How do I find the right mechanical seal?

Choosing the right mechanical seal is crucial for the smooth operation of your plant. The reasons for this are obvious. You will benefit from the seal’s long service life and avoid seal-related breakdowns. This reliability reduces downtime, which ultimately saves costs.

When is it necessary to select a new mechanical seal?

Wear and tear, defects, changes in operating conditions and plant modernisation are typical situations that necessitate the selection of a new mechanical seal. Choosing the right mechanical seal is crucial in these situations. This is because the risks associated with an incorrect choice can have serious consequences for the operation of your plant. This can lead to leaks if the seal fails prematurely. Replacing the defective seal leads to higher operating costs. This guide explains how to find the right mechanical seal. 

Are you unsure which mechanical seal should be used in your plant? Contact our team – we’ll provide you with personalised advice! 

Criteria for making the right choice

The mechanical seal must possess certain characteristics in terms of design, elastomers or materials to ensure it is optimally suited to your system. Although it may seem logical to select the appropriate mechanical seal based solely on its size, this is a common mistake when choosing a seal.
To find the right mechanical seal, consider the design and installation space within the system, the operating conditions of your system, and the ambient parameters affecting the seal, as the environment in which the mechanical seal operates has a huge impact on its function and service life.

Selecting the right mechanical seal – an overview of examples:

Mechanical seals

- Seals consisting of rotating and stationary components that are installed together during pump installation.
- Applications: Standard industrial applications, as well as demanding applications
that require a more robust design and can withstand harsh conditions.
- Reduces the ingress of particles into the sealing interface
- Designed for viscous and abrasive fluids
- Industry examples: Wastewater treatment, mining, paper and pulp industry

Cartridge seals

- Pre-assembled units
- Requirements: High reliability and fast turnaround times
- Industry examples: Chemical processing, petrochemical industry

Step-by-step guide to choosing

To help you find the right mechanical seal as effectively as possible, these instructions are based on a step-by-step selection process. To do this, you will need to determine the dimensions in several steps, then identify and record the operating conditions and the properties of the pumped medium

1. Determine the dimensions of the suitable mechanical seal

To determine the size of the mechanical seal, measure the 
- inner diameter of the seal or the shaft diameter 
- outer diameter of the seat in the housing 
- installation length of the seal

Expert tip: You can determine the correct installation length by measuring the seal with a spring compressed by approximately two-thirds. 

2. Type of mechanical seal

Selection criterion: Your application

- Design type: Design with O-ring or bellows and type of spring arrangement, e.g. single spring, group spring, sinusoidal spring, etc.

3. Selecting mechanical seal materials

Selection criteria: Application area and pumped medium

- Materials of the sliding surfaces: Ceramic, carbon, silicon carbide, CrNiMo or tungsten carbide - O-rings and bellows: NBR, EPDM, FKM or special elastomers such as FEP

4. Analysis of operating conditions and medium

Objective: Determine the requirements for the mechanical seal

Application / System type:

- Pump, agitator, etc. 
- Maximum operating pressures and temperatures 
- Speed: High speeds may require special mechanical seals.

Properties of the medium to be pumped:
- Lubricating, corrosive, particulate-laden, requiring special chemical resistance, etc.
- Fluid characteristics: viscosity / abrasiveness, chemical compatibility (to prevent degradation of sealing materials)

Are special applications such as CIP (Cleaning-in-Place) or SIP (Sterilization-in-Place) required?

Environmental factors:
- Standards / regulatory requirements: compliance with regulations and industry standards
- Installation environment: external contaminants / conditions to which the mechanical seal is exposed

Dos and don'ts when selecting a mechanical seal

Rising costs are tempting companies to prioritise price above all else. We do not wish to dismiss this reality. However, we would like to point out that price should not be a deciding factor when selecting the right mechanical seal. When it comes to seals, suitability is the top priority. After all, the mechanical seal must also be leak-tight. However, this is only the case if it meets the requirements of your system 100 per cent. If you compromise on suitability and quality, follow-up costs are inevitable, which will far exceed the purchase price.

Another ‘don’t’ is failing to take the measurements correctly. This is a mistake that unfortunately happens frequently and leads to high follow-up costs. That is why taking precise measurements is an essential ‘do’ when selecting the right mechanical seal.

Our expert tip: To find the right mechanical seal, you should take your time to avoid measurement errors and/or price traps. If you need to act (very) quickly, you should consult a specialist who can support you with their expert knowledge so that you can quickly select the right mechanical seal.

How the right choice affects service life

Choosing the right mechanical seal is not rocket science, but it has a decisive impact on the seal’s service life. We would like to illustrate here, by way of example, what can happen if you do not choose the right mechanical seal:

- If seal components are corroded due to chemical incompatibility, this can also cause damage to the system, shortening its service life.
- If the seal does not fit 100 per cent, the mechanical seal will wear out quickly. This results in leaks. The seal must be replaced.

In short: with the right mechanical seal, you not only increase its service life but also reduce your plant’s downtime.

Do you have any questions about how to find the right mechanical seal?
We’d be happy to help you select the right mechanical seal. Contact our experts:

- by phone: 09090 - 705880
- by email: mail@billi-seals.de
- directly via WhatsApp

Our experts will get back to you straight away.