Hot tapping, or pressure tapping, is the method of making a connection to existing

piping Within industry, piping is a system of pipes used to convey fluids (liquids and gases) from one location to another. The engineering discipline of piping design studies the efficient transport of fluid. Industrial process piping (and accomp ...

pressure vessel A pressure vessel is a container designed to hold gases or liquids at a pressure substantially different from the ambient pressure. Construction methods and materials may be chosen to suit the pressure application, and will depend on the size o ...

s without the interrupting or emptying of that section of pipe or vessel. This means that a pipe or tank can continue to be in operation whilst maintenance or modifications are being done to it. The process is also used to drain off pressurized casing fluids and add test points or various sensors such as temperature and pressure. Hot taps can range from a ½ inch hole designed for something as simple as quality control testing, up to a 48-inch tap for the installation of a variety of ports, valves, t-sections or other pipes. Hot Tap Procedures: A. A hot tap saddle, service saddle or welded threadolet, valve installed, assembly is pressure tested and hot tap machine attached. B. Valve opened, hot tap completed, coupon or cut portion retained by latches on pilot drill. Pressure is contained within the hot tapping machine. C. Cutter and coupon retracted and valve closed. Fluid is drained and hot tapping machine is removed. The tapped valve is now ready for the contractor's tie-in or IFT's linestop/stopple equipment to be inserted. Hot tapping is also the first procedure in line stopping, where a hole saw is used to make an opening in the pipe, so a line plugging head can be inserted. Situations in which welding operations are prohibited on equipment which contains: * Mixtures of gases or vapours within their flammable range or which may become flammable as a result of heat input in welding operations. * Substances which may undergo reaction or decomposition leading to a dangerous increase in pressure, explosion or attack on metal. In this context, attention is drawn to the possibility that under certain combinations of concentration, temperature and pressure, acetylene, ethylene and other unsaturated hydrocarbons may decompose explosively, initiated by a welding hot spot. * Oxygen-enriched atmospheres in the presence of hydrocarbons which may be present either in the atmosphere or deposited on the inside surface of the equipment or pipe. * Compressed air in the presence of hydrocarbons which may be present either in the air or deposited on the inside surfaces of the equipment or pipe. * Gaseous mixtures in which the partial pressure of hydrogen exceeds 700 kPa gauge, except where evidence from tests has demonstrated that hot-tapping can be done safely. Based on the above, welding on equipment or pipe which contains hazardous substances or conditions as listed below (even in small quantities) shall not be performed unless positive evidence has been obtained that welding/hot tapping can be applied safely. Substances *

Acetylene Acetylene (Chemical nomenclature, systematic name: ethyne) is a chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is u ...

Acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not class ...

* Butadiene * Caustic soda* *

Chlorine Chlorine is a chemical element; it has Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between ...

Compressed air Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air in vehicle tires and shock absorbers are commonly used for improved traction and reduced vibration. Compressed air is an important medium for t ...

at a pressure in excess of 3000 kPa gauge; *

Ethylene Ethylene (IUPAC name: ethene) is a hydrocarbon which has the formula or . It is a colourless, flammable gas with a faint "sweet and musky" odour when pure. It is the simplest alkene (a hydrocarbon with carbon–carbon bond, carbon–carbon doub ...

Ethylene oxide Ethylene oxide is an organic compound with the chemical formula, formula . It is a cyclic ether and the simplest epoxide: a three-membered ring (chemistry), ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless ...

* Fat/lean DEA/MEA; * High pressure steam (pressure in excess of 5000 kPa (ga)) * Hydraulic Oil *

Hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

(partial pressure in excess of 700 kPa (ga)) *

Hydrogen sulphide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist Ca ...

* *

Hydrofluoric acid Hydrofluoric acid is a solution of hydrogen fluoride (HF) in water. Solutions of HF are colorless, acidic and highly corrosive. A common concentration is 49% (48–52%) but there are also stronger solutions (e.g. 70%) and pure HF has a boiling p ...

Oxygen Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...

Propene Propylene, also known as propene, is an unsaturated organic compound with the chemical formula . It has one double bond, and is the second simplest member of the alkene class of hydrocarbons. It is a colorless gas with a faint petroleum-like od ...

* Propene oxide * Sulphuric acid * Toxic substances.* Constraints based on general hazard in the event of line puncturing during welding, not the welding process. Conditions: * Vacuum conditions; * Dissolved hydrogen in the pipe wall (e.g. due to service history); * Pyrophoric scale deposits. Note: The above list is not exhaustive, but gives an indication only.

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Further reading