F.A.S.T. (Fully Automated Stud Tensioner) | FASTORQ

F.A.S.T. (Fully Automated Stud Tensioner)

fast1

F.A.S.T. SYSTEM

The F.A.S.T. (Fully Automated Stud Tensioner) system was designed to increase safety, save time, and maximize joint integrity compared to hydraulic torque wrenches and conventional stud tensioners for bolt tightening and loosening operations.

 

HOW IT WORKS

F.A.S.T. utilizes patented ZipNut® Technology to provide tensioning and de-tensioning of fasteners in time critical joints such as drilling risers, subsea piping flanges and pipeline repair clamps. ZipNuts were first developed to NASA’s requirements for a Space Shuttle flight in 1989. Since then, ZipNuts have been used not only aboard the Shuttle, but in construction of the International Space Station and during repair of the Hubble Space Telescope. A ZipNut can be installed by simply pushing it onto a bolt in one motion, eliminating the difficulty of threading a traditional nut. Another advantage of the ZipNut is that damaged threads do not affect its operation, and it cannot be cross-threaded during installation. ZipNuts also come in a Double Zip® option that slides onto the nut in the same manner as the original, but give users the ability to also remove the nut the same way with a release mechanism to slide off the bolt. When this device is used in place of a standard reaction nut for a stud tensioner, it provides the tensioner with the same ability to slide on and off the bolt.

 

SAFETY

The ability to slide on and off the bolts allows F.A.S.T. to operate hands-free with an operator at a remote Hydraulic Control Console with a built in pump to control all functions for the F.A.S.T. This maximizes safety as no personnel need be anywhere near tool when it is operating. The hydraulic pressure from the Hydraulic Control Console to the F.A.S.T. is 2,000 psi. or less making it much safer than the 22,000 psi. required for conventional stud tensioning systems. An intensifier is located inside the tool envelope to deliver the required pressure to the tensioner load cells. Safety is further ensured in the event of hydraulic seal failure by diverting the fluid inside the tool envelope.

 

TIME SAVINGS

F.A.S.T. saves time over other methods for tightening and loosening fasteners in bolted joints.

Hydraulic Ratcheting Wrenches

Hydraulic ratcheting torque wrenches have been used for installation and removal of bolts because of the low cost. However, this is the slowest method for applying bolt load. The torque wrench must be fit on the nut multiple times in a crisscross pattern at progressively higher torque to achieve the final bolt load. This type of tightening method is wrought with problems. First, it is very time consuming as the hydraulic wrench only provides 10 degrees of nut rotation per stroke of the cylinder. Second, torque does not equal bolt load. The nut factor or K-factor is an experimental constant that is an expression of why torque does not directly translate into bolt load. When applying torque, it is only a guess at the resulting bolt load without a way to measure it directly. Third, elastic interactions are the transfer of bolt load from one fastener to another during the tightening process with torque. It is difficult if not impossible to control the final distribution of bolt load from applied torque in a bolted joint. The most important problem associated with using a hydraulic torque wrench is that the operator is required to be hands-on the tool the entire time.

Conventional Stud Tensioners

Conventional hydraulic stud tensioners have been favored over hydraulic torque wrenches for their ability to stretch the fastener thus applying direct load. This eliminates the problems associated with the nut factor or K-factor. However, it is more expensive than using a hydraulic torque wrench because multiple units are required evenly distributed around the joint. The idea is that more uniform direct loading is achieved. The problem is that the required size of the hydraulic load cell does not permit better than 50% coverage of the bolts. Therefore, the stud tensioners must be applied in two passes most of the time. The first set must be installed at a higher pressure than the second to account for a Load Loss Factor which is difficult to predict. The result is often uneven distribution of bolt load. The bigger problem is the time that it takes to install and remove the tensioners. The reaction nut must be threaded onto the stud bolt and secured on top of the tensioner. Worse still, the entire tensioner must be threaded onto the stud if the tensioner is of the direct fit variety. They can be very heavy and quite a bit of dangerous work. After the load cell is extended and the nut turned down to capture the load, the reaction nut is then turned down (sometimes with great effort) to compress the hydraulic load cell. There are spring return options available that help reduce the effort. However, it is still a very time consuming process. Most manufacturers have a split nut reaction unit that saves the time of threading the reaction nut onto the stud. These devices can be problematic in that they are not part of the tensioner and require a human to install. There is also the possibility of cross threading the device and getting it jammed on the stud. Conventional stud tensioners are also available in an MST (Multiple Stud Tensioner) configuration. This allows for the installation of multiple load cells in the same frame but does not do much for time savings. There is also one very big problem associated with conventional stud tensioners. The operator is required to turn down the service nut and the reaction nut on the tension while dangerously close to a 22,000 psi. energized hydraulic load cell!

F.A.S.T. Advantage

Because F.A.S.T. is a tensioning system, it has none of the problems associated with hydraulic ratcheting torque wrenches. Utilizing ZipNut Technology and double-acting hydraulic load cells, it also eliminates the drawbacks of conventional tensioners. 100% coverage means loading all the bolts in a connection simultaneously and thus eliminating elastic interactions and the Load Loss Factor. By reducing the hydraulic load cell diameter and increasing the pressure, the tensioners fit better side-by-side to achieve 100% coverage on the same side of the flange. The overwhelming advantage of the F.A.S.T. is that no human intervention is required at the tool. Everything is controlled from the Hydraulic Control Console.

Comparison

To summarize the differences in time, safety and joint integrity related to torque compared to tension and then to F.A.S.T., the following example is provided. In a piping flange with (24) 2” diameter stud bolts with a target bolt load of 215,000 lb., these are the results for each method:

 

Method

Time

Safety

Joint Integrity

Hydraulic Torque Wrench

2+ Hours

Minimum

Low

Conventional Stud Tensioners

45 Minutes

Minimum

Medium

FAST System

4 Minutes

Maximum

High

 

 

OPERATION

F.A.S.T. must be used with a delivery system such as an articulating arm, rail driven frame or overhead lift system. The delivery system must be able to move up and down, in and out, and side to side. The Hydraulic Control Console is responsible for the following tool actions.

 

Control

Function

Pressure psi. (bar)

Wings

Open & Close

1,500 (103)

Tool Rotation

Clockwise & Counter Clockwise

1,500 (103)

Nut Rotation

Clockwise & Counter Clockwise

1,500 (103)

Load Cell

Extend & Retract

2,000 (138)*

ZipNut

Release

1,500 (103)

*2,000 psi. (138 bar) is intensified to 25,000 psi. (1,517 bar) inside the tool.

 

 

Click the picture below to see how the F.A.S.T. works.

fast_offshore