System and method for treating flexible pipes

Abstract

A system and method for treating pipes according to which the flexibility of the pipe is increased or maintained, or at least any decreases in the flexibility of the pipe is minimized, in relatively low temperature environments.

What is claimed is:  
     
         1 . A method of treating a flexible pipe to prevent or minimize increase in its stiffness in relatively low temperature environments, the method comprising adding rubber modifiers to the material forming the pipe to prevent or minimize any increase in the modulus of elasticity of the plastic material due to the low temperature.  
     
     
         2 . The method of  claim 1  wherein the pipe is formed by at least one layer of plastic material.  
     
     
         3 . The method of  claim 1  wherein the pipe is formed by two or more layers of plastic material and wherein the rubber modifiers are added to at least one of the layers.  
     
     
         4 . The method of  claim 1  wherein the rubber modifiers are added in sufficient quantities to reduce the hardness of the pipe to a maximum value of 50.  
     
     
         5 . The method of  claim 1  wherein the rubber modifiers are in the form of thermoplastic elastomers.  
     
     
         6 . The method of  claim 5  wherein the thermoplastic elastomers are a blend of two or more polymer systems, each with its own phase.  
     
     
         7 . The method of  claim 6  wherein one of the polymer systems is a polyolefin.  
     
     
         8 . The method of  claim 7  wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, and polyvinylchloride.  
     
     
         9 . The method of  claim 6  wherein one of the polymer systems is an elastomer.  
     
     
         10 . The method of  claim 9  wherein the elastomer is selected from the group consisting of ethylene-propylene rubber and nitrile-butadiene rubber.  
     
     
         11 . The method of  claim 1  wherein the modifiers are in the form of thermoplastic vulcanates.  
     
     
         12 . The method of  claim 11  wherein the modifiers comprise thermoplastic elastomers and thermoplastic vulcanates.  
     
     
         13 . The method of  claim 1  further comprising storing the pipe in an environment in which the temperature is no less than approximately 5° C. to reduce the stiffness of the pipe when compared to a pipe that is stored in an environment greater than 5° C.  
     
     
         14 . The method of  claim 1  further comprising heating the pipe to a temperature of no less than approximately 5° C. to reduce the stiffness of the pipe when compared to a pipe that is at a temperature less than 5° C.  
     
     
         15 . The method of  claim 14  further comprising the step of storing the heated pipe on a storage drum, the diameter of which is such that the maximum strain due to the bending of the pipe on the drum is no greater than five percent when compared to the pipe when it is not bent.  
     
     
         16 . The method of  claim 1  further comprising the step of storing the pipe on a storage drum, the diameter of which is such that the maximum strain due to the bending of the pipe on the drum is no greater than five percent when compared to the pipe when it is not bent.  
     
     
         17 . A method of treating a flexible pipe to prevent or minimize increase in its stiffness in relatively low temperature environments, the method comprising storing the pipe in an environment in which the temperature is no less than approximately 5° C. to reduce the stiffness of the pipe when compared to a pipe that is stored in an environment greater than 5° C.  
     
     
         18 . The method of  claim 17  wherein the pipe is formed, at least in part, by a plastic material, and further comprising the step of adding rubber modifiers to the material forming the pipe to prevent or minimize any increase in the modulus of elasticity of the plastic material due to the low temperature.  
     
     
         19 . The method of  claim 17  further comprising storing the pipe on a storage drum in the environment, the diameter of the drum being such that the maximum strain due to the bending of the pipe on the drum is no greater than five percent when compared to the pipe if it is not bent.  
     
     
         20 . A method of treating a flexible pipe to prevent or minimize increase in its stiffness in relatively low temperature environments, the method comprising heating the pipe to a temperature of no less than approximately 5° C. to reduce the stiffness of the pipe when compared to a pipe that is at a temperature less than 5° C.  
     
     
         21 . The method of  claim 20  wherein the step of heating comprises circulating relatively warm water or relatively warm air through the pipe.  
     
     
         22 . The method of  claim 20  wherein the pipe is formed, at least in part, by a plastic material, and further comprising adding rubber modifiers to the plastic material to prevent or minimize any increase in the modulus of elasticity of the plastic material due to the low temperature.  
     
     
         23 . The method of  claim 20  further comprising storing the heated pipe a storage drum, the diameter of which is such that the maximum strain due to the bending of the pipe on the drum is no greater than five percent when compared to the pipe if it is not bent.  
     
     
         24 . A method of treating a flexible pipe to prevent or minimize increase in its stiffness in relatively low temperature environments, the method comprising the step of storing the pipe on a storage drum, the diameter of which is such that the maximum strain due to the bending of the pipe on the drum is no greater than five percent when compared to the pipe if it is not bent.  
     
     
         25 . The method of  claim 24  wherein the step of storing eliminates any stress relaxation that would be caused if the diameter of the storage drum causes a maximum strain in excess of five percent.  
     
     
         26 . The method of  claim 24  wherein the strain is calculated according to the following formula:  
       ε d/D    where 
 ε=the strain at the outer fiber of the material, equal to the elongation per of unit length at the outer fiber of the layer  
 d=the outer diameter of the pipe, and  
 D=the diameter of the centerline of the pipe in the storage condition.  
   
     
     
         27 . The method of  claim 24  wherein the pipe is formed, at least in part, by a plastic material, and further comprising adding rubber modifiers to the material to prevent or minimize any increase in the modulus of elasticity of the plastic due to the low temperature.  
     
     
         28 . The method of  claim 24  further comprising storing the pipe in an, environment in which the temperature is no less than approximately 5° C. to reduce the stiffness of the pipe when compared to a pipe that is stored in an environment greater than 5° C.  
     
     
         29 . The method of  claim 28  wherein the step of storing occurs after the temperature of the pipe is at least 5° C.  
     
     
         30 . The method of  claim 24  further comprising heating the pipe to a temperature of no less than approximately 5° C. to reduce the stiffness of the pipe when compared to a pipe that is at a temperature less than 5° C.  
     
     
         31 . The method of  claim 30  wherein the step of heating is before the step of storing.