Thermon Electric Heat Tracing Bedienungsanleitung PDF herunterladen (Seite 8)

Electric Heat Tracing

Circuit Protection Requirements . . .

1. Over-current protection (typically circuit breakers) is

required for each branch circuit. This protection must

isolate all power conductors from the supply.

2. For typical installations (with TT and TN grounding

systems), a means of protection against earth faults is

required that includes a residual-current protective device

for each branch circuit. For ﬁ xed-level earth/ground-

fault circuit interrupters, a minimum 30 mA trip level is

recommended. The preferred trip level for adjustable

devices is 30 mA above any inherent capacitive leakage

characteristic of the heater as speciﬁ ed by the heat

tracing supplier. Where conditions of maintenance and

supervision ensure that only qualiﬁ ed persons will service

the installed systems, and continued circuit operation

is necessary for the safe operation of the equipment

or processes, earth-fault detection without interruption

is acceptable if alarmed in a manner to assure an

acknowledged response.

3. For IT grounding systems, a means of protection

against earth faults is required that includes an electrical

insulation monitoring device that shall disconnect the

supply whenever the electrical resistance is not greater

than 50 ohms/volt of rated voltage.

Thermal Insulation . . .

1. Before installing thermal insulation, insulation resistance

test should be conducted. The cable should be tested

with a test voltage of at least 500 Vdc. However,

for polymer insulated heating cables, 2500 Vdc is

recommended. The minimum acceptable level should not

be less than 20 megohms.

2. The need for properly installed and well-maintained

thermal insulation cannot be overemphasized. Without

insulation, heat losses are generally too high to be offset

by a conventional heat tracing system.

3. In addition to piping and in-line equipment such as pumps

and valves, all heat sinks must be properly insulated. This

includes pipe supports, hangers, ﬂ anges and, in most

cases, valve bonnets.

4. Regardless of the type or thickness of insulation used, a

protective barrier should be installed. This protects the

insulation from moisture intrusion, physical damage and

helps ensure the proper performance of the heat tracing

system. Seal around all penetrations through the thermal

insulation.

5. Apply “Electric Heat Tracing Caution” labels to the

insulation vapor barrier on 3m intervals or as required

by code or speciﬁ cation. The labels are supplied with

Thermon connection kits.

Final Inspection and Documentation . . .

1. After the installation of the thermal insulation and

weather barrier but BEFORE ENERGIZING THE HEATING

CIRCUIT, the insulation resistance test should be

repeated. This should call attention to any damage to

the heating cable that may have occurred during the

insulation installation.

(Record 3 on Insulation Resistance Test Page 9 and 10.)

For Series Heating Cables, measure the electric loop resistance

and record measured Ohms (Record 3 on Page 10.)

2. It is recommended that the circuit be temporarily

energized so that the volts, amps, pipe temperature and

ambient temperature may be recorded. Take the values

after 5 minutes of energizing. This information may be of

value for future reference and should be maintained for

the historical operating data log.

(Record 4 on Insulation Resistance Test Page 9 and 10)

3. Stabilized design can be used for self-regulating, power-

limiting and constant watt heating cables without a limiting

device to determine the T-class through the use of the

Thermon CompuTrace software or Thermon Engineering.

4. Series heating cable output and T-rating are dependent

upon supply voltage, cable resistance, temperature

conditions as well as additional variables through the

use of the Thermon CompuTrace software or Thermon

Engineering.

5. The maximum temperatures provided by Thermon’s

CompuTrace software and by Thermon engineering are

calculated to the methods and requirements of

EN-IEC 62086-2 and EN-IEC 60079-30.

6. If stabilized design is used, the end user must record the

system parameters and the area T-class, and keep these

records for the time the heating cable is in operation.

7. Inspect system on a regular basis at least once per year.

Record all information after conducting test. If the system

fails any test, refer to Thermon’s Maintenance and Trouble

Shooting Guide for assistance. De-energize circuits affected

and make the necessary repairs immediately.

8. Verify the setting of the maximum control device, if

provided to limit the T-rating for the circuit design, to

ensure it limits the maximum surface temperature to be in

compliance with clause 4.4.3 of EN-IEC 60079-30-1.

Maintenance and Repair . . .

1. Refer to form TEP0066-Electric Heat Tracing Maintenance

and Trouble Shooting Guide.

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