The pump that is cool under pressure

29.10.2001

Sterling Fluid Systems has extended its range of high-temperature pumps with the introduction of the new ZDNA and ZHNA models designed for hot water pumping applications.

Both new pumps have been developed to offer users a cost-effective alternative to the existing high-performance ZEN range, yet with the same cost and operational benefits.

The ZDNA long-coupled pump is suitable for hot water up to 185 °C, it has a single, uncooled mechanical seal and a casing pressure of up to 25 bar, making it suitable for applications where the ZENC 40 bar pump (which is suitable for hot water up to 230 °C) is not required.

Unlike conventional hot water pumps, the ZDNA (like the ZENC) has its mechanical seal placed at the ‘cold end’ or drive end of the pump and uses a double heat barrier to achieve the required reduction in temperature at the drive end of the shaft. As a result the use of an uncooled echanical seal does not cause problems as the temperature will not exceed 100 °C in the seal area.

This avoids the typical problems of uncooled shaft seals such as high thermal stresses, friction and deformation of seal surfaces which can lead to a short service life and low cost benefit.

To extend the life of the seal, all Sterling’s hot water pumps are fitted with a gas separator in the mechanical seal chamber - this prevents gas bubbles from collecting around the seal faces and causing failure.

The new ZHNA long-coupled pump is also suitable for hot water up to 180 °C and has a single uncooled mechanical seal casing pressure up to 16 bar. For hot oil pumping pplications, Sterling’s ZTN range of long-coupled centrifugal pumps and ZTK close-coupled and close-coupled in-line pumps have been developed to handle thermal oil up to 350 °C with an uncooled seal. Their ability to safely handle high-temperature oils allows customers to meet increasingly stringent health and safety requirements as well as reducing running costs.

Heat losses are reduced by a heat barrier which is installed behind the hydraulics, while the pump is also fitted with a thermally isolated bearing carrier. These design features, together with an additional throttling bush achieve the required reduction in temperature in the shaft seal area, allowing the use of single, uncooled shaft seals.

A further benefit of these pumps is that, as long as the suction pressure is below 5 bar, seal rings can be used rather than a mechanical seal to reduce the cost of spares. In addition, as there are a number of seal rings arranged in series, should one of the seal rings fail, the other seal rings will contain the leak. This means that leakage from the pumps will be slow and gradual, allowing the pump to remain in service while new seal rings are ordered.

For pumping thermal oil up to 400 °C, the ZTKA magnetic drive pump has a design with a heat barrier where a ‘dead ended’ magnetic chamber is used - the heat barrier separates the pump thermally from the magnetic coupling and prevents heat flow into the magnetic chamber.

About Sterling Fluid Systems

Sterling Fluid Systems is a global engineering group operating in the field of fluid and gas handling.

It's five specialised business groups include, Liquid Pumps, Vacuum Process Pumps, Filling & Testing Systems, Water Treatment Systems and Engineered Valves.

Focused on market requirements,these businesses serve industry by delivering engineered solutions. Sterling Fluid Systems has a group turnover in excess of $450 million with more than 2800 employees designing, manufacturing, marketing and developing new systems and processes.

The organisation benefits from it's affiliation with it's parent company Thyssen Bornermisza Group (TBG) which has annual sales of more than US$ 2 billion.

The Sterling Fluid Systems Group has more than 50 fully owned operations around the world established in Europe, The Middle East, North and South America, Africa and Asia. An additional network of distributors and agents ensures the support of business at a "local level".

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