5 Main Performance Parameters

5.1 Low temperature series performance parameters

- Standard color: Black

- Temperature range: maximum maintained temperature of 65 ℃

Maximum exposure temperature 85 ℃

Maximum surface temperature 85 ℃

- Construction temperature: minimum -60 ℃

Thermal stability: After cycling back and forth 300 times between 10 ℃ and 99 ℃, the cable's heat generation remains above 90%.

Bending radius: 25.4mm at room temperature of 20 ℃ and 35mm at low temperature of -30 ℃.

- Insulation resistance: When the length of the heat tracing cable is 100m and the ambient temperature is 75 ℃, the minimum insulation resistance is 20M Ω.

5.2 DWK Heat Tracing Cable Power Temperature Operating Curve (Power Supply 220Vac),

5.3 Medium temperature series performance parameters

- Standard color: Brown

- Temperature range: maximum maintained temperature of 105 ℃

Maximum exposure temperature 135 ℃

Maximum surface temperature 135 ℃

- Construction temperature: minimum -30 ℃

- Thermal stability: After cycling back and forth 300 times between 10 ℃ and 149 ℃, the cable's heat generation remains above 90%

Bending radius: 25.4mm at room temperature of 20 ℃ and 35mm at low temperature of -30 ℃.

- Insulation resistance: When the length of the heat tracing cable is 100m and the ambient temperature is 75 ℃, the minimum insulation resistance is 20 M Ω.

5.4 ZWK Heat Tracing Cable Power Temperature Operating Curve (Power Supply 220Vac), see Figure 2

5.5 The selection of fuses and the maximum length of a single power supply are shown in Table 2

Table 2: Selection and Maximum Length of Fuses

Cable model specification Starting temperature ℃ Fuse

10A 20A 30A 40A

Maximum usage length of a single power supply (m)

15DWK2-J -20-100+10 

25DWK2-J -20-100+10

35DWK2-J -20-100+10

40ZWK2-J -20-100+10

50ZWK2-J -20-100+10

60ZWK2-J -20-100+10

6 uses

- Parts or places that require anti freezing, ice melting, snow melting, and anti condensation.

- Heat tracing insulation, viscosity reduction, and blockage prevention for pipelines, valves, pumps, containers, tanks, tanks, reactors, etc. that are prone to liquefaction, solidification, crystallization, and viscous liquids. Such as gas, chlorine gas, crude oil, heavy oil, edible oil, and water pipes, especially when the above pipelines are intermittently operated and cannot be completely emptied.

The branch pipe of the measuring instrument is thin and the material does not flow.

- No need for precise constant temperature instruments, components, and limited temperature heating with low power.

- Processing of agricultural and sideline products and other uses, such as fermentation, hatching, breeding, etc.

7 Precautions for use

During transportation, storage, installation, and use, it is necessary to avoid crushing, impact, repeated bending, and the invasion of organic solvents or oil stains.

One end of the cable is connected to the power supply, and the wire core at the other end must not be short circuited or in contact with conductive substances. It must be tightly sealed with a matching head. In situations where explosion-proof is required, a matching explosion-proof junction box should be used. The sheath shall not be damaged, and the core tape shall not be exposed.

The output power of the heat tracing cable is related to many factors of the heat tracing system, and thermal design must be carried out when using the heat tracing cable to achieve the operating effect.

8 Simple Thermal Design

Electric heat tracing is the use of heat output from heat tracing cables to compensate for the heat dissipated by storage and transportation systems such as pipelines, containers, and tanks, in order to maintain the operating medium of the system at the appropriate temperature range required by the process. So, in thermal design, the first step is to determine the heat loss or heat consumption of the process equipment, and then determine the power and length of the required heat tracing cables based on the heat consumption.

8.1 Process parameters that need to be determined in the design

1) Maintenance temperature required for pipelines, TV;

2) Local minimum ambient temperature (℃), TA;

3) The outer diameter of the pipeline, D;

4) The surface area of the container, S;

5) Types and thicknesses of insulation materials for pipelines;

6) The pipeline is located indoors or outdoors.

