Before construction, a complete design drawing should be prepared, which should include the following information:
Line number: indicated by a rectangular box at the power supply point;
The required heat tracing cable and length for the line, and the model of the heat tracing cable;
The required length of heat tracing cable per meter of pipe length; if the number is greater than the former, it indicates spiral winding;
The required length of heat tracing cable for each valve;
Remarks;
List of supporting materials and accessories for the heat tracing system;
List of accessories for the temperature control system;
List of materials required during construction;
Design parameters and specifications of the insulation materials used.
Preparation Work
(A) Piping system:1. The piping system and fittings have been installed;
2. The anti-rust and anti-corrosion coating is completely dry;
3. The construction and specifications of the piping system are consistent with the design drawing;
4. Remove all burrs and sharp edges.
(B) Heat tracing cable and accessories:
1. Check if the surface of the heat tracing cable is damaged;
2. The insulation performance of the heat tracing cable is good (insulation resistance should be 20 megohms when tested with a megger at 1000 VDC);
3. The models of the heat tracing cable and all accessories are consistent with the design requirements.
(C) Site preparation
Place a roll of heat tracing cable on a stand and position it near one end of the line.
Lay the heat tracing cable along the pipe and avoid the following:
* Placing the heat tracing cable on burrs and sharp edges;
* Pulling the heat tracing cable forcefully;
* Stepping on or placing heavy objects on the heat tracing cable.
Single Cable Installation Method
1. Use fiberglass heating tape (high-temperature resistant heating tape) to fix the heating tape to the pipe at intervals of approximately 50 cm;
2. Attach the heat tracing cable to the lower half of the pipe as much as possible;
3. Reserve 50 cm of heat tracing cable at each power supply point and the end of the line;
4. Lay the cable according to the "winding factor" shown in the design drawing;
5. For all heat sinks (such as supports, valves, flanges, etc.), reserve the required length of heat tracing cable as per the design drawing, wrap this section around the heat sink and secure it. Pay attention to the following points:
* The heat sink should have the required length of heat tracing cable as per the design;
* Heat tracing cables can overlap each other;
* The winding method should allow the heat sink to be removed for maintenance or replacement without damaging the heat tracing cable or affecting other lines;
* At locations where two-way or three-way fittings are used, reserve 40 cm of heat tracing cable at each end.
Spiral Winding
For example, if the winding factor is 1.4, it means that 5 meters of pipe requires 7 meters of heat tracing cable. During construction, first fix both ends of a 7-meter section of heat tracing cable to a 5-meter length of pipe, then wind the slack cable around the pipe and secure it.
Accessory Installation
* Select accessories according to the design drawing;
* The sealing gasket used must match the heat tracing cable;
* The power junction box should be as close as possible to the power supply end of the pipe line;
* Prepare the cable ends and install according to the accessory installation instructions;
* Reserve a short section of heating cable at each end for future maintenance.
Inspection and Testing
Immediately after the installation of the heat tracing cable, perform the following inspections and tests:* Inspect the surface of the heat tracing cable for damage;
* Inspect all accessories for complete installation;
* Use a megger at 2500 VDC to test one end of the line; the insulation resistance should be above 20 megohms. Note that the test time should be at least one minute, and test the power supply cable against the metal shield;
* Record the test results on the installation record sheet.
Insulation Layer Installation
After the electric heat tracing cable construction test, immediately install the insulation layer, and pay attention to the following points:* The material, thickness, and specifications of the insulation layer should comply with the design drawing;
* The pipe and insulation material must be dry during construction;
* A waterproof outer cover should be added outside the insulation layer;
* Avoid damaging the heat tracing cable during insulation layer installation;
* Immediately after insulation installation, perform an insulation test on the electric heat tracing cable;
* Attach a label on the outside of the insulation layer indicating "Electric heat tracing system inside", and also mark the locations of all accessories;
* For pipes with an outer diameter less than 100 mm, the inner diameter of the insulation layer should be increased by 13 mm.
Temperature Control System Installation
(A) Ambient temperature thermostat:* Use an appropriate thermostat according to the design requirements, and it should meet waterproof and explosion-proof ratings;
* Supply power according to the required voltage;
* Install the thermostat in the coldest and most windy location as much as possible.
(B) Pipe-sensing thermostat:
* Use an appropriate thermostat according to the design requirements, and it should meet waterproof and explosion-proof ratings;
* Supply power according to the required voltage;
* The sensor should be in close contact with the pipe and away from the heat tracing cable, and at least 1 meter away from any heat sink;
* Install the sensor in a relatively hidden place to avoid damage;
* Adjust the thermostat appropriately.
Final Testing
* Inspect all pipes, insulation layers, and accessories to ensure no issues.* Turn off all circuit breakers for the lines.
* Use a megger to test each line once.
(A) For systems controlled by ambient temperature thermostats:
* Set the thermostat to the power supply state;
* Supply power to the line for 4 hours to allow the pipe temperature to reach a steady state;
* Measure the voltage, current, ambient temperature, and pipe temperature for each line, and record the data on the installation record sheet;
* After testing, set the thermostat back to the required setting.
(B) For systems controlled by pipe-sensing thermostats:
* Fine-tune the thermostat to the power supply state;
* Supply power to the line until it reaches the temperature set on the thermostat.
Test the backup system as above, but test only one system at a time.
