Systems

Dual acting systems – a significant asset to the ACUTENSION product offering – feature two hydraulic flow lines between the hydraulic source (pump) and the tooling (bolt tensioners).

One of these flow lines is a higher pressure ‘advance’ line, the second is a lower pressure ‘retract’ flow line.

Within a dual acting system the tooling is operated and actuated via oil flowing down the advance line, which simultaneously displaces oil flowing back to the pump tank via the retract line, at low pressure [1].

Once the tensioning operating is complete [2], in a dual acting system the pump will then send oil back to the tools via the retract line, which simultaneously displaces oil from the advance chamber, which subsequently flows back to the pump tank via the advance line at low pressure [3]. This allows for the tools to be reset hydraulically, rather than via operator effort or utilising spring retraction.

Dual acting systems have conventionally been more common in the field of hydraulic torque, rather than bolt tensioning, due to the lower operating pressures required (typically 700 bar, 10,000 psi). This is owing largely to the availability of dual acting pumps working at this pressure, as well as the nature of torque-wrench mechanics.

Up until now, hydraulic retraction at higher pressures in bolt tension has largely been overlooked by tension OEMs, however it has always had inherent advantages to lend to bolt tensioning. This is precisely why ACUTENSION have sought to exploit the benefits of dual acting systems – utilising state-of-the-materials science and drawing upon our extensive engineering expertise – resulting in several optimised tensioner ranges, for various industries.

ACURA^™, ACURA-SUB^™, ACU-BREEZE^™ and ACU-HERO^™ are the patented dual acting systems manufactured only by ACUTENSION, each of which offer both significant safety and time-saving benefits.

Single acting systems are prevalent due to their widespread use in tensioning applications to-date, therefore some users may opt to continue in the practice of single acting tensioning systems, to maintain/harmonise methodology and compatibility.

However, specifying a dual acting system is typically much faster than using a single acting system.

In a dual acting system, power hydraulics are utilised to reset the tensioner pistons, which permits far greater speed and efficiency of operations. The reason for this is that the use of power hydraulics is by far the fastest method for resetting bolt tensioners. In fact it is greatly faster than using either manual retract (operator effort) or spring retract tensioners.

In fact, a testimony of ACUTENSION clientele states: ‘why have we been doing all of this work all of these years?’.

Manually retracting single acting tensioner pistons can be a cumbersome and difficult task for operators, particularly where larger tensioners are required and therefore specified. Seal friction and oil volume play a massive part, and ACUTENSION engineers recognised this from very early on.

Therefore, employing a dual acting system – taking advantage of the power hydraulics readily available – completely removes the burden of having to reset the tensioners; which is time-consuming work. Especially when several tensioners are used together at once. Whilst spring retraction does alleviate this burden somewhat, spring retract tensioners are much larger and heavier than manual retract tensioners; so there is always additional effort wherever a single acting system is specified. Furthermore, many spring retract tensioner offerings are merely ‘spring assist’ rather than actual spring retract per se, and many cannot even fully return all of the oil where several tensioners are interconnected together (it is not uncommon to witness incomplete retraction of spring retract tools furthest from the hydraulic source in this scenario).

And where a particularly large oil displacement is required – the subsea market being a prime example (whereby the tools are operated at a considerable distance from the pump) – spring retraction methods are in fact not possible at all.

In conclusion?

Dual acting systems offer a far faster, efficient and more universal solution to hydraulic bolt tensioning operations; and this is purely down to speed. ACUTENSION’s unique and patented designs permit massively accelerated operating times, and ensure that operators can work both faster and smarter, with duration between tensioning passes greatly reduced and with no need to manually (neither fully nor partially) retract tensioner pistons between sequences. In essence, ACUTENSION’s product offering seeks to maximise the benefit of power hydraulics throughout the full tensioning cycle, rather than confining hydraulics solely to the advance part.

Furthermore, ACUTENSION’s ACU-HERO^™ range of hydraulic pumps will work as either dual or single acting system feeds, meaning an investment in ACUTENSION equipment does not render older equipment obsolete. They also guarantee that as bolting systems continue to increase in size – in order to match ever-increasing downstream process demand (an example in recent years being the pace/size of wind turbine evolution) – customer capability and speed of operation is assured, because dual acting tensioners are particularly much lighter and easier to handle compared to single acting systems for larger tensioner sizes.

All-in-all, thanks to ACU-HERO^™ series pumps and our associated ACU-BREEZE^™ and ACURA^™ bolt tensioner ranges, dual acting systems are the best way to ‘future proof’ your bolt tensioner capability; be it for rental and service contractors, or OEMs and EPCs alike.

ACUTENSION possess vast experience in the design, specification and supply of bespoke or hybrid tensioning systems, no matter your industry. Despite our array of world-class single and dual acting standard product ranges, our engineers possess unmatched experience in the design of ‘application specific’ (ETO) solutions, no matter the challenge nor industry.

In fact, such is our capability in the design of customised bolt tensioner solutions, ACUTENSION has to-date supplied almost as many special tensioners as it has standard units!

Applications typically vary, and quite often a unique or exacting challenge requires an equally specialised solution. Unlike many of our peers, if a standard solution or system cannot satisfy the need or happens to be incompatible somehow (insufficient load, fit issues, inefficiency or safety concerns being a few examples of how this might be), ACUTENSION will most likely have met this challenge before, and can almost always engineer a solution.

Please contact us to learn more about how ACUTENSION can tailor our design approach to solve any unique or specific challenge.