T-BAR CABLE CLAMP
Publication Date: 2008-Sep-23
The IP.com Prior Art Database
A wireline T-bar clamp is provided that includes a T-section; and a clamping section below the T-section, wherein the clamping section comprises a liner for receiving a wireline cable, and wherein the liner comprises one or more curved sections.
FIELD OF THE INVENTION
The present invention relates generally to a wireline T-bar clamp, and more particularly to a wireline T-bar clamp having an improved clamping section.
Wireline T-bar clamps are routinely used to secure wireline logging cables during wellbore operations such as LWF (Logging While Fishing) and wireline fishing. Their primary purpose is to clamp wireline cables so that slack can be provided. This slack is required during many wireline fishing operations and is often used to solve a variety of other problems, such as preventing cables from jumping (i.e. becoming disengaged with) wireline sheaves, and removing damaged cable sections.
A standard T-bar design has been in use for many years. Such a standard T-bar is shown in Figure 1, where the “T” is located at the top of the assembly with the block or clamping section located below the “T” (note that Figure 1 shows the T-bar in a horizontal position, however in use the T-bar is in a vertical position, as it is shown in Figure 3.)
Figure 2 shows a more detailed view of the standard T-bar clamping section. As shown, this section includes a cable insert or liner which is typically composed of brass. In this design, the clamping strength is created by tightening turnbuckles around the liner to “clamp” the cable into the liner. However, when the cable is placed under extreme tensions, this type of clamping section has been known to allow the wireline cable to slip relative to the T-bar.
For example, a 30,000 foot deep well could require cable tensions in excess of 12,000 lbs for normal wireline logging runs and 18,000 lbs to pull the cable free if a stuck situation occurs. Using the standard T-bar, these high loads could allow the cable to slip; to become damaged, or even fractured due to the extra force required on the turnbuckles.
Accordingly, a need exists for a wireline T-bar clamp having an improved clamping section.
DETAILED DESCRIPTION OF THE DRAWINGS
In one embodiment the presenting invention is a wireline T-bar clamp having a clamping section adapted for improved strength. For example, in one embodiment an insert or liner in the clamping section includes in at least one curved section to create a “capstan” effect. That is, by adding these curved sections to the liner, a cable clamped therein experiences more liner contact due to the longer path (for the same T-bar length) and also experiences a “capstan” type of effect to keep the cable from slipping. With this design, the more tension applied to the wireline logging cable, the more “capstan” effect it will see, thus eliminating slippage even when the cable is under extreme loads.
When pulling on the wireline cable is required, it is usually performed with rig equipment instead of a wire...