Taboos and measures in forged steel valves pipeline construction-part one
Taboo 1: The main materials, equipment and products used in construction lack technical quality identification documents or product certificates that meet the current national or ministerial standards.
Consequences: The quality of the project is unqualified. There are latent dangers of accidents. It cannot be accomplished and put into use on time, and it must be reworked and repaired, resulting in delays in construction period and increased investment in labor and materials. Measures: The main materials, equipment and products used in water supply, drainage, heating and sanitation projects shall have technical quality appraisal documents or product certificates that meet the current standards issued by the state or the ministry; their product names, models, specifications and national quality standards code, date of manufacture, manufacturer's name and location, factory product inspection certificate or code shall be indicated.
Taboo 2: The forged steel valve is not subjected to the necessary quality inspection before installation.
Consequences: The forged steel valve switch is inflexible in the system operation, the shutdown is not strict and the phenomenon of water (steam) leakage occurs, causing reworking and repairing, and even affecting the normal water (steam) supply.
Measures: Before the installation of forged steel valves, the compression strength and tightness test should be done. The test should be carried on by checking 10% of each batch quantity (same brand, same specification, and same model), and not less than one. For closed-circuit forged steel valves that function as a cut-off and are installed on the main pipe, the strength and tightness tests shall be made one by one.
Taboo 3: The specifications and models of the installed forged steel valves do not meet the design requirements. For example, the nominal pressure of the forged steel valve is less than the system testing pressure. the gate valve is used when the pipe diameter of the water supply pipe is less than or equal to 50 mm; the dry pipe and the stand pipe of the hot water heating adopt a globe valve; and the fire pump suction pipe adopts a butterfly valve.
Consequences: It will affect the normal opening and closing of forged steel valves and affect the valve's other function like adjusting the resistance and pressure. It may even cause the forged steel valve to be damaged and forced to repair during the system running.
Measures: Be familiar with the application range of all kinds of forged steel valves, and select the specifications and models of forged steel valves according to the design requirements. The nominal pressure of the forged steel valve must meet the requirements of the system testing pressure. According to the requirements of construction specifications: if the water supply pipe diameter is less than or equal to 50 mm, a forged globe valve should be used; when the pipe diameter is bigger than 50 mm, a forged gate valve should be used. The hot water heating dry and vertical control valves shall adopt gate valves, and the fire pump suction pipes shall not adopt butterfly valves.
Taboo 4: The installation method of the forged steel valve is wrong. For example, the water (steam) flow direction in the shut-off valve or check valve is opposite to the sign, the valve stem is installed downward, the horizontally mounted check valve is installed vertically, the rising stem gate valve or the butterfly valve handle has no opening and closing space, and the valve stem of the concealed installed forged steel valve does not face the inspection door.
Consequences: Forged steel valves do not work, switch maintenance is difficult, and the valve stem facing down often causes water leakage.
Measures: Install the forged steel valve strictly according to the installation instructions. For the rising stem gate valve, leave enough space for the stem opening and extending. For the butterfly valve, fully consider the handle rotation space. For all kinds of forged steel valves, the stems cannot be lower than the horizontal position, and cannot be installed downward. The concealed forged steel valve should not only be set to meet the inspection door required for the opening and closing of the forged steel valve, but also the valve stem should face the inspection door.
To be continued...