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The range of process applications to which SFC interlocks can be applied is unlimited. As clients begin to understand the immense operational capabilities of SFC interlock systems, they often request unique solutions to specific problems.
In this section we present some examples of
'specials' we have developed to meet clients'
specific operating safety requirements.
SFC are always pleased to receive a challenge to provide unique solutions to clients' individual or special problems. |
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| To convert remote valve operation (motorised valves) to local operation, and still retain the integrity and safety of the operating sequence. |
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For this problem, our solution was to design and manufacture a solenoid key release device. As a consequence of the working environment, a hazardous area enclosure to Eexd llb T6 was also required The basic 'QL' lock body was fitted to the operating lever (knob) of the switch. BASEEFA certification for this adaptation was approved.
A remote signal from the control room activates the local solenoid which releases the key. The key is used to operate other valve control equipment in the system. A proximity sensor fitted to the switch lock provides evidence back to the control room that operational activity is underway. |
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| To interlock a single acting, pneumatic actuator on a ball valve. |
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Where single acting, spring return pneumatically actuated valves have to be incorporated into an interlock sequence, an interlocked 3-way isolating valve is a simple and effective solution. The isolating valve is located upstream of the actuator control panel. When operating the isolating valve, air pressure
to the actuator is vented to atmosphere, thus completely disabling the valve which will then operate automatically to it’s designed fail-safe position.
Single or double key arrangements can be used to isolate the valve in any position. In the illustration the interlock incorporates a chassis plate for local wall mounting, and a proximity sensor for status indication back to a control room. This arrangement is a cost effective addon control feature to all types of pneumatic, hydraulic or gas actuators. |
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| Resrictions of space require that a modular style double block and bleed valve is used in place of a conventional 3 valve piped arrangement. It is required that the modular valve is interlocked with other valves in the system. |
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Modular valves of this type pose greater problems for interlocking by virtue of their size and space limitations. SFC designed a bespoke cam type interlock especially for this host valve.
Used on the Brent Delta platform, this interlock provided the perfect solution for our customer's problem. |
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| To mechanically interlock an electrically operated device, within a hazardous environment. |
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Where mechanical (interlocked) control of powered equipment is required in a hazardous area, the SFC switch lock provides the perfect solution. In this illustration our 'QL' quarter turn interlock is fitted to the actuator lever of an Eexd lIb T6 hazardous area control switch.
A single or dual key configuration can be supplied to lock in the 'ON', 'OFF' or both positions. Switches of all zone protection specifications can be provided. |
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| To ensure two ports on an instrument manifold can never be simultaneously opened. |
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Needle valves of all types can be fitted with SFC interlocks. Regardless of body design, number of operating handles or method of operation, SFC can supply a solution to your problem. In this illustration a 4-port instrument manifold is equipped with SFC's NVL interlock. The locking device ensures that pairs of operating handles can only be operated one at a time. Upon opening the first port, the key becomes trapped. The second port cannot be opened until such time that the first port has been closed, thus releasing the operating key.
The opposite pair of ports are controlled in the same way with a differently coded key. |
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| To permit complex variations in operating sequences on launcher/receiver systems. |
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The simplest interlock systems will normally feature a 'linear sequence'. This is where the outward 'journey' (operating steps) are mirrored by the return journey. However, from time to time non-linear
sequences are necessary. A typical example of a non-linear sequence is a pig receiving procedure where double block and bleed valves control complex nitrogen purging, pressure equalisation, venting
and draining.
The sequence control unit is a mechanical key issuing/control device. It is normally placed locally to the valve system. It differs from a key exchange unit in that, upon inserting a permit key, a selector
knob is rotated to a fixed position before the next key is issued. |
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| To interlock a double acting, pneumatic actuator on a ball valve. |
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For this requirement SFC adapted their QLA interlock to incorporate a sliding control lever with forward and backwards motion.
This linear motion interfaced with the pneumatic valve operating lever to provide double acting operation. |
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