Analysis on the Content of JB / T4088 - 2012 Standard for Tubular Electric Heating Elements
The standard for new tubular components for daily use has been in effect since November 2012. I was a member of the revised edition of the Standard 98 and the revised version of 2012. I am familiar with the standard. The new version of the standard compared with the old version of a lot of content has been modified, in addition to the gate and increase. In order to facilitate the domestic enterprises to accurately understand and facilitate the operation, and further to the new standard as a benchmark to improve the technical level of daily tubular electric components to adapt to the needs of domestic and international application market. I am here to this article on the new standards related to the provisions of a number of changes in the analysis, treatment, in this and everyone to communicate. Since I am not within the scope of official duties, all views can only be of an academic nature and do not have any interpretive authority. All content is for reference only!
1 range
Compared with the old version, the voltage was changed from 440V to 480V, and the power was changed
from 4000W to 6000W. This is to adapt to market development needs.
Terms and Definitions
2.1 The new standard on the definition of damage to a little change, the old standard on the
withstand voltage value is less than the specified value is damaged, and the new standard to
withstand the voltage value is lower than 75% of the normal value of damage. Pressure 1500V
product is intact, after a period of use can only withstand 1200V pressure, this product can not
use the old standard, and the new standard that is not damaged.
2.2 An explanation of the equivalent resistance has been added
The equivalent resistance is primarily used as an alternative to the quick inspection of the power
delivered to the factory. We all know that most of the varieties of electric components can not be
carried out by the power of one by one, (because the surface of the tube after the oxide layer and
time-consuming) Therefore, most manufacturers are measuring DC resistance to determine the power
of qualified or not. However, due to resistance wire material at different temperatures its
resistance has a certain change, we are accustomed to this change is called resistance temperature
coefficient. Here refers to the equivalent resistance is different according to the operating
temperature, measured resistance multiplied by a factor multiplied by the element than the normal
temperature of the temperature value.
The relationship in the standard: R (T) = R0 [1 + a (T-T1)]
Equivalent resistance = normal temperature resistance x [1 + resistance fixed temperature
coefficient (operating temperature - normal temperature) for this formula I have two ideas;
A temperature coefficient of resistance is directly related to the temperature of course, but it is
not a linear relationship.
B The resistance wire has a correction factor for the relevant temperature coefficient in the
professional standard of the resistance wire. This correction value refers to the temperature of
the resistance wire itself, not to the surface temperature of the element.
In view of the above two points, I think this formula can not be accurately calculated. So I
suggest that resistance wire should be at different temperatures when the correction value into
the formula for calculation.
R (T) = Ro x Ct
The text describes: equivalent resistance = temperature resistance x temperature coefficient
For example: a component 220V 1000W work when the component surface temperature of 300 ℃, the
resistance wire itself temperature 450 ℃,
Look-up table at this time resistance wire corresponding to the correction value, and then into
the calculation. Here suggest: resistance wire material with different correction factor is
different. It is important that the equivalent resistance is accurate (consistent with the accuracy
of the power). It is recommended that the manufacturer verify the thermal resistance of the
component at the simulated operating temperature (this is the true equivalent resistance). The
verification steps are as follows:
A first measured cold resistance;
B Connect the component to the power supply to allow the component to reach its normal operating
temperature;
C When the temperature is stable, note down the power (display voltmeter /, power meter must be
accurate);
D the measured power value into Ohm's law to calculate: the equivalent resistance = the square of
the voltage / measured power value
E calculate the number of resistance temperature ct = equivalent resistance / cold resistance
Ohm's Law for the calculation is very accurate, no doubt, if the conditions can be equipped with
electronic bridge that is power measurement. In the actual work of enterprises on the equivalent
power of alternative resistance to the scope of control should be left a certain margin.
3. Classification
Compared with the old standard more refined, the shape, whether the vibration, whether embedded,
heating characteristics of classification.
4. Technical requirements
Compared with the old standard to the C grid content; around no explosive, flammable, corrosive
gases and conductive dust. The grid goes to the ring temperature.
4.2 Power deviation requirements are not changed
4.3 Leakage current The original standard of not more than 0.5mA revised wood for more than 0.75mA. Here to explain, is not required to reduce, in essence, is due to the scope of the new standard is 6KW, we all know that the size of the leakage current and the size of the power has a certain relationship, so revised to 0.75mA power expansion is normal
4.4 electrical strength compared with the old standard to increase the requirements under the cold
condition, in fact, this requires the production enterprises have been operating as a normal
project. Because it is cold, so than the working temperature and the tide condition under the
requirements of increased, so as 1500V. For the working voltage greater than 250V product voltage
is 1.2 times the working voltage plus 1250V, the working temperature of the voltage value is 1.2
times the working voltage plus 800V, the tide of the voltage value of 1.2 times the operating
voltage plus 1000V.
4.5 to increase the requirements of harmful substances limits, in this regard the production
enterprises to control.
4.6 General structural aspects
4.6.1 Adjust the tube body temperature limit in the old standard to Appendix C. Normative
information
4.6.2 Adjust the wall thickness limit of the metal pipe to Appendix D. Information material
4.6.3 Adjust the insulation thickness and creepage distance between the electrodes of the component
and the housing to see Appendix D.
4.6.4 In the new standard, the length limit of the rod in the pipe is greatly changed from the old
standard.
A Change the value of the pipe diameter to the interval value. So that in the actual work on the easy operation.
B rationalize the lead rod specifications and diameter specifications with the rationality. For
example, the original standard diameter diameter of 6.5mm supporting rod diameter 3mm-4mm, which
is not realistic, and the new standard in the diameter 6.5mm matching leads between 2mm-2.5mm, this
is In line with the use of. Here suggest that: If the customer is required to produce diameter 6,5
mm and supporting rods for the diameter of 3mm, then it is not to meet the standard requirements.
The standard form content is mainly to length can not be too short, if the length is less than the
table requirements should be unqualified.
4.6.5 Tolerance of the geometric dimensions of the new standard GB / 1804 in the assessment by the
V-class, so that the old standard with the
More practical.
4.7 On the heating uniformity in the standard has no specific requirements, but referred to the
temperature limit of the pipe body requirements. (Appendix C)
I have a few ideas for the heat uniformity:
A first of all affirmed in the future of our products used in the metal material temperature
requirements must comply with the requirements of Appendix C;
B Appendix C can not replace the heating uniformity requirements, as the tubular electric heating
element is concerned, it is a power after the heating body, the tube surface temperature should be
uniform, the work can be uniform to the heating of various substances, the reality In which no
heating device does not require uniform heating. Secondly, we all know that the electric components
with the temperature of its insulation safety performance will change. In the same conditions, the
higher the temperature the greater the leakage current; then the resistance wire is also the
higher the temperature the shorter the life.
C I think the uniformity of the fever or should be assessed, but the old way of the components of
the X-ray film inspection is not easy to operate and can not guarantee accuracy. Can not guarantee
the exact reason is: to achieve uniform heating tube surface In addition to the resistance from
the density of uniform density of wire packing must also be uniform, or the tube surface
temperature is not necessarily uniform.
D of the component heating uniformity of the assessment methods:
D1 components connected to the power to be stable after the temperature test;
D2 if the surface load is too large should be reduced voltage for testing;
D3 must be measured using a surface temperature thermometer:
D4 temperature requirements should be controlled at 10% is moderate (refer to the relevant foreign
standards), this requirement does not reduce the comparison with the old standard;
D5 on the surface of the component evenly distributed 5-point test and calculation, for the
intuitive uniformity of the fever must be used as a point test;
D6 is calculated as follows:
, Tc = max [| 1- (Tn / T flat) |] × 1%
In the formula:
Tc ---- temperature difference
Tn ---- any point temperature
T Average of all test points
4.8 The requirements of the new standard for tensile testing of lead-out bars are the same as those
of the old standard, but the requirements for tensile tests and inserts for welded lugs on lead
bars are increased.
In view of this content I view is as follows:
A electrode sheet is a small part, but it is very important with the lead out of the stick, if
the contact will be in the process of using the ignition or out of touch, the general electrical
lugs are charged, the emergence of this The situation is very dangerous.
B Electrode inserts, like lugs, are also important in their size requirements in addition to
their secure contact with the lead-out bar. If the size of the thickness of thin, then the use of
poor contact, this is a security risk. Based on this point, it is recommended that attention
should be paid to manufacturing enterprises. Familiar with the relevant requirements in GB / 17196
(insert standard), the size requirements and insertion force should be strengthened and controlled
.
4,9 new standards to increase the anti-dry requirements
Anti-dry test is mainly for liquid heating elements in the junction scale, dehydration, the
components from the liquid into a gas plus
Heat and the contents of the assessment. For dry-burning conditions, there is no clear requirement
in the standard, written only in consultation with the user. Correct
In the anti-dry test I have the following view:
A standard has been expressly provided for must be implemented, but because of this test,
components, if the use of copper pipe is clearly not suitable;
B. It is not possible to use a dry-burning test to ensure that the water element can be completely
safe (no thermal breakdown, no bursting, no burn-out) after the scale has been applied, since the
packing inside the element sometimes takes a long time Will change.
C In order to adapt to the dry burning test, we need to adjust the design of water components, tube
surface load to reduce, if the load is still relatively large can not use modified magnesium oxide
, and to select high-temperature magnesium oxide.
D standard of the pipe surface load is greater than 10W of the article does not apply, so I think
it is wrong, because the tube surface load the greater the scale of the device components, the
faster the scale, the electrical properties of the possibility of the decline of the more Big.
Based on this we must have this understanding of production enterprises, can not have a lucky
heart, (not assessment of dry), whereas 10W negative charge of the product should consider the use
of filler selection of high temperature magnesium oxide.
In order to improve the technical performance of water heating elements to ensure that no burst,
no heat breakdown burned, I also wrote a reference for information.
4.10 The new standard adds to the flammability requirements of the sealing material
This article basically according to the requirement in GB / 4706.1.
5 on the test method
5.1 on the measuring instruments to increase the humidity of the instrumentation and precision
requirements.
5.2 Measuring power I suggest to be equipped with a regulated power supply, the test voltage should
be measured first, to ensure accurate measurement of electrical power after the voltage can be
accurate. As mentioned earlier, the equivalent resistor center value must be verified by a power
test at a simulated operating temperature.
5.3 Leakage current measurement at operating temperature
Specific methods of testing and attention to items:
A component must be insulated from the earth;
B at a simulated operating temperature;
C adjust the voltage to 1.15 times the rated power voltage;
D Both ends of the component are measured, whichever is greater.
Here suggest that in the course of the test if the peak and then down, then this component should
be the peak to determine the results. Because as an electrical product in the course of the moment
if there is a security risk, product manufacturers can not avoid responsibility.
5.4 Sealing test and leakage current test after water pressure
These two states of the leakage current are in fact the scope of cold leakage current on the cold
leakage current test most companies do not seriously done, in fact, it is a substitute insulation
resistance test method, because the standard from the 98 version to cancel Insulation Resistance
Item Requirement. Test method is the use of AC voltage, (1.06 times the rated voltage), components
are not energized, AC voltage is applied between the electrode and the shell.
Add: No. 16, Road 3, Sanjiang Industry Zone, Shengzhou, Zhejiang, China
Contact:Eric Xie
Email: sale@benoelectric.com
Mob: +861598895936
Skype: ericxie123@outlook.com
Wechat & Whatsapp: +8615988295936
Website:www.benoindustry.com
