Points To Be Considered In The Construction Of Hot Oil Installation
1.Thermal Oil expansion tank: must be at least 30% of the total thermal oil volume in the installation (including the boiler). The diameter of the expansion tank must be as small as possible (for the surface in contact with the atmosphere to be small), and the tank must be placed upright cylindrical.
2.Reserve oil tank: must be at least 1.5 times the volume of all thermal oil in the installation.
3.Thermal oil circulation pumps: specially designed for high temperatures, preferably air-cooled, steel casting or ductile iron.
4.Thermal Oil filling pumps : gear pumps can be used designed according to the viscosity of thermal oil at room temperature.
5.Valves, check valves, 3-way valves : thermal oil must be resistant to operating temperature and copper or copper alloys should not be used in its internal parts. Valves must be PN16 ductile iron or PN25 / 40 steel casting.
6.Filters: they keep solids carried with oil in the installation. They need to be cleaned from time to time. Selecting filter surfaces as large as possible is appropriate in terms of reducing the frequency of cleaning. A manometer must be attached to the input and output of the filter in order to be able to see and interfere with the resistance that will occur with the contamination of the filter.
7.Thermal Oil level indicator: the temperature and characteristics of thermal oil in the expansion tank must be appropriate.
8.Piping and fittings: all fittings must be steel. Unalloyed Steels under 300 C are permitted to be used. Carbonaceous in piping (e.g. ASTM a-53 and ASTM a-106) or St. 35.8 seamless steel pull pipe can be used. Cast iron is never used in hot oil installations. (Due to the danger of breaking, cracking, oil leakage) the pipe installation should be properly inclined and an air drain pipe and Valve should be placed where there is a possibility of Air collection. The pipes that are cycled by the oil must be isolated with sufficient thickness with the stone wool.
9.Instruments: the following instruments must be present in the hot oil system for safety and control.
a. Burner control thermostat
b.Maximum temperature thermostat
c.The differential presostad or flow control automatic (flow switch) stops the burner when the oil circulation slows or the oil circulation pump turns off.
d.The expansion tank minimum oil level lock deactivates the burner by alerting it when the oil level falls below a certain level.
e.Flue thermostat: when oil circulation stops for any reason: because the flue gas temperature rises, it turns off the burner.
10.Thermal Oil to be used in the system : mineral oils made from Mineral oils, which do not lose their properties at high temperatures, do not have corrosive properties, thermal stability (heat bearing properties) should be preferred.
11.Expansion tank: the only place in the system where thermal oil comes into contact with air. In order to avoid oxidation, the temperature of the oil in the tank must not exceed 60 C. The facility should be made to guarantee this condition. In order to reduce the surface of the oil in the tank in contact with the air, the expansion tank should be manufactured in the form of an upright cylindrical tank and mounted at a higher point than the top of the installation so as not to cause problems in pressing the circulation pump out of the building. Expansion tank should not be isolated. (however, in places in danger of frost can be enclosed in a Mahal.) The connection of the installation with the expansion tank is provided before the suction of the circulation pump and with 1 1/2" - 2 " diameter non-insulated pipe.
12.Thermal Oil Storage Reserve Tank: place the reserve tank at a depth where all the oil in the installation will be drained by natural flow. If possible, put a level indicator or petrometer on it. Start filling the oil in the system with a hand pump or gear pump from the bottom point. Ensure that they are turned on during the oil refilling process by installing an air drain system where there is a possibility of holding air in the system.
13.Pipe prolongation: due to high temperatures, expansion of pipes in hot oil installation should be taken into consideration. These elongations in the connections of installation elements such as boiler, valve gain even more importance. The elasticity of small diameter pipes can sometimes compensate for these elongations. However, if there is too much armature on large diameter pipes and feature pipeline, the compensator should be used at certain intervals and the pipes should be fixed from the appropriate places.
14.Air Evacuation System: precautions must be taken to evacuate the Steam and gas collected at the top points of the system.
15.Bluffing: to empty all oil and other materials in the installation should be installed in a suitable place.
16.Hot oil boiler rooms: separate from the main building, must have been independent and made to the floor. It must have an emergency exit door (made of fire resistant material) other than the entrance door.
17.Ventilation: The Boiler Room should have a lower air intake and an upper dirty air outlet that will allow more air circulation than incineration air.
Hot Oil Installation Commissioning Procedure
1.Pressure test: the hot oil boiler and all installation should be subjected to pressure test with thermal oil or air at least 6 bar pressure. If the pressure test is conducted with air, the air must be completely drained at the end of the test process.
2.Thermal Oil Filling: to prevent air retention in the installation, the system is started to press thermal oil through the filling pump (gear pump) from the lowest point of the installation. In the meantime, air relief valves are open. The valves are closed when the air discharge from these areas is finished and the oil starts to come in. Up to 1/3 of the thermal oil expansion tank (minimum level) is filled. Circulation pump oil is operated in cold condition for 4 hours and the discharge of possible air in sentemde is provided.
3.Commissioning: the temperature rise rate is raised to 40 C / hour until the thermal oil temperature rises to 90 C. Temperature rise between 90 C and 120 C should not exceed 10-15 C/hour. After that, the system is run for 6 hours at normal operating temperature. The system is cooled. The foreign substances accumulated in the filters are cleaned.
4.Thermal Oil test: periodically check the oil in the system by taking samples as follows. If it has reached the point of replacement, replace the thermal oil.
a.The first test is conducted after the first run.
b.The second check should be done at the end of 100 working hours or the second month.
c.The third and fourth checks must be checked after 2000 working hours or every 6 months.
d.All subsequent checks should be carried out regularly every 3000 working hours or every year.
5.How to test thermal oil: oil intake should not be less than 1 kg in a transparent container and when the system is cold. When the system is cold, the circulation pump is operated and stopped for 10-15 minutes and the sample is taken after pouring some oil from the sampling valve on the return line. In the first Test (after the first run) the thermal oil inside the sample container is checked to see if it is clean. If contamination is detected, the oil in the system is drained and filtered and filled again. In the test of the oil in the system, contamination, oxidayon and deterioration signs are sought.
6.Signs Of Deterioration Of Thermal Oil
a.Contamination: the residues in the thermal oil from the installation sample reduce the thermal stability, heat carrying capacity and heat transfer capability of the oil. In addition, foreign objects such as welding Burr can cause damage to plumbing elements such as circulation pumps and valves.
b.Oxidation: when the thermal oil temperature exceeds 60 C, it undergoes oxidation if it comes into contact with the air. Its viscosity increases. Reduced fluidity and heat transfer capacity.
c.Thermal degradation: when the Thermal Oil overheats in the boiler and its temperature exceeds 350-400 C (the general reason for this is that the oil speed may stop or slow down too much in the boiler) it starts to deteriorate. (Cracking). It is seen in black spots (pitchization) in the first part of the Bo oil. This distortion can cause the fluid to thicken, decrease the flowability, increase the resistance in the oil circuit in the system, prevent heat transfer by plastering on the boiler heating surfaces at a higher level and cause heat accumulation and fire as a result of punctures. Excess contaminated and thermal degradation thermal oil must be replaced immediately.