Guidelines for Installing and Maintaining Soft-Sealed Knife Gate Valves

The soft-sealed knife gate valve is a valve that uses a seal made of elastic material to control the flow of fluid through the movement of the gate. It is characterized by good sealing performance, small opening and closing torque, and long service life. This article will introduce the material selection, maintenance recommendations, installation steps and precautions of the soft-sealed knife gate valve in detail.

I. Material selection of soft-sealed knife gate valves

1.1 Valve body material

The selection of valve body material should take into account the working environment and medium characteristics of the valve. Commonly used materials include cast iron, ductile iron, carbon steel, stainless steel, etc. For corrosive media, it is recommended to choose stainless steel or plastic-lined materials.

1.2 Sealing material

Soft sealing materials usually include EPDM, NBR, PTFE, etc. EPDM is suitable for hot water, steam and other media; NBR is suitable for oil and hydrocarbon media; PTFE has excellent corrosion resistance and high temperature performance.

1.3 Valve stem material

The valve stem material should have good strength and corrosion resistance. Commonly used materials include stainless steel and alloy steel. For high temperature and high pressure conditions, it is recommended to choose alloy steel.

II. Maintenance recommendations for soft-sealed knife gate valves

2.1 Regular inspections

Regularly check the sealing performance and opening and closing conditions of the valves, and handle any abnormalities in a timely manner. Pay special attention to checking the wear of the seals and replace them if necessary.

2.2 Cleaning and lubrication

Regularly clean the inner and outer surfaces of the valves to keep them clean. For valves that are frequently opened and closed, grease should be added regularly to reduce friction and wear.

2.3 Anti-corrosion treatment

For valves exposed to the atmosphere, anti-corrosion treatment should be performed regularly to prevent corrosion of the valve body and valve stem. Common anti-corrosion measures include applying anti-rust paint and electroplating.

III. Installation steps and precautions for soft-sealed knife gate valves

3.1 Installation steps

1). Check the valve: Before installation, check whether the valve model, specification and pressure rating meet the design requirements. Confirm that the valve sealing surface is not damaged.

2). Clean the pipeline: Make sure there is no welding slag, iron filings and other debris in the pipeline to prevent damage to the seals.
3). Install the valve: put the valve into the pipeline, fix the flange with bolts, and pay attention to tightening the bolts diagonally to prevent uneven force.
4). Adjust the valve: after installation, open and close the valve manually to ensure flexible opening and closing without jamming.

3.2 Precautions

- Directionality: The soft-sealed knife gate valve has directionality. When installing, pay attention to the direction of the medium flow consistent with the arrow on the valve body.

- Prevent over-torque: When opening and closing the valve, do not use excessive force to prevent damage to the seal and valve stem.

- Avoid high temperature: Avoid installing the valve in a high temperature environment to prevent aging and deterioration of the seal.

- Antifreeze measures: In cold areas, antifreeze measures should be taken to prevent the valve from freezing.

As an important control device, the material selection, maintenance and installation of the soft-sealed knife gate valve directly affect the performance and life of the valve. Through reasonable material selection, regular maintenance and correct installation, the use efficiency and life of the soft-sealed knife gate valve can be effectively improved. I hope the content of this article can provide useful reference for users.

References

1. GB/T 12232-2005  《General valves - Manual iron and copper gate valves》
2. JB/T 5300-2005  《Valve model compilation method》
3. HG/T 20592-2009  《Steel pipe flange》
4. API 6D-2007  《Pipeline valves for petroleum and natural gas industries》