Soft Back Seat Butterfly Valve–Seat Material Selection & Machining Process


If a customer asks me what is the most important part of soft seal butterfly valve, I will tell him it is the valve seat. There is no doubt that the sealing of valve seat performance, the capacity of the pressure-bearing, directly determines the quality of the butterfly valve. So what kind of seat is an excellent seat? How many kind of soft seal valve seat? let’s discuss these issues.

Rubber seat of soft seal butterfly valve can be divided into hard back rubber seat and soft back rubber seat.

seat of butterfly valves

1. differences between soft back seat and hard back seat:

  • Hard back seat is pressed in the valve body with a mold, it is not easy to replace by yourself, besides, hard back seat edge is thin. In contrast, the soft back valve seat is manufactured according to the mold, it is more convenient to replace by yourself, and it can be used many times to save the cost. Meanwhile the edge of the soft back seat is wider, so when the pipeline is connected to the valve, the non-special flange for butterfly valve can be used, and the sealing performance is as good as the special flange. In addition, the pressure-bearing capacity of the soft back seat is better than that of the hard back seat.
  • The service life of the soft back seat is longer than the hard back seat, During the long -term operation of the valve, when the valve seat axis is worn and leaks, the valve seat of the hard back is directly penetrated to the external phenomenon of the valve body. The soft back is a large and wide -edged structure, so this will not occur.

2. How is the rubber valve seat processing? What are the factors that determine the performance of the soft secret valve seat?

Now, let’s discuss it together.

The rubber valve seat is mixed of a certain proportion of natural rubber, charcoal black, and some other additives. After mixing, it would be pressed into black rubber tablet by machine.The addition of charcoal black strengthens the tensile performance and strength of rubber.

After the first time it is pressed into a rubber tablet, we need to test the rubber sample of the performance, to obtain the suitable vulcanization temperature and time.

Raw rubber that passes the test before it can be used for rubber production. Qualified raw rubber needs to be stretched and shaped again by the machine, according to the mold to make the initial shape of the soft valve seat raw rubber or hard back valve seat, and finally, put it inside the vulcanizing machine, according to different rubber materials and sizes, set up different vulcanization time, vulcanization temperature, pressure, and finally vulcanize it to become a mature rubber.

soft back seat process

3. The quality of the rubber soft back seat of butterfly valve is determined by the following factors.

  • First, the content of natural rubber;
  • Second, the ratio of natural rubber and carbon black;
  • Thirdly, the vulcanization time and whether the temperature is enough.
  • Fourth, whether the technology of the vulcanizing factory is mature or not;

4. Zfa Valve can provide what kind of rubber seat? What is the use of temperature and media?

  • EPDM       -46℃ – 135℃          Anti-aging
  • NBR           -23℃-93℃             Oil Resistant
  • PTFE        -20℃-180℃            Anti-corrosion and chemical media
  • VITON      -23℃ – 200℃          Anti-corrosion, high temperature resistance
  • Silica         -55℃ -180 ℃         High temperature resistance
  • NR            -20℃ – 85℃           High elasticity
  • CR            -29℃ – 99℃           Wear-resistant, anti-aging

Rubber valve seats are crucial for low-pressure soft-sealing butterfly valves. Zfa Valve has rubber factories with more than 20 years of cooperation, which have mature vulcanization processes, and fully automatic vulcanization equipment. So we can control the quality of rubber from the source and promises to ensure No recycled rubber is used, thus ensuring the stability and high quality of the valve seat.

ZFA Valve, in the process of more than twenty years of production, has developed soft seat molds for Wafer butterfly valves, Lug butterfly valves and Flange butterfly valves, which solves the problems of customers in practical applications, and at the same time, it also makes the valve body of butterfly valves can be recycled for many times, saves the cost of customers finally.