Tools Manual

How to determine a high quality hydraulic torque wrench
 
Hydraulic torque wrench come out because of the bolt tightening and loosening. It plays a very important role in the world mining, metallurgical, power generation, wind power energy, ship building, oil and gas, steel, offshore any industry regarding to the bolt solution.
People used to tight the nut by hands. However, when the tighten torque request higher and bolt space has limitation, people can not finish the job by hands. So they find out the hydraulic torque wrench to help them tighten the bolt.
Nowadays, the hydraulic torque wrench is not just help people tighten the nut but also need to help tighten the nut in a accurate torque. Tighten torque bigger than the nut torque request, the nut may get broken. Tighten torque smaller than the nut torque request, there will be a risk in the future. For example, the nut help connect two split flange. If the nut do not reach the tighten requirements, the flange may result in leaking in the future. It may result in a very serious accident.
Therefore, chose a high quality hydraulic torque wrench is very import.
 
How can we chose a good supplier with this equipment?
1. Material of the hydraulic torque wrench
Square drive torque wrench body material and Low profile wrench power head material:
The first hydraulic torque wrench main body material is using Steel. Steel is one of a durable material. However, the steel material is too heavy. It is not convenient for people when they operating the torque wrench and move the torque wrench. As a result, people find out another material Aluminum-Titanium alloy which is aerospace material. This material is also durable but its light. The impact strength and yield strength of this material is qualified in this equipment.
The significant advantage of Aluminum-Titanium alloy is the weight reduced a lot compare to the steel.
Even the Aluminum-Titanium also have different kinds of grade which will effect on the hydraulic torque wrench quality.
So, check the raw material is very important. Every brands of torque wrench can broken. However, if the torque wrench body broken one by one, you really need to doubt their material selection.
Aluminum-titanium alloy have a lot of suppliers in the world. Check with the supplier where they purchase from and which brand (country of original) . The famous brand should have a fully strict rules to examine their material before they send out to its customers.
Interior spare parts of hydraulic torque wrench, square drive material:
For example: I take hydraulic torque wrench square drive series as an example
Square drive wrench accessories of square drive.
It happens very often, the torque wrench performance well but the square drive keep broken. The customer may feel confuse.
Actually, it also regarding to material selection: The raw material of square drive can be 34CrMo or 38CrMo. The difference will direct effect on the strength of square drive. The cost of the material is also different. Usually, the manufacturer do not like to communicate with material selection as they think that is their own secret. That is why the spare parts quality different. To judge the square drive good or bad quality is depend on the material yield strength. Be simple, that is how much strength or how hard the parts are. Some good suppliers, their square drive yield strength can reach 1200 degrees while some poor suppliers can only reach up to 800 degrees.
 All above is why every player said they are using Aluminum-Titanium but the torque wrench performance different in the world.
 
Therefore, a professional good manufacturer should have a clear understand of how to selecting the raw material of hydraulic torque wrench. This technology will bring them a good reputation of high quality products.
2. Machining Accurate effect on hydraulic torque wrench
Only know how to select the material is not enough, the hydraulic torque wrench manufacturer still needs good at machinery manufacturing.
First the factory should have good machining equipment.
For example: modern CNC Machine instead of traditional manual work shop.
With good and high-accuracy CNC Machine can help reduce people mistake during the manufacturing process. The purchase depart should have good talent in charge of CNC machine.
Usually, a square drive hydraulic torque wrench including more than 50 spare parts. Most of the parts will be done in the CNC Machine. The hydraulic torque wrench torque output accurate depend on the spare parts accurate or not. The size of the spare parts even dozens of dmm will effect on the hydraulic torque wrench.

 
3. Machinery Manufacturing Process of hydraulic torque wrench
With good material and good machines are not enough. The manufacturer should be very familiar with the manufacturing process.
For example, the hydraulic torque wrench low profile wrench side plate belonging to low profile wrench hex link.
The raw material should machining before the heat treatment or after the heat treatment. This will be very different towards the side plate strength after finished. The raw material of side plate receive a heat treatment before machining will help the raw material increase the raw material strength. However, after heat treatment the material will become more strength than the original which will make the cost increase. This is because, the stronger material will be a test for the machine knife during the machining process. Should we ignore the heat treatment before machining? The answer is No. It is not worth to cut the cost base on reduce the product quality.
 
4. Seal ring of hydraulic torque wrench
As we all know the hydraulic torque wrench max working pressure normally is up to 70Mpa some even 80Mpa. Thus, the seal ring inside of the wrench must have really good quality.
Usually, the hydraulic torque wrench manufacturer do not manufacture seal ring. So they purchase from the market. However, the seal ring quality is very different. Some very very cheap some are more expensive. As a good manufacturer, they should not save the cost at the seal ring. The seal ring plays a very important role in the hydraulic torque wrench. It helps avoid leaking. Once the wrench leaking, the torque output will not accurate and stable. Even worse is the wrench can not work. Whatever, if the torque is not accurate, the torque wrench is no value.
Normally, the square drive wrench at least 13 pieces of seal ring.
Swivel joint seal ring. The swivel joint quality is not only about the machining quality but also related to seal ring.
Piston seal ring etc. See the picture below:

The manufacture should chose the stable high quality supplier. They can not save cost at this point. It is easier for a manufacture to change one of the seal ring in the torque wrench but it is very difficult for the customer change. When the torque wrench broken and delay the end user project, it will result in end user lose more money than a seal ring.
Some Italy suppliers does have high quality seal ring.
5. Assemble the spare parts of hydraulic torque wrench
Check out their assemble process to see if they have very strict controlling system.
Before the spare parts take into the assemble room, the spare parts size should examine through the quality inspector. Any fail spare parts should report to the manager. It is not allow to take out from the work shop.
After finish all the spare parts then they need to be assembled by people.
This people’s technology is also relevant to the hydraulic torque wrench quality.
For example, assemble the swivel joint seal ring. Different manufacturer have different design in the swivel joint so the seal ring assemble is different. Take JHJX as an example, during the assemble process: if the worker make little bit scratch on the seal ring during the assemble, they not to change to a new seal ring. They can not put the flawed seal ring in the hydraulic torque wrench. Otherwise, when this part result in leaking, it will damage the company reputation.
One people assemble, another people stand side is inspector. Both of them need to sign in the data recording system. Every wrench have a serial number which help the factory find out who response for the torque wrench.
6. Testing the hydraulic torque wrench and calibrated before sending out from the factory.
Asking the supplier what is their testing process of a finished hydraulic torque wrench.
For example, how much pressure does the supplier test the hydraulic torque wrench. 30Mpa, 50Mpa, 70Mpa or 80Mpa.
It is necessary to test the hydraulic torque wrench in its max pressure 70Mpa. Some supplier test even bigger than that which is around 80Mpa.
The 70Mpa is under its safe working condition.
How long to keep the hydraulic torque wrench when its working at 70Mpa?
The inspector should remain the max pressure for a moment. Hold the pressure, then inspect the wrench every possible leaking areas.
Calibration of hydraulic torque wrench:
You need to get response from the supplier.
How they calibrate its hydraulic torque wrench.
The torque output accurate whether within +-3% or not. If the torque output more than 3% or less than 3%, this means the torque wrench fail.
What is the transducer using for the calibration.

7. Warranty of the hydraulic torque wrench
Usually, the manufacturer offer the customer one year warranty.
The one year warranty is the common length of warranty.
The warranty of the hydraulic torque wrench should including: main body and every spare parts.