8.2 Calculation of Pipeline and Plane Heat Loss

8.2.1 Pipeline

The heat loss of the insulated pipeline (with a 30% safety factor added) is calculated according to formula (1):

Qt={[2π(TV-TA) ]/［( LnD0/D1）1/λ+2/( D0α)]}×1.3 ………(1)

8.2.2 Plane

The heat loss of the insulation plane (with a 30% safety factor added) is calculated according to formula (2):

QP=[(TV-TA)/(δ/λ+1/α)] ×1.3 ……………………………(2)

In equations (1) and (2):

Qt - Heat loss per unit length of pipeline, W/m;

Qp - heat loss per unit plane, W/㎡;

TV - Maintenance temperature required by the system, ℃;

TA - Local minimum ambient temperature ℃;

λ - Thermal conductivity of insulation material, W/(m ℃), see Table 3;

D1- Inner diameter of insulation layer, (outer diameter of pipeline) m;

D0- outer diameter of insulation layer, m; D0=D1+2 δ;

δ - insulation layer thickness, m;

Ln - natural logarithm;

The heat dissipation coefficient of the outer surface of the insulation layer facing the atmosphere, W/(㎡℃), is related to the wind speed ω, (m/s), 

Calculate the alpha value according to formula (3):

α=1.163(6+ω1/2) W/( ㎡℃ ) …………………………(3)

8.2.3 Correction factor for pipeline material

The thermal conductivity of different materials varies, and the required power varies under the same TV conditions. The correction factor Kc is shown in Table 4;

The conditions for Q t and Q P values are steel, and any material changes should be multiplied by a material correction factor. For example, equation (4):

Table 3 Thermal conductivity of commonly used insulation materials

Thermal conductivity of insulation material W/(m ℃)

Glass fiber 0.036

Slag cotton 0.038

Calcium silicate 0.054

Expanded perlite 0.054

Vermiculite 0.084

Rock wool 0.043

Polyurethane 0.024

Polystyrene 0.031

Foam plastic 0.042

Asbestos 0.093

Table 4 Correction Factors for Pipeline Materials

Correction factor for pipeline materials

Carbon steel 1

Copper 0.9

Stainless steel 1.25

Plastic 1.5

Q=Qt×kc W/m ………………………………………(4)

8.3 Calculate the total length L of the required heat tracing cable

Use Q value to select the appropriate specification of heat tracing cable, and determine the length and laying method of the heat tracing cable used for each meter of pipeline.

8.3.1 Heat tracing cable length Lg for pipeline section

1) The length Lg of the heat tracing cable that should be laid per meter of pipeline is:

Lg=Q/QM m/m (5)

In the formula, QM is the output power (W/m) of a certain specification of heat tracing cable when maintaining temperature TV.

2) When Lg is less than 1, the heat tracing cable used for each meter of pipeline cannot be laid if it is less than 1m, so Lg cannot be less than 1.

3) When Lg is equal to 1, 1 meter of heat tracing cable of this specification is used for each meter of pipeline, laid in a single straight line.

4) When Lg is equal to n (n is an integer), n heat tracing cables of this specification are used per meter of pipeline, and n cables are laid in straight lines.

5) If Lg is greater than 1 and not equal to n, spiral winding can be used for laying, with a pitch of LS (m)

LS=π（D+d）/（Lg2-1）0.5 m ………………………(6)

D is the outer diameter of the pipeline (m); D is the thickness of the heating cable (m)

6) The length of the heat tracing cable used for the pipeline section is: 

L1=total length of pipeline x Lg m (7)

8.3.2 Length L2 of heat tracing cable for flat parts

1) The length of heat tracing cable to be laid per square meter of surface is:

Lp=（Qp×Kc）/ QM m/㎡

2) Lp ≥ 3 means that a heat tracing cable with a length of no less than 3 meters must be laid per square meter of area.

3) The length of the heat tracing cable used for the flat part is:

L2=S×Lp m…………………………………………………(8)

S is the area of the heat dissipation plane (m2). When the diameter of the pipe is greater than 600mm, it can be treated as a flat container.

8.3.3 Length of heat tracing cable for pipeline accessories

The heat loss of pipeline accessories can be converted into the heat loss of pipelines of the same length and diameter, and the required cables should be laid on the corresponding accessories.

The required length of heat tracing cable for pipeline accessories=accessory heat dissipation coefficient x required length of the same type of cable per meter of pipeline

1) The required cable length Lf for each valve is:

Lf=kf×Lg………………………………………………………（9)

In the formula, kf is the valve heat dissipation coefficient, as shown in Table 5

Table 5 Valve Heat Dissipation Coefficient

Valve type: Gate valve, Butterfly valve, Ball valve, Ball core valve

Heat dissipation coefficient 1.5 0.9 1.0 1.4

2) The required cable length Lj for each pipeline and other accessories is:

Lj=kj×Lg …………………………………………………（10)

In the formula, kj is the heat dissipation coefficient of other accessories, as shown in Table 6:

