A pump seal is the determining factor between pump failure and success. Although seals are relatively small-sized components of pumping equipment, an incorrect or poor quality seal can wreak havoc on a slurry pumping project. A leaking pump is the worst case scenario, however an incorrect or poor quality seal could cause more damage than you might think throughout the lifecycle of the pump.
By following best practises when sealing your pump, you can significantly reduce lifecycle costs and minimise hassle. This approach takes equipment design, seal lifecycles, slurry characteristics and budget into consideration, providing you with the very best solution to your pumping application.
Increased reliability as well as the reduction or elimination of flush water are the main considerations when selecting the most cost effective and durable solution for your slurry pump seal.
For best practices in mechanical seals for slurry applications, the following factors of the seal should be considered:
- A robust design with a stationary spring design
- Seal face geometry that is hydraulically balanced
- Springs located outside of the slurry
By choosing a mechanical seal design that places the springs entirely outside of the seal, the seal will be able to deliver the required closing force to keep the faces tracking properly. Springs that are correctly balanced should compensate for mechanical misalignments, as well as keeping a consistent load on the seal faces.
Split mechanical seals are also useful in slurry applications. Split seals minimise installation complications as they can be installed without needing to disassemble the equipment. If a positive impact on labour hours and downtime can be achieved overall, a split seal will provide a suitable and hard-wearing option.
In non-settling slurry or dewatering applications, heat can build up around the seal faces. This can affect the properties of the o-ring and limit its overall performance.
To combat this, Chesterton mechanical seal designs involve micro polishing the sealing surfaces, which enables the o-ring to move and flex. This is unique to the Chesterton range, and increases the o-ring’s ability to seal.
High solid content is often present within heavy slurry. Because of this, it is important to choose a seal that can withstand such impacts. A seal face that is covered in metal shrouds for protection is the best option for these types of projects.
By adopting best available practices in either controlling flush or eliminating flush by the use of environmental controls, it is possible to save both time and money.
Enviroseal SpiralTrac environmental controllers have revolutionised the sealing environment in stuffing boxes. They are used with Chesterton mechanical seals and packing to reduce the flush fluid required and further enhance seal reliability by driving seal cavity circulation and solids removal.
Mechanical packing is also widely used in slurry pumping applications – most often when mechanical seals are not an option due to budget constraints or operation factors. In the past, mechanical packing was the seal of choice for slurry sealing. The high tensile materials used in the manufacture of some slurry packing (despite being able to withstand harsh abrasion) gave off a less than desirable amount of heat. This heat, if not cooled by large amounts of flush water, would result in wear of the seal. Wear and excessive water both contribute to excessive life cycle costs of slurry pumping.
However, advancements in packing materials such as the use of carbon and high purity graphite have led to a reduction in the amount of flush water required, and significantly reduce wear on dynamic surfaces.
Chesterton Seals provide two main products for slurry sealing, including a reinforced graphite product called GrafMax and the advanced expanded graphite/PTFE 1830 SSP packing.
Developed to handle high-speed and high-temperature rotating equipment applications. The reinforced graphite construction, self-lubricating and heat-dissipation properties make GraphMax an outstanding performer in slurry sealing programs.
This packing is also designed for use in valve applications including steam valves. GraphMax is a solution for plant-wide standardisation programs, reducing flush, and effectively eliminating leakage in pumps and valves.
This packing was also developed to meet the requirements of slurry applications. This low-friction, non-abrasive packing reduces heat generation and shaft or sleeve wear. Structural carbon is integrated into the design of this advanced expanded graphite PTFE packing, resulting in a more resilient packing. The unique hybrid material and construction result in low leakage and long life.
Each of these packings are easily removable during repack and are able to meet rigid demands of slurry sealing applications. The packing is low in friction, which in turn generates minimal heat and greatly reduces flush, resulting in a low leakage profile and a long equipment life.
Flushless slurry seals
When flush is not available, heavy-duty flushless slurry seals are also an option for slurry applications. The Chesterton Slurry 170 Single Cartridge seal is a unique product able to withstand harsh slurry environments without the need for external flushes in slurries that consist of up to 40 per cent solids in suspension. Their non-clogging, robust design has ease of installation and is easy to maintain throughout its lifecycle.
The Chesterton Slurry Program
According to Jason Lynch, Director at FITT Resources, the Chesterton Seal Slurry Program is a useful tool to help you choose the correct seal for your slurry pump.
“Through the program, Chesterton’s engineering team help solve problems that impact production and maintenance, and bring solutions from comparable situations.
“By using the best practices approach, Chesterton can help users reach their productivity targets by reducing maintenance costs on targeted rotating equipment.
“The solution might be looking to standardise their plant, reduce their need for flush water, or gaining an increase in mean time between failure of equipment,” said Mr Lynch.
“We aren’t biased towards mechanical seals or packing, and we have put as much research and development into both. As a company, we are not afraid to remove or replace either form of seal to deliver the highest quality and best solution to suit each of our customers.
According to Mr Lynch, Chesterton and FITT’s team of engineers have years of experience in sealing slurry and offer knowledgeable customer support.
“And at FITT Resources, we have the capacity to come and supervise installation, help monitor and measure performance and also help troubleshoot any challenges that customers have.
“It is the business to business contact provided by FITT Resources and Chesterton that our clients find most valuable,” said Mr Lynch.