This document is a Quick Fix Guide for Netherlocks Process Interlocking valve interlocks, designed to help users understand, operate, and troubleshoot these safety systems.
Function Description
Netherlocks valve interlocks are safety systems designed to enforce a predefined valve operating sequence, create a safer working environment, save costs, and prevent production spills or losses due to incorrect switchovers. They guide operators safely through strict work procedures. These interlocks are permanently mounted to the valve and guide the operator through a predefined sequence using unique keys for each step.
Some common applications for valve interlocks include:
- Pressure Safety Valves: To guarantee that only one relief valve can be offline/in maintenance at any given time.
- Pig launching and receiving: To guarantee the closure door can only be opened when the vessel is depressurized, free from toxic gases, and isolated.
- Decoking: To guarantee a safe changeover from cracking to de-coking of the furnace.
- Inert gas systems: To prevent that inlet and outlet of a tank are closed at the same time.
- Pump startup: To guarantee that during startup, the suction valve is open.
- Flare lines: To guarantee that there is always an open path to the flare.
- Boiler blow-down: To prevent that the drain and vent are opened at the same time.
- 2 out of 3: To guarantee that always two out of three instruments (e.g., pressure gauge, level gauge) are online.
- Chemical dosing: To guarantee that the pot is isolated before filling.
- Amine absorber: To guarantee that the drain can only be opened when the vessel is isolated.
The basic principle of valve interlocking involves a key cabinet and two locks (Lock A and Lock B). A "Green start key" is taken from the key cabinet to operate Lock A. Once Lock A is operable, a "Yellow switch key" is transferred from Lock A to Lock B. After Lock B is operated, a "Red end key" is returned from Lock B to the key cabinet. This sequential key transfer ensures proper operation.
Important Technical Specifications
The document details two main types of valve interlocks: NDL (Ninety Degree Lock) for lever-operated valves and MRL (Multi Rotation Lock) for handwheel and gearbox-operated valves.
NDL (Ninety Degree Lock) Components:
- AISI 431 sliding lever for optimum flexibility.
- AISI 316 body.
- AISI 316 Adaptor - purpose machined - with 4 keyways.
- Linear key for operator friendly use.
- Key slots protected with self-sealing weather strips.
- Mounting plate to connect bracket to interlock.
- AISI 316 bracket - purpose machined.
- Fixing means.
NDL Dimensions (without bracket and adaptor):
- Length (mm): 133
- Width (mm): 115
- Height (mm): 107
- Mass of lock (kg)*: 2.9
- Lever sizes (mm): Different lever sizes from 230 to 730
MRL (Multi Rotation Lock) Components:
- CS powder coated hand wheel / optional AISI 316.
- AISI 316 body.
- Original nut will be used if possible.
- AISI 316 Adaptor - purpose machined - with 4 keyways.
- Easy to set and reset counters behind counter cover plate.
- Linear key.
- Key slots protected with self-sealing weather strips.
- Mounting plate to connect bracket to interlock.
- AISI 316 bracket - purpose machined.
MRL-S (Small type) Dimensions (without bracket, adaptor and hand wheel):
- Length (mm): 133
- Width (mm): 115
- Height (mm): 82
- Mass of lock (kg)*: 3
- Handwheel sizes: Different sizes between 200 and 700
- Max. valve spindle diameter (mm): 26
MRL-L (Large type) Dimensions (without bracket, adaptor and hand wheel):
- Length (mm): 152
- Width (mm): 144
- Height (mm): 100
- Mass of lock (kg)*: 4.7
- Handwheel sizes: Different sizes between 380 and 700
- Max. valve spindle diameter (mm): 68
Interlock Tag Plates:
These plates are permanently fitted to the locking device and include:
- Key code open key
- Key code close key
- System tag number
- Serial number (netherlocks-year.serialnumber)
Key Tag Plates:
These indicate the situation of the valve:
- Green tag: 'standard or preferred' situation (e.g., PSV B IN OPERATION, PSV A IN SPARE)
- Red tag: 'in maintenance' or 'non-standard' situation (e.g., PSV A IN OPERATION, PSV B IN MAINTENANCE)
- Yellow tag: 'switching in progress' (e.g., SWITCH KEY, PSV A, PSV B)
Netherlocks recommends using red, yellow, and green tags according to the 'traffic light principle'.
Key Cabinet Tag Plates:
Tagging in a key cabinet is only visible when keys are out, indicating that the system is being operated. Tag plate texts and colors are specified by the customer.
Usage Features
The guide provides clear instructions on how to operate and reset valve interlocks.
How to operate valve interlocks:
- Make sure the code on the key is the same as the code on the lock.
- To enter the key correctly, see the engraving on the side of the lock body for correct positioning.
- Fully insert the key in the key slot.
- Fully operate the valve.
- Remove the other key (if applicable, single locking devices only have 1 key for open or closed).
How to reset an MRL valve interlock:
Resetting is required when the end stops of a valve change due to wear or pollution inside the valve.
- On both sides of the MRL lock, there are slotted holes where the counting mechanism of the lock can be set for any valve or gearbox up to 180 turns.
- Above 180 turns, a special valve interlock (x-counter) has to be installed, which can handle 800 turns by default.
- For more than 800 turns, a customized version of the x-counter is available.
Reset Procedure (Open Side):
- Ensure the key is fully inserted and leave it in.
- Confirm both keys are entered.
- Remove the counter cover on the open side (right).
- Slowly turn the valve back towards its closed position until both set screws are visible (on the open side).
- If only one or no set screw appears, contact Netherlocks or your local interlock partner.
- Untighten both set screws.
- Fully open the valve.
- Tighten both set screws.
- Re-install the counter cover.
- Remove the open key; the valve is locked open.
