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November 05,2023

1. Prevent valve leakage and steam leakage


All valves must undergo hydraulic tests of different levels after entering the factory.

Valves that require disassembly and maintenance must be ground.

During the repair process, it is necessary to carefully check whether any packing has been added and whether the packing gland is tightened.

Before installation, the valve must be checked for debris such as dust, sand, and iron oxide inside. If there are any debris mentioned above, it must be cleaned before installation.

All valves must be equipped with corresponding grade gaskets before installation.

When installing the flange door, the fasteners must be tightened, and the flange bolts must be tightened symmetrically and sequentially.

During the valve installation process, all valves must be installed correctly according to the system and pressure, and random or mixed installation is strictly prohibited. All valves must be numbered and recorded according to the system before installation.

2. Prevent oil system leakage and leakage

Systems with oil storage tanks must be carefully inspected and cleaned before installation.

Equipment with oil coolers must undergo a hydraulic test.


For the oil pipeline system, hydraulic testing and acid cleaning work should also be carried out.

During the installation process of the oil pipeline, all flange interfaces or threaded joints must be equipped with oil resistant rubber pads or oil resistant asbestos pads.

The leakage points of the oil system are mainly concentrated on flanges and threaded unions, so bolts must be tightened evenly when installing flanges. Prevent leakage or looseness.

During the oil filtration process, construction personnel must always stay at their work positions and are strictly prohibited from leaving or leaving their posts.

The oil filter must be stopped before replacing the oil filter paper.

When installing the temporary connection pipe for oil filter (high-strength plastic transparent hose), the joint must be securely tied with lead wire to prevent oil leakage after the oil filter has been running for a long time.

Assign highly responsible construction personnel to oversee the work of the oil filter.

Before the auxiliary oil system starts oil circulation, the engineering department shall organize a detailed technical briefing for the personnel responsible for the auxiliary oil circulation.

3. Prevent equipment and pipe fittings from bubbling, emitting, dripping, and leaking when combined

Flange sealing gaskets above 2.5Mpa are all made of metal wound gaskets.


The flange sealing gasket of 1.0Mpa to 2.5Mpa is made of asbestos and coated with black lead powder.

The flange sealing gasket of the 1.0Mpa sewage pipeline is made of rubber and coated with black lead powder.

The packing of the water pump is made of PTFE composite packing.

The sealing parts of the smoke, air, and coal pipelines should be twisted and flattened with asbestos ropes at once before joining the joint surface. It is strictly prohibited to forcefully join after tightening the screws.

4. Prevent valve internal leakage

During pipeline installation and construction, it is necessary to establish a good quality awareness, consciously clean the oxide scale and inner wall of the pipeline, leave no debris, and ensure that the inner wall of the pipeline is clean.

Firstly, ensure that all valves entering the site must undergo a 100% hydraulic test.

Valve grinding should be carried out carefully, requiring all valves (except for imported valves) to be sent to the grinding team for disassembly, inspection, and maintenance. Responsibilities should be implemented, and records and markings should be consciously made for easy traceability. Important valves should be itemized for secondary acceptance, meeting the requirements of "stamping, verification, and recording".

The first water supply and discharge valves of the boiler should be determined in advance. During the water pressure test, only these valves are allowed to be opened, and other valves are not allowed to be opened arbitrarily to protect the valve core.

When flushing the pipeline, it should be opened and closed gently to prevent damage to the door core.

5.What if the valve has already leaked? Find the cause and prescribe the right medicine!

Leakage of valve body and valve cover


The casting quality of cast iron parts is not high, and there are defects such as sand holes, loose structures, and slag inclusions on the valve body and cover body;

Cold weather and frost cracking;

Poor welding with defects such as slag inclusion, lack of welding, and stress cracks;

The cast iron valve was damaged after being hit by a heavy object.

Maintenance method:

Improve the casting quality and conduct strength tests in strict accordance with regulations before installation;

Valves with temperatures between 0 ℃ and below should be insulated or heated, and valves that are no longer in use should be drained of accumulated water;

The welding seams of the valve body and valve cover composed of welding should be carried out in accordance with relevant welding operation regulations, and after welding, flaw detection and strength testing should also be carried out;

It is prohibited to push or place heavy objects on the valve, and it is not allowed to hit cast iron and non-metallic valves with a hammer. The installation of large diameter valves should have brackets.

