of transfer of energy from electrode source to the workpiece is very high (usually over 90%), since losses from radiation, convection and spatter are minimal. The deposition rate along with the weld reliability is good. A reduction in Cost and improved productivity in welding operations can, therefore, generate a considerable impact on the competitiveness of various manufacturing industries. At the time of welding, joint preparation and arc efficiency are the most important factors dominating the cost and productivity of the weld. The desired amount of weld penetration must be achieved in a single pass the welding speed will be the major factor that determines the welding time. The efficiency of the arc is determined by proper penetration as well as the productivity of quality welds. The filler material is an uncoated, continuous wire electrode, that is applied to the joint along with a flow of fine-grained flux, which is supplied from a flux hopper via a tube. The electrical resistance of the electrode should be as low as possible to facilitate welding at high current and so the welding current Is supplied to the electrode through contacts very close to the arc and immediately above it. The arc burns in a cavity, which it is filled with gas and metal vapour. The top of the cavity is formed by molten flux. The solidified weld and the solidified flux covers the weld in a thin layer and which must subsequently be removed. The excess flux can be reused again. It also has a thermal insulating effect that reduces heat losses from the arc. As a result, more of the input energy is there for the process of welding. There are greater thermal efficiency and a faster rate of welding. It has been found that there is greater thermal efficiency in submerged arc welding that shields metal arc. The thickness of the part is considered important in developing the desired penetration. The procedure for welding stainless does not show much difference in stool steel does not differ greatly from that of welding mild steel. The material being used is expensive and necessary conditions of service are usually required necessitating extra precautions and attention to detail. Stainless steel can be welded using either A C or DC with as short an Arc as possible in order to overcome any possibility of alloy loss across the arc. When using AC, slightly higher current and setting may be required. While welding in the flat position, stringer beads should be used and, if weaving is required, this should be limited to two times the electrode diameter. The heat input, which affects the corrosion resistance and leads to excessive distortion, should be limited by using the correct electrode diameter to give the required bead profile and properties at the maximum travel speed.