PD458
EExe CeS Increased Safety
Immersion Heater
CERTIFIED TO ATEX EN 60079-0:2006, IEC 60079-0:2006(Ed 5.0);
AND
EN 60079-7: 2007, IEC 60079-7:2007 (Ed 4.0)
CERTIFICATE No. ITS02ATEX3026X
800-443-2640
www.chromalox.com
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Table of Contents
Section
Topic
Section 1
Health and Safety ..................................................................................... 1
Section 2
General Information ................................................................................ 2
Section 3
Operation Instructions ............................................................................. 5
Section 4
Electrical Checks ..................................................................................... 6
Section 5
Fault Finding ............................................................................................. 7
Section 6
Health and Safety ..................................................................................... 8
Section 7
General Information ................................................................................. 9
Section 8
Element Replacement............................................................................ 10
Section 9
Replaceable Element ............................................................................. 11
Section 10
Removable of Element Bundle.............................................................. 12
Section 11
Removal of Bundle Elements ................................................................ 13
Section 12
New Element Replacemant ................................................................... 14
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1
Health and Safety
Attention is drawn to the Health and Safety at Work Act 1974 and all its subsequent
amendments, the regulations made under these Acts and also any other appropriate statutory requirements or by-laws. These place responsibility for complying with specific safety
requirements on the manufacturer and user.
Hazardous Environments
The heater must be installed by suitably trained personnel in full accordance with EN 60079-14:2003. This
standard defines the code of practice for the safe installation of electrical equipment in hazardous areas
other than mines.
Any persons about to perform maintenance procedures in connection with any electric heater should first
satisfy themselves as to the nature and extent of potential hazards that may be encountered.
NO WORK SHOULD BE UNDERTAKEN UNTIL ALL HAZARDS ARE REMOVED OR REDUCED TO AN
ACCEPTABLE LEVEL.
No operation involving the use of an open flame or other source of ignition should be attempted until the
condition has been made safe (gas free) by the control of the flammable material that may give rise to the
risk. Electrical test equipment can constitute a hazard and should not be used in the presence of a flammable material, unless specifically designed for the purpose and suitably certified.
Electric Shock
The electrical supply to the equipment must be switched off before removing covers from any unit where
incendive or lethally high voltages may be present.
General Safety Precautions
Ensure that the area safety supervisor and others in the vicinity are aware that work is being undertaken and
post warning notices. Ensure that the ap¬propriate safety equipment and clothing is worn. Beware of wet or
slippery ladder rungs and working areas if working aloft.
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General Information
CeS Increased Safety Immersion heaters are constructed in accordance with the requirements and specifications of Certificate ITS02ATEX3026X. The equipment may be used with flammable gases and vapours with
apparatus group II, category G2. Certified ambient temperature range –50˚C to + 55˚C only.
In certain exceptional circumstances, the marked Temperature Class on the equipment may be exceeded
either on the heater mounting flange or at the exit point of the process vessel under the designed operating
conditions. This matter must be fully understood and addressed by the user with the appropriate risk assessments carried out before commissioning the equipment.
The heaters are manufactured with great care from the highest quality materials and thoroughly inspected
before leaving our works. They must be handled with care and stored in dry conditions as befits any electrical apparatus and not exposed to wet or damp atmospheres. Before installation and commissioning it is
advisable that the elements be checked to ensure that the insulation readings are above 2 megohms per
element at 500 volts dc. If there is an unacceptable low reading on any of the elements, it will be necessary
to dry them out. For details of this procedure, please refer to the Maintenance section.
The certification of this equipment relies upon the following materials used in its construction:
•
Carbon steel
• Stainless steel
• Copper
• Brass
• Neoprene O-ring seals
• Neoprene closed cell A profile gasket
• Neoprene gasket material
The performance of these materials with regard to attack by aggressive substances shall be taken into account when installing in the hazardous area. The heater is suitable for mounting outdoors and is protected to
IP65 with 2mm thick glandplates and IP66 with 3mm thick glandplates.
P.E.D STATEMENT
This immersion heater has been manufactured, tested and inspected in accordance with the Pressure Equipment Directive (PED) 97/23/EC and classified in accordance with Sound Engineering Practice (SEP).
For details of the Fluid Category, Maximum Allowable Pressure, Maximum Working Temperature, and the
Hydrostatic Test Pressure, please refer to the Check List For The Essential Safety Requirements Of The Pressure Equipment Directive produced for this heater (or heater and vessel assembly) where applicable.
When installing heaters, sufficient clearance must be allowed for access to the terminal enclosure and to enable the heater bundle to be withdrawn from the tank or pressure vessel.
Ensure that the mains supply available corresponds with the supply voltage on the heater nameplate and
ensure that the size of supply cables, fuses and contactors are adequate for the electrical load they carry.
