WO2007064774A1

WO2007064774A1 - Method for insulating a steam pipe in situ

Info

Publication number: WO2007064774A1
Application number: PCT/US2006/045809
Authority: WO
Inventors: Alex Schmidt
Original assignee: Thermal Science Technologies, Llc
Priority date: 2005-11-30
Filing date: 2006-11-30
Publication date: 2007-06-07

Abstract

A method and apparatus for insulating underground steam pipe in situ includes the steps of creating at least one hole in the ground, inserting a liner into the hole, using a drill string to drill a hole in the conduit, inserting a tubing into the liner so that a first end of the tubing is positioned next to the pipe and a second end of the tubing is attached to a pumping system. The foam is then pumped through the tubing around the pipe and then the tubing is removed and the foam is allowed to cure and become rigid, thereby functioning as insulation. The plastic foam may be a polyisocyanurate or a urethane-modified polyisocyanurate.

Description

Method for Insulating a Steam Pipe In Situ

FIELD OF INVENTION

The present invention relates generally to a method for insulating steam pipe and, more particularly, to a method for insulating installed underground steam pipe and for performing the insulating process underground.

BACKGROUND OF THE INVENTION

Underground steam pipe systems are very necessary in most cities. These systems provide heat and energy to commercial and residential spaces alike. The pipe through which the steam flows can range anywhere from two to twenty-four inches in diameter and is typically made of steel. When steam passes through the steel pipe, the temperature of the pipe rises to 350°-450°F. Because metal is a good conductor of heat, a significant amount of heat would be expected to be dissipated or lost through the pipe, resulting in inefficiency. Therefore, in order to reduce heat dissipation, steel steam pipe is typically insulated.

Foamed plastics are often used, for insulation purposes, at temperatures of up to 120 ° C, because of their low density, low thermal conductivity and resistance to moisture. Foamed polyurethane, for example, has an aged thermal conductivity of 0.016 W/m ^• K at 23 ° C. Other foamed plastics include polystyrene, polyvinyl chloride (PVC), and phenolic foams. These foamed plastics are "cured" or "cast" and are transformed into rigid structures. Objects of various shapes can be made simply by casting the foam inside a mold which is shaped to make the desired article. For steam pipe insulation applications, foamed plastics are transformed or "precast" into rigid half-cylinders or blocks. These half- cylinders are inserted into the annular area between the steel steam pipe and concrete or tile conduit. Typically, this process is done before or during laying the pipe underground.

U.S. Patent No. 5,732,742, entitled "Method for re-insulating installed steam pipe in situ," assigned to the same assignee as the instant invention and hereby incorporated herein by reference in its entirety, teaches repairing deteriorated insulation by injecting plastic foam insulation (polyisocyanurate foam) into the annular space. The process for re-insulating underground steam pipe in situ first involves creating at least one hole in a suitable location in the ground and inserting a liner into the hole. Then, using any suitable tool such as a drill, torch or jack hammer, a hole is opened into the conduit to allow insertion of a tubing through the conduit (through the liner). A first end of the tubing is positioned through the hold and proximate to the pipe and a second end of the tubing is attached to a pumping system. The foam is then pumped through the tubing around the pipe. Once the tubing is removed and the foam is allowed to cure it becomes a rigid insulation for the pipe. Industrial application of the insulating process typically uses a closed cell, high temperature, plastic foam insulation (polyisocyanurate foam) as a means of re-insulating the underground lines. The present method, also known as "Condufill™", uses a high temperature Teflon hose to apply the insulating foam through a vacuum, excavation or a manhole.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a method and apparatus for insulating underground, metal steam pipe in situ.

According to one embodiment of the present invention, a method is provided for the insulation of underground steam pipe in which insulating foam is deposited around installed steam pipe.

In another embodiment, the invention comprises pumping uncured plastic foam into the annular space between installed underground steam pipe and surrounding conduit and subsequently causing the foam to cure and become rigid.

In a still further aspect, the method for in-place insulation of an underground steam pipe comprises creating at least one hole in the ground, inserting tubing into the hole so that a first end of the tubing is positioned next to the pipe and a second end of the tubing is attached to a pumping system. The foam is then pumped through the tubing around the pipe and then the tubing is removed and the foam is allowed to cure and become rigid, thereby functioning as insulation.

