Gas Safe Registration (ACS) Liquefied Petroleum Gas (LPG) - Domestic and Park Homes Flashcards

24 sample cards from the Liquefied Petroleum Gas (LPG) - Domestic and Park Homes deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. Why can LPG pipework often be smaller in bore than the equivalent natural gas pipework for the same heat input?

   LPG has a much higher calorific value per cubic metre (propane $\approx 93\ \text{MJ/m}^{3}$ vs natural gas $\approx 38\ \text{MJ/m}^{3}$), so far less volume of gas is needed to deliver the same energy. Lower volumetric flow plus the larger permitted pressure drop ($2.5\ \text{mbar}$) allows smaller pipe sizes.

2. Why must LPG-specific pipe sizing tables (not natural gas tables) be used when sizing propane pipework?

   Pipe-sizing discharge depends on gas density and the permitted pressure drop. Propane's relative density ($\approx 1.5$) and the $2.5\ \text{mbar}$ allowance differ from natural gas ($\approx 0.6$, $1\ \text{mbar}$), so the flow-versus-length tables are different; using NG tables would give incorrect (undersized or oversized) results.

3. When converting an appliance heat input to a propane gas rate for pipe sizing, what calorific value is used?

   The propane gross calorific value of approximately $93\ \text{MJ/m}^{3}$ ($\approx 25.9\ \text{kWh/m}^{3}$). Gas rate $\dot{V} = \dfrac{\text{heat input (kW)}}{\text{CV (kWh/m}^{3})}$ gives the volumetric flow needed to size the pipe.

4. At what pressure is a tightness test on a domestic propane installation normally carried out?

   At the appliance operating pressure of $37\ \text{mbar}$ for propane (the regulator outlet pressure). A water gauge/manometer or electronic gauge is connected at a test point and the system stabilised before timing the test.

5. On a new LPG pipework tightness test (pipework only, no appliances) at $37\ \text{mbar}$, what pressure drop is acceptable?

   There should be no perceptible pressure drop. New, sound pipework with the system isolated should hold the test pressure with zero movement on the gauge over the test period; any drop indicates a leak that must be traced and rectified.

6. Outline the basic procedure for an LPG tightness test using a manometer.

   Isolate the installation, connect a calibrated gauge at a test point, raise the system to operating pressure ($37\ \text{mbar}$ propane), allow a stabilisation period for temperature/regulator settling, then time the test period and observe the gauge. Confirm let-by at the regulator/control first, then check for any pressure drop indicating leakage.

7. What is a regulator 'let-by' test and why is it done before a tightness test?

   It checks that the regulator/control valve is not passing (letting by) gas when shut. With the control closed and a small test pressure applied, the gauge must not rise. If it does, the valve is leaking past its seat and would mask or invalidate the tightness test result.

8. What is the difference between a strength (pressure) test and a tightness test on LPG pipework?

   A strength/pressure test proves the mechanical integrity of pipework at a pressure above operating pressure (used on new, buried or concealed pipe before commissioning). A tightness test proves the system is gas-tight at operating pressure before letting gas to appliances. Strength testing is normally done with air; tightness can use gas or air.

9. What is purging in an LPG installation, and why is it critical?

   Purging is displacing air from new/recommissioned pipework with gas (or displacing gas with air/inert gas when decommissioning), so that no flammable air–gas mixture remains within the flammable range. It must be done to a safe outdoor location, away from ignition sources, because LPG's narrow, low flammable limits make trapped mixtures dangerous.

10. When purging LPG pipework, where must the discharge be directed and why?

    To a safe place in open air, away from ignition sources, drains, gullies and low-level openings. Because LPG vapour is heavier than air it can flow along the ground and collect in low spaces, so it must not be vented near cellars, basements or below-ground drains.

11. What is the CPA1 (residential park homes) assessment concerned with?

    It covers the safe installation, testing, commissioning and inspection of LPG systems serving residential park homes — including the bulk/cylinder supply, regulation, the service pipework into the home, tightness testing and appliance connection under park-home conditions.

12. How does the LPG supply to a residential park home typically differ from a permanent dwelling?

    Park homes are usually fed from a communal bulk tank or cylinder bank via buried/distribution pipework to a meter or regulator at each unit, and the home is a transportable structure on a pitch. This means attention to flexible/movement joints, the service isolation valve at the unit, and ventilation suited to a single-storey timber-framed structure.

