DWTT Drop Weight Tear Tester

Test Application

Metal Testing

Test Property

Standards

What is the Drop-Weight Tear Test?

Steel pipelines are widely used to transport energy in the form of liquid petroleum and natural gas. The steel used in the manufacture of these pipelines must have high strength and toughness, and high resistance to fracture. Over the last few decades, it has been recognized that the Drop-Weight Tear Test (DWTT) better represents the ductile fracture resistance than the Charpy Test, as it utilizes a specimen that has the full thickness of the pipe and has a fracture path long enough to reach steady-state fracture resistance. The zones of ductile and brittle fracture during DWTT characterize the quality of pipeline steels.

The Drop Weight Tear Test (DWTT), specified in API RP 5LR or ASTM E436, was developed in the early 1960s at the Battelle Memorial Institute, USA, to overcome some limitations of the 'Pellini' Drop- Weight Test. Drop Weight Tear Testing is a material characterization test aimed at avoiding brittle fracture and ensuring crack arrest in pipelines (seamless or welded).

Applications

Qualitest Quali-DWTT series is mainly used for drop weight tear test (DWTT) of Ferrite Steels, to observe specimen fracture surface after impact within the temperature that fracture type is converted from non-ductility to ductility. This test method is that the hammer striker with weights is raised to a specific height then released. Free drop hammer impacts and tears the specimen. After the impact, proportions of ductile fracture (shear) and cleavage on the fracture surfaces are measured.

This testing machine complies with the relevant requirements of standards for DWTT such as metallic materials Drop-weight tear tests of ferrite steels.

API RP 5L3 (recommended)
ASTM E 436
EN 10274
GB 8363

The recommended practice API RP 5L3 issued by the American Petroleum Institute (API) describes the testing procedure to be used on large-drop impact testers. A specimen supported at both ends is impacted with a cold-press-fitted notch, with the point of impact opposite to the notch. In some cases, high impact energies of up to 100,000 Joule are necessary to break the specimen.

Features/Advantages

Regulating impact energy by adjusting the lifting height and mass of the weights.
Very robust construction stands up to the rigors of high energy testing to provide high reliability with a minimum of downtime.
The buffer is equipped to absorb the residual energy after breaking the specimen to protect the weight and anvil from destroying. Also install the safe outfit, such as safety net, safe pin for maintenance and hanger locking.
Easily interchangeable contact parts simplify maintenance and reduce the cost of ownership.
State-of-the-art testing accommodates impact energies up to 100,000J and specimens up to 50mm thick also available on request.
Automated specimen loading provides compliance with cycle times required by test methods while maintaining operator safety.
Very rigid base and anvils ensure very low flexure under high test loads.
Guided mass system to ensure that the impact geometry is correct throughout the entire test.
Equipped with the specimen-carrying outfit, anti-falling of outfit for the specimen, centering outfit to guarantee quick, accurate and reliable tests.
High quality, easy to use control software ensures consistency and enhances throughput.
Ergonomically designed, no requirement for the operator to work at elevated heights or handle excessive physical loads.
Optional liquid low-temperature chamber
Optional automatic specimen feeding system
Responsive lifetime technical support.

Semi-Automatic System (Without Automatic Specimen Feeding System)

The operator opens the specimen door on the bath, takes the specimen from the cooling bath and places it on the alignment table. The operator closes the specimen door.

The rest of the sequence is automatic. The autoloader picks the specimen up, places it on the anvil, the clamp is applied and the autoloader returns to the default position. The drop weight is then released and the broken pieces of the specimen conveyed to the right side of drop tower.

Disadvantages

The cycle time might exceed 10 seconds*
Low-temperature hazard
Cooling medium hazard to health (Ethanol)
Cooling medium flammable (Ethanol)
Safety hazard-Operator has to stand close to the machine
Removing the specimen from the bath and breaking them as described in many standards, shouldn’t take longer than 10 Seconds (API 5L3, ASTM E436, EN 10274).

Automatic System (With Automatic Specimen Feeding System)

The operator configures the drop height, cooling temperature and soak time on software.

The rest of the sequence is automatic: the specimen feeding system picks the specimen from cooling bath, places it on the anvil, and then returns to the default position. The drop weight is then released and the broken pieces of the specimen conveyed to the right side of drop tower.

Advantages

Cycle time completely within 10 seconds
Safe to operators
The system is designed for a minimum cycle time of 3 minutes. Cycle times under 3 minutes with very low energy absorption might result in overheating of the shock absorbers, and consequently to damage.

Technical Specifications

Maximum energy (J)	Quali-DWTT-30kJ	Quali DWTT-40kJ	Quali -DWTT-50kJ	Quali -DWTT-60kJ	Quali -DWTT-80kJ	Quali DWTT-100kJ

