The vibratory plow is inserted into the ground and as the machine moves forward the vibration or oscillation of the blade cuts or separates the ground. Behind the oscillating or vibrating blade, the tube is connected and pulled through the slice in the ground. Photo Credit: Reed Manufacturing Company.
Figure 1. Figure 3. Key Considerations for Impact Moling While using a moling process for underground copper water services, the following installation conditions should be evaluated on a case-by-case basis to ensure no unforeseen tube damage is encountered. Be cognizant of areas that may present different soil conditions in the path of the installation. Where questionable soil conditions are suspected, testing should be conducted to evaluate the soil corrosivity.
Care should be taken to ensure that sharp rocks, underground structures or other obstacles are not present in the path of installation. Sharp underground objects can gouge, scrape or ultimately damage the copper tube, or poly wrap material, as the tube is pulled through the bore hole. Photo Credit: Charles Machine Works. Key Considerations for Open Trench Installations When open trenching is utilized for the installation of underground copper tube, a number of factors must be taken into account to ensure it is safe and long lasting.
Copper tubing should be installed so that it is surrounded by a homogenous backfill on all sides of the tube, including between the trench floor and the bottom of the tube. Laying the tube on the bottom of a trench, where it is in contact with the undisturbed or virgin soil could create an oxygen differential cell along the bottom of the tube and in rare cases can lead to preferential corrosion in this area. Slide the nut over the ring and thread it onto the fitting until it is hand-tight.
Be careful not to cross-thread the nut. Solenoid valves are used to help control the flow of different liquids and gases. It can never be reused once they have been compressed. This connector is directly placed over the pipe and the nut is tightened compressing the ferrule between the pipe and the body of the fitting.
Compression of this ferrule also results in deformation of the copper tubing. NPT ends look very different than compression ends.
NPT has no nuts or ferrules, but instead relies entirely on a thread connection. A 2-way, normally closed, solenoid valve has 2 pipe connections, an inlet called the cavity port and an outlet called the body orifice port. When the valve is energized the plunger opens allowing media to flow through the valve in the cavity port and out the body orifice port. Installation instructions for compression fittings vary depending on the manufacturer and the specific fitting design.
Care should be taken to follow the assembly procedures recommended by the manufacturer. There are however, several common elements to the installation procedure for nearly all compression fittings:. Typically the procedure for tightening a compression fitting is specified using the rotation of the nut as the key metric, rather than torque.
Torque, on the other hand, can vary greatly, depending on fitting and ferrule material, lubrication, degree of galling for stainless fittings , and other factors.
This does not hold true for compression fittings. Insufficient tightening of the compression nut will not deform the ferrule enough to create this contact, but over-tightening will deform the ferrule too much, creating a surface contact. A surface contact weakens the seal and often results in leaks. Disassembly and Re-Assembly The ease of assembly and disassembly is one of the reasons why compression fittings are so widely used.
Disassembly involves simply loosening the compression nut or screw. Re-assembly can be accomplished in a similar manner to the initial assembly, although typically fewer turns of the nut are required, since the ferrule is already swaged to the tubing. Mixing and matching components from different manufacturers therefore, can provide variable results at best, and is not usually recommended. Compression fittings are often selected for reasons beyond just leak-free sealing and ease of use.
In many applications, high pressures and temperatures necessitate the use of hard tubing, which is incompatible with many other types of fittings.
In other applications, such as laboratory instruments, concerns over contamination make the sterility and low out-gassing properties of stainless steel tubing and compression fittings attractive. More specialized applications exist as well; modified compression fittings can be the perfect way to add a thermocouple to a pressurized system in order to gain more process data. High Pressure Applications Compression fittings are the perfect choice for high pressure applications. In combination with a high pressure tubing material like steel, large compression fittings can often be used at pressures in excess of 10, psig.
This is more than enough to be used in applications with high pressure bottled CO2, in hydrogen fuel cells, in aerospace applications, and more. The key to using compression fittings at high pressure, especially with gases, is the integrity of the ferrule seal. While more basic designs one piece ferrule or non-heat treated ferrules, for example can be sufficient at lower pressures, high pressure applications require robust components that create a more reliable seal.
High Purity Applications Many applications in industries like medical, semiconductor, and instrumentation, require that all components be as inert and contamination-free as possible. Compression fittings facilitate these applications greatly. Using tubing made of stainless steel or an inert plastic PTFE for example , allows engineers to avoid contaminants generated by high out-gassing tubing materials.
Brass compression fittings will work on some sizes of clear vinyl tubing and most sizes of low density polyethylene tubing. However, it really depends on the outside diameter and the inside diameter of the plastic tubing. When using plastic tubing, the "plastic sleeve" must be used and the "brass insert" must be used.
The plastic sleeve is used to seal against the outside of the plastic tubing and the tapered end will seal into the compression fitting. Plastic sleeves are used because the brass compression sleeves can more easily cut into the plastic tubing, potentially causing a leak.
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