Nice and tight. TECHNICAL. HEATING. IGE/UP/1 Edition 2 tends to be a catch-all
procedure when the installation is outside the scope of. IGE/UP/1A ...
HEATING
TECHNICAL
Nice and tight The author Mike Heads has been in the gas industry for nearly 40 years. He began his career as an apprentice Service Engineer with British Gas. He completed various gas utilisation qualifications then progressed to become a trainer for 14 years. Mike joined Ideal Boilers as a trainer and centre manager, completed a BSc (Open) and then a PGCE. Became a college lecturer teaching plumbing and gas, and now works for NGST as a trainer/assessor. He is a member of various organisations including MIGEM Eng Tech, MIDHEE, past president of the Yorkshire Gas Association. Presented various papers on combi boilers and condensing boilers, written a central heating fault-finding book for CORGI. Writes much of the training material used by NGST.
Tightness testing is one of the most important procedures in the gas industry. Mike Heads looks at the most involved and thorough method – IGE/UP/1 Edition 2.
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GE/UP/1 Edition 2 tends to be a catch-all procedure when the installation is outside the scope of IGE/UP/1A, IGEM/UP/1B and IGEM/UP/1C. It can be used for 1st, 2nd and 3rd family gases, any pipe size and up to a pressure of 16 bar. To carry out this testing procedure, the operative must be competent and have adequate knowledge and experience. Strength testing If the installation contains new pipework, it should be strength tested. Before any test times can be calculated, you need to
know both the MOP (maximum operating pressure), which can be obtained from the installation’s designer, and the MIP (maximum incidental pressure), which can be obtained from the meter asset manager. Before carrying out the test, a risk assessment is required to check for any major weaknesses, that joints are correctly made, and that pipework is adequately clipped. Spool pieces may need to be fitted where components could be damaged by the test pressure. Table 1 in IGE/UP/1 Edition 2 provides strength test pressures, stabilisation times, test times and the maximum drop allowed.
Example A low-carbon steel pipework installation with a volume of 2m3, Maximum Incidental Pressure of 800mbar and a Maximum Operating Pressure of 120mbar. Using Table 1, the test pressure would be either 1.1 3 MIP or 2.0 3 MOP, whichever is the greater: 1.1 3 800 = 880mbar 2.0 3 120 = 240mbar The strength test would be at 880mbar with 10 minutes stabilisation, 5 minute test and a maximum permitted drop during the test of 20% STP or 176mbar (Table 1). A pneumatic test above 1 bar contains a great deal of energy so if the pipe were to fracture during the test, the volume and pressure could cause a small explosion. If the strength test exceeds 1 bar, an exclusion zone is
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HEATING
TECHNICAL
Figure 1. Regulator linked out.
required depending on the pressure and volume of the installation. Hydraulic testing should be carried out if testing metallic pipework above 2 bar and 150mm and above 3 bar for all PE pipework. This is seen as a specialist procedure because removing the water after the test could be problematic. The volume of the installation is required for tightness testing and for the strength test when the testing pressure exceeds 1 bar. To calculate the pipework volume IGE/UP/1 Edition 2, Table 4 provides the volume for 1 metre, which is then multiplied by the length. Once all the lengths are added together, it is normal procedure to add on 10% for the fittings.
››The pressure drop is not based on gauge movement or perceptible movement – it is based on leakage rate.‹‹
Tightness testing To carry out a tightness test, the volume of the installation needs to be calculated. The gauge needs to be selected – Table 6 provides a list of gauges, their pressure range, maximum test time durations and their readable movement. The gauge readable movement is also used for calculating the test time durations. This test procedure is different to the other three test procedures (IGE/UP/1A, IGEM/UP/1B and IGEM/UP/1C) because the pressure drop is not based on gauge movement or perceptible movement. Instead, it is based on leakage rate. The leakage rate
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in adequately ventilated areas of less than 60 m3 is calculated from the threshold of smell – 5 parts odourised natural gas in 10,000 parts of air. (0.05% gas in air). With 1. 5 air changes per hour, this equates to 0.000 75 m3 per hour per m3 of space. There are four maximum permitted leak rates for natural gas: A. Inadequately ventilated areas (Type A) – 0.001 4 m3/hr B. Adequately ventilated internal area < 60 m3 – 0.000 5 m3/hr C. Adequately ventilated area > 60m3 or external exposed areas – 0.03 m3/hr D. Underground (buried) – 0.03 m3/hr A new installation tightness test is based on Type A (inadequately ventilated area), which varies depending on the gas type. The rate for natural gas, for example, is 0.0014 m3/h. The calculation for new or existing installation in Type A areas is: GRM 3 IV 3 F1 F1 is derived from Table 6 and gives values for fuel gases and air or nitrogen. If testing a new installation for natural gas using air, the figure is 67. Example: An installation with a volume of 2 m3 and using a U-gauge manometer GRM 0.5 mbar. GRM 3 IV 3 F1 = 0.5 mbar 3 2m3 3 67 = 67 minutes The recommended time for a water gauge is 30 minutes, meaning that in this example it would be recommended to use a different type of gauge. When the test time exceeds the recommended test time, this equipment could still be used but barometric (atmospheric pressure) and temperature changes during the test would be needed.
