There are two main types of hydraulic torque wrench, the Square Drive
wrench and the Limited Clearance wrench (also known variously as Low Clearance/
Direct Fit/ Cassette/ Hex Link wrench). The Square Drive wrench drives a socket
whereas the Limited Clearance wrench fits directly on the nut. The vast
majority of hydraulic torque wrench tool systems are "double-acting"
(hydraulic advance, hydraulic return back over the ratchet) although
single-acting (hydraulic advance, spring return back over the ratchet) systems
are available and whilst few manufacturers/suppliers cater for this option, the
single-acting system can bring advantage in terms of cost and on remote,
difficult-to-access bolting applications where a power source is not readily
available.
The Square Drive wrench is by far the more versatile of the two wrench
options in that it will drive any AF size socket with a suitable drive. The
Limited Clearance wrench requires a bespoke AF size hex link for each size nut
which can make it expensive to assemble a suitable range of equipment for all
bolt sizes. With good operating habits, both wrench types are easy and safe to
use although the Limited Clearance wrenches are generally more suited to flange
work than their Square Drive counterparts.
Given a choice on any bolting job where either wrench type can
legitimately be used, I would personally opt for the Limited Clearance wrench
as it negates much of the twisting force and reaction challenges often
experienced by the Square Drive wrench. Having said that, the Square Drive
wrenches find more favour with our customers which is indicative of their much
greater versatility and resultant cost effectiveness.
The wrenches are powered by a hydraulic pump. Most Torque Wrenches systems nowadays are designed to work to a maximum pressure of 10,000
psi (710 bar). The pump pressure, as measured by the pump pressure gauge and
locked in at the desired rating, dictates the torque output of the wrench.
Typically, the pumps are either air or electric powered (usually 110V) although
the single-acting wrenches can be powered by any 10,000 psi pump including
manual hand pumps. The wrenches are
connected to the pump by a high pressure siamese hose (or single hose for
single-acting wrenches) usually around 5m in length although can be any length
within reason.
The most commonly used wrenches tend to be 3/4" and 1" Square
Drive Wrenches with maximum torque outputs ranging from 1000Nm up to 4,000 Nm
and their Limited Clearance counterparts - accommodating nut AF sizes up to
80mm - up to around 5,000 Nm. Beyond these, the Square Drive wrenches ( 1
1/2" and 2 1/2" drives) and Limited Clearance wrenches in most tool
ranges accommodate tightening torques up to and in excess of 30,000 Nm for
working on large bolts.
Gulf Incon, an authorized dealer of SPX Bolting system in UAE
offers hydraulic torque
and tensioning systems, industry specific certified training programs, system
rentals, and flange management database software etc. If you need more about torque wrenches or bolt tensioners feel free to contact us and our experts will
guide you.
