"Don't forget, when adding bits of "Bling" to an existing or New plant, you may be "modifying" the system - how many have fallen foul of insurance companies with car conversions?
Think, act or ignore, it's your own choice."
Insurance companies insure a car based on risk, and insure the entire vehicle. Steam insurance policies are to insure a pressure vessel only, associated pipework and fittings, as long as they perform safely within their working limits and perform the duty they are designed to do to the same or better level than OEM, then insurers are happy as they do not compromise the pressure vessel. Insurance companies do not insure the 'system' as you put it, but only provide cover to the pressure vessel if proof that ancilliary systems that maintain the plant's safety are in good working order- basically, water supply, safety valve operation and pressure gauge accuracy.
If it was proven that modifications did not fall into the above standard, and an accident happened, then yes, there would be a problem with liability.
As an engineer who works with steam on a daily basis, and responsible organiser of a public regatta I'm well aware of liabilities and what is important and what isn't- the document above may be a well written code of practice that we would all do well to follow, but the fact of the matter is that anyone who can prove their plant is safe- ie. boiler cert., and is insured to a good enough standard- then they can display their boiler under steam in public. However, if their boiler is under 3BarLitres, then as unwise at it may be, they do not need insurance or a boiler certificate, to be within the remit if the law in the UK, if they wish to exhibit their plant in public.
As a regatta organiser I do specify that any steam boiler on public display as part of the regatta must have insurance, and if above 3BarLitres, a valid boiler certicate- this year boilers range from horizontal boilers that would fit in your hand, to loco boilers that hold around 200gal, with everything inbetween.
Greg