13. Why is low-level ventilation especially important in a park home using LPG?

    Because LPG is heavier than air, any leak collects at floor level in the void or living space. Permanent low-level ventilation/air bricks and avoidance of unventilated underfloor voids reduce the risk of a flammable accumulation in the lightweight structure.

14. Where should LPG cylinders or the bulk vessel serving a park home be located?

    Outside, in the open air, on a firm base, with the required separation distances from the home, boundaries, openings, drains and ignition sources, and never below ground level or in an unventilated enclosure. Regulators and changeover equipment are positioned for safe access and protection.

15. What does the BMP (boats and inland waterway craft) module cover?

    The safe installation, testing and inspection of LPG systems on boats and inland waterway craft — cylinder lockers, vapour-tight enclosures, appliance flueing/ventilation, pipework on a moving vessel, and tightness testing to BS EN ISO 10239 / BS EN 1949.

16. What are the key requirements for an LPG cylinder locker on a boat?

    It must be vapour-tight to the boat's interior, top-opening, and drained from its lowest point to the outside of the hull above the waterline so that any leaking heavier-than-air vapour drains overboard rather than into the bilge. Cylinders are secured upright and the locker is dedicated to LPG.

17. Why is LPG accumulation in a boat's bilge particularly dangerous?

    LPG vapour is heavier than air and the bilge is the lowest enclosed point, so leaking gas collects there with no natural escape. A spark from the engine, bilge pump or electrics can ignite the trapped mixture, causing an explosion — hence vapour-tight, overboard-drained cylinder lockers and bubble/leak testers.

18. What is a bubble (leak) tester on a boat or caravan LPG system?

    An in-line device fitted near the cylinder that lets the user quickly check for leaks: when the test button is operated, bubbles in a sight glass indicate gas flowing (a leak) when all appliances are off, giving a simple routine tightness check before use.

19. What standardised appliance operating pressure is used for LPG systems in caravans, motor caravans and boats, and why?

    $30\ \text{mbar}$, regardless of whether propane or butane is used. A single standard pressure (introduced for leisure/marine harmonisation) allows interchangeable appliances and 30 mbar regulators across butane and propane supplies in habitation vehicles and craft.

20. In a touring caravan/LAV, what are the key ventilation requirements for LPG appliance safety?

    Permanent high- and low-level ventilation sized for the appliances, with low-level vents to clear heavier-than-air LPG, and a sealed/vented cylinder locker draining to outside. Room-sealed appliances are preferred; flueless appliances need defined ventilation free areas to prevent CO build-up.

21. How are LPG cylinders required to be housed in a touring caravan or leisure accommodation vehicle?

    In a dedicated gas locker that is sealed (vapour-tight) from the living space, ventilated/drained at low level to the outside, with cylinders secured upright and the regulator and changeover fitted within. This contains and vents any leak away from the habitable interior.

22. What does the PDLP assessment relate to?

    PDLP covers LPG work in permanent dwellings, including owner/self-build LPG installations — the design, installation, testing and commissioning of fixed propane/butane pipework and appliances in conventional buildings, supplied from bulk tanks or cylinder banks.

23. What special considerations apply to LPG in basements or below-ground rooms of a permanent dwelling?

    Because LPG is heavier than air, LPG appliances and cylinders are generally not permitted in basements, cellars or below-ground rooms without specific safeguards, since a leak would accumulate with no natural escape. Installation must avoid creating low-level pockets where vapour can collect.

24. For a self-build (PDLP) propane installation, summarise the commissioning sequence before handing over to the customer.

    Confirm pipework is correctly sized and supported; carry out a strength/pressure test on new pipe as required; perform a regulator let-by check and a tightness test at $37\ \text{mbar}$ with no perceptible drop; purge the system safely to outside; light and commission each appliance, checking working pressure ($37\ \text{mbar}$), gas rate, flame picture, flueing/ventilation and combustion (CO/CO\textsubscript{2}); then instruct the user.

What this deck covers

Liquefied Petroleum Gas (LPG) - Domestic and Park Homes flashcards FAQ