Why Use Bolt Caps?
There has usually been a relaxed consideration for the fire protection of the bolts and nuts on bolted connections. The main reason is that there is no specific regulation, standard or test protocol to follow.
The advice from intumescent paint manufacturers and accepted generally by the specialist organisations is as follows: “un-primed bolt heads [and nuts] will require correct preparation and priming prior to the application of the [manufacturers’] basecoats”.
In addition the advice states “All products should be applied in accordance with the manufacturers’ instructions”
This advice relates to each primer manufacturers’ instructions which are generically:
- Degrease the bolt and nut; it will then need rinsing off
- Bright steel bolts can be primed, preferably with a surface tolerant primer
- Galvanised bolts need to be acid etched and then primed
- For other pre-coated bolts and nuts i.e. sheradised/zinc coated seek the advice of the primer manufacturer or the intumescent manufacturer
In any case, in each of the above circumstances, it is highly likely that a tie coat/primer is going to be required prior to any intumescent coating.
What are the likely outcomes of not doing this preparation?
- The nut and bolt will not be adequately fire protected
- The intumescent paint will start falling off the bolted connection within a relatively short period of time
- The intumescent supplier may withdraw their product warranty
- The insurance company may withhold or reduce a claim if it can be shown that the work was not carried out in accordance with the instruction
- You are potentially liable for not ensuring the work was properly monitored and carried out
What QA procedures should be available to ensure adequate fire protection?
- Nuts and bolts must be separately detailed and priced on a bill of quantity (See M61 110 of the NBS)
- FIRAS or other third party accreditation body will need to add the fire protection of bolts and nuts specifically to its monitoring procedures if it has not already done so.
- If intumescent paint is used for the fire protection of the bolts, measurement details should be recorded and stored on coating reports showing the intumescent coverage is correct
- Details of the correct application of intumescent paint should be noted on the Contractors’ QA documents
- Sub-contractors’ work sheets should confirm the correct procedures have been followed.
Is it fair to say that a lot of work is needed just to protect the bolts and nuts of a bolted connection? The advice from the ASFP is quite clear “All bolted connections should be adequately fire protected to the correct fire protection period”.
So why use bolt caps?
Because:
- Independently fire tested to two hours fire protection using BS476 part 20
- No mix up over the fire protection period. The caps are all the same rating
- No prior preparation is required to the bolts and nuts
- No need to check that the preparation for priming has been carried out correctly
- Bolt caps are very difficult to remove without breaking them which adds to the security of the building
- One clack of a rubber mallet and it is fixed
- Can be painted off site
- Can be painted over on site, at the same time as the top seal to the surrounding steel is applied
- The decorator, the intumescent painter or the structural steel contractor can install them
- If the Cap is not on the connection is not protected
- Aesthetically pleasing for external exposure in public places
- Value for money
For more information please contact info@scapeconnections.co.uk Tel: 01694 751394.