Leakage at the filler

The proportion of valve leakage at the packing area is the largest.


Incorrect selection of fillers, not resistant to medium corrosion, not resistant to valve high-pressure or vacuum, high or low temperature use;

The installation of the filler is incorrect, with defects such as replacing the large with the small, poor spiral wound joints, and loose upper and lower parts;

The filler has exceeded its service life, aged, and lost its elasticity;

The valve stem has low accuracy and defects such as bending, corrosion, and wear;

Insufficient number of packing rings and incomplete compression of the gland;

Damage to the gland, bolts, and other components, making it unable to be tightened;

Improper operation, excessive force, etc;

The gland is tilted, and the gap between the gland and the valve stem is too small or too large, resulting in valve stem wear and packing damage.

Maintenance method:

The materials and types of fillers should be selected according to the operating conditions;

Install the packing correctly according to relevant regulations, place and compress the packing ring by ring, and the joint should be at 30 ℃ or 45 ℃;

Fillers with long service life, aging, or damage should be replaced in a timely manner;

After the valve stem is bent or worn, it should be straightened and repaired, and those severely damaged should be replaced in a timely manner;

The filler should be installed according to the specified number of turns, the gland should be tightened symmetrically and evenly, and the pressure sleeve should have a pre tightening gap of more than 5mm;

Damaged glands, bolts, and other components should be repaired or replaced in a timely manner;

Comply with operating procedures and operate at a constant speed with normal force, except for impact handwheels;

The gland bolts should be tightened evenly and symmetrically. If the gap between the gland and the valve stem is too small, the gap should be appropriately increased; The gap between the gland and the valve stem is too large and should be replaced.

Leakage of sealing surface


The sealing surface is ground unevenly and cannot form a sealing line;

The top center of the connection between the valve stem and the closing part is suspended, misaligned, or worn;

The valve stem is bent or improperly assembled, causing the closing part to be skewed or out of alignment;

Improper selection of sealing surface material quality or failure to select valves according to operating conditions.

Maintenance method:

Correctly select the material and type of the gasket according to the working conditions;

Carefully adjust and operate smoothly;

The bolts should be tightened evenly and symmetrically, and a torque wrench should be used if necessary. The pre tightening force should meet the requirements and should not be too large or small. There should be a certain pre tightening gap at the flange and threaded connection;

The gasket assembly should be centered and aligned, with uniform stress. The gasket should not overlap or use double gaskets;

The static sealing surface is corroded, damaged, and of low processing quality. Repair, grinding, and coloring inspection should be carried out to ensure that the static sealing surface meets relevant requirements;

When installing the gasket, attention should be paid to cleanliness, and the sealing surface should be cleaned with kerosene. The gasket should not fall to the ground.

Leakage at the connection of the sealing ring


The sealing ring is not tightly rolled;

The sealing ring is welded to the body, and the welding quality is poor;

Loose sealing ring connection threads, screws, and pressure rings;

The sealing ring is corroded due to connection.

Maintenance method:

Leakage at the sealing rolling point should be fixed by injecting adhesive before rolling;

The sealing ring should be re welded according to the welding specifications. When repair welding is not possible at the weld overlay, the original weld overlay and processing should be removed;

Remove screws and pressure rings for cleaning, replace damaged components, grind the sealing and connection seat sealing surfaces, and reassemble. For components with significant corrosion damage, welding, bonding, and other methods can be used to repair them;

The sealing ring connection surface is corroded and can be repaired by grinding, bonding, and other methods. If it cannot be repaired, the sealing ring should be replaced.

Leakage caused by detachment of closing parts


Poor operation, causing the closing part to jam or exceed the top dead center, and damage and fracture of the connection;

The connection of the closing component is not secure, and it falls off due to looseness;

The material of the selected connector is incorrect, and it cannot withstand medium corrosion and mechanical wear.

Maintenance method:

Correct operation, close the valve without excessive force, open the valve without exceeding the top dead center, and after the valve is fully opened, the handwheel should be slightly reversed;

The connection between the closing part and the valve stem should be firm, and there should be a retaining part at the threaded connection;

The fasteners used for connecting the closure part and valve stem should withstand the corrosion of the medium and have a certain degree of mechanical strength and wear resistance.

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