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QUALITY

DVD QUALITY POLICY

"to supply its customers with consistent and reliable products that are technologically ahead of its competitors. To supply these products on time, leading to high satisfaction of customers and getting their well reserved trust"

QUALITY ASSURANCE

To comply with the quality policy, DVD holds quality certificates that are valid throughout the world. Moreover, DVD manufactures its products following the quidelines of ISO 9001 quality control system, which DVD has been approved so by TSE & LLOYDS.

 


Material Hardness Tests
DVD Valves works with foundries which proved their quality in the market. Selection and evaluation of these foundries are done as specified in DVD Valves Quality Handbook. Furthermore, to make sure of the quality level of all supplied castings, DVD Quality Procedures provide a special acceptance procedure for incoming material. One of these procedures is to measure the hardness of the castings. DVD Quality Control Staff checks the hardness of the incoming castings in regular intervals and records these data for future references. If the hardness of the material is not suitable, castings are rejected from start.



Wall Thickness Tests
Another testing done for the castings is the Wall Thickness Test. With a special ultrasonic thickness device, wall thicknesses of the items are measured according to EN 15317 in regular time intervals. The device records the minimum thickness over a profile and engineers check these data whether they are suitable or not with regards to the drawings. If for any reason such as a mould problem or a casting problem, thicknesses are very low, necessary actions are taken by the responsible department.



Machined Surface Profile Roughness Tests:
DVD Valves works with fully automated CNC Machining Centers. However, even with fully automated machines, due to some reasons such as worn tools, surface profile of the machined item can pass tolerances. To make sure that our customers receive a clean machined surface, Quality Control Engineers measure the profile of the surface and documents it on computer according to DIN EN ISO 3274. With the surface data of the surface, engineers can see the variance of the profile and act immediately if the variances pass tolerances. Therefore, Production Department takes necessary precautions. Machined Surface Profile Reports can be sent according to customer request.



Dimensional Checks
DVD Valves has embraced the Built-in Quality concept for quality control. Every operator is responsible to make the necessary dimensional checks which they manufacture. Plus, quality control staff checks these values in regular intervals.



3 Dimensional Measurement Device
In regular intervals, samples from machined valve bodies are taken to measurement room where machined surface dimensions are checked. For large sizes, portable computurized measurement arm is used for measurement. These devices have very low tolerances and all dimensional readings are recorded on computer. DVD Valves provide Dimensional Control Reports generated with the software to the customers on request.



Surface Roughness Tests
After the Sand Blasting Process, the surface profile of the valve should be checked whether its roughness is appropriate or not according to ISO 8503-1. Therefore, DVD Quality Control Department checks sample valves coming out of the blasting process randomly to make sure all items are blasted according to the ISO standards.



Dew point Tests
At the time of application of coating to the metal surface, the presence of moisture in the area and on the valve part can result in very poor quality of coating and as a result, very weak bonding and premature corrosion can occur. DVD Quality Procedures prevent such a situation by measuring dew point of the environment at all times. When the moisture content of the environment passes a limit, fully automated testing equipment provides an alarm so that there will not be any coating at that stage. All temperature and dew point data are recorded in the environment as standard.



Coat Thickness Tests
In regular intervals, DVD Quality Control Staff checks the thickness of coating for valves. DVD standard for coating is 250 microns. Higher thickness can be realized according to customer request.



Cross-cut Test
The adhesion of the coating is tested by Cross-cut Test according to EN ISO 2409. In this test, a shape similar to X is scribed on the valve body with a special cutting equipment to the metal substrate. Then, a tape is stick on the X and it is lifted off. If there is any damage on the coating, it means that there is something wrong with the application of the coating and necessary actions are taken accordingly.



Spark Test
To make sure that there is no porosity on the coating which causes an infiltration, the coating is checked by a Spark Test. By giving 3000 Volts on the body, if there is any porosity, metal substrate conducts electricity which causes an alarm on the test device. No conduction means there is no porosity on the coating.



Sponge Test
In large size valves, porosity of the coating is checked by a Sponge Test where high voltage is given on the body and conduction is checked by a wet sponge device. This allows the quality control staff to be able to check a wider area at a single time.



Hydrostatic Tests
Every single valve manufactured by DVD go into hydrostatic test process without any exceptions. With the hydrostatic tests, Shell Tightness and Seat Tightness are guaranteed. Hydrostatic tests are done according to EN 12266-1.



Low Pressure Sealing Test
All valves are tested for low pressure sealing as well. DVD Check Valves and Air Valves can provide sealing even below 2 meter pressure.



Torque & Mechanical Strength Tests
With a special device, opening and closing torque values of the valves are measured and recorded for customer use. Furthermore, mechanical strength tests are done on the valves in design stage. This test is applied to the spindle of the valve for making sure that the valve assembly will withstand a high closing or opening torque. The valve is forced to close when the valve is already in closed position and the valve is forced to open when the valve is already in open position. At the end of the test, the operation of the valves is checked.



Bending Tests
All the valves manufactured from Ductile Iron material have to go through a Bending Test in the design stage according to EN 1074-2. In this test, by a piston, the valve body is bended and it is seen that the valve operates and provides sealing even after the test. This is a simulation for an earthquake situation.



Life Time Cycle Tests
Every DVD product has to pass from a Cycle Test in design stage according to EN 1074-2. Cycle Test applies the workload which the valve will face through its predicted life time. The valve is opened and closed with a motor for the number of times the valve will face through its life time. As a result of this test, the endurance of the sealing system is checked and it is guaranteed that it will function and provide drip tight sealing even after the cycle test.



Computurized Hydraulic Laboratory - Flow Characteristic Test
All applicable valves are installed on the dynamic test bench which is fully operated by a special software. In this test bench, pressure loss data, Kv value calculation and flow/pressure regulation characteristics of the valve can be tested. With sensors on the bench, upstream/downstream pressure and flow values can be seen in real time and can be recorded for future reference.



3.1B & Test Certificates:
As standard, for all customer orders, DVD Valves provides 3.1B Certificates and Test Certificates. 3.1B Certificates provide data about the chemical composition of the casting, and Test Certificates provide data about hydrostatic tests, coating thickness, marking, materials of the items etc. All tests are done in-house. However, if the customer requires 3rd party inspections, DVD Valves can arrange a 3rd part inspection according to customer demands. For all other testing processes specified above, customers can request test reports for their orders.



 
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