Valve pressure test for a long time all rely on daily careful maintenance and maintenance
In general, valves are not strength tested, but repaired bodies and covers or corroded ones should be. For safety valves, the constant pressure, return pressure and other tests should comply with their specifications and related regulations. When the test, low pressure, large diameter unimportant valves and valves that have provisions to allow leakage are allowed to have trace leakage phenomenon; As general valves, power station valves, Marine valves and other valves have different requirements, the leakage requirements should be implemented according to the relevant regulations.
(1) When the hydraulic test, the valve air will be eliminated as far as possible.
(2) During the test, the valve installation position should be in the direction of easy inspection.
(3) cast iron valve strength test, the application of copper hammer tap valve body and valve cover, check whether there is leakage.
(4) For welded valves, conical seal or O-ring seal can be used for pressure test when the pressure test is not good with huang plate.
(5) After the pressure test of the valve, the water in the valve should be removed in time and cleaned, and the test record should be made.
(6) The pressure should be gradually increased during the test, and sharp and sudden pressurization is not allowed.
(7) when the valve is tested, except for the sealing surface of the plug valve is allowed to be oiled, other valves are not allowed to be oiled on the sealing surface.
(8) Throttle valve should not be closed parts of the sealing test, but should be strength test and packing and gasket sealing test.
(9) In the pressure test, the valve closing force only allows one person’s normal physical strength to close; Do not use tools such as levers (except torque wrenches), when the diameter of handwheel is greater than 320mm, two people are allowed to close together.
(10) when the valve pressure test, the pressure of the blind plate on the valve should not be too large, so as not to produce deformation of the valve, affecting the test effect (if the cast iron valve is too tight, it will be damaged).
(11) Any valve with a driving device, the sealing test of the application of the driving device to close the valve for sealing test. Manual drive device should also be used to close the valve seal test.
(12) strength test and sealing test installed on the main valve by-pass valve, in the main valve strength and sealing test; When the main valve shutoff is opened, it should also be opened.
(13) Safety valve installation should be strength and sealing test. Low-pressure safety valve spot check 20%, such as unqualified should be 100% inspection; Medium and high pressure safety valves should be 100% inspected.
(14) The valve with the upper seal should take out the packing for sealing test, the upper seal officer closed, check whether leakage. When testing with gas, fill the stuffing box with water for inspection. For packing sealing test, the upper seal is not allowed to be in a tight position.
(15) Strength test and sealing test duration is generally 2~3min, important and special valves should last 5min. Small diameter valve test time can be shorter, large diameter valve test time can be longer. During the test, if there is any doubt, the test time can be extended. Sweat or leakage of body and bonnet shall not be allowed during strength test. Sealing test, rotor pump general valve only once, safety valve, high pressure valve and other raw valves need to be carried out twice. When the test, low pressure, large diameter unimportant valves and valves that have provisions to allow leakage are allowed to have trace leakage phenomenon; As general valves, power station valves, Marine valves and other valves have different requirements, the leakage requirements should be implemented according to the relevant regulations.
In general, valves are not strength tested, but repaired bodies and covers or corroded ones should be. For safety valves, the constant pressure, return pressure and other tests should comply with their specifications and related regulations. Hope the above share 15 valve pressure test common technical problems, to help you!
Valve with long rely on daily careful maintenance and maintenance
The valve is mainly used to isolate equipment and pipeline system, adjust flow, prevent backflow, adjust and discharge pressure, fluid pipeline system control components, the role is significant, so in the usual use process need to pay attention to the maintenance and maintenance of the valve. Here is to introduce the daily maintenance of valves.
One, the daily maintenance of the valve
1. Attention should be paid to the storage environment of the valve. It should be stored in a dry and ventilated room and blocked at both ends of the channel.
2. The valve should be checked regularly, and the dirt on it should be smeared with anti-rust oil on its surface.
3. After the installation and application of the valve, it should be repaired regularly to ensure its normal work.
4. Check whether the sealing surface of the valve is worn and repair or replace it according to the situation.
5, check the trapezoidal thread wear of the stem and stem nut, whether the packing is outdated and invalid, and carry out the necessary replacement.
6, the sealing performance of the valve should be tested to ensure its performance.
7. The valve in operation should be intact, the bolts on the flange and bracket are complete, the threads are not damaged, and there is no loosening phenomenon.
8, if the hand wheel is lost, it should be ready in time, and can not be replaced by a adjustable wrench.
9. Packing gland is not allowed to be skewed or without preload clearance.
10, if the valve use environment is more bad, vulnerable to rain, snow, dust, sand and other dirt contamination, should be installed for the stem protective cover.
11, the valve on the scale should be kept complete, accurate, clear, valve seal, cap.
12, insulation jacket should not sag, crack.
13, in operation of the valve, avoid knocking on it, or support heavy objects, etc.
Two, valve grease maintenance work
The professional maintenance of valves before and after welding production plays a vital role in the production and operation of valves. Correct and orderly and effective maintenance will protect valves, make them function normally and extend the service life of valves. Valve maintenance seems simple, but it is not. There are often overlooked aspects of work.
***, valve grease, often ignore the amount of fat.
After grease injection and refueling, the operator selects the valve and grease injection connection mode to carry out grease injection operation. There are two situations: on the one hand, less fat injection is insufficient, and the sealing surface is accelerated by the lack of lubricant. On the other hand, excessive fat injection, resulting in waste. There is no accurate calculation of different valve sealing capacities based on valve type and category. The sealing capacity can be calculated by valve size and type, and then reasonable injection of appropriate grease.
Second, the valve grease, often ignore the pressure problem.
During the operation of fat injection, the pressure of fat injection showed a regular peak and valley change. The pressure is too low, the sealing leakage or failure pressure is too high, the grease injection mouth is blocked, the grease in the sealing is hardened, or the sealing ring is locked with the valve ball and valve plate. Usually when the grease injection pressure is too low, the injected grease flows into the bottom of the valve chamber, which generally occurs in small gate valves. If the fat injection pressure is too high, on the one hand, check the fat injection nozzle and replace it if the blockage of the fat hole is identified; On the other hand, grease hardening, to use cleaning liquid, repeatedly soften the failure of the sealing grease, and injection of new grease replacement. In addition, sealing type and sealing material also affect the grease injection pressure, different sealing forms have different grease injection pressure, in general, the hard seal grease injection pressure is higher than the soft seal.
Post time: Jun-15-2022
