Answer SSEP Question 21
Q21.
With respect to the hazardous areas of tankers,
The Ex Certification label and equipment rating label must not be painted over. Remember that no alterations to the Exd equipment are allowed without permission from the Certification Authority. This applies also to the lamp size aid its rating for a particular light fitting it must have the correct lamp fitted. Some pump rooms have pressurized light fittings (marked Exp on the Certification label). Here it is necessary to confirm that the fittings are purged and pressurized before the light is allowed to be switched on. Similarly the lights should automatically be switched off if the air pressure drops below its set value. Electrical instrumentation and communication equipment used in hazardous areas must be intrinsically safe (marked Exi on the Certification label).
In most cases/zener barriers, are connected in line with intrinsically safe circuits and are fitted in a safe area just outside the hazardous area. The surveyor cannot easily test zener barriers in situ as this would involve special equipment and it is generally accepted that such protection equipment will function correctly when circuit fault conditions arise. This is no different to accepting that a fuse will blow when a short-circuit occurs. However, the surveyor will visually inspect the zener barrier installation. The barriers must have secure connections
and be properly bolted to an earth strap, which in turn, must be solidly bonded to the ship's hull.
The most common form of hazirdous area electrical equipment is the flameproof enclosure type (marked Exd on the equipment certificate label). The internal apparatus may include parts which are and surfaces become hot. Outside flammable gas may seep inside the enclosure skit must fulfil three conditions:
(1) The enclosure must be strong enough to withstand and internal explosion without suffering.
(2) The enclosure must prevent the flame and hot gases from being transmitted to the external if flammable atmosphere.
(3) The external surface temperature/ of, the enclosure must retain below the ignition temperature of the surrounding gas under all operating conditions.
The transmission of flame and hot gases from a flame proof enclosure is prevented because all joints, such as flanges, spigots, shafts and bearings are closely machined to achieve a small gap which is less than a defined maximum.
The pressure of an internal explosion is then released through the small gap between machined face which cools the gas sufficiently to prevent it from igniting any external flammable atmosphere.
The maximum gas depends upon three factors:
(1) The type of gas which the apparatus is safe for use. This is indicated by apparatus Group.
(2) The width of the joint.
(3) The volume of the enclosure.
B. State the type of electrical equipment that would be protected in this way.
This type of enclosure will be found on light-fitting, motors, starters, push-buttons and alarms within the hazardous zones.
C. List likely defects of flameproof equipment.
The flame proof enclosure surface should be maintained in clean condition (which affects the surface temperature), corrosion should be prevented and mountings to be properly secured. On lighting fitting the cement that bonds the lamp glass to its frame must be closely inspected for cracks or indentation. All bolts must be in place, evenly torque-up and correct type. The edges of flame path flanged joints must not be painted over or impeded in anyway. Exposed flame proof equipment on deck must be made weather proof With the correct (approved) gaskets or "O" rings in place. All Exd Fitting to the Exd. Equipment is allowed without permission for certification authority. This applies to the lamp size and its rating for particular light fitting - it must have the correct lamp fitted.
A. Explain the term
flameproof (Ex d) for electrical equipment;
B. State the type of
electrical equipment that would be protected in this way.
C. List likely
defects of flameproof equipment.
Answer: A. Flame proof for electric equipments with respect to the hazardous areas of tankers:
Electrical equipment in the hazardous areas of oil/gas carriers and other ships carrying potentially dangerous cargo will be surveyed during the normal engine survey (every four years) and during docking and annual surveys. Consequently, the hazardous area electrical equipment is effectively surveyed every year. The most common form of hazardous area electrical equipment is the flameproof enclosure type (marked Exd on the equipment certification label). This type of enclosure will be found on light fittings, motors, starters, push-buttons and alarm bells within the hazardous zones.
Electrical equipment in the hazardous areas of oil/gas carriers and other ships carrying potentially dangerous cargo will be surveyed during the normal engine survey (every four years) and during docking and annual surveys. Consequently, the hazardous area electrical equipment is effectively surveyed every year. The most common form of hazardous area electrical equipment is the flameproof enclosure type (marked Exd on the equipment certification label). This type of enclosure will be found on light fittings, motors, starters, push-buttons and alarm bells within the hazardous zones.