In this installation, testing would be against a gas valve meaning that a let-by test would be required. This would be carried out at 50% of the operating pressure for the test time duration. If there is an increase in pressure and it is confirmed, the test should be suspended and made safe before the emergency service call centre should be informed. For this example, the testing times would be: • 14 minutes let-by test – at 50% of the operating pressure. If the installation is a low pressure installation of 21 mbar, this would be at 10.5 mbar. • 15 minutes stabilisation time at the operating pressure and 14 minutes test. A digital gauge accurate to two decimal places has a GRM of 0.1 mbar. GRM 3 IV 3 F1 = 0.1 mbar 3 2m3 3 67 = 13.4 minutes. Correct procedure would be to round up to the nearest minute. The test time would therefore be 14 minutes, and the recommended test time for this gauge is 15 minutes. The stabilisation time is 15 minutes or the tightness test time – whichever is the longest. In this case, there would be no let-by test because the test is being carried out using air. The test would therefore be 15 minutes stabilisation and 14 minutes test. If the test includes plastic MDPE pipework above 1 bar, creep or stretching of the pipe needs to be considered. Appendix 7 deals with creep and soak times. Existing installations Before testing, a thorough examination of the installation should be carried out to ensure there are no open ends, and any regulators or non-return valves that can trap gas should be linked out/bypassed. Alternatively, the regulator could be adjusted to prevent lock-up (see Figure 1) – this would have to be reset after testing. The procedure for calculating test times requires calculating volumes in the same way as a new installation. Please note that an existing installation may
include a meter. Table 3 provides meter and cyclic volumes – for tightness testing the IVm is used. IVm + IVp + IVf = IVt Example: U40 meter with pipework volume of 2m3 • The volume for a U40 meter is 0.067m3 • 10% is normally added to the pipework volume for fittings, which would be 0.2 m3 Using IVm + IVp + IVf = IVt 0.067 m3 + 2 m3 + 0.2 m3 = 2.267 m3 If the installation was in an adequately ventilated area, the smallest occupied space is included in the calculation of the test time: Existing pipework in Type B area 2.8 GRM 3 IV 3 RV –1 3 F1 RV –1
When a test is carried out and the pressure drop during the test period exceeds the gauge readable movement, the MPLR (Maximum Permitted Leak Rate) needs to be calculated, as follows: F3 3 GM (mbar) 3 IV (m3) TTD (mins) = m3/hr of fuel gas at OP F3 can be obtained from Table 11, and for all fuel gases it is 0.059 for air while nitrogen will vary. Example: An installation of 2m3 with a pressure drop of 1.5 mbar over a test duration of 14 minutes.
F3 3 GM (mbar) 3 IV (m3) = m3/hr TTD (mins) 0.059 3 1.5 (mbar) 3 2m3 14 minutes = 0.0126m3/hr If this were in a well-ventilated area with a smallest occupied space of 20m3, the leakage rate for natural gas allowed (providing there is no smell of gas) using Table 8 is 0.0005m3/hr for each m3 of room volume. 20m3 3 0.0005 = 0.01m3/hr In this case, the leakage rate exceeds the maximum permitted leakage rate, meaning that the leak would have to be traced and repaired until the leakage rate is less than the permitted leakage rate and there is no smell of gas. Any pipework in inadequately ventilated areas should be tested using LDF or a suitable gas detector. After a successful tightness test and before commissioning and re-commissioning any appliance, a tightness test should be carried out of the pipework between the appliance and its isolation valve. If this appliance connector test falls into the scope of the IGEM/UP/1B or IGE/UP/1A, a two minute test can be carried out providing that the volume is less than 0.12m3. n
TO SUM UP
(or 1/RV) is the reciprocal of the room volume. If the room volume was 20 m3, this would be 1 ÷ 20 = 0.05. If the test is using gas, F1 would be 42 (Table 9). If a digital manometer is used to two decimal places, this would give a GRM of 0.1 mbar.
› Any new pipework is normally strength tested to calculate the time – the MIP and MOP is required.
2.8 GRM 3 IV 3 RV –1 3 F1 = Tightness test time
› The maximum leakage rate for adequately ventilated areas is 0.0005m3/h per m3 of space.
2.8 3 0.1 3 2.267 3 0.05 3 42 = 13.33 minutes, which would be rounded up to 14 minutes. The stabilisation time would be 15 minutes or the tightness test time (whichever is longer). In this case, it would be 15 minutes.
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› For new and inadequately ventilated areas, the test time is calculated using: GRM 3 IV 3 F1. › New and inadequately ventilated areas have a maximum leakage rate of 0.0014m3/h. › For existing installations in adequately ventilated areas, the test time is calculated using: 2.8 3 GRM 3 IV 3 RV–1 3 F1.