These and other features, aspects and advantages of the present invention will become better understood from the description herein, appended claims, and accompanying drawings as hereafter described.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For simplicity and illustrative purposes, the principles of the present invention are described by referring to various exemplary embodiments thereof. Although the preferred embodiments of the invention are particularly disclosed herein, one of ordinary skill in the art will readily recognize that the same principles are equally applicable to, and can be implemented in other systems, and that any such variation would be within such modifications that do not part from the scope of the present invention. Before explaining the disclosed embodiments of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of any particular arrangement shown, since the invention is capable of other embodiments. The terminology used herein is for the purpose of description and not of limitation. Further, although certain methods are described with reference to certain steps that are presented herein in certain order, in many instances, these steps may be performed in any order as would be appreciated by one skilled in the art, and the methods are not limited to the particular arrangement of steps disclosed herein.

The present invention addresses the aforementioned needs associated with application of insulation to underground piping. The new insulation performs up to a temperature of 450°F. Moreover, the inventive process has the advantages of not requiring the digging up of existing pipe. The inventive process also has the advantage of eliminating the cost of purchasing and installing new conduit and pre-cast rigid foam insulation material. In addition to the cost savings from the process itself, another advantage of the present invention is that the steam transmission system does not have to be shut down during the re- insulation process. A further advantage of the invention is that it can be practiced year round. Yet another advantage of the invention is that up to 1,000 feet of pipe can be insulated or re-insulated at a time. This is because the inventive method provides the option of preparing multiple holes in advance and sequentially injecting the plastic foam into the multiple holes along up to 1,000 feet of conduit. Thus, the inventive method is highly time efficient.

Moreover, according to the present invention, the foam used is flowable, thus, it can more uniformly fill the area between the pipe and conduit and insulate more efficiently as compared to the previously proposed methods. Any remaining original insulation does not have to be removed, rather it can remain in place and the new foam is pumped around it. When the new foam cures, the old insulation becomes part of the new rigid foam structure.

Generally, the plastic insulating foam is a polyurethane. Other newer types of plastic foams such as polyisocyanurates, polystyrene, PVC and phenolic foams can be used in practicing the invention. In particular, recently developed urethane-modified rigid polyisocyanurate foams exhibit superior thermal stability and combustibility characteristics. Polyurethane -processing equipment can be used. The present invention addresses, among others, the need for delivering through an injection hose a well blended mixture of chemical reactants, at the proper flow rate and temperature, for in situ application of the polyisocyanurate insulation to existing pipe systems.

The plastic insulating foam may consist of two or three components which must be mixed before pumping. For example, a polyurethane foam may have one component which is an isocyanate and one component which is an amine. These two components must be mixed together before pumping. A typical polyurethane foam formulation is shown in Table 1. A typical polyisocyanurate foam formulation is shown in Table 2.

Table 1- Polyurethane foam formulation.

IL. ii ^■>"' 1..J¹ "...» '!■^■■!! ιi...]t ..- ,„..;> n,,,ri \t,,,\t PCT/US2006/045809

A preferred embodiment of the present invention wherein the steam pipe is encased in conduit and has an annular space between the pipe and the conduit provides for the following steps: creating at least one hole in the ground; lowering a drill into the hole; drilling a hole in the conduit; inserting tubing into the hole in the conduit so that a first end of the tubing is positioned next to the pipe and a second end of the tubing is attached to a pumping means; pumping the foam through the tubing so that the foam fills the annular space around the pipe; removing the tubing; and allowing the foam to cure and become rigid thereby functioning as insulation. Further, a plastic casing or liner of about twelve inches in diameter may be inserted into the hole before drilling the hole in the conduit.

EXAMPLE 1

The Condufill™ process

Condufill™ is a rigid polyisocyanurate cellular plastic foam. It is high density, closed cell, water impermeable insulation material that is used in the Condufill™ for insulating steam lines by filling the annular space in the conduit containing the lines.

Preferable "Condufill™" is installed using a Mobile Pumping Unit (MPU). U.S. Patent Application US 2005/0258269, entitled "Mobile Pumping Unit for Dispensing Insulating Material In Situ," assigned to the same assignee as the instant invention and hereby incorporated herein by reference in its entirety, teaches just such an MPU.

