What’s a Flush Plan, And Why Should I Care?

Author: Jorie Ballun | March 8, 2016 | Category: Mechanical Seals

Mechanical SealsJust like you may want a clean desk and a comfy chair, mechanical seals appreciate good working environments too.  The best way to ensure that your mechanical seal is performs at its best, is to select the seal properly and have the appropriate flush plan to support it.

What is a Flush Plan?

A flush plan is a strategic equipment arrangement that circulates fluid to or from the seal chamber in order to maintain proper lubrication, pressure, temperature, and solids management.  The goal is to create an ideal work environment for the seal in order to avoid wear and failures, thus prolonging its useful life. 

There are many types of flush plans that are selected for certain applications, fluids, and seal configurations.  Keep in mind that seals and flush plans are engineered products that require calculated design in their selection, so be sure to talk to an engineer about them!

How Do They Work?

There are some flush plans that use the pump construction geometry to function, but we will be focusing on external flush plans in this post. Flush plans typically depend on redirecting fluid to or from the seal chamber by using tubing equipment and fluid treatment devices.  The fluid can either be from the process itself or from an external source, depending upon what is required for the process.  Typically, the simpler the process is, the simpler the flush plan can be.  Hazardous or dangerous fluids will require more aggressive flush plans to protect the materials and workers from exposure to the product.

Simple plans can use the suction or discharge pressure of the pump to move fluid across the seal faces – these plans will simply have piping with orifices leading from a port to the seal chamber.  Connecting to the discharge port will allow for the high pressure discharge fluid to travel to the seal chamber and re-enter the process.  Connecting to the lower pressure suction port will cause fluid to move from the seal chamber to the suction port to re-enter the process.  Either way, you are providing lubrication and cooling while flushing solids away from the seal so that it can maintain appropriate contact and keep your process inside the pump.

Mechanical Seal Flush PlanSometimes the process fluid needs to be treated before it can re-enter the seal chamber.  Plans in this category pipe the fluid from the pump ports and use external devices, such as heat exchangers or cyclone separators, to cool the fluid down or remove solids before it passes over the seal.

In the tough cases, the process fluid may not be suitable for supporting the seal and an external fluid source will be required.  Many times, cool plant water will do the trick.  This will dilute the process product as seal water is introduced into the system, but many times that is acceptable.

When you have specialized fluids that should not leak to the atmosphere or will not permit dilution with seal water, a double mechanical seal will be required and the flush plan will act as a miniature loop of barrier or buffer fluid.  Barrier fluid is pressurized and keeps the product inside the pump.  Buffer fluid is unpressurized so it collects leaking product and creates a diluted solution.  These plans will be more elaborate with reservoirs and monitors, but they offer the benefit of excellent seal environment control and great protection from exposing the product to the atmosphere.

Why Should You Care?

You spent time and money on the equipment and product, didn’t you?  Incorporating the correct flush plans will help protect the equipment that you have while preventing future issues.  Taking care of your seals with a flush plan will increase their life expectancy and minimize unplanned downtime and expensive repairs.  Also, a well cared for mechanical seal will help reduce leaks and wasted product, keeping you from mopping dollars off of the floor.  Finally, in tough applications, they are absolutely essential for safety reasons.

If you are interested in setting up a flush plan for your mechanical seals, contact us! Our experienced engineers are ready to help you design the perfect plan for your application. 

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Jorie Ballun

Jorie Ballun

Jorie is an Application Engineer at Crane Engineering. She has a passion for creating pumping systems that are effective, efficient, and adhere to customers' goals.

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