Grimsby Fish Dock Enterprises Ltd operate the fish docks and market in Grimsby. In order to keep the fish fresh they produce ice on site using a Ziegra ice making machine. The ice is used within the market itself, on outgoing boats and is also sold to local businesses on an ad hoc basis.

In 2007 Grimsby Fish Dock Enterprises approached ETCIC to conduct an investigation into the efficiency of their ice making equipment and assess if it could be operated any more effectively...

The ice making process comprises of five chiller units feeding a central silo. The ice is stored in the silo and is then transported out using an auger which feeds onto conveyors for loading the ice either into skips or out through the building to load vessels.

The ice storage silo has a capacity of 30 tonnes but at present Grimsby Fish Dock Enterprises can only have it running with 20 tonnes stored in it. If this weight is exceeded then the ice begins to compress and compact. This causes it to jam and sit above the auger, preventing any ice from being transported out of the silo. When this happens the ice blockage needs to be broken down manually which can be a very time consuming process as employees are required to dig down to the compacted ice and then break up the larger blocks of ice.

The ice is able to block the auger when it is compacted as the aperture to the auger is quite small.

When the silo reaches the point where it contains 20 tonnes of ice, the ice making equipment is switched off to prevent overfilling. When ice levels begin to reduce then the equipment is started up again. The operators try to run the equipment so that there is always a stockpile of available ice. If the silo is completely emptied it is estimated that it takes 24 hours to produce a further 20 tonnes of ice.

As the chiller is located in a cold-room, Grimsby Fish Dock Enterprises have the ability to store some ice outside of the silo. They are able to store approximately 100 skips, each holding about 0.33 tonnes of ice. Therefore they are able to store 33 tonnes of ice in addition to the 20 tonnes held in the silo. However if left for more than 24 hours the ice begins to melt and compact and will eventually become unfit for purpose.

Grimsby Fish Dock Enterprises prefer to have 24 hours notice of the ice requirements of boats. This allows them to try and ensure there is sufficient ice for both the market and the boats. However there are some instances where they are not given the 24 hours notice and this has led to shortfalls in ice production.

The conveyor and rollers which feed the ice outside to awaiting boats can become jammed quite regularly, particularly in summer when the ice begins to melt and compact and therefore becomes denser and heavier. The contact area between the rollers and the conveyor belt are smooth, there are no teeth or notches to aid the purchase of the belt against the roller. Therefore the rollers slide against the conveyor belt and are unable to move it, causing problems with vessel filling and also causing a back-up of ice on the conveyor which can in turn lead to the auger becoming jammed.

The market itself can require up to 60 to 70 tonnes of ice per week at its peak. In the period from 01/10/06 to 30/09/07 the chiller unit produced 2504 tonnes of ice. This equates to 48.15 tonnes per week or 6.86 tonnes per day.

Other Issues

As the Grimsby Fish Docks are located in a hard water area there are regular problems with the water filtration system as filters become blocked. Regular maintenance is required and on average the refrigeration maintenance company have to be called in at least once every two weeks. Grimsby Fish Dock Enterprises have implemented a weekly maintenance check with the aim of identifying any problem issues and rectifying them before it becomes a breakdown issue. The check is carried out by employees and checks for water pressure, oil leaks on gearboxes, leaks from water seals and ensures there are no trip lights illuminated on the control panel.

The water level feeding the ice making machine is also believed to be a problem factor. Water coming onto the site is fed into a water header tank. From there it is drawn off to various areas throughout the market and to the chiller unit. It is felt that if the market itself is consuming a lot of water for cleaning activities etc then it is at detriment to the ice making process, and therefore affects ice production efficiency.

Recommendations

Where possible the ice silo should be kept as empty as possible to reduce the affect of the weight compacting the ice and causing blockages above the auger. It is however recognised that this has to be balanced with the demand for ice and that on some occasions a large volume of ice will be required to be stockpiled to meet demand. Where it can be done, the ice should be transported by conveyor directly into the skips, to await use. Rather than producing a 20 tonne load of ice and then filling the skips, which may lead to blocking of the auger. If all the skips are filled then the silo can begin to be filled if demand requires. By producing the ice this way it should mean that there are fewer blockages, and also if there does happen to be a blockage, at least some ice is available until the blockage is cleared.

Grimsby Fish Dock Enterprises may wish to implement a formal system whereby any vessels requiring ice must give at least 24 hours notice, to ensure that enough ice is produced and that demand is met.

As ice is supplied on an ad hoc basis to local companies such as abattoirs and food processors, it would be beneficial to approach these businesses with a view to formalising their ice requirements in the future. If an understanding of their process requirements and periods of demand can be gained then it would help Grimsby Fish Dock Enterprises to better balance their ice production.

If more in depth data on ice production requirements such as weekly demand for the previous year can be provided, then further recommendations on the optimum amount of ice to be stored at any one time can be made.

The recommendations above will only assist Grimsby Fish Dock Enterprises with balancing ice production demands with the restraints placed upon them by the current maximum weight of 20 tonnes that they are able to hold in the silo. There may on occasions still be issues with production not meeting demand at peak times.

In order for the company to be able to increase their storage capacity for ice, alterations to the silo and conveyor system will be required. The size of the aperture leading to the auger in the silo is at present quite small, leading to bridging of ice above it which prevents it from flowing into the auger and in turn being transported out. By increasing the size of the aperture, the distance that ice would need to bridge would be increased, therefore making it less likely to occur and thus reducing the number of blockages. The angle of the slope feeding into the aperture should also be reviewed to ensure it promotes the best flow of ice into the auger.

Another possible method to overcome blockages of ice would be to retrofit to the equipment a system whereby hot water can be introduced to the area where the blockages are occurring. This would enable the blockages to be melted and allow the less compacted ice above to flow into the auger.

The conveyors which transport the ice from the auger to the skips and / or vessels should be upgraded to have rollers and belts with teeth and notches, allowing improved contact between them and thus preventing the belts slipping, causing the build up of ice.