Gland Packing

To prevent costly leakage from your pumping systems, gland packing is a cost efficient way of creating a barrier or seal to minimise fluid loss. Here at Cromwell, we have a wide range of gland packing from leading brand Vulcan Seals.

What is gland packing?

Gland packing - also known as compression packing or valve stem packing - is the name given to a type of compression packing which is designed to provide an extra seal on pumps, valves in high pressure environments where extra support is needed. Gland packing is manufactured from a braided rope like material with strands twined together to provide a seal to stop pumps from leaking and to prevent excess fluid loss.

When is gland packing used?

Used as additional support on top of other types of seals, gland packing is commonly used in the plumbing, manufacturing or automotive industry to prevent leakage from the shaft of water pumps. Generally, gland packing is used on centrifugal pumps where a rotating shaft needs to enter the 'wet' area of the pump without the loss of pressurised fluid in excess. Whilst mechanical seals can also be used to perform the same task, gland packing is often preferred due to its cheap upfront cost, ease of installation and replacement as and when needed and can be adjusted whilst the pump is in service to avoid costly and time-consuming shutdowns of equipment. However, it's important for gland packing to be kept cool and it is not suitable for use with abrasive fluids, as this can cause the packing to wear down and require frequent replacement or maintenance.

Considerations when choosing gland packing

Operating temperature suitability - Depending on the temperature of your fluid, you will need to ensure that your chosen gland packing can withstand your desired temperatures. Gland packing, unlike mechanical seals, must be kept cool to avoid breaking or failing to properly create a barrier to stop the loss of leaking fluids, so its vital that yo select a product than can work in your required temperature range.

Roll length - Gland packing is usually supplied on rolls of 8 metre lengths, however larger rolls can be purchased if necessary. It's best to estimate how much gland packing you will need before purchasing to ensure the roll you buy is long enough to cover all areas of your pumps.

Pressure rating - Usually measured in 'bar', different gland packing is built to withstand various pressures within the pumping system. Select the gland packing that is designed specifically for use with the pressure rating that best suits your application to ensure optimum working levels.

pH range - To ensure that your gland packing seal doesn't become less effective due to chemical wearing, it's vital that you select a gland packing that won't degrade or corrode away if exposed to a chemical with a pH level that it isn't designed for. This is measured between 0-14, with 0 being extremely acidic and 14 having a high alkalinity. Neutral is classed as 7.

Gland packing jargon buster

We want to make it easy for you to shop our range of gland packing, so here are some key terms that will help you understand our array of products in this range and their applications a little better.

What does pH and the pH scale mean?

The pH scale - with pH standing for "Potential of Hydrogen" - is a chemical scale used to assess the acidity or alkalinity - often called basicity - of a liquid. The basic scale runs from 0-14, with the lower numbers denoting that a liquid has a higher acid concentration and the higher number showing a liquid's alkalinity. The number 7 on the scale deems a liquid as neutral, or equal in balance between acidity and alkalinity. This is usually what we'd expect to find as the pH of pure water, for example.

So why is this important when selecting gland packing?

Depending on what fluid - and the pH of that fluid - flows through your pumping system, it's important to select gland packing that is suited to withstand it. For example, if you know the fluid that flows through your pumping system is acidic, to prevent the gland packing from wearing out and requiring replacement or maintenance, you need to choose a product which has a suitable pH range. Some gland packing possesses a pH suitability of 0-14 or 1-14, which means they can withstand both acidity and alkalinity, but it is best to check before purchasing.


Is gland packing a mechanical seal?

No. A mechanical seal is a more robust and durable solution than gland packing, performing the same function. The seal possesses three sealing points; one rotary, one stationary and one spring loaded vertical bearing. They are a more permanent solution to leaking fluid, but are generally more expensive, rely on constant external or internal lubrication to function correctly and unlike gland packing, they cannot be adjusted whilst the pump is in service which can cause costly interruptions to your work.