WHAT TO CONSIDER BEFORE CHOOSING A TORQUE WRENCH, TO SUIT YOUR APPLICATION AT THE BEST
Torque wrench is used to apply a controlled torque to bolted joints: mechanical joints (automotive, aeronautics, carpentry, reducers, etc.), flanged joints for transporting fluids (petrochemical, food, nuclear, etc.) smaller coupling (electronics, hydraulics, bicycles, etc.).
Without knowing exactly the applied torque, the coupling of two parts is very much subjective, ineffective and entrusted to the operator’s feeling. The result is affected by operator strength, height and fatigue, and could greatly vary the resulting torque (and thus preload) on the joint.
An example are the fixing screws of the wheels of cars, motorcycles and bicycles, or a flanged joint for pipes carrying flammable fluids: an incorrect Torque can cause a nut loosens (tightening torque lower than the target value) or breaks (tightening torque exceeding the target value) with consequent loss of wheel, in the case of vehicles, or leakage of liquids that can be hazardous to people and to the environment (with catastrophic consequences in some cases).
- A well-made torque wrench must be designed, built and certified according to DIN EN ISO 6789, a standard that guarantees its reliability, quality and safety.
- Latest version available: DIN EN ISO 6789: 2017
Tolerance of torque wrench
Torque wrenches generally have a precision stated by the manufacturers that it is dictated by DIN EN ISO 6789: 2017 which is +/- 4% for manual wrench and +/- 6% for small capacity wrench and screwdrivers. TECNOGI wrenches are within the required parameters and some models are also more precise than required (900 Series, 4000 = 3% and the 7000 Series +/- 1%).
After a certain number of tightening cycles or time elapsed, it is advisable to carry out a new calibration, so that the Torque Wrench falls within the parameters determined at the beginning. The EN ISO 6789: 2017 standard recommends calibration every year or after 5000 tightening cycles. This time frame is decided by the company quality office, who knows the type of applications and the characteristics. TECNOGI offers a service of calibration with Accredia Certified transducers, in addition to repairs and restoration of the nominal scale where it is possible.
Torque calculation
The torque wrench works by applying a force (N or Kg or Lb). Considering the distance between the application point of the force and the tightening point (m or cm or ft), the torque is given in N · m or Kg · m or Ft · Lb.
Formula for calculating the Torque: Force X Length = torque 100 Kg x 1 meter = 100 Kg · m
Torque calculation for special adapters
First of all, it is necessary to know the necessary torque given from designer or specifications. This value is needed for the selection from the capacity that the wrench can provide, and that falls within the parameters you need. It is a good rule to select a wrench so that you have a maximum capacity that is at least 10% higher or lower. Example: If the target torque is 80 N · m, it will be better to choose a capacity range from 40 – 200 N · m .
Torque wrench type
Using a torque wrench we will apply an exact torque value, but an operator’s ability to react will also be needed to prevent over tightening (if the operator movement goes over the degrees of click of the wrench).
A clear example can be found on a wrench with a wide 20 ° click angle: this type of wrench it is used in mass production where controlled torque is essential. The 20 ° cut off allows the operator to avoid over tightening in applications of importance primary (engines, wheels, steering, …).
CLASSIC TORQUE WRENCH – LIMITED DEGREES OF RELEASE
The torque increases at the growing of the applied force.
At the achievement of the set torque – threshold “set torque” – the wrench breaks and for 3° / 6° it doesn’t exercise any torque. If the operator doesn’t stop to apply force during this gap, the torque begins again to grow, overcoming the set torque.
BREAKING TORQUE WRENCH – 20 DEGREES OF RELEASE
The torque increases at the growing of the applied force. At the achievement of the set torque – threshold “set torque” – the wrench breaks and for 20° it doesn’t exercise any torque, gap wider than the previous one, as shown in the graphic. The operator has more margin to stop to apply the force, preventing the overcoming of the set torque.
SLIPPING TORQUE WRENCH
The torque increases at the growing of the applied force. At the achievement of the set torque – threshold “set torque” – the wrench breaks and ceases to exercise torque. Continuing to apply force, the torque increases until the threshold “set torque” breaking again, preventing the overcoming of the set torque. It is not applicable the rearm concept as it is not necessary to re-set the break mechanism.
