HSHLV-D agitator seal for sensible reaction processes

Sealing solution for a polymer dispersion plant

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Situation

Several top-driven stirred tank reactors, which are run discontinuously in batch operation

Challenge

High pressures and temperatures; a standstill of the stirred tank reactor during the chemical process has to be avoided at all costs

Solution

HSHLV-D agitator seals to seal the stirred tank reactor, and mechanical seals Typ M481 in the reactors storage tanks 

In a production facility for aqueous polymer dispersions, several stirred tank reactors are run discontinuously in batch operation. This means that the tank is filled at the beginning of the process and then set to the required operating conditions. Diverse monomers and water are used as raw materials. Through polymerization they react to form polymers which at the end of the reaction exist in aqueous solution as a dispersion.

The agitator is not allowed to stop while the reaction is in progress as this could result in a runaway reaction, i.e. overheating and even uncontrolled release of chemicals. Thus, the agitator seal must be especially reliable and have considerably higher lifetimes. The second factor to be considered are pressures up to 100 bar that have to be handeled by the implemented seal.

  • Seal: HSHLV-D/160-E5
  • Materials: AQ22M1/V5/M5GE (1.4571) – AQ22V/V5GE (1.4122)
  • Seal type: Agitator with top drive
  • Supply system: Closed system (loop) with WED 3160/A001-A1 heat exchanger and SPN 150/L003-D1 refill unit; each seal can be operated separately and in de pen dently of the others
  • Barrier medium: Synthetic oil according to ISO VG 10
  • Barrier pressure: 120 barg
  • Operation mode: A barrier medium circulating rate of >1 m3/h is required to ensure that the seal is fully functional. This value was determined in practical trials. At lower circulating rates, overheating causes damage to the sliding faces.

The first stirred tank reactors, in use since the early 80’s, were originally fitted with other seal types from a competitor. Already in the 80’s these were converted to EagleBurgmann seals, which lead to a significant increase of the lifetime. By further optimization regarding construction details and material selection the lifetime could be further increased. To keep the level of the best available technology a new seal type, the HSHLV-D was tested. With it an average MTBF of 2 to 3 years was achieved. One seal set a new lifetime record of more than 4 years.

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  • A self-closing double seal of cartridge design with integrated bearing
  • A concave support ring (Item 10) is recommended at pressures beyond 50 bar and is essential at pressures beyond 80 bar; a deformation of the O-ring and subsequent damage to the PTFE coverings are thus prevented
  • In the extremely rare case that the O-rings in the shaft sleeve (Item 19 and 20) fail, an emergency seal takes over the sealing of the reactor. The reaction cycle can thus be ended in normal manner without loss of a product batch
  • An integrated cooling flange prevents the seal from overheating, thus extending its service life. The cooling flange is considered to be a part of the tank; hence to comply with the regulations for pressure vessels it is TÜV-tested separately
  • Any leakage can be selectively removed by way of a drainage facility
  • Assembly rolls make it easier to install and dismantle the mechanical seal.
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HSHLV-D agitator seal for sensible reaction processes

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