Solution for accidental fall off of the valve plate of rising stem wedge gate valve

In the previous Tanghai valve knowledge, we have mentioned that if the working conditions are too bad or the gate valve purchased is from an unqualified small manufacturer, or for the rising stem wedge gate valve, the valve will suffer corrosion and wear during the opening and closing process. Or improper operation may cause the valve plate

to be disconnected from the valve stem. Once this happens, it will undoubtedly be troublesome for the production pipeline and even cause huge losses. So, if this situation has already happened, how can we deal with it?
Generally speaking, if the valve cannot be opened after it has been closed, it can only be replaced after cutting it out of the piping system. This is mainly for the welding connection. If the gate valve cannot be cut out from the system, another connection process or device shutdown is required. Take the rising stem wedge gate valve as an example, the specific repair methods are as follows:

1. The valve plate falls off but cannot be cut out for processing
Under the condition of ensuring that the medium is sealed, the valve plate can be exposed by changing the assembly methods of the gland, valve stem, packing, etc., and then the valve stem and the valve plate can be restored by conventional methods. This is to ensure that the three seals of the valve can continue to be maintained. After the bonnet is disassembled, the wedge angle of the valve plate is in the friction angle domain, so no matter whether the two ends of the valve plate are under pressure or not, the valve plate will not squeeze out of the valve seat by itself under the self-locking condition.

2. The valve plate falls off, the handwheel can still be turned
(1) In this case, the valve plate can be pushed back to the valve seat to form a seal through the handwheel. Loosen the packing nut but not completely. Loosen the packing first, and do the same for all the nuts on the bolts on the valve cover in turn.
(2) Next, turn the handwheel in the closing direction. The valve stem should be in a state where it will not move anymore. The upper part of the valve cover is separated from the valve body as a whole to ensure that the valve plate and the valve seat are indeed sealed or only A small amount of medium leakage that affects construction treatment. At this time, completely unscrew the nuts on all bolts, remove the upper part of the valve cover and the valve stem, and the top of the valve plate in the valve seat is exposed. Then check the reason and solution of the valve plate falling off.
(3) If it is not for special conditions, welding is generally used to re-establish the connection between the valve stem and the valve plate. However, if it is flammable and explosive oil, gas and other media, it is very unsafe to weld directly in this way. In this case, the end of the valve stem can be taken out and processed into the special form required. During installation, the contact surface of the valve stem and the valve core is treated with a high-strength adhesive repair agent, or directly drilled at the top of the valve plate. Tapping is changed to threaded connection. Special attention is to be paid to the valve stem and bonnet during the repair, which must be installed on a vertical plane to maintain good neutrality, so as to avoid opening difficulties when restarting.
(4) The sealing gasket should be replaced according to the situation to prevent leakage after the sealing surface is put into use, and then part of the packing should be added to the stuffing box as needed, and the packing gland should be properly compressed.

The above method can be used to repair the exposed rod wedge gate valve in a very short time. The repair requires less manpower and short working hours. The cost is mainly for disassembly, welding, bonding or drilling. The construction and material costs can be controlled within 1,000 yuan. . Practice has proved that the above method will open and close normally after repairing the valve, avoiding the loss of production shutdown, and will reduce the direct and invisible property loss of the enterprise. For more details about rising stem wedge gate valves, please contact Tanghai Valve’s online customer service.

TH Valve is a professional manufacturer of butterfly valve, gate valve, check valve, globe valve, knife gate valve, ball valve with API, JIS, DIN standard, used in Oil, Gas, Marine industry, Water supply and drainage, fire fighting, shipbuilding, water treatment and other systems, with Nominal Diameter of DN50 to DN1200, NBR/EPDM/VITON, Certificates & Approvals: DNV-GL, Lloyds, DNV, BV, API, ABS, CCS. Standards: EN 593, API609, API6D

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