Written by Valley Forge’s James Brooks

Controlled bolting has for many years been associated with critical bolted joints. The term is more often applied to the act or procedure of installation than to the life cycle of the bolted joint.

Application, measurement and control of torque has also been the predominant challenge for users of controlled bolting methods.

Installation methods have been designed to deliver torque-based final results. They have required the use of tooling with controlled output settings and with highly specific procedures in an effort to deliver reliable, repeatable clamp loads.

A shift in thinking to controlled bolting is taking place in many industries:

The use of direct tension measurement and control, versus torque, is growing.  Inherently more accurate, tension control only uses torque as the “driving force” used to rotate and tighten a bolted joint.  If measured directly, it can be used simply and quickly to manage torque-based equipment output.

But after the installation, can the bolted joint be controlled?

We do not have bolts that tighten themselves, yet, but using tension-based load monitoring fasteners is a reality.  With the same benefit over torque, tension-based monitoring is more accurate.

Condition monitoring is the most costly part of controlled bolting. Factors include; inspection frequency, accessibility and equipment downtime, to name just a few.

The use of Valley Forge’s SPC4 tension indicating technology is playing a large part in driving these changes in controlled bolting installation and post-installation thinking.

Once installed, an SPC4 bolt or stud can be considered as the “foundation” from which a menu of interchangeable inspection options can be chosen. With a standard reading surface across all sizes of bolt or stud, different readers can be used as required or desired.  They include:

  • Manual, snap-on readers both in-line and right-angle.
  • Wired electronic readers with data collection options and output control for torque tightening equipment operation.
  • Blue tooth enabled readers.
  • Hard-wired remote readers.
  • Pre-programmed wireless readers for remote monitoring, including WiFi and Low Frequency options.
  • Wireless Low Frequency readers that have internet user interfaces and can be programmed to send an alert if a bolted joint tension level is reached i.e. using the IOT, critical bolted joints can talk to you if they are having a problem: or are about to have a problem.

These options are taking the cost and complexity out of condition monitoring of critical bolted joints.  They are now controlled for life.

Want to know more?  Contact us today.

For more information or discuss what this means for your bolting application, please reach out to our sales team anytime at sales@vfbolts.com.

The spring ASTM Committee F16 on Fasteners meeting was held this past week and was attended by several Valley Forge members.

The purpose of the F16 Committee, which is broken into subgroups, is to maintain, update and improve existing standards.

The various subcommittees conducted their usual business and F16 main wrapped up on Tuesday afternoon.

This report is intended to high lite some of the major issues and topics from the meetings.


ASTM F2482 Load-Indicating Externally Threaded Fasteners


During the F16-02 meeting a representative of Industrial Indicators (formally Stress Indicators) requested that a task group be formed to include their product, Smart Bolt & the “Chroma Series”, into the F2482 specification.  Several years ago, F16 made a determination to reduce the number of fastener standards by grouping like product standards.  Although the F2482 standard is not up for renewal until 2020, it was agreed that a task group be formed.  Valley Forge was initially a principal in the introduction and the writing of this standard.  It is expected that the rewrite of the standard will be divided into two (2) distinct categories.  They will be the original “Measuring Type” and a “Go/No Go” type.  Valley Forge will participate in the work group to insure the integrity of the standard and the clear distinction of the two (2) types.


F16.96 Subcommittee on Bolting Technology 

The interesting aspect of this committee are the Technical Presentations delivered by various companies.  The representative of Industrial Indicators (formally Stress Indicators) introduced their new “Chroma Series” tension indicating fastener.  Unlike their Smart Bolt it requires a chromatic displacement transducer to determine if the predetermined tension has been reached.  It was presented as an upgrade of the Smart Bolt with an expected accuracy of +/- 5%.  To date the development is being completed, and a protoype unit was on display for inspection.


