Steel Pipeline Systems [Part.2]

Coupling Procedures.
a. For 8-inch Steel Tubing. Procedures for this tubing, because of weight (210-pound tubing), are different than for lighter pipelines. A saddle-type carrying bar (Figure B-2) and one extra person in the crew are required for constructing the 8-inch tubing pipeline. This extra person is a second helper who assists in raising the new section onto the lineup cage and in lowering it. The rest of the coupling operations are the same as those for a 4- or 6-inch line. Except for size, the 8-inch lineup cage and pipe-cleaner swab are identical to those used on the smaller pipe.

Coupling procedures for 8-inch steel tubing are as follows:
■The second helper assists the wrenchman's helper to raise their end of the tubing section and guide it onto the lineup cage, while the stabber and jackman handle the other end.

■The second helper moves to the other end and assists the jackman and stabber in aligning the section, as directed by the wrenchman.

■The second helper assists the jackman and stabber in lowering the new end of the pipeline on the lazy board. Then the second helper assists the wrenchman's helper with the next section.

For 8- and 12-Inch Standard Steel Pipe and 12-Inch Steel Tubing. Do not manually handle pipe sections heavier than the 6-inch (300-pound) standard-weight pipe. Use powered equipment to off-load the pipe and couple one section at a time. You can stockpile the pipe along the pipeline trace. If you do, use a pipelayer (Figure B-3) to handle the pipe. (The pipelayer is a commercial piece of equipment that must be leased.)

Swabbing and Cleaning. The swabber and pipe-end cleaner swab all of the pipe on a load, one row at a time, in a single operation. (They can swab the pipe while it is still on the truck or in a stockpile.) With one man at each end, they insert a snake in either outside pipe of the top row and pass it through to the other end. The man at the end where the snake is coming through pulls it through the first pipe and simultaneously feeds the snake back through the next pipe in the row. The men repeat this operation until they swab all the pipes (Figure B-4).

(2) Moving the Pipe. The pipe is picked in the middle with an automatic clam-type release hook attached to the hoisting line of the stringing boom. The pipe joint is first raised only a few inches from the pipe. The swabber and pipe-end cleaner, working at opposite ends, clean and file the pipe land and groove on each end at the same time. At the same time, the wrenchman and helper (one team) and the jackman and stabber (another team) construct cribbing of 4- by 4-inch by 3-footlong blocks. This cribbing takes the place of the lazy board and pipe jack. Each of the blocks is tied together with rope. Doing so allows the wrenchman's helper to drag one cribbing set at a time when moving it to the next location.

(3) Positioning the Pipe. After the pipe ends are cleaned, the pipe section is swung into approximate alignment on the pipeline. The stabber inserts the lineup-cage snake through it (only one snake is used). The jackman and wrenchman's helper guide the pipe joint into position on the lineup cage protruding from the end of the line. The stringing-boom operator raises or lowers the load and extends or retracts the boom, as directed by the stabber or wrenchman. Once aligned, the jackman keeps the joint aligned by leaning or shoving against the end.

(4) Installing the Coupling. After tightening the coupling, the crew lifts the pipeline high enough so they can pull the cribbing stack out from under the pipeline and drag it forward (about 40 feet) to the far end of where they will install the next section. The jackman lowers the pipeline and guides it onto the cribbing stack. At the same time the stabber places the gasket inside out on the end of the pipeline. As soon as the coupling is tightened, the stabber pulls the lineup cage forward. The stabber erects the cribbing stacks while couplings are installed. As he moves forward, the wrenchman releases the pipe lifting tongs so that the pipe-stringing boom will swing back to the bolster truck for the next pipe section.

Steel Pipeline Systems [Part.1]

Steel Pipe. Steel pipe (light- and standard-gauge wall thickness) is available in 20-foot lengths with diameters of 4, 6, and 8 inches. Steel pipe is coupled using a standard, two-piece split-ring coupling. The coupling uses two half-moon sections, which are bolted together over a one-piece gasket. The average time required to couple together two sections of steel pipe is 5 minutes.

Lightweight Steel Grooved Pipe. This pipe is made of light gauge steel with API STD5L pipe nipples welded to each end. The pipe ends are single-grooved for use with bolted couplings. This pipe comes in 20-foot sections with 4-, 6-, 8-, and 12-inch nominal IDs. Because of its thin wall, lightweight steel pipe should not be buried nor used for submerged stream crossings or in populated areas and locations where fire and damage hazards are acute.

