EMS Gas Metering Spanner Set

Precision spanner set for gas meter installations.

EMS Gas Metering Spanner Set

By Sam White

By Sam White, Technical Manager at Energy Metering Solutions and YPPC 2019 finalist

WHEN I FIRST JOINED EMS in November 2016 and began installing gas meters, I encountered several situations that led to a search for more suitable tooling for the installation and maintenance of diaphragm gas meters with threaded connections.

Having identified the issues with the conventional tooling often used for these kinds of works, and unsatisfied with other options available on the market, I began creating a spanner set specifically designed to fit the brass fittings used on domestic and commercial gas meters, regulators and flexible connections (spec BS746:2014).

Despite the first version of BS746 being issued in 1937, no other product has been designed - to my knowledge - specifically for this application.

As well as the three sizes of meter connection, 1in, 1¼in and 2in, there are also a number of adaptors of different sizes within the BS746 spec and relating to BSP pipe thread to BS746.

I identified 14 different sizes across flat dimensions that would be necessary to complete the set and allow it to be used on all available fittings.

FIGURE 1 EXAMPLE BS746 ADAPTOR AND METER UNION
FIGURE 2 PROTOTYPE SPANNER SET AND INDIVIDUAL SPANNER
FIGURE 3 PRODUCTION SET – COMPONENTS AND BOXED SET

The Problem

The issue I first encountered (and saw repeatedly when exchanging gas meters) was overtightening by the original installer.

Elastomeric washers were brittle and over-compressed on removal. On inspection of the connection on the meter itself, washer seats were often seen to have a layer of thin rust, indicating that moisture had worked into the connection. The likely cause of the corrosion was overtightening of the nut on the meter union, causing excessive compression of the washer.

The washer becomes hardened over time and can no longer accommodate expansion and contraction of the joint with temperature changes, thus leading to leakage and moisture ingress. Most of the time, the leakage is minimal and usually detected by the end user.

However, this situation still causes unnecessary calls to the gas emergency line, load on the network staff to attend and make safe, usually some time off gas for the customer and an attendance by the meter operator to make the repair.

All of this could be avoided by correctly tightening the connection at the time of installation. One of the most extreme cases of overtightening I observed was on an old U40 meter installation in a brick house in a churchyard, which had become excessively corroded. The meter unions were so tight and corroded that when I took a pipe wrench to the fitting, the union was completely seized and the meter connection broke off from the meter casing. The installation had to be cut out and completely re-piped as a result.

Another issue with pipe wrenches and similar tools is they are often toothed, and cause damage to the brass fittings. These can become sharp or rounded off, presenting a cut hazard and the risk of slipping when applying force.

Pipe wrenches in the wrong application have been the cause of many a bruised knuckle, as any pipefitter will confirm. The larger diameters also require a jaw opening up to 86mm, which tends to only be available on large, long tools with handles in excess of 600mm.

These also tend to be weighty, adding to the overtightening problem due to the lever length. To compound all of the above, the meter itself is quite often boxed in or hard to fully access, and once overtightened can make life extremely difficult for engineers in the future.

 

Initial Design and Manufacture

Once the problems had been identified, I initially had the idea of creating seven double open-ended spanners, with lugs to attach a bar for extra leverage.

I hunted for a manufacturer who would be willing to help me develop the design. Maun Industries was interested and could see the benefit of the innovation to the industry, so we worked on a set of prototypes to be field-tested by EMS and our subcontractors.

The decision was taken in the interest of saving material and weight to separate all the spanner jaws and use a single drive bar. The drive would be via ½in square drive on a breaker bar, with an eight-pointed star cut-out to allow fitting of the drive bar in eight positions.

Also, in the set is an octagonal key for use inside the adaptor fitting, from 2in BSPM to 2in BS746M, which has an internal hexagon profile for fitting. The spanners were to be made of 6mm waterjet cut steel, then case hardened and laser etched.

FIGURE 4 DOMESTIC GAS METER SPANNER SET

TABLE 1 PARTS LIST WITH TIGHTENING TORQUES FOR FITTINGS WHERE ELASTOMERIC WASHERS ARE USED TO MAKE THE SEAL. TORQUE
FIGURES OBTAINED FROM BS746:2014 TABLE 1. SPANNER SIZES MATCHED TO WASHER SIZE ON INTENDED FITTINGS

Testing and Development

During field tests it became apparent very quickly that the angle of the drive bar in the set made the spanners likely to twist on application, so I instantly swapped it for a standard ½in ratchet, bringing the effort back in line with the nut.

Now there was a ratchet in use, it became unnecessary to have the eightpointed star, so the next version was to have a ratchet drive and a square hole to give a better fit.

Some spanners were a tight fit to their design, and due to manufacturing tolerances on the brass nuts, would not always fit. These sizes were adjusted to suit and now provide a good fit across the whole range of unions and adaptors.

Similarly, the key fitting was on the snug side, so this was adjusted too, and a short drive extension added to allow easier access down into the fitting with the key attached. A smaller box was sourced and a better layout designed to keep the spanners secure in the box.

We thought it would be worthwhile to carry out some destructive testing on the spanners, which provided results well in excess of the max strength test figures stated in BS746:2014, but we did see the potential for breakage if used incorrectly

Testing results were as follows:

  • 52mm spanner – stretched/broke at 135N/m
  • 80mm spanner – stretched/broke at 190N/m
  • 86mm spanner – stretched/broke at 190 N/m


    • Torque setting (BS746:2014 Table
  • 1 - Requirements for leak testing of elastomeric washers): 1in meter union (52mm spanner) 25N/m
  • 2in meter union (86mm spanner) 100N/m

    • The decision was taken to upgrade the thickness of the plate to 8mm, providing some extra durability to avoid breakages from overzealous/ inexperienced fitters.


    Finished Tool

    At the end of the design and testing process, we were left with a lightweight tool that could be used in tight spaces, in excess of 270 degrees rotation around the fitting thanks to the ratchet, eliminating slipping and damage to brass nuts and decreasing the chances of overtightening with a shorter lever.

    With the addition of a short inline torque adaptor, the force applied can be read out whilst installing, helping less experienced engineers to develop a feel for the correct tightening torque.

    There is an option for the set to be scaled down for domestic meters only (up to U16), to keep costs and weight down for the domestic engineer’s toolset. This is also in final packaging, mimicking the style of the full set


    Conclusion

    The thinking behind the development of this tool is an attempt to change the way that gas engineers approach their installations.

    There is a widespread belief among many installers that ‘the tighter, the better’. That kind of attitude when working with a metal-rubber-metal seal can lead to leaks in high frequencies, and given the softness of brass as a material is guaranteed to cause damage to the fitting.

    With the continued drive for smart meters, meter exchanges will continue to increase over the next five years. I view this as the perfect opportunity to promote a change in approach and to ensure that future engineers will be working on installations that are leak free, easier and safer to work on. This should made installers more confident in their connections to meters on completion of the job.

    With this tool, I believe we’ve taken a step towards how things should be done, rather than accepting the way things are, and hopefully we can continue to look for new innovations to make gas safer for everyone.


    References

    BS746:2014 – Specification for gas meter unions and adaptors


    Acknowledgements

    Thanks to the following people and organisations whose support made the development possible: Deep Valecha, Operations Director, Regent Gas, for sponsoring the development and patent filing for the invention; Phil Casper, Managing Director of PJ Casper Associates and consultant to EMS, for mentorship throughout the project; Maun Industries for their expertise and commitment to the development, design and manufacture; EMS subcontractors for field testing and feedback.