Technofast Industries says its new EziTite TR High Temperature Hydraulic Nuts demonstrated their performance when they were used to assemble boiler feed pumps at an electricity generating plant in South Korea.

The application involved the use of 12 large EziTite TR High Temperature Hydraulic Nuts fitted to M110 X 4.0 studs.

The temperature resistant fasteners were used to replace the former method employing large torque wrenches weighing more than 125kg.

The Technofast method resulted in an installation time of around 30 minutes using two people, compared with eight hours and four personnel using the previous method.

Technofast founder and managing director John Bucknell said these results showed that using the EziTite fasteners instead of conventional methods involving sledgehammers, stud heaters and multi-jackbolt tensioners lead to time savings.

“Large nuts of this diameter can require terrific torque forces to achieve the desired tensioning, or require jacknuts which have multiple forcing screws to bring the job within the power range of hand tools,” Bucknell said.

“Given the damage which can occur to the fastener components and joint faces, some operators have opted to use these jacknut fasteners.

“However, large nuts such as those used on the Boiler Feed Pump can easily have 24 of these forcing screws per nut, and they have to be progressively and sequentially tightened to a specific torque at each step, or the individual screws will be overstressed and fail.

“This can add days of downtime to a typical maintenance operation.

“Also, when jacknut fasteners need to removed, the forcing screws have to be backed off in a strict sequence to avoid failure. If not, then excessive load will transfer to remaining screws and cause failures. The jacknut assembly will then need to be cut off.”

EziTite Hydraulic Nuts, by contrast, tension the bolt in one simple operation, and are rapidly applied by being screwed by hand onto bolt studs, hydraulically actuated to stretch the bolt to the precise tension required, then secured in place mechanically with an integral mechanical lock ring.

The charging pressure is relieved, and the EziTite Hydraulic Nuts remain in situ at the precise target bolt load.

The reverse procedure permits equally rapid disassembly when it is eventually required. All studs can be tensioned or de-tensioned simultaneously by manifolding them to a single hydraulic source.

The EziTite Hydraulic Nuts used in the Korean application also overcame multiple issues experienced with the former method involving heavy torque wrenches, including:

• Horizontal stud position, which made handling difficult;
• Torque damage to studs, hex nuts and sump surfaces;
• Irregular torque readings that were difficult to relate to tensions applied (a result which can be caused by common issues such as corrosion, thread damage and other factors where multiple tensioning is involved).