The heater should NOT be mounted outdoors where exposed to the weather, or where it is likely to suffer
severe shock/vibration or corrosive/dust laden environments, unless it has been specific¬ally designed for
the application.
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Incoming cables must be connected to the terminations by means of suitable cable lugs. It is essential to
ensure that they are secured from loosening or twisting, and that the contact pressure is permanently maintained. The saddle clamps provided must be used and the order of assembly of the full nuts, spring washers
and locknuts to secure them must be maintained.
It is also important to ensure that the incoming cables are properly supported independently of the enclosure
and do not impart any adverse loads upon it. They must be routed so as not to impose undue stress on the
connections or press against other terminals. Sufficient electrical clearance must exist between all conducting components of differing potential (i.e. phase to phase or phase to earth).
The minimum clearance distance between such components is 10mm.
Under normal design conditions, all incoming cables should be suitable for operation at 70oC.
Where the heater is divided into several control stages, the overheat cut-out device, in the form of either
a thermocouple or RTD, must be wired into the first heater stage, i.e. the stage which is con¬tinuously
switched on whilst the heater is energised. It must be so wired into the control system in series with the coil
of the main contactor, such that complete shut down of the heater is ensured in the event of overheating and
the supply cannot be re-energised until the system is reset. Where more than one cut-out device is fitted,
these must be wired in series.
For equipment whose design requires overheat sensors on the process flange and the back plate of the
terminal enclosure, the output from each must be included in the control system to ensure the complete shut
down of the heater if an over temperature situation were to occur.
Check that a sufficiently good earth connection is made to the heater by means of the earth facilities provided both inside and outside the terminal enclosure. Earthing is to comply with the requirements of EN 6007914:2003.
When installing the heater, the stand off area between the terminal enclosure and the mounting flange must
not be enclosed or insulated. The purpose of the stand-off is to ensure that the temperature inside the terminal box does not exceed 70oC under normal design and operating conditions. This area requires free air
circulation at all times during operation and failure to comply with this requirement will invalidate the equipment certification.
Control System Specification for Heaters Located in Hazardous Areas
a)
In addition to the usual process temperature control, all type G2 and L immersion heaters shall be
fitted with, or controlled by, an over temperature cut-out device to ensure that the process temperature and therefore the surface temperature of the flange does not exceed the values given in Table 1.
b)
All type G1 heaters shall either be rated by design for continuous operation without need for a cutout (convector or anti-condensation heaters) or as in the case of air heaters, be fitted with suitable
temperature sensors clipped to the element sheath. Such sensors shall be attached at the hottest
point within the heater, usually on the air-off side at the top of the unit with a minimum of one fitted
per phase on two of the phases of the first-on, last-off stage. The trip temperature of the sensors
shall be set no higher than the values given in Table 1.
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TABLE 1
G2 & L Classified Heaters
T6
80˚C
T5
95˚C
T4
130˚C
T3
195˚C
T2
290˚C
T1
440˚C
G1 Classified Heaters
T6
Not Permitted
T5
75˚C
T4
110˚C
T3
175˚C
T2
270˚C
T1
420˚C
When setting the trip temperature, it is important to establish beforehand, the long-term reliability of the
sensor being used and any degree of set-point drift which may occur over time. This must then be deducted
from the value given in Table 1 to ensure that the limiting temperature appropriate to the relevant T Class is
not reached or exceeded under any foreseeable circumstances
Mechanical temperature limiting devices (cut-outs) and temperature controlling devices (thermostats) may
not be fitted inside the heater terminal enclosure, but must be terminated in a suitably approved adjacent
auxiliary junction box forming part of the heater or separately within the process environment. Over temperature sensors such as thermocouples or RTDs are usually fitted via the process flange and terminated in a
separate terminal housing.
Sensors, either mechanical or electrical, must be of an established proven design and comply with the requirements of EN 954 -1
c) It is recommended that earth fault protection, (suitable for the firing method) be incorporated in the
control system.
d) When using contactor control, it is necessary to provide a ‘back-up’ contactor; one for control, the
other not normally operating for trip purposes.
e) Where SCR / SSR devices are used for power regulation, a common trip relay shall be used to interlock power supply to SCR driver instrument or primary to trigger card circuitry.
