How to install and manage oil and gas pipeline valve internal leakage cause and judgment

How to install and manage oil and gas pipeline valve internal leakage cause and judgment

The valve is an important control part in the pipeline fluid conveying system, which has various types, specifications, materials and connection modes. There ARE MANY CHALLENGES IN THE MANAGEMENT OF FIELD VALVE INSTALLATION, THIS paper briefly introduces the main control points of each link in the field pipeline valve installation, and provides reference for the management of field pipeline valve installation.
The valve is an important control part in the pipeline fluid conveying system, which has various types, specifications, materials and connection modes. There ARE MANY CHALLENGES IN THE MANAGEMENT OF FIELD VALVE INSTALLATION, THIS paper briefly introduces the main control points of each link in the field pipeline valve installation, and provides reference for the management of field pipeline valve installation.
Pipeline valve as an important part of the process system. The installation quality of pipeline valve directly determines the good realization of related functions of process system. The main control links of its management are as follows:
1, valve inspection and acceptance
1.1 Inspection of valve appearance: no pores, trachoma, cracks and rust in valve body; Stem no bending, corrosion phenomenon, stem thread is smooth, neat without broken wire; Gland with good, flexible rotation of the handwheel; Flange sealing surface without scratches, pockmarks, etc.; Thread connection in good condition; Qualified welding groove. Valve bit number, pressure and other parameters are consistent with the design.
1.2 Document inspection: Documents mainly include: quality plan, material proof, as-built drawings, test records, maintenance manuals, storage requirements, and certificate of conformity. Non-conforming valves shall have corresponding conditional release documents and entity non-conforming identification plates.
2. Valve storage and maintenance requirements
Keep valve inlet and outlet closed and place desiccant, replace regularly according to desiccant instructions. Determine temperature, humidity and environmental requirements for storage according to valve maintenance documents. For stainless steel valves, be careful to select non-halogen wrapping material. Valves should be checked and maintained regularly during storage.
3, valve pressure test
Because the valve has been done shell, seat and closing pressure test before leaving the factory, only do the closing test of the valve on site. For the scope and proportion of the verification, the national standard GB50184-2011 describes the proportion of the field pressure test, foreign standards have no requirements. Usually the owner is determined according to the quality supervision and use experience of the valve manufacturing stage, and the general valve needs to be 100% closed in the field.
3.1 Test medium requirements: the valve test medium is water; Use different levels of water quality according to the cleanliness of the system; However, when the valve working medium is gas, the test medium is preferred to use dry oil-free compressed air or nitrogen, and can also be replaced by water pressure.
3.2 Determination of closing test pressure: The requirements for closing test pressure of valves in the GB/T13927-2008 and ASME B16.34 and MSS-SP-61 are basically the same. The HYDROSTATIC TEST PRESSURE IS 1.1 TIMES THE RATED PRESSURE FOR THE VALVE PRESSURE CLASS AT 100OF, OR A PRESSURE TEST OF LESS THAN 80psi MAY BE USED INSTEAD. When THE VALVE NAMEplate IS MARKED WITH a LARGE WORKING PRESSURE difference OR THE OPERATING mechanism of the valve is not suitable for high-pressure sealing pressure test, THE test pressure can be carried OUT according to 1.1 times of THE larger working pressure difference marked with the valve nameplate.
3.3 Evaluation of test results: The valve closing test specification only requires the test to last for the shortest time, and there is no special requirement to close the test for no less than 5 minutes in actual operation. The valve sealed with flexible material shall have no visible leakage and no pressure drop of the pressure gauge during the pressure holding time. For PARTS OF THE VALVE DESIGN THAT ALLOW LEAKAGE, USSS MAY DIRECTLY MEASURE LEAKAGE PER UNIT TIME OR USE THE NUMBER OF BUBBLES OR WATER DROPLETS AS DESCRIBED IN THE MSS-SP-61 PRESSURE TEST. Leakage IS related to the nominal diameter of the valve. The leakage requirement of national standard is similar to that of American standard.
