PT100尺寸說明

1、authorization for this document is on file in the geo standards department. all information herein is the confidential property of air products and chemicals, inc., unless another source is shown. this information is subject to return on demand and must not be disclosed or reproduced without prior w

2、ritten consent.air products and chemicals, inc., 2007global engineering guidelineguideline for selecting and specifying temperature elements3ps15001revision 3 22 february 2007page 1 of 32responsible group: process controls current contact: david c. arnerdenotes revision table of contents section tit

3、le page 1. purpose 2 2. scope 2 3. related documents 2 4. definitions 3 5. temperature elements 4 table 1 relative merits of rtds and thermocouples 5 table 2 thermocouple types 6 table 3 thermocouple accuracy 8 table 4 thermocouple cables 9 table 5 recommended default u dimensions for welded and thr

4、eaded applications outside cold boxes 26 figure 1 rtd wiring options 11 figure 2typical terminal arrangement 15 figure 3thermowell styles (threaded well) 16 figure 4threaded well and threadolet 18 figure 5threaded well and threaded elbowlet 18 figure 6dn20 socket weld installation 19 figure 7dn20 so

5、cket weld elbow installation 20 figure 8flanged thermowell installation 21 figure 9a threadolet installation dimensions 23 figure 9b weldolet installation dimensions 23 figure 10elbow installation nominal dimensions 24 figure 11flanged thermowell installation 25 figure 12thermowell extensions 27 app

6、endix a fast response thermocouples for reciprocating o2 compressors 31 3ps15001, rev. 3, page 2 of 32 all information herein is the confidential property of air products and chemicals, inc., unless another source is shown. this information is subject to return on demand and must not be disclosed or

7、 reproduced without prior written consent.air products and chemicals, inc., 20071. purpose1.1 this global engineering guideline provides background information and recommendations for the selection and specification of temperature elements. 1.2this guideline is intended to encourage consistent and u

8、niform good practice while meeting performance and reliability requirements. 2. scope2.1 this guideline applies to temperature elements for both air products-owned and -operated plants and for plants supplied to third parties. 2.2this guideline considers both rtd and thermocouple types of temperatur

9、e elements. other temperature measurement methods (e.g., thermisters, optical) are excluded. 2.2.1this guideline specifically does not include details of very low temperature applications (liquid hydrogen and liquid helium applications) for which silicon diode type temperature elements have typicall

10、y been specified. 2.3this guideline has been prepared specifically considering the requirements of: air separation plants hyco plants chemicals the general principles described within this guideline may be applied to other plant types with caution. additional considerations may apply to other types

11、of plants (e.g., ultra high purity plants). 2.3.1 this guideline is not intended for laboratory scale or other special applications. 2.3.2 interested parties are invited to make proposals to broaden the scope of this document to cover other processes at a future issue. 2.4 this guideline makes refer

12、ence to existing tier 4 specifications, and provides some supporting background information for these specifications.3. related documents3.1 air products engineering documents 3ma27036 mechanical requirements for distillation by temperature control for packed and trayed columns. 3ps00007 selection a

13、nd installation of transmitters 3ps00016 material selection for control valves and instrumentation in oxygen service 3ps15002 use of thermowells in pressurized systems 3ps45004 oxygen compressor temperature protection system 4wps-temp01 temperature sensors and thermowells for cold box service 4wps-t

14、emp02 resistance type temperature detectors (rtds) for cryogenic and general service 4wps-temp03 temperature sensors and thermowells for oxygen compressors - fast response type 4wps-temp04 temperature sensors for tray-type columns 4wps-temp05 temperature sensors for surface type measurements 4wps-te

15、mp06 temperature sensors and thermowells for general service 4ece-m25 cold box/can temperature element installation apg air products ped committee guidelines (intranet) provided for background information only (not referenced in the text) to be published at a date subsequent to this issue date 3ps15

16、001, rev. 3, page 3 of 32 all information herein is the confidential property of air products and chemicals, inc., unless another source is shown. this information is subject to return on demand and must not be disclosed or reproduced without prior written consent.air products and chemicals, inc., 2

17、0073.2 american society for testing and materials (astm) e 230 standard specification and temperature-electromotive force (emf) tables for standardized thermocouples e 608/e 608m standard specification for mineral-insulated, metal-sheathed base-metal thermocouples e 1137 standard specification for i

18、ndustrial platinum resistance thermometers 3.3 instrumentation, systems, and automation society (isa) mc96.1 temperature measurement thermocouples 3.3 international electrotechnical commission (iec) iec 60584-1 thermocouples. part 1: reference tables iec 60584-2 thermocouples. part 2: tolerances iec

19、 60751 industrial platinum resistance thermometer sensors 3.4 british standards (bs) bs en 60584-1 thermocouples. part 1: reference tables bs en 60584-2 thermocouples. part 2: tolerances bs en 60751 industrial platinum resistance thermometer sensors 3.5 german standards (din) din en 60584-1 thermoco

20、uples. part 1: reference tables din en 60584-2 thermocouples. part 2: tolerances 3.6 national institute of standards and technology (nist) its-90 international temperature scale of 19904. definitions4.1 rtd means resistance temperature detector (i.e., the actual sensing element in a prt). operation

