THERMOCOUPLES GENERAL DESIGN AND SELECTION THERMOCOUPLE STANDARD

Transcription

1 THERMOCOUPLES GENERAL Straight Thermocouples Straight thermocouple with metal and ceramic protecting tubes are widely used in a variety of processes between 200 C and 2320 C The maximum operating temperatures given in the catalogue apply to the air where there are no corrosive gases. L-type of Thermocouples L-type thermocouples are usually used in temperature measurement of salt baths and metal melts. The reason for using of angled type thermocouples is to protect the head from the heart and the corrosive gases on the bath. Inset Type Thermocouples Inset type of thermoucouples are inserted to the secondary protecting tubes to have longer life-time in process applications. Inset consist of an inset tube stem or alternatively of mineral isolated thermocouples terminated with a ceramic terminal block connected to a metal flange. Portable type Thermocouples Portable type thermocouples have a comprehensive range of applications. Portable type thermocouples can be used in measuring the temperatures of both ambient and surfaces. Exhaust Thermocouples Exhaust thermocouples have special mounting forms in accordance with the characteristics of process. Generally they are mounted with fixed cables. Bayonet Type Thermocouples These thermocouples are mounted with fixed cables and secured with spring compression to their location of installation. The bayonet type thermocouples can not used for liquids or humid conditions. Mineral Insulated Thermocouples Mineral Insulated Thermocouples can be used in various processes at different temperatures such as; in containers, pipelines, apparatus and machinery, also in laboratories and experimental plant in gaseous and liquid media such as air, gases, water, oil, etc. in low-pressure areas, at low rates of flow Thermowells In general the thermowells chosen for the installation is governed mainly by the corrosion conditions the well will face. The high polish given to all stainless wells provides maximum corrosion resistance. Occasionally, the material consideration is one of the strength rather than corrosion resistance. When ordering flanged thermowells, be sure to specify the flange fully. Use a sketch or drawing of both flange and well for ordering stage. DESIGN AND SELECTION In order to increase the life-span of thermocouples the materials for the thermocouple, element wire insulator, protecting tube and connection head must be selected according to operating conditions. The maximum operating temperatures given in the catalogue apply to the conditions where operating medium is air. Although the exceeding of the maximum temperature limits specified for short periods do not effect the results, they will reduce the life of the thermocouples corrosive substances in the process also causes the upper temperature limit to be lower for the protecting tube. THERMOCOUPLE STANDARD EMF characteristics of the thermocouples meeting DIN and IEC 584 are given in Thermocouples Supplementary Notes section concerning thermocouples. According to the customer requirements, Elimko can manufacture thermocouples in other standards or special types. 65