F16.97 Coordination with North American TAGs to ISO TC 2 on Fasteners

ISO TC2 on Fasteners worldwide representatives will be meeting in Montreal Oct. 15 – Oct. 19.

In the last meeting the Chinese Delegation presented an interesting item.  They had wished to include in ISO 898, a product in class 8.8 & 9.8, using non-heat-treated material.  They have been using this material throughout China for several years. Their attempts at 10.9 have not been successful.  This concept was totally rejected by the committee.  The question is “will this product find its way into North America”?

After several years of discussion, testing and review of results, ISO 4042 has been voted on and accepted.  This is an electroplating specification that somewhat follows ASTM F1941 removing baking for items 360 HV and below.  They however, put in a grey area between HV 360 – 390 that cautions the specification user that they may wish to consider baking.  We will understand this new specification better once we obtain a printed version.


B08 Metallic and Organic Coatings

B08-06 Soft Metals

As most of you are aware there are two (2) standards within ASTM, both pertaining to electro deposited zinc.  They are F1941 & B633 and they disagree at what hardness is baking to be performed.  In 2007, B633 was change to make baking mandatory at RC31, grade 5 or higher.  The B08-06 committee has claimed that there was work performed to support this change.  They however; have not presented the supporting documents. ASTM has stated that they will not become involved to resolve the discrepancy.  It must be resolved by the individual committees. The specification has now been basically rewritten and submitted for comments.

Of course, many negatives were received and an all-day work session was held on Wednesday to resolve the negatives.  Basically, many of the areas of the document were rewritten and restructured to resolve the negatives.  At the end of the day there still remained negatives. It was decided to once more send out the rewritten specification for a vote.  The negative comments will be dealt with at the next meeting or by special action by the voting members.  It is believed that the majority of the voting members will accept the rewritten standard and find the negatives “non-persuasive”.  The rewriting of this standard and the removal of the requirement for baking beginning at RC31 is very important.  Valley Forge has a voting member serving on this committee.

Valley Forge is very proud to announce that our Load Indicating Fasteners have passed Military Shock Testing Standard MIL-S-901D!!

This is a rigid test that means great things for our fasteners moving forward with many different applications involving any degree of shock to the fastener while in service.

Shock Tests, Requirements for High-Impact Shipboard Machinery, Equipment and Systems

  • Specification: Testing was completed per MIL-S-901D, Lightweight, Grade B, Class 1, Type C shock testing requirements.
  • Location: Testing was done by Element Material Technology in Jupiter, Florida
  • Purpose: The purpose of this testing is to verify the ability of shipboard equipment to withstand shock loadings which may be incurred during wartime service due to the effects of nuclear or conventional weapons.
  • Load Indicating products tested:
    • Standard SPC4™
    • No-Standoff SPC4™
    • Single Lever Maxbolt™
    • Dual Lever Maxbolt™
    • Mini Maxbolt™
    • No-Standoff Maxbolt™
  • MIL-S-901D is a common requirement for shipbuilders and other companies supporting the US Navy.

Our Maxbolt™ crosstalk video demonstrates the interactions which occur between fasteners in a typical flanged piping connection.  This scenario is a perfect example of the complexity of many real-life bolted joints; particularly those with gaskets.

The demonstration clearly shows the limitations inherent with torque-tightening.  The resulting differences between theory and reality can be significant.  Not only does torque-tightening deliver limited accuracy in terms of resulting bolt tension, but it cannot tell you what happens once the torque wrench is removed.

All conventional tightening methods except for load indicating fasteners have this limitation, in that they are only useful for initial installation, and cannot be used to provide feedback from the bolts (and the joint) after tightening.  It is true that methods such as torque-tightening, hydraulic tensioning, or turn of the nut techniques can be used in various ways after the initial bolt tightening in an effort to compensate for interactions such as bolt cross-talk.  However these methods all fundamentally use the same approach; repeat the same (or a variant of the) procedure used during initial tightening.  In the context of torque-tightening, a common practice in industry is to repeatedly torque the bolts in a joint over-and-over until the nuts do not turn.  If the nuts turn this implies that the bolt became loose during prior tightening.  Obviously this information is very subjective in nature and does not provide any useful information other than some form of load relaxation or joint interaction is actually taking place.

