Characteristics and Differences between Wedge and Slab Gate Valves
The sealing surface of the wedge gate valve is wedge-shaped, forming a certain angle with the centerline of the gate. Push the valve stem to close the gate. As the thrust of the valve stem increases, the positive pressure acting on the sealing surface of the wedge-shaped gate increases, which can form a forced seal and improve the sealing performance for low-pressure media. At the same time, the sealing surface of the gate opens and leaves the valve seat instantly, reducing the wear of the sealing surface.
Wedge gate valve standard: GB/T12234-2019 steel gate valves with bolted valve covers for petroleum and natural gas industries. GB/T12232-2005 general valve flange connection iron gate valve. API STANDARD 600-2015.
The gate of wedge gate valves is divided into three structural forms: wedge single gates, wedge elastic gates, and wedge double gates. By deforming the sealing surface of the wedge-shaped elastic gate and wedge-shaped double gate, a better sealing effect can be formed with the valve seat.
And effectively avoid the phenomenon of the gate getting stuck and unable to open caused by temperature changes. The sealing surface of the inlet and outlet ends of the slab gate valve is parallel to the centerline of the gate, and the sealing of a single gate valve mainly relies on the medium to push the floating gate or floating valve seat to complete.
Double gate sealing can be achieved through springs or supporting mechanisms between the gate plates. During the switching process, the sealing surfaces of the gate and valve seat are always tightly adhered to each other.
Parallel gate valve standard: GB/T23300-2009 slab gate valves. JB/T5298-2016 steel slab gate valves for Pipeline Use. API 6D pipeline valve. API 6A wellhead equipment and Christmas tree equipment.
The gate of a slab gate valve is divided into two types: single gates and double gates. At the same time, the gate can be equipped with or without a guide hole. The one with a guide hole has the same inner diameter as the valve seat, making it convenient for pipeline cleaning. It can be combined with the valve seat to form an inlet end seal, an outlet end seal, and a sealing form at both ends of the inlet and outlet.
The difference between wedge gate valves and slab gate valves
1. Different execution standards. Wedge gate valves and slab gate valves have corresponding implementation standards.
2. The shape of the gate is different. The gate shape of a wedge gate valve is wedge-shaped. The gate plate of the slab gate valve is flat and can be equipped with guide holes for easy ball passing and line sweeping.
3. The driving torque of the valve stem is different. Wedge gate valves rely on the valve stem to push the wedge gate downwards to achieve forced sealing, with high torque. Slab gate valves rely on medium pressure to tightly seal the gate and valve seat. The torque on the valve stem is relatively small.
4. The limit control mode of the distribution switch is different. The closing of the electric wedge gate valve is controlled by a torque switch, as a certain torque must be maintained to keep the valve stem pushing the gate and creating a certain sealing pressure on the valve seat. The closing of the slab gate valve is controlled by a travel switch, as long as the position of the gate is controlled.
5. Adapt to media containing suspended particles differently. The gate and seat of a wedge gate valve are separated when opened, and when closed, particulate media will enter the sealing surface, causing poor sealing and damaging the sealing surface. During the opening and closing process of a parallel gate valve, the sealing surfaces of the gate and valve seat are always in contact, and particles in the medium cannot enter the sealing surface, making it more suitable for working conditions with media containing particles.
6. The impact of excessive temperature difference on the gate varies. When the temperature rise of the wedge gate valve is too high in the closed state, the valve stem will expand and elongate, causing the gate to jam. The elongation of the valve stem of the slab gate valve has no effect on the sealing of the gate plate, and the gate plate will not get stuck.
7. The valve stem position protection for rising stem gate valves is different. The valve stem of the rising stem wedge gate valve is leaking outside without a protective cover. The upper part of the valve stem of the rising stem slab gate valve has a protective cover, which can protect the valve stem threads from dust and rainwater corrosion, and has an opening indicator.
8. Are the packing and gate positions sealed with grease? The packing sealing position and gate sealing of wedge gate valves generally do not require sealing grease. Slab gate valves, due to the tight fit between the gate plate and the valve seat during the opening and closing process. It can increase lubrication, reduce wear, and enhance sealing effect by adding grease. Adding grease to the packing can prevent the packing from drying out and lubricate the valve stem.