The procedures for a typical Condufill™ injection day are as follows:

1. Verify the fuel levels for the MPU and generator.

2. Fill tanks as necessary.

3. Drive the MPU and support vehicles to the injection site.

4. Park the MPU at a secure injection site location, use the tire chocks when necessary. 5. Place the copper ground protection pole into the ground.

6. Start the diesel generator, wait at least 30 seconds until power supply is correct.

7. Perform pump maintenance.

8. Verify the chemical levels in each tank.

9. Start the air compressor.

10. Start the chemical temperature control units and the air driers.

11. Start the Rim Cell series model #RC-30-GE and turn on computer control panel.

12. Calibrate the pressures and flow rates of components.

13. Select the injection operating mode: Manual or automatic pour time control, and begin injections.

14. Remove excess foam and apply waterproofing tar to exposed foam areas.

15. Stop the controls on the MPU and turn switches off.

16. Return to storage facility or move to another injection site.

EXAMPLE 2

Steps for Injection 1. Technical evaluation of the system a. Identify and evaluate various street locations for installation and prioritize the same. b. Review the excavation and existing manhole access points in to the conduit air space based on drawings and existing site

conditions. c. Obtain necessary permits. d. Schedule contractors for support activities to install Condufill.

e. Calculate material requirements for the install process.

2. Accessing the conduits. a. As the excavations are opened for installation of Condufill, the crews need to physically study the void area for

congestion, steam line/condensate line sizes, existing insulation condition and actual void interior sizes. b. Determine the distance that tubing can be effectively inserted into the conduit void. This may be accomplished by inserting a fiberglass rod into a section of Teflon tubing. Once the specific length of Teflon has been installed onto the reel, the crew can then push the Teflon and fiberglass rod into the void of both the large and small conduits.

3. Tube insertion a. Once the tubing length has been determined cut hose lengths to the lengths determined. b. As per the installation protocols, for temperatures, flow rates and pressures pre-set with the MPU, total hose lengths of 80 feet need to be used. c. The total hose length can be made up from a combination of both the specified Teflon and rubber hose sections. d. When using Teflon in smaller voids, the part outside the void itself can still be rubber hose.

4. While injecting a. Control the injection (using eye sight and halogen lamps) and withdraw the Teflon tubing as necessary. The person performing the injection should be able to witness the progression of a foam wave towards them and visually confirm it is being applied to all areas within the conduit void. b. When injecting in to a void that cannot be witnessed visually, the timing of the injection, based on previous void calculations and product requirements, is a critical step to maintain. This method requires the operator to mathematically calculate how many cm/inch of Teflon tubing should be pulled per minute based on the void size, compaction, and flow rates. c. Generally this method will need to be utilized in conduits that are smaller in size and/or positioned that prevent the injection operator from allowing his head/body the ability to physically see into the void. d. Coordinate withdrawing hose with another person in charge of timing the operation and the PLC operator in charge of checking volumes dispensed as the injection is in progress. It is important to withdraw the hose as late as possible, leaving no chance for any voids to occur. In smaller void, the movement of the hose tends to be limited, and as the foam expands, it can and will at times trap the hose before the operator can effectively withdraw it or before the shot is complete. e. The shot can continue to be pumped, provided that the flow through the hose proceeds in an uninhibited manner and without any added pressure. The operator must maintain his timing of the shot to ensure the proper amount of product is being injected.

The compacting of foam may lead to trapped hoses but it will not affect the quality of the foam. It will however, increase the cost of the injection should you continue to pump the product beyond that of the calculated amounts. Proceed with inserting a new section of Teflon tubing into the void if the first hose gets trapped and repeat Step 4. Ensure that the new Teflon is placed against the wall/wave of dry foam generated by the last injection. Withdraw the hose 2-3 feet, and then begin the next injection. Withdraw the hose slowly and rely on the sticky/trap feeling of the hose once again.