If load-indicating bolts are utilized, as in this video demonstration, the nature and magnitude of the interactions can be quantified, and more importantly corrected for.  Rather than embarking on the time-consuming process of blindly re-torquing all bolts multiple times, a more calculated approach can then be taken which targets only those bolts with unacceptably low load.


Fastener Crosstalk is the phenomenon where as fasteners are tensioned, they affect the load on other fasteners around them, essentially speaking to each other.

We have been wanting to make a video that can show this intriguing display for a very long time.  Because the Maxbolt™ can measure continuous tension in the fastener, there is simply nothing that can show crosstalk in fasteners better.

In making this video, an actual installation was done on an ASME class 300 flange unit.  All measurements were recorded precisely during tightening with 3/4″ Maxbolt fasteners and a spiral wound gasket installed.   The full procedure was:  (1-5-3-7), (2-6-4-8) PCC- Legacy Modified.

First Pass: Fasteners were torqued to 55 ft lbs, which targeted 22% on the Maxbolt (40% of target torque STAR)

Second Pass: Fasteners were torqued to 138 ft lbs, which targeted 50% on the Maxbolt (100% of target torque STAR)

Third and Final Pass: Fasteners were torqued to 138 ft lbs, which targeted 50% on the Maxbolt (100% of target torque CW)

Calculated with K= 0.17, 100% on MB = 26,700 Lbf

During the first pass, there was a considerable amount of crosstalk in the bolts.  A the very beginning all fasteners started hand tightened, but we found many were much more loose than this as we tried to torque them.  During the second and final pass though, we really see the bolts crosstalking to each other and it reflected in their tension in the video.  This video animation of an actual installation illustrates that controlling a joint with torque results in uneven tensioning of the fastener because of fastener crosstalk.  With Maxbolts, designed preloads can be monitored continuously and show +/- 5% of targeted load to ASTM F2482 standards.

We hope you enjoy this video as much as we enjoyed making it.  Please share and stay tuned for more animations like these to see more of the Fastener Revolution.


The spring meeting of ASTM F16 took place the first week of May in San Antonio, Texas. F16 meets to review, update and propose new fastener standards. The meetings take place over several days, as F16 is comprised of eleven (11) Subcommittees, plus the main F16 Committee. The Main Committee meeting wraps up the Subcommittee meetings, as each chair reports on the respective meeting activities.  Glenn Snowberger, as a member of F16, was in attendance representing Valley Forge.

As usual much work was accomplished in reviewing and voting on ballot issues pertaining to revising and or eliminating standards.

All changes, revisions or new proposed standards are balloted to the voting committee members. All negative ballots are discussed and voted on before any change can be initiated or any standard can be moved forward and submitted for a Main Ballot vote.

The subject of Hydrogen Embrittlement was a major point of discussion during several of the meetings. As a result of several fastener failures in the Gulf of Mexico, that were initially attributed to Hydrogen Embrittlement and then reversed, it was discovered that there are two (2) existing standards within ASTM covering Zinc Electroplating Plating that are not in agreement on the issue of at what hardness should fasteners be baked after plating. The standards are F1941 and B633, which are under the jurisdiction of two (2) separate committees, F16 Fasteners and B08 Metallic & Inorganic Coatings.

This difference is of major importance and cannot be left to exist. API ( American Petroleum Institute) and ASTM A01 have joined together in a request to have the two (2) committees find a common ground and resolved this disparity. It must be noted that B633 was changed in 2007 to require baking at hardness of RC 32 and above. Prior to 2007 it was in agreement with F1941. There are questions as to what brought about this change and what supporting studies and testing are available to support this change by B08.