2 PROTECTING TUBES Protecting tubes must be selected in accordance with the conditions of the process. As a rule, metal protecting tubes are used up to 1200 C and ceramic tubes are used over 1200 C. In order to prevent the thermocouples element wire from being effected by corrosive gases and increase the life span of the thermocouple, a second ceramic protecting tube is placed inside. Ceramic protecting tubes being used as gas-tight have below given specifications; KER 610 Better gas-tight characteristics High heat resistance High aluminium oxide percentage More economical than KER 799 KER 799 Much better gas-tight characteristics Maximum heat resistance Pure aluminium oxyde pers entage Better and more expensive than KER 610 In L-type thermocouples protecting tubes are connected to the body in two ways. Si-Cr and Si-Ni type of ceramics are connected in TC06 drawing code and the others are in TC07 drawing code. Since the mineral insulated thermocouples have a special structure, they do not have the opportunity to be used with various cases with different alternatives like other thermocouples. The protecting tubes of mineral insulated thermocouples can be inconel or 316 stainless steel. Elimko standards are usually inconel and are used up to 1200 C. Thermocouples could be welded with or without grounded at the end point. It is required to give the details at ordering stage. CONNECTION HEADS Element wires and compensation cables are connected in right polarities to the ceramic terminal in connection head which the thermocouple tubes are fastened A-type large and B-type small heads in standards are used. Connection heads are available having dimensions according to DIN Metal heads are suitable for a maximum ambient temperature of 200 C. MOUNTING METHOD The thermocouples given in detail in this catalogue are generally considered to be connected by means of an adjustable flange or adjustable bushing. These mounting parts can be supplied when customers specify exact needs. INSTALLATION INSTRUCTIONS It is recommended to use the maximum immersion length of thermocouple assembly, thus keeping measuring errors caused by heat transfer along the protecting tube and wires to a minimum. In order to prevent the long tubes from bending, it is advisable to mount them upright position or to prodvide for appropriate support. A compensating cable should be used between the thermocouple head and the instrument. Please be sure that a proper compensating cable is selected and the connection is made properly. In order to get accurate measurement, insertion length of the thermocouple should be not less than 10 times of the external diameter. For the L-type thermocouples, the head of the thermocouple should be away from the corrosive gases over the bath level. For mineral insulated thermocouples insertion length of the thermocouple can be 5 times of its external diameter in case of liquids, and 20 times of its external diameter in case of gases. Minimum bending-radius changes according to the diameter of the mineral insulated thermocouples. STANDARD TYPES The standard types ordered by the customers are delivered in short periods and at reasonable prices provided that the priority is given to the competition factors. To chose the standard type of thermocouples are easy by using code list and can be delivered from stock. SPECIAL TYPES Special types according to the application can be ordered by giving the answers of the questions below. a. Application b. Continuous and maximum operating temperatures c. Technical drawings with size, diameter, and other details d. Product code number, if ordered previously e. Pressure and flow data if known f. Chemical corrosion factors Please try to fill in the questionary form of thermocouples in supplementary notes. SPARE PARTS All kinds of spare parts for thermocouples can be ordered by using the selection table in the catalogue. According to the stock level, the spare parts may be delivered from stock or within a certain delivery period. REPAIR Repair of the thermocouples is not economical if almost all the elements are defective. As stated in the thermocouple spares section, only when either the tube or the element wire is working the other component can be repaired using spare parts. HOW TO ORDER a. Standard types Standard types are coded by using drawing number and 7 different groups of alphanumeric characters b. Special Types Special features are defined in the 7th digit or by additional information added to the end of the 7th digit. Fully special types are subjected to a different coding. Example TC01-1K 2 N 22-50PY Drawing nr TC01 With single element NiCr-Ni Element wire dia 2mm Seconder protection Seconder protection 22 mm Immersion length 500 mm Gas-tight KER

3 EL MKO STRAIGHT THERMOCOUPLE CODING Drawing number 1 Number of elements (single-double) 2 Type of element 3 Diameter of element wire 4 Protecting tube 5 Diameter of protecting tube 6 Immersion length 7 Special features TC01-1 K 2 N PY Drawing nr Drawing nr.tc01 TC02 TC03 TC04 TC05 TC06 TC07 TC07-A TC08 TC09 TC10 TC11 TC12 TC013 TC14 TC15 TC16 1- Single element Double element (1) (2) 2- Type of element EL MKO CODE STANDARD CODE U Cu-Const U* L Fe-Const L* T Cu-Const T J Fe-Const J K NiCr-Ni K E Cr-Const E N Nikrosil-Nisil N S Pt%10Rh-Pt S R Pt%13Rh-Pt R B Pt%18Rh-Pt B 3- Diameter of the element wire 1) 1 mm 2) 2 mm 3) 3 mm 4) 0.35 mm 5) 0.5 mm 6) 1.38 mm 7) 1.5 mm 8) 6.0 mm M/I 9) 4.5 mm M/I 10) 1.5 mm M/I 11) 8.0 mm M/I special 4- Protecting tube A Al-25 P (304) M X 530 N Y 610 O Z 799 B Brass C C-2 D St-35.8 F Pure Iron G Graphite I Inconel E (316) H (316L) J (321) K (316TI) L L R Refrax S Si-Cr T Titanium Q Quartz Thermocouples are coded with different drawing numbers. 1 or 2 comes in the 1.digit in a accordance with the number of the elements of thermocouple In 2. digit, corresponding letter represents the type of the element *According to DIN standards the others are IEC 584 In 3. digit diameter of the element wire is given. It refers to the temperature which thermocouple works. In general, the diameters of 0.35mm and 0.35mm and 0.5mm are for PtRh-Pt elements In 4. digits, the material of the protecting tube is given by selecting in accordance with the process. Please reference to the Thermocouple selection table for an appropriate selection 5- Diameter of the element wire 6- Thermocouple length (immersion length) Note: These dimensions are in mm Note: These dimensions are in cm Only inset heights are in mm In 5. digit, the diameter of the protecting tube is given. The diameter is selected by considering different factors. The diameters given here are standard dimensions. Note: 5. digit has two digits. In 6.digit, the immersion length is given. In order to ensure an account measurement, immersion length of the thermocouples should be at least 6 or 10 times of the protecting tube diameter. Note: 6. digit has two digits. 7- Special Features P Primary PY Primer KER 610 R Mounting Bush PZ Primer KER 799 F Flange EX Exproof head I Insulator Tr Transmitter O Special S Socket S 1 S 2 S 3 In 7.digit the corresponding character is given. These letters present such as primary protecting tube, coupling, flange etc. For special conditions in addition to standards "O" letter is printed. 67