21、is based on the principle of resistance thermometry, i.e., when a metals ele ctrical resistance increases with increasing temperature. metals that have shown a relative linearity and rangability for use in temperature measurement are platinum and nickel. 4.2 prt means platinum resistance thermometer

22、 (the whole assembly), i.e., a prt uses a rtd. 4.3 thermocouple operation is based on the seebeck effect whereby a voltage is created along a metal wire in the presence of a temperature gradient. a thermocouple uses a pair of dissimilar metal wires joined at two points such that a net emf is generat

23、ed when the junctions are at different temperatures. standard combinations of dissimilar metals suitable for a range of applications are given thermocouple type designators. see table 2 for thermocouple types currently used by air products. 4.4 electromotive force (emf) the term emf is used througho

24、ut this document to describe the voltages that are generated due to temperature gradients in thermocouple installation.4.5 cold junction compensation the net emf generated by a thermocouple installation depends on the temperatures both at the measuring thermocouple junction (hot junction), and at th

25、e reference junction (cold junction) i.e., the junction between the thermocouple cable (or compensating cable) and the copper cables or terminals of the associated transmitter/control system. cold junction compensation is the process of compensating for errors that would otherwise be introduced by c

26、hanges in temperature at the reference junction. historically, these errors were eliminated by immersing the reference junction in an isothermal environment (e.g., melting ice). in contemporary industrial systems, the thermocouple cable (or compensating cable) 3ps15001, rev. 3, page 4 of 32 all info

27、rmation herein is the confidential property of air products and chemicals, inc., unless another source is shown. this information is subject to return on demand and must not be disclosed or reproduced without prior written consent.air products and chemicals, inc., 2007is connected directly to the as

28、sociated transmitter/control system. the transmitter/control system compensates electronically for the actual temperature at the reference junction (i.e., at the transmitter/control systems terminals). 4.6the following dimensional definitions are used in this document: id dimension is the pipe inter

29、nal diameter (which depends on pipe nominal bore size and wall thickness or schedule). for example, see figure 9a. l lagging extension length. see figure 12 and paragraph 5.6.21.1. n nipple extension length. see figure 12 and paragraph 5.6.21.1. od dimension is the pipe external diameter (which depe

30、nds on pipe nominal bore size only). for example, see figure 9a. s dimension is the setback from the pipe wall od to the bottom of the fitting engagement. see figure 14 for an example. t thermowell extension length. see figure 12 and paragraph 5.6.21.1. th dimension is the pipe wall thickness. u dim

31、ension is the insertion length of the thermowell well measured from the tip of the well to the: bottom of the thread for threaded wells bottom of the weld section for welded wells bottom of the flange for flanged wells caution : there is some variability in the letter codes used for dimensions both

32、in other air products standards and in industry. care should be taken to clarify terminology when referring to dimensions by letter. 5. temperature elements5.1 standards for temperature elements 5.1.1section 3, above, illustrates that there are many national and international standards for temperatu

33、re elements. 5.1.2air products view is not to fa vor one standard over another (e.g., astm over iec). consequently, temperature elements may be specified in accordance with any internationally recognized standard. 5.1.3the european and iec standards are typically identical to one another. however, t

34、here are some significant differences between iec and american standards (e.g., claimed accuracies and thermocouple cable colors). 5.1.4consequently, it is necessary to specify thermocouples and compensating cable to a particular standard to achieve consistent color coding. particular standards are

35、likely to be preferred for certain projects to suit: local conventions client requirements 5.2 element type 5.2.1because of the many types of temperature elements available, there may be several potential solutions for any particular application. 3ps15001, rev. 3, page 5 of 32 all information herein

36、 is the confidential property of air products and chemicals, inc., unless another source is shown. this information is subject to return on demand and must not be disclosed or reproduced without prior written consent.air products and chemicals, inc., 20075.2.2for air products to achieve benefits fro

37、m standardization, this guideline recommends standard element types for most applications. 5.2.3these standard element types should be specified whenever it is practical to do so. however, other technically acceptable alternatives may be specified when there is an overriding reason to do so, such as

38、: modifications to an existing plant when a different element type is used as standard. when an existing product-based plant design is being repeated without re-engineering. 5.2.4 when no suitable precedent exists from which to select an element type, then information in the following sections shoul

39、d be considered when making a selection. 5.2.5 the following table describes some of the relative merits of rtds and thermocouples: table 1 relative merits of rtds and thermocouples consideration rtd thermocouple comment accuracy more less depending on class and range temperature range narrower 200

40、to +650 c (-328 to 1200 f) wider 200 to +2000c (-328 to 3630 f) depending on type and design of element cost more expensive less expensive small difference swamped by other costs sensitivity stem sensitive tip sensitive can result in more critical minimum insertion length for rtds speed of response

41、slower faster usually swamped by other lags (particularly thermowell response). for either an rtd or thermocouple in a typical tapered thermowell, expect a response time of 2 minutes for gas flows. vibration effects less suitable suitable particular care is required when selecting rtds for vibrating

