Choosing Reliable Seal Support System Lubrication Can Help Avoid These Common Alberta Refinery Problems

When mechanical seals fail, it’s usually because the seal support system failed to maintain the proper seal chamber environment. This can happen for a variety of reasons, but one of the most common is inadequate seal support system lubrication.

Seal support system lubrication failures can happen even if there have not been any recent process changes, so it’s essential to monitor the condition of seal support systems and their lubricating media and make changes when needed. This article will examine the consequences of inadequate seal support system lubrication, the lubrication options available, and their advantages and disadvantages.

The Consequences of Inadequate Seal Support System Lubrication

A seal support system must create a seal chamber environment that maintains the integrity of the mechanical seal. To do this, it must be able to deliver the process, barrier, buffer, or flush fluid at the required rate, pressure, and temperature.

Leaks

There are many reasons a mechanical seal can leak. In terms of seal support system lubrication, a leak can occur when high temperatures, corrosion, or abrasive media cause the seal faces to deform or degrade.

If the seal chamber is too hot, thermal expansion can distort the seal faces and alter their parallelism. Precise dimensional control of the seal faces is essential to seal the fluids while still allowing lubrication and rotation. If the faces become deformed even slightly, leak paths can be created.

Some possible lubrication-related problems that can cause elevated temperatures leading to seal face deformation:

• Inefficient cooling resulting from buildup on heat exchanger coils
• Inadequate flow of plant water through cooling coils
• Impeded lubricant flow because of tubing damage, leaking connections, or clogged filters or strainers

Mechanical seal faces can also be damaged if the seal chamber fluids are corrosive or abrasive. Over time, pitting or abrasion can degrade the seal faces and create leak paths. These problems occur when corrosive or abrasive media finds its way to the seal faces, which can be caused by:

• Corrosion in aging piping, seal pots, or cooling coils migrating to the seal chamber
• Inadequate filtering of process fluids

Contamination of Process or Barrier Fluid

One important job of the seal support system is to maintain the required pressure to prevent contamination. Depending on the fluids involved, it may be critical to prevent the lubricating medium from contaminating the process fluid or vice versa. If the necessary seal chamber pressure is not maintained, process or barrier fluids can migrate across the seal faces.

There are a few ways seal support system lubrication can cause pressure changes that can lead to contamination:

• Clogged filters or strainers causing poor flow to the seal chamber
• Pressure drop due to tubing damage, leaking connections, or inadequate seal pot pressurization from plant nitrogen, bladder accumulator, or piston accumulator
• Pressure increase due to excessive seal pot pressurization from plant nitrogen, bladder accumulator, or piston accumulator

Dry Running

A well-lubricated mechanical seal should last for many years. However, when lubrication is inadequate, it can cause dry running, which can be very harmful to mechanical seals.

Dry running can occur when air is trapped in the seal chamber, preventing the lubrication fluid from reaching the seal faces. When this happens, the lack of lubrication can lead to rapid mechanical seal failure.

Some problems that might lead to dry running are:

• Improper venting of air trapped in the seal chamber
• Clogged filters or strainers causing poor flow to the seal chamber

There’s no universal solution to every seal support system lubrication problem. However, many problems can be mitigated or solved by changing the barrier, buffer, or flush fluids—especially when they result from recent process changes. Likewise, when installing a new seal support system, selecting the right lubrication is an essential design decision.

Seal Support System Lubrication Options and Solutions

Seal support system lubrication must be able to maintain a proper seal-shaft interface and transfer heat away from the seal faces. There are two general types of lubricants to choose from:

1. Water/glycol mixtures
2. Oil-based lubricants

The choice between the two is typically based on process temperature: water/glycol mixtures are more effective for low-temperature processes, while high temperatures usually require oils. The differences and the pros and cons of each are shown below.

Pros and Cons of Water/Glycol Mixture Lubricants

Pros and Cons of Oil-Based Lubricants

The specific water/glycol ratios or types of oils can be customized to the process conditions for the most reliable and efficient results. Your mechanical seal support system vendor can provide guidance to help you match the pumping process with the right seal support system and lubrication to optimize reliability.

Questions about Seal Support System Lubrication? Ask the Experts

Inadequate or improper seal support system lubrication can quickly lead to major problems in Alberta refineries. Fortunately, Edmonton Valve & Fitting is here to provide solutions to remedy problems and prevent them from occurring again.

One of our Field Advisors can come to your refinery to perform an onsite evaluation of your seal support systems and recommend the barrier, buffer, or flush fluids that will ensure long-term reliability. We can also recommend components and systems, including seal support systems, that will protect your mechanical seals and help you avoid costly downtime and repairs.