One pump operator recently came to KSB GIW, Inc., with a startling but not unique problem: Slurry was leaking from the back of his stuffing box. We reached out to Technical Services Manager Kenny Meyer about stuffing box malfunctions, some potential consequences, and the measures pump operators can take to prevent and resolve leakage problems.
The problem
There’s slurry coming out of the back of the stuffing box. What could cause this to happen?
Stuffing box leakage can occur because of a variety of factors. First and foremost, the lack of adequate sealing water flow and pressure could be the culprit. If that’s not the case, other factors such as unresolved vibrations can cause gaskets and fasteners to loosen, resulting in leaks. Improper maintenance practices, such as not replacing worn components or having the stuffing box misaligned with the shaft sleeve, can also contribute to leakage. Corrosive sealing water and environments can cause deterioration and subsequent leaks if the stuffing boxes aren’t corrosion-resistant.
What are the consequences of this leakage?
A stuffing box leaking slurry is usually a sign of something more serious. You should give this situation your immediate attention before something catastrophic occurs — such as bearing contamination, shaft damage, or even shaft breakage. You should also consider the safety risks of having slurry (which is often caustic) spraying in an already-dangerous and congested area. And of course there’s the obvious consequences of lost product, especially when you’re pumping rare and precious minerals.
What should operators do if they see slurry coming out of the stuffing box?
The first thing operators should do is check whether there is adequate sealing water flow and pressure. If this is the issue, they should take immediate steps to correct the problem. If there are no issues with the sealing water, then they should perform maintenance on the stuffing box.
The solution
How should operators resolve slurry leakage problems?
Operators should always read their Maintenance Manuals and set up the sealing water systems accordingly. They must provide the recommended supply (flow and pressure) of sealing water to the stuffing boxes and remember to keep their pumps — especially the stuffing boxes — maintained on a regular basis. The addition of a throat bushing stuffing box can also aid in prolonging the life of stuffing box packing and shaft sleeves, as well as reduce sealing water consumption.
A throat bushing is a type of sealing water restriction device that is generally inserted into the bottom of the stuffing box housing. When properly applied, throat bushings can mitigate the migration of slurry between the shaft sleeve and packing, thus reducing component wear and thereby reducing the propensity for leakage.
GIW offers several shaft sealing alternatives to the throat bushing design. Our lowest flow stuffing box offering is the KE design. We also have mechanical seal options, dynamic seals (which are used exclusively on the LCC product line), and the Spiral Tracᵀᴹ Throat Bushing.
Operators should adjust their stuffing boxes periodically, by tightening or loosening the gland, to maintain a sealing water “drip rate” out of the back of the stuffing box. This is normal procedure. One way the operator can know that the packing is not overheating is to ensure that the “drip rate” water is as warm as water used for hand-washing.
What are your tips for pump operators?
Operators can observe the following three simple steps to help avoid slurry leaking from their stuffing boxes:
- Read the Maintenance Manuals and set up the sealing water systems accordingly.
- Monitor and maintain the gland/sealing water drip rate.
- Maintain the pumps regularly, especially the stuffing boxes.