The Solution To Bolting Problems

2,000 Ton Forging Press

Problem: The column nuts on this press had a long history of coming loose. Previously, heating rods were used to obtain 2,000,000 lbs of preload per column. Workers needed to tighten the column nuts weekly, and years of operation with the loose column nuts had detrimental effects to other components. The press eventually needed to be overhauled.

Solution: A new base, top platen and columns were manufactured, and the column nuts were upgraded to Superbolt® split tensioners. The split design assured there would not be complications while installing the nut onto the main thread, such as thread galling and seizing. The split design greatly eases assembly, especially for overhead installation below the press. To install the lower nuts, the column was lowered by crane and the two nut halves were easily installed.

Superbolt® Tensioners were also chosen in order to achieve a higher column preload. The jackbolts were tightened to 285 ft-lb to achieve 3,444,000 lbs of preload. An IR 252-3/4" impact was chosen for initial tightening, and final tightening was done with a torque wrench. Two workers tightened the bottom nuts in about two hours each, and one worker installed the top nuts in less than one hour each.

Tightening of four lower tensioners. 3/4" impact was used to build up column prestress. Final tightening was done with a torque wrench.

P.O. Box 683
1000 Gregg St.
Carnegie, PA 15106
www.superbolt.com
1-800-345-BOLT (USA)
1-412-279-1149 (International)
Fax: 412-279-1185
bolting@superbolt.com

January 21, 2009

The Solution To Bolting Problems

Heat Exchanger

This power utility replaced ten existing studs and nuts on one of their high pressure feed water heaters.

The old studs had problems with thread galling and nut seizure, partly due to the material not being suitable for the 850° conditions. The old 4" diameter studs were made from a carbon steel only good for low temperature service. Superbolt® replaced the studs and recommended using a more common material for high temperature service. The old hex nuts were replaced with stainless, high temperature, Superbolt® tensioners.

The Superbolt® Multi-Jackbolt tensioners eliminate the risk of thread galling and seizing because there are no twisting forces acting on the threads.

Previous stud and hex nut used in this application. You can see the thread galling on the stud.

P.O. Box 683
1000 Gregg St.
Carnegie, PA 15106
www.superbolt.com
1-800-345-BOLT (USA)
1-412-279-1149 (International)
Fax: 412-279-1185
bolting@superbolt.com

August 18, 2008

Application: Ball Valve

Superbolt® Tensioners have been used on ball valves for many years, however most times the tensioners have been installed all at once during a reinstallation. One major utility approached Superbolt® with a very inventive game plan to reduce the maintenance time for an upcoming outage.

Part of the planned spring outage by the utility was to pull a ball valve off-line to do some turbine work, with minimal down time. The customer's game plan was to have the standard nuts of the ball valve, which require hydraulic tensioners to install and remove, replaced with Superbolt® Tensioners prior to the outage. To accomplish this, the customer purchased (145) 4-1/2" - 8 tpi tensioners approximately 3 months ahead of the scheduled outage and installed them in their spare time over a several month period (2-3 per day) until both sides of the valve were fully outfitted.

During the spring outage 4 workers (2 per side of the valve)removed all the 4-1/2" tensioners in 2-1/2 hours! The estimated time savings over the previous hydraulic method was 2-3 days. Similar time savings was also accomplished on reassembly of the valve.

Since this is a pumped storage facility, the plant sells power at the peak times of the day to supplement its other steam power plants. Therefore it's essential for the facility to minimize any down time and using Superbolt® products helped accomplish this. The estimated savings by reducing down time was $5 million dollars (US).

savings was the fact that Superbolt® Tensioners were not only accurate, but repeatable in providing consistent load from stud to stud. Initially, the tension on the studs was monitored with extensometers. After seeing repeatable results with the first few tensioners installed, the remaining studs did not require any further monitoring, unlike the hydraulic method.

P.O. Box 683
1000 Gregg St.
Carnegie, PA 15106
www.superbolt.com
1-800-345-BOLT (USA)
1-412-279-1149 (International)
Fax: 412-279-1185
bolting@superbolt.com