- Note: To set the MRL, the valve must be fully operable. An allen key M3 and a T30 Resistorx key are needed to reset.
Reset Procedure (Close Side):
- Ensure the key is fully inserted and leave it in.
- Confirm both keys are entered.
- Remove the counter cover on the close side (left).
- Slowly turn the valve back towards its open position until both set screws are visible (on the closed side).
- If only one or no set screw appears, contact Netherlocks or your local interlock partner.
- Untighten both set screws.
- Fully close the valve.
- Tighten both set screws.
- Re-install the counter cover.
- Remove the close key; the valve is locked closed.
Q-cards - Commissioning keys:
Q-cards allow free operation of an interlock for commissioning and installation purposes. They are dedicated commissioning keys inserted in an interlock during production. They are specifically designed for one-time use to avoid abuse of Q-cards after removal. No need for master keys or spare keys during installation and testing, as these could jeopardize plant safety later.
How to remove a Q-card:
- Fully close the valve.
- Remove the temporary plastic cover on the close side.
- Ensure set screws are aligned and flush.
- Tighten grub screws.
- Now remove the Q-Card.
- Insert the correct operating key (cross-checking lock tag and code on key).
- Place counter cover.
- Fully open valve.
- Repeat steps 2 to 7 for the open side of the lock.
Troubleshooting Valve Interlocks:
- Key stuck (key cannot be removed):
- Check if you are considering removing the correct key (valve open, then right key should be removed; valve closed, then left key should be removed).
- Check if the valve is fully operated; the key is only removed when the valve is fully open or closed.
- Check setting; remove the setting counter cover from the side where the key is stuck.
- If two set screws are not inline, flush, and directly visible, the lock has passed or not reached its setting and needs to be reset (see reset procedure).
- After reset, remove the key.
- Key does not fit (key cannot be inserted):
- Check if the key is being inserted in the right orientation (not upside down); see key engraving on the side of the lock body for correct positioning.
- Check if you have the correct key by comparing the engraved key code with the code of the lock key position.
- Check if anything is blocking the key entrance or if the key is damaged.
- If two set screws are not inline, please contact Netherlocks or your local interlock partner.
- Key lost:
- Use a spare key, master key, or group master key to (temporarily) replace the lost key (a group master key is a master key for only part of the plant).
- Order a replacement key.
- Lookup interlock serial number on the lock tag plate.
- Check key code of missing key.
- Netherlocks keeps track of all lock serial numbers and corresponding key codes. Based on the lock serial number and key code, new keys can be manufactured and shipped.
- Valve is replaced:
- Check if the new host valve is the same type & size as the previous valve (see 'valve interlock components' for an explanation on interlock parts).
- Check whether the topwork dimensions of the valve are the same. Check fill-in sheets on netherlocks.com/support.
- If the valve is the same type and size, the lock body can be re-used.
- If the valve is another type and/or size, contact Netherlocks or your local interlock partner to determine whether the same lock body can be re-used.
- If topwork is equal to the old valve, the bracket and adaptor can be re-used.
- If topwork is not equal to the old valve, order a new mounting set, based on the new topwork dimensions.
- Note: Lever operated valves require an NDL. Handwheel and gearbox operated valves require an MRL. When an interlocked, lever-operated valve gets equipped with a gearbox, a new interlock is required.
Maintenance Features
Netherlocks valve interlocks are manufactured with care and are renowned for their high quality. They do not need greasing, neither do parts have to be replaced.
Netherlocks offers various support programs and service products:
Installed Base Support:
- Single maintenance programs: Maximize interlock components and system lifetime, increase process uptime, minimize last-minute repairs, ensure compliance with company and/or regulatory safety rules, and ensure efficient execution of maintenance. Output: report including system status and repair advice.
- Survey: Visual inspection of locks and cabinets (general condition, missing locks/keys, damage, tagging). Every 1-3 years depending on criticality of the system.
- Functional check: Visual inspection of locks and cabinets (see Survey). Functionality test of locks and sequences (includes resetting of locks if necessary). Every 1-3 years depending on criticality of the system.
- Internal inspection: Removal and opening of locks, inspection and cleaning of lock internals (when locks are exposed for a period of time to severe climates or fouling environments). Every 5-10 years depending on the environment (normally only 10-20% of the locks are done in order to assess the overall health condition of the system).
- Emergency call out and standby contracts: Securing response times for on-site interventions.
- Multi-year agreements: Combination of different maintenance programs (intervals adjustable to requirements) and/or fixed response times for emergencies. Extra advantages: keep system up to date at all times, full after-care.
- Troubleshooting: Resolving technical issues and repairing locks, assuring the best possible solution.
Project Support:
- Measurement and installation: Collection of valve topwork details, designing the right solution for an up-to-date system, installation of new locks.
- Installation and commissioning: Installation of locks at the customer's production site, setting and ensuring the sequence is according to the agreed specifications and functionality. A Netherlocks commissioning report per system is issued.
- Supervision: A Netherlocks service engineer will work with the customers installation team to ensure installation and commissioning at the highest quality levels. A Netherlocks commissioning report per system is issued.
Knowledge Support:
Several training programs are offered at an on-site location or at the Netherlocks facilities in the Netherlands.
- Training program end-user:
- Maintenance training: Learn about basic interlock functionality, installation, setting, and troubleshooting.
- Operations training: Learn about interlock functionality, operation skills (sequences, key operation, etc.), and setting.
- Training program contractor - Installation: Learn about basic interlock functionality, installation, and setting.
- Advanced training program for agents and certified service partners.
For support, users can contact support@netherlocks.com or call +31 (0)172 471 339. Additional resources include instruction videos on youtube.com/netherlocksproducts and interlock sequence information on netherlocks.com/sequence-book.
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