Quality controls is concerned with three main aspects :-
1) Quality of materials
2) Quality of components and
3) Quality of finished products (valves, pipes and fittings)
Quality controls should not be confused with quality assurance. The latter is concerned with ensuring that the quality control and systems used are maintaining the standard specified.
Basic quality control requirements are indicated, but not necessarily specified by standard specification to which the valves is made or covering valve for similar application. If the valve is such that it is not covered by a particular standard or specification, then those valves are manufactured according to requirements and application of the buyer. In regular production, careful control of materials supplied, visual and dimensional inspection of components and pressure testing of the final valve at ambient temperature will be sufficient.
The extents of quality control to be applied in the manufacturing of a valve should be determined primarily in relation to its application. We generally, apply quality control appropriate to the normal uses of such valves. We readily advise to our factory the standard control procedure for particular valves and this should prove more than adequate for most of the purposes. Obviously, this will vary according to the type of valves, being more exhaustive for a high-pressure steam valve than for bronze radiator valve. Where valves are of special designed, made of special material as compared with normal production or critical services, then more exhaustive quality control may be considered desirable. Such cases should be discussed in detail with prospective buyers.
It is necessary to ensure that materials used are as specified and they are in suitable condition for the purpose intended. The latter will involve general inspection and or may include non-destructive testing procedures in appropriate to form, such as ultrasonic testing, radiography and crack detection. The scope and extend of NDT should be determined in relevant to the severity and hazard of end use of the valves. For items in regular mass production, some form of sample is often used as material quality control and again the extent of testing is determined by the intended purpose of valve.
When materials quality control has been applied, quality control on components is basically one of inspection against the design requirements. Again the applicant of total inspection or the use of sample must be determined by circumstances.
FINISHED VALVES, PIPES AND FITTINGS
Here quality control is concerned with satisfactory operation and function of valve in accordance with the specification operation and function of valve in accordance with the specification to which it is made. This will involve both inspection and testing. Usually including Hydraulic pressure testing, both body and seat where valves have a primarily shut-off function.
Many valve specifications including British standard require that there shall be no visual leakage through the valves seat under specified test condition. In practice, it is appreciated that test carried out under different condition.
Some valve product standard has acknowledged the impractibility of zero seat leakage concept for certain industrial valves and in this maximum leakage rates are specified. Specified permissible leakage should be based on process consideration, such as hazard resulting from leakage after emergency shut-off etc. In many industrial applications, some degree of degree of leakage is acceptable and permissible.
All aspects of quality control, inspection and testing should be carefully weighed against the application and hazard associated with the service of the valves. Caution should be exercised to avoid over specification, which can result in an unnecessarily expensive product and which may reduce source of available and extend the delivery time.
Any requirement for quality control (for materials and test certificates, if they are thought to be necessary) should be discussed and agreed with the supplier at the time of order, changes made after work as commenced may lead extension of delivery times.
It is controlled by one of our department called as 'QUALITY CONTROL DEPARTMENT' headed by an Engineer as Quality Manager, having inspectors and Supervisors under him. All are responsible to reply direct to the Chief Manager or Managing Director.
The system used in our factory has following sections :-
1) Control of drawing and changes.
2) Procurement Control
3) In-Process Inspection
4) Special Process control
6) Corrective Action
7) Final Inspection
8) Painting and Packing
Each employee is responsible for the quality of the contributes to the product, either directly or indirectly. Quality Control Department is responsible for inspection of the materials at receiving section, during manufacturing and assembly and for acceptance of finished products.
It is divided into four parts :-
a) Ferrous castings for all Cast Iron parts of the valves. These items are manufactured in our Foundry at 245 'K' road, Belgachiya, Howrah. Raw materials used to manufacture Valves and fittings meet standard is Cast Iron to IS:210 gr. 200. The Quality Control foundry engineer specifies Heat No. of all castings. Each heat has testing bar either integrally cast with body or separately marking Heat No. After casting and fatling the test bar is detached from casting and sends to laboratory at our factory P-280 Banaras Road, Belgachiya, Howrah, where our Laboratory In-charge carries the test of Cast Iron part and testing bar as per specification on universal testing machine to find out grade and quality. After satisfaction, he issues instructions to the factory, receiving section to receive the materials from foundry with identification mark. After receiving the castings, again the Inspection Engineer check each part on sound prove to issue to supervisor for machining.
b) For non-ferrous items of Valve such as trims for body and seat, nuts, bushes etc., we have foundry for non-ferrous at our factory at 60/1/1 'O' Road, Howrah where similar type of arrangements as stated above have been made and same system to receive non-ferrous castings after carrying the test, as per specification for mechanical and chemical reports.
c) Stem materials, generally, we purchase from recognized stockist such as stainless steel rounds/bars from indigenous manufacturers who issue test certificate with materials for gradation, chemical composition, UTS as specified in specification and after receipt, we again test in our own laboratory for chemical and mechanical properties of stem materials and satisfaction we put for further operation.
d) BOUGHT OUT ITEMS: We purchase from lacal indigenous manufacturers/stockist bolts, nuts, rubber insertion, compressed fiber packing etc. as given specification.
e) After receiving all materials and after machining our inspecting engineers check each and every parts dimensionally as per drawing and specification and on satisfaction they put forward to assembly section. During inspection, if any material in not qualified and observes below specification, instantly Quality Control Manager makes a report and rejects with marking and tag and set aside for disposition. The control and disposition of non-conformities is the responsibility of Quality Control Department.
f) ASSEMBLY: On time of assembly all parts related to make Valve are kept in inventory section and reinspected by assembly section engineer and after assembly, the operation of valves are observed to see the strength, clearance setting of valves and other facts. And on satisfaction, the assembly department releases the valves for testing hydraulically. After hydraulic testing, as specified in specification and on satisfaction, the Valves are use to transfer for painting and finishing, and after that the valves are transferred to dispatch section or offered for inspection to the buyers nominated inspection agencies for quality assurance and acceptance of the materials. Generally the materials are finally inspected and accepted and released for dispatch/shipment after full satisfaction and meeting the requirement as per satisfaction and order. Inspection are generally carried out by the under noted independent third party inspection from time to time.