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The Fluid Systems Engineering and Management Blog

by Swagelok Northern California

Mechanical Seal Support Failure Causes—And What You Can Do About Them

by Paul Lesnau, on 10/20/20 8:45 AM

Swagelok mechanical seal support

One of your guys found a leak. Whether it was a whiff in the air or a puddle on the ground, this is not good news—especially in the highly-regulated Northern California Bay Area. If you’re lucky, the leakage is small, though noticeable, and you can remedy it before it brings a critical pumping process to a halt. In the worst case, it’s catastrophic, with ramifications of sanctions from Cal/OSHA or the BAAQMD. What can you do to prevent these situations? After all, aren’t seal support systems supposed to enhance pump reliability?

I’ve worked to prevent mechanical seal support failure causes with process and reliability engineers for many years and it usually comes down to one of two major factors: changes in process conditions and the inability to maintain the required seal chamber temperature. Let’s look at each of these, acknowledging that there’s often interplay among the variety of seal support systems, mechanical seals, and pumping processes involved.

2 Major Causes of Mechanical Seal Support Failure

Have Pumping Process Conditions Changed Significantly?

It’s not unusual for pumping process conditions to change during the course of a pump’s life. Pumps installed years ago were likely designed for a specific purpose. In the ensuing years, with changes to accommodate a demand for product variations or attempts to boost process productivity or efficiency, mechanical seals and seal support systems may no longer be able to adequately support the pump. I’ve listed key factors to consider in the table below.

Mechanical Seal Support Failure Causes Attributable to Process Changes

Factor Remedy
Change to process fluid running at higher temperatures
  • Replace mechanical seal with one designed to tolerate high-temperature conditions.
  • Enhance the cooling capacity of the seal support system (heat exchanger addition or upgrade).
Increased particulates in process fluid abrade seal faces
  • Seal faces with greater durability in dirty or contaminated process fluids.
  • Add strainer or cyclone separator to remove particulates from process fluid (API Plans 12, 22, 31, and 41).
  • Increase barrier fluid pressure to keep particulates from infiltrating inboard seal faces (API Plans 53 (A, B, and C), 54, and 74).
Increased or decreased pumping pressure
  • Adjust the pressure of the process, barrier, or buffer fluid accordingly (API process-side and dual seal plans).
  • Pressure increases may require changing to different mechanical seal design.

 

Seal Support Failure

As you might expect, pumps, mechanical seals, and seal support systems need to be carefully matched to avoid mechanical seal support failure. Changes in process conditions can quickly upset the balance required to ensure pump reliability.

Maintaining the Proper Seal Chamber Temperature Is Critical

Excessive seal chamber temperatures are virtually guaranteed to result in mechanical seal failures that lead to leakage. I’ve addressed temperature factors associated with changes to process conditions above. Now let’s focus on problems tied to a mechanical seal support system’s failure to maintain the proper seal chamber temperature. In these scenarios, there have been no changes to the process fluid. The problem lies within the seal support system. Here are the most common problems to consider: 

Mechanical Seal Support Failure Causes Attributable to Temperature and Flow

Factor Remedy
Current cooling capacity of the process fluid is inadequate
  • Scale or mineral build-up on heat exchanger coils are diminishing the cooling capacity. If the current heat exchanger is difficult to access or maintain, consider replacing it with one that is more accessible and easily maintained.
  • Add or increase cooling capacity with a new or upgraded heat exchanger. 
  • Check for the proper flow of water circulating through the heat exchanger. Has the supply mistakenly been reduced or shut off as a result of upstream maintenance?
Inadequate barrier or buffer fluid flow rate
  • Dual seal systems require a pumping ring to circulate the barrier fluid through the seal chamber. Ensure the pumping ring is properly installed and not damaged.
  • For barrier or buffer fluid pressurized by external systems (API Plans 54 and 55), ensure that the pump is operating properly.
Coking, icing, or oxidation on the atmospheric side of seal faces
  • Install API Plan 51 or API Plan 62 to prevent these problems.
  • If plans are already installed, check plant water, steam, or nitrogen supply lines for scale or minerals, or inadvertent reduction or shut off as a result of upstream maintenance.

 

For any of these systems, pinched, crimped, or leaking tubing that conveys cooling fluid can also be the culprit. Temperature and flow are closely related. It can be difficult to determine if a mechanical seal support failure cause is one or both of these factors. Begin by identifying or ruling out the simplest problems to fix. In the simplest case, it’s merely a control adjustment to an external source to restore the proper flow of cooling fluid. In more complicated cases, a design improvement may be the only way to eliminate a continually recurring problem.

Don’t Try to Figure Out Mechanical Seal Support Failure Causes On Your Own

Although a few of these mechanical seal support failure causes can be quickly diagnosed and resolved, solving the more complex problems requires the expertise and experience of a seal support system vendor with deep industry knowledge.

A local partner like Swagelok will help you diagnose your mechanical seal support failure causes, on-site. Whether the recommendation is as simple as a heat exchanger upgrade or a redesign and replacement of an outdated seal support system, you’ll benefit from the expertise of a team of field engineers and technicians certified in ISO 9001. There’s no better partner in Northern California to provide you with a full range of services, including consulting, design, fabrication, testing, training, and on-going technical support.

To find out more about how Swagelok Northern California can help you diagnose and solve the most common mechanical seal support failure causes by providing expert consultation and Assembly Services, contact our team today by calling 510-933-6200.


Paul LesnauAbout Paul Lesnau | Sales Manager, Business Development Manager, and Field Engineer

Paul holds a B.S. in Mechanical Engineering from North Dakota State University. Before joining Swagelok Northern California, he was the West Coast Regional Sales Manager for an organization focused within the pneumatic and hydraulic industry where he supervised product distribution throughout the western United States, Canada, and Mexico. While in this role, he was able to help provide technical and application-specific expertise to customers and distribution to drive specifications.

Topics:Assembly ServicesMission CriticalSeal Support Systems

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