The
flameproof enclosure will be inspected for surface cleanliness (which
affects the surface temperature), corrosion and secure mountings. On
lighting fittings the cement that bonds the lamp glass to its frame must
be closely inspected for cracks or indentations.
All bolts must be in place, evenly torqued-up and of the correct type. The edges of flamepath flanged joints must not be painted over or impeded in any way. Exposed flameproof equipment on deck must be adjudged weatherproof with the correct (approved) gaskets or "O" rings in place. An Exd fitting may be opened up to check the condition of its flamepath surfaces for corrosion, pitting or scratch marks as shown in Figure.
All bolts must be in place, evenly torqued-up and of the correct type. The edges of flamepath flanged joints must not be painted over or impeded in any way. Exposed flameproof equipment on deck must be adjudged weatherproof with the correct (approved) gaskets or "O" rings in place. An Exd fitting may be opened up to check the condition of its flamepath surfaces for corrosion, pitting or scratch marks as shown in Figure.
The Ex Certification label and equipment rating label must not be painted over. Remember that no alterations to the Exd equipment are allowed without permission from the Certification Authority. This applies also to the lamp size aid its rating for a particular light fitting it must have the correct lamp fitted. Some pump rooms have pressurized light fittings (marked Exp on the Certification label). Here it is necessary to confirm that the fittings are purged and pressurized before the light is allowed to be switched on. Similarly the lights should automatically be switched off if the air pressure drops below its set value. Electrical instrumentation and communication equipment used in hazardous areas must be intrinsically safe (marked Exi on the Certification label).
In most cases/zener barriers, are connected in line with intrinsically safe circuits and are fitted in a safe area just outside the hazardous area. The surveyor cannot easily test zener barriers in situ as this would involve special equipment and it is generally accepted that such protection equipment will function correctly when circuit fault conditions arise. This is no different to accepting that a fuse will blow when a short-circuit occurs. However, the surveyor will visually inspect the zener barrier installation. The barriers must have secure connections
and be properly bolted to an earth strap, which in turn, must be solidly bonded to the ship's hull.
The most common form of hazirdous area electrical equipment is the flameproof enclosure type (marked Exd on the equipment certificate label). The internal apparatus may include parts which are and surfaces become hot. Outside flammable gas may seep inside the enclosure skit must fulfil three conditions:
(1) The enclosure must be strong enough to withstand and internal explosion without suffering.
(2) The enclosure must prevent the flame and hot gases from being transmitted to the external if flammable atmosphere.
(3) The external surface temperature/ of, the enclosure must retain below the ignition temperature of the surrounding gas under all operating conditions.
The transmission of flame and hot gases from a flame proof enclosure is prevented because all joints, such as flanges, spigots, shafts and bearings are closely machined to achieve a small gap which is less than a defined maximum.
The pressure of an internal explosion is then released through the small gap between machined face which cools the gas sufficiently to prevent it from igniting any external flammable atmosphere.
The maximum gas depends upon three factors:
(1) The type of gas which the apparatus is safe for use. This is indicated by apparatus Group.
(2) The width of the joint.
(3) The volume of the enclosure.
B. State the type of electrical equipment that would be protected in this way.
This type of enclosure will be found on light-fitting, motors, starters, push-buttons and alarms within the hazardous zones.
C. List likely defects of flameproof equipment.
The flame proof enclosure surface should be maintained in clean condition (which affects the surface temperature), corrosion should be prevented and mountings to be properly secured. On lighting fitting the cement that bonds the lamp glass to its frame must be closely inspected for cracks or indentation. All bolts must be in place, evenly torque-up and correct type. The edges of flame path flanged joints must not be painted over or impeded in anyway. Exposed flame proof equipment on deck must be made weather proof With the correct (approved) gaskets or "O" rings in place. All Exd Fitting to the Exd. Equipment is allowed without permission for certification authority. This applies to the lamp size and its rating for particular light fitting - it must have the correct lamp fitted.
All good
ReplyDeleteThanks
I love it
Simple and informative ❤❤