Retrofitting mechanical seal support systems in existing pumps 

Improving mechanical seal reliability, reducing unplanned downtime and meeting evolving safety expectations often mean upgrading seals and their support systems long after a pump first enters service. While seals and support systems form part of the original pump selection, real operating conditions frequently reveal gaps in the initial design. What looked sufficient on paper may no longer meet site requirements once process realities, safety standards or performance targets change.  

In many plants, retrofitting becomes essential when: 

Each of these scenarios introduces technical and practical challenges that differ significantly from those encountered when specifying a system for a new installation. As a result, understanding these differences is key to successful retrofitting. 

Why retrofits are more complex than first-time installations 
Upgrading mechanical seals in existing equipment rarely allows engineers to start from a blank design. Instead, teams must work within fixed mechanical layouts and site constraints. Compared with greenfield projects, retrofit solutions often face tighter constraints on what can be physically installed and on how support systems integrate with existing infrastructure. 

Retrofitting typically involves: 

These constraints narrow the range of feasible solutions, even when a more optimal configuration exists in theory.  

This is also where alignment with API 682 becomes especially important. Although new editions primarily apply to new equipment, many operators expect retrofit solutions to follow its requirements wherever possible, including piping plans, instrumentation and support system design. 

Physical space: The first major barrier 
Physical space presents one of the biggest hurdles in retrofit projects. Inside the pump, engineers must confirm that there is sufficient room in the seal chamber and that the axial shaft length is sufficient to accommodate the upgraded seal. Moving from single to dual seals or adding extra ports and features increases seal size. Machining an existing pump to create more internal space is often impractical, leaving seal suppliers constrained by the original pump dimensions.  

Outside the pump, the challenge usually intensifies as upgraded seals require additional support equipment and space that existing installations were never designed to accommodate. 

Upgraded seals often require additional support equipment. This might include extra flush pipework or small components mounted directly on the pump. In many cases, however, full support systems with heat exchangers or vessels require their own stand and baseplate. 

During the original installation, the pump baseplate would have been designed to accommodate both the pump and the support system. For example, adding a Plan 52 or Plan 53B system can nearly double the baseplate width. In retrofit situations, that space no longer exists. The concrete foundation and surrounding area were never designed for these additions, making it difficult to position equipment without obstructing access for operators and maintenance teams.  

Practical layout requirements for retrofit installations include: 

Support system pipework must also follow best practices to avoid issues such as vapour lock and poor circulation. Typical guidance includes: 

The system must be positioned so these routing principles can be applied in practice.  

One favourable option in retrofit scenarios is a Plan 54 system. Because it can sit further away from the pump and supply pressurised barrier fluid to multiple units, a single centrally located system can support several pump upgrades, reducing space demands in congested areas. 

Connections: Accommodating additional interfaces 
Many mechanical seal upgrades introduce new connections for: 

Adding these interfaces may require extending the seal axially, which in turn requires additional shaft space. In some cases, engineers must also drill additional ports into the pump seal chamber to accommodate new piping.  

Each new connection adds complexity to the mechanical design and installation process, reinforcing the need for careful assessment during retrofit planning. 

Utilities: Often the deciding factor 
Utilities are often the primary driver of support system selection. More advanced seals and systems rely on site infrastructure, which may be lacking. If water, power or gas supplies are unavailable, extending utilities requires extra capital investment and may limit upgrade options. 

Typical utility considerations include: 

Instrumentation also plays a growing role. Modern systems often include transmitters with local indicators to support remote monitoring and alarm management, particularly in oil and gas environments. Each instrument adds wiring costs and requires available inputs on the site control system.  

In colder climates or viscous services, heat tracing may be necessary to maintain operating temperatures. This can involve electric tracing or heated fluids routed through pipework. 

Where utilities are limited, specific systems offer advantages. For example, Plan 53B can deliver high-pressure barrier fluid without requiring electrical power or pressurised gas, making it suitable for remote locations where infrastructure upgrades are undesirable. 

Maintenance and training: Managing increased complexity 
Upgrading support systems inevitably increases operational complexity. Maintenance teams must manage more components, instruments and procedures. Commissioning and start-up routines become more involved, often requiring: 

Once in service, upgraded systems introduce ongoing tasks such as: