GOST 28800-90
GOST 28800−90 Pipe metal. Method for the determination of moisture on the internal surface of pipes
GOST 28800−90
Group В69
INTERSTATE STANDARD
PIPE METAL
Method for the determination of moisture on the internal surface of pipes
Metal pipes. Method for determination of moisture on the internal surface of pipes
ISS 17.040.30
AXTU 1709
Date of introduction 1991−07−01
INFORMATION DATA
1. DEVELOPED AND INTRODUCED by the Ministry of metallurgy of the USSR
2. APPROVED AND put INTO EFFECT by Decision of the USSR State Committee on management of quality and standards from
3. The standard fully complies ST SEV 6739−89
4. INTRODUCED FOR THE FIRST TIME
5. REFERENCE NORMATIVE AND TECHNICAL DOCUMENTS
| The designation of the reference document referenced |
The partition number |
| GOST 4204−77 |
2 |
| GOST 9293−74 |
2 |
| GOST 13374−86 |
2 |
6. Limitation of actions taken by Protocol No. 5−94 of the Interstate Council for standardization, Metrology and certification (ICS 11−12−94)
7. REPRINTING. September 2010
This standard specifies a method for determining the moisture on the internal surface of metallic pipes with outer diameter from 3 to 54 mm, designed for use in refrigeration plants using refrigerants.
The method is based on purging the sample tube, dried with nitrogen, the subsequent absorption of moisture by the pentoxide of phosphorus, which is in a V-shaped tubes of the test set, determining the change in mass and the conversion of the mass of moisture per unit area.
1. METHOD SAMPLE SELECTION AND PREPARATION
1.1. The sample size and location sampling set in the normative-technical documentation for pipe.
1.2. For the test samples of pipe are selected so that the inner surface was not less than 0.2 m.
2. EQUIPMENT AND REAGENTS
Installation for testing is going according to the scheme indicated in the drawing.
Drawing. Diagram of the setup for the test
Cylinder filled with nitrogen, and containing not more than 0.5% volume of oxygen.
The regulating valve.
Drying tower with tube, with a capacity of 250−500 cm, filled with glass wool and phosphorus pentoxide.
The heating chamber.
V-shaped glass tube (2 PCs) with a diameter of 14.5 mm and a height of 80−100 mm with a glass tube filled with glass wool and phosphorus pentoxide.
A flow meter.
Analytical scales with the greatest limit of weighing of 200 g and a measurement error of ±0.1 mg.
Timers bubbles (2 pieces) filled with concentrated sulfuric acid.
A glass or copper tube to connect with the sample.
Heat resistant rubber hose for connection of the ends of the tubes.
Of phosphorus pentoxide.
Wool.
Sulfuric acid according to GOST 4204.
Vacuum oil GOST 13374 for sealing the lapped traffic of V-shaped tubes.
Nitrogen according to GOST 9293.
3. PREPARING FOR THE TEST
3.1. Before testing, the V-shaped tube containing phosphorus pentoxide, weighed with an accuracy of 0.1 mg.
3.2. Installation preparation to the test
The test set is collected without the test sample.
Extending from the drying tower (4) pipeline connects the V-shaped tube (7). Then, after the installation of the missing nitrogen with a flow rate of 5 l·h. V-shaped tubes (7 and 8) is removed from the test set and weighed. This process is repeated until constancy of mass (
).
Constant mass is considered reached when the mass difference of the two weighings after transmission of nitrogen (not less than 5 h) not more than 1 mg.
4. TESTING
4.1. The test is performed as follows: nitrogen from the cylinder 1 through the valve 2 and the timer bubbles 3 is passed through a drying tower 4 and through the sample 6placed in a heating chamber 5. There nitrogen absorbs evaporating due to the heating of moisture that flows through the V-shaped tube 7 and 8, is filled with phosphorus pentoxide, where the moisture is absorbed.
After passing through the timers of the bubbles 9 and flow meter 10, the nitrogen is released into the air.
The timers of the bubbles 3 and 9 serve as a safety device against the penetration of atmospheric moisture into the instrument.
4.2. The flow passing in nitrogen during testing should be between 5 and 10 l·h.
________________
* The text of the document matches the original. — Note the manufacturer’s database.
4.3. Testing time — not less than 3 hours.
4.4. During the test, the specimen is heated to a temperature of (105+5)°C.
4.5. After a time of testing both V-shaped tube filled with phosphorus pentoxide, and weighed to determine the change in their mass. To prevent weighing errors due to fluctuations in temperature and air pressure the weight gain of the first V-shaped tube are corrected by changing the mass of the second V-shaped tube in the following way:
— in case of weight gain the second V-shaped tube 8 is subtracted from her weight gain the first V-shaped tube 7;
— in the case of reducing the mass of the second V-shaped tube 8 is added to her weight gain the first V-shaped tube 7.
5. PROCESSING OF THE RESULTS
5.1. A lot of moisture () in milligrams is calculated by the formula:
— if weight gain second V-shaped tube 8
— by reducing the mass of the second V-shaped tube 8
where is the change of mass of the first V-shaped tube 7, mg;
absolute mass changes of the V-shaped tube 8, mg.
5.2. A lot of moisture (a), in milligrams per square meter of the inner surface of the sample, is calculated by the formula
where is the internal surface area of the specimen, m
.