4 EL MKO STRAIGHT THERMOCOUPLE ASSEMBLIES TC01 TC02 TC03 TC04 TC05 TC30 EL MKO L-TYPE THERMOCOUPLE CODING In determining codes for L-type thermocouple, straight-type thermocouple coding list is used. Drawing number of L-type thermocouple can be TC06 or TC07. As seen in the drawing below L1 is the insertion length. In standard types, when L1 is determined, L2 is determined automatically. Special requirements should be specified additionally. L1 versus L2 lengths are given in the table. Drawing nr. TC06 TC07 L 1 length chosen in the code L 1 = 31 cm L 1 = 51 cm L 1 = 71 cm L 1 = 30 cm L 1 = 50 cm L 1 = 71 cm standard L 2 versus L 1 L 2 = 33 cm L 2 = 50 cm L 2 = 50 cm L 2 = 33 cm L 2 = 50 cm L 2 = 57 cm L 1 xl 2 ( mm) L 1 xl 2 = 310x330 mm L 1 xl 2 = 510x500 mm L 1 xl 2 = 710x500 mm L 1 xl 2 = 300x330 mm L 1 xl 2 = 500x500 mm L 1 xl 3 = 710x570 mm L 3 (mm) 460 mm 660 mm 860 mm EL MKO L-TYPE THERMOCOUPLE ASSEMBLIES TC07-A TC06 TC07 68

5 EL MKO PORTABLE TYPE THERMOCOUPLE CODING In determining codes, for portable type of thermocouple straight-type thermocouple coding list is used. Drawing number of portable type of thermocouples can be chosen below given assembles according to the application. EL MKO PORTABLE TYPE THERMOCOUPLE ASSEMBLIES TC08 TC09 TC10 TC10-1 TC10-Y TC10-YA TC10-YU TC10-YD TC10-I TC10-HD TC10-H TC14 TC15 TC15-K TC16 TC17 69

6 EL MKO EXHAUST AND OTHER TYPE T/C CODING These types of thermocouples are coded with special figures. Standard code list may be used as well. After the drawing number is written, other numbers and letters may be drawn from the coding list of straight type thermocouples. EL MKO EXHAUST AND OTHER TYPE T/C ASSEMBLIES TC11 TC12-1 TC12-2 TC12-11 / TC12-21 TC13 TC20 EL MKO INSET THERMOCOUPLES Insets can be used for installation into assemblies of different design. They can be exchanged easily during operation the insets described in this catalogue can be used for installation in to TC03 and TC04 types. In determining codes for insets, straight-type thermocouple coding list is used. Drawing number of inset is TC05. Only exception is the inset length is given in mm instead of cm. Example: TC05-1K1P Length is in mm only for insets EL MKO INSETS AND THERMOCOUPLES WITH INSETS ASSEMBLIES TC03 TC04 TC05 70