Drop Height (m)
Max. vertical drop height (m)	3	2.6	2.6	3.1	3.2	4.1
Impact velocity (m/s)	5.4<v<7	5.4<v<7	5.42<v<7	5.4<v<7.9	5.4<v<7.9	5.4 <v<8.96
Resolution	1 mm
Accuracy	± 2mm
Drop weight (kg)
Mass of drop weight frame (kg)	630	800	1000	1300	1300	1300
Mass of weight increments (kg)	19.5	30	50	50	50	50
Quantity of weight increments	20	27	20	24	24	24
Total mass of drop weight (kg)	1020	1610	2000	2500	2500	2500
Mass deflection	±0.5%
Max. Raising speed (m/min)	4
Dimensions & Weight
Dia. of guide column (mm)	Ø110	Ø110	Ø110	Ø110	Ø200	Ø200
Dia. of post (mm)	Ø155	Ø155	Ø155	Ø155	Ø200	Ø200
Overall height of tower(m)	6.2	6.2	6.2	7	7	7.4
Gross weight of tower(kg)	12000	14000	14000	15000	18000	20000
Striker
Radius of curvature	25.4 00 ± 0.1 mm
Centerline with respect to center of anvil supports	0mm ±1.0mm
Complies with	API 5L3, ASTM E436, EN 10274
Anvil
Radius of curvature	15.0mm ±0.1mm
Span	254.0mm ±1.0mm
Complies with	API 5L3, ASTM 436, EN 10274
Specimens
Width	76.0mm ±3.0mm
Length	305mm±50.0mm
Thickness	6mm to 50mm
Notch depth	5.1mm±0.51mm. Notch angle 45°±2°
Notch radius	0mm to 0.05mm
Planarity	5mm
Can accommodate specimens prepared according to standards	API 5L3, ASTM 436, EN 10274
Notch type of specimen	Pressed or Chevron

Main Components

Drop Tower

The structure of the drop weight tower is a 4-support-post & 2-guide-column structure, of which two are used for guiding the hammer and another four posts are for supporting purposes. The servo-controlled hoist motor is installed at the side of the bottom plate, which facilitates the maintenance.

The top plate of drop tower is a complete steel plate of 50 mm thick, on which two pulleys and protective enclosure are installed, and the hoist rope is passing through the two pulleys. The bottom plate of the drop tower is made of cast iron which has excellent anti-impact performance.

The guide columns are firmly mounted between the top plate and bottom plate through a flange interface, and the parallelism degree should be controlled within 0.1/1000. Those columns adopt hollow 45# steel tube, and it is hardened and tempered, the outer surface is electroplated.

Four solid posts ensure the high stiffness

Two guide columns to ensure that the drop weight hit right in the center of specimen, chrome-plated surface ensure the longest life as well as lowest friction

Ladder to access top to facilitate installation and maintenance

Enclosed by squared mesh panels secure the whole drop tower from top to bottom

Drop weight

The drop weight is made of 20# steel plate. For user’s convenience, we will provide one set of special tools to facilitate loading and unloading weight increments into drop weight framework. The total weight increments of drop weight can be free adjusted, with which the user can regulate impact energy by adjusting the lifting height and quantity of the weight increments.

The hammer tip and hammer structure is separated; the hammer tip is a quick wear component, so it is easy to replace the hammer tip when necessary. The material of striking edge is 5CrW2Si and its hardness can reach HRC50－57 through heat treatment.

Heavy Duty Industrial Shock Absorber

Shock absorbers decelerate the loads quickly, gently and without any recoil or bounce back. Also, they are ideally suited for a simple and quick installation, e.g. in handling devices, rotary actuators, linear cylinders, linear cylinders and many more industrial applications.

Shock absorber bodies and inner pressure chambers are fully machined from solid high-tensile alloy steel. This gives a completely closed-end, one-piece pressure chamber with no seals or circlips being necessary. The shock absorbers are maintenance-free, self-contained hydraulic devices with the most innovative sealing technology and an extremely compact design.

Specimen Anvil and Tup

The anvil is mounted on the bottom plate, and it employs alloy 5CrW2Si who has sufficient hardness, its hardness can be up to HRC50-57 after heat treatment

Note: Tup with load cell inside is for data acquisition option (instrumented DWTT)

Winch

Easy to access for periodic inspection and maintenance

AC brushless servo motor fitted with brake, driving sling via a precision gearbox

Debris collecting system

To collect the fractured specimen and flying debris, the anvil is designed with a slope and make specimen slide along the slope and the specimens are collected on the belt at the bottom plate and then they are transported out of the tower by the conveyer belt.

Protective Cage

Protective case secures the whole operation area

Quali-TSB Series of Temperature Soak Bath (Low-Temperature Chamber & Temperature-Measuring /Controlling System

Qualitest Temperature Soak Bath system can accommodate up to 10 (optional 12 pieces) specimens of thickness up to 50mm with a minimum 26mm gap between each specimen. External construction is made from Zinc-coated mild steel sheet. External surfaces finished in stoved epoxy paint, while the internal bath and guides are made from 304-grade stainless steel.

ASFS Automatic Specimen Feeding System

Qualitest’s Automatic Specimen Feeding System available for our range of DWTT’s is pneumatically operated pick and place system with Load cycle time < 9s with an accuracy of placement of specimen within ± 0.5mm (X & Y axes)

Software

Platform: PC running Microsoft Windows XP / 7. Supplied system minimum specification of 4GB RAM, 120GB hard drive, CD-RW, 21” display.
Environment: Compatible with MS Office 2003/XP and above
Purpose: Control of impact testing sequence and analysis of impact data
Access control: Two, password-protected levels, 1) Operator access, to perform pre-defined DWTT tests. 2) Administrator access, to control the type of test performed and the required documentation information etc. also for sensitive configuration and calibration functions.
Language: The DWTT system has a Human Machine Interface that is easy to use and works in English only, other languages upon request

Safety

Safety features of this unit are compliant with the European CE machinery safety directive (89/392/EEC & 91/368/EEC – machinery safety). Electrical and mechanical safety interlocking. Testing is possible only after checking of all safety parameters, to comply with OSHA requirements (USA).

Access to specimen area protected by interlocked doors when the machine is running
Emergency stop function electrically isolates winch drive and release.
All safety systems dual circuit and fail-safe.
No unsafe release of the drop weight possible under any of the following conditions:
Failure of mains power supply
Failure of compressed air supply
Failure of control software