DTIs, are single use mechanical load cells used
to indicate when the required tightening torque has been achieved in
structural fastener assemblies.
Direct tension indicators are hardened washer shaped components with 4 to 6 small arch-like protrusions on the bearing surface that are designed to deform in a controlled manner when subjected to appreciable tightening torque.
Basically the Direct tension indicators washers work on
the principle that appreciable tightening force on the bolt nut assembly the
arch like protrusions collapse under the applied load and this indicates that
the required torque has been applied in tightening the assembly. The gaps in
between the washer and nut are normally checked with thin feeler gauges. In
some cases the protrusions are filled with certain silicone material which
flows out from the protrusions and through the crevice in the washer towards
the outer edge thus indicating that appreciable torque has been applied in
tightening the assembly. These washers are known as Squirter
Washers because the silicone is squirted out from the protusions as the
washer flattens out with increasing load.
High quality alloy steel/C-65 spring steel material used
in the manufacture of direct tension indicators washers shall be designed,
processed, heat treated, and protectively coated as required. These direct
tension indicators washers are manufactured to conform to required
international standards for chemical composition, load, and dimensions.
DTIs are a function of induced tension. As the fastener
assembly is tightened, the arch-like protrusions are compressed and the change
in distance between the base of the protrusions of the DTI washer and the
protrusion apex correlates to a value of tensile force induced into the
fastener. This distance can be verified by insertion of a tapered feeler gage
between the protrusions to the bolt shank. The number of instances the bolt
shank can be reached by the feeler gage is then compared to either the results
of a pre-installation verification procedure or the manufacturer's
instructions.
DTI washers indicate the amount of torque applied to
tighten the assembly is a
function of induced tension. As a fastener assembly is tightened, the arch-like
protrusions are compressed
and the change in distance between the base of the protrusions of the DTI washer and the protrusion
apex, indicate the amount of tensile force induced into the fastener assembly.
Common uses of DTI washers are in machinery and heavy
structures like road and rail bridges and also building structures. Inspection
entails that structural engineers randomly check the fastening units with
tapered feeler gauges. Though the washers are made to international standards
the same can be cross checked by using torque indicating wrenches which give a
reading of the applied torque. Nowadays it is mandatory for design engineers to
specify the use of DTI washers because of this inherent characteristic.
DTI Washer can sit on the structural member or be
separated by a washer, but it should never be installed with the bumps facing
the member and it should never be touching a rotating surface.
Bhalla Fasteners manufacture these DTI washers according to the ASTM F959 & EN-14399-9 standards. DTI Washersby defination stands for ‘Direct Tension Indicator Washers’ and is mostly used to measure the bolt tension developed during the tightening process regardless of the torque resistance of the bolt. At Bhalla Fasteners we usually manufacture these washers in C-45, 8.8 and 10.9 grades in sizes M12 to M36 Bhalla Fasteners is among the largest manufacturers of DTI washers in India and exporter to Europe and is known for the high-quality, reliable products that we produce.
DTI Washer is the world’s simplest cost effective
solution to control the tensioning of bolts. These unique, patented fasteners
deliver consistent, reliable bolt tension, along with installation and
inspection efficiency. They are used every day to achieve required tension
loads on bolts in countless applications including: structural steel buildings
and bridges, studs used in the petro-chemical industry, anchor bolts and SAE
cap screws for automotive applications. This washer is also known as ASTM F959
Washer.
Bhalla Fasteners is the leading manufacturer, supplier,
exporter, trader of DTI washer in Kolkata, Coimbatore,
Salem, Chennai, Hosur, Hyderabad, Andhra Pradesh,Gujrat, Karnataka, Kerala, Perambur, Ennore, Ambattur,
Pune, Mumbai, Nasik, Aurangabad, Nagpur, Chandrapur, Ichalkaranji, Jalgoan,
Kohlapur, Sriperumpudur, Meerut, Durgapur, Kharagpur, Kalyani.
Bhalla Fasteners is the leading manufacturer, supplier and exporter of DTI washers in USA ,UK ,Poland, Germany ,France, Spain, Belgium, Greece, Denmark, Estonia, Hungary, Austria, Portugal, Finland, Czech Republic, Sweden, Latvia, Lithuania, Slovakia, Croatia, Bulgaria, Austrailia, Scotland, Panama, Ireland, Netherlands, Italy, Canada, Mexico, Brazil, Argentina, Colombia, Cuba, Peru, Chile, Costa Rica, Paraguay, Uruguay
Bhalla Fasteners is the leading manufacturer, supplier, exporter, trader of DTI washers in Kolkata, Coimbatore, Salem, Chennai, Hosur, Hyderabad, Andhra Pradesh,Gujrat, Karnataka, Kerala, Perambur, Ennore, Ambattur, Pune, Mumbai, Nasik, Aurangabad, Nagpur, Chandrapur, Ichalkaranji, Jalgoan, Kohlapur, Sriperumpudur, Meerut, Durgapur, Kharagpur, Kalyani.
Load indicating washers (LIW) are used to develop the correct tension when installing A325 or A490 structural bolts used in construction. Standard DTIs and loading indicating washers are made to ASTM F959. Load indicating washers may be available for other bolt grades and made on order.
I Size/Grade | OD Min. [mm] | OD Max. [mm] | ID Min. [mm] | ID Max. [mm] | Thickness Min. [mm] | Thickness Max. [mm] | Number of Protrusions | Weight [kg/pc] |
---|---|---|---|---|---|---|---|---|
M12 | 25.7 | 30.2 | 13.3 | 13.4 | 2.6 | 4.6 | 4 | 0.017 |
M16 | 32.4 | 36.8 | 16.75 | 16.85 | 3.2 | 5.5 | 4 | 0.023 |
M20 | 40.4 | 46 | 20.95 | 21.05 | 3.6 | 6.0 | 5 | 0.029 |
M22 | 42.4 | 50.6 | 23.05 | 23.15 | 3.6 | 6.0 | 5 | 0.045 |
M24 | 48.4 | 55.2 | 25.15 | 25.25 | 4.0 | 7.0 | 6 | 0.048 |
M27 | 54.1 | 62.1 | 28.3 | 28.4 | 4.0 | 7.0 | 6 | 0.089 |
M30 | 58.1 | 69.0 | 31.45 | 31.55 | 4.0 | 7.0 | 7 | 0.097 |
M36 | 70.1 | 82.8 | 37.75 | 37.85 | 4.8 | 7.0 | 8 | 0.116 |