7 EL MKO BAYONET TYPE THERMOCOUPLE CODING The bayonet thermocouples are coded as follows: Drawing number 1 Number of elements (single-double) 2 Type of element 3 Diameter of protecting tube 4 Immersion length 5 Cable Length BT01-1 J 06-3 K10 Drawing nr Drawing nr.bt01, BT02, BT03, BT04, BT05, BT06 Bayonets are coded with different numbers 1- Single element Double element (1) (2) 1 or 2 comes in the 1.digit in a accordance with the number of the elements of thermocouple 2- Type of element EL MKO CODE STANDARD CODE U Cu-Const U* L Fe-Const L* T Cu-Const T J Fe-Const J K NiCr-Ni K 3- Diameter of the protecting tube 04 (in mm) Bayonet length 2 (in cm) Cable length K10 1 m K m K20 2 m K m K30 3 m. In 2. digit, corresponding letter represents the type of the element *According to DIN standards the others are IEC 584 In 3. digit the diameter of the protecting tube is given. Generally protecting tubes used are brass or stainless steel. Note: The third digit has two digits. In 4. digit the immersion length is given. Standard length is 30 mm. In 5. digit the cable length is given as K10, K15. K10 means a cable length of 1 meter, K25 means 1.5 meters EL MKO BAYONET TYPE THERMOCOUPLE ASSEMBLIES BT01 BT02 BT03 71

8 BT04 BT06 BT05 EL MKO MINERAL INSULATED THERMOCOUPLE CODING The mineral insulated thermocouples are coded as follows: Drawing number 1 Number of elements (single-double) 2 Type of element 3 Diameter of protecting tube 4 Immersion length 5 Special Features MI01-1 J F Drawing nr Drawing nr. 1- Single element Double element MI01, MI02, MI03, MI04, MI05, MI06, MI07, MI08 (1) (2) Mineral insulated thermocouples are coded with different numbers 1 or 2 comes in 1. digit in accordance with the number of elements of thermocouple 2- Type of element EL MKO CODE STANDARD CODE L Fe-Const L DIN J Fe-Const J IEC 584 K NiCr-Ni K IEC 584 In 2. digit, corresponding letter represents the type of the element 3- Protecting tube diameter mm 30 3 mm mm 60 6 mm In 3. digit the diameter of protecting tube is given. Note: The third digit has two digits. 4- Thermocouple length 16 (in cm) Note: Only inset lengths are in mm. 5- Special features R Mounting Bush F Flange O Special Tr Transmitters ME Miniature Socket (Male) SE Standart Socket (Female) MD Miniature Socket (Male) SD Standard Socket (Female) In 4. digit the immersion length is given. In order to ensure an accurate measurement, immersion length of the thermocouples should be at least 5 times for liquids, at least 20 times for gases. Note: 4. digit has two digits. In 5. digit the corresponding character is given. These letters present such as mounting bush, flanges, sockets, etc. for special types, in addition to standarts "O" letter is printed. 72

9 EL MKO MINERAL INSULATED THERMOCOUPLE ASSEMBLIES MI01 MI02 MI03 MI04 MI05 MI06 MI07 MI07-I MI07-Y MI07-YA MI07-I MI07-H MI07-HD The mineral insulated Thermocouples have certain diameters on the standards. The minimum diameters that these thermocouples can be bended are limited. If bending curve exceeds these dia meters, the thermocouple is damaged. It can be broken. Because of this reason, attention should be paid when bending the mineral insulated thermocouples. The limits are given a table. MI08 Fe-Const or NiCr-Ni Outer Diameter Minimum Bending Approximate Diameter Element wire diameter 1.5 mm 8 mm 0.18 mm 3.0 mm 15 mm 0.45 mm 4.5 mm 23 mm 0.7 mm 6.0 mm 30 mm 1 mm 8.0 mm 36 mm 1.2 mm 73