Comparing click angle from TECNOGI wrenches and competitor wrenches
TECNOGI offers very broad degrees of release on all its models which allow the operator to prevent over tightening.
Torque wrench technology
Click – spring
A spring inside the wrench is compressed and this compression will cause the click will occur at the set torque. This is the most widespread system for torque wrenches on the market, but it needs to be reset at every work shift so that the spring is not left compressed for long time, losing its calibration then. This typology is available both with 3 ° of detachment angle both with 20 ° of shutter angle.
Click – variable geometry
The innovative “variable arm trigger mechanism” (TECNOGI patent) allows you to adjust the tightening torque by varying the mutual position of the internal and non-internal lever systems, by loading a spring as in the case of traditional click wrenches. The internal spring only creates the necessary contrast for the trip and reset, always working in the same condition regardless of the couple exercised: this innovative method guarantees a longer calibration duration and improved repeatability.
Click – electromechanical
They are normal spring-loaded keys but with a digital display that through the internal software allows you to have a light and sound confirmation of the achievement of the set torque. Self by mistake the operator should exceed or not reach the set torque will be signaled with red light and indicated as ‘’ Non Ok ’’.
Slip
Torque wrenches ideal for controlled tightening in production lines. On reaching the torque value set the wrench “slide” freely, this mechanism ensures not exceed the set torque value.
Dial
Dial wrenches indicate the torque detected through a hand (reading needle) while a static indicator confirms the torque reached remaining stationary after the displacement caused from the reading needle. They are also used to evaluate the torque needed to move, example sphere inside a valve, and then calibrate any actuators.
Digital
Electronic wrenches read the values of the Torque and/or Torque / Angle through a transducer. Available with torque reading accuracy of ± 1% and rotation angle reading of ± 1%, to satisfy the most demanding applications.
• Torque: peak and continuous mode reading
• Torque or torque / angle reading
• Clockwise and counterclockwise (CW / CCW)
• Torque reading precision: ± 1% or 2% on the value read (10% -100% full scale)
• Angle measurement accuracy: ± 1% on the value read
• Setting value of torque target or torque cycle + angle
• Setting the percentage deviation value (acceptable range) with respect to the target value
• Data that can be stored: 900 (date, torque value, angle value, measurement set)
• Yellow/green/red LEDs and buzzer
In the most complete models, a cable or WIFI transmission allows to connect to a computer with various functions. It can record values applied with reference to the joint and the operator. In addition, it can provide Torque / Angle charts. As an example: we can consider an operation for a valve, where the sphere inside will need a certain strength to move and overcome the friction of the gaskets. With this function the operator can graphically see the force applied to each rotation angle.
Wrench accessories
Torque multipliers
In its range TECNOGI also includes mechanical torque multipliers. Designed to allow tightening to high torques, even in limited or inaccessible spaces. All the models are equipped with safety protection against overloads: the drive (models TN14, TN27 and TN35) and the plug (models TN40, TN60 and TN95) are calibrated to yield if subjected to 20% of overload, thus protecting the internal mechanisms of the multipliers. Accuracy ± 5%.
Torque cells
The BTR is a digital torsometric cell ideal for the calibration and control of torque wrenches, screwdrivers with direct reading and snap action.
Joint simulators
The joint simulator reproduces the working conditions of a tightening tool. In combination with a torque transducer, it allows the calibration of a screwdriver considering the rigidity of the joint on which it will operate.
Software
TDEMO – Simple PC-BTR connection program through an RS232 serial port. Allows reading the data collected and sent by the BTR to the acquisition PC.
Torque KAL – The program guides the user in the calibration process of torque tools via sample devices (eg certified BTRs).
Services
Calibration certificats
We issue calibration certificates with international traceability through accredited laboratories on all types of torque wrenches of all brands; at the request of the customer it is possible to supply them with ACCREDIA certificate issued by an ACCREDIA accredited calibration center by “dall’Istituto Metrologico Primario”.
Post-sales assistance
Short time repairs
Torque multipliers control reports
Per altre informazioni visitate il nostro sito www.tecnogisrl.it
TECNOGI fa parte di SCS Concept Group – www.scsconcept.com
