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Monday, October 5, 2009

Gland Plate Construction

An essential component of any installation is the gland plate. The purpose of this part is to hold either the mating ring assembly or the seal head assembly, depending on whether the seal head is rotating with the shaft or stationary to the pump casing. It is also a pressure containing component of the installation. The aligment of one of the sealing surfaces, particularly the mating ring used with a rotating seal assembly and a gland plate bushing, is dependent on the lift of the gland plate to the pump. To ensure the proper installation, the API specification requires a register fit with the inside or outside diameter of the seal chamber. The static seal on the face of the seal chamber must be completely confined. Three basic gland plate are:
  1. A plain gland plate is used where seal cooling is provided internally through the pump stuffing box and where the liquid to be sealed is not considered hazardous to the plant environment and will not crystalline or carbonize at the atmospheric side of the seal.
  2. A flush gland plate is used where internal cooling is not available. Here coolant (liquid sealed or liquid from an external source) is directed to the seal faces where the seal heat is generated.
  3. A flush and quench gland plate is required on those application that need direct cooling as well as a quench fluid at the atmospheric side of the seal. The purpose of the quench fluid, which may be a liquid, gas or steam, is to prevent the build up of any carbonized or crystalized material along the shaft. When properly applied, a seal quench can increase the life of a seal installation by eliminating the loss of seal flexibility due to hangup. The gland plate can also be used for flush, vent, and drain where seal leakage needs to be controlled. Flammable vapor leaking from the seal can be vented to a flare and burned off, while nonflammable liquid leakage can be directed to a seal sump.