42、 service (e.g., compressor service) long-term stability excellent less satisfactory stability of thermocouples depends on type and service. robustness more suitable less suitable cables copper cable compensating cable is required linearity slightly non-linear non-linear not an issue since transmitte

43、rs/control systems routinely perform the linearization cold junction compensation not required required not an issue since transmitters/control systems routinely perform the compensation signal level low level very low level (v) self-heating effect yes no normally insignificant. may be significant f

44、or very low gas flows. 3ps15001, rev. 3, page 6 of 32 all information herein is the confidential property of air products and chemicals, inc., unless another source is shown. this information is subject to return on demand and must not be disclosed or reproduced without prior written consent.air pro

45、ducts and chemicals, inc., 20075.3 thermocouples 5.3.1the following table describes the different standard thermocouple types currently in use at air products: table 2 thermocouple types thermocouple type name approximate working range astm e 230-03 recommendation k chromel vs. alumel 0 to 1100c 32

46、to 2012f 0 to 1090c 32 to 2000f n nicrosil vs. nisil 0 to 1250c 32 to 2282f 0 to 1090c 32 to 2000f r platinum vs. platinum - 13% rhodium 0 to 1600c 32 to 2912f 0 to 1150c 32 to 2100f s platinum vs. platinum - 10% rhodium 0 to 1500c 32 to 2732f 0 to 1150c 32 to 2100f t copper vs. constantan -200 to 3

47、00c -328 to 572f -200 to 232c -328 to 450f notes: 1. the above element temperature limits refer to the limits of use for the thermocouple type without taking into account construction issues such as wire diameter, insulation, etc., or factors such as the anticipated environment or service life. 2. t

48、he astm e 230 recommended temperature range is based on: # 18 awg dual thermocouple sheath 0.25 inch od magnesium oxide insulated enclosed in thermowell standard tolerance grade inconel sheath for temperatures 870c (1600 f). 316 ss sheath for lower temperatures. 3. other temperature ranges are avail

49、able from alternative designs in accordance with astm. 5.3.2 a brief description of each of these thermocouple types follows: 5.3.3 type k 5.3.3.1low cost, base metal thermocouple. the traditional first choice of thermocouple for moderate temperatures. 5.3.3.2subject to thermoelectric instability wi

50、th time and temperature: long-term drift with exposure to high temperatures due to compositional changes caused by oxidation. drift and failure at high temperatures due to green rot phenomenon, due to preferential oxidation of the chromium content within sealed sheaths. temperature cycling hysteresi

51、s errors caused by magnetic and structural inhomogeneities. errors caused by composition changes resulting from migration of the high vapor pressure elements (manganese and aluminum) from the negative to the positive wire. 3ps15001, rev. 3, page 7 of 32 all information herein is the confidential pro

52、perty of air products and chemicals, inc., unless another source is shown. this information is subject to return on demand and must not be disclosed or reproduced without prior written consent.air products and chemicals, inc., 20075.3.3.3 oxidation-induced errors are most prevalent above 800c (1472

53、f). temperature cycling errors are prevalent in the range 250 to 600c (482 to 1112f). 5.3.3.4 despite these disadvantages, type k is still the most commonly used thermocouple type throughout industry. 5.3.4 type n 5.3.4.1low cost, base metal thermocouple. similar in price to type k. a relatively new

54、 thermocouple type (first standardized in 1986 in bs en 60584.1 part 8, and subsequently publicized in iec 584). 5.3.4.2has the following advantages over type k: better oxidation resistance since the high levels of chromium and silicon in the nicrosil conductor and of silicon and magnesium in the ni

55、sil conductor act as a diffusion barrier. temperature cyclic effects are reduced due to the high levels of chromium in the nicrosil conductor and of silicon in the nisil conductor. migration effects are virtually eliminated since the conductors contain only traces of manganese and aluminum. 5.3.4.3

56、in summary, type n is a much more stable alternative to type k. it can also handle higher temperatures than type k, enabling it to be used as a low cost alternative to platinum-based thermocouples in many applications, including all hyco reformer high temperature applications. 5.3.5 type s 5.3.5.1 p

57、latinum metal thermocouple. in common with other platinum thermocouples: suitable for very high temperature applications. more stable than base metal thermocouples. more expensive than base metal thermocouples. generates a lower emf than base metal thermocouples. 5.3.6 type r 5.3.6.1 similar to type

58、 s except: suitable for even higher maximum temperatures. improved stability. slightly higher output. 5.3.6.2 if a platinum metal thermocouple is required for a specific application, then type r is generally technically preferred over type s. 5.3.7 type t 5.3.7.1 base metal thermocouple particularly

59、 well suited to cryogenic to warm temperatures. it is unsuitable for higher temperatures since the copper arm would rapidly oxidize. 5.3.8 thermocouple accuracy 5.3.8.1 suitable accuracy tolerance criteria for thermocouples are given in astm e230 and iec 60584-2. 5.3.8.2 for example, tolerance data

60、from iec 60584-2 is as follows: 3ps15001, rev. 3, page 8 of 32 all information herein is the confidential property of air products and chemicals, inc., unless another source is shown. this information is subject to return on demand and must not be disclosed or reproduced without prior written consen