Where the control system is operating is employing a PLC, over temperature sensors must act directly on the PLC power supply and not rely on the instrument for safe shut down.
f) The over temperature system for EExe heaters must operate in all abnormal conditions and is required in addition to, and be independent from, any control system that may be necessary for the
normal operation of the equipment. The temperature high limit controllers for all EExe applications
shall be tamperproof i.e., access to the keypad or set-point adjustment is locked and where applicable, the computer adjustment is password protected.
g) For EExe applications where the element fixing pitch is less than the standard 32mm, it is necessary
to protect the heater flange and terminal box backplate temperature by high limit controllers, (operating conditions as f) above). The trip temperature of the sensors shall be set no higher than the values
given in Table 1 above and in the case of the backplate sensor, the set temperature must be determined relative to the design temperature of the heater busbar system and the thermal rating of the
incoming cables.
h) The protective systems of EExe certified equipment should de-energize the heater either directly or
indirectly. They must be of the manual re-set type and re-setting must only be possible with the aid of
a tool when the unit has returned to its normal operating condition. In the event of a sensor failing, the
control instrument must respond by de-energizing the heater.
i) The entire control system including all over temperature cut-outs must be inspected periodically to
confirm functionality and accuracy. The frequency of such inspections will be determined by experience and by manufacturer’s reliability data relating to the system components.
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Operation Instructions
Operation Instructions
The elements in the heater may be wired in a single stage or multistage configuration depending on individual customer order requirements. As such the power can be varied or switched on and off by the control panel
as the heat require¬ment varies. This may be controlled, either manually or automatically and the installer
and operator should be familiar with the type of control fitted.
All foreign matter must be removed from the process system before initial use of the heater system. Failure
to remove such matter may cause a potential hazard and result in heater failure if carried through the system
to the heater.
Anti-condensation heater – Where an anti-condensation heater is fitted, it will be of the self regulating type
and is certified on the basis that it will only be energised whilst the power to the main heater terminals is
switched off. Two types may be installed, one with the power connection terminated in a separate external
junction box and one with the power supply cable terminated inside the main heater enclosure.
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Electrical Checks
Electrical Checks Prior To Start Up
Insulation Resistance (Megger)
The megger should be applied between each phase and earth, with any control sup¬plies disconnected from
the power supply, the insulation resistance shall be measured with a voltage of not less than 500V dc and
should be above 2 meg.ohms divided by the number of heating elements. Should the insulation resistance
be below this value, then the elements should be individually checked for insula¬tion resistance to identify
those that will need drying out. For procedures see Maintenance Instructions, paragraph 8.
Continuity
Check that the ohms reading per phase on each stage are approximately equal and correct.
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5
Fault Finding
Fault Finding
If the control system cycles or trips during initial start up there may be insufficient flow. In the event of a
shutdown caused by overheating the MAIN ISOLATOR MUST BE SWITCHED OFF BEFORE any checks are
made. The pipe work should be checked for obstructions of the flow, any filters/strainers (if fitted) checked
for blockage and the control system inspected to determine the cause of the overheating BEFORE the unit is
put back into operation. Do not forget to reset any thermal cut-outs within the control system.
Always switch “OFF” the main isolator before removing either the heater terminal enclosure lid or the lid of
any auxiliary control sensor junction boxes
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Health and Safety
Health and Safety
Hazardous Environments
Any persons about to perform maintenance procedures in connection with any electric heater should first
satisfy themselves as to the nature and extent of potential hazards that may be encountered.
NO WORK SHOULD BE UNDERTAKEN UNTIL ALL HAZARDS ARE REMOVED OR REDUCED TO AN ACCEPTABLE LEVEL
No operation involving the use of an open flame or other source of ignition should be attempted until the
condition has been made safe (gas free) by the control of the flammable material that may give rise to the
risk. Electrical test equipment can constitute a hazard and should not be used in the presence of a flammable material, unless specifically designed for the purpose and suitably certified.
Electric Shock
The electrical supply to the equipment must be switched off before removing covers from any unit where
incendive or lethally high voltages may be present.
General Safety Precautions
Ensure that the area safety supervisor and others in the vicinity are aware that work is being undertaken and
post warning notices. Ensure that the ap¬propriate safety equipment and clothing is worn. Beware of wet or
slippery ladder rungs and working areas if working aloft.
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7
General Information
It is essential to periodically check all the electrical connections in the terminal enclosures for tightness and
to ensure that there are no signs of overheating, etc.
Recommended minimum tightening torques for busbar fastenings are as follows
M5
M6
M8
2.5 Nm
7.2 Nm
17 Nm
M10
M12
M16
28 Nm
45 Nm
91 Nm
The minimum electrical clearance between conducting components of different potential (i.e. phase
to phase or phase to earth) is 10 mm; on no account must the heater be energised if this requirement
has not been complied with.
A recommended method of checking the condition of all connections within the terminal enclosure is the use
of a suitable thermal imaging camera. Regular monitoring will highlight any areas requiring attention.
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Heating Elements
Heating Elements
Heating elements should periodically be examined to ensure insulation and continuity readings are satisfactory if the heater has been shutdown for any length of time.