Standard-Weight Steel (API STD5L) Pipe. This regular commercial-type pipe, which is manufactured to the standards of the API, is used when lightweight pipe or tubing is unavailable or unsuitable. The pipe comes in 20-foot sections grooved for coupling and in random lengths and diameters beveled for welding.

Bolted Coupling. This is a standard, split-ring, groove-type coupling (Figure B-1). It consists of two housing segments; two bolts and nuts; and a synthetic-rubber, oil-resistant, self-sealing gasket. The coupling and gasket are designed so that the pipe joint seals under pressure and vacuum. The coupling provides a sufficient amount of angular deflection and slack adjustment for expansion and contraction of the line between adjacent joints.

When using bolted couplings, the crew consists of a crew leader, wrenchman, wrenchman's helper, stabber, jackman, swabber, and pipe-end cleaner. The bolted-coupling crew will normally require--

■Two 20-inch hinged socket wrench handles. ■Two sockets to fit size of pipeline coupling nut and wrench. ■File. ■Dauber brush. ■Lazy board. ■Two pipeline jacks with two snakes. ■Pipeline cleaner swab with one snake. ■Wooden blocks (4 by 4 by 10 inches) with carrying rope attached. ■Full half-gallon bucket or one-gallon bucket half filled with GAA grease. ■Cleaning rags.

Pipe Saw, 8-Inch Capacity for Hazardous Locations. This is a reciprocating-type saw powered by an air motor. You can cut steel, cast iron, and stainless or alloy steel pipe as well as bar stock structural and rail. Use this saw to cut out a damaged portion of pipeline when operating in hazardous locations. You can operate when clearances are at minimum and you can make a straight, right-angle cut.

Tapping Machine. This machine is used for tapping into a pressurized pipeline to establish a service tap or to install a pressure-relief device. This operation can be done without shutting down the pipeline system. The machine uses a hole saw; a holder-pilot performs the cutting operation. He retains the separated pipe after he completes the cut and allows for its removal.
The tapping machine is lightweight and easy to operate and has an adjustable automatic-feed rate for any cutting condition. The advance rate for cutting is set by the feed-adjustment knob. This knob engages a friction-type clutch that automatically regulates the feed rate. The operator loosens (slow feed) or tightens (faster feed) the feed-adjustment knob to obtain the correct amount of force for the task. The machine comes with a ratchet crank for manual operation.

Deadweight Tester. This tester is used to calibrate pressure gauges, verify the set points of spring-loaded relief valves, and provide precise pressure readings for pipelines. The tester uses known weights that directly correlate to known pressure gauges and the verification of set points for spring-loaded relief valves.

Valves

VALVES [Lesson 1]

Process Valve Types And Applications
Valves are used in both domestic and industrial situations to control the flow of liquids, solids and gases.

The most common and familiar valves are the taps used in the home to control the hot and cold water. In the oil industry, valves are a major element in the control of operations. In general, valves are used for one or more of three main purposes:
1. To control the rate of flow (throttle);
2. To shut off/permit flow (ON/OFF function);
3. To isolate systems and protect products.

There are a wide variety of valve types and designs available from many suppliers in a wide range of materials; the main types and their uses are
- Gate Valve: Used for shut off - ON/OFF function.
- Ball/Plug Valves: Used for shut off - ON/OFF function
- Globe Valves: Used for control of flow and shut off.
- Butterfly Valves: Used for control of flow and shut off.
- Relief Valves: Spring loaded to open at a given pressure, and used to protect systems from over-pressure.
- Check Valves: To allow flow in one direction only.
- Fusible Link Valves/Piston Operated Valves: Quick acting and used for emergency shut off.
- Twin Sea valves: Used when tight shut off required.
- Semi-Needle Valves: Used in conjunction instruments to bleed off part of the flow.
- Ball Check Valves: Used with gauge glasses as safety precaution.

There are other less commonly used types of valves.
The actual construction/design of gate valves, for example, may vary widely depending on its application,the materials used, or the manufacturer’s own special features. The basic principle, however, will be the same.

Valves can be specially made to work at high or low temperatures (cryogenic), or to very high standards for use in explosive atmospheres, or when no leakage is permissible.

Design Features

1. Internal Sealing Systems And Materials
All valves are prone to leakage as it is difficult to obtain a perfect seal, although the use of special seal materials and designs can have very good result If high security is required, use can be made of two valves in series, one to act as the main valve and the second as a back-up should the first fail.

