The months of August and September already tend to be busy times for bell pepper grower Hans van der Waal from H. van der Waal nursery. On 8.3 hectares he cultivates yellow and red peppers, which he supplies to ZON. This year came with an extra challenge, however. The trusses and roof of his tank needed emergency repair. And, according to all involved, that was not an easy task.

Hans explains: "At the beginning of March we found a nitrogen leak in the top of the tank that serves as an expansion tank." A look at the roof, however, indicated that something else was going on. The roof had collapsed. A call was made to Calor Holland, which deals with the design, installation and maintenance of greenhouse heating installations. They soon saw that the damage was caused by an implosion of the tank. "Probably something went wrong with a safety mechanism. Due to pressure differences after a certain water shift, a vacuum was created that bent the rafters."

Difficult access
SJR Greenhouse Tanks was brought in as a third party to assist with the repairs. Like Calor it's also a relatively young company, and since 2017 part of the SJR Group (formerly known as Sloot Tankbouw). This company specializes in the construction of heat storage tanks around the world since 1961. "This was not an everyday task for us", says André Stougje. "That was mainly because the tank was wedged in between the greenhouses and a shed. The only access was a door of 90 cm by two meters. Too narrow for a crane."

Some creative problem solving was required. The roof of the barn had to be opened up for the crane. "There still remained a lot of manual work, because the largest crane we could fit there hung 1.5 meters above the tank."

Temporary heating installation
During the repairs, normal work inside the greenhouses had to continue uninterrupted. This meant that the boiler installation had to be kept warm. "We installed a temporary expansion installation. After the repairs the tank was refilled and the temporary installation disconnected," explained Jean-Pierre Schenkeveld from Calor.

Happy grower
The repairs were finished in nine weeks, and Hans is delighted with the result. With the new roof and the new rafters, his 18-year-old tank is safe to use again. "It was a challenging project for us all. I am very pleased with the intensive cooperation and the good communication on the work floor," the content grower concluded.

For more information:


Hans van der Waal
Kwekerij H. van der Waal

Noordelijke Dwarsweg 61
2761 GD Zevenhuizen
T: +31 (0)6 24 504 481

André Stougje
SJR Greenhouse Tanks

Gieterijweg 31
3089 JZ Rotterdam
T: +31 (0)10 - 248 35 00

Jean-Pierre Schenkeveld
Calor Holland B.V.
Nijverheidsweg 20P
2821AW Stolwijk
+31 182 604 871