If there is an unacceptably low insulation reading on any of the elements, it will be necessary to dry them out
either by using the following procedure or by returning the complete heater bundle to Chromalox for drying
out at the factory. (Please see note on page 8)
Remove the ceramic sealing bead from each end of the element.
Completely scrape out the silicone sealing compound down to the white pow¬dered magnesium oxide.
Ensure that all loose debris is removed from the element ends.
Connect the elements to a low voltage (either 50v d.c. or 24v a.c.) supply and heat the element to between
100°C and 200°C and drive out the moisture. This operation should be continued for approximately 12 hours
or until the resistance to earth is greater than 2 meg.ohms.
Important Note: Priming of element ends should be carried out as soon as possible after drying out to avoid
ingress of moisture.
Eltron Primer (part number 112470) is to be applied to the elements ends, i.e. to the internal face of the
sheath, the surface of the dead within the sheath and the surface of the insulant (magnesium oxide).
A thin film of the primer will give the best seal. Film thickness can be estimated by the colour; the thicker the
film, the darker the tint. The cor¬rect thickness should only give a pale tinge to the surface.
Allow the primer to cure at normal temperature and humidity conditions for 1 hour before sealing the elements.
Fill the end cavity with Eltron Silastic sealing compound (part number 113800) to ensure complete potting.
Fit sealing bead by pushing down and rotating (to ensure wiping of bead) until it is seated in the top of the
element sheath.
Fit clamping nut above sealing bead (half nut).
Wipe excess sealant from around joint of bead.
Allow sealant to cure for a minimum of 24 hours before subjecting to any inspection/running procedures.
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Cables
Cables
Check all incoming cables for damage and replace where necessary.
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Removal of Element Bundle
Removal of Element Bundle
If it is required to remove an element, the heater bundle must be removed from the tank or vessel to gain access for the repair. The weight of the bundle assembly will be stated on the manufacturing drawing and may
also be stamped on the mounting flange. The heater must be withdrawn as a unit using the flange lifting lugs
to support it as it is withdrawn. To accomplish this, proceed as follows:
Isolate heater from supply.
Remove the terminal enclosure cover.
Disconnect the supply cables and remove them from the glands.
Unbolt the pressure flange and withdraw the heater (assuming that the vessel or tank has been drained beforehand).
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Removal of Bundle Elements
Removal of One or More Elements from Bundle
If it is necessary to remove an element, proceed as follows:
The heater is fitted with a stood-off terminal enclosure and weatherproof glands are used where each element leg enters the enclosure. In order to remove individual elements, the terminal box must be removed.
First disconnect the busbars and remove them having first noted their exact posi¬tioning, relative to the element terminals. Where black nylon sealing glands are used, undo each gland top nut and take out the rubber
compression seal and skid washer (the seals cannot be re-used and should be replaced with new items
upon re-assembly).
For enclosures operating at higher temperatures a plated brass gland is used; the top nut and o-ring seal
must be removed before unscrewing the gland body from the enclosure backplate together with it’s sealing
washer.
When all the glands have been dismantled as above, the stand-off fixings can be undone and the terminal
enclosure removed.
Before removing an element check that it has no thermal cut-out sensor attached. If it has, this will have to
be released before proceeding.
The elements are fitted to the pressure flange by means of ‘bite’ couplings; to release an element will require
a special extended reach socket spanner to undo the top nut of the coupling. It will then be necessary to cut
through the ‘bite’ olive on each element leg before it can be withdrawn through the flange.
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New Element Replacement
Replacement Of New Element
Replacement spare elements will be provided with two ‘bite’ olives and two top nuts. Rubber sealing washers will also be supplied where appropriate.
Elements fitted with “bite” glands can be refitted as follows:
a) Insert the element through the ‘bite’ coupling bodies in the terminal plate.
b) Ensure the element passes through the plate by the same amount as the others in the flange.
c) Put one olive followed by a top nut on each element leg and then do up finger tight onto each gland
body.
d) Each top nut should then be tightened one and a quarter turns, which is equivalent to a torque of 35
foot pounds force (47.5Nm). This will cause the olive to bite onto the element sheath. Take care that
the element does not move or twist in the gland whilst tighten¬ing the nut.
Replace terminal enclosure.
Replace weatherproof gland top nuts and new rubber seals where appropriate.
Refit the busbar assembly.
Refit thermal cut-out sensor and spacer assembly, where fitted.
Refitting the heater bundle into the vessel or tank is the reversal of the dismantling procedure.
Re-connect supply cables, ensuring that all connections are made properly.
Recheck electrically and visually. Ensure that sufficient electrical clearance exists between all conducting
components of differing potential (i.e. phase to phase or phase to earth).
The minimum clearance distance between such components is 10mm.
Ensure that all gland plates, where fitted, and terminal covers are secured before the supply is switched on.
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