The ZANDZ Technical Centre has received a request to calculate the lightning protection for a crude oil custody transfer metering system. Let's consider the solution offered by the technical center's specialists.
- Facility: a crude oil custody transfer metering system.
- Architectural drawings.
- Soil resistivity: 100 Ohm*m.
The activities have been performed according to:
- the EIC, Rev. 7, SO 153 34.21.122 2003 Instructions for Mounting Lightning Protections of Buildings, Structures and Industrial Communications (hereinafter referred to as SO);
- RD 34.21.122-87 Instructions for Mounting Lightning Protection for Buildings and Structures (hereinafter referred to as RD);
The facility is classified as Category II of the lightning protection.
Requirements provided by the customer and in the regulatory documents:
- The protected facility is classified as Category II with the protection zone B according to RD (item 3 of Table 1 RD for В-1г class zone according to the EIC as specified by the customer).
- Facilities of Category II of lightning protection can be protected both by standalone lightning arresters and by lightning arresters installed on the facility.
- The space above the breather valve limited by a cylinder 2.5 high with the radius of 5 m should be protected.
A set of arrangements ensuring compliance with the lightning protection requirements is based on the following solutions:
- 1 x 20 m standalone lightning arrester is installed. The lightning arrester generates protection zone B according to RD as shown in the drawing;
- the protection zone covers an explosive space above breathing valves with dimensions H = 2.5 m, R = 5 m, according to item 2.6 of RD;
- laying a 5 m horizontal ground electrode for current spreading in two directions at 90 degrees between them;
- at the end of the horizontal ground electrode, one vertical electrode with the length of 3 m is installed in each directions;
- 3 m steel copper-plated grounding devices are used as a vertical grounding device;
- a steel copper-plated bar 30 x 4 mm is used as a horizontal grounding arrangement;
- vertical and horizontal electrodes, as well as horizontal electrodes with the interception rod are connected using clamps ZZ-005-064.
Ground terminal resistance calculation:
Vertical grounding arrangement resistance:
Ом - Ohm
Верт - Vert
Экв - Eq
where ρ is equivalent soil resistivity, 100 Ohm·m;
L is vertical electrode length, 3 m;
d is vertical electrode diameter, 0,014 m;
T is deepening;
t is the distance from the ground surface to the grounding arrangement, 0.5 m;
Horizontal electrode resistance:
Гор - Hor
where ρ is soil resistivity, 100 Ohm·m;
b is horizontal electrode width, 0.03 m;
h is horizontal grounding depth, 0.7 m;
Lhor is horizontal electrode length, 10 m.
Electrical impedance of the grounding arrangement:
ЗУ - GA
where n is number of vertical grounding arrangements - 2 pcs; horizontal grounding arrangements - 1 pc;
kutil is utilization rate, 0.81;
estimated resistance of the grounding arrangement is 9,72 Ohm.
Условные обозначения: - Legend:
- отдельно стоящий молниеприемник H=20 м - standalone lightning arrester H = 20 m
- горизонтальный заземлитель - horizontal grounding arrangement
- зажим для подключения проводника - clamp for connecting wire
- вертикальный заземлитель длиной 3 м - 3 m vertical grounding
Figure 1. Layout of grounding arrangement parts.
Table 1. List of needed materials.
|№||Part number||Name||Quantity, pcs.|
|Lightning protection system:|
|1.||ZZ-201-020||ZANDZ 20 m vertical lightning arrester (galvanized steel; with parts embedded under the foundation)||1|
ZANDZ Conductor connection clamp
|3.||ZZ-001-065||ZANDZ Copper-plated threaded grounding rod (D14; 1,5 m)||4|
|4.||ZZ-002-061||ZANDZ Threaded coupling||3|
|6.||ZZ-004-060||ZANDZ Guide head for jackhammer attachment||1|
|7.||ZZ-006-000||ZANDZ Conductive grease||1|
|8.||ZZ-007-030||ZANDZ Waterproofing tape||1|
|9.||ZZ-008-000||ZANDZ Attachment to the hammer (SDS max)||1|
|10.||GL-11075-10||GALMAR Copper-plated strip (30 x 4 mm/S 120 mm²; 10-meter strip bundle)||1|
Do you have any questions about the lightning protection of the crude oil custody transfer metering system or other facilities? Please, contact the ZANDZ Technical Center!