4.—(1) A pipeline shall be fixed in such a manner and position that—
(a)it will not be adversely affected by the heat of the exhaust system of any engine or any other source of heat,
(b)it is protected from vibration and strain in excess of that which it can reasonably be expected to withstand, and
(c)in the case of a high pressure pipeline it is so far as is practicable accessible for inspection.
(2) Subject to sub-paragraph (4) a high pressure pipeline shall be—
(a)a rigid line of steel, copper or copper alloy of high pressure hydraulic grade, suitable for service on road vehicles and designed for a minimum service pressure rating of not less than 75 bar absolute, and
(b)effectively protected against, or shielded from, or treated so as to be resistant to, external corrosion throughout its length unless it is made from material which is corrosion resistant under the conditions which it is likely to encounter in service.
(3) No unsupported length of any high pressure pipeline shall exceed 600mm.
(4) Flexible hose may be used in a high pressure pipeline if—
(a)it is reinforced either by stainless steel wire braid or by textile braid,
(b)its length does not exceed 500mm, and
(c)save in the case of a pipeline attached to a gas container for the purpose of filling that container the flexibility which it provides is necessary for the construction or operation of the gas system of which it forms a part.
(5) If a high pressure pipeline or part of such a pipeline is so constructed or located that it may, in the course of its normal use (excluding the supply of fuel from a gas container), contain liquid which is prevented from flowing, a relief valve shall be incorporated in that pipeline.