Table 6 Heat dissipation coefficient of pipeline accessories

Attachment project: Flange elbow straight joint T-shaped joint bracket hanger

Heat dissipation coefficient 2 2 2 3 3 3

8.3.4 Reserved length of joint L3

1) Reserve 1m for each power input terminal;

2) Leave 0.5m at each end;

3) Reserve 0.5m for each straight or T-shaped junction box;

4) Backup (as required by the project);

The total length L of the required heat tracing cable is (with a 30% increase in safety factor), L=(L1+L2+Lf+Lj+L3) × 1.3

8.4 Selection of heat tracing cables 

8.4.1 Select the corresponding heat tracing cable with the highest exposure temperature based on the maximum temperature that the pipeline may withstand

Determine whether there will be occasional temperature rise in the pipeline (such as steam, hot water, hot oil cleaning pipeline) and the maximum temperature. The maximum exposure temperature of the selected heating cable should not be lower than the occasional temperature rise.

If the accidental temperature rise is higher than the maximum exposure temperature, the installation method can be adjusted after thermal estimation, that is, a layer of insulation with appropriate thickness is added between the heat tracing cable and the pipeline to mitigate the impact of the accidental temperature rise on the cable.

8.4.2 Select the power of the heat tracing cable based on the power temperature curve

The selection of the output power of the heat tracing cable is not based on the nominal power, but on the power that the heat tracing cable must output when maintaining the temperature of the system.

The temperature level and heat tracing power of the selected cable are directly related to the required maintenance temperature of the system. The cable with the highest surface temperature higher than the system maintenance temperature (such as 20 ℃) and capable of compensating for system heat loss should be selected.

8.4.3 Determination of maximum length of single power supply heating cable

The sum of the lengths of all sections of heat tracing cables led from the same power junction box is called the maximum heat tracing cable length for a single power supply. Select the capacity of the overcurrent protection switch based on this. According to the distribution of pipelines and the length of branch lines, cables are selected. Low power cables have a longer length and are suitable for longer branch lines. If the power of one cable is not enough, multiple cables can be used.

8.4.4 Selection of Cable Structure

Structural selection based on installation environment and conditions

1) Shielding products can be used on containers and pipelines that are coated with paint on plastic or surfaces but cannot be reliably grounded.

2) In flammable and explosive areas, or when the medium inside the pipeline is flammable and explosive, shielded products should be selected.

3) If the medium inside the pipeline is corrosive, or if the cable may come into contact with chemicals that corrode the shielding layer, protective products should be used.

8.4.5 Other matters

1) The power connection section of the heat tracing cable should be larger than the conductor section of the heat tracing cable.

2) Fuses and air switches should be selected appropriately, taking into account a current greater than the starting current of the entire line.

3) Special power junction boxes, intermediate junction boxes, and terminals must be used in flammable and explosive areas.

4) Determine whether to use single-phase power supply or three-phase power supply and voltage level based on power capacity, voltage, and grid balance status.

5) Whether the surrounding environment of the pipeline is conducive to cable installation, and determine whether the heat tracing cable should be laid in a straight line or a spiral.

9 Electric Heat Tracing System Diagram 

9.1 Principles for drawing electric tracing system diagrams

1) Each electric heat tracing system powered by a single power source should have its own electric heat tracing system diagram drawn.

2) The electric tracing system diagram is based on the piping diagram of the traced pipeline and is represented by an axial projection diagram.

3) The electric tracing system diagram is a schematic diagram and may not be drawn to scale.

9.2 Requirements for Diagram of Electric Heat Tracing System

1) The electric tracing system diagram should list the pipeline number, diameter, material, insulation material, and insulation thickness;

2) The positions of valves, fittings, brackets, flanges on the pipeline and the length of the pipeline should be marked, and the position of the junction box should also be marked;

3) List the name, operating temperature, maintenance temperature, possible maximum temperature, minimum ambient temperature, temperature difference, and heat dissipation loss of the medium inside the pipe

Classification of lost and dangerous areas;

4) List the specifications, quantity, and heat generation of the heat tracing cable during temperature maintenance, as well as the quantity, specifications, and models of the electrical equipment

Other attachments.

Installation of 10 electric heat tracing facilities

10.1 Preparation before installation

1) All heat tracing cables must undergo circuit continuity and insulation performance tests, and those that do not comply with regulations cannot be used.

2) Electrical and control equipment must undergo visual inspection. If there is deformation, cracking, incomplete components that cannot be repaired, they cannot be used.

3) Before installation, the pipeline number, pipeline specifications, process conditions, and tracing cable parameters should be checked one by one according to the electric tracing system diagram

The specifications and models of electrical equipment and control equipment must be confirmed to be correct before installation can proceed.

