Thanks to Swagelok and API, Seals Can Stay Healthier
by Jeff Hopkins, on 12/14/18 8:45 PM
With our mechanical seal support systems you'll extend useful life and keep costs down
"Pump shaft seals cost thousands of dollars, and a refinery might have 1,000 of them or more. Do the math, and you can see why it's important to keep the seals in good condition."
Seals, Seals, Seals
Pump shaft seals cost thousands of dollars, and a refinery might have 1,000 of them or more. Do the math, and you can see why it's important to keep the seals in good condition. Then consider other mechanical seals you may have in mixers or compressors, whether they are driven by electric, steam, hydraulic, or compressed gas motors.
If mechanical seals are your responsibility, you probably have already run a process hazard analysis, either formally or in your head: What happens if equipment fails? What are the consequences of a leak, spill, fire or explosion? What are the likely methods of failure? (If something leaks on a hot motor, for instance, it might start a fire.)
An ounce of prevention
Keeping everything running smoothly is a hard job, involving lots of in-the-field engineering. We want to help make it easier with Swagelok Northern California's mechanical seal support systems. They are fully assembled or kitted to meet your specific needs, and we can configure them for process side, atmospheric side, and between seal plans. These systems can offer a reliable and high performance solution to your mechanical seal operations.
Swagelok Mechanical Seal Support Systems
According to the plan
The American Petroleum Institute has a set of recommendations that applies to mechanical seals for rotating equipment. These API 682 guidelines are considered a standard for best practices.
Take, for instance, API 682 Single Seal Flush Plans. A flush plan is an arrangement that circulates fluid to or from the seal chamber, typically by means of tubing equipment and fluid treatment devices. The goal is to maintain proper lubrication, pressure, temperature, and solids management, and thus prolong the life of the seal.
The fluid can either be from the process itself or from an external source. Typically, the simpler the process is, the simpler the flush plan can be. So when the pumped fluid is clean, does not exceed the temperature limits of the seal, and is compatible with the seal components, you can use a method called a bypass flush. A bypass flush provides circulation flow past the seal faces to carry away seal generated heat. The seal operating temperature will stabilize at the temperature of the pumped fluid.
Normally, this consists of a piping run from the pump discharge to the flush connection on the seal gland, providing flow from the pump, past the seal, and back into the pump through the seal chamber throat. Or it can be piped from the flush connection on the seal gland back to the pump suction, sending the flow in the opposite direction.
Simple plans can use the suction or discharge pressure of the pump to move fluid across the seal faces.
But let's say you want to isolate the seal from the pumped fluid. Then you can use the external flush method. An external flush consists of a minimal flow of a clean, relatively cool liquid (usually water) from an external source injected into the seal gland flush connection at a pressure higher than the pump seal chamber pressure. The external flushing liquid flows past the seal and into the pump, mixing with the pumped fluid.
A control valve, gauge, and flow meter should be installed in the flushing liquid supply line to provide the control functions needed to set and monitor the flushing liquid supply.
When you have specialized fluids that mustn't leak to the atmosphere or will not permit dilution with seal water, a double mechanical seal will be required. In these cases, the flush plan will act as a miniature loop of barrier or buffer fluid.
Guided by API 682 : Pumps - Shaft Sealing Systems for Centrifugal and Rotary Pumps, we have created standard kits and assemblies that can be tailored to your facility. We can start helping you work on a health plan for all the mechanical seals at your site. Learn more about Swagelok Mechanical Seal Support Systems and/or get in touch with us through our Swagelok Mechanical Seal Support Systems webpage >>
API 682 Design Optimization in Action (Video)
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