Gland Seal Water Explained
Clean and reliable gland water supply is a critical utility in any oil sands mining facility. Pressurized gland water is pumped into the seals of slurry pumps in order to keep them clear of bitumen, sand and fines. This gland seal water serves three important functions:
- it enables the pump shaft to rotate within its sleeve with minimum friction,
- it prevents the slurry from back-flowing into the seals and damaging the shaft, and
- it allows for a small amount of cooling of the pump shaft, which heats up as it rotates at high speeds.
Maintaining sufficient gland water flow and pressure is critical to the proper operation of any slurry pumping system. Operating without gland water, even for only a few seconds, will cause the slurry to back-flow into the pump’s sleeve and damage the rotating pump shaft. Worn seal packing is far easier to repair than a damaged slurry pump.
The most important factor in designing a gland water system is to ensure the system is reliable and has sufficient pressure. If gland water pressure is too low, it will not be able to overcome back-pressure from the pump and cause the slurry to back-flow into the sleeve. However, excessively high gland water pressure is also not recommended since this will also reduce the life of the packing.
The amount of gland water required depends mostly on pump design and how worn the packing is. A new packing will take less gland water. Water requirements will slowly increase as the packing gets worn out and eventually needs to be replaced. Normal gland water flow rates for slurry pumps can be as low as 5 m³/hr to as much as 25 m³/hr if the pump packing is really worn-out.
Ideally, gland seal water is sourced from a clean, cool water supply, such as filtered river water. However, since clean water is such a precious commodity in the oil sands, many operators use water recycled from the tailings pond. Any reliable water source is suitable, however, operators should note that dirty water will obviously deteriorate the packing more quickly. Slurry pump manufacturers have also been working towards optimizing the design of their pump seals in order to reduce gland water consumption rates.