Pipes and tubular conduits – Distinct layers – Reinforced
Reexamination Certificate
1999-03-30
2001-05-15
Hook, James (Department: 3752)
Pipes and tubular conduits
Distinct layers
Reinforced
C138S155000, C138S109000, C138SDIG008, C169S016000, C239S209000
Reexamination Certificate
active
06230751
ABSTRACT:
The present invention relates to a corrosion and fire-resistant pipe system suitable for sprinkler systems and the like in offshore industries and on both military and civilian seagoing vessels and also as sprinkler systems in public buildings and industrial buildings.
Conventional steel pipe systems are not suitable for transporting liquids that are as aggressive as sea water and industrial waste solutions and other, similar waste liquids. In offshore industries for instance where sea water pipelines are required to a great extent for cooling and fire extinguishing purposes (sprinkler systems), the replacement of traditional steel qualities with other, hopefully more suitable materials has been pursued for quite some time. In this regard, efforts have been made to switch to more expensive metallic materials, such as steel qualities that are more highly alloyed, e.g. SMO steel which is an acid-proof Cr—Ni steel that contains about 6% Mo, and more sophisticated metals or alloys, for instance titanium and different Cr—Ni alloys.
Tests have also been made with plastic materials, wherein fibreglass-reinforced epoxy pipes have been tested as line pipes for conducting sea water. Although such plastic pipes have significant advantages over steel pipes with regard to their corrosion resistance, they are unsuitable as replacements for steel pipes in all applications and primarily within the offshore and seagoing vessel sector, for other reasons. For instance, such pipes are not fire-resistant, but, on the contrary, inflammable and combustible and therefore generate smoke and toxic gases and need to be provided with separate fire insulation even in simple applications. Plastic pipes also have a limited mechanical resistance, for instance against external blows and knocks and against so-called water hammer that occur with abrupt, powerful pressure changes of the water in the pipe system, caused, for instance, by the closing and opening of valves, which is, of course, also a significant disadvantage in many contexts. Metallic pipes also have poor resistance against water hammer due to their inability to expand quickly.
These more expensive metallic materials are far more suited for the purposes in question than plastic pipes, with the exception of their resistance to water hammer as mentioned above. However, since the material is extremely expensive the running metre cost of such material is high and its usefulness is restricted to the most advanced applications and to use in particularly demanding systems. However, all metal-based pipe systems are still encumbered with a number of serious problems. Firstly, none of the tested qualities is completely free from corrosion problems in spite of everything, and exposure to temperatures that are slightly higher than normal room temperatures can have serious consequences. Secondly, these materials require extensive welding work and/or other similar “hot work” when assembling, installing and servicing pipe systems whose pipes are made from such materials, which, from the aspect of safety, is something that one wishes to avoid to the greatest possible extent, particularly in the offshore and ship sector. In addition to the problem presented by the actual heat in such work, there is always the risk of gas leakage in oil and gas recovery systems. It is therefore always necessary to stop production during work which entails the use of open flames or the like in offshore installation work. Naturally, this results in significant costs and also in serious drawbacks and production disturbances.
In the case of fire, different high heat flux densities occur together with high temperatures, depending on the nature of the fire. In the case of a difficult fire that involves the combustion of solid fuels, so-called cellulosic fire, the temperature in the region of the fire increases continuously and will be about 900° C. after 60 minutes, about 1050° C. after 120 minutes and a highest temperature of about 1150° C. will be reached after 240 minutes. The heat flux density that prevails at the same time is, on average, about 60 kW/m
2
, and a maximum heat flux density of about 100 kW/m
2
can be reached. In hydrocarbon pool fires or the like, the temperature rises much more rapidly and a maximum temperature of about 1150° C. will be reached after 20 minutes. The heat flux density is much higher than in the case of cellulose fires, on average about 200 kW/m
2
, with a highest peak of about 225 kW/m
2
. The worst type of fire is the so-called jet fire, which may occur when natural gas and different condensates burn under high pressure, such as in natural gas reservoirs, either offshore or on land. Offshore platforms and corresponding installations on land can be the subject of such fires and such fires have, unfortunately, occurred with catastrophic consequences and the loss of many lives. In the case of jet fires, the temperature rises very quickly (10-15 seconds) to a magnitude of 1300-1400° C., at which the fire has a typical heat flux density of 360 kW/m
2
and limited up to about 500 kW/m
2
.
Against this background, the recovery of oil and gas offshore and on land places very high demands on fire safety and fire protection, and offshore platforms are thus equipped with advanced sprinkler systems based on pumping large volumes of water from the sea, said systems having branches in all parts of the platforms.
Particularly in the offshore and shipyard industry, there has long been expressed the need for corrosion-resistant and fire-resistant pipe systems that can be used, for instance, on oil platforms, military vessels and oil tankers, where particularly strict and advanced requirements are found with respect to fire resistance and corrosion resistance and where there is a desire to greatly reduce or preferably totally eliminate the need to carry out welding work or other hot work.
The object of the present invention is to provide a corrosion-resistant and fire-resistant pipe system for the most advanced applications and with which the aforesaid problems associated with materials used hitherto are greatly reduced or even totally eliminated in certain cases, and which is also able to afford further important advantages with respect to its installation and re-construction, by using the specific properties of the pipe material used, for instance better cold-forming properties.
The inventive pipe system is characterized to this end by the features set forth in the following Claims. The pipe system thus includes rigid and cold-formable pipe sections or lengths that include one or more tubular rubber layers and reinforcing layers which surround or embrace one or more of said tubular rubber layers and consist of wires or ribbons that are wound, braided, knitted or that are made to cross one another in some other way and each of which defines a winding or spiralling angle with the longitudinal axis of respective pipe sections such as to impart the greatest possible strength to the reinforced, tubular rubber layers and, when applicable, to branch connections for connecting one pipe section to another pipe section in a multi-path coupling. By “rigid and cold-formable pipe sections” is meant here that said sections can only be bent under plastic deformation of the pipe sections. In this context, it is worth mentioning that pipes that can be bent without any plastic deformation are referred to as “hoses” by way of definition.
The reinforcement may be encapsulated in one or more rubber layers or may consist in one or more separate layers between rubber layers. The reinforcing material itself is not critical, since the most important thing in this connection is to achieve the greatest possible stability and strength and also to achieve a high flexural rigidity, or bending resistance, which enables the pipe to deform plastically and which differentiates said pipe from a “hose”, as indicated above. It is known from the manufacture of reinforced hose that when the winding angle, or the spiralling angle as it can also be called, i.e. the acute angle that each reinforcing wire o
Burns Doane Swecker & Mathis L.L.P.
Hook James
Trelleborg Viking AS
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