Some valves have bleed holes installed to detect leakage across the seal. If two valves are used together, a bleed hole may be fitted in the pipe between them, which can be opened when the valves are closed to drain any leakage. (Block and Bleed valves)

2. Body/Housing Materials
A wide range of materials is used in valve manufacture, the particular material depending largely on the fluids to be handled. Iron and steel are mainly used for oil/petroleum applications with most valves being made of mild or alloy steel. Brass valves are used for water (as well as cast iron, steel and other alloys).

Stainless steel is used for acids and other corrosive liquids. Bronze is also a commonly used material which can cope with most liquids.

3. External Sealing Systems And Materials
As well as the main seal between valve and disc, wedge, etc. there are other seals required to prevent external leaks. Gaskets or ‘0’ rings are used between surfaces such as flanges, where no relative movement takes place. The main problems occur around the valve stem, which both rotates and, in some cases, moves vertically as well.

Special glands or packings are used which can be compressed by gland nuts to increase sealing. Special materials have to be used in corrosive applications, but an asbestos based fibre is a commonly used packing material with PTFE/Teflon being increasingly common. ‘O’ rings can also be used as shaft seals and are generally made of rubber.

4. Actuation of Valves
Many smaller valves are hand operated if they are accessible. Larger valves require power actuators and inaccessible valves of all types require some form of mechanical or electrical actuator. Pneumatic (compressed air) and hydraulic cylinders and mechanisms are widely used in larger applications. Smaller valves can be operated with solenoids, but larger valves require more complex motors and mechanisms for electrical power operation.

5. Standards of Manufacture
There are many standards to which valves can be made:
• Metric/Imperial dimensions;
• British Standards BS;
• German Standards DIN;
• US Standards ANSI (previously ASA)
• American Petroleum Institution API.

Care must be taken that valves, flanges, etc. and other equipment are compatible, or leakage may occur.
API flanges and other equipment are commonly used in the oil industry. The standards lay down performance requirements as well as dimensions and material. Valves are rated according to the maximum pressure and temperature at which they can safely be used.

6. Quick Closing Valves
Quick closing valves can be installed in pipelines and systems to isolate sections in case of fire, leakage or other emergencies.

A spring is usually used to operate the valve and can be released by a number of methods:
• Fire melts fusible link;
• Remote manual cable;
• Air operated actuating cylinder;
• Electrical solenoid, etc.

If the valve can be installed so that the line pressure will help to close it, this will increase the sealing capability. Swinging check valves are often used as the basis of a quick closing valve, although ball valves, plug valves and butterfly valves are also suitable.

Sizing Of Pipelines

SIZING OF PIPELINES

Oil Pipelines
Pumping a specified quantity of a given oil over a given distance may be achieved by using a large diameter pipe with a small pressure drop, or small diameter pipe with a greater pressure drop.

The first alternative will tend to a higher capital cost with lower running costs. It is necessary to strike an economic balance between these two.

There are no hard and fast rules, which can be laid down for achieving this balance. For instance, a pumping station in a populated area may consist of a simple building, involving the provision of electrically driven pumps, taking power from outside sources and little else. To obtain the same pumping power in remote or undeveloped countries would involve a considerably more complicated and expensive installation. Obviously in this latter case, it is desirable to reduce the number of pumping stations at the cost of using larger diameter piping.

Similarly, the cost of the pipeline will vary considerably, depending upon circumstances. It will be costly in highly industrialised areas, environmentally sensitive areas, offshore or in hostile, mountainous or swamp areas; cheaper in flat, soft but firm, undeveloped terrain.

Gas Pipelines
Sizing problems encountered in gas lines differ considerably from those of oil lines. A simplification results from the negligible weight of the gas as the pressure in the line is virtually independent of the ground elevation on the other hand, the compressibility of gas introduces the complication of the density decreasing and consequently the volume rate of flow increasing in the direction of flow. In an oil line of constant diameter laid on level ground, the pressure decreases uniformly with distance and the velocity stays constant whereas, in a gas line, the velocity increases as the pressure gradient decreases with an exponential, which becomes progressively steeper.

The characteristics of pumps and compressors also determine the site of any pipeline booster stations as well as the initial pipeline conditions which have to be met Pumps need to be sited in positions where they are receiving the crude oil at a pressure greater than the vapour pressure of the crude oil, whereas compressors have to be sited at a location where both the pressure and velocity of the gas are at optimum conditions.