73A. [ Ovens and Driers. [Inserted/Substituted by Notification No. 4(a) 4-91-16B, dated 6-4-1995.]
- (1) Application. - This rule shall apply to ovens and driers, except those used in laboratories or kitchen of any establishment and those which have a capacity below 325 litres.(2)Definition. - For the purpose of this rule, oven or drier means any enclosed structure, receptacle, compartment or box which is used for baking, drying or otherwise procession of any article or substances at a temperature higher than the ambient temperature of the air in room or space in which the oven or drier is situated, and in which a flammable or explosive mixture of air and a flammable substance is likely to be evolved within the enclosed structure, receptacle, compartment or box or part thereof on account of the article or substance which are baked, dried or otherwise processed within it.(3)Separate electrical connection. - Electrical power supplied to every oven or drier shall be by means of a separate circuit provided with in isolation switch.(4)Design, Construction, examination and testing. - (a) Every oven or drier shall be properly designed on sound engineering practice and be of good construction, sound material and adequate strength free from any patent defects and safe if properly used;(b)No oven or drier shall be taken into use in a factory for the first time unless a competent person has thoroughly examined all its part and carried out the tests as are required to establish that the necessary safe system and controls provided for safety in operation for the processes for which it is to be used and a certificate of such examination and tests signed by that competent person has been obtained and is kept available for inspection;(c)All parts of an oven or drier which has undergone any alteration or repair which has the effect of modifying any of the design characteristics, shall not be used unless a thorough examination and tests as have been mentioned in clause (b) has been carried out by a competent person and a certificate of such examination and tests signed by that competent person has been obtained and is kept available for inspection;(d)Competent person for the purpose of this rule shall be the person who is graduate or diploma engineer in electrical or mechanical branch and has atleast 5 years working experience of designing or manufacturing or repairing and maintenance of such equipments.(5)Safety Ventilation. - (a) Every oven or drier shall be provided with a positive and effective safety ventilation system using one or more motor-driven centrifugal fans so as to dilute any mixture of air and any flammable substance that may be formed within the oven or drier and maintain the concentration of the flammable substance in the air a safe level of dilution.(b)The safe level of dilution referred to in clause (a) shall be so as to achieve a concentration of the concerned flammable substance in air of not more than 25 per cent of its lower explosive limit :Provided that a level of concentration in air upto 50 per cent of the lower explosive limit of the concerning flammable substance may be permitted to exit subject to installation and maintenance of an automatic device which-(i)shows continuously the concentration of the flammable substance in air present in the oven or drier at any instance;(ii)sounds an alarm when the concentration of the flammable substance in air in any part of the oven or drier reaches a level of 50 per cent of its lower explosive; and(iii)shuts down the heating system of the oven or drier automatically when the concentration in air if the flammable substance in any part of the oven or drier reaches a level of 60 per cent of its lower explosive limit, is provided to a oven or drier and maintained in efficient working condition.(c)No oven or drier shall be operated without its safety ventilation system working in an efficient manner.(d)No oven or drier shall be operated with a level of dilution less than what is referred to in clause (b).(e)Exhaust dusts of safety ventilation system should be so designed and placed that their dust discharge the mixture of air and flammable substance away from the work-rooms and not near windows or doors or other openings from where the mixture could re-enter the work-rooms.(f)The fresh air admitted into the oven or drier by means of the safety ventilation system shall be circulated adequately by means of circulating fan or fans through all parts of the oven or drier so as to ensure that there are no locations where the flammable substance can accumulate in the air become pocketed to any dangerous degree.(g)Throttling dampers in any safety ventilation system should be so designed by cutting away a portion of the damper or otherwise, that the system will handle atleast the minimum ventilation rate required for safety when they are set in their maximum throttling position.(6)Explosion panels. - (a) Every oven or drier having an internal total space of not less than half cubic meter shall be provided with suitably designed explosion panels so as to allow release of the pressure of any possible explosion within the oven or drier through explosion vents. The area of openings to be provided by means of such vents together with the area of opening of any access doors which are provided with suitable arrangements for their release in case of an explosion, shall be not less than 2200 square centimeters for every one cubic meter of volume of the oven or drier. The design of the explosion panels and doors as above said shall be such as to secure their complete release under an internal pressure of 0.25 kg per square centimetre.(b)The explosion releasing panels, shall, as far as practicable, be situated at the roof of the oven or drier or at those portions of the walls where persons do not remain in connection with operation of the oven or drier.(7)Interlocking arrangements. - In each oven or drier efficient inter-locking arrangements shall be provided and maintained to ensure that-(i)all ventilating fans and circulating fans whose failure would adversely effect the ventilation rate or flow pattern, are in operation before any mechanical conveyor that may be provided for feeding the articles or substances to be processed in the oven or drier is put into operation;(ii)failure of any of the ventilating or circulating fans will automatically stop any conveyor as referred to in clause (i) as may be provided, as well as stop the fuel supply by closing the 'shut off valve and shut off' the ignition in the case of gas or oil fired ovens, and in the case of electrically heated ovens switch off the electrical supply to the heaters;(iii)the above said mechanical conveyor is set in operation before the above said shut-off valve can be energised; and(iv)the failure of the above said conveyor will automatically close the above said shut off valve in the case of ovens and driers heated by gas, oil or steam and deactivate the ignition systems, or cut off the electrical heaters in the case of electrically heated ovens or furnaces.(8)Automatic preventilation. - Every oven or drier heated by oil, gas, steam or electricity shall be provided with an efficient arrangement for automatic preventilation consisting of atleast 3 volume changes with fresh air by operation of the safety ventilation fans and the circulating fans (if used) so as to effect purging of the oven or drier of any mixture of air and a flammable substance before the heating system can be activated and before the conveyor can be placed in position.(9)Temperature Control. - Every oven or drier should be provided with an automatic arrangement to ensure that the temperature within does not exceed a safe upper present limit to be decided in respect of the particular processing being carried on.(10)Multistage processes. - Wherever materials are to be processed in ovens or driers in successive operations, suitable arrangement should be provided to ensure that the operating temperatures necessary for safe operation at each stage are maintained within the design limits.(11)Combustible substances not to drip on electrical heaters or burners flames. - Effective arrangements shall be provided in every oven or drier to prevent (dripping of combustible substances on electric heater or burner flame used for heating.(12)Periodical examination testing and maintenance. - (1) All parts of every oven and drier shall be properly maintained and thoroughly examined and the various controls as mentioned in this rule and working of the oven or drier tested at frequent intervals to ensure its safe inter-operation by a responsible person designated by the occupier or manager who by his experience and knowledge of necessary precautions against risks of explosion, is fit to undertake such work.(b)A register shall be maintained in which the details of the various tests carried out from time to time under clause (a) shall be entered and every entry made shall be signed by the person making the tests.(13)Training of operations. - No person shall be assigned any task connected with operation of any oven or drier unless he has completed 18 years of age and he is properly trained.(14)Polymerising machines. - (a) Printed fabric shall be thoroughly dried by passing them over drying cans or through hot flue or other equally effective means, before the same is allowed to pass through polymerising machines.(b)Infra-red ray heaters of polymerising machines shall be cut-off while running the prints.]