4) Products without product markings, or with unclear markings that cannot be recognized, cannot be installed.

5) Before installing the electric heat tracing system, all the heat tracing pipelines must be constructed and checked for compliance through a water pressure test (or/and an air tightness test)

Ge.

10.2 Installation precautions

1) When installing the heat tracing cable, do not drag it on the ground to avoid being damaged by sharp objects. Do not come into contact with high-temperature objects to prevent welding

Slag splashes onto the heating cable.

2) The heat tracing cable has good flexibility, but it is not allowed to be bent hard. When bending is required, the bending radius should not be less than 6 times the thickness of the heat tracing cable.

3) It is strictly prohibited to hit the heating cable with heavy objects. If the heating cable is hit, it should undergo electrical testing again and can only be used after passing the test.

4) The heat tracing cable should be tightly attached and fixed to the heat tracing pipeline (or equipment) to improve the heat tracing efficiency. When fixing the heat tracing cable, use specialized

Use nylon zip ties and strictly prohibit tying with metal wires.

5) A layer of aluminum tape should be applied between the outer wall of non-metallic pipelines and the heat tracing cable to increase the contact heat transfer area.

Figure 3 Diagram of winding method for heat tracing cable on pipeline

1. Cable tie 2, pipe 3, cable tie 4, heat tracing cable

The maximum distance between two zip ties is 300mm

Figure 4 Winding method of heat tracing cable at flange Figure 5 Installation and fixation of heat tracing cable on pipeline 

1. Flange 2, Pipe 3, Tie 4, Heat Tracing Cable 1, Pipe 2, Insulation Layer 3, Outer Protective Layer 4, Tie 5, Heat Tracing Cable

6) The installation of heat tracing cables should fully consider the possibility of dismantling pipeline accessories (or equipment), and the heat tracing cables do not need to be cut off. Pay attention to the sealing of the joint when the cable is cut or spliced.

7) When the heat loss per meter of pipeline is greater than the output power per meter of heat tracing cable, the heat tracing cable can be laid according to Figure 4 for easy disassembly during maintenance.

8) The flange is prone to leakage, so when winding the heat tracing cable, it should be avoided directly below it, as shown in Figure 5.

9) The installation method and fixation of the heat tracing cable on the pipeline can be carried out according to Figure 6. The cable tie material should be selected according to the temperature of the pipeline.

10) After the installation of the heat tracing system is completed, it is necessary to conduct electrical tests on each circuit one by one before conducting a power on test to check the heat tracing cables

Fever situation. After confirming that everything is normal, insulation is allowed.

11) The insulation material should be dry. Damp insulation materials not only affect the heat tracing effect, but also lead to corrosion of the heat tracing cable, shortening its lifespan

The insulation pipeline without an outer protective layer should be dried before applying the outer protective layer after being wetted by rain and snow.

12) After the construction of the heat tracing system is completed, obvious electric heat tracing markings should be made on the outer protective layer of the pipeline to remind people to pay attention.

13) When installing the heat tracing cable, before connecting one end of the cable to the power supply, the other end of the busbar should be sealed with a matching head. The two busbars should not

It needs to be short circuited.

14) When multiple circuit heat tracing cables are connected from the same junction box, each busbar should be isolated with insulation sleeves to prevent short circuits.

15) The junction box should be sealed to prevent rainwater from entering. 

10.3 Typical installation diagram of heat tracing cable (see Figure 7-17) 

Figure 6 Schematic diagram of heat tracing cable assembly

Figure 7 Installation of heat tracing cable at three-way junction Figure 8 Installation of heat tracing cable on valve

1. Cable tie 2, heat tracing cable 3, pipeline 1, cable tie 2, heat tracing cable 3, pipeline 4, valve body

Pull out the heating cable and lay it on the outside of the elbow

Figure 9 Installation of heat tracing cable at elbow Figure 10 Installation of heat tracing cable at "U" - shaped pipe clamp

1. Cable tie 2, pipeline 3, heat tracing cable 1, cable tie 2, heat tracing cable 3, pipeline 4, U-shaped card 5, bracket

Figure 11 Installation of heat tracing cable at flat pipe support Figure 12 Installation of heat tracing cable at bent pipe support

1. Pipeline 2, heat tracing cable 3, zip ties 4, pipe support 1, pipeline 2, heat tracing cable 3, zip ties 4, pipe support

Figure 13 Installation of heat tracing cable at pipeline and support Figure 14 Installation of heat tracing cable at pipeline hanger

1. Cable tie 2, pipeline 3, bracket 4, heat tracing cable 1, hanger 2, sealant 3, waterproof cover 4, insulation layer

5. Pipeline 6, heat tracing cable 7, zip ties

Figure 15 Installation of heat tracing cable on pump Figure 16 Installation of heat tracing cable on liquid level controller

1. Motor 2, pump outlet 3, heat tracing cable 4, pump inlet 5, pump body 1, heat tracing cable 2, zip tie 3, tail end seal 4, junction box

10.4 On site testing and inspection of electric heat tracing system

1) The continuity and insulation resistance of the heat tracing cable shall be checked with a 500V megohmmeter. If the system insulation resistance is greater than 5M Ω, it is qualified.

