Lightning Protection for a Crude Oil Custody Transfer Metering System (COCTMS)

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.

Lightning Protection for a Crude Oil Custody Transfer Metering System (COCTMS)

Initial data:

  1. Facility: a crude oil custody transfer metering system.
  2. Architectural drawings.
  3. 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:

Calculation of a vertical arrangement

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;

Ground electrode deepening

Horizontal electrode resistance:

Calculation of a horizontal arrangement

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:

Calculation of impedance of a grounding arrangement


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.

Lightning protection for a crude oil custody transfer metering system (COCTMS)

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
Grounding arrangement:
2. ZZ-005-064

ZANDZ Conductor connection clamp

(up to 40 mm)

3. ZZ-001-065 ZANDZ Copper-plated threaded grounding rod (D14; 1,5 m) 4
4. ZZ-002-061 ZANDZ Threaded coupling 3
5. ZZ-003-061 ZANDZ Termination 2
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!

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