1 2 within the oil and gas pipeline valve leakage reason and judgment plays a truncated medium in the operation of the valve in the oil and gas pipelines, the flow direction of medium distribution, an important role in regulating pressure, valve * * common affect production safety problems is the leakage, the valve leakage outside the two cases are respectively valve leakage (leakage) and internal leak (leak). If it is not found and dealt with in time, there will be great safety risks, which may affect the safety of oil and gas transport production and operation and equipment maintenance and overhaul. When the valve leakage, you can listen to the scene, check whether there is obvious media leakage and other intuitive findings, but also can use combustible gas
The valve plays an important role in the operation of oil and gas pipelines, such as cutting off the medium, distributing the flow direction of the medium, regulating the pressure and so on. The common problem affecting the safety of the valve is leakage. The two cases of valve leakage are the external leakage of the valve (referred to as external leakage) and the internal leakage (referred to as internal leakage). If it is not found and dealt with in time, there will be great safety risks, which may affect the safety of oil and gas transport production and operation and equipment maintenance and overhaul. When the valve leaks, you can listen to the sound on the spot, check whether there is obvious media leakage and other intuitive findings, but also can use combustible gas detector or leak detection instrument for inspection and detection. After valve leakage, the general hiding is strong, not found in time, easy to occur pressure overload, oil pollution and other safety production accidents, such as the occurrence of different media inter-string, oil storage tank roof, downstream equipment can not be repaired, etc., the consequences are serious.
Cause of internal leakage of valve
1.1 Switch limit problem
The most important reason leading to valve leakage is the switch limit adjustment is not in place. The first STEP IN DETERMINING valve leakage is to check whether the valve switch is in place, especially to see if the valve can be fully closed in place. Most ball valves in the full position, the ball closing parts and the valve body only need to differ 2~3 degrees, it will cause the leakage of the medium. Because the plug valve has reduced diameter, so the general closing parts and the valve body difference of 10-15 degrees will cause internal leakage. Generally cause the valve switch limit is not in place mainly caused by the following situations:
(1) The valve is installed in the factory or in the process of transportation and loading and unloading, resulting in the valve stem connected accessories and valve stem drive sleeve assembly Angle dislocation resulting in limit deviation resulting in internal leakage;
(2) for assembling the ball valve of the valve set blocks, as well as buried because of the long stem, as the growth of the use of time, the valve stem rust and other impurities into the lower status of the set of, will be in between the valve stem and valve set blocks piled up some impurities such as dust, sand, rust, paint, formed in the valve closing the valve cannot be fitted in place of leakage;
(3) For the actuator that has not been maintained for a long time, due to the deterioration of the grease in the gear box into hard blocks, rust accumulation, loose limit bolts and other reasons, it will cause limit deviation and cause valve inner leakage;
(4) the valve with the actuator set the full closing position is more advanced, in the valve is not actually fully closed in place to stop action, resulting in inaccurate limit and cause internal leakage;
(5) The valve is discharged irregularly, and impurities accumulate in the valve chamber, resulting in the valve can not be fully closed in place and causing internal leakage;
(6) During operation, impurities in the tube enter between the valve body and the closing parts, resulting in the valve can not be fully closed in place.
1.2 Impurities exist in the valve
Another cause of valve leakage is always the presence of impurities in the valve. These impurities may be sand, stones, rust, welding slag, etc., but also may be tools, welding rods, wood rods, plastic products and other similar items found on the construction site. These problems are mainly caused by the following reasons:
(1) After the hydraulic test of the valve manufacturer, the water in the equipment is not discharged, or the water is not dried, anticorrosive, lubricating oil and other protective measures, resulting in internal corrosion of the valve and resulting in internal leakage;
(2) The construction site is not well protected on both sides of the valve before the installation of the valve, resulting in sediment, rain, stones and other impurities into the groove between the valve seat seal and the valve body, the seat “O” ring or spring groove, resulting in internal leakage.
(3) During the construction process, the operation is not in accordance with the rules, and the construction details are not paid attention to. The workers’ tools, welding electrodes and other sundries at the construction site enter the valve, causing the valve inner leakage.
(4) not often action of the valve, mud or impurities accumulation in the sealing surface, forming a hard cushion or the bottom of the gate valve accumulation is too much, can not be closed in place, resulting in internal leakage.
(5) Before and after the installation of the valve, the qualified grease is not injected in time, and the impurities enter the groove between the valve seat seal and the valve body, the “O” ring of the valve seat or the spring groove, resulting in internal leakage.
(6) The pigging is not maintained before and after, resulting in impurities accumulation or entering the groove after the seat, resulting in poor sealing.
(4) The valve sealed by sealing grease is not supplemented in time, resulting in the insufficient amount of sealing grease to form inner leakage.