A choke tube hydraulic torque wrench is closed which helps to remove or install choke tubes by using an expanding element that fits right into the choke tube that is being changed. As it expands, it pushes against the inside of the choke tube to keep it from sliding. Outward serrated edges on the the wrench push notches into the tube, helping to turn it. These were filed for patent towards the end of the year 1989. It became a publication a year later, in October of 1990. The creation was credited to two New York men. These men are Stavros Mavrakis and Thomas R. Cresci.
Ratchet tube hydraulic torque wrench are made of stainless steel and carbon and can be used for hydraulics and plumbing. The jaws of this type are made with springs that snap open. They close in onto the tube or fitting. This allows them to be used in small or tight spaces. Most ratchet tube wrenches come in as many as twelve sizes. Some of these sizes are 5/8, 5/16, 1/2, and 3/4.
A tube nut hydraulic torque wrench has a separated push button that revises this electrically operated wrench. It knows when there has been too much pressure set onto the tube, so it loosens its grip. It can sense when the motor is stalled for an extended period of time and shuts off. This type has been around for a little over a decade. It was set for publication in June of 1997, just nine months after the time of filing. The inventors this time were three Pennsylvania men, named John M. Estep, Harry E. Morris III, and Donald R. Warner.