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Effectively monitoring bladder integrity in accumulators

Supplier: HYDAC International By: Eddie Alves
05 August, 2014

Hydro-pneumatic accumulators are commonly used in industry to improve the performance of hydraulic systems, but can pose a safety risk without proper maintenance.

A revolutionary new device from a leading fluid technology specialist could make it easier to identify issues should they arise.

Hydro-pneumatic accumulators are pressure vessels designed and built to store fluids under pressure. They are charged with nitrogen, which is separated from the fluid section by a piston, bladder or diaphragm.

The principle applications of accumulators are: energy storage, emergency and safety functions, damping and the reduction of vibrations, pulsation damping, shock absorption, suction flow stabilisation, media separation, energy recovery, volume and leakage compensation and weight equalisation.

Using an accumulator improves the performance of the whole hydraulic system, and can give great safety and comfort for operators of machines.

Safety hazards

It is however important to know hydraulic accumulators present an acute safety risk to personnel and equipment if not correctly engineered, applied or maintained, according to HYDAC, a specialist with over 50 years' experience in their development, design and production.

Particularly in a bladder accumulator, the bladder, a crucial component between the gas and the fluid, can be deformed and the effects of temperature and aggressive media on the elastomer material can destroy the bladder.

To date there has been no means of directly monitoring the bladder integrity in individual accumulators, particularly in accumulator stations where testing is very time-consuming and costly.

Effective monitoring with BIS

A new process control device available from HYDAC has been designed to inform you if there is a problem in the bladder. Called Bladder Integrity System (BIS), it consists of a BIS bladder, BIS adapter and electronic components BIS 1000.

The BIS detects fluid which has penetrated the bladder and transmits a signal. A split is therefore detected in the bladder. In addition, the temperature and pressure can be monitored electronically (current loop/HART).

The BIS is available together with a bladder accumulator as initial equipment. A retrofit version is also available, both for HYDAC bladder accumulators and for other brands as well.

There are different types of the BIS that can be chosen to fit your needs, the types are: basic, ATEXia [ATEX (94/9/EC), IECEx], ATEXd [ATEX (94/9/EC), IECEX, cCSAus] and ATEXd+, which comes with junction box in aluminium or stainless steel.

Using a BIS has many advantages. By identifying a defective bladder during operation you can have a planned repair or maintenance interval and reduction in downtime. Also, you can monitor the pressure and temperature of an accumulator during operation.

This system can be used on hydraulic accumulators with emergency functions, such as: mechanical seals, oil and gas, lubrication systems, davits, booster stations, refineries, chemical plants and remotely operated oil fields. It can also be used in accumulator stations on presses, plastic injection moulding machines, steel works and test rigs.