EXAMPLE 3

ConduFill Technical Data

(an HT-450 formulation)

Density: 3.0 pcf

Service Temperature: 400°F / 204⁰C

Closed-cell Content: >95%

Compressive Strength: 16-30 psi

K Factor 0.18 Btu-inch/hr-ft2-degree F

Dimensional Stability -0.20% (by volume)

Water Absorption <2% (by volume)

While the invention has been described with reference to certain exemplary embodiments thereof, those skilled in the art may make various modifications to the described embodiments of the invention without departing from the scope of the invention. The terms and descriptions used herein are set forth by way of illustration only and not meant as limitations. In particular, although the present invention has been described by way of examples, a variety of devices would practice the inventive concepts described herein. Although the invention has been described and disclosed in various terms and certain embodiments, the scope of the invention is not intended to be, nor should it be deemed to be, limited thereby and such other modifications or embodiments as may be suggested by the teachings herein are particularly reserved, especially as they fall within the breadth and scope of the claims here appended. Those skilled in the art will recognize that these and other variations are possible within the scope of the invention as defined in the following claims and their equivalents.

Claims

We claim:

1. A method for the insulation of an underground steam pipe within a conduit comprising the steps of: forming a hole in the ground substantially aligned above the steam pipe within the conduit; drilling an aperture in the conduit without affecting the steam pipe;

inserting tubing through the length of the formed hole so that a first end of the tubing passes through the drilled aperture and is positioned next to the steam pipe; attaching a second end of the tubing to a pumping system; pumping plastic foam through the tubing around the steam pipe using the pumping system; withdrawing the tubing from the aperture and from the hole in the ground; and causing the foam to cure and become rigid thereby functioning as thermal insulation for the steam pipe.

2. The method of claim 1, wherein the foam has a density of 3.0 pcf.

3. The method of claim 2, wherein the foam has a service temperature: 400°F / 204⁰C.

4. The method of claim 3, further comprising forming a plurality of spaced- apart holes in the ground, each substantially aligned above the steam pipe.

5. The method of claim 4, further comprising drilling a plurality of spaced- apart apertures in the conduit without affecting the steam pipe using the plurality of spaced-apart holes in the ground.

6. The method of claim 1 further comprising pumping the plastic foam, through the tubing, a distance of not more than 100 feet.

7. The method of claim 6, further comprising the steps of inserting a plastic liner into the hole and lowering a drill through the plastic liner prior to inserting the tubing.

8. The method of claim 1 further comprising selecting the plastic foam from the group of polyurethane, polyisocyanurate, and urethane-modified polyisocyanurate .

9. A reinsulated underground steam pipe within a conduit, with an annular area formed between the pipe and the conduit, having a rigid plastic foam structure disposed in the annular area, wherein the rigid plastic foam structure is comprised of preexisting rigid insulation that is substantially incorporated within a newly cast plastic foam and wherein the plastic foam has a density of 3.0 pcf, a service temperature: 400⁰F / 204⁰C, and a compressive strength of 16- 30 psi.

10. The method of claim 1 wherein the plastic foam is a phenolic foam.

11. A method of insulating an underground steam pipe within a conduit, with an annular area formed between the pipe and the conduit, the method comprising:

providing an uncured plastic foam into the annular area; and

allowing the plastic foam to cure.

12. The method of claim 11, wherein the plastic foam is selected from polyurethane, polyisocyanurate, polystyrene, polyvinyl chloride (PVC) and phenolic foam.

13. The method of claim 11, wherein the plastic foam is a phenolic foam.

14. The method of claims 11, wherein the uncured plastic foam comprises a plurality of components.

15. The method of claim 14, wherein the plurality of components are mixed together before entering the annular area.

16. The method of claim 14, wherein the plurality of components are mixed together within the annular area.

17. A method of forming an underground insulated steam pipe system, the method comprising:

providing a steam pipe within a conduit such that an annular space exists between the steam pipe and the conduit;

providing an uncured phenolic foam to the annular space; and

allowing the uncured phenolic foam to cure forming a rigid insulation substantially filling the annular space.

18. The method of claim 17, wherein the uncured phenolic foam comprises a plurality of components. US2006/045809

19. The method of claim 17, wherein the plurality of components are mixed together before entering the annular space.

20. The method of claim 17, wherein the plurality of components are mixed together within the annular space.

21. An insulated underground steam pipe system comprising:

a steam pipe;

a conduit surrounding the steam pipe such that an annular area is formed between the pipe and the conduit; and

an in situ cured plastic foam structure substantially filling the annular area.

22. The insulated underground steam pipe of claim 21, wherein the rigid plastic foam is a phenolic foam.