2) After the installation of the heat tracing system is completed, the test results of each electric heat tracing circuit should be recorded and reported.

3) Inspectors should conduct intermediate inspections, final verification, and acceptance of the installation of the heat tracing system in accordance with engineering regulations, and may seek assistance from the cable factory if necessary.

Structural material of temperature controlled heating cable:

1. Core tape layer:

PTC core strip is a parallel circuit formed by uniformly extruding PTC material onto two parallel tinned copper wires.

The cross-section of the core strip can be dumbbell shaped or flat circular.

2. Insulation layer:

The insulation of the cable should be modified polyolefin and other insulation materials that meet the highest working temperature level of the cable. The insulation should be tightly extruded on the PTC core tape, and its surface should be smooth, flat, and uniform in color. The insulation should not adhere to the core tape. The insulation thickness is 0.6 mm ± 0.1 mm, and any point of the insulation thickness may be less than the specified value, but as long as it is not less than 90% -0.1 mm of the specified value. It should be checked whether it meets the requirements according to the test method specified in Article 8.1 of GB/T 2951.1. Cable samples should be taken at least 1 meter apart from each other at three locations. The insulated wire core should be able to withstand the AC 50Hz spark test specified in the GB/T 3048.9 power frequency spark test method for insulated wire cores of wires and cables. As an intermediate inspection, the spark test voltage value is 6kV.

Requirements for Physical Performance Testing of Insulation Machinery

Unit standard requirements for serial number test items

11.11.2 Mechanical properties before aging Tensile strength, minimum elongation at break, minimum MPa% 12.5200

22.12.2 Mechanical performance treatment conditions for air box aging: temperature duration, tensile strength change rate, maximum fracture elongation change rate, maximum ℃ d% 135 ± 37 ± 25 ± 25

33.13.2 Treatment conditions for thermal extension test: elongation under mechanical load for air temperature load time, permanent elongation after maximum cooling, maximum ℃ minMPa%% 200 ± 3150.217515

44.1 Water absorption test weight method treatment conditions: temperature time weight change rate, maximum ℃ dmg/cm2 85 ± 2141

55.1 Shrinkage test processing conditions: temperature time shrinkage change rate, maximum ℃ h% 135 ± 314

3. Cover layer:

The shielding layer of shielded cables should be woven with tin plated copper wire on the insulation layer. The maximum diameter of tinned copper wire for weaving is shown in the following table: 

Tin plated copper wire size

Maximum cable width for tinned copper wire

b≤10.0mm 0.16mm

10.0mm＜b≤20.0mm 0.21mm

The weaving coverage rate should be above 75%.

4. Sheath layer:

The cable sheath should be made of modified polyolefin and other sheath materials, and the sheath should be extruded in a single layer. When the heat tracing cable is of protective type, the sheath is extruded on the insulation layer or metal shielding layer. The sheath should be tightly extruded, and the surface of the sheath should be smooth, uniform in color, and easy to peel off without damaging the insulation and weaving layer. The thickness of the sheath is 0.75mm ± 0.1mm. Any point of the sheath thickness may be less than the specified value, but as long as it is not less than 85% -0.1mm of the specified value. The test method specified in Article 8.2 of GB/T 2951.1-1997 should be used to check whether it meets the requirements. Cable samples should be taken at least 1 meter apart from each other at three locations.

Requirements for Mechanical and Physical Performance Testing of Sheath

Unit standard requirements for serial number test items

11.11.2 Mechanical properties before aging Tensile strength, minimum elongation at break, minimum MPa% 12.5200

22.12.2 Mechanical performance treatment conditions for air box aging: temperature duration, tensile strength change rate, maximum fracture elongation change rate, maximum ℃ d% 135 ± 310 ± 25 ± 25

3 carbon black content, minimum% 2

4. Resistant to environmental stress cracking, minimum h 1000

55.15.2 Thermal extension test processing conditions: elongation under temperature mechanical load time load, maximum permanent elongation after cooling, maximum ℃ MPAmin%% 200 ± 50.21517515

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