Electrical Flying Leads and Connectors

3.3.9. Electrical Flying Leads and Connectors

The EFL connects the EDU to the SCM on the tree. Each SCM utilizes two independent EFLs from the EDU for the redundant power on communi- cation circuits, as shown in Figure 3-11.

3.3.9.1. Manufacturing

The EFL assembly is composed of one pair of electrical wires enclosed in a thermoplastic hose, fitted at both ends with soldered electrical connectors. The assembly constitutes an oil–filled, pressure-compensated enclosure for all wires and their connections to ROV-mateable connectors.

3.3.9.2. Construction

Wires are continuous and are, at a minimum, of 16 AWG. A twisted-pair configuration is recommended. Voltage and current ratings for the wires are sized to not significantly degrade overall circuit performance based on the results from the electrical analysis. Wires are soldered to the connector pins and protected by boot seals of compatible material. Pin assignment matches the system requirements. A hose with low collapse resistance, specifically selected for subsea use, with titanium or equivalent end fittings, connects both electrical connectors of the flying lead, to ensure compatibility of materials used. The length of the wire within the hose is sized to allow for any stretching of the hose up to failure of the hose or the end fittings. Hose stretching does not allow for any pull load on the soldered connections. Hoses are a continuous length with no splices or fittings for lengths under 300 ft (91m). Any use of splices or fittings is brought forward for approval on a case-by-case basis. Hoses are filled with Dow Corning –200 dielectric fluids. The compatibility of the hoses, boot seals, and wire insulation with the compensating fluid and seawater is confirmed. The wire insulation is a single-pass extrusion and suitable for direct exposure to seawater. All wires are100 % tested for voids and pinholes by immersion in water hipot. Connectors are marked appropriately to simplify ROV operations. An alignment key or other device is incorporated to ensure correct orientation. The electrical connectors must be qualified for the duty and be capable of making and breaking at worst case angles, before and after course alignment, without failure. They must be capable of making and breaking 100 times under power on the female pin half without any sign of damage to pins or sockets and still remain capable of excluding seawater.

3.3.9.3. Installation

Connectors are provided with shipping protection covers. All assemblies are identified with tags on both ends of the EFL. Tags must be designed such that they do not come off under severe handling onshore, offshore, and during installation and must be visible to ROVs at working water depth. The color of the hose is visible to ROVs when in subsea use. Such colors include yellow or orange. In order to be easily visualized and identified by ROV in underwater situations, the ROV handles and the bottom plastics sleeves of flying leads should be painted with colorful marks according to standards and codes. These marks should be identified throughout the life time of the system. All EFL assemblies are filled with compensating fluid to a slight positive pressure (10 psi) prior to deployment. Flying leads installed subsea are protected with mating connectors when not in use. These EFLs are temporarily located on parking positions on the E-UTA assembly, at the tree, or on a parking stand installed for that purpose.

3.3.9.4. Electrical Connectors

Electrical connectors have the following basic requirements: • An electrical connector is a termination for electrical cables used to transmit electrical power of low voltage and communication signals between subsea production control system components.

• Electrical connectors at the very minimum meet all requirements as stated in the latest revision of ISO 13628-4 [4] and ISO 13628-6 [3].
• The number of electrical connectors in series is kept to a minimum.
Redundant routing follows different paths. Consideration should be given to keeping voltage levels as low as practical in order to minimize electrical stresses on conductive connectors.
• Connectors are either Tronic or ODI.
• The electrical connector is capable of making wet mateable electrical connections utilizing an ROV. They are designed and constructed for normal and incidental loads imparted by ROVs during make-or-break operations.
• It is important to confirm the type of connector halves – whether it is “cable end” type or “bulkhead connector” type.
• The Christmas tree side has male (pin) connectors and the flying leads have female (socket) connectors.
• Connectors are configured to ensure that no male pins are powered up while exposed. Electrical distribution systems should be designed such that “live disconnect” is not required during normal mainte- nance or if possible during failure mode operation or recovery periods.
• Connectors are furnished with the necessary equipment to protect it from being unmated while in-service and to prevent calcareous buildup and marine growth.
• Optical connectors for any fiber-optic lines are fitted with long-term protective caps.